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Project Title:  Neurogenesis and cognition in human apoE transgenic mice following 56Fe radiation Reduce
Fiscal Year: FY 2009 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 09/01/2005  
End Date: 08/31/2009  
Task Last Updated: 11/22/2009 
Download report in PDF pdf
Principal Investigator/Affiliation:   Raber, Jacob  Ph.D. / Oregon Health & Science University 
Address:  Behavioral Neuroscience and Neurology 
L470, 3181 SW Sam Jackson Park Road 
Portland , OR 97239-3011  
Email: raberj@ohsu.edu  
Phone: 503-494-1524  
Congressional District:
Web:  
Organization Type: UNIVERSITY 
Organization Name: Oregon Health & Science University 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Fike, John  UCSF 
Key Personnel Changes / Previous PI: 0
Project Information: Grant/Contract No. NNJ05HE63G 
Responsible Center: NASA JSC 
Grant Monitor: Cucinott1a, Francis  
Center Contact: 281-483-0968 
noaccess@nasa.gov 
Solicitation / Funding Source: 2004 Radiation Biology NNH04ZUU005N 
Grant/Contract No.: NNJ05HE63G 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) CNS:Risk of Acute (In-flight) and Late Central Nervous System Effects from Radiation Exposure (IRP Rev G)
Human Research Program Gaps: (1) CNS01:What are significant adverse changes in CNS performance in the context and time scale of space flight operations? How is significance defined, and which neuropsychological domains are affected? Is there a significant probability that space radiation exposure would result in adverse changes? What are the pathways and mechanisms of change? (IRP Rev F)
Flight Assignment/Project Notes: NOTE: End date changed back to 8/31/2009 per S. Krenek/JSC (8/07)

End date changed to 9/30/2009 per JSC update info (10/06)

Task Description: Of the major human isoforms of apolipoprotein E (E), E4 is associated with age-related cognitive decline and increased risk to develop Alzheimer’s disease (AD). The space radiation environment contains 56Fe. 56Fe radiation exposure causes cognitive injury and might predispose E4 subjects to cognitive injury and an earlier onset or more severe extent of AD. The pathogenesis of this injury may involve loss or injury to neural precursor cells in the dentate subgranular zone (SGZ) of the hippocampus, which is involved in complex learning requiring the ability to learn about multiple relationships among stimuli. Disturbances in hippocampal functioning reduce spatial learning and memory. The granule cells of the dentate gyrus are involved in spatial memory and their radiation-induced depletion implicated in cognitive deficits. Our data show reduced numbers of proliferating cells and immature neurons and spatial learning and memory impairments in wild type mice x-irradiated at 2 months and behaviorally tested 3 months later. Treatments that damage neuronal precursor cells or their progeny might reduce neurogenesis and impair hippocampus-dependent cognitive functions in an E isoform-dependent fashion. Our data indicate that neuronal expression of E3 protects immature neurons against radiation injury and that E3 is more potent than E4 in supporting neuronal proliferation. After irradiation, SGZ precursor cells undergo rapid apoptotic cell death, which might involve oxidative stress. Oxidative stress might also play a critical role in later reductions in hippocampal neurogenesis. E isoforms differ in their ability to protect against neurotoxicity and apoptosis and oxidative stress. Isoform-specific effects of E on 56Fe radiation-induced oxidative stress, apoptosis, and loss of proliferating SGZ cells rapidly after 56Fe-irradiation or oxidative stress later after irradiation might contribute to their effects on cognitive injury later in life. We hypothesize that human E isoforms are associated with different levels of 56Fe-induced loss of neural precursor cells and hippocampus-dependent cognitive injury, and that these effects can be ameliorated by antioxidants. The Specific Aims are: 1A. Determine if E isoform is associated with radiation-induced apoptosis of neural precursor cells in the dentate SGZ; 1B. Determine the role of E isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ. Mice will be tested 3 months following radiation; 1C. Determine how E isoform affects neurogenesis following 56Fe- irradiation, and determine if this effect is related to the severity of radiation-induced cognitive deficits; 2A. Determine if the presence of a specific E isoform is associated with markers of oxidative stress following radiation injury; and 2B. Determine if the antioxidant a-lipoic acid enhances cognitive function and reduces radiation-induced cognitive impairments and whether this ability is E isoform-dependent. Mice will be irradiated with 56Fe ions (0 to 3 Gy). We will assess cognitive impairments using behavioral tests that require hippocampal functioning and quantify of radiation-induced changes using immunohistochemistry.

Research Impact/Earth Benefits: Our research impacts life on earth as it determines whether genetic risk factors for age-related cognitive decline are also risk factors for radiation-induced cognitive impairments. As we show that the anti-oxidant dietary supplement alpha-lipoic acid is able to antagonize these impairments, the impact constitutes a potential intervention against these challenges.

Task Progress & Bibliography Information FY2009 
Task Progress: In the brain, apoE has been implicated in development, regeneration, neurite outgrowth, and neuroprotection. ApoE plays an important role in tissue repair following brain injury. Our data show that apoE isoform critically modulates the pattern of cognitive changes in the water maze in female mice three months following 56Fe irradiation but in a pattern opposite to that found three months following 137Cs irradiation. ApoE4 female mice are more susceptible than apoE2 female mice to develop cognitive injury 3 months following 137Cs irradiation, similar to the enhanced risk in apoE4 than apoE2 carriers to develop age-related cognitive injury and Alzheimer’s disease (AD). However, 3 months following 56Fe irradiation, apoE2 female mice show radiation-induced cognitive injury while apoE4 female mice show enhanced cognitive performance. This enhanced cognitive performance 3 months following 56Fe irradiation is highly reproducible and seen in apoE4 female mice irradiated at 2 or 6 months of age and cognitive tested 3 months later. This enhanced cognitive performance is not restricted to apoE4 female mice and also seen in apoE3 female mice. In addition, we demonstrated that there is no simple relationship between reduced neurogenesis following irradiation and cognitive function. In contrast to the apoE isoform-dependent effects of 56Fe irradiation on cognitive function, the number of doublecortin-positive immature neurons in the dentate gyrus is dramatically and similarly reduced following 56Fe irradiation in all three genotypes (p < 0.001). Thus, there is no simple relationship between neurogenesis and cognitive function and other mechanisms contribute to the differential cognitive outcomes in the context of a particular apoE isoform. These novel and exciting data have radically changed our understanding of the effects of space irradiation on cognitive function.

In the last year of the grant, we performed work pertinent to Aim 1B: Determine the role of apoE isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ; 1C: Determine how apoE isoform affects neurogenesis following 56Fe- irradiation, and determine if this effect is related to the severity of radiation-induced cognitive deficits; and 2B: Determine if the antioxidant a-lipoic acid enhances cognitive function and reduces radiation-induced cognitive impairments and whether this ability is apoE isoform- dependent. Specifically, we started to test the hypothesis that differences in the levels of reactive oxygen species (ROS) prior and following irradiation contribute to these paradoxical effects. We generated data consistent with such a novel mechanism. As it turned out, these data are not only pertinent to our understanding of the effects of space irradiation on cognitive function in human apoE targeted replacement mice but also to our understanding of the effects of 56Fe irradiation in wild-type mice and the effects of 137Cs irradiation on cognitive performance in wild-type mice.

The hypothesized mechanism is based on the dual role of ROS in learning and memory and the increase in ROS levels following irradiation. While ROS is critical for normal synaptic function and learning and memory, chronic highly elevated ROS levels are pathological. Important in the context of different apoE isoforms, apoE2 is more effective as antioxidant than apoE3 or apoE4. The higher ROS levels in apoE3 and apoE4 than apoE2 female mice prior to irradiation might provide a preconditioning challenge to the apoE3 and apoE4 mice and therefore enhance cognitive function in apoE3 and apoE4, but not apoE2, mice. This might not be limited to human apoE mice and 56Fe irradiation. When we behaviorally tested wild-type mice and mice deficient in the extracellular form of superoxide dismutase (EC-SOD) which show elevated levels of oxidative stress following 137Cs irradiation or sham irradiation, irradiation impaired cognitive function in wild-type while it enhanced hippocampus-dependent cognitive function in distinct cognitive tasks. Although the levels of oxidative stress were higher prior to irradiation in the mice deficient in EC-SOD than wild-type mice, irradiation increased oxidative stress levels only in wild-type mice. In EC-SOD deficient mice, the levels of oxidative stress did not increase following irradiation. We hypothesize that like the EC-SOD deficient mice, apoE4 female mice have higher levels of oxidative stress prior to irradiation and, as a result of altered oxidative stress levels prior and following 56Fe irradiation, show enhanced cognitive performance 3 months following irradiation. We also hypothesize that this enhanced cognitive performance is time-dependent and not seen following prolonged increased levels of ROS in middle aged mice, who show enhanced ROS levels as part of the aging process. Indeed, apoE3 female mice irradiated with 56Fe at 2 months of age and cognitive tested 10 months later did show impairments in spatial memory retention in the water maze.

To determine the role of ROS in cognitive performance following 56Fe irradiation, 9 month-old apoE2 and apoE4 female mice were irradiated with 56Fe or sham-irradiated and either fed a regular diet or a diet containing the anti-oxidant a-lipoic acid (ALA) and cognitively tested 3 months later. At 12 months of age, there was no longer a genotype difference in spatial memory retention in the water maze in the different experimental groups. Therefore, the two genotypes were combined for analysis. Strikingly, while sham-irradiated mice that received ALA-containing food showed worse spatial memory retention than sham-irradiated mice that received the regular diet, the opposite pattern was seen in irradiated mice. Irradiated mice that received the ALA-containing food showed better spatial memory retention than irradiated mice that received the regular diet. To determine whether this effect was restricted to human apoE female mice, we repeated this experiment with wild-type female mice. Consistent with the data in human apoE female mice and the EC-SOD data described above, irradiated wild-type female mice that received the ALA-containing diet outperformed irradiated wild-type mice that received the regular diet but this effect was not seen in sham-irradiated mice. Consistent with this mechanism, we find the same effect in wild-type male mice sham-irradiated or irradiated with 137Cs and treated with a combination of ramipril and statin or a superoxidase mimetic (Euk compound). The sham-irradiated mice show worse cognitive performance with these treatments than sham-irradiated mice that receive vehicle, while a trend towards a therapeutic effect is seen in irradiated mice.

Based on these data and as a future perspective, we are planning experiments to assess whether the effects of ALA on cognitive performance in irradiated mice are associated with lower ROS levels. Similarly, it will be important to show that in young apoE4 female mice the cognitive enhancing effects are associated with enhanced ROS levels. In addition to assessments of oxidative stress using dihydroethidium and western blot analyses for 3-nitrotyrosine, we are planning to develop an in vitro slice model to study the nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase complex. NADPH might be important for the role of ROS on cognitive performance following irradiation. It is expressed in neurons, both in soma and the synaps. In addition, irradiation of rat brain endothelial cells in vitro leads to increases in ROS production and expression of p22 phox and p4 phox proteins, and NADPH oxidase can produce brief bursts of superoxide upon stimulation. Western blot analyses can be used to assess total protein levels and the slice system allows assessment of the activity of the complex. So this would allow assessing the effects of space irradiation on the complex and to determine if these effects are critically modulated by apoE isoform.

Finally, in the final year of the grant we showed that the dendritic marker microtubule-associated protein 2 (MAP-2) is very sensitive to effects of 56Fe irradiation in an apoE isoform-dependent fashion. To determine whether MAP-2 levels change in an apoE isoform-dependent fashion following 56Fe irradiation, brains of the apoE female mice irradiated at 2 months of age as described above were processed for MAP-2 immunohistochemisry. Group differences were analyzed using a multivariate analysis with genotype and treatment as between subject factors. There was a genotype x treatment interaction (P < 0.05, Roy’s Largest Root Multivariate Analysis). Irradiation reduced MAP-2 levels in apoE3 and apoE4 (p < 0.001), but not apoE2, mice. Expression of MAP-2 is increased in the hippocampus and cortex of aged female and male C56BL/6J wild-type mice. Similarly, we find increased hippocampal MAP-2 levels in the aged female Rhesus monkeys. We hypothesize that this increase might constitute a compensatory change and that therefore the reduced MAP-2 levels in irradiated apoE3 and apoE4 female mice might contribute to pathological aging and reduced MAP-2 levels as seen in late stages of AD. Next we determined whether the reduced MAP-2 levels in irradiated mice are associated with increased levels of the presynaptic marker synaptophysin (SYN). This turns out not to be the case. In aged, but not middle-aged Rhesus monkeys, the levels of SYN are increased. These data indicate that MAP-2 is a particularly suitable and sensitive marker to quantify effects of space irradiation on brain function. Based on the magnitude of the effect, MAP-2 seems also a good candidate to help developing a mathematical framework for risk estimation of age-related changes in brain function following irradiation and as a function of apoE isoform.

Bibliography Type: Description: (Last Updated: 07/23/2021)  Show Cumulative Bibliography Listing
 
Abstracts for Journals and Proceedings Raber J, Villasana L, Pfankuch T. "Effects of 56Fe Radiation on Hippocampal-Dependent Spatial Learning and Memory and Hippocampal Neurogenesis in Mice." 19th Annual NASA Space Radiation Investigators’ Workshop, Philadelphia, Pennsylvania, 2008.

19th Annual NASA Space Radiation Investigators’ Workshop, Philadelphia, Pennsylvania, 2008. , Aug-2008

Abstracts for Journals and Proceedings Villasana L, van Meer P, Pfankuch T, Raber J. "Enhanced Spatial Memory Retention of hApoE4 Female Mice in the Water Maze Following 56Fe Cranial Irradiation." Society for Neuroscience Annual Meeting 2008, Washington, DC, November 2008.

Society for Neuroscience Annual Meeting 2008, Washington, DC, November 2008. , Nov-2008

Abstracts for Journals and Proceedings Benice T, Raber J. "Late-phase trial-dependent spatial memory in mice relies on androgens but not on changes in adult hippocampal neurogenesis." Society for Neuroscience Annual Meeting 2008, Washington, DC, November 2008.

Society for Neuroscience Annual Meeting 2008, Washington, DC, November 2008. , Nov-2008

Abstracts for Journals and Proceedings Villasana L, van Meer P, Pfankuch T, Raber J. "Enhanced spatial memory retention of hApoE4 female mice in the watermaze following 56Fe cranial irradiation." New England Science Symposium 2009, Joseph B Martin Conference Center at Harvard Medical School, Boston MA, May 2009.

New England Science Symposium 2009, Joseph B Martin Conference Center at Harvard Medical School, Boston MA, May 2009. , May-2009

Abstracts for Journals and Proceedings Villasana L, van Meer P, Pfankuch T, Raber J. "Enhanced spatial memory of apoE3 and apoE4 female mice following 56Fe irradiation associated with reduced hippocampal MAP-2 levels." Student Research Forum OHSU 2009, Oregon, May 2009.

Student Research Forum OHSU 2009, Oregon, May 2009. , May-2009

Abstracts for Journals and Proceedings Fike JR, Rosi S, Ferguson R, Fishman K, Obenaus A, Raber J. "Trauma induced alterations in cognition and expression of the behaviorally expressed immediate early gene Arc are reduced by a previous exposure to 56Fe." Heavy Ions in Therapy and Space Symposium, 20th Annual NASA Space Radiation Health Investigators’ Workshop 2009, Cologne, Germany, July 2009.

Heavy Ions in Therapy and Space Symposium, 20th Annual NASA Space Radiation Health Investigators’ Workshop 2009, Cologne, Germany, July 2009. , Jul-2009

Abstracts for Journals and Proceedings Raber J, Villasana L, Fike JR, Pfankuch T. "Paradoxical Apolipoprotein E Isoform-dependent Effects of 56Fe Radiation on Cognitive Function and MAP-2 Immunoreactivity in Mice." Heavy Ions in Therapy and Space Symposium, 20th Annual NASA Space Radiation Health Investigators’ Workshop 2009, Cologne, Germany, July 2009.

Heavy Ions in Therapy and Space Symposium, 20th Annual NASA Space Radiation Health Investigators’ Workshop 2009, Cologne, Germany, July 2009. , Jul-2009

Abstracts for Journals and Proceedings Villasana L, van Meer P, Pfankuch T, Raber J. "Enhanced spatial memory of apoE3 and apoE4 female mice following 56Fe irradiation associated with reduced hippocampal MAP-2 levels." Society for Neuroscience Annual Meeting 2009, Chicago, IL, November 2009.

Society for Neuroscience Annual Meeting 2009, Chicago, IL, November 2009. , Nov-2009

Abstracts for Journals and Proceedings Rosi S, Ferguson RA, Levy W, Fishman K, Raber J, Obenaus A, Fike JR. "Trauma induced alterations in cognition and expression of the behaviorally-induced immediate early gene Arc are reduced by a previous exposure to 56Fe." Society for Neuroscience Annual Meeting 2009, Chicago, IL, November 2009.

Society for Neuroscience Annual Meeting 2009, Chicago, IL, November 2009. , Nov-2009

Abstracts for Journals and Proceedings Raber J. "Potential short- and long-term effects of environmental conditions during space missions on cognitive function." Symposium: Space Radiation Effects. 2009: 55th Annual Meeting Radiation Research Society, Savannah, Georgia, October 3-7, 2009.

55th Annual Meeting Radiation Research Society, Savannah, Georgia, October 3-7, 2009. , Oct-2009

Abstracts for Journals and Proceedings Raber J. "Invited talk: Effects of Cranial Irradiation on Cognition and Neurogenesis in Mice." Medical College of Wisconsin invited talk, 2009.

Medical College of Wisconsin invited talk, January 2009. , Jan-2009

Abstracts for Journals and Proceedings Raber J. "Effects of cranial irradiation on neurogenesis and cognition in mice." 2009: Continuing Education Symposium at Annual Meeting Society of Toxicologic Pathology, Washington, DC, August 2009.

2009: Continuing Education Symposium at Annual Meeting Society of Toxicologic Pathology, Washington, DC, August 2009. , Aug-2009

Articles in Peer-reviewed Journals Benice TS, Raber J. "Castration and training in a spatial task alter the number of immature neurons in the hippocampus of male mice." Brain Res. 2010 May 6;1329:21-9. Epub 2010 Mar 15. PMID: 20233585 , May-2010
Articles in Peer-reviewed Journals Jahn-Eimermacher A, Lasarzik I, Raber J. "Statistical analysis of latency outcomes in behavioral experiments." Behav Brain Res. 2011 Aug 1;221(1):271-5. Epub 2011 Mar 17. http://dx.doi.org/10.1016/j.bbr.2011.03.007 ; PMID: 21397635 , Aug-2011
Articles in Peer-reviewed Journals Siegel JA, Haley GE, Raber J. "Apolipoprotein E isoform-dependent effects on anxiety and cognition in female TR mice." Neurobiol Aging. 2012 Feb;33(2):345-58. Epub 2010 Apr 18. PubMed PMID: 20400205 , Feb-2012
Articles in Peer-reviewed Journals Villasana L, Pfankuch T, Raber J. "Isoform-dependent effects of apoE on doublecortin-positive cells and microtubule-associated protein 2 immunoreactivity following (137)Cs irradiation." Radiation and Environmental Biophysics, 2010 Aug;49(3):421-6. PMID: 20458592 , Aug-2010
Articles in Peer-reviewed Journals Villasana LE, Benice TS, Raber J. "Long-term effects of 56Fe irradiation on spatial memory of mice: role of sex and apolipoprotein E isoform." Int J Radiat Oncol Biol Phys. 2011 Jun 1;80(2):567-73. PubMed PMID: 21549250 , Jun-2011
Articles in Peer-reviewed Journals Haley GE, Villasana L, Dayger C, Davis MJ, Raber J. "Apolipoprotein E genotype-dependent paradoxical short-term effects of (56)fe irradiation on the brain." nternational Journal of Radiation Oncology Biology Physics. 2012 Nov 1;84(3):793-9. Epub 2012 Mar 6. http://dx.doi.org/10.1016/j.ijrobp.2011.12.049 ; PubMed PMID: 22401921 , Nov-2012
Articles in Peer-reviewed Journals Olsen RH, Agam M, Davis MJ, Raber J. "ApoE isoform-dependent deficits in extinction of contextual fear conditioning." Genes Brain Behav. 2012 Oct;11(7):806-12. PubMed PMID: 22883220 , Oct-2012
Articles in Peer-reviewed Journals Yeiser LA, Villasana LE, Raber J. "ApoE isoform modulates effects of cranial (56)Fe irradiation on spatial learning and memory in the water maze." Behavioural Brain Research. 2012 Sep 24;237C:207-214. http://dx.doi.org/10.1016/j.bbr.2012.09.029 ; PubMed PMID: 23018124 , Sep-2012
Articles in Peer-reviewed Journals Villasana LE, Rosenthal RA, Doctrow SR, Pfankuch T, Zuloaga DG, Garfinkel AM, Raber J. "Effects of alpha-lipoic acid on associative and spatial memory of sham-irradiated and (56)Fe-irradiated C57BL/6J male mice." Pharmacology, Biochemistry, and Behavior. 2012 Oct 7;103(3):487-93. http://dx.doi.org/10.1016/j.pbb.2012.09.021 ; PubMed PMID: 23051895 , Oct-2012
Articles in Peer-reviewed Journals Villasana L, Dayger C, Raber J. "Dose- and ApoE isoform-dependent cognitive injury after cranial 56Fe irradiation in female mice." Radiat Res. 2013 Apr;179(4):493-500. http://dx.doi.org/10.1667/RR3210.1 ; PubMed PMID: 23496055 , Apr-2013
Articles in Peer-reviewed Journals Haley GE, Yeiser L, Olsen RH, Davis MJ, Johnson LA, Raber J. "Early effects of whole-body (56)Fe irradiation on hippocampal function in C57BL/6J mice." Radiat Res. 2013 May;179(5):590-6. Epub 2013 Mar 19. http://dx.doi.org/10.1667/RR2946.1 ; PubMed PMID: 23510274 , May-2013
Articles in Peer-reviewed Journals Acevedo SE, McGinnis G, Raber J. "Effects of 137Cs gamma irradiation on cognitive performance and measures of anxiety in Apoe-/- and wild-type female mice." Radiat Res. 2008 Oct;170(4):422-8. PubMed PMID: 19024648 , Oct-2008
Articles in Peer-reviewed Journals Acevedo SF, Tittle S, Raber J. "Transgenic expression of androgen receptors improves spatial memory retention in both sham-irradiated and 137Cs gamma-irradiated female mice " Radiat Res. 2008 Nov;170(5):572-8. PubMed PMID: 18959467 , Nov-2008
Articles in Peer-reviewed Journals Villasana L, Rosenberg J, Raber J. "Sex-dependent effects of 56Fe irradiation on contextual fear conditioning in C57BL/6J mice." Hippocampus. 2010 Jan;20(1):19-23. PubMed PMID: 19489001 , Jan-2010
Articles in Peer-reviewed Journals Raber J, Villasana L, Rosenberg J, Zou Y, Huang TT, Fike JR. "Irradiation enhances hippocampus-dependent cognition in mice deficient in extracellular superoxide dismutase." Hippocampus. 2011 Jan;21(1):72-80. PMID: 20020436 , Jan-2011
Articles in Peer-reviewed Journals Raber J. "Unintended effects of cranial irradiation on cognitive function." Toxicologic Pathology, 2010 Jan;38(1):198-202. PMID: 19880825 http://dx.doi.org/10.1177/0192623309352003 , Jan-2010
Books/Book Chapters Obenaus A, Raber J. "Behavioral and neurophysiological changes with exposure to ionizing radiation." Invited subcontract from AFFRI through the Henry M. Jackson Foundation to revise Chapter 7 in the Military Medicine Consequences of Nuclear Warfare (1989 Revision) textbook., Jan-2010
Project Title:  Neurogenesis and cognition in human apoE transgenic mice following 56Fe radiation Reduce
Fiscal Year: FY 2008 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 09/01/2005  
End Date: 08/31/2009  
Task Last Updated: 06/17/2008 
Download report in PDF pdf
Principal Investigator/Affiliation:   Raber, Jacob  Ph.D. / Oregon Health & Science University 
Address:  Behavioral Neuroscience and Neurology 
L470, 3181 SW Sam Jackson Park Road 
Portland , OR 97239-3011  
Email: raberj@ohsu.edu  
Phone: 503-494-1524  
Congressional District:
Web:  
Organization Type: UNIVERSITY 
Organization Name: Oregon Health & Science University 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Fike, John  UCSF 
Key Personnel Changes / Previous PI: 0
Project Information: Grant/Contract No. NNJ05HE63G 
Responsible Center: NASA JSC 
Grant Monitor: Cucinott1a, Francis  
Center Contact: 281-483-0968 
noaccess@nasa.gov 
Solicitation / Funding Source: 2004 Radiation Biology NNH04ZUU005N 
Grant/Contract No.: NNJ05HE63G 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) CNS:Risk of Acute (In-flight) and Late Central Nervous System Effects from Radiation Exposure (IRP Rev G)
Human Research Program Gaps: (1) CNS01:What are significant adverse changes in CNS performance in the context and time scale of space flight operations? How is significance defined, and which neuropsychological domains are affected? Is there a significant probability that space radiation exposure would result in adverse changes? What are the pathways and mechanisms of change? (IRP Rev F)
Flight Assignment/Project Notes: NOTE: End date changed back to 8/31/2009 per S. Krenek/JSC (8/07)

End date changed to 9/30/2009 per JSC update info (10/06)

Task Description: Of the major human isoforms of apolipoprotein E (E), E4 is associated with age-related cognitive decline and increased risk to develop Alzheimer’s disease (AD). The space radiation environment contains 56Fe. 56Fe radiation exposure causes cognitive injury and might predispose E4 subjects to cognitive injury and an earlier onset or more severe extent of AD. The pathogenesis of this injury may involve loss or injury to neural precursor cells in the dentate subgranular zone (SGZ) of the hippocampus, which is involved in complex learning requiring the ability to learn about multiple relationships among stimuli. Disturbances in hippocampal functioning reduce spatial learning and memory. The granule cells of the dentate gyrus are involved in spatial memory and their radiation-induced depletion implicated in cognitive deficits. Our data show reduced numbers of proliferating cells and immature neurons and spatial learning and memory impairments in wild type mice x-irradiated at 2 months and behaviorally tested 3 months later. Treatments that damage neuronal precursor cells or their progeny might reduce neurogenesis and impair hippocampus-dependent cognitive functions in an E isoform-dependent fashion. Our data indicate that neuronal expression of E3 protects immature neurons against radiation injury and that E3 is more potent than E4 in supporting neuronal proliferation. After irradiation, SGZ precursor cells undergo rapid apoptotic cell death, which might involve oxidative stress. Oxidative stress might also play a critical role in later reductions in hippocampal neurogenesis. E isoforms differ in their ability to protect against neurotoxicity and apoptosis and oxidative stress. Isoform-specific effects of E on 56Fe radiation-induced oxidative stress, apoptosis, and loss of proliferating SGZ cells rapidly after 56Fe-irradiation or oxidative stress later after irradiation might contribute to their effects on cognitive injury later in life. We hypothesize that human E isoforms are associated with different levels of 56Fe-induced loss of neural precursor cells and hippocampus-dependent cognitive injury, and that these effects can be ameliorated by antioxidants. The Specific Aims are: 1A. Determine if E isoform is associated with radiation-induced apoptosis of neural precursor cells in the dentate SGZ; 1B. Determine the role of E isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ. Mice will be tested 3 months following radiation; 1C. Determine how E isoform affects neurogenesis following 56Fe- irradiation, and determine if this effect is related to the severity of radiation-induced cognitive deficits; 2A. Determine if the presence of a specific E isoform is associated with markers of oxidative stress following radiation injury; and 2B. Determine if the antioxidant a-lipoic acid enhances cognitive function and reduces radiation-induced cognitive impairments and whether this ability is E isoform-dependent. Mice will be irradiated with 56Fe ions (0 to 3 Gy). We will assess cognitive impairments using behavioral tests that require hippocampal functioning and quantify of radiation-induced changes using immunohistochemistry.

Research Impact/Earth Benefits: Our research impacts life on earth as it determines whether genetic risk factors for age-related cognitive decline are also risk factors for radiation-induced cognitive impairments. In case the anti-oxidant dietary supplement is able to antagonize these impairments, the impact would also constitute of a potential intervention against these challenges.

Task Progress & Bibliography Information FY2008 
Task Progress: During this grant year we finished the behavioral analysis and assessment of the number of doublecortin-positive immature neurons following behavioral testing of human apoE2, apoE3, and apoE4 transgenic female mice irradiated with 56Fe at a dose of 3 Gy at two months of age and behaviorally tested 3 months later. This experiment is most pertinent to Aim 1B. The data show that 56Fe radiation-induced cognitive injury is apoE isoform-dependent.

The mice were behaviorally analyzed in a battery of tests over a 5-week period. The mice were tested first for levels of anxiety and exploratory behavior in the open field, elevated zero maze, elevated plus maze, and light dark tests (week 1), than for sensorimotor function on the rotorod (week 2), next for novel location and novel object recognition (week 3), for spatial learning and memory in the water maze (week 4), and last for emotional learning and memory in the passive avoidance test (week 5).

There were no effects of irradiation on anxiety-like behaviors on any of these tests. Consistent with our previous 137Cesium study, an effect of genotype was observed in the plus maze; apoE4 mice spent less time than apo3 mice in the open arms (p < 0.01) and moved less than apoE2 (p < 0.05) and apoE3 (p < 0.01) mice in the plus maze, indicating increased anxiety and reduced exploratory behavior in apoE4 mice.

Irradiation impaired hippocampal-dependent novel location recognition of apoE2 mice. Neither sham-irradiated nor irradiated apoE4 mice spent more time exploring the monkey in its novel location. However unlike sham-irradiated mice, irradiated apoE4 mice showed a trend to explore the monkey more in its novel location (p= 0.14). Impairments in novel location recognition were not due to deficits in object recognition, as all mice showed a preference for a novel object in the hippocampal-independent novel object recognition task.

The water maze was used to assess spatial learning and memory. Cumulative distance which measures how far from the platform the mice searched was used to measure performance and performance of irradiated mice was compared to the performance of their sham-irradiated genotype-matched mice. Irradiation did not impair swim speed or motor function. Although not significant, irradiation appeared to impair the initial performance of apoE2 (p = 0.15) but enhance that of apoE4 (p = 0.11) mice in the hidden platform sessions. In the first probe trial, irradiation impaired spatial memory retention of apoE2 (p < 0.05) mice and strikingly enhanced that of apoE3 and apoE4 (p < 0.05) mice. There was no effect of irradiation with further training.

These effects were not associated with a potential differential ability of apoE isoforms to protect against effects of irradiation on neurogenesis. The number of doublecortin-positive immature neurons in the dentate gyrus was dramatically and similarly reduced following 56Fe irradiation in all three genotypes (p < 0.001). Thus, there is no simple relationship between neurogenesis and cognitive function and other mechanisms contribute to the differential cognitive outcomes in the context of a particular apoE isoform.

The 56Fe data are opposite to what was observed following irradiation with 137Cesium. Following 137Cesium irradiation, apoE2 mice were protected while apoE4 mice were most susceptible to cognitive injury. These paradoxical effects may be related to the differential effects of these two sources of irradiation on neurogenesis. Therefore, we also assessed the effects of 137Cs irradiation on doublecortin-positive cells in the dentate gyrus of the hippocampus from behaviorally tested mice. Similar reductions in doublecortin-positive cells were observed in all genotypes, indicating that the differential effects of the two types of radiation on hippocamapal function were not due to potential differences on inhibition of neurogenesis. It is possible that a different dose rather than a different source of irradiation may account for differences in cognitive function following irradiation.

As it is possible that the effects of 56Fe irradiation on brain function of apoE4 mice are age-dependent, we irradiated 6-month-old human apoE mice with 56Fe at a dose of 3 Gy and tested them 3 later. In the first water maze probe trial (following the first day of hidden platform training), irradiation impaired spatial memory retention of only apoE2 mice. While apoE4 sham-irradiated male mice did not show spatial memory retention in the first probe trial, irradiated apoE4 male mice did. These data show that 56Fe irradiation at a dose of 3 Gy worsens cognitive function in apoE2 mice but enhances cognitive function in apoE4 mice and that these effects are seen when the mice are irradiated at 2 or at 6 months of age.

The ability of 56Fe irradiation to potentially impair or enhance cognitive function is not limited to human apoE transgenic mice. To determine whether doses lower than 3 Gy affect hippocampal function 3 months following irradiation, female and male C57Bl/6J wild-type mice were irradiated with 56Fe at a dose of 0, 1, 2, or 3 Gy at 2 months of age and cognitively tested 3 months later. This study was also undertaken to assess which lower doses should be used in future studies with apoE transgenic mice. There were no effects of irradiation on behavioral performance in the open field. Consistent with previous studies, the female mice were less active in the open field (F(1,49) = 9.06, p = 0.04). In the elevated zero maze, there was a sex x dose interaction (F(3,49) = 0.028, p < 0.05). While irradiation reduced measures of anxiety in the female mice, it increased measures of anxiety in the male mice.

To determine whether a more challenging water maze test version involving reversal learning (a novel hidden platform location) is able to detect effects of irradiation on cognitive performance in male mice, C57BL/6J mice were irradiated with 56Fe at 0, 1, 2, or 3 Gy (n = 8 mice/dose) and cognitively tested 3 months later. While the sham-irradiated mice showed spatial memory retention and searched more time in the target quadrant than any other quadrant, the mice irradiated at 1, 2, or 3 Gy did not. These data show this more challenging water maze paradigm involving 2 instead of 1 hidden platform location is sensitive to effects of irradiation in male mice.

Next we determine the effects of irradiation on hippocampus-dependent contextual and hippocampus-independent cued fear conditioning. In the fear conditioning task, mice learn to associate a neutral stimulus (audio tone, CS) with a foot shock (US) and thereby come to fear the previously neutral CS. Trained mice display this conditioned fear by ceasing all movement except for respiration in an attitude called 'freezing.’ After a 2 min period, during which the mouse is allowed to explore the experimental chamber, a tone is delivered followed in 30 sec by a foot shock (0.35 or 0.9 mA over 2 seconds). This was repeated 4.5 min later. One day later the mice were placed in the same context (environment) and, 1 hour later, in a new context (novel environment; different floor, walls, and smell) containing only the tone stimulus (cued). In a first experiment, we compared the shock intensity of 0.35 and 0.9 mA on fear conditioning on naïve (not irradiated) Wt male mice. A third group of animals was exposed to the same paradigm but no shock was delivered. Both 0.35 and 0.9 mA increased hippocampal-dependent contextual freezing but the freezing was more pronounced following a shock intensity of 0.9 mA. In contrast, both intensities elicited a comparable hippocampal-independent cued fear conditioning. Based on these data, the 0.35 mA intensity was used to asses fear conditioning in 2-month-old female and male C57BL/6J mice irradiated with 56Fe at 0, 1 or 3 Gy (n = 8 mice/dose) and cognitively tested 3 mo later. The female mice irradiated at 1 or 3 Gy showed impairments in contextual fear conditioning as compared to sham-irradiated mice. Following irradiation at a dose of 2 Gy, there was a trend towards an effect but that did not reach significance. In contrast, in male mice, irradiation at a dose of 1 or 2 Gy enhanced contextual fear conditioning. Following irradiation at a dose of 3 Gy, there was no enhancement in contextual fear conditioning. In contrast to contextual fear conditioning, no effects of irradiation were seen in cued fear conditioning in female or male mice. Thus, hippocampus-dependent contextual fear conditioning, but not hippocampus-independent cued fear conditioning, is sensitive to the effects of 1 Gy of 56Fe ions in a sex-dependent fashion. While female mice perform worse following irradiation, male mice perform better. These data indicate that hippocampus-dependent cognitive impairments occur after relatively low doses of irradiation. Based on these data, mice were irradiated at doses below 1 Gy and they will be cognitively tested in the next grant year.

Bibliography Type: Description: (Last Updated: 07/23/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Villasana L, Poage C, van Meer P, Raber J. "Passive avoidance learning and memory of 56Fe sham-irradiated and irradiated human apoE transgenic mice." Radiation Biology Radioecology, 2008 Jan;48:191-4. , Jan-2008
Articles in Peer-reviewed Journals Acevedo SF, Tittle S, Merry DE, Raber J. "Transgenic expression of androgen receptors improves spatial memory retention of sham-irradiated and 137Cesium irradiated female mice." Radiation Research, provisionally accepted, June 2008. , Jun-2008
Project Title:  Neurogenesis and cognition in human apoE transgenic mice following 56Fe radiation Reduce
Fiscal Year: FY 2007 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 09/01/2005  
End Date: 08/31/2009  
Task Last Updated: 06/28/2007 
Download report in PDF pdf
Principal Investigator/Affiliation:   Raber, Jacob  Ph.D. / Oregon Health & Science University 
Address:  Behavioral Neuroscience and Neurology 
L470, 3181 SW Sam Jackson Park Road 
Portland , OR 97239-3011  
Email: raberj@ohsu.edu  
Phone: 503-494-1524  
Congressional District:
Web:  
Organization Type: UNIVERSITY 
Organization Name: Oregon Health & Science University 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Fike, John  UCSF 
Key Personnel Changes / Previous PI: 0
Project Information: Grant/Contract No. NNJ05HE63G 
Responsible Center: NASA JSC 
Grant Monitor:  
Center Contact:   
Solicitation / Funding Source: 2004 Radiation Biology NNH04ZUU005N 
Grant/Contract No.: NNJ05HE63G 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) CNS:Risk of Acute (In-flight) and Late Central Nervous System Effects from Radiation Exposure (IRP Rev G)
Human Research Program Gaps: (1) CNS01:What are significant adverse changes in CNS performance in the context and time scale of space flight operations? How is significance defined, and which neuropsychological domains are affected? Is there a significant probability that space radiation exposure would result in adverse changes? What are the pathways and mechanisms of change? (IRP Rev F)
Flight Assignment/Project Notes: NOTE: End date changed back to 8/31/2009 per S. Krenek/JSC (8/07)

End date changed to 9/30/2009 per JSC update info (10/06)

Task Description: Of the major human isoforms of apolipoprotein E (E), E4 is associated with age-related cognitive decline and increased risk to develop Alzheimer’s disease (AD). The space radiation environment contains 56Fe. 56Fe radiation exposure causes cognitive injury and might predispose E4 subjects to cognitive injury and an earlier onset or more severe extent of AD. The pathogenesis of this injury may involve loss or injury to neural precursor cells in the dentate subgranular zone (SGZ) of the hippocampus, which is involved in complex learning requiring the ability to learn about multiple relationships among stimuli. Disturbances in hippocampal functioning reduce spatial learning and memory. The granule cells of the dentate gyrus are involved in spatial memory and their radiation-induced depletion implicated in cognitive deficits. Our data show reduced numbers of proliferating cells and immature neurons and spatial learning and memory impairments in wild type mice x-irradiated at 2 months and behaviorally tested 3 months later. Treatments that damage neuronal precursor cells or their progeny might reduce neurogenesis and impair hippocampus-dependent cognitive functions in an E isoform-dependent fashion. Our data indicate that neuronal expression of E3 protects immature neurons against radiation injury and that E3 is more potent than E4 in supporting neuronal proliferation. After irradiation, SGZ precursor cells undergo rapid apoptotic cell death, which might involve oxidative stress. Oxidative stress might also play a critical role in later reductions in hippocampal neurogenesis. E isoforms differ in their ability to protect against neurotoxicity and apoptosis and oxidative stress. Isoform-specific effects of E on 56Fe radiation-induced oxidative stress, apoptosis, and loss of proliferating SGZ cells rapidly after 56Fe-irradiation or oxidative stress later after irradiation might contribute to their effects on cognitive injury later in life. We hypothesize that human E isoforms are associated with different levels of 56Fe-induced loss of neural precursor cells and hippocampus-dependent cognitive injury, and that these effects can be ameliorated by antioxidants. The Specific Aims are: 1A. Determine if E isoform is associated with radiation-induced apoptosis of neural precursor cells in the dentate SGZ; 1B. Determine the role of E isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ. Mice will be tested 3 months following radiation; 1C. Determine how E isoform affects neurogenesis following 56Fe- irradiation, and determine if this effect is related to the severity of radiation-induced cognitive deficits; 2A. Determine if the presence of a specific E isoform is associated with markers of oxidative stress following radiation injury; and 2B. Determine if the antioxidant a-lipoic acid enhances cognitive function and reduces radiation-induced cognitive impairments and whether this ability is E isoform-dependent. Mice will be irradiated with 56Fe ions (0 to 3 Gy). We will assess cognitive impairments using behavioral tests that require hippocampal functioning and quantify of radiation-induced changes using immunohistochemistry.

Research Impact/Earth Benefits: Our research impacts life on earth as it determines whether genetic risk factors for age-related cognitive decline are also risk factors for radiation-induced cognitive impairments. In case the anti-oxidant dietary supplement is able to antagonize these impairments, the impact would also constitute of a potential intervention against these challenges.

Task Progress & Bibliography Information FY2007 
Task Progress: We started to test the hypothesis that 56Fe radiation-induced cognitive injury is sex- and apoE isoform-dependent by sham-irradiating or irradiating two-month-old male and female mice expressing human apoE2, apoE3 or apoE4 under the control of the mouse apoE promoter at 3 Gy and behaviorally testing them in a battery of tests at least three months later. This dose was selected because it was shown to cause a profound reduction in proliferating cells and immature neurons without inducing obvious tissue destruction. This experiment is most pertinent to Aim 1B of our grant proposal:

“1B. Determine the role of apoE isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ.” We also started to irradiate mice at BNL to look at short term-effects on neurogenesis in the dentate gyrus of the hippocampus. The brains of these mice are being processed for immunohistochemistry.

Two-month-old mice (n = 106) bred in our mouse colony at OHSU were sent to BNL for brain only 56Fe irradation (3 Gy) or sham irradiation in June 2006. Each mouse was anesthetized using mouse cocktail. The mice designated for irradiation were placed in positional cradles to stabilize the head position during irradiation. The cradles were placed in a box designed for the beam line. The whole-head of each mouse was irradiated with a 600 MeV/amu iron particles. A few days afterwards, the mice were shipped to OHSU for cognitive testing and tissue analyses. As we can maximally test 25 mice simultaneously in the object recognition and water maze tests, groups of 25 mice each were behaviorally analyzed in a battery of tests over a 5-week period. The researcher testing the mice was blinded to the genotype and treatment of the mice. To minimize the effect of stress on behavioral performance, the mice were tested first for levels of anxiety and exploratory behavior in the open field, elevated zero maze, elevated plus maze, and light dark tests (week 1), than for sensorimotor function on the rotorod (week 2), next for novel location and novel object recognition (week 3), for spatial learning and memory in the water maze (week 4), and last for emotional learning and memory in the passive avoidance test (week 5). The testing of the last cohort of 25 mice started in January, 2007. The researcher testing the mice was blinded to the genotype and treatment of the mice.

Exploratory behavior and measures of anxiety were first tested in the open field. There were no effects of apoE on activity or measures of anxiety in the open field. To assess activity and measures of anxiety, the elevated zero maze, elevated plus maze, and light- dark tests were also used. In the zero maze, there was an effect of genotype on activity (F = 6,514, p = 0.002). ApoE4 mice were less active than apoE2 (p = 0.003) and apoE3 (p = 0.011) mice. Consistent with the elevated zero maze, there was a similar effect of genotype on activity in the light-dark test (F = 3.947, p = 0.023). ApoE4 mice were less active than apoE2 (p = 0.047) and apoE3 (p = 0.038) mice. These differential effects of apoE on measures of activity in the elevated zero maze and light-dark tests are similar to the effects found in sham- and Cesium-irradiated 5-month-old apoE2, apoE3, and apoE4 transgenic mice irradiated at 10 Gy at OHSU at 2 months of age.

In contrast to the open field, elevated zero maze, and light-dark test, there were effects of genotypes and treatment on performance in elevated plus maze. There were effects of genotype on ratio time spent in the open arms of the elevated plus maze (time spent in open arms/(time spent in open + closed arms) (F = 8.12, p = 0.001). ApoE4 mice spent less time in the open arms than apoE3 (p =0.005) mice and apoE2 spent less time in the open arms than apoE3 mice (p = 0.002). Similarly, there was an effect of genotype on distance moved in the open arms (F = 11.24, p < 0.001). ApoE4 mice moved less in the open arms than apoE3 mice (p =0.001) and apoE2 mice moved in the open arms than apoE3 mice (p = 0.002). For pokes into the open arms, there was an effect of sex (F = 4.584, p =0.035) and a sex x treatment interaction (F = 4.7, p = 0.033). In female mice, irradiated mice poked more into the open arms than sham-irradiated mice (p = 0.027). Such effects were not found for pokes into the closed arms. There was only an effect of sex on pokes into the closed arms (F = 19.658, p < 0.001). For extending over the edges of the open arms, there was a genotype x sex x treatment interaction (F = 4.3, p = 0.016). Finally, there were effects of genotype (F = 12.278, p < 0.001) and treatment (F = 6.67, p = 0.001) on entries into the intersection. ApoE4 mice entered the intersection less than apoE2 (p = 0.002) or apoE3 (p < 0.001) mice. In addition, irradiated mice entered the intersection more than sham-irradiated mice (F = 4.793, p = 0.031). As the intersection is neither closed nor open and relates to measures of risk assessment, these data indicate that 56Fe irradiation increases risk assessment in human apoE transgenic mice. Consistent with interpretation, irradiated female mice poked more into the open arms than sham-irradiated female mice. This indicates that the effects of irradiation on risk assessment is more profound in females than males.

To assess hippocampus-dependent cognitive function, the mice were subsequently tested for novel location and novel object recognition, spatial learning and memory in the water maze, and for emotional learning and memory in the passive avoidance test. Sham-irradiated apoE2 and apoE3 female and male mice showed novel location recognition but irradiated apoE2 and apoE3 female and male mice did not. In contrast, while sham-irradiated apoE4 female and male mice failed to show novel location recognition, irradiated apoE4 female and male mice did. In contrast to novel location recognition, there were no effects of irradiation on novel object recognition. During the visible and hidden session of the water maze, there was an effect of genotype on time to reach the platform (latency) (apoE4 was different from apoE2 and apoE3). During the hidden session of the water maze, there was also a genotype x treatment interaction. Similar to the novel location recognition data, irradiation increased the latency of apoE2 mice but reduced the latency of apoE4 mice. Finally, irradiation impaired spatial memory retention in the probe trial in apoE2 female mice but improved spatial memory retention in apoE4 female and male mice. These data demonstrate that the effects of 56Fe irradiation on hippocampus-dependent cognitive function in mice are critically modulated by apoE isoform. The enhanced cognitive performance of apoE4 mice following 56Fe irradiation is exactly the opposite from the results we obtained in Cesium irradiated mice. Following Cesium irradiation, male mice were not affected and apoE4 female mice were particularly affected. These results indicate that the source of irradiation is critically modulating the direction of the effects of irradiation on brain function. Currently we are processing the brains of the behaviorally tested mice for immunohistochemistry. In particular, we plan to assess neurogenesis in these mice as proposed. As it is possible that these effects of 56Fe irradiation on brain function of apoE4 mice are age-dependent we irradiated older human apoE mice at BNL in May of 2007 and will start testing them at least 3 months following irradiation. This will show whether 56Fe irradiation worsens cognitive function in older apoE4 mice and that the excited, but unexpected, results are only detected in mice irradiated at 2 months of age.

Bibliography Type: Description: (Last Updated: 07/23/2021)  Show Cumulative Bibliography Listing
 
Abstracts for Journals and Proceedings Villasana L, Acevedo S, Poage C, Raber J. "Effects of Cesium Irradiation on Cognitive Function: Role of Sex- and Apolipoprotein E Isoform. " 4th Intl 17th Annual NASA Space Radiation Investigators' Workshop 2006, Moscow-St. Petersburg, Russia, June 2006.

4th Intl 17th Annual NASA Space Radiation Investigators' Workshop 2006, June 2006. , Jun-2006

Abstracts for Journals and Proceedings Villasana L, Acevedo S, Poage C, Raber J. "Sex- and ApoE Isoform-dependent effects of radiation on cognitive function." Society for Neuroscience Oregon Chapter Annual Meeting 2006, Salishan, Oregon, July 2006.

Society for Neuroscience Oregon Chapter Annual Meeting 2006, July 2006. , Jul-2006

Abstracts for Journals and Proceedings Villasana L, Acevedo S, Poage C, Raber J. "Sex- and ApoE Isoform-dependent effects of radiation on cognitive function." Society for Neuroscience Annual Meeting 2006, Atlanta, GA, U.S.A., November 2006.

Society for Neuroscience Annual Meeting 2006, November 2006. , Nov-2006

Abstracts for Journals and Proceedings Raber J, Villasana L, Poage C, van Meer P. "Cognition in human apoE transgenic mice following 56Fe radiation." NASA Human Research Program Investigators’ Workshop 2007, League City, Texas, February 2007.

NASA Human Research Program Investigators’ Workshop, League City, Texas, February 2007. , Feb-2007

Articles in Peer-reviewed Journals Villasana L, Acevedo SF, Poage C, Raber J. "Sex- and ApoE Isoform-dependent effects of radiation on cognitive function." Radiat Res. 2006 Dec;166(6):883-91. PMID: 17149978 , Dec-2006
Awards Villasana L, Acevedo S, Poage C, Raber J. "Student Research Forum OHSU 2006, Oregon, U.S.A. Sex- and ApoE Isoform-dependent effects of radiation on cognitive function. Awarded Best Poster. " Sep-2006
Project Title:  Neurogenesis and cognition in human apoE transgenic mice following 56Fe radiation Reduce
Fiscal Year: FY 2006 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 09/01/2005  
End Date: 09/30/2009  
Task Last Updated: 07/05/2006 
Download report in PDF pdf
Principal Investigator/Affiliation:   Raber, Jacob  Ph.D. / Oregon Health & Science University 
Address:  Behavioral Neuroscience and Neurology 
L470, 3181 SW Sam Jackson Park Road 
Portland , OR 97239-3011  
Email: raberj@ohsu.edu  
Phone: 503-494-1524  
Congressional District:
Web:  
Organization Type: UNIVERSITY 
Organization Name: Oregon Health & Science University 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Fike, John R UCSF 
Key Personnel Changes / Previous PI: 0
Project Information: Grant/Contract No. NNJ05HE63G 
Responsible Center: NASA JSC 
Grant Monitor:  
Center Contact:   
Solicitation / Funding Source: 2004 Radiation Biology NNH04ZUU005N 
Grant/Contract No.: NNJ05HE63G 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) CNS:Risk of Acute (In-flight) and Late Central Nervous System Effects from Radiation Exposure (IRP Rev G)
Human Research Program Gaps: (1) CNS01:What are significant adverse changes in CNS performance in the context and time scale of space flight operations? How is significance defined, and which neuropsychological domains are affected? Is there a significant probability that space radiation exposure would result in adverse changes? What are the pathways and mechanisms of change? (IRP Rev F)
Flight Assignment/Project Notes: End date changed to 9/30/2009 per JSC update info (10/06)

Task Description: Of the major human isoforms of apolipoprotein E (E), E4 is associated with age-related cognitive decline and increased risk to develop Alzheimer’s disease (AD). The space radiation environment contains 56Fe. 56Fe radiation exposure causes cognitive injury and might predispose E4 subjects to cognitive injury and an earlier onset or more severe extent of AD. The pathogenesis of this injury may involve loss or injury to neural precursor cells in the dentate subgranular zone (SGZ) of the hippocampus, which is involved in complex learning requiring the ability to learn about multiple relationships among stimuli. Disturbances in hippocampal functioning reduce spatial learning and memory. The granule cells of the dentate gyrus are involved in spatial memory and their radiation-induced depletion implicated in cognitive deficits. Our data show reduced numbers of proliferating cells and immature neurons and spatial learning and memory impairments in wild type mice x-irradiated at 2 months and behaviorally tested 3 months later. Treatments that damage neuronal precursor cells or their progeny might reduce neurogenesis and impair hippocampus-dependent cognitive functions in an E isoform-dependent fashion. Our data indicate that neuronal expression of E3 protects immature neurons against radiation injury and that E3 is more potent than E4 in supporting neuronal proliferation. After irradiation, SGZ precursor cells undergo rapid apoptotic cell death, which might involve oxidative stress. Oxidative stress might also play a critical role in later reductions in hippocampal neurogenesis. E isoforms differ in their ability to protect against neurotoxicity and apoptosis and oxidative stress. Isoform-specific effects of E on 56Fe radiation-induced oxidative stress, apoptosis, and loss of proliferating SGZ cells rapidly after 56Fe-irradiation or oxidative stress later after irradiation might contribute to their effects on cognitive injury later in life. We hypothesize that human E isoforms are associated with different levels of 56Fe-induced loss of neural precursor cells and hippocampus-dependent cognitive injury, and that these effects can be ameliorated by antioxidants. The Specific Aims are: 1A. Determine if E isoform is associated with radiation-induced apoptosis of neural precursor cells in the dentate SGZ; 1B. Determine the role of E isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ. Mice will be tested 3 months following radiation; 1C. Determine how E isoform affects neurogenesis following 56Fe- irradiation, and determine if this effect is related to the severity of radiation-induced cognitive deficits; 2A. Determine if the presence of a specific E isoform is associated with markers of oxidative stress following radiation injury; and 2B. Determine if the antioxidant a-lipoic acid enhances cognitive function and reduces radiation-induced cognitive impairments and whether this ability is E isoform-dependent. Mice will be irradiated with 56Fe ions (0 to 3 Gy). We will assess cognitive impairments using behavioral tests that require hippocampal functioning and quantify of radiation-induced changes using immunohistochemistry.

Research Impact/Earth Benefits: Our research impacts life on earth as it determines whether genetic risk factors for age-related cognitive decline are also risk factors for radiation-induced cognitive impairments. In case the anti-oxidant dietary supplement is able to antagonize these impairments, the impact would also constitute of a potential intervention against these challenges.

Task Progress & Bibliography Information FY2006 
Task Progress: This month (June 2006) was the first time the beam at BNL was available to our research. As the animals will be tested behaviorally three months following irradiation, these data are not available yet. However, we generated data using Cesium irradiation. These data, which are summarized in more detail below, indicate that the isoform-dependent effects of apoE on cognitive function are sex-dependent with female mice being more susceptible to radiation-induced cognitive impairments than male mice. While our proposals only included studies of male mice, we believe that these results are very important and bring up new critical path questions concerning the role of sex in the effects of irradiation ob cognitive function, particularly in the context of apoE. Importantly, the risk to develop Alzheimer’s disease (AD) in people carrying apoE4 is sex-dependent. Women are at higher risk to develop AD than men, and particularly women carrying apoE4. There is an synergistic interaction between female sex and apoE4 in risk to develop AD. It is conceivable that radiation might increase the risk of age-related cognitive decline and development of AD in a sex- and apoE isoform-dependent fashion.

To determine the potential effects of apoE isoform and sex on radiation-induced cognitive impairments, we irradiated, using Cesium irradiation at 10 Gy, two-month-old apoE2, apoE3, and apoE4 male and female mice and assessed their cognitive performance three months later. When hippocampus-dependent spatial learning and memory was assessed in the water maze, sham-irradiated apoE2, apoE3 and apoE4 and irradiated apoE2 female mice showed spatial memory retention, but irradiated apoE3 and apoE4 female mice did not. Compared to sham-irradiated apoE4 female mice, irradiated apoE4 female mice also required more trials to reach criterion in the hippocampus-dependent passive avoidance test. Irradiation had no effects on water maze or passive avoidance learning and memory of male apoE2, apoE3, or apoE4 mice, indicating that the effects of radiation on cognitive performance are sex- and apoE isoform-dependent. These results show that brain irradiation induces sex- and apoE isoform-dependent cognitive impairments. The lack of effects of irradiation on spatial memory retention of apoE2 female mice is consistent with the relative protection of apoE2 carriers in risk to develop AD. While irradiation affected passive avoidance learning of apoE4, but not apoE3, female mice, it affected water maze performance of both apoE3 and apoE4 female mice. A differential susceptibility of apoE3 and apoE4 female mice to irradiation-induced cognitive-impairments in the water maze might be revealed at a lower or higher irradiation dose. In addition, in contrast to the effects of irradiation on the water maze learning curves in this study stronger effects of irradiation on water maze learning curves might have been detected at higher irradiation doses and/or at longer follow-up times. Deficits in water maze performance were detected following higher irradiation doses (21-25 Gy) and longer follow-up times.

These result show higher anxiety levels in 5-month-old apoE4 than age-matched apoE3 mice expressing apoE under control of the mouse apoE promoter. These data are consistent with the higher anxiety levels of 6-month-old Apoe-/- male mice expressing apoE4 in neurons or astrocytes than those expressing apoE3 in neurons or astrocytes and with the higher anxiety levels of probable AD patients with only apoE4 than those with only apoE3. ApoE4 female and male mice moved less than sex-matched apoE3 mice in the open field, light-dark, and elevated zero maze. In the elevated plus maze, apoE4 female mice moved less than apoE3 female mice but this genotype difference did not reach significance in the genotype-matched male mice. Taken together, these data indicate that apoE4 mice move less than apoE3 mice in novel environments. This could be related to increased measures of anxiety and/or reduced exploratory drive in the context of apoE4.

In the first two visible sessions of visible platform training, irradiated apoE2 female mice performed less than sham-irradiated apoE2 female mice. These data indicate that in apoE2 female mice irradiation impaired initial task learning. In the elevated zero maze, there was a trend towards lower measures of anxiety in irradiated than sham-irradiated apoE2 female mice. Therefore, it is possible that irradiated apoE2 female mice showed this initial task learning deficit in the water maze as they might have been slightly less motivated to learn how to escape the water.

While anxiety can influence performance in the water maze probe trials, differences in anxiety levels did not contribute to the spatial memory retention deficits in irradiated apoE3 and apoE4 female mice. Irradiation or sex had no effects on measures of anxiety in the anxiety tests used or on time spent in the outer zone of the water maze. In addition, while apoE2 mice showed higher measures of anxiety than apoE3 mice, apoE3, but not apoE2, female mice showed spatial memory retention deficits following irradiation. Finally, the isoform-dependent effets of apoE on measures of anxiety were more pronounced in males than females but the radiation-induced impairments in water maze performance were only seen in females. In contrast to the water maze, isoform-dependent effects of apoE on measures of anxiety might have contributed to the better passive avoidance learning of apoE4 than apoE3 or apoE2 mice. Trials to reach criterion in the passive avoidance test correlated with measures of anxiety in the elevated zero maze, elevated plus maze, and light-dark tests. When sensorimotor function was assessed on the rotorod, apoE3 mice showed lower fall latencies than sex-matched apoE2 or apoE4 mice but irradiation had no effect on rotorod performance. In addition, female mice, which showed increased susceptibility to radiation-induced cognitive impairments, showed higher fall latencies than male mice. These data indicate that potential alterations in sensorimotor function did not contribute to the observed radiation-induced alterations in cognitive performance in apoE3 and apoE4 female mice. In summary, these data show sex- and apoE isoform-dependent effects of Cesium irradiation on water maze and passive avoidance performance. Both tests are hippocampus-dependent and the mechanisms underlying these effects might involve alterations in neurogenesis in the subgranular zone of the hippocampal dentate gyrus and in subsequent migration of newly born cells into the dentate granule cell layer. As the effects of radiation on cognitive injury are not transient and observed in rodents one year after irradiation, radiation exposure might predispose to age-dependent cognitive decline and an earlier onset or more severe extent of neurodegenerative diseases such as AD in a sex- and apoE isoform-dependent fashion.

Bibliography Type: Description: (Last Updated: 07/23/2021)  Show Cumulative Bibliography Listing
 
Abstracts for Journals and Proceedings Villasana L, Acevedo S, Poage C, Raber J. "Effects of Cesium Irradiation on Cognitive Function: Role of Sex- and Apolipoprotein E Isoform. " 4th Intl 17th Annual NASA Space Radiation Investigators' Workshop 2006, Moscow-St. Petersburg, Russia, June 2006.

4th Intl 17th Annual NASA Space Radiation Investigators' Workshop 2006, June 2006. , Jun-2006

Abstracts for Journals and Proceedings Villasana L, Acevedo S, Poage C, Raber J. "Sex- and ApoE Isoform-dependent effects of radiation on cognitive function. " Society for Neuroscience Oregon Chapter Annual Meeting, Salishan, Oregon, 2006.

Society for Neuroscience Oregon Chapter Annual Meeting, 2006. , Jun-2006

Abstracts for Journals and Proceedings Villasana L, Acevedo S, Poage C, Raber J. "Sex- and ApoE Isoform-dependent effects of radiation on cognitive function. " Society for Neuroscience Annual Meeting 2006, Atlanta, GA, October 2006.

Society for Neuroscience Annual Meeting, October 2006. , Oct-2006

Awards Villasana L, Acevedo S, Poage C, Raber J. "Awarded Best Poster , Student Research Forum OHSU 2006, Oregon." Mar-2006
Project Title:  Neurogenesis and cognition in human apoE transgenic mice following 56Fe radiation Reduce
Fiscal Year: FY 2005 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 09/01/2005  
End Date: 08/31/2009  
Task Last Updated: 02/08/2006 
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Principal Investigator/Affiliation:   Raber, Jacob  Ph.D. / Oregon Health & Science University 
Address:  Behavioral Neuroscience and Neurology 
L470, 3181 SW Sam Jackson Park Road 
Portland , OR 97239-3011  
Email: raberj@ohsu.edu  
Phone: 503-494-1524  
Congressional District:
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Organization Type: UNIVERSITY 
Organization Name: Oregon Health & Science University 
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Key Personnel Changes / Previous PI: 0
Project Information: Grant/Contract No. NNJ05HE63G 
Responsible Center: NASA JSC 
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Solicitation / Funding Source: 2004 Radiation Biology NNH04ZUU005N 
Grant/Contract No.: NNJ05HE63G 
Project Type: GROUND 
Flight Program:  
TechPort: No 
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Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) CNS:Risk of Acute (In-flight) and Late Central Nervous System Effects from Radiation Exposure (IRP Rev G)
Human Research Program Gaps: (1) CNS01:What are significant adverse changes in CNS performance in the context and time scale of space flight operations? How is significance defined, and which neuropsychological domains are affected? Is there a significant probability that space radiation exposure would result in adverse changes? What are the pathways and mechanisms of change? (IRP Rev F)
Task Description: Of the major human isoforms of apolipoprotein E (E), E4 is associated with age-related cognitive decline and increased risk to develop Alzheimer’s disease (AD). The space radiation environment contains 56Fe. 56Fe radiation exposure causes cognitive injury and might predispose E4 subjects to cognitive injury and an earlier onset or more severe extent of AD. The pathogenesis of this injury may involve loss or injury to neural precursor cells in the dentate subgranular zone (SGZ) of the hippocampus, which is involved in complex learning requiring the ability to learn about multiple relationships among stimuli. Disturbances in hippocampal functioning reduce spatial learning and memory. The granule cells of the dentate gyrus are involved in spatial memory and their radiation-induced depletion implicated in cognitive deficits. Our data show reduced numbers of proliferating cells and immature neurons and spatial learning and memory impairments in wild type mice x-irradiated at 2 months and behaviorally tested 3 months later. Treatments that damage neuronal precursor cells or their progeny might reduce neurogenesis and impair hippocampus-dependent cognitive functions in an E isoform-dependent fashion. Our data indicate that neuronal expression of E3 protects immature neurons against radiation injury and that E3 is more potent than E4 in supporting neuronal proliferation. After irradiation, SGZ precursor cells undergo rapid apoptotic cell death, which might involve oxidative stress. Oxidative stress might also play a critical role in later reductions in hippocampal neurogenesis. E isoforms differ in their ability to protect against neurotoxicity and apoptosis and oxidative stress. Isoform-specific effects of E on 56Fe radiation-induced oxidative stress, apoptosis, and loss of proliferating SGZ cells rapidly after 56Fe-irradiation or oxidative stress later after irradiation might contribute to their effects on cognitive injury later in life. We hypothesize that human E isoforms are associated with different levels of 56Fe-induced loss of neural precursor cells and hippocampus-dependent cognitive injury, and that these effects can be ameliorated by antioxidants. The Specific Aims are: 1A. Determine if E isoform is associated with radiation-induced apoptosis of neural precursor cells in the dentate SGZ; 1B. Determine the role of E isoform in the development of radiation-induced cognitive deficits and whether the severity of these deficits are associated with apoptosis of neural precursor cells in the dentate SGZ. Mice will be tested 3 months following radiation; 1C. Determine how E isoform affects neurogenesis following 56Fe- irradiation, and determine if this effect is related to the severity of radiation-induced cognitive deficits; 2A. Determine if the presence of a specific E isoform is associated with markers of oxidative stress following radiation injury; and 2B. Determine if the antioxidant a-lipoic acid enhances cognitive function and reduces radiation-induced cognitive impairments and whether this ability is E isoform-dependent. Mice will be irradiated with 56Fe ions (0 to 3 Gy). We will assess cognitive impairments using behavioral tests that require hippocampal functioning and quantify of radiation-induced changes using immunohistochemistry.

Research Impact/Earth Benefits: 0

Task Progress & Bibliography Information FY2005 
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Bibliography Type: Description: (Last Updated: 07/23/2021)  Show Cumulative Bibliography Listing
 
 None in FY 2005