Page 109 - 2014 Printable Abstract Book
P. 109
study was to investigate persistent effects of a sub-lethal radiation dose (2 Gy) on autophagy, and oxidant
and anti-oxidant pathways, which are interlinked processes affecting intestinal cell homeostasis. Methods
and materials: Six to eight weeks old C57BL/6J mice (n=10 mice per group) were exposed to 2 Gy γ
radiation (dose rate: 0.7 Gy/min). Mice were humanely euthanized 2-month after radiation exposure, the
intestine surgically removed, and flushed using sterile buffered saline. Parts of the intestine from the
jejuno-ilial region were fixed, frozen, or used for intestinal epithelial cell (IEC) isolation. While oxidant level
and mitochondrial status was assessed in isolated cells, autophagy and oxidative stress related signaling
pathways were probed in frozen and fixed samples using PCR-based expression array,
immunohistochemistry, and immunoblots. Results: Radiation exposure caused significant alterations in
the expression level of 28 autophagy and 17 oxidative stress related genes. While 11 genes involved in
initiating and regulating autophagy pathway were downregulated, 15 genes involved in anti-oxidant
activity were downregulated after radiation. Immunoblot results showed decreased Beclin1 and LC3B and
increased PI3K/Akt and mTOR signaling. Flow cytometry data showed increased oxidant production and
compromised mitochondrial integrity in irradiated samples. Radiation exposure was associated with
increased oxidative DNA damage as well as increased nuclear PCNA staining in IEC. Conclusions: Our study
provides insight into molecular events associated with long-term perturbation of intestinal function after
exposure to ionizing radiation. Radiation-induced inhibition of autophagy and promotion of oxidative
stress could work in tandem to trigger an intestinal inflammatory response reported earlier and has
implications for functional dysbalance in the gastrointestinal tract.
(PS1-10) Exposure to 1 Gy total body proton irradiation causes long-term damage to hematopoietic
1
1
2
1
1
1
stem cells in mice. Jianhui chang ; Wei Feng ; Yingying Wang ; Yi Luo ; Antiño R Allen ; Jennifer Turner ;
1
1
2
Blair Stewart ; Jacob Raber 2;3;4 ; Daohong Zhou ; and Lijian Shao, Division of Radiation Health, Department
of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, UAMS, little rock, AR ;
1
2
Departments of Behavioral Neuroscience, ONPRC, Oregon Health and Science University, Portland, OR ;
3
Department of Neurology, Oregon Health and Science University, Portland, OR ; and Division of
Neuroscience, Oregon Health and Science University, Portland, OR
4
Exploratory missions to planets or asteroids supported by the National Aeronautics and Space
Administration (NASA) will expose astronauts certain health risks. In the space radiation environment,
protons account for more than 80% of deep-space radiation. Additionally, proton radiation has been
increasingly used in clinic to treat cancer. Therefore, there is an urgent need to better understand the
biological effects of proton radiation on the body. This knowledge will lead to a more accurate assessment
of the potential health risk of proton radiation and the development of a better strategy to prevent and
mitigate the adverse effects of proton radiation. Previous studies have shown that exposure to low doses
of proton is detrimental to mature leukocyte populations in peripheral blood but the underlying
mechanism is not known. It may be attributable to damage to hematopoietic stem cells (HSCs) that have
the ability to self-renew, proliferate and differentiate into different lineages of blood cells through
hematopoietic progenitor cells (HPCs). The goal of the present study is to investigate the long-term effects
of low dose proton irradiation on HSCs. In this study, we exposed C57BL/6 mice to 1.0 Gy total body proton
irradiation. The effects of proton radiation on HSCs and HPCs were studied 22 weeks after the exposure.
The results show that exposure to 1.0 Gy total body proton irradiation significantly reduced the
frequencies and numbers of HSCs in the bone marrow of irradiated mice compared to un-irradiated
controls, demonstrating that proton radiation can induce a sustained reduction in HSCs. In contrast, no
107 | P a g e
and anti-oxidant pathways, which are interlinked processes affecting intestinal cell homeostasis. Methods
and materials: Six to eight weeks old C57BL/6J mice (n=10 mice per group) were exposed to 2 Gy γ
radiation (dose rate: 0.7 Gy/min). Mice were humanely euthanized 2-month after radiation exposure, the
intestine surgically removed, and flushed using sterile buffered saline. Parts of the intestine from the
jejuno-ilial region were fixed, frozen, or used for intestinal epithelial cell (IEC) isolation. While oxidant level
and mitochondrial status was assessed in isolated cells, autophagy and oxidative stress related signaling
pathways were probed in frozen and fixed samples using PCR-based expression array,
immunohistochemistry, and immunoblots. Results: Radiation exposure caused significant alterations in
the expression level of 28 autophagy and 17 oxidative stress related genes. While 11 genes involved in
initiating and regulating autophagy pathway were downregulated, 15 genes involved in anti-oxidant
activity were downregulated after radiation. Immunoblot results showed decreased Beclin1 and LC3B and
increased PI3K/Akt and mTOR signaling. Flow cytometry data showed increased oxidant production and
compromised mitochondrial integrity in irradiated samples. Radiation exposure was associated with
increased oxidative DNA damage as well as increased nuclear PCNA staining in IEC. Conclusions: Our study
provides insight into molecular events associated with long-term perturbation of intestinal function after
exposure to ionizing radiation. Radiation-induced inhibition of autophagy and promotion of oxidative
stress could work in tandem to trigger an intestinal inflammatory response reported earlier and has
implications for functional dysbalance in the gastrointestinal tract.
(PS1-10) Exposure to 1 Gy total body proton irradiation causes long-term damage to hematopoietic
1
1
2
1
1
1
stem cells in mice. Jianhui chang ; Wei Feng ; Yingying Wang ; Yi Luo ; Antiño R Allen ; Jennifer Turner ;
1
1
2
Blair Stewart ; Jacob Raber 2;3;4 ; Daohong Zhou ; and Lijian Shao, Division of Radiation Health, Department
of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, UAMS, little rock, AR ;
1
2
Departments of Behavioral Neuroscience, ONPRC, Oregon Health and Science University, Portland, OR ;
3
Department of Neurology, Oregon Health and Science University, Portland, OR ; and Division of
Neuroscience, Oregon Health and Science University, Portland, OR
4
Exploratory missions to planets or asteroids supported by the National Aeronautics and Space
Administration (NASA) will expose astronauts certain health risks. In the space radiation environment,
protons account for more than 80% of deep-space radiation. Additionally, proton radiation has been
increasingly used in clinic to treat cancer. Therefore, there is an urgent need to better understand the
biological effects of proton radiation on the body. This knowledge will lead to a more accurate assessment
of the potential health risk of proton radiation and the development of a better strategy to prevent and
mitigate the adverse effects of proton radiation. Previous studies have shown that exposure to low doses
of proton is detrimental to mature leukocyte populations in peripheral blood but the underlying
mechanism is not known. It may be attributable to damage to hematopoietic stem cells (HSCs) that have
the ability to self-renew, proliferate and differentiate into different lineages of blood cells through
hematopoietic progenitor cells (HPCs). The goal of the present study is to investigate the long-term effects
of low dose proton irradiation on HSCs. In this study, we exposed C57BL/6 mice to 1.0 Gy total body proton
irradiation. The effects of proton radiation on HSCs and HPCs were studied 22 weeks after the exposure.
The results show that exposure to 1.0 Gy total body proton irradiation significantly reduced the
frequencies and numbers of HSCs in the bone marrow of irradiated mice compared to un-irradiated
controls, demonstrating that proton radiation can induce a sustained reduction in HSCs. In contrast, no
107 | P a g e
