title: Persistent oxidative stress in human neural stem cells exposed to low fluences of charged particles.
abstract: Exposure to the space radiation environment poses risks for a range of deleterious health effects due to the unique types of radiation encountered. Galactic cosmic rays are comprised of a spectrum of highly energetic nuclei that deposit densely ionizing tracks of damage along the particle trajectory. These tracks are distinct from those generated by the more sparsely ionizing terrestrial radiations, and define the geometric distribution of the complex cellular damage that results when charged particles traverse the tissues of the body. The exquisite radiosensitivity of multipotent neural stem and progenitor cells found within the neurogenic regions of the brain predispose the central nervous system to elevated risks for radiation induced sequelae. Here we show that human neural stem cells (hNSC) exposed to different charged particles at space relevant fluences exhibit significant and persistent oxidative stress. Radiation induced oxidative stress was found to be most dependent on total dose rather than on the linear energy transfer of the incident particle. The use of redox sensitive fluorogenic dyes possessing relative specificity for hydroxyl radicals, peroxynitrite, nitric oxide (NO) and mitochondrial superoxide confirmed that most irradiation paradigms elevated reactive oxygen and nitrogen species (ROS and RNS, respectively) in hNSC over a 1 week interval following exposure. Nitric oxide synthase (NOS) was not the major source of elevated nitric oxides, as the use of NOS inhibitors had little effect on NO dependent fluorescence. Our data provide extensive evidence for the capability of low doses of charged particles to elicit marked changes in the metabolic profile of irradiated hNSC. Radiation induced changes in redox state may render the brain more susceptible to the development of neurocognitive deficits that could affect an astronaut's ability to perform complex tasks during extended missions in deep space.
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA.
authors: Janet E
authors: JE
authors: Baulch
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA.
authors: Brianna M
authors: BM
authors: Craver
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA.
authors: Katherine K
authors: KK
authors: Tran
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA.
authors: Liping
authors: L
authors: Yu
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA.
authors: Nicole
authors: N
authors: Chmielewski
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA.
authors: Barrett D
authors: BD
authors: Allen
authors: Department of Radiation Oncology, University of California, Irvine, CA 92697-2695, USA. Electronic address: climoli@uci.edu.
authors: Charles L
authors: CL
authors: Limoli
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D017665:Hydroxyl Radical / Q000378:metabolism; D018499:Linear Energy Transfer; D058953:Neural Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D018384:Oxidative Stress / Q000528:radiation effects*; D030421:Peroxynitrous Acid / Q000378:metabolism; D011839:Radiation, Ionizing; D013481:Superoxides / Q000378:metabolism
chemical_list: D013481:Superoxides; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D017665:Hydroxyl Radical; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase
keywords: Charged particle; Human neural stem cells; Oxidative stress; Space radiation