Galactic Cosmic Ray Particle Exposure Does Not Increase Protein Levels of Inflammation or Oxidative Stress Markers in Rat Microglial Cells In Vitro

Abstract

Astronauts on exploratory missions will be exposed to galactic cosmic rays (GCR), which can induce neuroinflammation and oxidative stress (OS) and may increase the risk of neurodegenerative disease. As key regulators of inflammation and OS in the CNS, microglial cells may be involved in GCR-induced deficits, and therefore could be a target for neuroprotection. This study assessed the effects of exposure to helium (4He) and iron (56Fe) particles on inflammation and OS in microglia in vitro, to establish a model for testing countermeasure efficacy. Rat microglia were exposed to a single dose of 20 cGy (300 MeV/n) 4He or 2 Gy 56Fe (600 MeV/n), while the control cells were not exposed (0 cGy). Immediately following irradiation, fresh media was applied to the cells, and biomarkers of inflammation (cyclooxygenase-2 [COX-2], nitric oxide synthase [iNOS], phosphorylated IκB-α [pIκB-α], tumor necrosis factor-α [TNFα], and nitrite [NO2−]) and OS (NADPH oxidase [NOX2]) were assessed 24 h later using standard immunochemical techniques. Results showed that radiation did not increase levels of NO2− or protein levels of COX-2, iNOS, pIκB-α, TNFα, or NOX2 compared to non-irradiated control conditions in microglial cells (p > 0.05). Therefore, microglia in isolation may not be the primary cause of neuroinflammation and OS following exposures to helium or iron GCR particles.