The effects of heavy ion and X-ray exposure on SH-SY5Y cell differentiation

Kurzfassung

Background: Exposure to ionizing radiation (IR) has increased in the last century. One field where radiation is omnipresent and little is known regarding its effects on human health is spaceflight. With scheduled long-duration missions (LDM) to the Moon and Mars, there has been a push to investigate radiation hazards for various organs and tissues, including the central nervous system (CNS). IR may not only contribute to the increased incidence of neurodegenerative disorders, but also hamper neurogenesis, contributing to cognitive impairment and emotional instability during spaceflight. The aim of this study was to investigate the effects of ¹²C ion and X-ray exposure on neuroblastoma cell differentiation. Methods: SH-SY5Y cells were irradiated with ¹²C ions or X-rays. Neuronal differentiation was induced by incubation with retinoic acid (RA) and different concentrations of fetal bovine serum (FBS). The effects of radiation/differentiation on growth, cell-cycle distribution, morphology changes and presence of neuronal markers was assessed by cell count, flow cytometry, phase-contrast and fluorescence microscopy. Results: Stem-like and differentiated cells exposed to X-rays at 4Gy exhibited the lowest total/live cell numbers (p<0.01; p<0.001, respectively) and viability, and the highest fraction of dead cells, also comprising the largest sizes (p<0.01). RA inhibited growth (p<0.05), with no significant differences in other parameters. Cell cycle distribution was similar between conditions, however with increased G1-phase cells in RA-treated conditions and decreased S-phase cells in irradiated conditions (p<0.001). Morphological and immunohistochemical analysis indicated robust neurite outgrowth with intense BIII-tubulin in RA-differentiated cells. Irradiated cells lost their adherence phenotype and displayed balanced ratios of Nestin:BIII-tubulin, compared to the predominantly Nestin-positive control. Conclusion: ¹²C ions and X-rays irradiation did not induce differentiation of stem-like cells nor inhibit differentiation of surviving cells treated with RA.