Reactive species and apoptosis of neural precursor cells after γ-irradiation

This study addresses the participation of radiation-induced free radicals, mainly nitric oxide (NO), in modulating the apoptotic response in an in vitro model of neural cortical precursor cells exposed to γ-radiation. Cortical cells obtained from rats at 17 gestational day (GD) were irradiated with a dose of 2 Gy. The percentage of apoptotic cells was significantly increased 4 h post-irradiation (pi). NO content showed a significant increase after 30 min pi and the rate of generation reached a maximum 1 h pi. Luminol-dependent chemiluminescence (CL) was significantly higher in cells after 2 h pi as compared to control cells and this profile was maintained up to 4 h pi. Supplementation with l-NAME significantly increased light emission. Administration of superoxide dismutase (SOD) following l-NAME addition prevented the observed changes due to l-NAME administration. The caspase inhibitor zDEVD-fmk significantly reduced the radical generation. Moreover, the cellular decrease in NO content occurred coincidentally with the rise in oxygen radical generation and the activation of caspase-3. In vitro irradiation of neural precursor cells allowed us to suggest that an early radiation-induced generation of NO could exert a neuroprotective role. However, despite this NO initial protective effect and its role modulating the response against γ-radiation, NO generation was not able of fully preventing radiation-induced apoptosis.