Role of NADPH oxidase in radiation-induced pro-oxidative and pro-inflammatory pathways in mouse brain

Purpose: The present study was designed to investigate our hypothesis that NADPH oxidase plays a role in radiation-induced pro-oxidative and pro-inflammatory environments in the brain. Materials and methods: C57BL/6 mice received either fractionated whole brain irradiation or sham-irradiation. The mRNA expression levels of pro-inflammatory mediators, such as TNF-alpha and MCP-1, were determined by quantitative real-time RT-PCR. The protein expression levels of TNF-alpha, MCP-1, NOX-2 and Iba1 were detected by immunofluorescence staining. The levels of ROS were visualized by in situ DHE fluorescence staining. Results: A significant up-regulation of mRNA and protein expression levels of TNF-alpha and MCP-1 was observed in irradiated mouse brains. Additionally, immunofluorescence staining of Iba1 showed a marked increase of microglial activation in mouse brain after irradiation. Moreover, in situ DHE fluorescence staining revealed that fractionated whole brain irradiation significantly increased production of ROS. Furthermore, a significant increase in immunoreactivity of NOX-2 was detected in mouse brain after irradiation. On the contrary, an enhanced ROS generation in mouse brain after irradiation was markedly attenuated in the presence of NOX inhibitors or NOX-2 neutralizing antibody. Conclusions: These results suggest that NOX-2 may play a role in fractionated whole brain irradiation-induced pro-oxidative and pro-inflammatory pathways in mouse brain.