Morphological and functional changes of microglia cultured under different oxygen concentrations and the analysis of related mechanisms

This study investigated the effects of different concentrations of oxygen exposure on the morphology and function of N9 microglia and analyzed its mechanisms. N9 microglia were cultured under the condition of high (95% O(2) and 5% CO(2)), normal (95% air and 5% CO(2)) and low oxygen (95% CO(2) and 5% O(2)) concentrations. The cell morphologies were observed under inverted phase contrast microscope after 24 h. Flow cytometry was applied to detect cell survival and apoptotic rate. The mRNA and protein expression levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis, respectively. The results showed that, N9 microglial apoptotic rates in hyperoxia and hypoxia conditions were significantly higher than those in the normal group (P<0.05) and the apoptosis rate in the hypoxia group was higher than that in the hyperoxia group (P<0.05). The mRNA and protein expression levels of IL-1β and TNF-α in the hyperoxia and hypoxia groups were significantly higher than those in the normal group (P<0.05) and the mRNA and protein expression levels in hypoxia group were higher than those in the hyperoxia group (P<0.05). Therefore, N9 microglia cultured under hyperoxia and hypoxia conditions can be activated, enhancing pro-inflammatory response and inducing cell apoptosis. The mechanism may be that the secretion of neurotoxic factors IL-1β and TNF-α is involved in these responses.