Hyperbaric Oxygen Preconditioning Induces Tolerance against Oxidative Injury and Oxygen-Glucose Deprivation by Up-Regulating Heat Shock Protein 32 in Rat Spinal Neurons

Objective: Hyperbaric oxygen (HBO) preconditioning (HBO-PC) has been testified to have protective effects on spinal cord injury (SCI). However, the mechanisms remain enigmatic. The present study aimed to explore the effects of HBO-PC on primary rat spinal neurons against oxidative injury and oxygen-glucose deprivation (OGD) and the relationship with heat shock proteins (HSPs). Methods: Primary rat spinal neurons after 7 days of culture were used in this study. HSPs were detected in rat spinal neurons following a single exposure to HBO at different time points by Western blot. Using lactate dehydrogenase release assay and cell counting kit-8 assay, the injuries induced by hydrogen peroxide (H2O2) insult or OGD were determined and compared among neurons treated with HBO-PC with or without HSP inhibitors. Results: The results of Western blot showed that HSP27, HSP70 and HSP90 have a slight but not significant increase in primary neurons following HBO exposure. However, HSP32 expression significantly increased and reached highest at 12 h following HBO exposure. HBO-PC significantly increased the cell viability and decreased the medium lactate dehydrogenase content in cultures treated with H2O2 or OGD. Pretreatment with zinc protoporphyrin IX, a specific inhibitor of HSP32, significantly blocked the protective effects of HBO-PC. Conclusions: These results suggest that HBO-PC could protect rat spinal neurons in vitro against oxidative injury and OGD mostly by up-regulating of HSP32 expression.