Study On The Oxidation-Induced Tissue Damage And The Anti-Oxidation Mechanistic Of NAD~+-Dependent Enzyme CD38 And NAD

By down-regulating oxidative stress,NAD is able to reduce the tissue damage in rodent testes caused by synchrotron radiation（SR）X-ray,decrease the doxorubicin-induced liver damage of mice and H₂O₂-induced cell damage.Therefore,to better understand the mechanism of tissue damage and find methods and targets for tissue protection,the study on the role of NAD and NAD-related enzymes in oxidative stress and anti-oxidation is required.First of all,we find that synchrotron radiation（SR）X-ray induces a CD38 increase in rodent testes by oxidative stress,which indicates that NAD plays an important role in oxidative stress-induced tissue damage.We further studied the mechanism of NAD-induced increase in anti-oxidation capacity by using differentiated PC12 cells.The results suggested that by increasing nuclear Nrf2,NADH leads to increase in GCL and glutathione.Also,NADH induces glutathione increase in primary cultured astrocytes and rotenone-treated cells,which indicates that NADH treatment can increase glutathione in Parkinson’s disease.Moreover,our results indicate that NAD+and NADPH oxidase have no effect on the NADH-induced glutathione increase.Pharmacological inhibition and siRNA silencing of SIRT2,but not inhibition of SIRT1,prevent NADH-induced increases in nuclear Nrf2,GCL expression and glutathione synthesis.SIRT2 inhibition and siRNA silencing prevent NADH-induced Akt phosphorylation.Also,specific inhibition of PI3K/Akt pathway prevents NADH-induced increases in nuclear Nrf2 and glutathione synthesis.Our results also show that SIRT2 protein level isn’t changed by NADH treatment.NADH can also increase catalase activity through SIRT2,which indicates that NADH may have an effect on other anti-oxidation pathways.Taken together,our study suggested a potential pathway for NAD-induced tissue protection:by increasing Akt activity,SIRT2 mediates NADH-induced increases in Nrf2/GCL pathway,leading to increasing in total glutathione level.