BACKGROUND:Intervertebral disc degeneration is one of the most common underlying factors causing low back pain.Recent studies have shown that melatonin has a positive effect on alleviating intervertebral disc degeneration.However,the underlying mechanism of melatonin remains to be elucidated. OBJECTIVE:To explore the biological effect and potential mechanism of melatonin in inhibiting hydrogen peroxide(H2O2)-induced injury of human nucleus pulposus cells. METHODS:Human nucleus pulposus cells insolated from degenerative intervertebral disc were cultured in vitro.Cell proliferation and the optimal intervention concentration of melatonin and H2O2 were detected by cell counting kit-8.The Human nucleus pulposus cells treated with H2O2 were used as a model group;the cells treated with H2O2 and intervened with melatonin were used as a melatonin group;the cells cultured in simple medium were used as a control group.The reactive oxygen species levels were detected by 2',7'-dichlorofluorescin diacetate(DCFH-DA),the expression levels of BAX and Caspase3 were detected by immunofluorescence,and the mRNA expression levels of BAX,BCL-2,Casepase3,PI3K and AKT were detected using the real-time fluorescent quantitative reverse transcription PCR. RESULTS AND CONCLUSION:The results of cell counting kit-8 experiment showed that the optimal intervention concentration of H2O2 was 400 μmol/L and the optimal intervention concentration of melatonin was 5 μmol/L.The reactive oxygen species level in the melatonin group was significantly lower than that in the model group.The average fluorescence intensity of BAX and Caspase3 in the melatonin group was significantly lower than that in the model group.The mRNA expressions of BAX and Caspase3 in the melatonin group were lower than those in the model group,while the mRNA expression of Bcl-2 was increased.In addition,the mRNA expressions of PI3K and AKT were also higher in the melatonin group compared with the model group.To conclude,melatonin may protect human nucleus pulposus cells from H2O2-induced oxidative damage through the PI3K/AKT signaling pathway.