AIM:To investigate the protective effects of naringin(Nar)phospholipid complex(NPC)on oxidative injury in retinal pigment epithelium cells(ARPE-19 cells)induced by tert-butyl hydroperoxide(t-BHP)and elucidate the underlying mechanism.

METHODS:The NPC was prepared by solvent method. Experimental cells are divided into seven groups: control group \〖cultured with dimethylsulfoxide(DMSO)\〗, model group(intervention with 200μmol/L t-BHP), nuclear factor erythroid 2-related factor 2(Nrf2)-siRNA group(cell transfection for Nrf2 gene), naringin group(add 200μmol/L t-BHP after pretreatment with 200μmol/L naringin medium), NPC group(add 200μmol/L t-BHP after pretreatment with 200μmol/L NPC medium), Nrf2-siRNA+ naringin group(after 200μmol/L naringin pretreatment, Nrf2 gene interference, then add 200μmol/L t-BHP)and Nrf2-siRNA+ NPC group(after 200μmol/L NPC pretreatment, Nrf2 gene interference, then add 200μmol/L t-BHP). The intracellular levels of superoxide dismutase(SOD), malondialdehyde(MDA)and total antioxidant capacity(T-AOC)were detected, intracellular level of reactive oxygen species(ROS)was detected by DCFH-DA staining method. The mRNA and protein expressions of HO-1, NQO-1, GCL and Nrf2 were detected by real-time PCR and western blot, respectively.

RESULTS:NPC more significantly increased the levels of SOD and T-AOC, reduced the contents of ROS and MDA than naringin in t-BHP-treated ARPE-19 cells. After naringin and NPC pre-protected ARPE-19 cells, the relative expression and protein expression of Nrf2, HO-1, NQO-1 and GCL mRNA were higher than those of the model group and Nrf2-siRNA group. There were statistically significant differences in the relative expression of 4 genes and the expression levels of 4 proteins in the naringin group and the NPC group, the Nrf2-siRNA+naringin group and the Nrf2-siRNA+NPC group. The expression of Nrf2, HO-1 and NQO-1 protein in the Nrf2-siRNA+naringin group was not significantly different than that in the Nrf2-siRNA group. Compared with the Nrf2-siRNA group, the expression of 4 proteins in the Nrf2-siRNA+NPC group was statistically significant, and the effect of NPC was significantly stronger than that of naringin.

CONCLUSION: After naringin forms a phospholipid complex, it can significantly increase the antioxidant capacity in cells and reduce the oxidation level. It up-regulates the expression of Nrf2 and its downstream antioxidant enzymes and phase Ⅱ detoxification enzymes by activating the Nrf2/ARE antioxidative stress pathway to better protect ARPE-19 cells from oxidative damage.