OBJECTIVETo study the effect of SOD2 and its C47T mutation on oxidative injury in cochlea hair cells.

METHODSHEI-OC1 cells were transfected with the SOD2 of Ala16 and Vla16. Cells' proliferation ability was determined by MTT assay. The intracellular SOD2 activities were detected by xanthine oxidase method. Intracellular ROS were determined by DCFH-DA after exposure to 100 µmol/L t-BHP and the early apoptotic and necrotic rate or late apoptotic rate were quantified by flow cytometry (FCM) using Annexin V/PI double staining.

RESULTSMTT method showed the transfection of SOD2 gene and empty plasmid did not affect the proliferation capacity. SOD2 vitality in Ala(16) and Val(16) SOD2 transfected cells increased 2.51 and 2.71 times respectively (P < 0.01), but the difference between the two transfection groups was not statistically significant (P > 0.05). After exposed to t-BHP, the majority of the untransfected and empty plasmid transfected cells sent '++' class bright fluorescence, while in Ala(16) and Val(16) SOD2 transfected groups, only about half cells sent '±' ∼ '+' level fuzzy fluorescence. determination of FCM suggested the early apoptotic and necrotic rate or late apoptotic rate decreased after SOD2 transfection (P < 0.01), but the difference between the two genotypes of SOD2 was not statistically significant (P > 0.05).

CONCLUSIONHigh expression of SOD2 below 3.71 times can reduce intracellular ROS level in HEI-OC1 cells, while SOD2 C47T mutation had no effect on them. SOD2 can be considered as NIHL susceptibility gene and its rs4880 SNP may be not directly related to NIHL genetic susceptibility.