The Effect of MMC on Chick Lens and its Mechanism

ABSTRACT

Mitomycin C (MMC)is used in trabeculectomy to promote the intraocular pressure control, but at the same time it also seems to increase the risk of cataract. In this study, we investigated the mechanism by which MMC causes lens opacity.The whole lenses were extracted from fertilized eggs of 11~13 days and cultured in M199 media supplemented with fetal bovine serum (FBS)at 38 degrees C.Levels of Lipid peroxidation (LPO)and Glutathione (GSH)were measured 24 hours and 5 minutes after treatment with 1 mg/ml MMC for 5 minutes.Changes of lenses by MMC were examined by light microscopy, and the modification of lens proteins was analyzed by SDS-PAGE and size exclusion column. Lens opacity was induced by MMC treatment in concentration of 1 mg/ml for 5 min, and MMC treated lenses showed 3 times higher LPO level and 2 times lower GSH level than normal lenses.In ultrastructure of opaque lenses, many vacuole formations in cortical area near equatorial zone were found.In electrophoresis followed by silver staining and size exclusion column profile, high molecular weight formation of lens proteins by MMC treatment was mainly due to disulfide bond.Also, when we treated the lens with antioxidants, the extent of opacity was decreased. In this study, we demonstrated that lenses treated with MMC became opaque mainly due to oxidative stress resulting in HMW formation of lens proteins by disulfide formation as well as irreversible oxidation.