HYDROGEN PEROXIDE-INDUCED EXPRESSION OF THE PROTOONCOGENES, C-JUN, C-FOS AND C-MYC IN RABBIT LENS EPITHELIAL-CELLS

The involvement of H2O2 in cataract development has been established i n both human patients and animal models. At the molecular level H2O2 h as been observed to cause damage to DNA, protein and lipid. To explore the oxidative stress response of the lens system at the gene expressi on level, we have examined the effects of H2O2 on the mRNA change of t he protooncogenes, c-jun, c-fos and c-myc in a rabbit lens cell line, N/N1003A. H2O2 treatment of the rabbit lens epithelial cells for 60 mi n induces quick up-regulation of both c-jun and c-fos mRNAs. The maxim al induction is 38 fold for c-jun at 150 mu M and 72 fold for c-fos at 250 mu M H2O2. Treatment of N/N1003A cells with 50-250 mu M H2O2 for 60 min leads to a 2-5 fold increase of the c-myc mRNA level. H2O2 also induces an up-regulation in transactivity of the activating protein-1 (AP-1) as shown with a reporter gene driven by a prolactin gene promo ter with 4 copies of AP-1 binding sites inserted in the upstream of th e promoter. Maximal induction occurs with 150 mu M H2O2. In the same s ystem, the antioxidants, N-acetyl-cysteine (NAC) and pyrrolidine dithi ocarbamate (PDTC) at concentrations shown to up-regulate the mRNAs of both c-jun and c-fos, also enhance the transactivity of AP-1. NAC and PDTC have different effects in modulating the induction of AP-1 activi ty by H2O2 and TPA. These results reveal that oxidative stress regulat es expression of various regulatory genes in lens systems, which likel y affects cell proliferation, differentiation and viability and thus a ffect normal lens functions.