| Summary: | 碩士 === 國立清華大學 === 生命科學系 === 90 === Metallothioneins (MTs) are a group of low molecular weight proteins which rich in cystein residues, and induced markedly by metal ions. In addition, oxidative stress was also a factor to induce the MT gene expression. Previous reports have been demonstrated that cadmium was able to induce the gene expression of metallothionein (MT), but the underlying mechanisms were not well understood. In this study, we used the catalase inhibitor, 3-amino-1, 2, 4-triazole (3-AT), to investigate the effects of cadmium on the gene expression of MT in human hepatoma cell lines (HepG2). First, we found that 3-AT significantly suppressed the gene expression of MT induced by cadmium or zinc using the Northern blot. 3-AT inhibited the gene expression of MT was a dose-dependent manner. Another catalase inhibitor, salicylic acid, also suppressed the gene expression of MT and shown a dose-dependent manner. Second, we tested the effects of 3-AT and salicylic acid on the intracellular level of cadmium in cadmium treatment cells. The results shown that salicylic acid significantly decreased the intracellular level of cadimium in dose-dependent manner. Low dose of 3-AT (10 mM) significantly decreased the intracellular level of cadmium, however, high dose of 3-AT (80 mM) slightly decreased the intracellular level of cadmium. Third, we found that high concentration of 3-AT (80 mM) significantly decreased the proliferation rate and viability in cadmium treatment cells. Low concentration of 3-AT or cadmium alone exhibited no significant effect in the inhibition of cell proliferation and viability. Furthermore, cotreatment of hydrogen peroxide and cadmium was not able to enhance the gene expression of MT compare with cadmium alone. These results suggested that induction of MT gene expression by cadmium might not mediate the generation of oxidative stress. It is possible that 3-AT decreased the cadmium into the cells and resulted in low intracellular level of cadmium and MT expression.
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