Effect of Exogenous Zinc on MsrB1 Expression and Protein Oxidation in Human Lens Epithelial Cells

Abstract

Aging has been related to zinc deficiency, resulting in protein oxidation and age-related decline of methionine sulfoxide reductase (Msr) activity. This study was designed to investigate the levels of methionine sulfoxide reductase B1 (MsrB1) mRNA and oxidized proteins in human lens epithelial (hLE) cells after treatment with exogenous zinc. The role of exogenous zinc in regulation of MsrB1 gene expression and protein oxidation in hLE cells was studied by MTT assay, oxidized protein measurement kit, and real-time PCR. The results showed that hLE cell viability was significantly decreased by MsrB1 gene knockdown or peroxynitrite (ONOO⁻) treatment, while it was significantly increased after treatment with exogenous zinc (P < 0.05). Protein carbonyl content in hLE cell by MsrB1 gene knockdown or ONOO⁻ treatment was significantly decreased after treatment with ZnSO₄ (P < 0.01). And exogenous zinc could increase the level of MsrB1 in hLE cell under normal (P < 0.001) and oxidative stress (P < 0.01) conditions. In conclusion, exogenous zinc could protect hLE cells against MsrB1 gene knockdown or ONOO⁻-induced cell death by upregulation of MsrB1 involved in the elimination of reactive oxygen species (ROS) and oxidized proteins.

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