Effect of zinc on gene expression in osteoblastic MC3T3-E1 cells: enhancement of Runx2, OPG, and regucalcin mRNA expressions

The effect of zinc sulfate on the mRNA expressions in Runx2, osteocalcin, α1(I) collagen, insulin-like growth factor-I (IGF-I), transforming growth factor-β1 (TGF-β1), osteoprotegerin (OPG), regucalcin, zinc transporter 1 (ZIP1), or glyceroaldehyde-3-phosphate dehydrogenase (G3PDH) in osteoblastic MC3T3-E1 cells in vitro was investigated. Cells with subconfluency were cultured for 48 h in a medium containing either vehicle or zinc sulfate (10⁻⁶-10⁻⁴ M) without fetal bovine serum. Culture with zinc sulfate (10⁻⁵ M) caused a significant increase in Runx2, OPG, or regucalcin mRNA expressions in the cells, while it did not have a significant effect on osteocalcin, α1(I) collagen, IGF-I, TGF-β1, ZIP1, or G3PDH mRNA expressions. The effect of zinc sulfate (10⁻⁴ M) in increasing Runx2 mRNA expression was seen at 24-72 h after culture. A significant increase in OPG mRNA expression was observed at 24 or 48 h after culture. Regucalcin mRNA expression was significantly increased at 48 or 72 h after culture with zinc sulfate (10⁻⁴ M). The stimulatory effects of zinc sulfate on Runx2, OPG, or regucalcin mRNAs were significantly prevented in the presence of cycloheximide (10⁻⁷ M), an inhibitor of protein synthesis, or 5,6-dichloro-1-β-d-ribofuranosyl-benzimidazole (10⁻⁶ M), an inhibitor of transcription activity. Culture with β-alanyl-l-histidinato zinc (10⁻⁵ M) caused a significant increase in Runx2 or regucalcin mRNA expressions, while zinc acexamate (10⁻⁵ M) did not have a significant effect on Runx2, OPG, ZIP1, or regucalcin mRNA expressions. This study demonstrates that zinc sulfate has a role in the enhancement of Runx2, OPG, or regucalcin mRNA expression in osteoblastic cells in vitro, suggesting its role in the regulation of gene expression in the cells.