Zinc affects miR-548n, SMAD4, SMAD5 expression in HepG2 hepatocyte and HEp-2 lung cell lines

MicroRNAs affect disease progression and nutrient status. miR-548n increased 57 % in Zn supplemented plasma from adolescent females (ages 9 to 13 years). The purpose of this study was to determine the effects of Zn concentration in cell culture on the expression of miR-548n, SMAD4 and SMAD5 in hepatocyte (HepG2) and lung epithelium (HEp-2) cell lines. Cells were incubated for 48 h in media containing 10 % Chelex 100-treated FBS (0 μM Zn), or with 15 or 50 μM Zn, before isolation of total RNA and cDNA. Expression of miR-548n, SMAD4 and SMAD5 was measured by qPCR. The ΔΔCT method was used to calculate the fold-change, and 15 µM expression levels were used as reference values. HepG2 miR-548n expression decreased 5-fold, and SMAD4 expression increased 4-fold in the absence of Zn, while HEp-2 miR-548n expression increased 10.5-fold, and SMAD5 expression increased 20-fold in the absence of Zn. HEp-2 miR-548n expression increased 23-fold, while SMAD4 expression decreased twofold, in 50 μM Zn-treated cells. However, SMAD4 and SMAD5 expression was not correlated. These data indicate that miR-548n expression is in part regulated by Zn in a cell-specific manner. SMAD4 and SMAD5 are genes in the TGF-β/BMP signaling pathway, and SMAD5 is a putative target for miR-548n; Zn participates in regulating this pathway through controlling SMAD4 and SMAD5 expression. However, SMAD5 expression may be more sensitive to Zn than to miR-548n since SMAD5 expression was not inversely correlated with miR-548n expression.