Zinc Chloride: Time-Dependent Cytotoxicity, Proliferation and Promotion of Glycoprotein Synthesis and Antioxidant Gene Expression in Human Keratinocytes

SIMPLE SUMMARY: Zinc ions are involved in the biology of cell growth, proliferation, differentiation or apoptosis by regulating many biological molecules, such as transcription factors, enzymes and growth factors. In this study, the time-dependent cytotoxicity, cell proliferation and gene expression in human keratinocytes HaCaT cells were evaluated when exposed to ZnCl(2). The results of this study showed non-cytotoxic effects up to 10 µg/mL after 24 h, no significant effect on cell proliferation when exposed to 5 or 1 µg/mL ZnCl(2) at 72 h and upregulation of eight genes, with great potential in the biomedical field, particularly for regenerative-medicine applications and wound healing. ABSTRACT: The use of ionic metals such as zinc (Zn(2+)) is providing promising results in regenerative medicine. In this study, human keratinocytes (HaCaT cells) were treated with different concentrations of zinc chloride (ZnCl(2)), ranging from 1 to 800 µg/mL, for 3, 12 and 24 h. The results showed a time–concentration dependence with three non-cytotoxic concentrations (10, 5 and 1 µg/mL) and a median effective concentration value of 13.5 µg/mL at a cell exposure to ZnCl(2) of 24 h. However, the zinc treatment with 5 or 1 µg/mL had no effect on cell proliferation in HaCaT cells in relation to the control sample at 72 h. The effects of the Zn(2+) treatment on the expression of several genes related to glycoprotein synthesis, oxidative stress, proliferation and differentiation were assessed at the two lowest non-cytotoxic concentrations after 24 h of treatment. Out of 13 analyzed genes (superoxide dismutase 1 (SOD1), catalase (CAT), matrix metallopeptidase 1 (MMP1), transforming growth factor beta 1 (TGFB1), glutathione peroxidase 1 (GPX1), fibronectin 1 (FN1), hyaluronan synthase 2 (HAS2), laminin subunit beta 1 (LAMB1), lumican (LUM), cadherin 1 (CDH1), collagen type IV alpha (COL4A1), fibrillin (FBN) and versican (VCAN)), Zn(2+) was able to upregulate SOD1, CAT, TGFB1, GPX1, LUM, CDH1, FBN and VCAN, with relative expression levels of at least 1.9-fold with respect to controls. We found that ZnCl(2) promoted glycoprotein synthesis and antioxidant gene expression, thus confirming its great potential in biomedicine.