Effects of oxidative stress-induced increases in Zn 2+ concentrations in human gingival epithelial cells

Previous studies have reported that oxidative stress increases intracellular Zn concentrations and induces cytotoxicity. However, no studies have investigated whether oxidative stress induces such changes in periodontal tissue cells. In the present study, we investigated the effect of oxidative stress on intracellular Zn concentration in periodontium constituent cells and its potential relationship with periodontal disease. We analyzed changes in intracellular Zn concentrations in human gingival epithelial (epi4) cells treated with hydrogen peroxide (H O ). The fluorescent probes FluoZin-3 AM and CellTracker Green CMFDA were used to detect intracellular Zn and thiol groups, respectively. Western blot analyses, luciferase reporter assays, and real-time polymerase chain reaction (PCR) analyses were performed to examine the effect of intracellular Zn on epi4 cells. H O treatment increased intracellular concentrations of Zn in epi4 cells by facilitating the movement of Zn from cellular nonprotein thiols to the cytoplasm and promoting cell membrane permeability to Zn . Furthermore, H O -induced increases in intracellular Zn activated the p38 cAMP response element-binding protein/mitogen-activated protein kinase (p38 CREB/MAPK) cascade, upregulated nuclear factor kappa B (NF-κB) DNA binding, and increased the expression of inflammatory cytokines and matrix metallopeptidase-9 (MMP-9). Increases in intracellular Zn induced by oxidative stress activate signaling pathways involved in inflammation, potentially contributing to the progression of periodontal disease.