The role of STIM1 in the Cr(vi)-induced [Ca2+]i increase and cell injury in L-02 hepatocytes.

Hexavalent chromium [Cr(vi)] is a potent cytotoxin and carcinogen. In recent years, drinking water contamination with Cr(vi) has become a worldwide problem of significant public health importance, thus much attention has been paid to the investigation of Cr(vi)-induced hepatotoxicity. The concentration of intracellular calcium ions ([Ca2+]i) was found to be increased after Cr(vi) exposure, but the exact underlying mechanisms involved in the Ca2+ homeostasis imbalance remain poorly characterized. In the present study, by utilizing the antagonist of store-operated calcium channels (SOCCs) 2-aminoethoxydiphenyl borate (2-APB), small interfering RNA against stromal interaction molecule 1 (si-STIM1) and antioxidant N-acetylcysteine (NAC), we found that Cr(vi) induces [Ca2+]i increase, cell viability loss and transaminase (AST/ALT) leakage, and that these could be suppressed by both 2-APB and si-STIM1. NAC significantly alleviated Cr(vi)-induced up-regulation of STIM1, phosphorylated-extracellular-signal-regulated kinases 1 and 2 (p-ERK1/2), ERK1/2 and nuclear factor κB (NF-κB). By utilizing the ERK inhibitor U0126 and the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC), we confirmed that STIM1 can be regulated by ERK and NF-κB. Thus we concluded that STIM1 plays a role in the Cr(vi)-induced [Ca2+]i increase and cell injury. Our current data provide new insights into the mechanisms of STIM1 function in Cr(vi)-induced hepatotoxicity, and may provide experimental clues for the prevention and treatment of liver diseases in the occupational population exposed to Cr(vi).