Studies on mercuric sulfide, a component of cinnabar, a Chinese herbal medicine, on celluar functions in mouse lung and fibroblasts

Although the cytotoxic effects of mercuric chloride (HgCl2) and methylmercury chloride (MeHg) have been extensively studied, the insoluble mercuric sulfide (HgS) has been the subject of fewer studies. Since the traditional Chinese mineral drug, cinnabar (containing >95% HgS) continues to be used as an ingredient for infant sedation, the pharmacological and toxicological effects of HgS need to be clarified. In previous experiments, HgS and cinnabar were shown to be absorbed from the gastrointestinal tract (GIT) and distributed in various tissues including the lungs. Thus, a preliminarily examination of whether HgS might exert any oxidative stress on a mouse lung was undertaken. HgS reduced GSH content and increased lipid peroxidation in the lung. Further studies on the cytotoxic effects and the possible mechanisms of action of HgS were compared with HgCl2 and MeHg in cultured lung fibroblast V79 cells. The results showed that HgS produced cytotoxicity at a concentration (400-1200 μM)in a dependent manner with IC50 of 795.6 μM, as compared to HgCl2 and MeHg, 8.1 μM and 5.9 μM, respectively. In addition, the HgS induced the phenomena of DNA fragmentation, increasing reactive oxygen species (ROS) and decreasing mitochondrial membrane potential, accompanied by decreased levels of intracellular ATP and GSH and higher lipid peroxidation levels, similar to HgCl2 and MeHg, but with different toxicokinetic properties. These findings provide evidence for understanding the mechanisms underlying the toxic effects of HgS.