The Tibetan medicine Zuotai differs from HgCl2 and MeHg in producing liver injury in mice

Zuotai is composed mainly of β-HgS, while cinnabar mainly contains α-HgS. Both forms of HgS are used in traditional medicines and their safety is of concern. This study aimed to compare the hepatotoxicity potential of Zuotai and α-HgS with mercury chloride (HgCl2) and methylmercury (MeHg) in mice. Mice were orally administrated with Zuotai (30 mg/kg), α-HgS (HgS, 30 mg/kg), HgCl2 (33.6 mg/kg), or CH3HgCl (3.1 mg/kg) for 7 days, and liver injury and gene expressions related to toxicity, inflammation and Nrf2 were examined. Animal body weights were decreased by HgCl2 and to a less extent by MeHg. HgCl2 and MeHg produced spotted hepatocyte swelling and inflammation, while such lesions are mild in Zuotai and HgS-treated mice. Liver Hg contents reached 45–70 ng/mg in HgCl2 and MeHg groups; but only 1–2 ng/mg in Zuotai and HgS groups. HgCl2 and MeHg increased the expression of liver injury biomarker genes metallothionein-1 (MT-1) and heme oxygenase-1 (HO-1); the inflammation biomarkers early growth response gene (Egr1), glutathione S-transferase (Gst-mu), chemokine (mKC) and microphage inflammatory protein (MIP-2), while these changes were insignificant in Zuotai and HgS groups. However, all mercury compounds were able to increase the Nrf2 pathway genes NAD(P)H:quinone oxidoreductase 1 (Nqo1) and Glutamate-cysteine ligase, catalytic subunit (Gclc). In conclusion, the Tibetan medicine Zuotai and HgS are less hepatotoxic than HgCl2 and MeHg, and differ from HgCl2 and MeHg in hepatic Hg accumulation and toxicological responses.