Thymol, a monoterpene phenolic derivative of cymene, abrogates mercury-induced oxidative stress resultant cytotoxicity and genotoxicity in hepatocarcinoma cells

Thymol (TOH) was investigated for its ability to protect against mercuric chloride (HgCl2 )-induced cytotoxicity and genotoxicity using human hepatocarcinoma (HepG2) cell line. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay confirmed the efficacy of TOH pretreatment in attenuating HgCl2 -induced cytotoxicity. Pretreatment with TOH inhibited HgCl2 -induced genotoxicity, depolarization of mitochondrial membrane, oxidative stress, and mitochondrial superoxide levels. Interestingly, TOH (100 µM) alone elevated the intracellular basal glutathione S-transferase (GST) levels and TOH pretreatment abrogated the decrease in glutathione, GST, superoxide dismutase, and catalase levels even after HgCl2 intoxication. Furthermore, TOH was also capable of inhibiting HgCl2 -induced apoptotic as well as necrotic cell death analyzed by flowcytometric analysis of cells dual stained with Annexin-FITC/propidium iodide. The present findings clearly indicate the cytoprotective potential of TOH against HgCl2 -induced toxicity, which may be attributed to its free radical scavenging ability which facilitated in reducing oxidative stress and mitochondrial damage thereby inhibiting cell death.