Comparative study on toxicity of methylmercury chloride and methylmercury hydroxide to the human neuroblastoma cell line SH-SY5Y.

Toxicities of methylmercury chloride (CH3HgCl) and methylmercury hydroxide (CH3HgOH) to cultured neuroblastoma cell line SH-SY5Y in vitro are evaluated. This is the comparative study between two methylmercury compounds to find out the extent of toxicity of these compounds are toxic to SH-SY5Y cell line. Both cytotoxicity and genotoxicity experiments were carried out to find out the more toxic compound. For cytotoxicity study, four staining assay methods independently with trypan blue (TB), acridine orange/ethidium bromide (AO/EB), 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT), and neutral red (NR) were used and the comet assay method was done for genotoxicity study. The obtained toxicity data were used for probit analysis. In cytotoxicity, CH3HgCl had minimum inhibitory concentration (MIC) value in each assay method as 3 mg/L invariably; LC25 values were in the range 7.41 to 10.23 mg/L, and LC50 values were 14.79 to 15.48 mg/L; while LC75 values were 20.89 to 26.91 mg/L. Moreover, LC100 value was 30 mg/L, known from comet assay experiments for CH3HgCl. Similarly for CH3HgOH, the MIC value in each assay method was invariably 3 mg/L, the LC25 values were in the range 12.58 to 16.59 mg/L, and LC50 values were 19.49 to 23.44 mg/L; LC75 values were 27.54 to 30.90 mg/L and LC100 value was 42 mg/L in each assay done for cytotoxicity and genotoxicity studies. Computed DNA fragmentation indices in comet assays were 98.6 ± 0.57 30 mg/L with CH3HgCl and 76 ± 5.29 30 mg/L with CH3HgOH. This study clearly indicated that methylmercury chloride is more toxic than methylmercury hydroxide to SH-SY5Y cell line. Toxicity of Hg had been quantified with in vitro cultured human neuroblastoma cell line; since it has neurotoxic effects, its neural evaluation has implications in environmental health issues.