CELLULAR EFFECTS OF MERCURY EXPOSURE IN PROXIMAL TUBULAR CELLS

Abstract

Mercury (Hg) is a lethal and persistent contaminant that does not decompose readily in the environment. Hg, as a pollutant, is distributed globally because of its volatile nature and its ability to convert between chemical forms. Humans are exposed to various forms of Hg by ingestion, inhalation, and dermal absorption. Inorganic forms of Hg accumulate readily in the kidney and can cause significant cellular injury. The purpose of this study was to test the hypothesis that Hg has detrimental effects on cellular components and processes such as protein folding, calcium homeostasis, mitochondrial activity, and junctional complexes. To test our hypothesis, cultured proximal tubular cells (TH1 cells) were exposed to different concentrations of mercuric chloride (HgCl2), and various assays were performed to assess different cellular parameters. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was utilized to identify the specific concentrations of Hg that lead to decreases in cellular viability. Quantitative Polymerase Chain Reaction (qPCR) was used to analyze the mRNA expression of B-cell lymphoma 2 (Bcl-2) and caspase 9 to determine if Hg induces apoptosis in exposed cells. Alterations in cell permeability were detected by measuring the passage of various dextran (4kD, 10kD, and 20kD) across a cell monolayer and immunocytochemistry was used to visualize changes in occludin. In addition, the ability of two antioxidant compounds, α-lipoic acid, and oxo thiazolidine-4-carboxylic acid (OTC), to prevent Hg-induced cellular alterations was also measured. The findings from this study indicate that exposure to inorganic forms of Hg has significant effects on numerous intracellular processes, which leads to cell intoxication and death. Although additional studies are necessary for a complete understanding of the effects of Hg on cellular processes, the current data are an important start to this process.