Arsenite exposure in human lymphoblastoid cell lines induces autophagy and coordinated induction of lysosomal genes

Chronic exposure to inorganic arsenic is associated with diverse, complex diseases, making the identification of the mechanism underlying arsenic-induced toxicity a challenge. An increasing body of literature from epidemiological and in vitro studies has demonstrated that arsenic is an immunotoxicant, but the mechanism driving arsenic-induced immunotoxicity is not well established. We have previously demonstrated that in human lymphoblastoid cell lines (LCLs), arsenic-induced cell death is strongly associated with the induction of autophagy. In this study we utilized genome-wide gene expression analysis and functional assays to characterize arsenic-induced effects in seven LCLs that were exposed to an environmentally relevant, minimally cytotoxic, concentration of arsenite (0.75 μM) over an eight-day time course. Arsenic exposure resulted in inhibition of cellular growth and induction of autophagy (measured by expansion of acidic vesicles) over the eight-day exposure duration. Gene expression analysis revealed that arsenic exposure increased global lysosomal gene expression, which was associated with increased functional activity of the lysosome protease, cathepsin D. The arsenic-induced expansion of the lysosomal compartment in LCL represents a novel target that may offer insight into the immunotoxic effects of arsenic.