Toxicity of arsenic on isolated human lymphocytes: The key role of cytokines and intracellular calcium enhancement in arsenic-induced cell death

Abstract Arsenic (As) is a semi-metal which causes health problems in human, and immune system has been documented as one of the main target of arsenic toxicity. Apoptosis has a crucial role in regulation of immune system, but it can also have an important role in As immune suppression. So, we decided to assess the comprehensive mechanism of As cytotoxic effect on lymphocytes isolated from human blood. We determine the direct effect of arsenic on human lymphocytes which have a key role in immune system functionality. To evaluate the mechanism of arsenic toxicity on human lymphocytes, we use accelerated cytotoxicity mechanisms screening (ACMS) technique. Lymphocytes were isolated from blood of healthy persons using Ficoll-paque PLUS standard method. Following treatment of human lymphocytes with 0.05-50 μM of arsenic for 12 h, cell viability was measured. For determination of mechanistic parameters, isolated human lymphocytes incubated with 1/2IC5012h (7.5 μM), IC5012h (15 μM) and 2IC5012h (30 μM) for 2, 4 and 6 h. The results of this study demonstrate arsenic-associated apoptosis in human lymphocytes is mainly through enhancement of intracellular calcium which causes oxidative stress and following adverse effect on lymphocytes organelles (like mitochondria and lysosome). Involvement of cellular proteolysis, activation of caspase-3, lipid peroxidation and stimulation of cytokines (IL2, INF-gamma and TNF-alpha) production were also associated with arsenic induced lymphocyte toxicity.