Acrylonitrile-induced toxicity and oxidative stress in isolated rat colonocytes

Acrylonitrile (ACN), an environmental toxic pollutant, has been detected in drinking water, food products and occupational environment. The objective of the present work was to investigate the cytotoxic effects as well as the oxidative stress induced by ACN in cultured rat colonocytes. Colonocytes were exposed in vitro to different concentrations of ACN (0.1-2.0mM) for 60min. Also, colonocytes were incubated with ACN (1.0mM) for different time intervals extending to 180min. Cytotoxicity was determined by assessing cell viability and lactate dehydrogenase (LDH) release. Oxidative stress was assessed by determining reduced glutathione (GSH) level and lipid peroxidation as indicated by thiobarbituric acid reactive substances (TBARS) production. Exposure of colonocytes to ACN (1.0mM) for 60min caused nearly a 50% decrease in cell viability and induced a 2.5-fold increase of LDH leakage. In the same experiment, ACN caused a significant decrease in cellular GSH content as well as a significant enhancement of TBARS accumulation. These toxic responses to ACN were dependent on both concentration and duration of exposure to ACN. There was a good correlation between LDH release and TBARS formation (r(2)=0.97, p<0.05). Treatment of colonocytes with GSH, N-acetyl-l-cysteine (NAC) or dithiothreitol (DDT) prior to exposure to ACN afforded different degrees of protection as indicated by significant decrease in the LDH leakage and TBARS formation as compared to ACN alone-treated cells. Also, pretreatment of colonocytes with the antioxidant enzyme superoxide dismutase (SOD) or catalase (CAT) significantly inhibited LDH leakage and TBARS production. Preincubation with dimethyl sulfoxide (DMSO), a hydroxyl radical scavenger or desferroxiamine (DFO), an iron chelator, diminished ACN-induced LDH leakage and TBARS generation. Our results suggest that ACN has a potential cytotoxic effect in rat colonocytes; and thiol group-donors, antioxidant enzymes, hydroxyl radical scavengers and iron chelators can play an important role against ACN-induced colonotoxicity.