Toxicity of Dibromoacetonitrile in Isolated Rat Colonocytes

Dibromoacetonitrile (DBAN) is a water disinfection by-product. The objective of the present work was to investigate the cytotoxic effects as well as the oxidative stress induced by DBAN in cultured rat colonocytes. Colonocytes were exposed in-vitro to different concentrations of DBAN (0.1-2.0 mM) for 60 min. Also, colonocytes were incubated with DBAN (1.0 mM) for different time intervals extending to 180 min. Cytotoxicity was determined by assessing cell viability and lactate dehydrogenase (LDH) release, glutathione (GSH) level and lipid peroxidation as indicated by thiobarbituric acid reactive substances (TBARS) production. Exposure of colonocytes to DBAN (1.0 mM) for 60 min caused nearly a 50% decrease in cell viability and induced a 3-fold increase of LDH leakage. In the same experiment, DBAN caused a significant decrease in cellular GSH content as well as a significant enhancement of TBARS accumulation. These toxic responses to DBAN were dependent on both concentration and duration of exposure to DBAN. Treatment of colonocytes with GSH, N-acetyl-L-cysteine (NAC) or dithiothreitol (DTT) prior to exposure to DBAN afforded different degrees of protection as indicated by significant decrease in the LDH leakage and TBARS formation as compared to DBAN alone-treated cells. Also, pretreatment of colonocytes with the antioxidant enzymes superoxide dismutase (SOD) or catalase (CAT) significantly inhibited LDH leakage and TBARS production. Preincuhation with dimethyl sulfoxide (DMSO), a hydroxyl radical scavenger or desferroxiamine (DFO), an iron chelator, diminished DBAN-induced LDH leakage and TBARS generation. Our results suggest that DBAN 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 DBAN-induced colonotoxicity.