Toxicity of dibromoacetonitrile in isolated rat colonocytes

ABSTRACT

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