Role of reactive oxygen metabolites in organophosphate-bidrin-induced renal tubular cytotoxicity

Due to low toxicity to nontarget species and rapid degradation after its ap plication, organophosphate (OP) remains a widely used class of pesticide. S uicidal or accidental overdose of OP can result in acute tubular necrosis. Experimental evidence shows little correlation between the renal tubular ne crosis and the degree of OF-induced acetylcholinesterase inhibition, the ma in mechanism of OP's toxicity, suggesting the involvement of alternate mech anisms. Since reactive oxygen species (ROS) are known mediators of many tox in-induced renal injuries, this study was conducted to investigate whether ROS play a role in Bidrin(R) (BD)-induced renal tubular epithelial cell (LL C-PK1) toxicity. ED is an OP insecticide formulation with dicrotophos as th e active ingredient. LLC-PK1 cell death, determined by lactate dehydrogenas e (LDH) release (% of total), rose concentration- and time-dependently afte r exposure of the cells to 1000, 1250, 1500, 1750, and 2000 ppm of ED for 6 , 12, 24, and 48 h. Antioxidants 2-methylaminochroman (2-MAC; 0.3 to 2.5 mu M) and desferrioxamine (DFO: 0.25 to 2 mM) reduced cell damage induced by 1250 ppm of ED over a 24-h incubation in a concentration-related manner. Th e greatest reductions in % LDH were produced by DFO 2 mM and 2-MAC 2.5 mu M , both significantly lower than ED alone. H2O2 levels (mu mol/mg protein pe r h) were significantly elevated after exposure to 1250 ppm of ED. Signific antly increased malondialdehyde formation (nmol/mg protein) compared with c ontrol was also found in ED-exposed cells indicating enhanced lipid peroxid ation. Malondialdehyde generation was significantly suppressed by 2-MAC and DFO. These results demonstrate that the organophosphate ED can cause direc t tubular cytotoxicity, and implicate, at least in part, a role for ROS and accompanying lipid peroxidation in cytotoxicity. Based on these direct in vitro findings, it is hypothesized that, besides hypotension that often acc ompanies OP intoxication, OP-induced oxidative stress at the tubular level may play a role in the pathogenesis of acute tubular necrosis.