Role of Bcl-xL in paracetamol-induced tubular epithelial cell death

Background. Paracetamol overdose causes acute renal failure and chronic exposure to paracetamol has been linked to chronic renal failure. Recently, apoptosis induction has been identified as a possible mechanism of paracetamol nephrotoxicity. Methods. Murine proximal tubular epithelial MCT cells were cultured in the presence of paracetamol. The effects of BclxL overexpression, Bax antisense oligodeoxynucleotides, and different caspase inhibitors on cell death were studied. Results. While paracetamol did not change the mRNA expression of the antiapoptotic gene bcl-xL, it decreased Bcl-xL protein levels. The decrease in Bcl-xL was prevented by lactacystin, but not by caspase inhibitors. Addition to the culture media of the survival factors present in fetal calf serum (FCS) increased Bcl-xL expression and decreased paracetamol-induced apoptosis. Overexpression of a human bcl-xL transgene decreased apoptosis induced by paracetamol by 60% at 24 hours and increased long-term cell survival. The constitutive expression of the viral caspase inhibitor CrmA decreased the rate of apoptosis by 60% at 24 hours and the broad-specific caspase inhibitor zVAD-fmk prevented paracetamol-induced features of apoptosis. However, caspase inhibitors did not prevent eventual cell death. Bax did not translocate to mitochondria and Bax antisense oligodeoxynucleotides were not protective. Conclusion. Our results suggest that induction of apoptosis may underlie the nephrotoxic potential of paracetamol and identify Bcl-xL as a player in toxic tubular cell injury.