Cytotoxic effects of psychoactive isobutyrylfentanyl and its halogenated derivatives on isolated rat hepatocytes

The novel and numerous psychoactive compounds derived from the analgesic prescription drug N-phenyl-N-[1-(2-phenylethyl)piperidin-4-yl]propanamide (fentanyl) have been illegally abused as recreational drugs and caused numerous fatalities. Because some psychoactive/psychotropic drugs are known to be hepatotoxic in humans and experimental animals, the cytotoxic effects and mechanisms of 4-fluoroisobutyrylfentanyl (4F-iBF), 4-chloroisobutyrylfentanyl (4Cl-iBF), and the parent compound isobutyrylfentanyl (iBF) were studied in freshly isolated rat hepatocytes. 4F-iBF caused not only concentration (0-2.0 mM)- and time (0-3 h)-dependent cell death accompanied by the depletion of cellular ATP and reduced glutathione (GSH) and protein thiol levels but also the accumulation of oxidized glutathione. Of these fentanyls examined, 4Cl-iBF/4F-iBF-induced cytotoxicity with the loss of mitochondrial membrane potential at concentrations of 0.5 and 1.0 mM and the production of reactive oxygen species (ROS) at 0.5 mM were greater than those induced by iBF. The pretreatment of hepatocytes with N-acetyl-l-cysteine as a precursor of cellular GSH ameliorated, at least in part, cytotoxicity accompanied by insufficient ATP levels, the loss of mitochondrial membrane potential, and generation of ROS caused by 4Cl-iBF/4F-iBF, whereas pretreatment with diethyl maleate as a GSH depletor enhanced fentanyl-induced cytotoxicity accompanied by the rapid loss of cellular GSH. Taken collectively, these results indicate that the onset of cytotoxic effects caused by these fentanyls is partially attributable to cellular energy stress as well as oxidative stress.