Cocaine hepatotoxicity: two different toxicity mechanisms for phenobarbital-induced and non-induced rat hepatocytes.
Hepatocytes isolated from both phenobarbital-induced and control rats were short-term cultured and exposed to cocaine (8-2000 microM) for varying times. Intracellular lactate dehydrogenase activity, free calcium levels ([Ca2+]i), reduced glutathione (GSH) and lipid peroxidation were investigated to evaluate the toxic effect of cocaine on hepatocytes. Cytochrome P450 induction by phenobarbital potentiated the in vitro cytotoxicity of cocaine by a factor of 13 (IC50 = 84 microM in induced cells vs 1100 microM in non-induced cells). This difference in the susceptibility of the two types of hepatocytes to cocaine correlated well with the activity of cytochrome P450 2B1/2. Rapid depletion of GSH, reaching 30% of the control levels, and massive lipid peroxidation thereafter were the two most remarkable phenomena preceding cell death in phenobarbital-induced hepatocytes. On the other hand, a sustained rise in [Ca2+]i starting 2 hr after incubation with cocaine was the most noteworthy finding in non-induced liver cells. We suggest two different pathways for cocaine hepatotoxicity: in phenobarbital-induced hepatocytes oxidative metabolism of the drug causes GSH depletion, subsequent extensive lipid peroxidation and cell death, at low concentrations of cocaine. In non-induced hepatocytes these changes are less relevant, and the major alteration caused by cocaine is a non-transient rise in [Ca2+]i that is evident at higher concentrations of the drug.
Jover
R
R
Unidad de Hepatología Experimental, Hospital Universitario La Fe, SVS/University of Valencia, Spain.
Ponsoda
X
X
Gómez-Lechón
J
J
Castell
J V
JV
D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D003042:Cocaine / Q000633:toxicity*; D019362:Cytochrome P-450 CYP2B1; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010088:Oxidoreductases / Q000378:metabolism; D010634:Phenobarbital; D051381:Rats; D017207:Rats, Sprague-Dawley
D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019362:Cytochrome P-450 CYP2B1; D005978:Glutathione; D003042:Cocaine; D002118:Calcium; D010634:Phenobarbital