Ethanol-Induced Enhancement of Cocaine Bioactivation and Irreversible Protein Binding: Evidence Against a Role of Cytochrome P-450IIE1 (original) (raw)
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Modification of hepatic cytochrome P450 profile by cocaine-induced hepatotoxicity in DBA/2 mouse
European Journal of Pharmacology: Environmental Toxicology and Pharmacology, 1994
Previous studics in our laboratory have shown that a hepatotoxic dose of cocaine increases coumarin 7-hydroxylase activity in male DBA/2 mouse liver. In the present study, the dose-and time-dependent responses of the hepatic CYP2A4/5 complex to cocaine-induced liver damage were studicd. Cocaine increased CYP2A4/5 levels in a dose-dependent manner. The maximal increases in coumarin 7-hydroxylasc activity (4-fold), microsomal CYP2A4/5 content (3-fold) and steady-state mRNA levels (10-fold) were observed at 24 h after administration of a single dose of 60 mg/kg cocaine coinciding with morphologically detectable diffuse liver damage, while the total P450 content was not changed. 3 and 5 days after the daily administration of cocaine severe, mainly pericentral (zone III of Rappaport), liver damage was apparent in parallel with a clear decline in CYP2A4/5 mRNA, protein content and coumarin 7-hydroxylase activity. After 5 days of treatment, CYP2A5 still remained at a very low level but an induction in CYP2B10 protein and related pentoxyresorufin O-dealkylase activity was observed. No marked changes in microsomal CYP2Cx and CYP1A1/2 contents or associated activities were observed. Dimethylnitrosamine N-demethylase activity, a marker for CYP2E1, decreased in parallel with increased cocaine dose and time and the severity of liver damage. Our results demonstrate that (i) administration of cocaine causes a clear but transient increase in the expression of Cyp2a-4/5 gene complex prior to overt liver damage and (ii) microsomal CYP2B10 and related 7-pentoxyresorufin O-dealkylase activity is markedly increased in animals treated for 5 days with cocaine concomitantly with the decrease in other monooxygenases indicating an'association of coumarin 7-hydroxylase activity with liver injury and different roles for coumarin 7-hydroxylase and 7-pentoxyresorufin O-dealkylase activities in cocaine hepatotoxicity.
Potentiation of cocaine hepatotoxicity in human hepatocytes by ethanol
Toxicology in Vitro, 1992
The cytotoxic effect of cocaine on human hepatocytes was evaluated after 24 hr of exposure to cocaine by measuring the leakage of intracellular lactate dehydrogenase and the reduction of MTT. According to these endpoint parameters, the half-maximal cytotoxic concentration (ICs0) of cocaine was 6.8 and 7.8 mM, respectively. Lower concentrations of cocaine, however, impaired basic metabolic functions of human hepatocytes. Exposure of cells to 2 mM-cocaine resulted in a 500 decrease in hepatic glycogen, a 40% decrease in cellular glutathione content and a 40% decrease in urea synthesis with respect to control values. Ethanol greatly potentiated cocaine-induced hepatotoxicity. After a 48-hr pretreatment of human hepatocytes with 50 raM-ethanol, concentrations of cocaine (0.25 mM) that had no effects on hepatocyte metabolism in the absence of ethanol, caused a 20°/, inhibition of the urea synthesis rate, a 40% depletion of glycogen stores and a 30% reduction in glutathione content. The results of our work show that ethanol significantly increases the toxic effects of cocaine on human hepatocytes.
European Journal of Pharmacology: Environmental Toxicology and Pharmacology, 1994
Cocaine is eliminated and detoxified principally through the metabolism of nonspecific plasma and tissue esterases. Microsomal oxidative metabolism is of importance in cocaine N-demethylation, this being a principal pathway of cocaine bioactivation and hepatotoxicity. The contribution of different cytochrome P450 (CYP) enzymes to cocaine N-demethylase activity was studied in vitro with DBA/2 mouse and human liver microsomes, and cocaine hepatotoxicity was examined in vivo in DBA/2 male mice. Species dependent enzyme kinetics was observed. Cocaine N-demethylase displayed two K m values in murine liver (40-60 #M and 2-3 raM), whereas only one K m value was observed in human liver microsomes (2.3-2.7 raM). We suggest that CYP3A plays a prominent role in the N-demethylation of cocaine for the following reasons: (i) pregnenolone-16acarbonitrile, an inducer of CYP3As increases cocaine N-demethylase in parallel with testosterone 6/3-hydroxylase activity and immunoreactive 3A protein in mouse liver; (ii) human and mouse cocaine N-demethylase and testosterone 6/3-hydroxylase activities can be inhibited by triacetyloleandomycin, cannabidiol, or gestodene, all selective inhibitors of CYP3A P450s; (iii) antibodies directed against P450s within subfamilies 1A, 2A, 2B, 2C, or 2E inhibited cocaine N-demethylase activity only marginally, and fnally, (iv) treatment of mice with triacetyloleandomycin or cannabidiol in vivo significantly attenuated the cocaine-elicited hepatotoxicity as assessed by the serum alanine aminotransferase activity and liver histology in parallel with decreased cocaine N-demethylase activity. The present results demonstrate that the first step of cocaine bioactivation is catalyzed by the CYP3A enzyme(s) in both murine and human liver microsomes and cocaine-induced liver injury in mice may be prevented by the administration of the CYP3A inhibitors.
Hepatology, 1996
2B10, although markedly increased by cocaine treat-The effects of daily cocaine administration for up to ment, has only a minor role in cocaine hepatotoxicity; 14 days were studied in terms of hepatic morphology and (3) despite increased microsomal CNDM activity, coand the expression of cytochrome P450 (CYP) enzymes caine-induced liver injury is reversible in mice. (HEPAin the mouse liver. Daily intraperitoneal doses of 60 mg/ TOLOGY 1996;23:515-523.) kg of cocaine for 3 days induced severe hepatocellular necrosis in the pericentral zone and decreased activities of CYP1A2, CYP2A4/5, and CYP2Cx. The microsomal Cocaine, one of the oldest drugs of abuse, is a natu-CYP2B10 protein content was increased by about 2.5fold, but 2B10-dependent 7-pentoxyresorufin O-dealky-rally occurring plant product found in the leaves of lase (PROD) activity was barely detectable. Five or Erythroxylon coca. In the United States during 1989 seven daily cocaine doses caused prominent pericentral and 1990 cocaine ranked first in both total drug abuse inflammation and a significant (up to 14-fold) increase episodes and in drug-related deaths. 1 The toxicity of in the microsomal protein content and PROD activity. cocaine includes myocardial infarcts, cardiac arrhyth-An increase in microsomal CYP3A was also evident, but mias, and hemorrhage. Psychiatric complications such CYP2A5 and CYP1A2 still remained at a low level. Immuas acute anxiety or panic and paranoid psychosis have nohistochemical examination showed that the relative also been reported. 1,2 induction of CYP2B10 and CYP3A after treatment with One of the most striking toxic effects of cocaine is its cocaine was strongest in perivenous hepatocytes. Immuhepatotoxicity. Cocaine-induced liver injury has been noinhibition experiments showed that CYP2B10 accounted for catalysis of only 15% to 20% of the enhanced documented both in laboratory animals 3,4 and humicrosomal cocaine N-demethylase (CNDM) activity, mans. 5,6 There are marked species differences in the which correlated well with immunoreactive 3A protein, hepatotoxic potency of cocaine, 7 the mouse being the and could be blocked 70% to 90% by triacetyloleandomymost susceptible. cin. After 10 or 14 daily doses of cocaine, regenerative
Hepatic Morphologic and Biochemical Changes Induced by Subacute Cocaine Administration in Mice
Toxicologic Pathology, 1992
The initial event and site of cocaine-induced hepatic injury have not been elucidated. In an attempt to identify the minimal effective dose and the site of injury, we have examined the livers of mice exposed to small daily doses of cocaine, using morphological and biochemical methods. All doses of cocaine greater than 5 mg/kg were able to cause significant elevation of serum glutamic pyruvic transaminase. Light microscopy revealed a progression of centrilobular necrosis as the dose increased from 10-30 mg/kg. The initial morphologic changes observed prior to necrosis included aggregation of intermediate filaments and dilation of rough endoplasmic reticulum with loss of ribosomes. Immunohistochemistry, using antibodies to cytokeratins, showed staining of individual hepatocytes in livers from cocaine-treated animals but not in controls. In contrast to earlier reports, we found little, if any, disruption of mitochondria. In vitro, the direct application of cocaine, norcocaine, and N-hy...
Cocaine mutagenicity and hepatocarcinogenicity evaluations in rodents
Teratogenesis, Carcinogenesis, and Mutagenesis, 1998
The mutagenicity (clastogenicity) and the carcinogenicity (promoting potential) of cocaine were evaluated, respectively, by the mouse bone marrow micronucleus test (study I) and by the initiated rat liver bioassay (study II). In study I, two administration routes (i.p. and i.v.) and two sampling times (24 and 48 hours) after cocaine treatment were studied. Swiss male mice were treated with cocaine at doses of 0, 18, 37, and 75 mg/kg and 0, 2, 4, and 8 mg/kg by i.p. and i.v. routes, respectively. No significant differences were observed between treated and negative control groups regarding the frequencies of micronuclei and the polichromatic/normochromatic erythrocyte (PCE/NCE) ratios. In study II, the development of putative preneoplastic foci of hepatocytes expressing the enzyme glutathione S-transferase placental form (GST-P +) was utilized as the end-point marker in a 8-week rat liver bioassay. The animals were initiated for carcinogenesis by a single i.p. sub-carcinogenic dose of diethylnitrosamine (DEN). After a 6-week exposure to 5 or 10 mg/kg of cocaine i.v. twice a week there was no enhancement of GST-P + foci development above the values of the control DEN-only treated animals. Also, cocaine did not induce any toxicity as evidenced by the absence of alterations of rat body and liver weights and of liver biochemical function and morphology. The results suggest that cocaine does not have a mutagenic effect on the mouse bone marrow cells or promoting activity on the rat hepatocarcinogenesis process.
Drug and Alcohol Dependence, 2000
The purpose of this study was to investigate possible mechanism of cocaine-induced hepatotoxicity and its potentiation by ethanol in mice. Ethanol (2 g/kg) and/or cocaine (25 mg/kg) injections were given as binge model (five injections in 3 days). Cocaine administration with or without ethanol caused an increase in lipid peroxidation in liver homogenate and its subcellular fractions. The greatest increases were observed in mitochondrial fraction following cocaine plus ethanol treatment. Also, glutathione (GSH) levels were increased in liver homogenate and its mitochondrial fractions after cocaine and cocaine plus ethanol treatment. Microsomal calcium sequestration was found to decrease in all treatments. These results suggest that increased lipid peroxidation and decreased microsomal calcium sequestration in the liver may play a possible role cocaine-induced hepatotoxicity and its potentiation by ethanol.
Liver damage from cocaine in mice
Life sciences, 1977
Four daily injections of 20 mg per kg cocaine hydrochloride into B6AF 1/J mice produced focal necrosis of liver parenchymal cells in the midzonal region. Massive liver damage and marked elevation of serum glutamic-oxaloacetic transaminase was observed ...
The role of CYP enzymes in cocaine-induced liver damage
Archives of Toxicology, 1995
Cocaine is hepatotoxic in several species, including man. A high dose of cocaine produces metabolismdependent, mainly pericentral, liver damage. At 24h after a single dose of cocaine, mouse hepatic P450 content decreases but CYP2A activities; coumarin 7-hydroxylase and testosterone 15α-hydroxylase increase concomitant with prominent diffuse cell necrosis. Repeated adminision of cocaine for up to 5 days decreases CYP1A1/2, 2A4/5, 2Cx, and 2E1 related enzymatic activities. However, after five doses of cocaine, CYP2B10 increases in conjunction with the healing process. In the acute phase, the increased CYP2A activities do not participate in cocaine bioactivation. CYP3A enzymes are principally responsible for the cocaine N-demethylation in human and mouse liver microsomes. The hepatic metabolic CYP enzyme profile will change during prolonged cocaine intake, this being accompanied by altered cell morphology. Possible connections to cocaine toxicity in man are discussed.