Cocaine N-demethylation and the metabolism-related hepatotoxicity can be prevented by cytochrome P450 3A inhibitors (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.
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.
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
Alcoholism: Clinical and Experimental Research, 1991
Chronic ethanol consumption potentiates cocaine-induced liver injury in rodents. Since cocaine has to be bioactivated by a cytochrome P-450-dependent N-oxidative pathway to exert its hepatotoxic effects, we studied the role of the ethanol-inducible P-45011E1 for cocaine metabolism. Male Sprague-Dawley rats were pretreated with either a liquid diet containing ethanol (30% of calories) for 4 weeks or injected with pyrazole (200 mg/kg/day, ip, for 3 days). Both agents induced microsomal p-nitrophenol hydroxylation which is a probe for the catalytic activity of P-45011El. However, only ethanol, but not pyrazole, increased both microsomal cocaine N-demethylase activity (by 47%) and the extent of irreversible binding of [3H]-cocaine to microeomal proteins (by lOO%), which was taken as a quantitative endpoint for the formation of a reactive metabolite. Cocaine Ndemethylation and irreversible protein binding of cocaine were not inhibited by P-45011E1 isozyme-selective substrates, nor was the rate of cocaine metabolism and binding decreased by functionally active polyclonal anti-rat P-45011E1 antibodies. Furthermore, pyrazole pretreatment sensitized cultured hepatocytes to the glutathione-dependent cytotoxic effects of nontoxic concentrations of cocaine. These results indicate that (a) cocaine is not a major substrate for the ethanol-inducible P-45011E1, (b) the enhancing effects of ethanol on cocaine bioactivation may be due to induction of other P-450 isoforms, and (c) induction of P-45011E1 may potentiate cocaineinduced hepatocellular toxicity in vitro independently of cocaine metabolism, e.g., by P-45011E 1-dependent oxidative stress.
International Journal of Measurement Technologies and Instrumentation Engineering
The effects that chronic cocaine administration (CCA) have on craving, cocaine metabolite concentrations and cytochrome P450 3A4 isoenzyme (CYP450 3A4) activities in Sprague-Dawley rats following the administration of Salako Nutritional Supplements (SNS) were examined. Five groups of fifty rats were used to assess the effect of the SNS following CCA. Craving was analyzed for each rat using a Conditioned Place Preference protocol. Blood samples were obtained at regular intervals and used to measure cocaine plasma metabolite levels. CYP450 3A4 activity was determined in the liver. Administration of the SNS reduced craving of cocaine significantly, upon discontinuing cocaine in the rats. Blood plasma analysis showing higher benzoylecgonine equilibrium and the CYP450 3A4 levels demonstrated that the SNS possibly aided in the removal of the stored metabolites indicative of increased metabolism of cocaine, enhanced by the Supplements. Results indicate that the SNS formulation reduces crav...
2014
Dimethocaine (DMC), a synthetic derivative of cocaine, is distributed and consumed as "new psychoactive substance" (NPS) without any safety testing at the forefront. It is mainly metabolized by N-acetylation, N-deethylation or hydroxylation. Therefore, the aim of the presented study was to determine the human NAT and P450 isozymes involved in this major metabolic steps, to measure the kinetics of the reactions, and to estimate the contribution on in vivo hepatic clearance. For these studies, cDNA-expressed NATs and P450s were used and formation of metabolites after incubation was measured using LC-MS or LC-MS(n). For N-acetylation, NAT2 could be shown to be the only isoform catalyzing the reaction in vitro hence assuming to be the only relevant enzyme for in vivo acetylation. Kinetic profiles of all P450 catalyzed metabolite formations followed classic Michaelis-Menten behavior with enzyme affinities (Km values) between 3.6 and 220 μM. Using the relative activity factor approach, the net clearances for deethylation of DMC were calculated to be 3% for P450 1A2, 1% for 2C19, <1% for 2D6, and 96% for 3A4. The net clearances for hydroxylation of DMC were calculated to be 32% for P450 1A2, 5% for 2C19, 51% for 2D6, and 12% for 3A4. Furthermore, these data were confirmed by chemical inhibition tests in human liver microsomes. As DMC is metabolized via two main steps and different P450 isoforms were involved in the hepatic clearance of DMC, a clinically relevant interaction with single P450 inhibitors should not be expected. However, a slow acetylation phenotype or inhibition of NAT2 could lead to decreased N-acetylation and hence leading to an increased risk of side effects caused by this arylamine.
Forensic Toxicology, 2008
6β-hydroxylase (CYP3A), pentoxyresorufi n O-dealkylase (CYP2B1), ethoxyresorufi n O-deethylase (CYP1A1), and methoxyresorufi n O-demethylase (CYP1A2) activities were increased 2-6 fold in both PB-pretreated and BNF-pretreated rat liver microsomes sampled at 24 h after MDMA administration as compared with the control values. These results suggest that PB-induced and BNF-induced CYP enzymes have inhibitory effects on N-demethylation of MDMA to MDA in vivo in rats. If HHMA is the precursor of HMMA in rats, there is a possibility that the O-demethylenation of MDMA to HHMA is increased by the induced CYP enzymes. The decreased urinary concentration of MDMA and very low percent recoveries of MDA, HMMA, and (4-hydroxy-3-methoxyphenyl)acetone (HMPA) in the inducer-pretreated groups suggest that other metabolic pathways of MDMA exist and are activated under the present experimental conditions.
Toxicology, 2003
Drug-metabolizing enzymes play a great role in the bioactivation and also detoxification of zenobiotics and carcinogens such as N -nitrosamines and polycyclic aromatic hydrocarbons (PAHs). Therefore, the present study was undertaken to investigate the effect of narcotic drugs such as cannabis (hashish) and diacetylmorphine (heroin) on the activity of N -nitrosodimethylamine N -demethylase I [NDMA-dI], arylhydrocarbon [benzo(a)pyerne] hydroxylase [AHH], cytochrome P450 (CYP), cytochrome b 5 , NADPH-cytochrome c reductase, glutathione-S -transferase, and levels of glutathione and thiobarbituric acid-reactive substances (TBARS). In addition, the present study showed the influence of hashish and heroin after single (24 h) and repeated-dose treatments (4 consecutive days) on the expression of cytochrome P450 2E1 (CYP 2E1) and cytochrome P450 2C6 (CYP 2C6). The expression of CYP 2E1 was slightly induced after single-dose and markedly induced after repeated dose-treatments of mice with hashish (10 mg kg (1 body weight). Contrarily, heroin markedly induced the expression of CYP 2C6 after single-dose and potentially reduced this expression after repeated-dose treatments. It is believed that N -nitrosamines are activated principally by CYP 2E1 and in support of this, the activity of NDMA-dI was found to be increased after single-and repeated-dose treatments of mice with hashish by 23 and 41%, respectively. In addition, single-and repeated-dose treatments of mice with hashish increased: (1) the total hepatic content of CYP by 112 and 206%, respectively; (2) AHH activity by 110 and 165%, respectively; (3) NADPH Á/cytochrome c reductase activity by 21 and 98%, respectively; (4) and glutathione level by 81 and 173%, respectively. Also, single-dose treatments of mice with heroin increased the total hepatic content of CYP, AHH, NADPH Á/cytochrome c reductase, and glutathione level by 126, 72, 39, 205%, respectively. However, repeated dose-treatments of mice with heroin did not change such activities except cytochrome c reductase activity increased by 20%. Interestingly, the level of free radicals, TBARS, was potentially decreased after single or repeated-dose treatments with either hashish or heroin. It is clear from this study that the effects of hashish are different from those of heroin on the above mentioned enzymes particularly after repeated dose treatments. It is concluded that hashish induced the expression of CYP 2E1 and other carcinogen-metabolizing enzymes activities, and this induction could potentiate the deleterious effects of N -nitrosamines and aromatic hydrocarbons, e.g. benzo(a)pyrene, upon the liver and probably * Present address: