Histopathology of cocaine hepatotoxicity. Report of four patients

Effect of alcohol and/or cocaine on blood glutathione and the ultrastructure of the liver of pregnant CF-1 mice

Alcohol and cocaine are abused by the general population as well as by pregnant women. Since alcohol and cocaine are hepatotoxic, pregnant mice were used to study the effect of alcohol and/or cocaine on alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and on liver ultrastructure. Also, blood glutathione (GSH) and GSH related enzymes such as glutathione reductase (GSH-Rx) and glutathione peroxidase (GSH-Px) were studied. The mice were treated with 0.6 g/kg ethanol twice daily via gavage and/or 20 mg/kg of cocaine hydrochloride intravenously once daily. The treatment was from day 6 to 15 of gestation and these studies were performed at day 18. Our results indicated a significant increase in AST level after treatment with ethanol alone or in combination with cocaine. The blood GSH levels decreased significantly in all the treated groups compared to the control. The activity of GSH-Px was significantly decreased only in the ethanol and cocaine combination group compared to the control. Histopathological studies indicated that co-administration of ethanol and cocaine lead to a significant potentiation in liver toxicity as indicated by increased fatty infiltration.

Ethanol does not increase the hepatotoxicity of cocaine in primary rat hepatocyte culture

Rat hepatocytes were utilized to investigate the role of cocaine metabolism and the contribution of ethylcocaine formation to cocaine-induced liver damage. Hepatocytes were prepared from rats pretreated with saline, phenobarbital or ethanol and exposed to cocaine, ethanol, or their combination. Hepatotoxicity was assessed by lactate dehydrogenase (LDH) leakage and was correlated with cocaine metabolism which was assessed quantitatively using HPLC. Only phenobarbital-pretreatment produced increases in LDH leakage from cultures exposed to cocaine. This increase in LDH release occurred simultaneous to a decrease in benzoylecognine formation and a marked increase in norcocaine generation. Exposing cultures to ethanol alone did not result in LDH leakage from hepatocytes. Furthermore, including ethanol in cultures treated with cocaine did not enhance the LDH leakage produced by cocaine alone. This study confirms quantitatively that cocaine-induced hepatotoxicity is mediated through cocaine oxidative events and is enhanced by microsomal induction produced by phenobarbital. The finding that ethylcocaine formation was maximal in the ethanol-pretreatment group where no toxicity was observed suggests that ethylcocaine is not the agent responsible for the hepatotoxicity observed in this study.

Effect of cytochrome P450 inducers on cocaine-mediated hepatotoxicity

The effect of several cytochrome P450 (P450) inducers on cocaine metabolism were examined in order to characterize the metabolic events contributing to cocaine-induced hepatotoxicity. Phenobarbital (PB)-pretreatment of mice induced P450s 3A and 2B and markedly increased serum alanine aminotransferase (ALT) activity after cocaine or norcocaine administration. Although dexamethasone (Dex) induced P450s 3A and 2B at least to the same extent as PB, no increase in serum ALT activity was observed after cocaine or norcocaine administration. Phencyclidine (PCP) pretreatment did not increase either P450s 3A or 2B, yet it markedly enhanced cocaine- or norcocaine-induced serum ALT activity. In contrast to the marked induction of P450s 3A and 2B, P450 2C was increased only 2.5-fold by PB and to an even lesser extent by Dex or PCP. Cannabidiol (CBD), which inactivates P450s 3A and 2C in mice, completely protected mice against cocaine- or norcocaine-induced hepatotoxicity irrespective of whether they were induced or not with PB or PCP. Both PB and Dex pretreatment increased the in vitro hepatic microsomal formation of the first two sequential oxidative metabolites of cocaine (norcocaine and N-hydroxynorcocaine), whereas PCP pretreatment did not. Hepatic esterase activity was also determined after pretreatment with P450 inducers, since this is the major detoxification pathway in cocaine metabolism. Dex pretreatment markedly increased (> 11-fold) total hepatic esterase activity, whereas PB pretreatment increased it more modestly (less than fourfold) and PCP pretreatment had little effect. This marked effect of Dex pretreatment may decrease liver cocaine concentrations and thus protect mice against cocaine-induced hepatotoxicity, despite their increased P450 2B and 3A contents.

Liver disease due to illicit substance use

While the adverse neurological, cardiovascular, renal, haematologic and musculoskeletal consequences of the use of various illicit substances are widely appreciated, less attention has been directed to possible hepatotoxic effects. This is an important issue in view of increasing evidence in both experimental animals and humans that the use of some illicit substances may be associated with substantial liver damage, leading on occasion to acute liver failure. This manuscript reviews the effects on the liver of some of the most commonly used illicit substances, including ecstasy (3,4-methylenedioxymethamphetamine), other amphetamines, cocaine, heroin, angel dust (phencyclidine), lysergic acid diethylamide and marijuana. Additional causes of liver damage in those using illicit substances are discussed.

Cocaine: pathophysiology and clinical toxicology

PURPOSE

To review the medical complications of cocaine abuse and the mechanisms of action of cocaine that contribute to medical complications.

DATA SOURCES

Pertinent articles identified through a MEDLINE search of the English-language literature from 1985 to 1996 and through a manual search of bibliographies of all identified articles.

STUDY SELECTION

All articles describing complications of cocaine use including case reports, small reported series, and review articles.

DATA SYNTHESIS

A qualitative description of reported complications.

RESULTS

Since the introduction of freebase and crack cocaine, multiple medical complications have been observed, and all major body organ systems have been affected. Cocaine can cause acute strokes, myocardial infarction, cardiac dysrhythmias, pulmonary edema, rhabdomyolysis, and acute renal failure.

CONCLUSION

Adverse reactions to cocaine should be considered in the differential diagnosis of acute ischemic events that occur in young adults. General awareness of the significant complications of cocaine will facilitate early diagnosis and prompt treatment.

Cocaine-induced liver injury in mice is mediated by nitric oxide and reactive oxygen species

The modulating effects of nitric oxide (NO) and reactive oxygen species on cocaine-induced hepatotoxicity were examined by measuring plasma alanine aminotransferase activity and by carrying out histological studies. Liver injury was induced by a single injection of cocaine in adult male ICR mice. Pretreatment with aminoguanidine (an inhibitor of NO synthase), N-methyl-D-glucamine dithiocarbamate complex with iron ion (II) (Fe2+(MGD)2, a trapping reagent of NO) or deferoxamine complex with iron ion (III) (Fe3+-deferoxamine, a scavenger of NO) produced a marked inhibition of the hepatotoxicity induced by cocaine. In addition, pretreatment with allopurinol (an inhibitor of xanthine oxidase) and 1,3-dimethylthiourea (a scavenger of hydroxyl radical) also produced a potent inhibition. These findings suggest that a hydroxyl radical produced by the reaction of NO and superoxide anion (O2-) via peroxynitrite may be involved in the pathogenesis of cocaine hepatotoxicity.

Developmental immunotoxicity of cocaine and ethanol in postnatal Lewis rats

The immunomodulatory effect of cocaine (COC), ethanol (EtOH) and their combination was investigated in the developing immune system of postnatal Lewis rats. To simulate the route of exposure during lactation, newborn rats were orally treated with either saline, 20 mg COC/kg, and 0.6 g EtOH/kg or the coadministration of COC and EtOH from day 1 to 21 of life. Rat pups were sacrificed thirty minutes following the last treatment. Total lymphocytes and spleen/body weight ratios were decreased in animals exposed to COC. These immunotoxic effects were not enhanced by the coadministration of EtOH. However, pups exposed to both drugs had significantly decreased levels of serum immunoglobulin M (IgM) when compared to saline-treated rats. Plasma and tissue distribution studies revealed that the combination treatment group had a higher COC content in the brain and spleen as well as an increase in the metabolites benzoylecognine (BE) and norcocaine (NC) in the spleen. Ethylcocaine (EC) formation was not demonstrated in this model.

Impairment of mitochondrial respiration and electron transport chain enzymes during cocaine-induced hepatic injury

Morphological and biochemical changes in mitochondrial have been reported early in the course of cocaine-induced hepatotoxicity. This study was designed to examine the effects of repeated cocaine exposure in vivo on mitochondrial respiration, activities of respiratory chain enzymes, and lipid peroxide measures in liver. Male Sprague-Dawley rats were exposed to cocaine (5 i.p. injections of 25 mg/kg; 3-day period). Blood and liver samples were taken, and hepatic mitochondria were isolated by differential centrifugation. The cocaine-treated rats developed oxidative stress in hepatic mitochondria as evidenced by a significant increase in malonaldialdehyde (MDA; 52%; p < 0.0001) and a decreased glutathione (GSH; 22%; p < 0.0003). Blood aspartate aminotransferase (AST) and glutathione s-transferase (GST) levels in cocaine groups were significantly elevated (2.6 and 3.2 fold, respectively; p < 0.0001 for both). Cocaine caused a decrease in state-3 respiration and respiratory control ratio (RCR) ratio when exposed to site I and II substrates; these changes were parallelled by a decrease in complex I (22%; p < 0.003), succinate cytochrome c reductase (27%; p < 0.004), and complex IV (24%; p < 0.003). In conclusion, functional abnormalities of hepatic mitochondria accompany lipid peroxidation caused by cocaine, supporting the hypothesis that the mitochondria is one of the major intracellular targets of cocaine hepatotoxicity.

Evaluation of abnormal liver function tests

Although the liver can be affected in a wide range of disorders, the differential diagnosis of abnormal liver function tests can be substantially narrowed by a comprehensive history and physical examination and by the recognition of relatively distinct biochemical patterns of liver injury. Although referral to a specialist may be required for the performance of, for example, percutaneous liver biopsy and long-term management of chronic liver disease, a presumptive diagnosis can usually be made in the vast majority of patients who present to primary care physicians with abnormal liver function tests.

The role of CYP enzymes in cocaine-induced liver damage

Cocaine is hepatotoxic in several species, including man. A high dose of cocaine produces metabolism-dependent, mainly pericentral, liver damage. At 24 h after a single dose of cocaine, mouse hepatic P450 content decreases but CYP2A activities; coumarin 7-hydroxylase and testosterone 15 alpha-hydroxylase increase concomitant with prominent diffuse cell necrosis. Repeated administration 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.

Modification of hepatic cytochrome P450 profile by cocaine-induced hepatotoxicity in DBA/2 mouse

Previous studies 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 studied. Cocaine increased CYP2A4/5 levels in a dose-dependent manner. The maximal increases in coumarin 7-hydroxylase 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatotoxicity is not increased in alcoholics with positive urinary cocaine metabolites

Cocaine hepatotoxicity in mice has been reported by numerous investigators. Such hepatotoxicity in other animal models has been more difficult to produce. We prospectively assessed 1212 alcoholics admitted for detoxification for historical, clinical and laboratory evidence of concomitant cocaine/crack use and evidence of liver disease. The 470 cocaine positive subjects had both longer durations and higher average daily costs of cocaine/crack use than the 742 cocaine negative subjects, but had a shorter duration of alcohol use. Serum transaminases were higher in the cocaine negative group. There were no clinically severe cases of liver disease or rhabdomyolysis in either group. Serum hepatitis B surface antibody and hepatitis A antibody were more frequent in the cocaine positive subjects. In conclusion, in this large sample of alcoholics abusing cocaine, severe hepatotoxicity was not at all evident. The previous reports of hepatotoxicity may represent co-morbidity. Some possibilities include infection with a hepatitis or other virus, the presence of an adulterant, an idiosyncratic reaction or an enzymatic abnormality.

Dissociation of covalent protein adduct formation from oxidative injury in cultured hepatocytes exposed to cocaine

1. The relationship between the oxidative and the alkylating properties of cocaine was investigated in primary cultures of hepatocytes derived from phenobarbital-pretreated rats. 2. The cytotoxic effects (LDH release) of 300 microM cocaine were preceded by depletion of intracellular glutathione (GSH) and concomitant increases of oxidized glutathione (GSSG). Furthermore, exposure to [3H]-cocaine was associated with the formation of covalent protein adducts which plateaued between 2 and 7 h and which remained stable for at least 24 h. 3. The addition of the thiol-reducing agent dithiothreitol (DTT, 0.5 mM) protected against cocaine-induced LDH release without altering the time course and extent of cocaine covalent protein adduct formation. Similarly, when DTT was added after short-term exposure to cocaine in Krebs-Henseleit buffer, the loss of viability could be prevented, indicating that alterations in the thiol redox equilibrium, and not covalent protein adduct formation per se, may be crucial for the development of hepatocyte injury. In contrast, high concentrations (2.5-5.0 mM) of DTT inhibited both cocaine bioactivation and covalent binding and thus protected through prealkylative mechanisms. 4. Data demonstrate that cocaine-induced acute lethal hepatocyte injury was mediated by non-alkylative mechanisms, and that covalent adduct formation could be clearly dissociated from the consequences of oxidative stress that lead to cell killing.

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.

Neurons and glial cells of the enteric nervous system: studies in tissue culture

The enteric nervous system (ENS) has been recognized as the main component in regulating the function of the digestive tract and as a model for studying neuronal physiology and pharmacology. Most of the present knowledge on the ENS was derived from in vitro studies on freshly isolated plexuses. In 1978 the first study on cultured myenteric neurons was published and since then there has been a growing interest in this method. Several different culture preparations have been introduced, including the recent development of cultures from adult guinea-pigs and humans. This review summarizes the findings which have been made using cultured enteric neurons and glia. The main topics that are described are the role of the extracellular matrix and of hormones on neuronal growth, neuron-glia interactions, release of neuropeptides and their actions on neurons and co-transmission between neurons.

Chronic ethanol and cocaine-induced hepatotoxicity: effects of vitamin E supplementation

The mechanisms of chronic cocaine toxicity and its potentiation by ethanol were investigated. Cocaine was administered to male C57BL/6 mice (20 mg/kg by peritoneal injection twice a day) alone or in combination with ethanol-containing diets (26% of total calories) supplied with a normal (20 IU/liter) or high content (170 IU/liter) of vitamin E. Liver levels of vitamin E, reduced glutathione, ascorbic acid, and hydroxyproline were measured. Accumulation of thiobarbituric acid-reactive substances, after in vitro stimulation of lipid peroxidation by Fe3+/ADP/ascorbate system, was measured as an index of susceptibility of hepatic membranes to oxidative stress. Plasma alanine aminotransferase, lethality, liver weight, and liver/body weight ratio were determined to assess the extent of liver toxicity. Consumption of ethanol exacerbated liver toxicity induced by cocaine treatments and reduced survival, but ethanol or cocaine treatments alone caused no or only modest mortality. Ethanol potentiated cocaine-induced accumulation of collagen in the liver and depletion of ascorbic acid. Hepatotoxicity induced by the combined ethanol plus cocaine treatment was not accompanied by a decrease in intracellular vitamin E or glutathione content. There were no changes in the basic levels and in the rate of accumulation of thiobarbituric acid-reactive substances in liver homogenates under the lipid peroxidation-stimulating system in vitro. The toxic effects of ethanol and cocaine were not reduced by the ingestion of vitamin E during short-term exposure of 21 days of treatment.

Cocaethylene hepatotoxicity in mice

Cocaethylene is a novel metabolite of cocaine formed in the presence of ethanol. When administered to ICR male mice in dosages ranging from 10 to 50 mg/kg, i.p., cocaethylene was found to produce dose-dependent hepatic necrosis in the midlobular zone (zone 2). Severity of the lesion was maximal 12-24 hr after administration. A transient but significant decrease in hepatic glutathione content was observed 1 hr after cocaethylene administration. Pretreatment with the cytochrome P450 inhibitors cimetidine (200 mg/kg, i.p., in divided doses) or SKF 525A (50 mg/kg, i.p.) diminished toxicity. Pretreatment of mice with the esterase inhibitor diazinon (10 mg/kg, i.p.) increased cocaethylene hepatotoxicity, as did pretreatment with the cytochrome P450 inducing agents phenobarbital (80 mg/kg/day, i.p., for 3 days) or beta-naphthoflavone (40 mg/kg/day, i.p., for 3 days). Phenobarbital pretreatment also caused a shift in the morphologic site of necrosis from midzonal to peripheral lobular (zone 1) regions. The type of hepatic lesion produced by cocaethylene, its morphologic distribution (including the shift with phenobarbital treatment), the potency of cocaethylene in producing this effect, and the apparent requirement of oxidative metabolism for hepatoxicity were all remarkably similar to observations with its parent compound, cocaine, in this and earlier studies. This suggests that these compounds produce liver toxicity through the same or similar mechanisms.

Cocaine hepatotoxicity: influence of hepatic enzyme inducing and inhibiting agents on the site of necrosis

Cocaine-induced hepatotoxicity has been reported in human beings and is well documented in mice. One interesting feature of this toxicity that appears to be common to both species is an apparent shift in the intraacinar site of necrosis under circumstances known to alter cocaine metabolism. However, the evidence in human subjects is limited, and studies elucidating the mechanism of this phenomenon cannot be performed in human beings. Although future studies in mice may define the basis of this mechanism, the current evidence is a somewhat fragmented composite of studies using different mouse strains and enzyme-inducing agents. Therefore a comprehensive pathologic investigation was initiated for the purpose of identifying and establishing an animal model suitable for studying this phenomenon. In naive ICR mice a single 60 mg/kg dose of cocaine was found to produce midzonal (zone 2) coagulative necrosis. In mice whose oxidative metabolism had been increased with beta-ionone or in which esterase metabolism had been inhibited by diazinon, the severity of the toxicity was increased but the intraacinar origin of the lesion did not change. However, when the oxidative microsomal metabolism of ICR mice was induced by phenobarbital or beta-naphthoflavone, the acinar zone affected was dramatically different. Phenobarbital induction produced zone 1 necrosis, whereas beta-napthoflavone induction caused necrosis in zone 3. The site of necrosis corresponded with the distribution of cocaine, and its metabolites were identified with colloidal gold-conjugated antibody probes. The results of this study suggest that the agents shifting the location of cocaine-induced hepatic necrosis alter the intraacinar site of protein binding of cocaine and its metabolites.

Interactions between human immunodeficiency virus-1, hepatitis delta virus and hepatitis B virus infections in 260 chronic carriers of hepatitis B virus

To evaluate the factors determining the severity of chronic hepatitis B virus infection and the interactions of human immunodeficiency virus and hepatitis delta virus infections, we retrospectively analyzed 260 patients, 146 of whom were followed for a mean of 31.4 +/- 1.8 mo. Human immunodeficiency virus, hepatitis B virus, and hepatitis delta virus status and aminotransferase activities, histological activity index, alcohol consumption and the prevalence of cirrhosis were investigated. The patients included 54 homosexuals, 19 parenteral drug abusers and 187 subjects with other or unidentified risk factors for exposure to hepatitis B virus. Thirty-five patients (13%) were positive for antibody to human immunodeficiency virus; 27 were homosexual and 8 were drug abusers. The mean aminotransferase activities, histological activity index and the prevalence of cirrhosis were similar in the human immunodeficiency virus-positive and human immunodeficiency virus-negative subgroups. Actuarial survival was significantly lower in the human immunodeficiency virus-negative subgroups. Actuarial survival was significantly lower in the human immunodeficiency virus-positive group than in the human immunodeficiency virus-negative subjects (p = 0.004); the cause of death was clearly related to liver failure in four of the five human immunodeficiency virus-positive patients and two of the six human immunodeficiency virus-negative subjects who died. To evaluate the factors determining the severity of liver disease, we compared homogeneous subgroups of subjects. Among the homosexual patients, the prevalence of HBeAg and hepatitis B virus DNA, aminotransferase activities and the histological activity index did not differ according to human immunodeficiency virus antibody status.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatotoxicity associated with cocaine abuse

The mechanisms evaluated in animals as being responsible for cocaine associated hepatotoxicity are presented. The importance of the P-450 enzyme system in cocaine associated hepatotoxicity is emphasized. Moreover, the putative critical role of free radicals in such injury is discussed. Finally, the growing literature on clinical cases of cocaine hepatotoxicity is reviewed.

Hepatic morphologic and biochemical changes induced by subacute cocaine administration in mice

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-hydroxynorcocaine on isolated mitochondria had no effect on the ADP:O or respiratory control ratios, at concentrations up to 2.0 mM. Our studies demonstrate that any early cellular alterations in cocaine-induced hepatic injury are manifested in intermediate filaments and endoplasmic reticulum with no evidence of mitochondrial involvement.

The role of alcohol in cocaine dependence

The relationships between the patterns of alcohol and cocaine use are examined using information derived from the authors' research data and from the literature. Excessive alcohol drinking was very prevalent among males seeking treatment for cocaine dependence at a Veterans Administration hospital in West Los Angeles. Fifty percent met DSM-III-R criteria for alcohol dependence. The drug-related behaviors of patients with the diagnosis of dependence on cocaine only were compared with those of patients dependent on cocaine and alcohol. The progression of the cocaine addiction was not significantly different in those two groups. However, patients with dependence on cocaine and alcohol were more likely to be users of other drugs of abuse. Concerning psychosocial behaviors, both groups maintained employment and stable interpersonal relationships throughout significant periods of their addictive career. One year after drug treatment, both subsamples showed significant improvement in terms of cocaine and alcohol use and social adjustment. Research implications and the possibility that both dependent conditions may share neurobehavioral reinforcing mechanisms are discussed.

Ethanol-induced enhancement of cocaine bioactivation and irreversible protein binding: evidence against a role of cytochrome P-450IIE1

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-450IIE1 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-450IIE1. 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 microsomal proteins (by 100%), which was taken as a quantitative endpoint for the formation of a reactive metabolite. Cocaine N-demethylation and irreversible protein binding of cocaine were not inhibited by P-450IIE1 isozyme-selective substrates, nor was the rate of cocaine metabolism and binding decreased by functionally active polyclonal anti-rat P-450IIE1 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-450IIE1, (b) the enhancing effects of ethanol on cocaine bioactivation may be due to induction of other P-450 isoforms, and (c) induction of P-450IIE1 may potentiate cocaine-induced hepatocellular toxicity in vitro independently of cocaine metabolism, e.g., by P-450IIE1-dependent oxidative stress.

Biomechanisms of cocaine-induced hepatocyte injury mediated by the formation of reactive metabolites

Cocaine is an intrinsic hepatotoxin in laboratory animals, and there is growing evidence that high doses of cocaine can precipitate hepatic necrosis in humans. The rodent model of cocaine hepatotoxicity is commensurate with the concept that a multistep mainly cytochrome P-450 dependent N-oxidative pathway is responsible for the expression of hepatocellular injury. Among the possible biomechanisms by which cocaine exerts its cytotoxic effects, direct oxidative damage by reactive oxygen species generated by redox cycling during the metabolic cascade seems most important. The role of the ensuing lipid peroxidation and protein thiol oxidation is less clear. Similarly, the functional role of irreversible (covalent) binding of a not yet defined electrophilic cocaine intermediate to hepatocellular proteins remains enigmatic so long as the critical molecular targets have not been identified. Finally, glutathione plays a pivotal protective role against cocaine-induced hepatic injury. Interactions with ethanol or inducers of the expression of the cytochrome P-450IIB subfamily can potentiate cocaine hepatotoxicity. Thus, the net amount of the ultimate reactive species seems to determine the severity of the hepatic lesions and to be responsible for the marked interspecies, interstrain, and sex differences. Recent advances in culture techniques of hepatocytes and precision-cut liver slices from various species including man have made it possible to correlate cocaine biotransformation with cytotoxicity and to selectively study the putative cellular mechanisms. Clearly, more studies are necessary to further illuminate our understanding of the role of the biochemical and molecular events precipitating hepatic necrosis during cocaine-mediated hepatotoxicity.

Potentiation of cocaine hepatotoxicity by ethanol in human hepatocytes

The hepatotoxic effects of cocaine on the human liver and the effect of ethanol on cocaine-induced hepatotoxicity have been examined in adult human hepatocytes cultured in chemically defined conditions. Cultures were exposed to concentrations of cocaine ranging from 10(-2) to 10(-5) M. Cytotoxicity was evaluated after 24 hr of continuous exposure to cocaine by measuring the leakage of intracellular LDH and the ability of cells to reduce MTT. According to these end-point parameters, half-maximal cytotoxic concentrations of cocaine for human hepatocytes (IC50) were 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 for 24 hr resulted in a 50% decrease in hepatic glycogen, a 40% decrease in cellular glutathione content, and a 40% decrease in urea synthesis with respect to control values. For most of the metabolic parameters assayed, significant alterations were observed at 0.5 mM cocaine. Glycogen reloading of hepatocytes began to be inhibited in the presence of 0.60 mM cocaine (IC10). Ethanol greatly potentiated cocaine-induced hepatotoxicity. After a 48 hr pretreatment of human hepatocytes with 50 mM ethanol, low concentration 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% degradation of glycogen stores, and a 30% reduction in glutathione content. The results of our work show that ethanol increases the effects of cocaine on human hepatocytes by a factor of 10.

Reactive oxygen species and non-peroxidative mechanisms of cocaine-induced cytotoxicity in rat hepatocyte cultures

Primary short-term cultures of hepatocytes derived from phenobarbital-induced male Sprague-Dawley rats were used to investigate the mechanisms of cocaine-induced cytotoxicity. Exposure of cells to cocaine resulted in a time and concentration-dependent release of lactate dehydrogenase (LDH) into the culture medium which became evident after 7 h of incubation. Over the course of 24 h incubation with cocaine (0.3 mM) there was no significant lipid peroxidation (measured as the formation of thiobarbituric acid-reactive substances. TBA-RS). The addition of the ferric iron chelator, deferoxamine (DFO), prevented in part cocaine-induced LDH release. Alternatively, addition of the antioxidant, alpha-tocopherol polyethylene glycol 1000 succinate (TPGS), did not protect against hepatocyte injury. Depletion of the intracellular glutathione (GSH) with diethyl maleate (DEM) to below critical levels for antioxidative protection markedly accelerated the onset and increased the extent of cocaine-induced LDH release, concomitant with massive production of lipid peroxidation. During the first four hours of incubation DFO and TPGS protected against cocaine-induced cytotoxicity in GSH-depleted cells. However, at later stages (24 h), the protective effect was lost even in the absence of lipid peroxidation. These results suggest that reactive oxygen species are involved in cocaine-mediated hepatocyte injury. However, lipid peroxidation can be dissociated from other, non-peroxidative, iron-dependent mechanisms of oxidative cell injury.

Liver function tests in non-parenteral cocaine users

To investigate the effect of cocaine on standard liver function tests (LFT), we studied 46 cocaine users with no history of parenteral drug use or homosexuality. LFT were similar in 21 users of cocaine only (Group A) and 25 users of cocaine and alcohol (Group B). Only three patients, two of whom were hepatitis B carriers, had an alanine aminotransferase level more than five units above normal limits. Group B patients were significantly more likely to complain of headaches, irritability, and loss of memory. We conclude that (1) non-parenteral cocaine use is rarely associated with significant LFT abnormalities and (2) alcohol may potentiate some adverse effects of cocaine.

Modulation of cocaine metabolism in primary rat hepatocyte cultures: effects on irreversible binding and protein biosynthesis

To study mechanisms of cocaine-induced hepatotoxicity, short-term-cultured rat hepatocytes were exposed to cocaine or norcocaine at 10(-6) to 10(-4) M. Induction in vivo (with Aroclor 1254) or inhibition in vitro (with SKF-525A) of cytochrome P450 modulated the rate of oxidative biotransformation of cocaine to norcocaine and to other metabolites in vitro. The quantitative changes in the metabolic conversion of cocaine were paralleled by the amount of radiolabeled cocaine equivalents irreversibly bound to hepatocellular protein. Furthermore, induction of cytochrome P450-mediated cocaine or norcocaine metabolism was associated with inhibition of protein biosynthesis in cultured hepatocytes, whereas this effect was restored to normal when the oxidative metabolism was blocked by SKF-525A. Glutathione depletion with buthionine sulfoximine both increased the covalent binding of cocaine to hepatic macromolecules and augmented the inhibitory effect on protein biosynthesis. The integrity of the hepatocellular plasma membrane was not affected (no effect on lactate dehydrogenase leakage). The results indicate that in rat hepatocytes (a) a high proportion of intracellular cocaine is converted to a reactive metabolite which irreversibly binds to protein, and (b) irreversible binding of cocaine to hepatic protein is associated with impairment of hepatocellular function and could play a role in cocaine-mediated hepatotoxicity.