Cocaine Detoxification by Human Plasma Butyrylcholinesterase (original) (raw)
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Therapeutic Use of Butyrylcholinesterase for Cocaine Intoxication
Toxicology and Applied Pharmacology, 1997
The administration of human butyrylcholinesterase Therapeutic Use of Butyrylcholinesterase for Cocaine Intoxica-(BChE), an endogenous plasma enzyme that metabolizes tion. Mattes, C. E., Lynch, T. J., Singh, A., Bradley, R. M., Kelcocaine to a nontoxic metabolite, has been shown to decrease laris, P. A., Brady, R. O., and Dretchen, K. L. (1997). Toxicol. Appl. the hypertensive and arrhythmogenic effects of cocaine in Pharmacol. 145, 372-380.
European journal of …, 2005
Butyrylcholinesterase is a major cocaine-metabolizing enzyme in humans and other primates, catalyzing hydrolysis to ecgonine methylester. Increasing butyrylcholinesterase activity may be a treatment for cocaine addiction. We evaluated the effect of 30-min pretreatment with horse-derived butyrylcholinesterase (5-15,000 U i.v.) or with the selective butyrylcholinesterase inhibitor cymserine (10 mg/kg i.v.) on the metabolism of cocaine (17 mg/kg i.p.) in anesthetized rats. Venous blood samples were collected for two hours after cocaine administration and later assayed for cocaine and metabolites by gas chromatography/mass spectroscopy. Whole brains were collected after the last blood sample and similarly assayed. Butyrylcholinesterase significantly increased plasma and brain ecgonine methylester levels and decreased cocaine plasma half-life from 26.2 min (saline) to 16.4 min (15,000 U). Butyrylcholinesterase had no significant effect on plasma or brain cocaine or benzoylecgonine levels. Cymserine had no effect on any variable. These findings suggest that butyrylcholinesterase treatment may have benefits in enhancing cocaine metabolism and in increasing levels of ecgonine methylester, which may have a protective action against cocaine.
Molecular Pharmacology, 1999
Butyrylcholinesterase (BChE) has a major role in cocaine detoxication. The rate at which human BChE hydrolyzes cocaine is slow, with a k cat of 3.9 min Ϫ1 and K m of 14 M. Our goal was to improve cocaine hydrolase activity by mutating residues near the active site. The mutant A328Y had a k cat of 10.2 min Ϫ1 and K m of 9 M for a 4-fold improvement in catalytic efficiency (k cat /K m). Since benzoylcholine (k cat 15,000 min Ϫ1) and cocaine form the same acyl-enzyme intermediate but are hydrolyzed at 4000-fold different rates, it was concluded that a step leading to formation of the acyl-enzyme intermediate was rate-limiting. BChE purified from plasma of cat, horse, and chicken was tested for cocaine hydrolase activity. Compared with human BChE, horse BChE had a 2-fold higher k cat but a lower binding affinity, cat BChE was similar to human, and chicken BChE had only 10% of the catalytic efficiency. Naturally occurring genetic variants of human BChE were tested for cocaine hydrolase activity. The J and K variants (E497V and A539T) had k cat and K m values similar to wild-type, but because these variants are reduced to 66 and 33% of normal levels in human blood, respectively, people with these variants may be at risk for cocaine toxicity. The atypical variant (D70G) had a 10-fold lower binding affinity for cocaine, suggesting that persons with the atypical variant of BChE may experience severe or fatal cocaine intoxication when administered a dose of cocaine that is not harmful to others. Cocaine 1 abuse is a medical problem in the United States. About 23 million Americans have used cocaine at least once and approximately 5 million are habitual users (Das, 1993). The number of cocaine-related emergency room visits is about 100,000 annually (Schrank, 1992). Among a total of 14,843 residents of New York City who received fatal injuries from 1990 through 1992, 26.7% had cocaine or a metabolite in their urine or blood (Marzuk et al., 1995). Life-threatening symptoms due to cocaine toxicity include grand-mal seizures, cardiac arrest, stroke, and drug-induced psychosis accompanied by elevated body temperature (Rich and Singer, 1991; Das, 1993; Warner, 1993). There is evidence that butyrylcholinesterase (BChE, EC 3.1.1.8) is the major detoxicating enzyme of cocaine. The first experiments that identified BChE as a cocaine hydrolase came from the laboratory of W. Kalow (Stewart et al., 1977, 1979; Inaba et al., 1978). They recognized that only a small percentage of cocaine appeared unchanged in the urine of humans and that the major metabolites resulted from the hydrolytic splitting of ester bonds (Fig. 1). Human plasma was known to contain only two major esterases, BChE and paraoxonase. The esterase in blood that hydrolyzes cocaine was identified as BChE by showing that diisopropyl fluorophosphate, eserine, and sodium fluoride, three characteristic inhibitors of BChE, inhibited hydrolysis of cocaine. By contrast, EDTA, an inhibitor of paraoxonase, did not inhibit hydrolysis of cocaine by plasma. Furthermore, purified BChE accounted for all the cocaine hydrolase activity seen in plasma. The metabolite produced by BChE in the test tube was ecgonine methyl ester (Fig. 1); ecgonine methyl ester was also a major metabolite found in urine, thus supporting a role for BChE in metabolism of cocaine (Inaba et al., 1978). A second metabolite found in high amounts in urine was benzoylecgonine (Fig. 1). This metabolite is produced by spontaneous hydrolysis at alkaline pH as well as by liver carboxylesterase (Brzezinski et al., 1994). Animal studies showed that administration of purified human BChE protected mice and rats from the toxic effects of cocaine. Hoffman et al. (1996) gave mice an i.p. injection of
Journal of Clinical Toxicology, 2018
Background: Cocaine is a commonly used illegal recreational drug and its consumption can produce various adverse health effects in animal and clinical studies. To date no information is available on whether exposed to cocaine will result in abnormally high plasma AChE activity in animals and whether it is characteristic of apoptosis. Our goals were to examine the relationship between enhanced AChE activity and cocaine-induced apoptosis and the possible underlying mechanisms. Methods: For this purpose, carboxylesterase and butyrylcholinesterase deficient ES1-/-BChE-/-mice in strain C57BL/6 were treated intraperitoneally with 25 mg/kg cocaine daily for 8 days and sacrificed on day 9. Plasma AChE activity and body temperature were measured before and after treatment. Tissue sections from brain, heart, kidney, and liver were stained for AChE activity and apoptosis. Results: Mice had a 1°C decrease in surface body temperature at 10 min after cocaine treatment and the temperature returned to base line by 30 min. Plasma AChE activity in mice increased about 1.5-fold on days 7-8 and 1.75-fold on days 9 after cocaine treatment. More apoptotic cells were observed in liver sections of treated mice compared to controls. TUNEL-positive cells in the liver also stained heavily for AChE activity. Conclusions: AChE activity and apoptosis were both induced in carboxylesterase and butyrylcholinesterase knockout mice treated with cocaine. Their relationship might provide some novel information of cocaineassociated toxicity. Abnormally high plasma AChE activity may be an effect biomarker of cocaine exposure.
Addiction Biology, 2013
ABSTRACTa db_424 30..39 Although substantial research effort has focused on developing pharmacological treatments for cocaine abuse, no effective medications have been developed. Recent studies show that enzymes that metabolize cocaine in the periphery, forestalling its entry into the brain, can prevent cocaine toxicity and its behavioral effects in rodents. Here we report on effects of one such enzyme (Albu-CocH) on the pharmacokinetic and behavioral effects of cocaine in squirrel monkeys. Albu-CocH was developed from successive mutations of human butyrylcholinesterase (BChE) and has 1000-fold greater catalytic activity against cocaine than naturally occurring BChE. Pharmacokinetic studies showed that Albu-CocH (5 mg/kg) had a half-life of 56.6 hours in squirrel monkeys. In these studies, plasma levels of cocaine following i.v. 1 mg/kg cocaine were reduced 2 hours after administration of Albu-CocH, whereas plasma levels of the cocaine metabolite ecgonine methyl ester were increased. These effects were still evident 72 hours following Albu-CocH administration. In behavioral experiments in monkeys, pre-treatment with 5 mg/kg Albu-CocH dramatically decreased self-administration of a reinforcing dose of i.v. cocaine (30 mg/kg/injection) for over 24 hours. Pre-treatment with 5 mg/kg Albu-CocH also attenuated the reinstatement of extinguished cocaine self-administration by an i.v. priming injection of cocaine (0.1 or 0.3 mg/kg) and, in separate studies, attenuated the discriminative-stimulus effects of cocaine. The ability of Albu-CocH to attenuate the abuse-related effects of cocaine in squirrel monkeys indicates that further investigation of BChE mutants as potential treatment for cocaine abuse and toxicity is warranted.
Increased Hepatotoxicity and Cardiac Fibrosis in Cocaine-Treated Butyrylcholinesterase Knockout Mice
Basic & Clinical Pharmacology & Toxicology, 2008
In mice, cocaine is detoxified to inactive products by butyrylcholinesterase (BChE) and carboxylesterase. In human beings, cocaine detoxification is primarily by BChE. The focus of this investigation was to elucidate the importance of BChE in reducing pathophysiological effects following cocaine exposure. Previous studies examining the effects of cocaine on BChE deficient animals relied on chemical inhibition of BChE with tetraisopropyl pyrophosphoramide (iso-OMPA). The creation of the BChE knockout mouse has provided a model for studying pathological effects of cocaine in mice free of chemical confounders. We hypothesized that mice with low or no BChE activity would have reduced cocaine metabolism, leading to hepatotoxicity and cardiomyopathy. A high-resolution in vivo imaging system recorded cardiac and respiratory function following treatment with a carboxylesterase inhibitor and a high dose of cocaine (100 mg/kg, intraperitoneally). The BChE − / − mice demonstrated depressed respiration through 12 hr after dosing and abnormal respiratory patterns consisting of a pause at full inspiration (apneusis), whereas BChE+/+ mice had recovered normal respiration rates by 30 min. after dosing and exhibited no apneusis. Liver and cardiac histology sections were analysed following a 20 mg/kg intraperitoneally dose of cocaine administered daily for 7 days. BChE-/-mice treated for 7 days with the chronic low dose showed significant hepatotoxicity and cardiac perivascular fibrosis compared to BChE+/+ mice. The observed functional changes following acute high-dose and chronic low-dose cocaine in BChE − / − and +/ − mice warrants further investigation into the possibility of increased cocaine toxicity in human beings with BChE deficiency.
Journal of Pharmacology and Experimental Therapeutics, 2002
Human butyrylcholinesterase (BChE) hydrolyzes cocaine to inactive metabolites. A mutant of human BChE, A328W, hydrolyzed cocaine 15-fold faster compared with wild-type BChE. Although the catalytic properties of human BChE secreted by Chinese hamster ovary (CHO) cells are identical to those of native BChE, a major difference became evident when the recombinant BChE was injected into rats and mice. Recombinant BChE disappeared from the circulation within minutes, whereas native BChE stayed in the blood for a week. Nondenaturing gel electrophoresis showed that the recombinant BChE consisted mainly of monomers and dimers. In contrast, native BChE is a tetramer. The problem of the short residence time was solved by finding a method to assemble the recom-binant BChE into tetramers. Coexpression in CHO cells of BChE and 45 residues from the N terminus of the COLQ protein yielded 70% tetrameric BChE. The resulting purified recombinant BChE tetramers had a half-life of 16 h in the circulation of rats and mice. The 16-h half-life was achieved without modifying the carbohydrate content of recombinant BChE. The protective effect of recombinant wild-type and A328W mutant BChE against cocaine toxicity was tested by measuring locomotor activity in mice. Pretreatment with wild-type BChE or A328W tetramers at a dose of 2.8 units/g i.p. reduced cocaineinduced locomotor activity by 50 and 80%. These results indicate that recombinant human BChE could be useful for treating cocaine toxicity in humans.
Journal of forensic …, 2006
Cocaine is known to degrade in vivo and in vitro by several hydrolytic mechanisms. A previous study found that the initial amount of cocaine added to plasma could be accounted for by summing the molar concentrations of cocaine's hydrolysis products and the cocaine remaining after hydrolysis. The present study was undertaken to investigate whether or not relationships might exist between such molar concentration sums for different postmortem bodily fluids. Determinations of cocaine, benzoylecgonine, ecgonine methyl ester, and ecgonine were performed using liquid chromatography/mass spectrometry (LC/MS/MS) with heart blood, femoral blood, vitreous humor (VH), and urine (UR). The results demonstrate a strong correlation between blood and VH concentrations (correlation coefficients of 0.88-0.94), weak correlation between the UR and blood concentrations (correlation coefficients of 0.61-0.64), and weak correlation between UR and VH concentrations (correlation coefficient of 0.59). The results demonstrate that ecgonine is a significant hydrolysate with concentrations on the same order of magnitude as benzoylecgonine. The results are consistent with rapid distribution of the parent drug and its hydrolysates in the blood and VH. The strong correlation between the blood and VH demonstrates that VH is an important medium for toxicology testing when attempting to make a determination of cocaine intoxication.
Cocaine residue in plasma, cardiac and tracheal tissues of chronic cocaine-treated guinea-pigs
Supersensitivity of adrenoceptors to catecholamines is one of the mechanisms of cocaine-related cardiac complication. The precise mechanism of cocaine enhancing supersensitivity of adrenoceptors is unconcluded. The aim of this study was todetermine the levels of cocaine in plasma, cardiac and tracheal tissues in order to correlate with the supersensitivity ofadrenoceptors to catecholamines. In this study, two groups of ten guinea-pigs each were injected with 2.5 mg/kg cocaine or normal saline solution intraperitoneally twice daily for 14 days. After 24 hours of cocaine cessation, the cocaine levels in plasma, cardiac and tracheal tissues were determined using high performance liquid chromatography. The results showed that the cocaine levels in plasma and tracheal smooth muscle were 5.08±0.63 ng/ml and 2.8±0.41 ng/mg, respectively, while those in atria and ventricle were lower than 17.5 ng/g and 3.8 ng/g, respectively. These levels were less than the level that had been reported to b...