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The continuous emergence of new illegal compounds, particularly psychoactive chemicals, poses significant challenges for current drug detection methods. Developing new protocols and kits for each new drug requires substantial time, effort, and dedicated manpower. Whole-cell bacterial bioreporters have been proven capable of detecting diverse hazardous compounds in both laboratory and field settings, identifying not only single compounds but also chemical families. We present the development of a microbial bioreporter for the detection of cocaine, the nervous system stimulant that is the second-most widely used illegal drug in the US. Escherichia coli was transformed with a plasmid containing a bacterial luxCDABEG bioluminescence gene cassette, activated by a cocaine-responsive signaling cascade. The engineered bioreporter is demonstrated to be a sensitive and specific first-generation detection system for cocaine, with detection thresholds of 17 ± 8 μg/L and 130 ± 50 μg/L in a buffer solution and in urine, respectively. Further improvement of the sensor's performance was achieved by altering the nucleotide sequence of the PBen gene promoter, the construct's sensing element, using accelerated site-directed evolution. The applicability of ready-to-use paper strips with immobilized bioreporter cells was demonstrated for cocaine detection in aqueous solutions. [ABSTRACT FROM AUTHOR]

Background: Cocaine is a commonly abused drug and there is no approved medication specifically to treat its addiction or overdose. Bacterial cocaine esterase (CocE)-derived RBP-8000 is currently under clinical development for cocaine overdose treatment. It is proven to be effective for human use to accelerate cocaine metabolism into physiologically inactive products. Besides cocaine, RBP-8000 may hydrolyze the neurotransmitter acetylcholine (ACh), however, no study has reported its cholinesterase activity. The present study aims to examine RBP-8000's cholinesterase activity and substrate selectivity to address the potential concern that this enzyme therapy might produce cholinergic side-effects.Methods: Both computational modeling and experimental kinetic analysis were carried out to characterize the potential cholinesterase activity of RBP-8000. Substrates interacting with RBP-8000 were modeled for their enzyme-substrate binding complexes. In vitro enzymatic kinetic parameters were measured using Ellman's colorimetric assay and analyzed by Michaelis-Menten kinetics.Results: It is the first demonstration that RBP-8000 catalyzes the hydrolysis of acetylthiocholine (ATC). However, its catalytic efficiency (kcat/KM) against ATC is 1000-fold and 5000-fold lower than it against cocaine at 25 °C and 37 °C, respectively, suggesting RBP-8000 has the desired substrate selectivity for cocaine over ACh.Conclusion: Given the fact that clinically relevant dose of RBP-8000 displays insignificant cholinesterase activity relative to endogenous cholinesterases in human, administration of RBP-8000 is unlikely to produce any significant cholinergic side-effects. This study provides supplemental evidences in support of further development of RBP-8000 towards a clinically used pharmacotherapy for cocaine overdose. [ABSTRACT FROM AUTHOR]

RBP-8000 is a double mutant cocaine esterase that rapidly metabolizes cocaine. This study was conducted to assess the pharmacokinetics of cocaine and cocaine-induced physiological effects in the absence (placebo) or presence of RBP-8000. Twenty-nine cocaine abusers were randomized 1:1 (active: placebo) to 4 sequences and 2 treatment periods. In the presence of RBP-8000, cocaine plasma exposures dropped by 90% within 2 min; cocaine-induced physiological effects were significantly reduced with higher extent and faster decrease in systolic blood pressure and pulse rate compared to placebo. This study provides strong evidence in support to use RBP-8000 as a pharmacotherapy for cocaine intoxication. [ABSTRACT FROM AUTHOR]

Abstract: Background: Cocaine toxicity is a prevalent problem in the Unites States for which there is currently no FDA-approved pharmacotherapy. We have developed a bacterial cocaine esterase (CocE) towards this indication. A thermostabilized mutant of CocE (DM-CocE) retains the hydrolytic activity of the wild-type esterase, rapidly hydrolyzing cocaine into the inactive metabolites ecgonine methyl ester and benzoic acid, and can prevent cocaine toxicities in rodent and non-human primate models. To advance DM-CocE towards clinical use, we examine here how the hydrolytic activity of DM-CocE is altered by some drugs commonly co-administered with cocaine. Methods: We employed a spectrophotometric cocaine hydrolysis assay to evaluate whether pharmacologically relevant doses of alcohol, nicotine, morphine, phencyclidine, ketamine, methamphetamine, naltrexone, naloxone, or midazolam would alter the Michaelis–Menten kinetics of DM-CocE for cocaine. Mass spectrometry was used to evaluate interaction with diazepam as this drug interferes with the absorbance spectra of cocaine critical for the spectrophotometric assay. Results: Alcohol, nicotine, morphine, phencyclidine, ketamine, methamphetamine, naltrexone, naloxone, and midazolam did not alter cocaine hydrolysis by DM-CocE. However, diazepam significantly slowed DM-CocE cocaine hydrolysis at very high concentrations, most likely through interaction of the phenyl ring of the benzodiazepine with the active site of DM-CocE. Conclusions: DM-CocE does not display significant drug interactions, with the exception of diazepam, which may warrant further study as DM-CocE progresses towards a clinically used pharmacotherapy for cocaine toxicity. Alternate benzodiazepines, e.g., midazolam could be used to avoid this potential interaction. [Copyright &y& Elsevier]

Abstract: Background: A longer acting, double mutant bacterial cocaine esterase (CocE T172R/G173Q; DM CocE) has been shown to protect mice from cocaine-induced lethality, inhibit the reinforcing effects of cocaine in rats, and reverse cocaine''s cardiovascular effects in rhesus monkeys. The current studies evaluated the effectiveness of DM CocE to protect against, and reverse cocaine''s cardiovascular, convulsant, and lethal effects in male and female rats. Methods: Pretreatment studies were used to determine the effectiveness and in vivo duration of action for DM CocE to protect rats against the occurrence of cardiovascular changes, convulsion and lethality associated with acute cocaine toxicity. Posttreatment studies were used to evaluate the capacity of DM CocE to rescue rats from the cardiovascular and lethal effects of large doses of cocaine. In addition, male and female rats were studied to determine if there were any potential effects of sex on the capacity of DM CocE to protect against, or reverse acute cocaine toxicity in rats. Results: Pretreatment with DM CocE dose-dependently protected rats against cocaine-induced cardiovascular changes, convulsion and lethality, with higher doses active for up to 4h, and shifting cocaine-induced lethality at least 10-fold to the right. In addition to dose-dependently recovering rats from an otherwise lethal dose of cocaine, post-treatment with DM CocE also reversed the cardiovascular effects of cocaine. There were no sex-related differences in the effectiveness of DM CocE to protect against, or reverse acute cocaine toxicity. Conclusions: Together, these results support the development of DM CocE for the treatment of acute cocaine toxicity. [Copyright &y& Elsevier]

A long-acting mutant form of a naturally occurring bacterial cocaine esterase (T172R/G173Q CocE; double mutant CocE (DM CocE)) has previously been shown to antagonize the reinforcing, convulsant, and lethal effects of cocaine in rodents. However, the effectiveness and therapeutic characteristics of DM CocE in nonhuman primates, in a more clinically relevant context, are unknown. The current studies were aimed at (1) characterizing the cardiovascular effects of cocaine in freely moving rhesus monkeys, (2) evaluating the capacity of DM CocE to ameliorate these cocaine-induced cardiovascular effects when administered 10 min after cocaine, and (3) assessing the immunological responses of monkeys to DM CocE following repeated administration. Intravenous administration of cocaine produced dose-dependent increases in mean arterial pressure (MAP) and heart rate (HR) that persisted throughout the 2-h observation period following a dose of 3.2 mg/kg cocaine. Cocaine failed to produce reliable changes in electrocardiograph (ECG) parameters, body temperature, and locomotor activity. DM CocE produced a rapid and dose-dependent amelioration of the cardiovascular effects, with saline-like MAP measures restored within 5-10 min, and saline-like HR measures restored within 20-40 min of DM CocE administration. Although administration of DM CocE produced increases in anti-CocE antibodies, they did not appear to have a neutralizing effect on the capacity of DM CocE to reverse the cardiovascular effects of cocaine. In conclusion, these findings in monkeys provide strong evidence to suggest that highly efficient cocaine esterases, such as DM CocE, can provide a potential therapeutic option for treatment of acute cocaine intoxication in humans. [ABSTRACT FROM AUTHOR]

Cocaine is considered to be the most addictive of all substances of abuse and mediates its effects by inhibiting monoamine transporters, primarily the dopamine transporters. There are currently no small molecules that can be used to combat its toxic and addictive properties, in part because of the difficulty of developing compounds that inhibit cocaine binding without having intrinsic effects on dopamine transport. Most of the effective cocaine inhibitors also display addictive properties. We have recently reported the use of cocaine esterase (CocE) to accelerate the removal of systemic cocaine and to prevent cocaine-induced lethality. However, wild-type CocE is relatively unstable at physiological temperatures (τ1/2 ∼13 min at 37°C), presenting challenges for its development as a viable therapeutic agent. We applied computational approaches to predict mutations to stabilize CocE and showed that several of these have increased stability both in vitro and in vivo, with the most efficacious mutant (T172R/G173Q) extending half-life up to 370 min. Here we present novel X-ray crystallographic data on these mutants that provide a plausible model for the observed enhanced stability. We also more extensively characterize the previously reported variants and report on a new stabilizing mutant, L169K. The improved stability of these engineered CocE enzymes will have a profound influence on the use of this protein to combat cocaine-induced toxicity and addiction in humans. [ABSTRACT FROM PUBLISHER]

Abstract: Enhancing cocaine metabolism by administration of cocaine esterase (CocE) has been considered as a promising treatment strategy for cocaine overdose and addiction, as CocE is the most efficient native enzyme yet identified for metabolizing the naturally occurring cocaine. A major obstacle to the clinical application of CocE, however, lies in its thermo-instability, rapid degradation by circulating proteases, and potential immunogenicity. PEGylation, namely by modifying a protein or peptide compound via attachment of polyethylene glycol (PEG) chains, has been proven to overcome such problems and was therefore exploited in this CocE investigation. The PEG-CocE conjugates prepared in this study showed a purity of greater than 93.5%. Attachment of PEG to CocE apparently inhibited the binding of anti-CocE antibodies to the conjugate, as demonstrated by the enzyme-linked immunosorbent assay (ELISA) assay. In addition, PEGylation yielded protection to CocE against thermal degradation and protease digestion. Furthermore, preliminary in vivo results suggested that, similarly to native CocE, the PEG-CocE conjugates were able to protect animals from cocaine-induced toxic effects. Overall, this study provides evidence that the PEGylation may serve as a tool to prolong CocE functionality in the circulation and reduce its potential immunogenicity. [Copyright &y& Elsevier]

Abstract: Background: A bacterial cocaine esterase (CocE) produces robust protection and reversal of cocaine toxicity. The aim of this study was to investigate how effectiveness of CocE was changed following its repeated administration together with cocaine. Methods: Cocaine toxicity was quantified by measuring the occurrence of convulsions and lethality in mice. Immunologic responses of CocE were determined using ELISA. In the protection experiment, i.v. CocE 0.3mg was given 1min before a lethal dose of i.p. cocaine 180mg/kg. In the rescue experiment, i.v. CocE 0.3mg was given 1min after the occurrence of convulsions elicited by i.p. cocaine 100mg/kg. In both treatment paradigms, four trials were conducted in the same animals with a 2-week interval. Results: CocE retained its effectiveness to protect or rescue mice during the first two trials and these mice did not show an immune response. In contrast, CocE''s effectiveness was gradually reduced in the last two trials, accompanied by 10- and 100-fold increases in anti-CocE antibody titers. Nevertheless, effectiveness of CocE could be partially recovered by increasing the dose of CocE. In addition, escalating the dose of CocE from the minimum effective dose for repeated administration could also retain CocE''s effectiveness longer and slow the production of anti-CocE antibodies. Conclusions: These results indicate that CocE is a weak antigen and it can maintain its protective and rescuing ability initially against cocaine-induced toxicity. Decreased effectiveness of CocE following repeated use can be partially improved by adjusting the dose and frequency of CocE treatment. [Copyright &y& Elsevier]

Abstract: Human plasma butyrylcholinesterase (BChE) is essential for cocaine detoxification even though its catalytic efficiency for that substrate is relatively poor. Site-directed mutagenesis of this protein has recently been used to obtain much-improved cocaine esterases, one of which we designate CocE. We previously showed that adenoviral transduction of such esterases caused up to 50,000-fold increases in circulating cocaine hydrolase activity, led to drastically shortened cocaine half-life, and blunted the cardiovascular responses to cocaine in rats. In those experiments, gene transduction of cocaine esterase was sustained at high levels for up to 1 week but then declined steeply. Our eventual goal is to use long-term esterase expression as a means of reducing drug reward and extinguishing intake in models of cocaine-addiction. Therefore, we investigated the site of enzyme transduction for clues to the local reactions that may limit the duration of CocE expression. Histological and immunohistochemical observations demonstrated that hepatocytes were the primary focus for transduction of modified human BChE. Rats were administered 2.2×1010 plaque forming units of a replication-incompetent, type-5 adenoviral vector incorporating CocE cDNA. Within days the livers showed intense thiocholine staining for BChE activity. Selective immunohistochemistry for human BChE proved that this activity represented CocE transgene. By 5 days, however, pockets of mononuclear cells had invaded the hepatic parenchyma, and a meshwork of IgM-like immunoreactivity had lined the hepatic sinusoids. These phenomena probably represent early responses of the immune system, either to the transduced CocE or to the hepatocytes producing this protein. [Copyright &y& Elsevier]

Abstract: The goal of this work was to identify the esterases in human plasma and to clarify common misconceptions. The method for identifying esterases was nondenaturing gradient gel electrophoresis stained for esterase activity. We report that human plasma contains four esterases: butyrylcholinesterase (EC 3.1.1.8), paraoxonase (EC 3.1.8.1), acetylcholinesterase (EC 3.1.1.7), and albumin. Butyrylcholinesterase (BChE), paraoxonase (PON1), and albumin are in high enough concentrations to contribute significantly to ester hydrolysis. However, only trace amounts of acetylcholinesterase (AChE) are present. Monomeric AChE is seen in wild-type as well as in silent BChE plasma. Albumin has esterase activity with alpha- and beta-naphthylacetate as well as with p-nitrophenyl acetate. Misconception #1 is that human plasma contains carboxylesterase. We demonstrate that human plasma contains no carboxylesterase (EC 3.1.1.1), in contrast to mouse, rat, rabbit, horse, cat, and tiger that have high amounts of plasma carboxylesterase. Misconception #2 is that lab animals have BChE but no AChE in their plasma. We demonstrate that mice, unlike humans, have substantial amounts of soluble AChE as well as BChE in their plasma. Plasma from AChE and BChE knockout mice allowed identification of AChE and BChE bands without the use of inhibitors. Human BChE is irreversibly inhibited by diisopropylfluorophosphate, echothiophate, and paraoxon, but mouse BChE spontaneously reactivates. Since human plasma contains no carboxylesterase, only BChE, PON1, and albumin esterases need to be considered when evaluating hydrolysis of an ester drug in human plasma. [Copyright &y& Elsevier]