Lasting Reduction of Cocaine Action in Neostriatum— A Hydrolase Gene Therapy Approach

Abstract

We previously found that a quadruple mutant cocaine hydrolase derived from human butyrylcholinesterase [termed cocaine esterase (CocE)] can suppress or reverse cocaine toxicity and abolish drug-primed reinstatement in rats. Here, we examined whether gene transfer of CocE reduces cocaine actions in brain reward centers. Early experiments used a standard, early region 1-deleted adenoviral vector, which, after intravenous delivery of 10 10 plaque-forming units, caused plasma cocaine hydrolase activity to rise 25,000-fold between day 4 and day 7. During this period, under a protocol that typically induces FosB expression in the caudate nucleus, these rats and unprotected controls given only empty vector or saline were subjected to repeated twice-daily injections of cocaine (30 mg/kg i.p.). Immunohistochemistry of the neostriatum on day 7 showed many FosB-reactive nuclei in unprotected rats but few if any in rats pretreated with active vector, which resembled rats never exposed to cocaine. Western blots confirmed this result. In contrast there was a more localized protection against cocaineelicited FosB induction when hydrolase vector was injected directly into the ventral striatum, which generated high transgene expression in many neurons of the target area. Similar results were obtained with systemic and local injection of a more efficient helper-dependent adenoviral vector, which transduced high levels of hydrolase for at least 2 months, with lesser expression continued up to 1 year. Behavioral tests are now warranted to determine whether such effects can reduce drug-seeking behavior and lower the probability of relapse.Efforts guided by computer-based protein engineering have yielded modified versions of human butyrylcholinesterase (hBChE) that hydrolyze cocaine rapidly enough to deserve consideration for therapeutic use (Sun et al., 2001(Sun et al., , 2002aPancook et al., 2003;Pan et al., 2005;Zheng et al., 2008). We found accelerated cocaine metabolism and blunted cardiovascular effects of cocaine in rats given such enzymes directly (Gao and Brimijoin, 2004) or by adenoviral gene transfer . Others observed that bacterial cocaine hydrolase protected rats against the lethal effects of cocaine (Cooper et al., 2006;Ko et al., 2007). Last, we showed that a catalytically efficient hBChE-albumin fusion protein will abort cocaine-induced seizures and selectively suppress cocaine-induced reinstatement of drug-seeking behavior in rats (Brimijoin et al., 2008).Taken together, the above-mentioned results support the idea of a gene therapy for cocaine addiction based on generating sustained levels of a hydrolase that prevents cocaine access to reward centers in the forebrain. As a step toward that goal, we have now evaluated two viral vectors encoding a quadruple mutant hBChE, with a k cat value 200-fold greater than that of wild-type BChE. Each vector was given systemically or by intracerebral injection to test its effects on cocaine accumulation in brain tissue. We also investigated the ability of such treatments ...

Accelerating Cocaine Metabolism as an Approach to the Treatment of Cocaine Abuse and Toxicity

“…In a subsequent study, Gao and Brimijoin injected these vectors directly into the nucleus accumbens and showed a dramatic increase in BChE activity as a result of those injections [69]. Gao and Brimijoin showed that when treated with the gene-transferred quadruple mutant intravenously, plasma BChE activity was substantially enhanced for up to 7 days and the ability of cocaine to induce c-Fos expression in the caudate nucleus was reduced for up to 7 days [70]. These results show that gene transfer techniques can be applied to the BChE mutants to substantially increase their duration of action, making them viable candidates for the treatment of cocaine abuse.…”

“…While this compound’s duration of action may be over 24 h, any increase in the duration of action would be a significant improvement. A gene therapy approach that has been applied to two of these BChE mutants also shows promise of extending the duration of action for these compounds [62,69,70]. We are not aware of any of these compounds having been tested in humans for safety, which would be a necessary first step.…”

Efficacy of an adenovirus-based anti-cocaine vaccine to reduce cocaine self-administration and reacqusition using a choice procedure in rhesus macaques

“…Inadequate antibody affinity may result in inadequate function and account for the lack of clinical efficacy of previous anti-drug vaccines, such as several for nicotine (e.g., Hatsukami et al, 2011; Tonstad et al, 2013) and TA-CD for cocaine (Kosten et al, 2014). More recently, promising vector-based gene therapies have been developed for cocaine (Anker et al, 2012; Gao and Brimijoin, 2009; Koob et al , 2011). Hicks et al (2011) demonstrated in mice that administration of a first-generation cocaine vaccine that links a cocaine hapten (GNC) to the capsid proteins of a disrupted adenovirus (Ad) (dAd5GNC) increased serum anti-GNC antibody titers and when mice were administered cocaine (25 or 50 μg, i.v.…”

Gene-Delivered Butyrylcholinesterase Is Prophylactic against the Toxicity of Chemical Warfare Nerve Agents and Organophosphorus Compounds

“…The time course did seem to be equally rapid with declines from peak by 92% on day 10 and 98% on day 14. In contrast, prolonged periods of expression up to 1 year have been achieved in rats by using a new adenoviral vector (Gao and Brimijoin, 2009). The new adenoviral vector expressed a human BChE mutant enzyme that hydrolyzed cocaine and offered protection from cocaine toxicity.…”