Marijuana-inspired Painkiller? New Chemical Pathway Discovered
November 27, 2008
Science Daily/Scripps Research Institute
Marijuana can be an effective painkiller, but social issues and unhealthy smoke inhalation complicate its use. As a result, researchers have focused great attention on understanding the biochemical system involved so they might manipulate it by other means. Toward that end, scientists have definitively identified a chemical pathway that, in mice, imitates marijuana's painkilling effect. The work could enable the development of new pain treatments.
Marijuana kills pain by activating a set of proteins known as cannabinoid receptors, which can also regulate appetite, inflammation, and memory. The body also has chemicals known as endocannabinoids that naturally activate these same receptors, namely N-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG).
These natural components of the cannabinoid system remain the focus of intense efforts to develop new treatments not only for chronic pain, but also for obesity, anxiety, and depression. However, until the new paper (citation below) specific methods to study 2-AG signaling have been lacking.
AEA's activity has been well understood for years. In past research, Cravatt and his team identified an enzyme called fatty acid amide hydrolase, or FAAH, that breaks down AEA, effectively reducing its pain killing activity. A number of compounds are now in clinical development that target and breakdown FAAH, allowing AEA to build up, reducing pain. However, FAAH does not control 2-AG metabolism in vivo, and therefore, the potential biological functions and therapeutic potential of this second endocannabinoid have remained largely unknown.
Teasing out 2-AG's specific impacts have proven challenging. Comparable to FAAH, an enzyme called monoacylglycerol lipase (MAGL) breaks down 2-AG. But, despite numerous attempts, no group had been able to develop a chemical that inhibits MAGL specifically.
"The tools—selective and efficacious MAGL inhibitors—just weren't there, " says Jonathan Long, a graduate student of the Scripps Research Kellogg School of Science and Technology who is a member of the Cravatt lab and a first author of the new paper.
But now, a MAGL-specific inhibitor is finally available, thanks to the lab's new work. Key to this success was Activity-Based Protein Profiling, a unique chemical technique the group devised and has used fruitfully in other inhibitor hunts. This system enables the rapid engineering and testing of chemical compounds against many members of enzyme families, in hope of finding effective and selective inhibitors.
For this project, the group developed about 200 compounds and found that one was a highly effective block for MAGL. The scientists dubbed the compound JZL184, named after Long's initials and the order in the series of potential inhibitors tested. JZL184 effectively blocks only MAGL among more than 40 related brain enzymes, which opened the door for the first definitive study of 2-AG's activity.
A New View of 2-AG
Unlike increased AEA, which causes only reduced pain sensation, the team found that MAGL inhibition using JZL184, and the resulting increase in 2-AG concentration, not only reduced pain in mice, but also induced other effects associated with the cannabinoid receptors, namely hypothermia and decreased movement.
"This really does suggest a sort of segregation of labor, if you will," says Cravatt of the differential effects of elevating AEA versus 2-AG as part of the overall function of the cannabinoid system. "That, I think, is a truly unique result."
While treatments based on inhibiting FAAH show great promise for controlling pain, manipulating MAGL levels could also be a boon for treatment development, especially if 2-AG's other effects, such as hypothermia, can be managed.
"There are so many different types of pain," Cravatt says, "that it's possible some types could be more effectively treated with one treatment than another."
This research was supported by the National Institutes of Health, the Helen L. Dorris Child and Adolescent Neuro-Psychiatric Disorder Institute, and the Skaggs Institute for Chemical Biology.
https://www.sciencedaily.com/releases/2008/11/081123150249.htm
Cannabis Use, Effect and Potential Therapy for Alzheimer's, MS and Parkinson's
October 15, 2007
Science Daily/European College of Neuropsychopharmacology
Cannabis (marijuana) is the most widely produced plant-based illicit drug worldwide and the illegal drug most frequently used in Europe. Its use increased in almost all EU countries during the 1990s, in particular among young people, including school students. Cannabis use is highest among 15- to 24-year-olds, with lifetime prevalence ranging for most countries from 20--40% (EMCDDA 2006).
Recently there has been a new surge in the level of concern about potential social and health outcomes of cannabis use, although the available evidence still does not provide a clear-cut understanding of the issues. Intensive cannabis use is correlated with non-drug-specific mental problems, but the question of co-morbidity is intertwined with the questions of cause and effect (EMCDDA 2006). Prevention is of importance in adolescents, which is underlined by evidence that early-onset cannabis-users (pre- to mid-adolescence) have a significantly higher risk of developing drug problems, including dependence (Von Sydow et al., 2002; Chen et al., 2005).
The illegal status and wide-spread use of cannabis made basic and clinical cannabis research difficult in the past decades; on the other hand, it has stimulated efforts to identify the psychoactive constituents of cannabis. As a consequence, the endocannabinoid system was discovered, which was shown to be involved in most physiological systems -- the nervous, the cardiovascular, the reproductive, the immune system, to mention a few.
One of the main roles of endocannabinoids is neuroprotection, but over the last decade they have been found to affect a long list of processes, from anxiety, depression, cancer development, vasodilatation to bone formation and even pregnancy (Panikashvili et al., 2001; Pachter et al., 2006).
Cannabinoids and endocannabinoids are supposed to represent a medicinal treasure trove which waits to be discovered.
Raphael Mechoulam will tell the discovery story of the endocannabinoid system. His research has not only helped us to advance our understanding of cannabis use and its effects, but has also made key contributions with regard to understanding "neuroprotection," and has opened the door for the development of new drugs.
Endocannabinoid system
In the 1960s the constituent of the cannabis plant was discovered -- named tetrahydrocannabinol, or THC -- which causes the 'high' produced by it (Gaoni & Mechoulam, 1964). Thousands of publications have since appeared on THC. Today it is even used as a therapeutic drug against nausea and for enhancing appetite, and, surprisingly, has not become an illicit drug -- apparently cannabis users prefer the plant-based marijuana and hashish.
Two decades later it was found that THC binds to specific receptors in the brain and the periphery and this interaction initiates a cascade of biological processes leading to the well known marijuana effects. It was assumed that a cannabinoid receptor is not formed for the sake of a plant constituent (that by a strange quirk of nature binds to it), but for endogenous brain constituents and that these putative 'signaling' constituents together with the cannabinoid receptors are part of a new biochemical system in the human body, which may affect various physiological actions.
In trying to identify these unknown putative signaling molecules, our research group in the 1990s was successful in isolating 2 such endogenous 'cannabinoid' components -- one from the brain, named anandamide (from the word ´ananda, meaning ´supreme joy´ in Sanscrit), and another one from the intestines named 2-arachidonoyl glycerol (2-AG) (Devane et al., 1992; Mechoulam et al., 1995).
Neuroprotection
The major endocannabinoid (2-AG) has been identified both in the central nervous system and in the periphery. Stressful stimuli -- traumatic brain injury (TBI) for example -- enhance brain 2-AG levels in mice. 2-AG, both of endogenous and exogenous origin, has been shown to be neuroprotective in closed head injury, ischemia and excitotoxicity in mice. These effects may derive from the ability of cannabinoids to act through a variety of biochemical mechanisms. 2-AG also helps repair the blood brain barrier after TBI.
The endocannabinoids act via specific cannabinoid receptors, of which the CB1 receptors are most abundant in the central nervous system. Mice whose CB1 receptors are knocked out display slower functional recovery after TBI and do not respond to treatment with 2-AG. Over the last few years several groups have noted that CB2 receptors are also formed in the brain, particularly as a reaction to numerous neurological diseases, and are apparently activated by the endocannabinoids as a protective mechanism.
Through evolution the mammalian body has developed various systems to guard against damage that may be caused by external attacks. Thus, it has an immune system, whose main role is to protect against protein attacks (microbes, parasites for example) and to reduce the damage caused by them. Analogous biological protective systems have also been developed against non-protein attacks, although they are much less well known than the immune system. Over the last few years the research group of Esther Shohami in collaboration with our group showed that the endocannabinoid system, through various biological routes, lowers the damage caused by brain trauma. Thus, it helps to attenuate the brain edema and the neurological injuries caused by it (Panikashvili et al., 2001; Panikashvili et al., 2006).
Clinical importance
Furthermore it is assumed that the endocannabinoid system may be involved in the pathogenesis of hepatic encephalopathy, a neuropsychiatric syndrome induced by fulminant hepatic failure. Indeed in an animal model the brain levels of 2-AG were found to be elevated. Administration of 2-AG improved a neurological score, activity and cognitive function (Avraham et al., 2006). Activation of the CB2 receptor by a selective agonist also improved the neurological score. The authors concluded that the endocannabinoid system may play an important role in the pathogenesis of hepatic encephalopathy.
Modulation of this system either by exogenous agonists specific for the CB2 receptors or possibly also by antagonists to the CB1 receptors may have therapeutic potential. The endocannabinoid system generally is involved in the protective reaction of the mammalian body to a long list of neurological diseases such as multiple sclerosis, Alzheimer's and Parkinson's disease. Thus, there is hope for novel therapeutic opportunities.
Numerous additional endocannabinoids -- especially various fatty acid ethanolamides and glycerol esters -- are known today and regarded as members of a large ´endocannabinoid family´. Endogenous cannabinoids, the cannabinoid receptors and various enzymes that are involved in their syntheses and degradations comprise the endocannabinoid system.
The endocannabinoid system acts as a guardian against various attacks on the mammalian body.
Conclusion
The above described research concerning the endocannabinoid-system is of importance in both basic science and in therapeutics:
· The discovery of the cannabis plant active constituent has helped advance our understanding of cannabis use and its effects.
· The discovery of the endocannabinoids has been of central importance in establishing the existence of a new biochemical system and its physiological roles -- in particular in neuroprotection.
· These discoveries have opened the door for the development of novel types of drugs, such as THC for the treatment of nausea and for enhancing appetite in cachectic patients.
· The endocannabinoid system is involved in the protective reaction of the mammalian body to a long list of neurological diseases such as multiple sclerosis, Alzheimer's and Parkinson's disease which raises hope for novel therapeutic opportunities for these diseases.
References
Avraham Y, Israeli E, Gabbay E, et al. Endocannabinoids affect neurological and cognitive function in thioacetamide-induced hepatic encephalopathy in mice. Neurobiology of Disease 2006;21:237-245
Chen CY, O´Brien MS, Anthony JC. Who becomes cannabis dependent soon after onset of use" Epidemiological evidence from the United States: 2000-2001. Drug and alcohol dependence 2005;79:11-22
Devane WA, Hanus L, Breuer A, et al. Isolation and structure of a brain constituent that binds to the cannabinoid receptor. Science 1992;258:1946-1949
[EMCDDA 2006] European Monitoring Centre for Drugs and Drug Addiction. The state of the drugs problem in Europe. Annual Report 2006 (http://www.emcdda.europa.eu)
Gaoni Y, Mechoulam R. Isolation, structure and partial synthesis of an active constituent of hashish. J Amer Chem Soc 1964;86:1646-1647
Journal Interview 85: Conversation with Raphael Mechoulam. Addiction 2007;102:887-893
Mechoulam R, Ben-Shabat S, Hanus L, et al. Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors. Biochem Pharmacol 1995;50:83-90
Mechoulam R, Panikashvili D, Shohami E. Cannabinoids and brain injury. Trends Mol Med 2002;8:58-61
Pachter P, Batkai S, Kunos G. The endocannabinoid system as an emerging target of pharmacotherapy. Pharmacol Rev 2006;58:389-462
Panikashvili D, Simeonidou C, Ben-Shabat S, et al. An endogenous cannabinoid (2-AG) is neuroprotective after brain injury. Nature 2001;413:527-531
Panikashvili D, Shein NA, Mechoulam R, et al. The endocannabinoid 2-AG protects the blood brain barrier after closed head injury and inhibits mRNA expression of proinflammatory cytokines. Neurobiol Disease 2006;22:257-264
Von Sydow K, Lieb R, Pfister H, et al. What predicts incident use of cannabis and progression to abuse and dependence" A 4-year prospective examination of risk factors in a community sample of adolescents and young adults. Drug and alcohol dependence 2002;68:49-64
https://www.sciencedaily.com/releases/2007/10/071014163644.htm