Targeting cannabinoid agonists for inflammatory and neuropathic pain.

Abstract

“The cannabinoid receptors CB(1) and CB(2) are class A G-protein-coupled receptors. It is well known that cannabinoid receptor agonists produce relief of pain in a variety of animal models by interacting with cannabinoid receptors. CB(1) receptors are located centrally and peripherally, whereas CB(2) receptors are expressed primarily on immune cells and tissues. A large body of preclinical data supports the hypothesis that either CB(2)-selective agonists or CB(1) agonists acting at peripheral sites, or with limited CNS exposure, will inhibit pain and neuroinflammation without side effects within the CNS. There has been a growing interest in developing cannabinoid agonists. Many new cannabinoid ligands have been synthesized and studied covering a wide variety of novel structural scaffolds. This review focuses on the present development of cannabinoid agonists with an emphasis on selective CB(2) agonists and peripherally restricted CB(1) or CB(1)/CB(2) dual agonists for treatment of inflammatory and neuropathic pain.”

http://www.ncbi.nlm.nih.gov/pubmed/17594182

Targeting CB2 receptors and the endocannabinoid system for the treatment of pain.

Abstract

“The endocannabinoid system consists of the cannabinoid (CB) receptors, CB(1) and CB(2), the endogenous ligands anandamide (AEA, arachidonoylethanolamide) and 2-arachidonoylglycerol (2-AG), and their synthetic and metabolic machinery. The use of cannabis has been described in classical and recent literature for the treatment of pain, but the potential for psychotropic effects as a result of the activation of central CB(1) receptors places a limitation upon its use. There are, however, a number of modern approaches being undertaken to circumvent this problem, and this review represents a concise summary of these approaches, with a particular emphasis upon CB(2) receptor agonists. Selective CB(2) agonists and peripherally restricted CB(1) or CB(1)/CB(2) dual agonists are being developed for the treatment of inflammatory and neuropathic pain, as they demonstrate efficacy in a range of pain models. CB(2) receptors were originally described as being restricted to cells of immune origin, but there is evidence for their expression in human primary sensory neurons, and increased levels of CB(2) receptors reported in human peripheral nerves have been seen after injury, particularly in painful neuromas. CB(2) receptor agonists produce antinociceptive effects in models of inflammatory and nociceptive pain, and in some cases these effects involve activation of the opioid system. In addition, CB receptor agonists enhance the effect of mu-opioid receptor agonists in a variety of models of analgesia, and combinations of cannabinoids and opioids may produce synergistic effects. Antinociceptive effects of compounds blocking the metabolism of anandamide have been reported, particularly in models of inflammatory pain. There is also evidence that such compounds increase the analgesic effect of non-steroidal anti-inflammatory drugs (NSAIDs), raising the possibility that a combination of suitable agents could, by reducing the NSAID dose needed, provide an efficacious treatment strategy, while minimizing the potential for NSAID-induced gastrointestinal and cardiovascular disturbances. Other potential “partners” for endocannabinoid modulatory agents include alpha(2)-adrenoceptor modulators, peroxisome proliferator-activated receptor alpha agonists and TRPV1 antagonists. An extension of the polypharmacological approach is to combine the desired pharmacological properties of the treatment within a single molecule. Hopefully, these approaches will yield novel analgesics that do not produce the psychotropic effects that limit the medicinal use of cannabis.”

http://www.ncbi.nlm.nih.gov/pubmed/19150370

From cannabis to the endocannabinoid system: refocussing attention on potential clinical benefits.

Image result for West Indian Med J

“Cannabis sativa is one of the oldest herbal remedies known to man. Over the past four thousand years, it has been used for the treatment of numerous diseases but due to its psychoactive properties, its current medicinal usage is highly restricted. In this review, we seek to highlight advances made over the last forty years in the understanding of the mechanisms responsible for the effects of cannabis on the human body and how these can potentially be utilized in clinical practice. During this time, the primary active ingredients in cannabis have been isolated, specific cannabinoid receptors have been discovered and at least five endogenous cannabinoid neurotransmitters (endocannabinoids) have been identified. Together, these form the framework of a complex endocannabinoid signalling system that has widespread distribution in the body and plays a role in regulating numerous physiological processes within the body. Cannabinoid ligands are therefore thought to display considerable therapeutic potential and the drive to develop compounds that can be targeted to specific neuronal systems at low enough doses so as to eliminate cognitive side effects remains the ‘holy grail’ of endocannabinoid research.”

http://www.ncbi.nlm.nih.gov/pubmed/23155985

The non-psychoactive cannabis constituent cannabidiol is an orally effective therapeutic agent in rat chronic inflammatory and neuropathic pain.

Abstract

“Cannabidiol, the major psycho-inactive component of cannabis, has substantial anti-inflammatory and immunomodulatory effects. This study investigated its therapeutic potential on neuropathic (sciatic nerve chronic constriction) and inflammatory pain (complete Freund’s adjuvant intraplantar injection) in rats. In both models, daily oral treatment with cannabidiol (2.5-20 mg/kg to neuropathic and 20 mg/kg to adjuvant-injected rats) from day 7 to day 14 after the injury, or intraplantar injection, reduced hyperalgesia to thermal and mechanical stimuli. In the neuropathic animals, the anti-hyperalgesic effect of cannabidiol (20 mg/kg) was prevented by the vanilloid antagonist capsazepine (10 mg/kg, i.p.), but not by cannabinoid receptor antagonists. Cannabidiol’s activity was associated with a reduction in the content of several mediators, such as prostaglandin E(2) (PGE(2)), lipid peroxide and nitric oxide (NO), and in the over-activity of glutathione-related enzymes. Cannabidiol only reduced the over-expression of constitutive endothelial NO synthase (NOS), without significantly affecting the inducible form (iNOS) in inflamed paw tissues. Cannabidiol had no effect on neuronal and iNOS isoforms in injured sciatic nerve. The compound’s efficacy on neuropathic pain was not accompanied by any reduction in nuclear factor-kappaB (NF-kappaB) activation and tumor necrosis factor alpha (TNFalpha) content. The results indicate a potential for therapeutic use of cannabidiol in chronic painful states.”

http://www.ncbi.nlm.nih.gov/pubmed/17157290

Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities.

Philosophical Transactions of the Royal Society B: Biological Sciences: 367 (1607)

“Human tissues express cannabinoid CB(1) and CB(2) receptors that can be activated by endogenously released ‘endocannabinoids’ or exogenously administered compounds in a manner that reduces the symptoms or opposes the underlying causes of several disorders in need of effective therapy. Three medicines that activate cannabinoid CB(1)/CB(2) receptors are now in the clinic: Cesamet (nabilone), Marinol (dronabinol; Δ(9)-tetrahydrocannabinol (Δ(9)-THC)) and Sativex (Δ(9)-THC with cannabidiol). These can be prescribed for the amelioration of chemotherapy-induced nausea and vomiting (Cesamet and Marinol), stimulation of appetite (Marinol) and symptomatic relief of cancer pain and/or management of neuropathic pain and spasticity in adults with multiple sclerosis (Sativex). This review mentions several possible additional therapeutic targets for cannabinoid receptor agonists. These include other kinds of pain, epilepsy, anxiety, depression, Parkinson’s and Huntington’s diseases, amyotrophic lateral sclerosis, stroke, cancer, drug dependence, glaucoma, autoimmune uveitis, osteoporosis, sepsis, and hepatic, renal, intestinal and cardiovascular disorders. It also describes potential strategies for improving the efficacy and/or benefit-to-risk ratio of these agonists in the clinic. These are strategies that involve (i) targeting cannabinoid receptors located outside the blood-brain barrier, (ii) targeting cannabinoid receptors expressed by a particular tissue, (iii) targeting upregulated cannabinoid receptors, (iv) selectively targeting cannabinoid CB(2) receptors, and/or (v) adjunctive ‘multi-targeting’.”  https://www.ncbi.nlm.nih.gov/pubmed/23108552

“Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities”  http://rstb.royalsocietypublishing.org/content/367/1607/3353.long

The Therapeutic Potential of Cannabis and Cannabinoids

“Background

Cannabis-based medications have been a topic of intense study since the endogenous cannabinoid system was discovered two decades ago. In 2011, for the first time, a cannabis extract was approved for clinical use in Germany.”

“Therapeutic potential

Cannabis preparations exert numerous therapeutic effects. They have antispastic, analgesic, antiemetic, neuroprotective, and anti-inflammatory actions, and are effective against certain psychiatric diseases. Currently, however, only one cannabis extract is approved for use. It contains THC and CBD in a 1:1 ratio and was licensed in 2011 for treatment of moderate to severe refractory spasticity in multiple sclerosis (MS). In June 2012 the German Joint Federal Committee (JFC, Gemeinsamer Bundesausschuss) pronounced that the cannabis extract showed a “slight additional benefit” for this indication and granted a temporary license valid up to 2015.”

“The cannabis extract, which goes by the generic name nabiximols, has been approved by regulatory bodies in Germany and elsewhere for use as a sublingual spray. In the USA, dronabinol has been licensed since 1985 for the treatment of nausea and vomiting caused by cytostatic therapy and since 1992 for loss of appetite in HIV/Aids-related cachexia. In Great Britain, nabilone has been sanctioned for treatment of the side effects of chemotherapy in cancer patients.”

Results

“Cannabis-based medications exert their effects mainly through the activation of cannabinoid receptors (CB1 and CB2). More than 100 controlled clinical trials of cannabinoids or whole-plant preparations for various indications have been conducted since 1975. The findings of these trials have led to the approval of cannabis-based medicines (dronabinol, nabilone, and a cannabis extract [THC:CBD=1:1]) in several countries. In Germany, a cannabis extract was approved in 2011 for the treatment of moderate to severe refractory spasticity in multiple sclerosis. It is commonly used off label for the treatment of anorexia, nausea, and neuropathic pain. Patients can also apply for government permission to buy medicinal cannabis flowers for self-treatment under medical supervision. The most common side effects of cannabinoids are tiredness and dizziness (in more than 10% of patients), psychological effects, and dry mouth. Tolerance to these side effects nearly always develops within a short time. Withdrawal symptoms are hardly ever a problem in the therapeutic setting.”

Conclusion

“There is now clear evidence that cannabinoids are useful for the treatment of various medical conditions.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3442177/

 

Therapeutic aspects of cannabis and cannabinoids

The British Journal of Psychiatry

“HISTORY OF THERAPEUTIC USE

The first formal report of cannabis as a medicine appeared in China nearly 5000 years ago when it was recommended for malaria, constipation, rheumatic pains and childbirth and, mixed with wine, as a surgical analgesic. There are subsequent records of its use throughout Asia, the Middle East, Southern Africa and South America. Accounts by Pliny, Dioscorides and Galen remained influential in European medicine for 16 centuries.”

“It was not until the 19th century that cannabis became a mainstream medicine in Britain. W. B. O’Shaughnessy, an Irish scientist and physician, observed its use in India as an analgesic, anticonvulsant, anti-spasmodic, anti-emetic and hypnotic. After toxicity experiments on goats and dogs, he gave it to patients and was impressed with its muscle-relaxant, anticonvulsant and analgesic properties, and recorded its use-fulness as an anti-emetic.”

“After these observations were published in 1842, medicinal use of cannabis expanded rapidly. It soon became available ‘over the counter’ in pharmacies and by 1854 it had found its way into the United States Dispensatory. The American market became flooded with dozens of cannabis-containing home remedies.”

“Cannabis was outlawed in 1928 by ratification of the 1925 Geneva Convention on the manufacture, sale and movement of dangerous drugs. Prescription remained possible until final prohibition under the 1971 Misuse of Drugs Act, against the advice of the Advisory Committee on Drug Dependence.”

“In the USA, medical use was effectively ruled out by the Marijuana Tax Act 1937. This ruling has been under almost constant legal challenge and many special dispensations were made between 1976 and 1992 for individuals to receive ‘compassionate reefers’. Although this loophole has been closed, a 1996 California state law permits cultivation or consumption of cannabis for medical purposes, if a doctor provides a written endorsement. Similar arrangements apply in Italy and Canberra, Australia.”

“Results and Conclusions Cannabis and some cannabinoids are effective anti-emetics and analgesics and reduce intra-ocular pressure. There is evidence of symptom relief and improved well-being in selected neurological conditions, AIDS and certain cancers. Cannabinoids may reduce anxiety and improve sleep. Anticonvulsant activity requires clarification. Other properties identified by basic research await evaluation. Standard treatments for many relevant disorders are unsatisfactory. Cannabis is safe in overdose but often produces unwanted effects, typically sedation, intoxication, clumsiness, dizziness, dry mouth, lowered blood pressure or increased heart rate. The discovery of specific receptors and natural ligands may lead to drug developments. Research is needed to optimise dose and route of administration, quantify therapeutic and adverse effects, and examine interactions.”

http://bjp.rcpsych.org/content/178/2/107.long

The therapeutic potential of novel cannabinoid receptors.

Cover image

“Cannabinoids produce a plethora of biological effects, including the modulation of neuronal activity through the activation of CB(1) receptors and of immune responses through the activation of CB(2) receptors. The selective targeting of either of these two receptor subtypes has clear therapeutic value. Recent evidence indicates that some of the cannabinomimetic effects previously thought to be produced through CB(1) and/or CB(2) receptors, be they on neuronal activity, on the vasculature tone or immune responses, still persist despite the pharmacological blockade or genetic ablation of CB(1) and/or CB(2) receptors. This suggests that additional cannabinoid and cannabinoid-like receptors exist. Here we will review this evidence in the context of their therapeutic value and discuss their true belonging to the endocannabinoid signaling system.”  http://www.ncbi.nlm.nih.gov/pubmed/19248809

“The therapeutic potential of novel cannabinoid receptors”  http://www.sciencedirect.com/science/article/pii/S0163725809000266

Cannabinoids, Endocannabinoids, and Related Analogs in Inflammation.

“This review covers reports published in the last 5 years on the anti-inflammatory activities of all classes of cannabinoids, including phytocannabinoids such as tetrahydrocannabinol and cannabidiol, synthetic analogs such as ajulemic acid and nabilone, the endogenous cannabinoids anandamide and related compounds, namely, the elmiric acids, and finally, noncannabinoid components of Cannabis that show anti-inflammatory action. It is intended to be an update on the topic of the involvement of cannabinoids in the process of inflammation. A possible mechanism for these actions is suggested involving increased production of eicosanoids that promote the resolution of inflammation. This differentiates these cannabinoids from cyclooxygenase-2 inhibitors that suppress the synthesis of eicosanoids that promote the induction of the inflammatory process.”

 

“INTRODUCTION

This review is intended to be an update on the topic of the involvement of cannabinoids in the process of inflammation. Other reviews cover certain aspects of this subject and the reader is referred to them for a discussion of earlier reports. In this review are reports published in the last 5 years on the activities of all classes of cannabinoids, including the endogenous cannabinoids such as anandamide, related compounds such as the elmiric acids (EMAs), and noncannabinoid components of Cannabis that show anti-inflammatory action. An interesting recently published example of the latter one is caryophyllene, an abundant component of Cannabis oil that shows anti-inflammatory activity and has high affinity for cannabinoid receptor 2 (CB2; 5).”

 

“Phytocannabinoids: Tetrahydrocannabinol and Cannabidiol”

 

“PLANT PREPARATIONS AND NONCANNABINOID CONSTITUENTS OF CANNABIS”

“Cannabis sativa is a complex botanical, and it is not unlikely that the therapeutic benefits of marijuana are due to some of the more than 60 cannabinoids and 200–250 noncannabinoid constituents of the plant. One noncannabinoid, the geranylated flavone cannflavin A (Fig. 5), is 30 times more potent than aspirin as an inhibitor of prostaglandin E2 . These potentially important findings have been overlooked, as most attention in marijuana research has been directed to the analgesic effects of the plant and to mechanisms of psychoactivity. A further example that this line of inquiry has remained dormant is a series of overlooked observations, which demonstrate potent anti-inflammatory actions of a crude marijuana extract and of the nonpsychoactive Cannabis constituents, CBD, cannabinol, and cannabichromene in the carrageenan paw edema model of acute inflammation in rats. Volatile oil products of the plant also have biological activity. Thus, pyrolysis products may add to the therapeutic properties of smoked marijuana. Several of the most abundant cannabinoid and noncannabinoid constituents of C. sativa are nonpsychoactive.”

“Flavonoids are ubiquitous plant phenolic compounds that consist of two aromatic rings linked by a three carbon bridge. They are attracting interest because of their antioxidant, antitumor, anti-inflammatory, and antimicrobial activities. The flavone luteolin, a constituent of C. sativa, is also found in spices and in vegetables such as celery and green pepper. When added to peripheral blood mononuclear cells in vitro, luteolin suppresses production of the inflammatory cytokines TNFα, IL-1b, and IL-6, actions that relate to a selective reduction in numbers of monocytes. Perhaps more importantly, luteolin inhibits growth of Plasmodium falciparum in vitro and protects against induction of colon cancer in mice.”

“CONCLUSIONS

Possibly the very earliest literature reference on Cannabis describes its use as an anti-inflammatory agent. The Chinese emperor Shen-nung (ca. 2000 B.C.), in a work called Pen-ts’ao Ching, noted many of the effects of Cannabis in humans. Among other properties, it was claimed that cannabis “undoes rheumatism”, suggesting possible anti-inflammatory effects. The reports described in this review of the current literature provide support for the claims made by the ancient Chinese healers. These more recent publications include relief from chronic neuropathic pain, fibromyalgia, rheumatoid arthritis, and postoperative pain. In addition, a large body of preclinical data on all classes of cannabinoids, including the endogenous examples, point to a variety of therapeutic targets for cannabinoids and important roles for the endocannabinoids in the physiology of inflammation.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2664885/

The Endocannabinoid System as an Emerging Target of Pharmacotherapy

Abstract

“The recent identification of cannabinoid receptors and their endogenous lipid ligands has triggered an exponential growth of studies exploring the endocannabinoid system and its regulatory functions in health and disease. Such studies have been greatly facilitated by the introduction of selective cannabinoid receptor antagonists and inhibitors of endocannabinoid metabolism and transport, as well as mice deficient in cannabinoid receptors or the endocannabinoid-degrading enzyme fatty acid amidohydrolase. In the past decade, the endocannabinoid system has been implicated in a growing number of physiological functions, both in the central and peripheral nervous systems and in peripheral organs. More importantly, modulating the activity of the endocannabinoid system turned out to hold therapeutic promise in a wide range of disparate diseases and pathological conditions, ranging from mood and anxiety disorders, movement disorders such as Parkinson’s and Huntington’s disease, neuropathic pain, multiple sclerosis and spinal cord injury, to cancer, atherosclerosis, myocardial infarction, stroke, hypertension, glaucoma, obesity/metabolic syndrome, and osteoporosis, to name just a few. An impediment to the development of cannabinoid medications has been the socially unacceptable psychoactive properties of plant-derived or synthetic agonists, mediated by CB(1) receptors. However, this problem does not arise when the therapeutic aim is achieved by treatment with a CB(1) receptor antagonist, such as in obesity, and may also be absent when the action of endocannabinoids is enhanced indirectly through blocking their metabolism or transport. The use of selective CB(2) receptor agonists, which lack psychoactive properties, could represent another promising avenue for certain conditions. The abuse potential of plant-derived cannabinoids may also be limited through the use of preparations with controlled composition and the careful selection of dose and route of administration. The growing number of preclinical studies and clinical trials with compounds that modulate the endocannabinoid system will probably result in novel therapeutic approaches in a number of diseases for which current treatments do not fully address the patients’ need. Here, we provide a comprehensive overview on the current state of knowledge of the endocannabinoid system as a target of pharmacotherapy.”

Future Directions

“The length of this review, necessitated by the steady growth in the number of indications for the potential therapeutic use of cannabinoid-related medications, is a clear sign of the emerging importance of this field. This is further underlined by the quantity of articles in the public database dealing with the biology of cannabinoids, which numbered ∼200 to 300/year throughout the 1970s to reach an astonishing 5900 in 2004. The growing interest in the underlying science has been matched by a growth in the number of cannabinoid drugs in pharmaceutical development from two in 1995 to 27 in 2004, with the most actively pursued therapeutic targets being pain, obesity, and multiple sclerosis (Hensen, 2005). As in any rapidly growing area of research, not all the leads will turn out to be useful or even valid. Nevertheless, it is safe to predict that new therapeutic agents that affect the activity of the endocannaboinoid system will emerge and become members of our therapeutic armamentarium. The plant-derived cannabinoid preparation Sativex has already gained regulatory approval in Canada for the treatment of spasticity and pain associated with multiple sclerosis, and the CB1 receptor antagonist rimonabant has been approved in Europe and is awaiting Food and Drug Administration approval in the United States for the treatment of the metabolic syndrome. Undoubtedly, these will be followed by new and improved compounds aimed at the same or additional targets in the endocannabinoid system. However, it may be only after the widespread therapeutic use of such compounds that some important side effects will emerge. Although this occurrence would be undesirable from a health care perspective, such side effects may shed further light on the biological functions of endocannabinoids in health and disease.”

http://pharmrev.aspetjournals.org/content/58/3/389.long