Pharmacological evaluation of a novel cannabinoid 2 (CB2) ligand, PF-03550096, in vitro and in vivo by using a rat model of visceral hypersensitivity

Endocannabinoids regulate enteric neuron-glia networks and visceral hypersensitivity following inflammation through a glial-dependent mechanism

Acute gastrointestinal (GI) inflammation induces neuroplasticity that produces long-lasting changes in gut motor function and pain. The endocannabinoid system is an attractive target to correct pain and dysmotility, but how inflammation changes endocannabinoid control over cellular communication in enteric neurocircuits is not understood. Enteric glia modulate gut neurons that control motility and pain and express monoacylglycerol lipase (MAGL) which controls endocannabinoid availability. We used a combination of in situ calcium imaging, chemogenetics, and selective drugs to study how endocannabinoid mechanisms affect glial responses and subsequent enteric neuron activity in health and following colitis in Wnt1Cre;GCaMP5g-tdT;GFAP::hM3Dq mice. Trpv1Cre;GCaMP5gtdT mice were used to study nociceptor sensitivity and Sox10CreERT2;Mgllf/f mice were used to test the role of glial MAGL in visceral pain. The data show that endocannabinoid signaling regulates neuro-glial signaling in gut neurocircuits in a sexually dimorphic manner. Inhibiting MAGL in healthy samples decreased glial responsiveness but this effect was lost in females following colitis and converted to an excitatory effect in males. Manipulating CB1 and CB2 receptors revealed further sex differences amongst neuro-glia signaling that were impacted following inflammation. Inflammation increased gut nociceptor sensitivity in both sexes but only females exhibited visceral hypersensitivity in vivo. Blocking MAGL normalized nociceptor responses in vitro and deleting glial Mgll in vivo rescued visceral hypersensitivity in females. These results show that sex and inflammation impact endocannabinoid mechanisms that regulate intercellular enteric glia-neuron communication. Further, targeting glial MAGL could provide therapeutic benefits for visceral nociception in a sex-dependent manner.

A systematic review of novel cannabinoids and their targets: Insights into the significance of structure in activity

To provide a comprehensive framework of the current information on the potency and efficacy of interaction between phyto- and synthetic cannabinoids and their respective receptors, an electronic search of the PubMed, Scopus, and EMBASE literature was performed. Experimental studies included reports of mechanistic data providing affinity, efficacy, and half-maximal effective concentration (EC50). Among the 108 included studies, 174 structures, and 16 targets were extracted. The most frequent ligands belonged to the miscellaneous category with 40.2% followed by phytocannabinoid-similar, indole-similar, and pyrrole-similar structures with an abundance of 17.8%, 16.6%, and 12% respectively. 64.8% of structures acted as agonists, 17.1 % appeared as inverse agonists, 10.8% as antagonists, and 7.2% of structures were reported with antagonist/inverse agonist properties. Our outcomes identify the affinity, EC50, and efficacy of the interactions between cannabinoids and their corresponding receptors and the subsequent response, evaluated in the available evidence. Considering structures' significance and very important effects of on the activities, the obtained results also provide clues to drug repurposing.

Goods and Bads of the Endocannabinoid System as a Therapeutic Target: Lessons Learned after 30 Years

The cannabis derivative marijuana is the most widely used recreational drug in the Western world and is consumed by an estimated 83 million individuals (∼3% of the world population). In recent years, there has been a marked transformation in society regarding the risk perception of cannabis, driven by its legalization and medical use in many states in the United States and worldwide. Compelling research evidence and the Food and Drug Administration cannabis-derived cannabidiol approval for severe childhood epilepsy have confirmed the large therapeutic potential of cannabidiol itself, Δ9-tetrahydrocannabinol and other plant-derived cannabinoids (phytocannabinoids). Of note, our body has a complex endocannabinoid system (ECS)-made of receptors, metabolic enzymes, and transporters-that is also regulated by phytocannabinoids. The first endocannabinoid to be discovered 30 years ago was anandamide (N-arachidonoyl-ethanolamine); since then, distinct elements of the ECS have been the target of drug design programs aimed at curing (or at least slowing down) a number of human diseases, both in the central nervous system and at the periphery. Here a critical review of our knowledge of the goods and bads of the ECS as a therapeutic target is presented to define the benefits of ECS-active phytocannabinoids and ECS-oriented synthetic drugs for human health. SIGNIFICANCE STATEMENT: The endocannabinoid system plays important roles virtually everywhere in our body and is either involved in mediating key processes of central and peripheral diseases or represents a therapeutic target for treatment. Therefore, understanding the structure, function, and pharmacology of the components of this complex system, and in particular of key receptors (like cannabinoid receptors 1 and 2) and metabolic enzymes (like fatty acid amide hydrolase and monoacylglycerol lipase), will advance our understanding of endocannabinoid signaling and activity at molecular, cellular, and system levels, providing new opportunities to treat patients.

Efficacy and safety of olorinab, a full agonist of the cannabinoid receptor 2, for the treatment of abdominal pain in patients with irritable bowel syndrome: Results from a phase 2b randomized placebo-controlled trial (CAPTIVATE)

BACKGROUND

Olorinab is a highly selective, peripherally acting, full agonist of cannabinoid receptor 2. This study assessed the efficacy and safety of olorinab to treat abdominal pain in patients with irritable bowel syndrome with diarrhea (IBS-D) and constipation (IBS-C).

METHODS

CAPTIVATE was a phase 2b, randomized, double-blind, placebo-controlled, parallel-group trial. Eligible participants aged 18-70 years with IBS-C and IBS-D diagnosed per Rome IV received olorinab 10 mg, 25 mg, or 50 mg three times daily (TID) or placebo TID for 12 weeks. The primary endpoint was the change in patient-reported average abdominal pain score (AAPS) from baseline to Week 12.

KEY RESULTS

A total of 273 participants were randomized to receive olorinab 10 mg (n = 67), olorinab 25 mg (n = 67), olorinab 50 mg (n = 69), or placebo (n = 70). Although a treatment response was observed across all groups, the weekly change in average AAPS from baseline to Week 12 was not significantly different between placebo and any olorinab dose. In a prespecified subgroup analysis of participants with a baseline AAPS ≥6.5, olorinab 50 mg (n = 35) significantly improved AAPS compared with placebo (n = 30) (p = 0.014). Adverse event rates were comparable between olorinab and placebo and there were no reported serious adverse events or deaths.

CONCLUSION AND INFERENCES

Although olorinab was well-tolerated and improved weekly AAPS, the primary endpoint was not met. However, in participants with moderate-to-severe pain at baseline (AAPS ≥6.5), olorinab 50 mg significantly improved weekly AAPS compared with placebo.

CLINICALTRIALS

gov: NCT04043455.

Targeting the endocannabinoid system for the treatment of abdominal pain in irritable bowel syndrome

The management of visceral pain in patients with disorders of gut-brain interaction, notably irritable bowel syndrome, presents a considerable clinical challenge, with few available treatment options. Patients are increasingly using cannabis and cannabinoids to control abdominal pain. Cannabis acts on receptors of the endocannabinoid system, an endogenous system of lipid mediators that regulates gastrointestinal function and pain processing pathways in health and disease. The endocannabinoid system represents a logical molecular therapeutic target for the treatment of pain in irritable bowel syndrome. Here, we review the physiological and pathophysiological functions of the endocannabinoid system with a focus on the peripheral and central regulation of gastrointestinal function and visceral nociception. We address the use of cannabinoids in pain management, comparing them to other treatment modalities, including opioids and neuromodulators. Finally, we discuss emerging therapeutic candidates targeting the endocannabinoid system for the treatment of pain in irritable bowel syndrome.

The effect of medical cannabis in inflammatory bowel disease: analysis from the UK Medical Cannabis Registry

OBJECTIVES

Cannabis-based medicinal products (CBMPs) have shown promising preclinical activity in inflammatory bowel disease (IBD). However, clinical trials have not demonstrated effects on inflammation. This study aims to analyze changes in health-related quality of life (HRQoL) and adverse events in IBD patients prescribed CBMPs.

METHODS

A case series from the UK Medical Cannabis Registry was performed. Primary outcomes included changes from baseline in the Short Inflammatory Bowel Disease Questionnaire (SIBDQ), Generalized Anxiety Disorder-7 (GAD-7), Single-Item Sleep Quality Scale (SQS), and EQ-5D-5L Index score at 1 and 3 months. Statistical significance was defined using p < 0.050.

RESULTS

Seventy-six patients with Crohn's disease (n = 51; 67.11%) and ulcerative colitis (n = 25; 32.89%) were included. The median baseline SIBDQ score improved at 1 and 3 months. EQ-5D-5L index values, GAD-7, and SQS also improved after 3 months (p < 0.050). Sixteen (21.05%) patients reported adverse events with the majority being classified as mild to moderate in severity.

CONCLUSION

Patients treated with CBMPs for refractory symptoms of Crohn's disease and ulcerative colitis demonstrated a short-term improvement in IBD-specific and general HRQoL. Prior cannabis consumers reported greater improvement compared to cannabis-naïve individuals.

The Enteric Glia and Its Modulation by the Endocannabinoid System, a New Target for Cannabinoid-Based Nutraceuticals?

The enteric nervous system (ENS) is a part of the autonomic nervous system that intrinsically innervates the gastrointestinal (GI) tract. Whereas enteric neurons have been deeply studied, the enteric glial cells (EGCs) have received less attention. However, these are immune-competent cells that contribute to the maintenance of the GI tract homeostasis through supporting epithelial integrity, providing neuroprotection, and influencing the GI motor function and sensation. The endogenous cannabinoid system (ECS) includes endogenous classical cannabinoids (anandamide, 2-arachidonoylglycerol), cannabinoid-like ligands (oleoylethanolamide (OEA) and palmitoylethanolamide (PEA)), enzymes involved in their metabolism (FAAH, MAGL, COX-2) and classical (CB1 and CB2) and non-classical (TRPV1, GPR55, PPAR) receptors. The ECS participates in many processes crucial for the proper functioning of the GI tract, in which the EGCs are involved. Thus, the modulation of the EGCs through the ECS might be beneficial to treat some dysfunctions of the GI tract. This review explores the role of EGCs and ECS on the GI tract functions and dysfunctions, and the current knowledge about how EGCs may be modulated by the ECS components, as possible new targets for cannabinoids and cannabinoid-like molecules, particularly those with potential nutraceutical use.

Cannabis and Cannabis Derivatives for Abdominal Pain Management in Inflammatory Bowel Disease

For centuries, cannabis and its components have been used to manage a wide variety of symptoms associated with many illnesses. Gastrointestinal (GI) diseases are no exception in this regard. Individuals suffering from inflammatory bowel disease (IBD) are among those who have sought out the ameliorating properties of this plant. As legal limitations of its use have eased, interest has grown from both patients and their providers regarding the potential of cannabis to be used in the clinical setting. Similarly, a growing number of animal and human studies have been undertaken to evaluate the impact of cannabis and cannabinoid signaling elements on the natural history of IBD and its associated complications. There is little clinical evidence supporting the ability of cannabis or related products to treat the GI inflammation underlying these disorders. However, 1 recurring theme from both animal and human studies is that these agents have a significant impact on several IBD-related symptoms, including abdominal pain. In this review, we discuss the role of cannabis and cannabinoid signaling in visceral pain perception, what is currently known regarding the efficacy of cannabis and its derivatives for managing pain, related symptoms and inflammation in IBD, and what work remains to effectively utilize cannabis and its derivatives in the clinical setting.

Olorinab (APD371), a peripherally acting, highly selective, full agonist of the cannabinoid receptor 2, reduces colitis-induced acute and chronic visceral hypersensitivity in rodents

ABSTRACT

Abdominal pain is a key symptom of inflammatory bowel disease and irritable bowel syndrome, for which there are inadequate therapeutic options. We tested whether olorinab-a highly selective, full agonist of the cannabinoid receptor 2 (CB2)-reduced visceral hypersensitivity in models of colitis and chronic visceral hypersensitivity (CVH). In rodents, colitis was induced by intrarectal administration of nitrobenzene sulfonic acid derivatives. Control or colitis animals were administered vehicle or olorinab (3 or 30 mg/kg) twice daily by oral gavage for 5 days, starting 1 day before colitis induction. Chronic visceral hypersensitivity mice were administered olorinab (1, 3, 10, or 30 mg/kg) twice daily by oral gavage for 5 days, starting 24 days after colitis induction. Visceral mechanosensitivity was assessed in vivo by quantifying visceromotor responses (VMRs) to colorectal distension. Ex vivo afferent recordings determined colonic nociceptor firing evoked by mechanical stimuli. Colitis and CVH animals displayed significantly elevated VMRs to colorectal distension and colonic nociceptor hypersensitivity. Olorinab treatment significantly reduced VMRs to control levels in colitis and CVH animals. In addition, olorinab reduced nociceptor hypersensitivity in colitis and CVH states in a concentration- and CB2-dependent manner. By contrast, olorinab did not alter VMRs nor nociceptor responsiveness in control animals. Cannabinoid receptor 2 mRNA was detected in colonic tissue, particularly within epithelial cells, and dorsal root ganglia, with no significant differences between healthy, colitis, and CVH states. These results demonstrate that olorinab reduces visceral hypersensitivity through CB2 agonism in animal models, suggesting that olorinab may provide a novel therapy for inflammatory bowel disease- and irritable bowel syndrome-associated abdominal pain.

Pharmacology, Clinical Effects, and Therapeutic Potential of Cannabinoids for Gastrointestinal and Liver Diseases

Cannabis and cannabinoids (such as tetrahydrocannabinol and cannabidiol) are frequently used to relieve gastrointestinal symptoms. Cannabinoids have effects on the immune system and inflammatory responses, as well as neuromuscular and sensory functions of digestive organs, including pancreas and liver. Cannabinoids can cause hyperemesis and cyclic vomiting syndrome, but they might also be used to reduce gastrointestinal, pancreatic, or hepatic inflammation, as well as to treat motility, pain, and functional disorders. Cannabinoids activate cannabinoid receptors, which inhibit release of transmitters from presynaptic neurons and also inhibit diacylglycerol lipase alpha, to prevent synthesis of the endocannabinoid 2-arachidonoyl glycerol. However, randomized trials are needed to clarify their effects in patients; these compounds can have adverse effects on the central nervous system (such as somnolence and psychosis) or the developing fetus, when used for nausea and vomiting during pregnancy. Cannabinoid-based therapies can also hide symptoms and disease processes, such as in patients with inflammatory bowel diseases. It is important for gastroenterologists and hepatologists to understand cannabinoid mechanisms, effects, and risks.

Tetrahydrocannabinol (THC) Exacerbates Inflammatory Bowel Disease in Adolescent and Adult Female Rats

Inflammatory Bowel Disease (IBD) is a life-long disorder that often begins between the ages of 15 and 30. Anecdotal reports suggest cannabinoids may be an effective treatment. This study sought to determine whether home cage wheel running is an effective method to assess IBD, and whether Tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis, can restore wheel running depressed by IBD. Adolescent and adult female Sprague-Dawley rats were individually housed in a cage with a running wheel. Rats were injected with trinitrobenzene sulphonic acid (TNBS) into the rectum to induce IBD-like symptoms. One day later, both vehicle and TNBS treated rats were injected with a low dose of THC (0.32 mg/kg, s.c.) or vehicle. Administration of TNBS depressed wheel running in adolescent and adult rats. No antinociceptive effect of THC was evident when administered 1 day after TNBS. In fact, administration of THC prolonged TNBS-induced depression of wheel running for over 5 days in adolescent and adult rats. These results show that home cage wheel running is depressed by TNBS-induced IBD, making it a useful tool to evaluate the behavioral consequences of IBD, and that administration of THC, instead of producing antinociception, exacerbates TNBS-induced IBD. PERSPECTIVE: This article advances research on inflammatory bowel disease in two important ways: 1) Home cage wheel running is a new and sensitive tool to assess the behavioral consequences of IBD in adolescent and adult rats; and 2) Administration of the cannabinoid THC exacerbates the negative behavioral effects of IBD.

Anti-inflammatory and antinociceptive effects of the selective cannabinoid CB2 receptor agonist ABK5

Cannabinoid receptors are a potential target for anti-inflammatory and pain therapeutics. There are two subtypes, CB1 and CB2, and Δ9-tetrahydrocannabinol activates both of them, providing an analgesic effect but also psychoactive side effects. The psychoactive side effects are considered to be caused by activation of CB1, but not CB2. ABK5 is a CB2 subtype selective agonist that has a very different structure from known cannabinoid receptor agonists. Here, we report anti-inflammatory effects of ABK5 using the T-cell line Jurkat cells, and antinociceptive effect in an inflammatory pain model in rats. Production of the cytokines IL-2 and TNF-α was measured in stimulated Jurkat cells and MOLT-4 cells, and CXCL12-mediated chemotaxis of Jurkat cells was evaluated by a transwell migration assay. Anti-inflammatory and antinociceptive effects of ABK5 were also evaluated in a hindpaw CFA model in rats. ABK5 significantly decreased production of IL-2 and TNF-α measured as both mRNA and protein levels, and reduced chemotaxis towards CXCL12. It also attenuated edema and increased mechanical threshold in the hindpaw of CFA-treated rats. These results suggest that ABK5 is a good lead compound for the development of potential anti-inflammatory and analgesic agents.

Safety, Pharmacokinetics, and Efficacy of Olorinab, a Peripherally Acting, Highly Selective, Full Agonist of the Cannabinoid Receptor 2, in a Phase 2a Study of Patients With Chronic Abdominal Pain Associated With Crohn's Disease

Background

This randomized, open-label phase 2a study investigated the safety/tolerability, pharmacokinetics, and efficacy of olorinab-a highly selective, peripherally acting, full agonist of the cannabinoid receptor 2-in patients with Crohn's disease (CD) experiencing abdominal pain.

Methods

Eligible subjects 18-80 years of age with quiescent to mildly active CD were randomized to receive olorinab 25 or 100 mg three times daily for 8 weeks. The primary objective was to assess safety/tolerability.

Results

Fourteen subjects received olorinab 25 mg (N = 6) or 100 mg (N = 8). Ten subjects [4 (67%) in the 25-mg group and 6 (75%) in the 100-mg group] reported a total of 34 treatment-emergent adverse events (TEAEs; 32 grade 1/2, not serious events; 2 grade 3, serious, not treatment-related events). No dose reductions or discontinuations due to TEAEs or deaths were reported. Dose-proportional increases in olorinab exposure from 25 to 100 mg were observed, with minimal accumulation at both doses. At week 8, the mean (SD) change from baseline in average abdominal pain score at peak olorinab plasma concentrations was -4.61 (1.77) in the 25-mg group (P = 0.0043) and -4.57 (2.17) in the 100-mg group (P = 0.0036). The change from baseline at week 8 in the mean (SD) number of pain-free days per week was +1.60 (2.61) in the 25-mg group and +2.33 (3.62) in the 100-mg group. No subject required pain medication on study.

Conclusions

Patients with quiescent to mildly active CD receiving olorinab experienced mild-to-moderate adverse events and an improvement in abdominal pain scores in this study.

Role of Cannabis and Its Derivatives in Gastrointestinal and Hepatic Disease

Medical and recreational cannabis use has increased dramatically over the last decade, resulting from mainstream cultural acceptance and legalization in several countries worldwide. Cannabis and its derivatives affect many gastrointestinal processes via the endocannabinoid system (ECS). The ECS influences gastrointestinal homeostasis through anti-inflammatory, anti-nociceptive, and anti-secretory effects. Some gastrointestinal disorders might therefore be treated with cannabinoids. Despite numerous studies in cell lines and animals, few human studies have evaluated the therapeutic effects of cannabinoids. Cannabis' schedule 1 drug status has limited its availability in research; cannabis has been legalized only recently, in some states, for medicinal and/or recreational use. Cannabinoids can alleviate chemotherapy-induced nausea and emesis and chronic pain. Studies have demonstrated the important roles of the ECS in metabolism, obesity, and nonalcoholic fatty liver disease and the anti-inflammatory effects of cannabis have been investigated in patients with inflammatory bowel diseases. Despite its potential benefits, undesired or even detrimental effects of cannabis can limit its use. Side effects such as cannabinoid hyperemesis syndrome affect some users. We review the ECS and the effects of cannabis and its derivatives on gastrointestinal and hepatic function in health and disease.

Cannabidiol and Other Non-Psychoactive Cannabinoids for Prevention and Treatment of Gastrointestinal Disorders: Useful Nutraceuticals?

Cannabis sativa is an aromatic annual flowering plant with several botanical varieties, used for different purposes, like the production of fibers, the production of oil from the seeds, and especially for recreational or medical purposes. Phytocannabinoids (terpenophenolic compounds derived from the plant), include the well-known psychoactive cannabinoid Δ9-tetrahydrocannabinol, and many non-psychoactive cannabinoids, like cannabidiol. The endocannabinoid system (ECS) comprises of endocannabinoid ligands, enzymes for synthesis and degradation of such ligands, and receptors. This system is widely distributed in the gastrointestinal tract, where phytocannabinoids exert potent effects, particularly under pathological (i.e., inflammatory) conditions. Herein, we will first look at the hemp plant as a possible source of new functional food ingredients and nutraceuticals that might be eventually useful to treat or even prevent gastrointestinal conditions. Subsequently, we will briefly describe the ECS and the general pharmacology of phytocannabinoids. Finally, we will revise the available data showing that non-psychoactive phytocannabinoids, particularly cannabidiol, may be useful to treat different disorders and diseases of the gastrointestinal tract. With the increasing interest in the development of functional foods for a healthy life, the non-psychoactive phytocannabinoids are hoped to find a place as nutraceuticals and food ingredients also for a healthy gastrointestinal tract function.

Enterocolic increase of cannabinoid receptor type 1 and type 2 and clinical improvement after probiotic administration in dogs with chronic signs of colonic dysmotility without mucosal inflammatory changes

BACKGROUND

Colonic dysmotility in dogs can cause different GI signs. Sometimes, histology of enterocolic biopsies does not reveal inflammatory infiltrates or mucosal lesions that are typically associated with clinical disease activity. It is speculated that, similarly to humans, colonic dysmotility may be anxiety-based, although recent data demonstrate that irritable bowel syndrome (IBS) could result from acute infectious enteritis. Specific Lactobacillus spp. strains administered orally in humans induced the expression of μ-opioid and cannabinoid receptors in mucosal enterocytes, modulating intestinal morphine-like analgesic functions. We investigated the potential association of GI signs caused by colonic dysmotility and mucosal expression of cannabinoid receptors in intestinal epithelial cells and the number of mucosal mast cells.

METHODS

Ten to 15 endoscopic biopsies were collected from colonic mucosa of 20 dogs diagnosed with dysmotility disturbances before and after probiotic (Slab51 bacterial blend; Sivoy^® ) administration (3-month period). Number and distribution of mast cells (MCs), and cannabinoid receptor type 1 (CB1) and type 2 (CB2) were evaluated by immunohistochemistry and PCR. Results were compared to data obtained from five clinically healthy dogs (archive samples).

KEY RESULTS

Decreased numbers of MCs (P < .0001) and increased CB1- and CB2-positive epithelial cells (P < .0001) in diseased dogs were positively associated with post-treatment CCECAI scores (P < .0001).

CONCLUSIONS AND INFERENCES

Our results suggest that probiotic administration can reduce signs of colonic dysmotility, possibly due to microbiota modulation and epithelial cell receptor-mediated signaling in intestinal mucosa.

Relationship Between Recreational Marijuana Use and Bowel Function in a Nationwide Cohort Study

OBJECTIVES

Although the endogenous cannabinoid system modulates bowel function, our understanding of the impact of recreational marijuana (MJ) use on bowel motility is limited. This study examines the effect of MJ on self-reported bowel function among a large cohort of US adults.

METHODS

We identified adults (age: 20-59 years) who completed both the drug use and bowel health questionnaires in the National Health and Nutrition Examination Survey over a 6-year period from 2005 to 2010 (n = 9,645). Constipation and diarrhea were defined according to stool form (Bristol Stool Form Scale) and/or frequency criteria. Adjusted odds ratios (AORs) for likelihood of constipation or diarrhea were estimated in a multinomial logistic model according to MJ use status.

RESULTS

Overall, constipation prevalence was lower among those with recent MJ use compared with those with past/never use (7.5% vs 10.2%, P = 0.03). Recent MJ use was associated with a 30% decreased odds of constipation (crude odds ratio: 0.71 [0.56-0.98], P = 0.005), which persisted after stepwise adjustment for age and other demographic factors including sex, ethnicity, education, body mass index, and socioeconomic status (AOR: 0.64 [0.49-0.83], P = 0.001); comorbidities, substance use (alcohol, tobacco, heroin, and cocaine), constipating medications, general health condition, rigorous physical activity, and emotional disturbances (AOR: 0.68 [0.48-0.93], P = 0.016); and diet (AOR: 0.68 [0.52-0.89], P = 0.006). There was no association between recent MJ use and diarrhea.

DISCUSSION

In a nationally representative sample of community-dwelling US adults, recent MJ use was associated with decreased odds of constipation, counter to the known physiologic effects of cannabinoids on colonic motility.

µ-opioid receptor, β-endorphin, and cannabinoid receptor-2 are increased in the colonic mucosa of irritable bowel syndrome patients

BACKGROUND AND AIMS

The gut immune, cannabinoid, and opioid systems constitute an integrated network contributing to visceral sensation and pain modulation. We aimed to assess the expression of the µ-opioid receptor (MOR), its ligand β-endorphin (β-END), and cannabinoid receptor-2 (CB2 ) in patients with irritable bowel syndrome (IBS) and asymptomatic controls (AC) and their correlation with sex and symptom perception.

METHODS

Mucosal biopsies were obtained from the left colon of 31 IBS patients (45% women) with predominant constipation (IBS-C, 9) or diarrhea (IBS-D, 10) or with mixed bowel habits (IBS-M, 12) and 32 AC (44% women) and processed for qRT-PCR, Western blotting, and immunohistochemistry.

KEY RESULTS

µ-opioid receptor and CB2 mRNA and protein expression and β-END protein levels were increased in patients with IBS compared to AC (all Ps=0.021). A significant sex by IBS interaction was found in relation to CB2 mRNA expression (P = .003) with women showing a markedly higher expression to men (P = .035). In contrast, in AC, men had higher expression than women (P = .033). β-END, MOR, and CB2 immunoreactivities (IR) were localized to CD4+T cells including EMR-1+ eosinophils and CD31+ T cells but not to mast cells.

CONCLUSIONS

The increased expression of MOR, β-END, and CB2 in the mucosa of IBS patients, where they are localized to immune cells, suggests that opioid and cannabinoid systems play an immune-related compensatory role in visceral pain in IBS patients. Further work is necessary to support this hypothesis.

Insights into the role of cannabis in the management of inflammatory bowel disease

Over the last decade, interest in the therapeutic potential of cannabis and its constituents (e.g. cannabidiol) in the management of inflammatory bowel diseases (IBD) has escalated. Cannabis has been increasingly approved for a variety of medical conditions in several jurisdictions around the world. In animal models, cannabinoids have been shown to improve intestinal inflammation in experimental models of IBD through their interaction with the endocannabinoid system. However, the few randomized controlled trials of cannabis or cannabidiol in patients with IBD have not demonstrated efficacy in modulating inflammatory disease activity. Cannabis may be effective in the symptomatic management of IBD. Given the increasing utilization and cultural acceptance of cannabis, physicians need to be aware of its safety and efficacy in order to better counsel patients. The aim of this review is to provide an overview of the role of cannabis in the management of patients with IBD.

Cannabinoids and gastrointestinal motility: Pharmacology, clinical effects, and potential therapeutics in humans

BACKGROUND

Cannabinoid agents and cannabis are frequently used for relief of diverse gastrointestinal symptoms.

PURPOSE

The objective of this article is to increase the awareness of gastroenterologists to the effects of cannabinoids on gastrointestinal motility, as gastroenterologists are likely to encounter patients who are taking cannabinoids, or those with dysmotility that may be associated with cannabinoid mechanisms. The non-selective cannabinoid agonist, dronabinol, retards gastric emptying and inhibits colonic tone and phasic pressure activity. In addition to the well-recognized manifestations of cannabinoid hyperemesis, cannabinoid mechanisms result in human and animal models of gastrointestinal and colonic dysmotility. Decreased enteric FAAH activity is associated with colonic inertia in slow transit constipation and, conversely, the orphan G protein-coupled receptor, GPR55, is overexpressed in streptozotocin-induced gastroparesis, suggesting it is involved in inhibition of antral motility. Experimental therapies in gastrointestinal motility and functional disorders are focused predominantly on pain relief mediated through cannabinoid 2 receptors or inhibition of DAGLα to normalize colonic transit. In summary, cannabinoid mechanisms and pharmacology are relevant to the current and future practice of clinical gastroenterology.

Pharmacological modulation of colorectal distension evoked potentials in conscious rats

BACKGROUND

Cerebral evoked potentials (CEP) induced by colorectal distension (CRD) in conscious rats provides a novel method in studies of visceral sensitivity. The aim of this study was to explore the pharmacological effect on CEP of compounds known to reduce the visceromotor response to CRD.

METHODS

Epidural electrodes were chronically implanted in eight female Sprague-Dawley rats. Evoked potentials were elicited by colorectal rapid balloon distensions (100 ms, 80 mmHg) and the effect of WIN55 (cannabinoid CB receptor agonist), clonidine (adrenergic α₂ receptor agonist), MPEP (mGluR5 receptor antagonist), pregabalin (ligand of α₂δ subunits in voltage-gated calcium channels) and baclofen (GABA-B receptor agonist) on amplitudes and latency of CEP were determined.

RESULTS

WIN55 (0.1 μmol kg^-1), clonidine (0.05 μmol kg^-1), MPEP (10 μmol kg^-1) and pregabalin (200 μmol kg^-1) caused a significant, p < 0.05, reduction of the N2 to P2 peak-to-peak amplitude by 23 ± 8%, 25 ± 8%, 39 ± 5%, and 47 ± 6% respectively. Baclofen (9 μmol kg^-1) induced a prolongation of the N2 peak latency of 18 ± 4% but had no significant effect on the amplitudes.

CONCLUSION

The obtained results suggest that MPEP, WIN55, clonidine, and pregabalin reduce visceral nociceptive input to the brain, whereas the lack of effect of baclofen on CRD evoked CEP amplitudes suggest that the effect on VMR is not due to a direct analgesic effect. Brain responses to colorectal distension provide a useful tool to evaluate pharmacological effects in rats and may serve as a valuable preclinical model for understanding pharmacological mechanisms related to visceral sensitivity.

Toward an effective peripheral visceral analgesic: responding to the national opioid crisis

This minireiew summarizes recent new developments in visceral analgesics. This promising field is important, as a new approach to address abdominal pain with peripheral visceral analgesics is considered a key approach to addressing the current opioid crisis. Some of the novel compounds address peripheral pain mechanisms through modulation of opioid receptors via biased ligands, nociceptin/orphanin FQ opioid peptide (NOP) receptor, or dual action on NOP and μ-opioid receptor, buprenorphine and morphiceptin analogs. Other compounds target nonopioid mechanisms, including cannabinoid (CB2), N-methyl-d-aspartate, calcitonin gene-related peptide, estrogen, and adenosine A_2B receptors and transient receptor potential (TRP) channels (TRPV1, TRPV4, and TRPM8). Although current evidence is based predominantly on animal models of visceral pain, early human studies also support the evidence from the basic and animal research. This augurs well for the development of nonaddictive, visceral analgesics for treatment of chronic abdominal pain, an unmet clinical need.

Advancements in drug development for diarrhea-predominant irritable bowel syndrome

INTRODUCTION

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a common disorder characterized by a complex pathophysiology hampering optimal targeted drug development. Recent advances in our understanding of key underlying mechanisms prompted novel therapeutics including novel pharmacological approaches.

AREAS COVERED

This review summarizes the latest advancements in the pipeline of IBS-D drugs focusing on new pharmacological targets, efficacy and safety of medicinal products considering the recent harmonization of regulatory requirements by the FDA and the EMA.

EXPERT OPINION

The new 5-HT₃ receptor antagonist ramosetron appears a promising therapeutic approach devoid of significant adverse events, although it is presently unavailable in Western countries, most likely because of the precautionary approach taken by regulatory agencies with this drug class. New pharmacological concepts on full agonists/antagonists, mixed-receptor activity and novel drug targets may streamline the present drug pipeline along with the adherence on new regulatory guidelines on outcome measures. Eluxadoline can be taken as an example of this paradigm shift. It has now been granted marketing authorization for IBS-D on both sides of the Atlantic, but it is still considered as a second-line agent by the NICE. There is still much work to be done to fully cover clinical needs of patients with IBS-D.

Endocannabinoid-related compounds in gastrointestinal diseases

The endocannabinoid system (ECS) is an endogenous signalling pathway involved in the control of several gastrointestinal (GI) functions at both peripheral and central levels. In recent years, it has become apparent that the ECS is pivotal in the regulation of GI motility, secretion and sensitivity, but endocannabinoids (ECs) are also involved in the regulation of intestinal inflammation and mucosal barrier permeability, suggesting their role in the pathophysiology of both functional and organic GI disorders. Genetic studies in patients with irritable bowel syndrome (IBS) or inflammatory bowel disease have indeed shown significant associations with polymorphisms or mutation in genes encoding for cannabinoid receptor or enzyme responsible for their catabolism, respectively. Furthermore, ongoing clinical trials are testing EC agonists/antagonists in the achievement of symptomatic relief from a number of GI symptoms. Despite this evidence, there is a lack of supportive RCTs and relevant data in human beings, and hence, the possible therapeutic application of these compounds is raising ethical, political and economic concerns. More recently, the identification of several EC-like compounds able to modulate ECS function without the typical central side effects of cannabino-mimetics has paved the way for emerging peripherally acting drugs. This review summarizes the possible mechanisms linking the ECS to GI disorders and describes the most recent advances in the manipulation of the ECS in the treatment of GI diseases.

Review: The Role of Cannabinoids on Esophageal Function-What We Know Thus Far

The endocannabinoid system (ECS) primarily consists of cannabinoid receptors (CBRs), endogenous ligands, and enzymes for endocannabinoid biosynthesis and inactivation. Although the presence of CBRs, both CB1 and CB2, as well as a third receptor (G-protein receptor 55 [GPR55]), has been established in the gastrointestinal (GI) tract, few studies have focused on the role of cannabinoids on esophageal function. To date, studies have shown their effect on GI motility, inflammation and immunity, intestinal and gastric acid secretion, nociception and emesis pathways, and appetite control. Given the varying and sometimes limited efficacy of current medical therapies for diseases of the esophagus, further understanding and investigation into the interplay of the ECS on esophageal health and disease may present new therapeutic modalities that may help advance current treatment options. In this brief review, the current understanding of the ECS role in various esophageal functions and disorders is presented.

Dronabinol increases pain threshold in patients with functional chest pain: a pilot double-blind placebo-controlled trial

Noncardiac chest pain is associated with poor quality of life and high care expenditure. The majority of noncardiac chest pain is either gastresophageal reflux disease related or due to esophageal motility disorders, and the rest are considered functional chest pain (FCP) due to central and peripheral hypersensitivity. Current treatment of FCP improves 40-50% of patients. Cannabinoid receptors 1 (CB1) and 2 (CB2) modulate release of neurotransmitters; CB1 is located in the esophageal epithelium and reduces excitatory enteric transmission and potentially could reduce esophageal hypersensitivity. We performed a prospective study to evaluate its effects on pain threshold, frequency, and intensity in FCP. Subjects with FCP received dronabinol (5 mg, twice daily; n = 7; average age, 44 years; mean body mass index, 26.7) or placebo (n = 6; average age, 42 years; mean body mass index, 25.9) for 28 days (4 weeks). Chest pain, general health, and anxiety/depression questionnaires were assessed at baseline and at 4 weeks. Subjects underwent an esophageal balloon distention test prior to treatment and on last day of the study. Dronabinol increased pain thresholds significantly (3.0 vs. 1.0; P = 0.03) and reduced pain intensity and odynophagia compared to placebo (0.18 vs. 0.01 and 0.12 vs. 0.01, respectively, P = 0.04). Depression and anxiety scores did not differ between the groups at baseline or after treatment. No significant adverse effects were observed. In this novel study, dronabinol increased pain threshold and reduced frequency and intensity of pain in FCP. Further, large scale studies are needed to substantiate these findings.

Role of Cannabinoids in Gastrointestinal Mucosal Defense and Inflammation

Modulating the activity of the endocannabinoid system influences various gastrointestinal physiological and pathophysiological processes, and cannabinoid receptors as well as regulatory enzymes responsible for the synthesis or degradation of endocannabinoids representing potential targets to reduce the development of gastrointestinal mucosal lesions, hemorrhage and inflammation. Direct activation of CB₁ receptors by plant-derived, endogenous or synthetic cannabinoids effectively reduces both gastric acid secretion and gastric motor activity, and decreases the formation of gastric mucosal lesions induced by stress, pylorus ligation, nonsteroidal anti-inflammatory drugs (NSAIDs) or alcohol, partly by peripheral, partly by central mechanisms. Similarly, indirect activation of cannabinoid receptors through elevation of endocannabinoid levels by globally acting or peripherally restricted inhibitors of their metabolizing enzymes (FAAH, MAGL) or by inhibitors of their cellular uptake reduces the gastric mucosal lesions induced by NSAIDs in a CB₁ receptor-dependent fashion. Dual inhibition of FAAH and cyclooxygenase enzymes induces protection against both NSAID-induced gastrointestinal damage and intestinal inflammation. Moreover, in intestinal inflammation direct or indirect activation of CB₁ and CB₂ receptors exerts also multiple beneficial effects. Namely, activation of both CB receptors was shown to ameliorate intestinal inflammation in various murine colitis models, to decrease visceral hypersensitivity and abdominal pain, as well as to reduce colitis-associated hypermotility and diarrhea. In addition, CB₁ receptors suppress secretory processes and also modulate intestinal epithelial barrier functions. Thus, experimental data suggest that the endocannabinoid system represents a promising target in the treatment of inflammatory bowel diseases, and this assumption is also confirmed by preliminary clinical studies.

The Role of Visceral Hypersensitivity in Irritable Bowel Syndrome: Pharmacological Targets and Novel Treatments

Irritable bowel syndrome (IBS) is the most common disorder referred to gastroenterologists and is characterized by altered bowel habits, abdominal pain, and bloating. Visceral hypersensitivity (VH) is a multifactorial process that may occur within the peripheral or central nervous systems and plays a principal role in the etiology of IBS symptoms. The pharmacological studies on selective drugs based on targeting specific ligands can provide novel therapies for modulation of persistent visceral hyperalgesia. The current paper reviews the cellular and molecular mechanisms underlying therapeutic targeting for providing future drugs to protect or treat visceroperception and pain sensitization in IBS patients. There are a wide range of mediators and receptors participating in visceral pain perception amongst which substances targeting afferent receptors are attractive sources of novel drugs. Novel therapeutic targets for the management of VH include compounds which alter gut-brain pathways and local neuroimmune pathways. Molecular mediators and receptors participating in pain perception and visceroperception include histamine-1 receptors, serotonin (5-hydrodytryptamine) receptors, transient receptor potential vanilloid type I, tachykinins ligands, opioid receptors, voltage-gated channels, tyrosine receptor kinase receptors, protease-activated receptors, adrenergic system ligands, cannabinoid receptors, sex hormones, and glutamate receptors which are discussed in the current review. Moreover, several plant-derived natural compounds with potential to alleviate VH in IBS have been highlighted. VH has an important role in the pathology and severity of complications in IBS. Therefore, managing VH can remarkably modulate the symptoms of IBS. More preclinical and clinical investigations are needed to provide efficacious and targeted medicines for the management of VH.

Cannabinoids and GI Disorders: Endogenous and Exogenous

OPINION STATEMENT

Despite the political and social controversy affiliated with it, the medical community must come to the realization that cannabinoids exist as a ubiquitous signaling system in many organ systems. Our understanding of cannabinoids and how they relate not only to homeostasis but also in disease states must be furthered through research, both clinically and in the laboratory. The identification of the cannabinoid receptors in the early 1990s have provided us with the perfect target of translational research. Already, much has been done with cannabinoids and the nervous system. Here, we explore the implications it has for the gastrointestinal tract. Most therapeutics currently on the market presently target only one aspect of the cannabinoid system. Our main purpose here is to highlight areas of research and potential avenues of discovery that the cannabinoid system has yet to reveal.

Synthesis, binding assays, cytotoxic activity and docking studies of benzimidazole and benzothiophene derivatives with selective affinity for the CB2 cannabinoid receptor

Herein we report the design, synthesis, bioinformatic and biological studies of benzimidazole and benzothiophene derivatives as new cannabinoid receptor ligands. To test the hypothesis that the lack of a hydrogen bond interaction between benzimidazole and benzothiophene derivatives with Lys192 reduces their affinity for CB1 receptors (as we previously reported) and leads to CB2 selectivity, most of the tested compounds do not exhibit hydrogen bond acceptors. All compounds displayed mostly CB2 selectivity, although this was more pronounced in the benzimidazoles derivatives. Furthermore, docking assays revealed a ∏-cation interaction with Lys109 which could play a key role for the CB2 selectivity index. The series displayed low toxicity on five different cell lines. Derivative 8f presented the best binding profile (Ki = 0.08 μM), high selectivity index (KiCB1/KiCB2) and a low citoxicity. Interestingly, in cell viability experiments, using HL-60 cells (expressing exclusively CB2 receptors), all synthesised compounds were shown to be cytotoxic, suggesting that a CB2 agonist response may be involved.

The effect of FAAH, MAGL, and Dual FAAH/MAGL inhibition on inflammatory and colorectal distension-induced visceral pain models in Rodents

BACKGROUND

Recent studies showed that the pharmacological inhibition of endocannabinoid degrading enzymes such as fatty acid amide hydrolase (FAAH) and monoacyl glycerol lipase (MAGL) elicit promising analgesic effects in a variety of nociceptive models without serious side effects. However, the full spectrum of activities is not observed upon inhibition of either FAAH or MAGL enzymes alone and thus dual FAAH and MAGL inhibitors have been described. Visceral pain is strongly associated with inflammation and distension of the gut. Thus, we explored the comparable effects of FAAH, MAGL, and dual FAAH/MAGL inhibitors on inflammatory and mechanically evoked visceral pain models.

METHODS

Visceral inflammatory and distension-induced pain were assessed with the 0.6% acetic acid writhing test in mice and colorectal distension (CRD) test in rats, respectively. The selective FAAH inhibitor PF 3845, MAGL inhibitor JZL 184, dual inhibitor JZL 195, and the cannabis analog CP 55,940 were given systemically 30 min prior to nociceptive testing.

KEY RESULTS

PF 3845 (5, 10, and 20 mg/kg), JZL 184 (5, 10, and 20 mg/kg), and JZL 195 (5, 10, and 20 mg/kg) elicit dose-dependent antinociceptive in the acetic acid writhing test. In the CRD model, while JZL 195 (5, 10, or 20 mg/kg) and PF3845 (10, 20, and 40 mg/kg) produced dose-dependent antinociceptive effects comparable to those of CP 55,940 (0.1, 0.3, or 1 mg/kg), JZL 184 (10, 20, and 40 mg/kg) alone did not alter the visceromotor response (VMR).

CONCLUSIONS & INFERENCES

The selective FAAH inhibitor and dual FAAH/MAGL inhibitors were effective in both inflammatory and mechanically evoked visceral pain, while the MAGL inhibitor elicited an analgesic effect in inflammatory, but not in distension-induced, visceral pain.

The role of cannabinoids in regulation of nausea and vomiting, and visceral pain

Marijuana derived from the plant Cannabis sativa has been used for the treatment of many gastrointestinal (GI) disorders, including anorexia, emesis, abdominal pain, diarrhea, and others. However, its psychotropic side effects have often limited its use. Several cannabinoid receptors, which include the cannabinoid receptor 1 (CB1), CB2, and possibly GPR55, have been identified throughout the GI tract. These receptors may play a role in the regulation of food intake, nausea and emesis, gastric secretion and gastroprotection, GI motility, ion transport, visceral sensation, intestinal inflammation, and cell proliferation in the gut. However, the regulation of nausea and vomiting by cannabinoids and the endocannabinoid system has shed new knowledge in this field. Thus far, despite evidence of visceral sensitivity inhibition in animal models, data in irritable bowel syndrome (IBS) patients is scarce and not supportive. Furthermore, many compounds that either act directly at the receptor or increase (or reduce) ligand availability have the potential to affect other brain functions and cause side effects. Novel drug targets such as FAAH and monoacylglycerol lipase (MAGL) inhibitors appear to be promising in animal models, but more studies are necessary to prove their efficiency. The promise of emerging drugs that are more selective and peripherally acting suggest that, in the near future, cannabinoids will play a major role in managing an array of GI diseases.

Identification of a highly potent and selective CB2 agonist, RQ-00202730, for the treatment of irritable bowel syndrome

Herein we report the identification of a highly potent and selective CB2 agonist, RQ-00202730 (40), obtained by lead optimization of the benzimidazole scaffold. Compound 40 showed strong agonistic activity with an EC50 of 19nM and excellent selectivity (>1300-fold) over the CB1 receptor. Compound 40 displayed a dose dependent analgesic effect on TNBS-induced visceral hypersensitivity in rats by oral administration (ED50 0.66mg/kg at 2.5h after oral administration). In addition, 40 did not show a significant effect on body temperature in rats after oral administration at 300mg/kg. These findings suggest that highly selective CB2 agonists will be effective agents for IBS therapy.

Cannabinoid receptor 2 agonist attenuates pain related behavior in rats with chronic alcohol/high fat diet induced pancreatitis

Background

Chronic Pancreatitis (CP) is a complex and multifactorial syndrome. Many contributing factors result in development of dysfunctional pain in a significant number of patients. Drugs developed to treat a variety of pain states fall short of providing effective analgesia for patients with chronic pancreatitis, often providing minimal to partial pain relief over time with significant side effects. Recently, availability of selective pharmacological tools has enabled great advances in our knowledge of the role of the cannabinoid receptors in pathophysiology. In particular, cannabinoid receptor 2 (CB2) has emerged as an attractive target for management of chronic pain, as demonstrated in several studies with inflammatory and neuropathic preclinical pain models. In this study, the analgesic efficacy of a novel, highly selective CB2 receptor agonist, LY3038404 HCl, is investigated in a chronic pancreatitis pain model, induced with an alcohol/high fat (AHF) diet.

Results

Rats fed the AHF diet developed visceral pain-like behaviors detectable by week 3 and reached a maximum at week 5 that persists as long as the diet is maintained. Rats with AHF induced chronic pancreatitis were treated with LY3038404 HCl (10 mg/kg, orally, twice a day for 9 days). The treated animals demonstrated significantly alleviated pain related behaviors after 3 days of dosing, including increased paw withdrawal thresholds (PWT), prolonged abdominal withdrawal latencies (ABWL), and decreased nocifensive responses to noxious 44°C hotplate stimuli. Terminal histological analysis of pancreatic tissue sections from the AHF chronic pancreatitis animals demonstrated extensive injury, including a global pancreatic gland degeneration (cellular atrophy), vacuolization (fat deposition), and fibrosis. After the LY3038404 HCl treatment, pancreatic tissue was significantly protected from severe damage and fibrosis. LY3038404 HCl affected neither open field exploratory behaviors nor dark/light box preferences as measures of higher brain and motor functions.

Conclusion

LY3038404 HCl, a potent CB2 receptor agonist, possesses tissue protective and analgesic properties without effects on higher brain function. Thus, activation of CB2 receptors is suggested as a potential therapeutic target for visceral inflammation and pain management.

Novel orally available salvinorin A analog PR-38 protects against experimental colitis and reduces abdominal pain in mice by interaction with opioid and cannabinoid receptors

BACKGROUND

Salvinorin A (SA) is a potent anti-inflammatory diterpene isolated from the Mexican plant S. divinorum. Recently we showed that the novel SA analog, PR-38 has an inhibitory effect on mouse gastrointestinal (GI) motility mediated by opioid and cannabinoid (CB) receptors. The aim of the study was to characterize possible anti-inflammatory and antinociceptive action of PR-38 in the mouse GI tract.

METHODS

Macro- and microscopic colonic damage scores and myeloperoxidase activity were determined after intraperitoneal (i.p.), intracolonic (i.c.), and per os (p.o.) administration of PR-38 in the trinitrobenzene sulfonic acid (TNBS) and dextran sodium sulfate (DSS) models of colitis in mice. Additionally, MOP, KOP and CB1 protein expression was determined using Western blot analysis of mouse colon samples. The antinociceptive effect of PR-38 was examined based on the number of behavioral responses to i.c. instillation of mustard oil (MO).

RESULTS

The i.p. (10 mg/kg, twice daily), i.c. (10 mg/kg, twice daily) and p.o. (20 mg/kg, once daily) administration of PR-38 significantly attenuated TNBS- and DSS-induced colitis in mice. The effect of PR-38 was partially blocked by the KOP antagonist nor-binaltorphimine and CB1 antagonist AM 251. Western blot analysis showed a significant increase of MOP, KOP and CB1 receptor expression during colonic inflammation, which was reversed to the control levels by the administration of PR-38. PR-38 significantly decreased the number of pain responses after i.c. instillation of MO in the TNBS-treated mice.

CONCLUSIONS

Our results suggest that PR-38 has the potential to become a valuable anti-inflammatory and analgesic therapeutic for the treatment of GI inflammation.

Toward modulation of the endocannabinoid system for treatment of gastrointestinal disease: FAAHster but not "higher"

Cannabis has been used to treat various afflictions throughout the centuries, including nausea, vomiting, and pain. It has also been used recreationally for its psychotropic properties, which can include a pleasurable 'high' feeling and a decrease in anxiety and tension; however, other may experience dysphoria. Changes in cognition and psychomotor performance are also well-known with cannabis use. In recent years, our understanding of the endocannabinoid system (ECS) has progressed dramatically; the objective of identifying agents which may allow modulation of the ECS without significant psychotropic side effects may be possible. Inhibition of fatty acid amide hydrolase (FAAH), an important enzyme for the degradation of anandamide and other endogenous cannabinoids, is a promising target to achieve this goal. In this issue of Neurogastroenterology and Motility, Fichna and colleagues report on a novel selective FAAH inhibitor, PF-3845, with potent antinociceptive and antidiarrheal effects in a mouse model. In this context, we briefly review the components of the ECS, discuss pharmacologic targets for indirect cannabinoid receptor stimulation, and describe recent research with cannabinoids for gut disorders.

[From cannabis to selective CB2R agonists: molecules with numerous therapeutical virtues]

Originally used in Asia for the treatment of pain, spasms, nausea and insomnia, marijuana is the most consumed psychotropic drug worldwide. The interest of medical cannabis has been reconsidered recently, leading to many scientific researches and commercialization of these drugs. Natural and synthetic cannabinoids display beneficial antiemetic, anti-inflammatory and analgesic effects in numerous diseases, however accompanied with undesirable effects due to the CB1 receptor. Present researches focus on the design of therapeutical molecules targeting the CB2 receptors, and thus avoiding central side effects and therefore psychotropic effects caused by the CB1 receptor.

Targeting the endocannabinoid system for gastrointestinal diseases: future therapeutic strategies

Cannabinoids extracted from the marijuana plant (Cannabis sativa) and synthetic cannabinoids have numerous effects on gastrointestinal (GI) functions. Recent experimental data support an important role for cannabinoids in GI diseases. Genetic studies in humans have proven that defects in endocannabinoid metabolism underlie functional GI disorders. Mammalian cells have machinery, the so-called endocannabinoid system (ECS), to produce and metabolize their own cannabinoids in order to control homeostasis of the gut in a rapidly adapting manner. Pharmacological manipulation of the ECS by cannabinoids, or by drugs that raise the levels of endogenous cannabinoids, have shown beneficial effects on GI pathophysiology. This review gives an introduction into the functions of the ECS in the GI tract, highlights the role of the ECS in GI diseases and addresses its potential pharmacological exploitation.

The endocannabinoid system in inflammatory bowel diseases: from pathophysiology to therapeutic opportunity

Crohn's disease and ulcerative colitis are two major forms of inflammatory bowel diseases (IBD), which are chronic inflammatory disorders of the gastrointestinal tract. These pathologies are currently under investigation to both unravel their etiology and find novel treatments. Anandamide and 2-arachidonoylglycerol are endogenous bioactive lipids that bind to and activate the cannabinoid receptors, and together with the enzymes responsible for their biosynthesis and degradation [fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL)] constitute the endocannabinoid system (ECS). The ECS is implicated in gut homeostasis, modulating gastrointestinal motility, visceral sensation, and inflammation, as well as being recently implicated in IBD pathogenesis. Numerous subsequent studies investigating the effects of cannabinoid agonists and endocannabinoid degradation inhibitors in rodent models of IBD have identified a potential therapeutic role for the ECS.

Cannabinoid receptors in submandibular acinar cells: functional coupling between saliva fluid and electrolytes secretion and Ca2+ signalling

Cannabinoid receptors (CBRs) belong to the G protein-coupled receptor superfamily, and activation of CBRs in salivary cells inhibits agonist-stimulated salivation and modifies saliva content. However, the role of different CBR subtypes in acinar cell physiology and in intracellular signalling remains unclear. Here, we uncover functional CB(1)Rs and CB(2)Rs in acinar cells of rat submandibular gland and their essential role in saliva secretion. Pharmacological activation of CB(1)Rs and CB(2)Rs in the submandibular gland suppressed saliva outflow and modified saliva content produced by the submandibular gland in vivo. Using Na(+)-selective microelectrodes to record secretory Na(+) responses in the lumen of acini, we observed a reduction in Na(+) transport following the activation of CBRs, which was counteracted by the selective CB(1)R antagonist AM251. In addition, activation of CB(1)Rs or CB Rs caused inhibition of Na(+)-K(+) 2 -ATPase activity in microsomes derived from the gland tissue as well as in isolated acinar cells. Using a Ca(2+) imaging technique, we showed that activation of CB(1)Rs and CB(2)Rs alters [Ca(2+)](cyt) signalling in acinar cells by distinct pathways, involving Ca(2+) release from the endoplasmic reticulum (ER) and store-operated Ca(2+) entry (SOCE), respectively. Our data demonstrate the expression of CB(1)Rs and CB(2)Rs in acinar cells, and their involvement in the regulation of salivary gland functioning.

The cannabinoid receptor agonist delta-9-tetrahydrocannabinol does not affect visceral sensitivity to rectal distension in healthy volunteers and IBS patients

BACKGROUND

Visceral hypersensitivity to distension is thought to play an important role in the pathophysiology of the irritable bowel syndrome (IBS). Cannabinoids are known to decrease somatic pain perception, but their effect on visceral sensitivity in IBS remains unclear. Therefore, we evaluated the effect of the mixed CB(1) /CB(2) receptor agonist delta-9-tetrahydrocannabinol (Δ(9) -THC, dronabinol) on rectal sensitivity.

METHODS

Ten IBS patients and 12 healthy volunteers (HV) underwent a barostat study to assess rectal sensitivity using an intermittent pressure-controlled distension protocol before and after sigmoid stimulation. Repetitive sigmoid stimulation is a validated method to increase visceral perception in IBS patients, consisting of a 10-min period of 30 s stimuli (60 mmHg), separated by 30 s of rest (5 mmHg). The effect of placebo and Δ(9) -THC (5 and 10 mg in healthy volunteers and 10 mg in IBS patients) on rectal sensitivity was evaluated on respectively three and two separate days in a double blind, randomized, crossover fashion.

KEY RESULTS

All participants (HV and IBS) reported central side effects during the highest dose of Δ(9) -THC, most frequently increased awareness of the surrounding, light-headedness and sleepiness, whereas no side effects where reported during placebo. Although blood pressure was not affected, heart rate increased in both HV and IBS, but was most pronounced in IBS patients. The cannabinoid agonist Δ(9) -THC did not alter baseline rectal perception to distension compared to placebo in HV or IBS patients. Similarly, after sigmoid stimulation there were no significant differences between placebo and Δ(9) -THC in sensory thresholds of discomfort.

CONCLUSIONS & INFERENCES

These findings imply that Δ(9) -THC does not modify visceral perception to rectal distension and argue against (centrally acting) CB agonists as tool to decrease visceral hypersensitivity in IBS patients.

Small intestinal cannabinoid receptor changes following a single colonic insult with oil of mustard in mice

Cannabinoids are known to be clinically beneficial for control of appetite disorders and nausea/vomiting, with emerging data that they can impact other GI disorders, such as inflammation. Post-inflammatory irritable bowel syndrome (PI-IBS) is a condition of perturbed intestinal function that occurs subsequent to earlier periods of intestinal inflammation. Cannabinoid 1 receptor (CB1R) and CB2R alterations in GI inflammation have been demonstrated in both animal models and clinically, but their continuing role in the post-inflammatory period has only been implicated to date. Therefore, to provide direct evidence for CBR involvement in altered GI functions in the absence of overt inflammation, we used a model of enhanced upper GI transit that persists for up to 4 weeks after a single insult by intracolonic 0.5% oil of mustard (OM) in mice. In mice administered OM, CB1R immunostaining in the myenteric plexus was reduced at day 7, when colonic inflammation is subsiding, and then increased at 28 days, compared to tissue from age-matched vehicle-treated mice. In the lamina propria CB2R immunostaining density was also increased at day 28. In mice tested 28 day after OM, either a CB1R-selective agonist, ACEA (1 and 3 mg/kg, s.c.) or a CB2R-selective agonist, JWH-133 (3 and 10 mg/kg, s.c.) reduced the enhanced small intestinal transit in a dose-related manner. Doses of ACEA and JWH-133 (1 mg/kg), alone or combined, reduced small intestinal transit of OM-treated mice to a greater extent than control mice. Thus, in this post-colonic inflammation model, both CBR subtypes are up-regulated and there is increased efficacy of both CB1R and CB2R agonists. We conclude that CBR remodeling occurs not only during GI inflammation but continues during the recovery phase. Thus, either CB1R- or CB2-selective agonists could be efficacious for modulating GI motility in individuals experiencing diarrhea-predominant PI-IBS.

Cannabinoid 1 receptors modulate intestinal sensory and motor function in rat

BACKGROUND

Cannabinoid receptors are involved in visceral pain perception and control of intestinal motility in vivo. The underlying mechanisms are not well characterized. We aimed to determine whether the cannabinoid-1 (CB(1)) receptor modulates intestinal afferent nerve discharge and the peristaltic reflex.

METHODS

Rats were anesthetized and intestinal segments were removed. Afferent nerve discharge from a mesenteric nerve was investigated in vitro in the presence of the CB(1) antagonist SR 141716A or the CB(1) agonist WIN 55212-2. The myenteric peristaltic reflex was induced by electrical field stimulation and influence of SR 141716A or WIN 55212-2 was recorded.

KEY RESULTS

Afferent nerve discharge to the algesic mediator bradykinin was reduced to 11 +/- 5.1 imp s(-1) following pretreatment with SR 141716A and unchanged after WIN 55212-2 compared to 63 +/- 15.4 imp s(-1) in controls. At maximum distension pressure (80 cmH(2)O) during ramp distension, 92 +/- 12.4 imp s(-1) were reached following SR 141716A compared to 260 +/- 13.2 in vehicle controls and 227 +/- 15.4 in WIN 55212-2 pretreated animals. In contrast, afferent discharge to 5-HT (500 micromol L(-1)) was increased to 75 +/- 24.6 imp s(-1) following WIN 55212-2 compared to 18 +/- 5.9 imp s(-1) in controls, whereas SR 141716A had no effect. Ascending neuronal contractions were dose-dependently attenuated in the presence of SR 141716A and latency of these contractions was reduced. WIN 55212-2 had opposite effects that were abolished by SR 141716A.

CONCLUSIONS & INFERENCES

Activation of the CB(1) receptor differentially alters afferent intestinal nerve sensitivity to bradykinin, 5-HT, and noxious mechanical distension, while it strengthens ascending neuronal contractions. Further studies are needed to determine the physiological relevance of these observations.

Cannabinoids and the gut: new developments and emerging concepts

Cannabis has been used to treat gastrointestinal (GI) conditions that range from enteric infections and inflammatory conditions to disorders of motility, emesis and abdominal pain. The mechanistic basis of these treatments emerged after the discovery of Delta(9)-tetrahydrocannabinol as the major constituent of Cannabis. Further progress was made when the receptors for Delta(9)-tetrahydrocannabinol were identified as part of an endocannabinoid system, that consists of specific cannabinoid receptors, endogenous ligands and their biosynthetic and degradative enzymes. Anatomical, physiological and pharmacological studies have shown that the endocannabinoid system is widely distributed throughout the gut, with regional variation and organ-specific actions. It is involved in the regulation of food intake, nausea and emesis, gastric secretion and gastroprotection, GI motility, ion transport, visceral sensation, intestinal inflammation and cell proliferation in the gut. Cellular targets have been defined that include the enteric nervous system, epithelial and immune cells. Molecular targets of the endocannabinoid system include, in addition to the cannabinoid receptors, transient receptor potential vanilloid 1 receptors, peroxisome proliferator-activated receptor alpha receptors and the orphan G-protein coupled receptors, GPR55 and GPR119. Pharmacological agents that act on these targets have been shown in preclinical models to have therapeutic potential. Here, we discuss cannabinoid receptors and their localization in the gut, the proteins involved in endocannabinoid synthesis and degradation and the presence of endocannabinoids in the gut in health and disease. We focus on the pharmacological actions of cannabinoids in relation to GI disorders, highlighting recent data on genetic mutations in the endocannabinoid system in GI disease.

CB1 receptors mediate the analgesic effects of cannabinoids on colorectal distension-induced visceral pain in rodents

Activation of cannabinoid receptors (CB(1), CB(2) and GPR(55)) produces analgesic effects in several experimental pain models, including visceral pain arising from the gastrointestinal tract. We assessed the role of CB(1), CB(2), and GPR(55) receptors and the endogenous cannabinoid system on basal pain responses and acute mechanical hyperalgesia during colorectal distension (CRD) in rodents. The effects of cannabinoid receptor agonists and antagonists on pain-related responses to CRD were assessed in rats and in wild-type and CB(1) receptor knock-out mice. The dual CB(1/2) agonist, WIN55,212-2, and the peripherally acting CB(1)-selective agonist, SAB-378, inhibited pain-related responses to repetitive noxious CRD (80 mmHg) in a dose-related manner in rats. The analgesic effects of WIN55,212-2 and SAB-378 were blocked by the selective CB(1) antagonist SR141716, but were not affected by the selective CB(2) antagonist SR144528. SR141716, per se, increased the responses to repetitive noxious CRD, indicative of hyperalgesia, and induced pain-related responses during non-noxious CRD (20 mmHg), indicative of allodynia. The cannabinoid receptor agonists anandamide, virodhamine and O-1602 had no effect. At analgesic doses, WIN55,212-2 did not affect colonic compliance. In accordance to the rat data, WIN55,212-2 produced analgesia, whereas SR141716 induced hyperalgesia, during noxious CRD (55 mmHg) in wild-type but not in CB(1)-knock-out mice. These data indicate that peripheral CB(1) receptors mediate the analgesic effects of cannabinoids on visceral pain from the gastrointestinal tract. The allodynic and hyperalgesic responses induced by SR141716 suggest the existence of an endogenous cannabinoid tone and the activation of CB(1) receptors during noxious CRD.