Cannabinoids and the digestive tract

Assessment of spent hemp biomass as a potential ingredient in ruminant diet: nutritional quality and effect on performance, meat and carcass quality, and hematological parameters in finishing lambs

Spent hemp biomass (SHB), a byproduct of cannabinoid extraction from the production of industrial hemp has not been approved by FDA-CVM since its effects on animal health, performance, and product quality are unknown. Our objective was to investigate the effects of feeding two levels of SHB and a 4-wk withdrawal period on performance, carcass characteristic, meat quality, and hematological parameters in finishing lambs. A total of 35 weaned, Polypay male lambs kept in single pens were randomly assigned to five feeding treatments (n = 7) and fed diets containing either no SHB (CON) or SHB at 10% (LH1) or 20% (HH1) for 4 wk with 4 wk of clearing period from SHB, or SHB at 10% (LH2) or 20% (HH2) for 8 wk. Chemical analysis revealed SHB to have a nutritive quality similar to alfalfa with no mycotoxin, terpenes, or organic residuals as a result of the extraction process. Feed intake of lambs was negatively affected by 20% SHB in period 1 but not in period 2 where feed intake was the greatest in HH1 and LH2. In contrast, none of the performance data, including liveweight gains, were different across the groups and periods. In period 1, blood glucose, cholesterol, calcium, paraoxonase, and tocopherol were decreased by the level of SHB fed, while bilirubin and alkaline phosphatase (ALP) were increased. In period 2, the concentration in blood of urea, magnesium, bilirubin, ALP, and ferric reducing ability of the plasma (FRAP) were higher in LH2 and HH2 as compared with CON, while β-hydroxybutyrate was lower in HH2. Blood parameters related to liver health, kidney function, immune status, and inflammation were unaffected by feeding SHB. Most carcass and meat quality parameters did not differ across feeding groups either. Except carcass purge loss and meat cook loss were larger in lambs that were fed 20% SHB. Although lower feed intake of lambs that were fed 20% SHB initially in period 1 suggested SHB was not palatable to the lambs, increased feed intake at a lower level of inclusion at 10% in period 2 may point to a positive long-term effect of feeding SHB.

Localisation of Cannabinoid and Cannabinoid-Related Receptors in the Horse Ileum

Colic is a common digestive disorder in horses and one of the most urgent problems in equine medicine. A growing body of literature has indicated that the activation of cannabinoid receptors could exert beneficial effects on gastrointestinal inflammation and visceral hypersensitivity. The localisation of cannabinoid and cannabinoid-related receptors in the intestine of the horse has not yet been investigated. The purpose of this study was to immunohistochemically localise the cellular distribution of canonical and putative cannabinoid receptors in the ileum of healthy horses. Distal ileum specimens were collected from six horses at the slaughterhouse. The tissues were fixed and processed to obtain cryosections which were used to investigate the immunoreactivity of canonical cannabinoid receptors 1 (CB1R) and 2 (CB2R), and three putative cannabinoid-related receptors: nuclear peroxisome proliferator-activated receptor-alpha (PPARα), transient receptor potential ankyrin 1 and serotonin 5-HT1a receptor (5-HT1aR). Cannabinoid and cannabinoid-related receptors showed a wide distribution in the ileum of the horse. The epithelial cells showed immunoreactivity for CB1R, CB2R and 5-HT1aR. Lamina propria inflammatory cells showed immunoreactivity for CB2R and 5-HT1aR. The enteric neurons showed immunoreactivity for CB1R, transient receptor potential ankyrin 1 and PPARα. The enteric glial cells showed immunoreactivity for CB1R and PPARα. The smooth muscle cells of the tunica muscularis and the blood vessels showed immunoreactivity for PPARα. The present study represents a histological basis which could support additional studies regarding the distribution of cannabinoid receptors during gastrointestinal inflammatory diseases as well as studies assessing the effects of non-psychotic cannabis-derived molecules in horses for the management of intestinal diseases.

Cannabis Use Disorders Lead to Hospitalizations for Peptic Ulcer Disease: Insights From a Nationwide Inpatient Sample Analysis

Objectives

In this study, we aimed to explore the independent association between cannabis use disorders (CUD) and peptic ulcer disease (PUD)-related hospitalization, and then to delineate the demographic differences among PUD inpatients with versus without CUD.

Methodology

We conducted a cross-sectional study using the Nationwide Inpatient Sample of 50,444,133 patients. We then subgrouped them into PUD and non-PUD cohorts. We compared non-PUD and PUD cohorts using bivariate analysis to delineate the differences in demographics and comorbid risk factors (chronic lung disease, chronic kidney disease, liver disease, diabetes, chronic nonsteroidal anti-inflammatory drug use, tobacco abuse, and alcohol abuse). We used logistic regression analysis to measure the odds ratio (OR) of the association between CUD and PUD-related hospitalization.

Results

The prevalence of PUD was 0.14% (N = 70,898) among the total inpatient population. It was more prevalent in whites (65%) and males were at higher odds (OR: 1.11; P < 0.001) of being hospitalized for PUD. After controlling for potential comorbid risk factors and demographic confounders, the odds of association between CUD and PUD-related hospitalization were statistically significant (OR: 1.18; P < 0.001).

Conclusions

CUD was associated with a modest but significant increase of 18% in the likelihood of hospitalization for PUD. With the legalization of cannabis use and its increasing and problematic consumption, it is imperative to understand the impact of cannabis use on the physical health of patients and the related gastrointestinal problems.

The Genomics of Cannabis and Its Close Relatives

Cannabis sativa L. is an important yet controversial plant with a long history of recreational, medicinal, industrial, and agricultural use, and together with its sister genus Humulus, it represents a group of plants with a myriad of academic, agricultural, pharmaceutical, industrial, and social interests. We have performed a meta-analysis of pooled published genomics data, andwe present a comprehensive literature review on the evolutionary history of Cannabis and Humulus, including medicinal and industrial applications. We demonstrate that current Cannabis genome assemblies are incomplete, with ∼10% missing, 10-25% unmapped, and 45S and 5S ribosomal DNA clusters as well as centromeres/satellite sequences not represented. These assemblies are also ordered at a low resolution, and their consensus quality clouds the accurate annotation of complete, partial, and pseudogenized gene copies. Considering the importance of genomics in the development of any crop, this analysis underlines the need for a coordinated effort to quantify the genetic and biochemical diversity of this species.

Activation of cannabinoid 2 receptor relieves colonic hypermotility in a rat model of irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a common disease with intestinal dysmotility, whose mechanism remains elusive. The endocannabinoid system is emerging as an important modulator of gastrointestinal (GI) motility in multiple diseases, but its involvement in IBS is unknown. We aimed to determine whether cannabinoid 2 (CB2) receptor modulates intestinal motility associated with stress-induced IBS.

METHODS

A rat IBS model was established by chronic water avoidance stress (WAS). Colonic pathological alterations were detected histologically and intestinal motility was assessed by intestinal transit time (ITT) and fecal water content (FWC). Visceral sensitivity was determined by visceromotor response (VMR) to colorectal distension (CRD). Real-time PCR, western blot, and immunostaining were performed to identify colonic CB2 receptor expression. Colonic muscle strip contractility was studied by isometric transducers and nitric oxide (NO) was detected by the Griess test. The effects of AM1241, a selective agonist of CB2 receptors, on colonic motility were examined.

KEY RESULTS

After 10 days of WAS exposure, ITT was decreased and FWC elevated while VMR magnitude in response to CRD was significantly enhanced. Colon CB2 protein and mRNA levels increased and density of CB2-positive macrophages in the mucosa and enteric neurons in the myenteric plexus was higher than in controls. Pharmacological enhancement of CB2 activity by AM1241 relieved colonic hypermotility in WAS rats in a concentration-dependent manner via inhibition of p38 phosphorylation and elevation of NO production.

CONCLUSION

CB2 receptor may exert an important inhibitory effect in stress-induced colonic hypermotility by modulating NO synthesis through p38 mitogen-activated protein kinase signaling. AM1241 could be used as a potential drug to treat disorders with colonic hypermotility.

Fluoroscopic Characterization of Colonic Dysmotility Associated to Opioid and Cannabinoid Agonists in Conscious Rats

Background/Aims

Gastrointestinal adverse effects have a major impact on health and quality of life in analgesics users. Non-invasive methods to study gastrointestinal motility are of high interest. Fluoroscopy has been previously used to study gastrointestinal motility in small experimental animals, but they were generally anesthetized and anesthesia itself may alter motility. In this study, our aim is to determine, in conscious rats, the effect of increasing doses of 2 opioid (morphine and loperamide) and 1 cannabinoid (WIN 55,212-2) agonists on colonic motility using fluoroscopic recordings and spatio-temporal maps.

Methods

Male Wistar rats received barium sulfate intragastrically, 20–22 hours before fluoroscopy, so that stained fecal pellets could be seen at the time of recording. Animals received an intraperitoneal administration of morphine, loperamide, or WIN 55,212-2 (at 0.1, 1, 5, or 10 mg/kg) or their corresponding vehicles (saline, Cremophor, and Tocrisolve, respectively), 30 minutes before fluoroscopy. Rats were conscious and placed within movement-restrainers for the length of fluoroscopic recordings (120 seconds). Spatio-temporal maps were built, and different parameters were analyzed from the fluoroscopic recordings in a blinded fashion to evaluate colonic propulsion of endogenous fecal pellets.

Results

The analgesic drugs inhibited propulsion of endogenous fecal pellets in a dose-dependent manner.

Conclusions

Fluoroscopy allows studying colonic propulsion of endogenous fecal pellets in conscious rats. Our method may be applied to the noninvasive study of the effect of different drug treatments and pathologies.

Should Cannabinoids Be Added to Multimodal Pain Regimens After Total Hip and Knee Arthroplasty?

BACKGROUND

This study investigated the effects of dronabinol on pain, nausea, and length of stay following total joint arthroplasty (TJA).

METHODS

We retrospectively compared 81 consecutive primary TJA patients who received 5 mg of dronabinol twice daily in addition to a standard multimodal pain regimen with a matched cohort of 162 TJA patients who received only the standard regimen. A single surgeon performed all surgeries. Patient demographics, length of stay, opioid morphine equivalents (MEs) consumed, reports of nausea/vomiting, discharge destination, distance walked in physical therapy, and visual analog scale pain scores were collected for both groups. Student's t-tests as well as chi-square or Mann-Whitney U-tests were used for statistical comparisons.

RESULTS

There were no significant differences between the 2 groups for age, gender, body mass index, American Society of Anesthesiologists score, anesthesia type, visual analog scale scores, distance walked with physical therapy, discharge disposition, or episodes of nausea/vomiting. The mean length of stay in the dronabinol group was significantly shorter at 2.3 ± 0.9 days versus 3.0 ± 1.2 days in the control group (P = .02). In the context of a shorter stay, the dronabinol group consumed significantly fewer total MEs (252.5 ± 131.5 vs 313.3 ± 185.4 mg, P = .0088). Although the dronabinol group consumed fewer MEs per day and per length of stay on average, neither of these achieved statistical significance. No side effects of dronabinol were reported.

CONCLUSION

These findings suggest that further investigation into the role of cannabinoid medications for non-opioid pain control in the post-arthroplasty patient may hold merit.

Activity in nodose ganglia neurons after treatment with CP 55,940 and cholecystokinin

Previous work has shown that cannabinoids increase feeding, while cholecystokinin (CCK) has an anorexigenic effect on food intake. Receptors for these hormones are located on cell bodies of vagal afferent nerves in the nodose ganglia. An interaction between CCK and endocannabinoid receptors has been suggested. The purpose of these studies is to explore the effect of pretreatment with a cannabinoid agonist, CP 55,940, on nodose neuron activation by CCK. To determine the effect of CP 55,940 and CCK on neuron activation, rats were anesthetized and nodose ganglia were excised. The neurons were dissociated and placed in culture on coverslips. The cells were treated with media; CP 55,940; CCK; CP 55,940 followed by CCK; or AM 251, a CB1 receptor antagonist, and CP 55,940 followed by CCK. Immunohistochemistry was performed to stain the cells for cFos as a measure of cell activation. Neurons were identified using neurofilament immunoreactivity. The neurons on each slip were counted using fluorescence imaging, and the number of neurons that were cFos positive was counted in order to calculate the percentage of activated neurons per coverslip. Pretreatment with CP 55,940 decreased the percentage of neurons expressing cFos-immunoreactivity in response to CCK. This observation suggests that cannabinoids inhibit CCK activation of nodose ganglion neurons.

Therapeutic potential of medicinal marijuana: an educational primer for health care professionals

With the proposed Canadian July 2018 legalization of marijuana through the Cannabis Act, a thorough critical analysis of the current trials on the efficacy of medicinal marijuana (MM) as a treatment option is necessary. This review is particularly important for primary care physicians whose patients may be interested in using MM as an alternative therapy. In response to increased interest in MM, Health Canada released a document in 2013 for general practitioners (GPs) as an educational tool on the efficacy of MM in treating some chronic and acute conditions. Although additional studies have filled in some of the gaps since the release of the Health Canada document, conflicting and inconclusive results continue to pose a challenge for physicians. This review aims to supplement the Health Canada document by providing physicians with a critical yet concise update on the recent advancements made regarding the efficacy of MM as a potential therapeutic option. An update to the literature of 2013 is important given the upcoming changes in legislation on the use of marijuana. Also, we briefly highlight the current recommendations provided by Canadian medical colleges on the parameters that need to be considered prior to authorizing MM use, routes of administration as well as a general overview of the endocannabinoid system as it pertains to cannabis. Lastly, we outline the appropriate medical conditions for which the authorization of MM may present as a practical alternative option in improving patient outcomes as well as individual considerations of which GPs should be mindful. The purpose of this paper is to offer physicians an educational tool that provides a necessary, evidence-based analysis of the therapeutic potential of MM and to ensure physicians are making decisions on the therapeutic use of MM in good faith.

Novel derivatives of 1,2,3-triazole, cannabinoid-1 receptor ligands modulate gastrointestinal motility in mice

Cannabinoid-1 (CB1) receptors are broadly distributed in the central and peripheral nervous systems; among others, they are located in the enteric nervous system. In the gastrointestinal (GI) system, they participate in regulation of intestinal motility or ion transport. The aim of our study was to assess the effect of 1,2,3-triazole derivatives (compound 1: 2-[4,5-bis(2,4-dichlorophenyl)-2H-1,2,3-triazol-2-yl]-N-(2-fluorobenzyl)acetamide, compound 2: 2-[4,5-bis(2,4-dichlorophenyl)-2H-1,2,3-triazol-2-yl]-N-(4-fluorobenzyl)acetamide, compound 3: N-benzyl-2-[4-(4-chlorophenyl)-5-(2,4-dichlorophenyl)-2H-1,2,3-triazol-2-yl]acetamide]), characterized in vitro as CB1 antagonists with high CB1 over CB2 selectivity, in the mouse GI tract. The action of compounds 1-3 was assessed in vitro (electrical field stimulated smooth muscle contractility of the mouse ileum and colon) and in vivo (whole GI transit time). Compound 1 decreased ileal (10^-6 M) and colonic (10^-7-10^-6 M) smooth muscles contractility. Moreover, it prolonged whole GI transit. Compound 2 (10^-10-10^-8 M) slightly increased the amplitude of muscle contractions in the ileum, but at a higher concentration (10^-6 M), the amplitude was decreased. Compound 2 reduced colonic contractility but accelerated GI transit. Compound 3 decreased the amplitude of intestinal muscle contractions in the ileum (10^-6 M) and colon (10^-10-10^-6 M). Moreover, it increased the GI transit time in vivo. Triazole derivatives possess easily modifiable structure and interesting pharmacological action in the GI tract; further, alterations may enhance their efficacy at CB receptors and provide low side effect profile in clinical conditions.

Medical Marijuana: Current Concepts, Pharmacological Actions of Cannabinoid Receptor Mediated Activation, and Societal Implications

PURPOSE OF REVIEW

The purpose of the following review is to summarize the history and current policies related to marijuana use and prevalence, basic and clinical science pharmacological literature regarding efficacy, subpopulations of concern, and varying policies regarding its use at present.

RECENT FINDINGS

With the increasingly widespread utilization of marijuana, there is also a growing complexity of public health policy, regulation, and necessity to further assess the medical indications and adverse long-term effects of marijuana use. Health care providers as well as the general public must be prepared to become familiar and up-to-date with medical literature, legislation, and educational material regarding medical marijuana.

Approaches to Assess Biased Signaling at the CB1R Receptor

G protein-coupled receptors, such as the cannabinoid type 1 receptor (CB1R), have been shown to interact with multiple binding partners to transmit signals. In both transfected cell systems and in endogenously expressing cell lines, CB1R signaling has been described as multifaceted. The question remains as to how this highly widely expressed receptor signals in a given cell at a given time in vivo. The concept of functional selectivity, or biased agonism, describes the ability of an agonist to engage the receptor in a manner that preferentially engages certain signaling interactions (e.g., G proteins) over others (e.g., β-arrestins), presumably by stabilizing certain receptor conformations. There is growing interest in using such properties of ligands to direct signaling downstream of CB1R toward desirable therapeutic outcomes and to avoid adverse side effects. While it is not currently clear what pathways should be engaged and which should be avoided, the development of biased agonist tool compounds will aid in answering these questions. In this chapter, we discuss the approaches and caveats to assessing biased agonism at the CB1R.

Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment-a Systematic Review

Cannabinoid hyperemesis syndrome (CHS) is a syndrome of cyclic vomiting associated with cannabis use. Our objective is to summarize the available evidence on CHS diagnosis, pathophysiology, and treatment. We performed a systematic review using MEDLINE, Ovid MEDLINE, Embase, Web of Science, and the Cochrane Library from January 2000 through September 24, 2015. Articles eligible for inclusion were evaluated using the Grading and Recommendations Assessment, Development, and Evaluation (GRADE) criteria. Data were abstracted from the articles and case reports and were combined in a cumulative synthesis. The frequency of identified diagnostic characteristics was calculated from the cumulative synthesis and evidence for pathophysiologic hypothesis as well as treatment options were evaluated using the GRADE criteria. The systematic search returned 2178 articles. After duplicates were removed, 1253 abstracts were reviewed and 183 were included. Fourteen diagnostic characteristics were identified, and the frequency of major characteristics was as follows: history of regular cannabis for any duration of time (100%), cyclic nausea and vomiting (100%), resolution of symptoms after stopping cannabis (96.8%), compulsive hot baths with symptom relief (92.3%), male predominance (72.9%), abdominal pain (85.1%), and at least weekly cannabis use (97.4%). The pathophysiology of CHS remains unclear with a dearth of research dedicated to investigating its underlying mechanism. Supportive care with intravenous fluids, dopamine antagonists, topical capsaicin cream, and avoidance of narcotic medications has shown some benefit in the acute setting. Cannabis cessation appears to be the best treatment. CHS is a cyclic vomiting syndrome, preceded by daily to weekly cannabis use, usually accompanied by symptom improvement with hot bathing, and resolution with cessation of cannabis. The pathophysiology underlying CHS is unclear. Cannabis cessation appears to be the best treatment.

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.

Abnormal cannabidiol attenuates experimental colitis in mice, promotes wound healing and inhibits neutrophil recruitment

Background

Non-psychotropic atypical cannabinoids have therapeutic potential in a variety of inflammatory conditions including those of the gastrointestinal tract. Here we examined the effects of the atypical cannabinoid abnormal cannabidiol (Abn-CBD) on wound healing, inflammatory cell recruitment and colitis in mice.

Methods

Colitis was induced in CD1 mice by a single intrarectal administration of trinitrobenzene sulfonic acid (TNBS, 4 mg/100 μl in 30 % ethanol) and Abn-CBD and/or the antagonists O-1918 (Abd-CBD), AM251 (CB₁ receptor) and AM630 (CB₂ receptor), were administered intraperitoneally (all 5 mg/kg, twice daily for 3 days). The degree of colitis was assessed macro- and microscopically and tissue myeloperoxidase activity was determined. The effects of Abn-CBD on wound healing of endothelial and epithelial cells (LoVo) were assessed in a scratch injury assay. Human neutrophils were employed in Transwell assays or perfused over human umbilical vein endothelial cells (HUVEC) to study the effect of Abn-CBD on neutrophil accumulation and transmigration.

Results

TNBS-induced colitis was attenuated by treatment with Abn-CBD. Histological, macroscopic colitis scores and tissue myeloperoxidase activity were significantly reduced. These effects were inhibited by O-1918, but not by AM630, and only in part by AM251. Wound healing of both HUVEC and LoVo cells was enhanced by Abn-CBD. Abn-CBD inhibited neutrophil migration towards IL-8, and dose-dependently inhibited accumulation of neutrophils on HUVEC.

Conclusions

Abn-CBD is protective against TNBS-induced colitis, promotes wound healing of endothelial and epithelial cells and inhibits neutrophil accumulation on HUVEC monolayers. Thus, the atypical cannabinoid Abn-CBD represents a novel potential therapeutic in the treatment of intestinal inflammatory diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-016-0129-0) contains supplementary material, which is available to authorized users.

Cannabinoids: Medical implications

Herbal cannabis has been used for thousands of years for medical purposes. With elucidation of the chemical structures of tetrahydrocannabinol (THC) and cannabidiol (CBD) and with discovery of the human endocannabinoid system, the medical usefulness of cannabinoids has been more intensively explored. While more randomized clinical trials are needed for some medical conditions, other medical disorders, like chronic cancer and neuropathic pain and certain symptoms of multiple sclerosis, have substantial evidence supporting cannabinoid efficacy. While herbal cannabis has not met rigorous FDA standards for medical approval, specific well-characterized cannabinoids have met those standards. Where medical cannabis is legal, patients typically see a physician who "certifies" that a benefit may result. Physicians must consider important patient selection criteria such as failure of standard medical treatment for a debilitating medical disorder. Medical cannabis patients must be informed about potential adverse effects, such as acute impairment of memory, coordination and judgment, and possible chronic effects, such as cannabis use disorder, cognitive impairment, and chronic bronchitis. In addition, social dysfunction may result at work/school, and there is increased possibility of motor vehicle accidents. Novel ways to manipulate the endocannbinoid system are being explored to maximize benefits of cannabinoid therapy and lessen possible harmful effects.

Palmitoylethanolamide normalizes intestinal motility in a model of post-inflammatory accelerated transit: involvement of CB₁ receptors and TRPV1 channels

BACKGROUND AND PURPOSE

Palmitoylethanolamide (PEA), a naturally occurring acylethanolamide chemically related to the endocannabinoid anandamide, interacts with targets that have been identified in peripheral nerves controlling gastrointestinal motility, such as cannabinoid CB1 and CB2 receptors, TRPV1 channels and PPARα. Here, we investigated the effect of PEA in a mouse model of functional accelerated transit which persists after the resolution of colonic inflammation (post-inflammatory irritable bowel syndrome).

EXPERIMENTAL APPROACH

Intestinal inflammation was induced by intracolonic administration of oil of mustard (OM). Mice were tested for motility and biochemical and molecular biology changes 4 weeks later. PEA, oleoylethanolamide and endocannabinoid levels were measured by liquid chromatography-mass spectrometry and receptor and enzyme mRNA expression by qRT-PCR.

KEY RESULTS

OM induced transient colitis and a functional post-inflammatory increase in upper gastrointestinal transit, associated with increased intestinal anandamide (but not 2-arachidonoylglycerol, PEA or oleoylethanolamide) levels and down-regulation of mRNA for TRPV1 channels. Exogenous PEA inhibited the OM-induced increase in transit and tended to increase anandamide levels. Palmitic acid had a weaker effect on transit. Inhibition of transit by PEA was blocked by rimonabant (CB1 receptor antagonist), further increased by 5'-iodoresiniferatoxin (TRPV1 antagonist) and not significantly modified by the PPARα antagonist GW6471.

CONCLUSIONS AND IMPLICATIONS

Intestinal endocannabinoids and TRPV1 channel were dysregulated in a functional model of accelerated transit exhibiting aspects of post-inflammatory irritable bowel syndrome. PEA counteracted the accelerated transit, the effect being mediated by CB1 receptors (possibly via increased anandamide levels) and modulated by TRPV1 channels.

Complementary and alternative medicine for gastroparesis

Complementary and alternative medicine is of great interest to patients with gastrointestinal disorders and some will choose to ask their health care providers about those therapies for which some scientific evidence exists. This review focuses on those therapies most commonly used by patients, namely acupuncture/electroacupuncture and various herbal formulations that have been the focus of clinical and laboratory investigation. A discussion of their possible mechanisms of action and the results of clinical studies are summarized.

Colon carcinogenesis is inhibited by the TRPM8 antagonist cannabigerol, a Cannabis-derived non-psychotropic cannabinoid

Cannabigerol (CBG) is a safe non-psychotropic Cannabis-derived cannabinoid (CB), which interacts with specific targets involved in carcinogenesis. Specifically, CBG potently blocks transient receptor potential (TRP) M8 (TRPM8), activates TRPA1, TRPV1 and TRPV2 channels, blocks 5-hydroxytryptamine receptor 1A (5-HT1A) receptors and inhibits the reuptake of endocannabinoids. Here, we investigated whether CBG protects against colon tumourigenesis. Cell growth was evaluated in colorectal cancer (CRC) cells using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide and 3-amino-7-dimethylamino-2-methylphenazine hydrochloride assays; apoptosis was examined by histology and by assessing caspase 3/7 activity; reactive oxygen species (ROS) production by a fluorescent probe; CB receptors, TRP and CCAAT/enhancer-binding protein homologous protein (CHOP) messenger RNA (mRNA) expression were quantified by reverse transcription-polymerase chain reaction; small hairpin RNA-vector silencing of TRPM8 was performed by electroporation. The in vivo antineoplastic effect of CBG was assessed using mouse models of colon cancer. CRC cells expressed TRPM8, CB1, CB2, 5-HT1A receptors, TRPA1, TRPV1 and TRPV2 mRNA. CBG promoted apoptosis, stimulated ROS production, upregulated CHOP mRNA and reduced cell growth in CRC cells. CBG effect on cell growth was independent from TRPA1, TRPV1 and TRPV2 channels activation, was further increased by a CB2 receptor antagonist, and mimicked by other TRPM8 channel blockers but not by a 5-HT1A antagonist. Furthermore, the effect of CBG on cell growth and on CHOP mRNA expression was reduced in TRPM8 silenced cells. In vivo, CBG inhibited the growth of xenograft tumours as well as chemically induced colon carcinogenesis. CBG hampers colon cancer progression in vivo and selectively inhibits the growth of CRC cells, an effect shared by other TRPM8 antagonists. CBG should be considered translationally in CRC prevention and cure.

Inhibition of colon carcinogenesis by a standardized Cannabis sativa extract with high content of cannabidiol

PURPOSE

Colon cancer is a major public health problem. Cannabis-based medicines are useful adjunctive treatments in cancer patients. Here, we have investigated the effect of a standardized Cannabis sativa extract with high content of cannabidiol (CBD), here named CBD BDS, i.e. CBD botanical drug substance, on colorectal cancer cell proliferation and in experimental models of colon cancer in vivo.

METHODS

Proliferation was evaluated in colorectal carcinoma (DLD-1 and HCT116) as well as in healthy colonic cells using the MTT assay. CBD BDS binding was evaluated by its ability to displace [(3)H]CP55940 from human cannabinoid CB1 and CB2 receptors. In vivo, the effect of CBD BDS was examined on the preneoplastic lesions (aberrant crypt foci), polyps and tumours induced by the carcinogenic agent azoxymethane (AOM) as well as in a xenograft model of colon cancer in mice.

RESULTS

CBD BDS and CBD reduced cell proliferation in tumoral, but not in healthy, cells. The effect of CBD BDS was counteracted by selective CB1 and CB2 receptor antagonists. Pure CBD reduced cell proliferation in a CB1-sensitive antagonist manner only. In binding assays, CBD BDS showed greater affinity than pure CBD for both CB1 and CB2 receptors, with pure CBD having very little affinity. In vivo, CBD BDS reduced AOM-induced preneoplastic lesions and polyps as well as tumour growth in the xenograft model of colon cancer.

CONCLUSIONS

CBD BDS attenuates colon carcinogenesis and inhibits colorectal cancer cell proliferation via CB1 and CB2 receptor activation. The results may have some clinical relevance for the use of Cannabis-based medicines in cancer patients.

Behavioral effects of the novel potent cannabinoid CB1 agonist AM 4054

Due to the ubiquity of the CB1 cannabinoid receptor throughout the nervous system, as well as the many potential therapeutic uses of CB1 agonist-based interventions, it is desirable to synthesize novel probes of the CB1 receptor. Here, the acute behavioral effects of systemic (i.p.) administration of the putative novel CB1 full agonist AM 4054 were tested in rats. In Experiment 1, a dose range (0.15625-1.25 mg/kg) of AM 4054 produced effects consistent with CB1 agonism in the cannabinoid tetrad of tasks in rats, including induction of analgesia, catalepsy, hypothermia, and locomotor suppression. These effects were reversed with the CB1-selective inverse agonist AM 251 in Experiment 2, indicating that AM 4054 produced CB1 receptor-mediated effects. Analysis of open-field activity indicated that the reduction in locomotion is more consistent with general motor slowing than anxiogenesis. AM 4054 (0.0625-0.5 mg/kg) also dose-dependently reduced fixed-ratio 5 (FR5) operant responding for food in Experiment 3, and microanalysis of the timing and rate of lever pressing indicated a pattern of suppression similar to other CB1 agonists. Minimum doses of AM 4054 (0.125-0.3125 mg/kg) required to produce significant effects in these behavioral assays were lower than those of many CB1 agonists. It is likely that AM 4054 is a potent pharmacological tool for assessment of cannabinoid receptor function.

Rimonabant, gastrointestinal motility and obesity

Background:

Obesity and overweight affect more than half of the US population and are associated with a number of diseases. Rimonabant, a cannabinoid receptor 1 blocker in the endocannabinoid (EC) system, was indicated in Europe for the treatment of obesity and overweight patients with associated risk factors but withdrawn on Jan, 2009 because of side effects. Many studies have reported the effects of rimonabant on gastrointestinal (GI) motility and food intake.

The aims of this review are:

to review the relationship of EC system with GI motility and food intake;

to review the studies of rimonabant on GI motility, food intake and obesity;

and to report the tolerance and side effects of rimonabant.

Methods:

the literature (Pubmed database) was searched using keywords: rimonabant, obesity and GI motility.

Results:

GI motility is related with appetite, food intake and nutrients absorption. The EC system inhibits GI motility, reduces emesis and increases food intake; Rimonabant accelerates gastric emptying and intestinal transition but decreases energy metabolism and food intake. There is rapid onset of tolerance to the prokinetic effect of rimonabant. The main side effects of rimonabant are depression and GI symptoms.

Conclusions:

Rimonabant has significant effects on energy metabolism and food intake, probably mediated via its effects on GI motility.

Inhibitory effect of cannabichromene, a major non-psychotropic cannabinoid extracted from Cannabis sativa, on inflammation-induced hypermotility in mice

BACKGROUND AND PURPOSE

Cannabichromene (CBC) is a major non-psychotropic phytocannabinoid that inhibits endocannabinoid inactivation and activates the transient receptor potential ankyrin-1 (TRPA1). Both endocannabinoids and TRPA1 may modulate gastrointestinal motility. Here, we investigated the effect of CBC on mouse intestinal motility in physiological and pathological states.

EXPERIMENTAL APPROACH

Inflammation was induced in the mouse small intestine by croton oil. Endocannabinoid (anandamide and 2-arachidonoyl glycerol), palmitoylethanolamide and oleoylethanolamide levels were measured by liquid chromatography-mass spectrometry; TRPA1 and cannabinoid receptors were analysed by quantitative RT-PCR; upper gastrointestinal transit, colonic propulsion and whole gut transit were evaluated in vivo; contractility was evaluated in vitro by stimulating the isolated ileum, in an organ bath, with ACh or electrical field stimulation (EFS).

KEY RESULTS

Croton oil administration was associated with decreased levels of anandamide (but not 2-arachidonoyl glycerol) and palmitoylethanolamide, up-regulation of TRPA1 and CB₁ receptors and down-regulation of CB₂ receptors. Ex vivo CBC did not change endocannabinoid levels, but it altered the mRNA expression of TRPA1 and cannabinoid receptors. In vivo, CBC did not affect motility in control mice, but normalized croton oil-induced hypermotility. In vitro, CBC reduced preferentially EFS- versus ACh-induced contractions. Both in vitro and in vivo, the inhibitory effect of CBC was not modified by cannabinoid or TRPA1 receptor antagonists.

CONCLUSION AND IMPLICATIONS

CBC selectively reduces inflammation-induced hypermotility in vivo in a manner that is not dependent on cannabinoid receptors or TRPA1.

Cannabidiol in inflammatory bowel diseases: a brief overview

This minireview highlights the importance of cannabidiol (CBD) as a promising drug for the therapy of inflammatory bowel diseases (IBD). Actual pharmacological treatments for IBD should be enlarged toward the search for low-toxicityand low-cost drugs that may be given alone or in combination with the conventional anti-IBD drugs to increase their efficacy in the therapy of relapsing forms of colitis. In the past, Cannabis preparations have been considered new promising pharmacological tools in view of their anti-inflammatory role in IBD as well as other gut disturbances. However, their use in the clinical therapy has been strongly limited by their psychotropic effects. CBD is a very promising compound since it shares the typical cannabinoid beneficial effects on gut lacking any psychotropic effects. For years, its activity has been enigmatic for gastroenterologists and pharmacologists, but now it is evident that this compound may interact at extra-cannabinoid system receptor sites, such as peroxisome proliferator-activated receptor-gamma. This strategic interaction makes CBD as a potential candidate for the development of a new class of anti-IBD drugs.

The thrifty lipids: endocannabinoids and the neural control of energy conservation

The 'thrifty gene hypothesis' posits that evolution preferentially selects physiological mechanisms that optimize energy storage to increase survival under alternating conditions of abundance and scarcity of food. Recent experiments suggest that endocannabinoids - a class of lipid-derived mediators that activate cannabinoid receptors in many cells of the body - are key agents of energy conservation. The new evidence indicates that these compounds increase energy intake and decrease energy expenditure by controlling the activity of peripheral and central neural pathways involved in the sensing and hedonic processing of sweet and fatty foods, as well as in the storage of their energy content for future use.

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.

Dexamethasone has additive effect when combined with ondansetron and droperidol for treatment of established PONV

BACKGROUND

Prophylactic dexamethasone, ondansetron and droperidol have a documented effect on post-operative nausea and vomiting (PONV). Still, there is a lack of studies investigating the effect of adding dexamethasone to ondansetron and droperidol in order to treat established PONV.

METHODS

In this double-blind randomised, controlled trial, we compared triple prophylaxis for PONV consisting of dexamethasone 8 mg intravenous (IV), ondansetron 4 mg IV and droperidol 0.625 mg IV (n = 157) with placebo (n = 156) given before gynaecological day-case surgery. Subsequently, in those having PONV despite triple prophylaxis or placebo, a dose of ondansetron and droperidol plus dexamethasone was compared with the combination of ondansetron and droperidol.

RESULTS

Triple prophylaxis reduced acute PONV (0-6 h) (P = 0.0003) and post-discharge PONV (6-24 h) (P = 0.001) when compared with placebo. Among those suffering from PONV despite placebo or active prophylaxis (n = 80), adding dexamethasone to ondansetron and droperidol reduced acute PONV (0-6 h) (P = 0.025) as well as post-discharge nausea (6-24 h) (P = 0.04) compared with duo treatment comprising ondansetron and droperidol. In those reporting PONV despite prophylaxis (n = 12), the treatment comprising ondansetron and droperidol, with or without dexamethasone, gave a 91.7% reduction in acute PONV and an 83.6% reduction in post-discharge PONV.

CONCLUSION

Treatment of established PONV comprising ondansetron and droperidol, with or without dexamethasone, reduced PONV in both treatment groups. In those reporting PONV without active prophylaxis, the addition of dexamethasone resulted in a significant amplification of the PONV-reducing [corrected] effects of ondansetron and droperidol.

Effects of cannabinoid agonists on sheep sphincter of oddi in vitro

BACKGROUND/AIMS

According to recent studies, the endocannabinoid system plays an important role in both physiological and pathophysiological situations. The purpose of the present study was to investigate the effects of cannabinoid (CB) agonists on isolated sheep sphincter of Oddi (SO)in vitro.

METHODS

The isolated sheep SO tissues were mounted in organ baths and tested for isometric tension and cyclic GMP levels (cGMP) in response to the non-selective CB receptor agonist WIN 55,212-2 and the potent CB1 receptor agonist methanandamide in the presence and absence of the selective CB1 antagonist SR 141716A, the selective CB2 antagonist SR 144528 and the nonspecific inhibitor of nitric oxide (NO) synthase L-NAME.

RESULTS

CB agonists relaxed SO in a concentration-dependent manner. These relaxations did not reduce in the presence of SR 144528 but were significantly reduced by SR 141716A and L-NAME. Carbachol significantly increased the cGMP levels compared with the control group and both of the CB receptor agonists significantly increased the cGMP levels compared with the control and carbachol groups. On the other hand, L-NAME prevented the increase in cGMP levels caused by CB agonists.

CONCLUSION

These results show that the relaxation by the agonists may be through CB1 receptors. The decrease of CB relaxation responses by L-NAME, a nonspecific inhibitor of NO synthase, and the increase of cGMP levels in the SO tissues by CB agonists which decreased by L-NAME show that the relaxation effects of these agonists may also partially be via increasing the NO synthesis or release.

Functional role of cannabinoid receptors in urinary bladder

Cannabinoids, the active components of Cannabis sativa (maijuana), and their derivatives produce a wide spectrum of central and peripheral effects, some of which may have clinical applications. The discovery of specific cannabinoid receptors and a family of endogenous ligands of those receptors has attracted much attention to the general cannabinoid pharmacology. In recent years, studies on the functional role of cannabinoid receptors in bladder have been motivated by the therapeutic effects of cannabinoids on voiding dysfunction in multiple sclerosis patients. In this review, we shall summarize the literature on the expression of cannabinoid receptors in urinary bladder and the peripheral influence of locally and systemically administered cannabinoids in the bladder. The ongoing search for cannabinoid-based therapeutic strategies devoid of psychotropic effects can be complemented with local delivery into bladder by the intravesical route. A greater understanding of the role of the peripheral CB₁ and CB₂ receptor system in lower urinary tract is necessary to allow the development of new treatment for pelvic disorders.

Cannabinoid-induced delayed gastric emptying is selectively increased upon intermittent administration in the rat: role of CB1 receptors

BACKGROUND

Cannabinoids acutely administered depress central, cardiovascular and gastrointestinal functions. These effects might be modified upon repeated administration. Compared to the effects induced by daily administration, those induced by intermittent administration are less known. The effect of intermittent treatment with the CB1/CB2 cannabinoid agonist WIN55,212-2 (WIN) was studied in the rat.

METHODS

Male rats received saline, vehicle or WIN at 0.5 (low-WIN) or 5 (high-WIN) mg kg(-1) week(-1) for 4 weeks. WIN effects on the central nervous system (cannabinoid tetrad tests), cardiovascular function and gastrointestinal motor function were evaluated after the first and last doses, and, where appropriate, 1 week after the last dose. To determine the involvement of CB1 receptors in the chronic effect of WIN, the CB1 receptor antagonist/inverse agonist AM251 (1 mg kg(-1)) was used.

KEY RESULTS

High- (but not low-) WIN induced the four signs of the cannabinoid tetrad, and reduced gastrointestinal motility, but did not alter cardiovascular parameters. Upon chronic intermittent administration, tolerance did not clearly develop to WIN effects. Quite the opposite, depression of gastric emptying was intensified. No effect was long-lasting. Repeated administration of AM251 was more efficacious than single administration to block WIN chronic central effects, but the opposite occurred regarding lower intestinal motility.

CONCLUSIONS & INFERENCES

Upon intermittent administration, hypersensitization may develop to some effects (particularly delayed gastric emptying) induced by cannabinoid agonists. CB1 antagonists/inverse agonists may show different efficacy upon repeated or single administration to block cannabinoid-induced central and gastrointestinal effects. Thus, cannabinoid effects are dependent on the pattern of drug administration.

Cannabinoids: potential targets for bladder dysfunction

Cannabinoids are the active chemical components of Cannabis sativa (marijuana). The medical use of cannabis goes back over 5,000 years. Cannabinoids produce a very wide array of central and peripheral effects, some of which may have beneficial clinical applications. The discovery of cannabinoid receptors has spawned great interest within the pharmaceutical industry with the hopes of capitalizing on the beneficial effects of cannabis without the unwanted psychotropic effects on the central and peripheral nervous system. This chapter presents an overview of the pharmacology of cannabinoids and their derivatives. It reviews the current literature on central and peripheral cannabinoid receptors as related to effects on the lower urinary tract and the role of these receptors in normal and abnormal urinary tract function. An objective evaluation of the published results of clinical trials of cannabis extracts for the treatment of bladder dysfunction resulting from multiple sclerosis is also presented. It is clear that cannabinoid receptors are present in the lower urinary tract as well as spinal and higher centers involved in lower urinary tract control. Systemic cannabinoids have effects on the lower urinary tract that may be able to become clinically useful; however, a much greater understanding of the mechanisms of cannabinoid receptors in control of the human lower urinary tract is necessary to facilitate development of novel cannabinoid drugs for treatment of pelvic disorders.

Peripheral CB1 cannabinoid receptor blockade improves cardiometabolic risk in mouse models of obesity

Obesity and its metabolic consequences are a major public health concern worldwide. Obesity is associated with overactivity of the endocannabinoid system, which is involved in the regulation of appetite, lipogenesis, and insulin resistance. Cannabinoid-1 receptor (CB1R) antagonists reduce body weight and improve cardiometabolic abnormalities in experimental and human obesity, but their therapeutic potential is limited by neuropsychiatric side effects. Here we have demonstrated that a CB1R neutral antagonist largely restricted to the periphery does not affect behavioral responses mediated by CB1R in the brains of mice with genetic or diet-induced obesity, but it does cause weight-independent improvements in glucose homeostasis, fatty liver, and plasma lipid profile. These effects were due to blockade of CB1R in peripheral tissues, including the liver, as verified through the use of CB1R-deficient mice with or without transgenic expression of CB1R in the liver. These results suggest that targeting peripheral CB1R has therapeutic potential for alleviating cardiometabolic risk in obese patients.

The cannabinoid antagonist SR144528 enhances the acute effect of WIN 55,212-2 on gastrointestinal motility in the rat

BACKGROUND

In the absence of pathology, cannabinoid-induced depression of gastrointestinal (GI) motility is thought to be mediated primarily by CB1 receptors, whereas the role of CB2 receptors is still unclear. The aim of this work was to radiographically analyze the acute effect of the mixed cannabinoid agonist WIN 55,212-2 (WIN) on GI motor function in the rat, focusing on the involvement of CB1 and CB2 receptors.

METHODS

Male Wistar rats received different doses of WIN and both psychoactivity (cannabinoid tetrad) and GI motility (radiographic analysis) were tested. The duration of WIN effect on GI motility was also radiographically analyzed. Finally, the involvement of the different cannabinoid receptors on WIN-induced alterations of GI motility was analyzed by the previous administration of selective CB1 (AM251) and CB2 (SR144528 or AM630) antagonists. After administration of contrast medium, alterations in GI motility were quantitatively evaluated in serial radiographs by assigning a compounded value to each region of the GI tract.

KEY RESULTS

Low, analgesic doses of WIN delayed intestinal transit, but high, psychoactive doses were required to delay gastric emptying. Acute WIN effects on GI motility were confined to the first few hours after administration. AM251 partially counteracted the effect of WIN on GI motility. Surprisingly, SR144528 (but not AM630) enhanced WIN-induced delayed gastric emptying.

CONCLUSIONS & INFERENCES

X-ray analyses confirm that cannabinoids inhibit GI motility via CB1 receptors; in addition, cannabinoids could influence motility through interaction with a SR144528-sensitive site. Further studies are needed to verify if such site of action is the CB2 receptor.

Randomized, controlled, double-blind trial of taranabant for smoking cessation

RATIONALE

It has been proposed that cannabinoid-1 receptor inverse agonists might be effective for smoking cessation. We evaluated this hypothesis with the cannabinoid-1 receptor inverse agonist taranabant.

METHODS

Adults who smoked > or =10 cigarettes a day for >1 year and had an expired CO level of > or =10 ppm participated in a randomized, double-blind, 8-week, study of taranabant (N = 159) or placebo (N = 158). Taranabant was titrated from 2 mg once daily to 8 mg once daily. Patients received smoking cessation counseling. The primary efficacy endpoint was continuous abstinence, defined as no cigarettes assessed by daily patient self-report and verified by breath CO level (<10 ppm) and plasma cotinine test (<10 ng/ml), during the last 4 weeks of the 8-week treatment period.

RESULTS

The percentage of patients achieving continuous abstinence was 7.5% for taranabant 2-8 mg and 6.3% for placebo (odds ratio = 1.2 [90% confidence interval (CI), 0.6, 2.5], P = 0.678). Change from baseline in body weight in the taranabant 2-8-mg group was -1.5 (90% CI, -1.8, -1.3) versus 0.6 kg (90% CI, 0.4, 0.9) in the placebo group. Compared to placebo, taranabant 2-8 mg was associated with an increased incidence of psychiatric-related adverse events (e.g., depression, 8.2% versus 2.5%, P = 0.048), gastrointestinal-related adverse events (e.g., nausea, 49.7% versus 19.0%, P < 0.001), and flushing/hot flash adverse events (10.7% versus 1.9%, P = 0.002).

CONCLUSIONS

Taranabant 2-8 mg did not improve smoking cessation and was associated with increased incidences of psychiatric-related, gastrointestinal-related, and flushing adverse events (ClinicalTrials.gov NCT00109135).

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.

Constitutive activity at the cannabinoid CB(1) receptor and behavioral responses

The cannabinoid receptor type 1, found mainly on cells of the central and peripheral nervous system, is a major component of the endogenous cannabinoid system. Constitutive and endogenous activity at cannabinoid receptor type 1 regulates a diverse subset of biological processes including appetite, mood, motor function, learning and memory, and pain. The complexity of cannabinoid receptor type 1 activity is not limited to the constitutive activity of the receptor: promiscuity of ligands associated with and the capability of this receptor to instigate G protein sequestration also complicates the activity of cannabinoid receptor type 1. The therapeutic use of cannabinoid receptor type 1 agonists is still a heavily debated topic, making research on the mechanisms underlying the potential benefits and risks of cannabinoid use more vital than ever. Elucidation of these mechanisms and the quest for agonists and antagonists with greater specificity will allow a greater control of the side effects and risks involved in utilizing cannabinoids as therapeutic agents. In this chapter, we review a small subset of techniques used in the pharmacological application of and the behavioral effects of molecules acting at the paradoxical cannabinoid receptor type 1.

Evaluation of [11C]PipISB and [18F]PipISB in monkey as candidate radioligands for imaging brain cannabinoid type-1 receptors in vivo

N-(4-Fluorobenzyl)-4-[3-(piperidin-1-yl)indole-1-sulfonyl]benzamide] (PipISB, 3) is a selective and high-potency cannabinoid subtype-1 (CB1) receptor inverse agonist. We have previously reported radiosyntheses of [11C]3 and [18F]3. Here, we aimed to evaluate the uptake and CB(1) receptor-specific binding of each radioligand in monkey brain in vivo with positron emission tomography (PET). [11C]3 or [18F]3 was injected intravenously into rhesus or cynomolgus monkey, respectively, and examined with PET at baseline or after pretreatment with a receptor-saturating dose of CB1 receptor-selective ligand (3 for [11C]3 or 8 for [18F]3). In one PET experiment, the dose of 3 was administered at 100 min after [11C]3. Relative plasma concentrations of radioligand and radiometabolites were concurrently measured in baseline experiments with high-performance liquid chromatography. Brain radioactivity uptake was highest in striatum and cerebellum, and it reached 170-270% standardized uptake value (SUV) at 120 min after injection of [11C]3 and 180% SUV at 240 min after injection of [18F]3. Radioactivity was well retained in all CB1 receptor-rich regions. No reference region could be identified for nonspecifically bound radioligand. Under CB1 receptor pretreatment and displacement conditions, initial brain uptakes of radioactivity were similar to those at baseline. Regional brain radioactivity concentrations then became homogeneous and diminished to between 70 and 80% SUV at 120 min after injection of [11C]3 and to 25% SUV at 240 min after injection of [18F]3. [18F]3 was not defluorinated but was metabolized to less lipophilic radiometabolites, as was [11C]3. Hence, [11C]3 and [18F]3 showed high CB1 receptor-specific binding in monkey brain in vivo and merit further investigation as prospective PET radioligands in humans.

Interaction between cannabinoid CB1 receptors and endogenous ATP in the control of spontaneous mechanical activity in mouse ileum

BACKGROUND AND PURPOSE

Although it is well accepted that cannabinoids modulate intestinal motility by reducing cholinergic neurotransmission mediated by CB(1) receptors, it is not known whether the endocannabinoids are involved in more complex circuits and if they interact with other systems. The aim of the present study was to examine possible interactions between cannabinoid CB(1) receptors and purines in the control of spontaneous contractility of longitudinal muscle in mouse ileum.

EXPERIMENTAL APPROACH

The mechanical activity of longitudinally oriented ileal segments from mice was recorded as isometric contractions.

KEY RESULTS

The selective CB(1) receptor agonist, N-(2-chloroethyl)5,8,11,14-eicosaetraenamide (ACEA) reduced, concentration dependently, spontaneous contractions in mouse ileum. This effect was almost abolished by tetrodotoxin (TTX) or atropine. Inhibition by ACEA was not affected by theophylline (P1 receptor antagonist) or by P2Y receptor desensitization with adenosine 5'[beta-thio]diphosphate trilithium salt, but was significantly reversed by pyridoxal phosphate-6-azo(benzene-2,4-disulphonic acid) (P2 receptor antagonist), by P2X receptor desensitization with alpha,beta-methyleneadenosine 5'-triphosphate lithium salt (alpha,beta-MeATP) or by 8,8'-[carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino) bis(1,3,5-naphthalenetrisulphonic acid)] (P2X receptor antagonist). Contractile responses to alpha,beta-MeATP (P2X receptor agonist) were virtually abolished by TTX or atropine, suggesting that they were mediated by acetylcholine released from neurones, and significantly reduced by ACEA.

CONCLUSION AND IMPLICATIONS

In mouse ileum, activation of CB(1) receptors, apart from reducing acetylcholine release from cholinergic nerves, was able to modulate negatively, endogenous purinergic effects, mediated by P2X receptors, on cholinergic neurons. Our study provides evidence for a role of cannabinoids in the modulation of interneuronal purinergic transmission.

Emerging strategies for exploiting cannabinoid receptor agonists as medicines

Medicines that activate cannabinoid CB(1) and CB(2) receptor are already in the clinic. These are Cesamet (nabilone), Marinol (dronabinol; Delta(9)-tetrahydrocannabinol) and Sativex (Delta(9)-tetrahydrocannabinol with cannabidiol). The first two of these medicines can be prescribed to reduce chemotherapy-induced nausea and vomiting. Marinol can also be prescribed to stimulate appetite, while Sativex is prescribed for the symptomatic relief of neuropathic pain in adults with multiple sclerosis and as an adjunctive analgesic treatment for adult patients with advanced cancer. One challenge now is to identify additional therapeutic targets for cannabinoid receptor agonists, and a number of potential clinical applications for such agonists are mentioned in this review. A second challenge is to develop strategies that will improve the efficacy and/or the benefit-to-risk ratio of a cannabinoid receptor agonist. This review focuses on five strategies that have the potential to meet either or both of these objectives. 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 up-regulated cannabinoid receptors; (iv) targeting cannabinoid CB(2) receptors; or (v) 'multi-targeting'. Preclinical data that justify additional research directed at evaluating the clinical importance of each of these strategies are also discussed.

Targeting fatty acid amide hydrolase (FAAH) to treat pain and inflammation

The endogenous cannabinoid N-arachidonoyl ethanolamine (anandamide; AEA) produces most of its pharmacological effects by binding and activating CB(1) and CB(2) cannabinoid receptors within the CNS and periphery. However, the actions of AEA are short lived because of its rapid catabolism by fatty acid amide hydrolase (FAAH). Indeed, FAAH knockout mice as well as animals treated with FAAH inhibitors are severely impaired in their ability to hydrolyze AEA as well as a variety of noncannabinoid lipid signaling molecules and consequently possess greatly elevated levels of these endogenous ligands. In this mini review, we describe recent research that has investigated the functional consequences of inhibiting this enzyme in a wide range of animal models of inflammatory and neuropathic pain states. FAAH-compromised animals reliably display antinociceptive and anti-inflammatory phenotypes with a similar efficacy as direct-acting cannabinoid receptor agonists, such as Delta(9)-tetrahydrocannabinol (THC), the primary psychoactive constituent of Cannabis sativa. Importantly, FAAH blockade does not elicit any apparent psychomimetic effects associated with THC or produce reinforcing effects that are predictive of human drug abuse. The beneficial effects caused by FAAH blockade in these models are predominantly mediated through the activation of CB(1) and/or CB(2) receptors, though noncannabinoid mechanisms of actions can also play contributory or even primary roles. Collectively, the current body of scientific literature suggests that activating the endogenous cannabinoid system by targeting FAAH is a promising strategy to treat pain and inflammation but lacks untoward side effects typically associated with Cannabis sativa.

Discovery and labeling of high-affinity 3,4-diarylpyrazolines as candidate radioligands for in vivo imaging of cannabinoid subtype-1 (CB1) receptors

Imaging of cannabinoid subtype-1 (CB1) receptors in vivo with positron emission tomography (PET) is likely to be important for understanding their role in neuropsychiatric disorders and for drug development. Radioligands for imaging with PET are required for this purpose. We synthesized new ligands from a 3,4- diarylpyrazoline platform of which (-)-12a ((-)-3-(4-chlorophenyl)-N'-[(4-cyanophenyl)sulfonyl]-4-phenyl- 4,5-dihydro-1H-pyrazole-1-carboxamidine) was found to have high-affinity and selectivity for binding to CB1 receptors. (-)-12a and its lower affinity enantiomer ((+)-12a) were labeled with carbon-11 (t1/2 ) 20.4 min) using [11C]cyanide ion as labeling agent and evaluated as PET radioligands in cynomolgus monkeys. After injection of [11C](-)-12a, there was high uptake and retention of radioactivity across brain according to the rank order of CB1 receptor densities. The distomer, [11C](+)-12a, failed to give a sustained CB1 receptor-specific distribution. Polar radiometabolites of [11C](-)-12a appeared moderately slowly in plasma. Radioligand [11C](-)-12a is promising for the study of brain CB1 receptors and merits further investigation in human subjects.

Cannabinoid CB2 receptors in the enteric nervous system modulate gastrointestinal contractility in lipopolysaccharide-treated rats

Enhanced intestinal transit due to lipopolysaccharide (LPS) is reversed by cannabinoid (CB)2 receptor agonists in vivo, but the site and mechanism of action are unknown. We have tested the hypothesis that CB2 receptors are expressed in the enteric nervous system and are activated in pathophysiological conditions. Tissues from either saline- or LPS-treated (2 h; 65 microg/kg ip) rats were processed for RT-PCR, Western blotting, and immunohistochemistry or were mounted in organ baths where electrical field stimulation was applied in the presence or absence of CB receptor agonists. Whereas the CB2 receptor agonist JWH133 did not affect the electrically evoked twitch response of the ileum under basal conditions, in the LPS-treated tissues JWH133 was able to reduce the enhanced contractile response in a concentration-dependent manner. Rat ileum expressed CB2 receptor mRNA and protein under physiological conditions, and this expression was not affected by LPS treatment. In the myenteric plexus, CB2 receptors were expressed on the majority of neurons, although not on those expressing nitric oxide synthase. LPS did not alter the distribution of CB2 receptor expression in the myenteric plexus. In vivo LPS treatment significantly increased Fos expression in both enteric glia and neurons. This enhanced expression was significantly attenuated by JWH133, whose action was reversed by the CB2 receptor antagonist AM630. Taking these facts together, we conclude that activation of CB2 receptors in the enteric nervous system of the gastrointestinal tract dampens endotoxin-induced enhanced intestinal contractility.

Cannabinoid CB(1) receptor activation modulates spontaneous contractile activity in mouse ileal longitudinal muscle

The purpose of the present study was to examine whether cannabinoid receptor agonists influence spontaneous contractile activity of longitudinal muscle in mouse ileum in vitro. Isolated segments of mouse ileum displayed spontaneous contractions with an amplitude and frequency of about 300 mg and 30 cpm, respectively. The endocannabinoid anandamide (1-100 microM), the selective cannabinoid CB(1) receptor agonist, ACEA (0.1 microM-10 microM), but not the selective cannabinoid CB(2) receptor agonist, JWH 133 (0.1 microM-10 microM), reduced in a concentration-dependent manner the spontaneous mechanical activity. The inhibitory effect consisted in a decrease of the mean amplitude of longitudinal spontaneous contractions, without changes in the resting tone. The inhibitory effect induced by cannabinoids was significantly antagonized by the selective cannabinoid CB(1) receptor antagonist, SR141716A (0.1 microM), but not by the selective cannabinoid CB(2) receptor antagonist, AM630 (0.1 microM). None of the cannabinoid antagonists, at the concentration used, did affect the spontaneous mechanical activity. The ACEA-induced reduction of spontaneous contractions was almost abolished by tetrodotoxin, atropine or apamin and it was unaffected by hexamethonium or N(omega)-nitro-l-arginine methyl ester (l-NAME), inhibitor of nitric oxide synthase. The myogenic contractions evoked by carbachol were not affected by ACEA. In conclusion, the present results suggest that activation of neural cannabinoid CB(1) receptors may play a role in the control of spontaneous mechanical activity through inhibition of acetylcholine release from cholinergic nerve. Activation of small conductance Ca(2+)-dependent K(+) channels is involved in this action.

Endocannabinoids and related compounds: walking back and forth between plant natural products and animal physiology

Cannabis sativa has been known, used, and misused by mankind for centuries, and yet only over the last two decades has research stemming from the chemical constituents specific to this plant, the cannabinoids, started to provide fundamental insights into animal physiology and pathology, resulting in the development of new therapeutics. The discovery of the endocannabinoid system, and its targeting with two new pharmaceutical preparations now on the market in several countries, represent the most recent example of how studies on medicinal plants and on the mechanism of their biological effects can reveal, through a chain of breakthroughs, new systems of endogenous signals and physiological phenomena that can become the source of novel strategies for unmet therapeutic challenges.

The endocannabinoid system and gut–brain signalling

The endocannabinoid system (ECS) consists of cannabinoid receptors, endogenous ligands and the biosynthetic and metabolic enzymes for their formation and degradation. Within the gastrointestinal (GI) tract, the ECS is involved in the regulation of motility, secretion, sensation, emesis, satiety and inflammation. Recent studies examining the ECS in the gut-brain axis have shed new light on this system and reveal many facets of regulation that are amenable to targeting by pharmacological interventions that may prove valuable for the treatment of GI disorders. In particular, it has been shown that endocannabinoid levels in the brain and gut vary according to states of satiety, and in conditions of diarrhea, emesis and inflammation. The expression of cannabinoid (CB)(1) receptors on vagal afferents is controlled by the states of satiety and by gut peptides such as cholecystokinin and ghrelin. Vagal control of gut motor function and emesis is regulated by endocannabinoids in the brainstem acting on CB(1), CB(2) and transient receptor potential vanilloid (TRPV)-1 receptors. The ECS is involved in the modulation of visceral sensation and likely contributes to effects of stress on GI function. This review examines recent developments in our understanding of the ECS in gut-brain signalling.