Volume 27, Issue 3 - Special Issue: Cannabinoids in Health and Disease / Edited by Esther Shohami (Guest Editor) and Michal Horowitz (Editor-in-Chief)

Short overviews are presented on the historical uses of cannabis in the Middle East and on the more recent scientific and medical research on phytocannabinoids and the endocannabinoid system, with emphasis on research contributions from Israel. These are followed by examples of research projects and clinical trials with cannabinoids and by a short report on the regulation of medical marijuana in Israel, which at present is administered to over 22,000 patients.

Chronic pain is an escalating public health problem. Currently available treatments are inadequate to control chronic pain conditions, and there is a critical need for novel treatments. Over a half century of elegant preclinical research has identified the presence of a sophisticated endocannabinoid system that is part of our natural pain and immune defense network. Convergent work has supported the significant potential to exploit this system to decrease pain and inflammation. Although the clinical research remains in its infancy, recent systematic reviews have found that 25 of 30 randomized controlled trials have demonstrated a significant analgesic effect. The authors concluded that cannabinoids currently available for clinical use demonstrate a modest analgesic effect and are safe for the management of chronic pain. There is a critical need for more translational research so that the excellent work of Dr. Itai Bab and our basic science colleagues around the world can move forward in providing novel cannabinoid-based medicines. This should include more potent analgesics that are limited in side effects with several routes of delivery. Our patients deserve additional agents for pain control with a novel mechanism of action, and cannabinoids are the new frontier.

The endocannabinoid system plays an important role in the control of emotions, and its dysregulation has been implicated in several psychiatric disorders. The most common self-reported reason for using cannabis is rooted in its ability to reduce feelings of stress, tension, and anxiety. Nevertheless, there are only few studies in controlled clinical settings that confirm that administration of cannabinoids can benefit patients with a post-traumatic stress disorder (PTSD). There are considerable encouraging preclinical data to suggest that endocannabinoid-targeted therapeutics for anxiety disorders should continue. In this review, we will describe data supporting a role for the endocannabinoid system in preventing and treating anxiety-like behavior in animal models and PTSD patients. Cannabinoids have shown beneficial outcomes in rat and mouse models of anxiety and PTSD, but they also may have untoward effects that discourage their chronic usage, including anxiogenic effects. Hence, clinical and preclinical research on the endocannabinoid system should further study the effects of cannabinoids on anxiety and help determine whether the benefits of using exogenous cannabinoids outweigh the risks. In general, this review suggests that targeting the endocannabinoid system represents an attractive and novel approach to the treatment of anxiety-related disorders and, in particular, PTSD.

Background: It has been shown that the brain regulates bone remodelling through sympathetic and parasympathetic nerve fibres. However, it is unclear if signals from the skeleton also influence brain functions and animal behaviours. Methods: Bone formation was conditionally disrupted by daily injections of aciclovir (10 mg/kg) to transgenic mice expressing a herpes-simplex-virus thymidine kinase under the control of the osteoblast-specific promoter of the Bglap gene. Behavioural studies were conducted after 10 weeks of treatment. Results: Transgenic mice receiving aciclovir injections showed a reduced number of osteoblasts with a concomitantly reduced trabecular bone volume density, when compared to wild-type controls that were treated identically. The general health of the animals was not severely affected, as indicated by a similar increase in body weight, similar activity profiles and similar social behaviours. However, transgenic mice showed significantly increased despair behaviour and increased adrenal gland weights. Conclusions: Specific animal behaviours can be modulated by a selective disruption of bone formation. The increased despair behaviour observed in transgenic animals indicates that these animals may be more prone to depression-related phenotypes. These findings are important in the context of the well-established clinical association between depression and reduced bone mass.

In recent years, a library of approx. 70 N -acyl aminoacids (NAAAs) was discovered in the rat brain. A particular member of this family of compounds is arachidonoyl serine (AraS), which has generated special interest as a potential therapy for traumatic brain injury (TBI). This is due to its structural similarity to the endocannabinoid (eCB) 2-arachidonoyl glycerol (2-AG), which was previously shown to be beneficial in the recovery in a closed head injury model of TBI. Indeed, AraS exerted eCB-mediated neuroprotection, which was evident in numerous aspects related to the secondary damage characterizing TBI. These findings promoted broadening of the research to additional compounds of the NAAA family that share a structural similarity to AraS, namely, palmitoyl serine (PalmS) and oleoyl serine. The latter did not exhibit any improvement in recovery, whereas the former displayed some neuroprotection, albeit inferior to 2-AG and AraS, via unknown mechanisms. Interestingly, when a combined treatment of 2-AG, AraS and PalmS was tested, the overall effect on the severity score was inferior to their individual effects, suggesting not only a lack of direct or indirect synergism, but also possibly some spatial hindrance. Taken together, the complexity of the damage caused by TBI and the many open questions concerning the role of the eCB system in health and disease, the findings so far may serve as a small trace to the understanding of the eCB system, as well as of the mechanisms underlying TBI.

A series of in vivo and in vitro assays were conducted to characterize the pharmacological effects of the first generation abused synthetic cannabinoid CP47,497, a racemic bicyclic cannabinoid that is similar in structure to the potent, high-efficacy synthetic cannabinoid CP55,940. CP47,497 was less efficacious than CP55,940 in activating G-proteins and dose-dependently produced common CB 1 receptor-dependent pharmacological effects (i.e. catalepsy, hypothermia, antinociception, and hypolocomotion). CP47,497 also substituted for Δ 9 -tetrahydrocannabinol (THC) in the mouse drug discrimination, indicating that both drugs elicited a similar interceptive stimulus. The pharmacological effects of CP47,497 underwent tolerance following repeated administration and showed cross-tolerance following repeated THC administration, further suggesting a common cannabimimetic mechanism of action. Finally, the CB 1 receptor antagonist rimonabant precipitated similar magnitudes of somatic withdrawal responses in mice treated repeatedly with THC or CP47,497. Taken together, these data verify the acute cannabimimetic effects of CP47,497, and indicate tolerance and dependence following repeated administration. The assays used here provide a straightforward approach to characterize the emerging next generation of abused synthetic cannabinoids.

Investigations into the cellular and molecular mechanisms underlying the psychoactive effects of cannabis preparations have led to the discovery of the endocannabinoid system. Interest in the central nervous system effects was initially the main focus of the research, but it soon became evident that the endocannabinoid system affects virtually every organ. The research field has therefore experienced a tremendous growth over the last decade and is now truly interdisciplinary. This short review provides a personal account of an interdisciplinary collaboration between Itai Bab from the Hebrew University of Jerusalem and the author. It describes the discovery of the endocannabinoid system in bone and the analysis of its functions. I am summarising the role of CB1 signalling as a modulator of sympathetic inhibition of bone formation. Thus, activation of CB1 receptors on sympathetic nerve terminals in bone, presumably from endocannabinoids released from apposing osteoblasts, reduces the inhibition of bone formation of sympathetic norepinephrine. CB2 receptors on osteoblasts and osteoclasts also modulate the proliferation and functions of these cells. Thus, activation of CB2 stimulates bone formation and represses bone resorption, whereas the genetic disruption of CB2 results in an osteoporosis-like phenotype. This signalling mechanism is clinically relevant, as shown by the association of polymorphisms in the CB2 receptor gene, CNR2 , with bone density and osteoporosis. Finally, the review provides a summary of the recently discovered role of endocannabinoid signalling in one elongation. This review will also discuss the benefits of interdisciplinary and international collaborations.

Recently, there has been a rapidly growing interest in the role of cannabinoids in the regulation of skeletal remodeling and bone mass, addressed in basic, translational and clinical research. Since the first publications in 2005, there are more than 1000 publications addressing the skeletal endocannabinoid system. This review focuses on the roles of the endocannabinoid system in skeletal biology via the cannabinoid receptors CB1, CB2 and others. Endocannabinoids play important roles in bone formation, bone resorption and skeletal growth, and are sometimes age, gender, species and strain dependent. Controversies in the literature and potential therapeutic approaches targeting the endocannabinoid system in skeletal disorders are also discussed.

Background: Rates of osteoporosis are significantly lower in regions of the world where olive oil consumption is a dietary cornerstone. Olive oil may represent a source of oleoyl serine (OS), which showed efficacy in animal models of osteoporosis. Here, we tested the hypothesis that OS as well as structurally analogous N -acyl amide and 2-acyl glycerol lipids are present in the following cooking oils: olive, walnut, canola, high heat canola, peanut, safflower, sesame, toasted sesame, grape seed, and smart balance omega. Methods: Methanolic lipid extracts from each of the cooking oils were partially purified on C-18 solid-phase extraction columns. Extracts were analyzed with high-performance liquid chromatography-tandem mass spectrometry, and 33 lipids were measured in each sample, including OS and bioactive analogs. Results: Of the oils screened here, walnut oil had the highest number of lipids detected (22/33). Olive oil had the second highest number of lipids detected (20/33), whereas grape-seed and high-heat canola oil were tied for lowest number of detected lipids (6/33). OS was detected in 8 of the 10 oils tested and the levels were highest in olive oil, suggesting that there is something about the olive plant that enriches this lipid. Conclusions: Cooking oils contain varying levels of bioactive lipids from the N -acyl amide and 2-acyl glycerol families. Olive oil is a dietary source of OS, which may contribute to lowered prevalence of osteoporosis in countries with high consumption of this oil.

The observation that marijuana reduces intraocular pressure was made by Hepler and Frank in the 1970s. Since then, there has been a significant body of work investigating cannabinoids for their potential use as therapeutics. To date, no endocannabinoid system (ECS)-modulating drug has been approved for clinical use in the eye; however, recent advances in our understanding of the ECS, as well as new pharmacological tools, has renewed interest in the development of ocular ECS-based therapeutics. This review summarizes the current state-of-affairs for the use of ECS-modulating drugs for the treatment of glaucoma and ocular inflammatory and ischemic disease.

Endocannabinoids (eCBs) are endogenous lipid ligands that bind to cannabinoid receptors that also mediate the effects of marijuana. The eCB system is comprised of eCBs, anandamide, and 2-arachidonoyl glycerol, their cannabinoid-1 and cannabinoid-2 receptors (CB 1 and CB 2 , respectively), and the enzymes involved in their biosynthesis and degradation. It is present in both the central nervous system and peripheral organs including the kidney. The current review focuses on the role of the eCB system in normal kidney function and various diseases, such as diabetes and obesity, that directly contributes to the development of renal pathologies. Normally, activation of the CB 1 receptor regulates renal vascular hemodynamics and stimulates the transport of ions and proteins in different nephron compartments. In various mouse and rat models of obesity and type 1 and 2 diabetes mellitus, eCBs generated in various renal cells activate CB 1 receptors and contribute to the development of oxidative stress, inflammation, and renal fibrosis. These effects can be chronically ameliorated by CB 1 receptor blockers. In contrast, activation of the renal CB 2 receptors reduces the deleterious effects of these chronic diseases. Because the therapeutic potential of globally acting CB 1 receptor antagonists in these conditions is limited due to their neuropsychiatric adverse effects, the recent development of peripherally restricted CB 1 receptor antagonists may represent a novel pharmacological approach in treating renal diseases.

Background: The mechanisms involved in the spermatotoxic effect of Cannabis sativa are inconclusive. The involvement of oxidative stress in male factor infertility has been well documented, and the antioxidative potential of melatonin and vitamin C in many oxidative stress conditions has been well reported. This study sought to investigate whether melatonin and vitamin C will ameliorate C. sativa -induced spermatotoxicity or not. Methods: Fifty-five (55) male albino rats (250–300 g) were randomly divided in a blinded fashion into five oral treatment groups as follows: group I (control, n=5) received 1 mL/kg of 10% ethanol for 30 days; groups IIa, IIb, and IIc (n=5 each) received 2 mg/kg C. sativa for 20, 30, and 40 days, respectively; groups IIIa, IIIb, and IIIc (n=5 each) received a combination of 2 mg/kg C. sativa and 4 mg/kg melatonin for 20, 30, and 40 days, respectively; groups IVa, IVb, and IVc (n=5 each) received a combination of 2 mg/kg C. sativa and 1.25 g/kg vitamin C for 20, 30, and 40 days, respectively; group V (n=5) received a combination of 2 mg/kg C. sativa , 4 mg/kg melatonin, and 1.25 g/kg vitamin C for 30 days. Results: Cannabis treatments reduced the Johnsen score, sperm count, motility, morphology, paired testicular/body weight ratio, and total antioxidant capacity, but increased lactate dehydrogenase activity. In addition, supplementation of cannabis-treated rats with either melatonin or vitamin C exacerbates the effect of cannabis on those parameters, whereas combination of melatonin and vitamin C reversed the trend to the level comparable to control. Conclusions: This study further showed the gonadotoxic effect of C. sativa , which could be mediated by oxidative stress. It also showed that melatonin and vitamin C exacerbate C. sativa -induced testicular damage when administered separately but ameliorate it when combined in rats.

Background: Dimethylheptyl-cannabidiol (DMH-CBD), a non-psychoactive, synthetic derivative of the phytocannabinoid cannabidiol (CBD), has been reported to be anti-inflammatory in RAW macrophages. Here, we evaluated the effects of DMH-CBD at the transcriptional level in BV-2 microglial cells as well as on the proliferation of encephalitogenic T cells. Methods: BV-2 cells were pretreated with DMH-CBD, followed by stimulation with the endotoxin lipopolysaccharide (LPS). The expression levels of selected genes involved in stress regulation and inflammation were determined by quantitative real-time PCR. In addition, MOG 35–55 -reactive T cells (T MOG ) were cultured with antigen-presenting cells in the presence of DMH-CBD and MOG 35–55 peptide, and cell proliferation was determined by measuring [ 3 H]thymidine incorporation. Results: DMH-CBD treatment downregulated in a dose-dependent manner the mRNA expression of LPS-upregulated pro-inflammatory genes ( Il1b , Il6 , and Tnf ) in BV-2 microglial cells. The expression of these genes was also downregulated by DMH-CBD in unstimulated cells. In parallel, DMH-CBD upregulated the expression of genes related to oxidative stress and glutathione homeostasis such as Trb3 , Slc7a11/xCT , Hmox1 , Atf4 , Chop , and p8 in both stimulated and unstimulated microglial cells. In addition, DMH-CBD dose-dependently inhibited MOG 35–55 -induced T MOG proliferation. Conclusions: The results show that DMH-CBD has similar anti-inflammatory properties to those of CBD. DMH-CBD downregulates the expression of inflammatory cytokines and protects the microglial cells by inducing an adaptive cellular response against inflammatory stimuli and oxidative injury. In addition, DMH-CBD decreases the proliferation of pathogenic activated T MOG cells.

G protein-coupled receptor 55 (GPR55) shares numerous cannabinoid ligands with CB1 and CB2 receptors despite low homology with those classical cannabinoid receptors. The pharmacology of GPR55 is not yet fully elucidated; however, GPR55 utilizes a different signaling system and downstream cascade associated with the receptor. Therefore, GPR55 has emerged as a putative “type 3” cannabinoid receptor, establishing a novel class of cannabinoid receptor. Furthermore, the recent evidence of GPR55-CB1 and GPR55-CB2 heteromerization along with its broad distribution from central nervous system to peripheries suggests the importance of GPR55 in various cellular processes and pathologies and as a potential therapeutic target in inflammation.

Background: GPR55 is a lipid-sensing G protein-coupled receptor that is activated by the endogenous lipid l -α-lysophosphatidylinositol (LPI) and can be modulated by certain cannabinoid ligands. Methods: In this study we investigated the GPR55 activity of four synthetic CB 2 receptor agonists using the AlphaScreen ® SureFire ® assay. Results: Here we show that the CB 2 receptor-selective agonists HU-308, HU-433 and HU-910 do not promote GPR55-mediated ERK1/2 phosphorylation up to a concentration of 3 μM. However, LPI-induced ERK1/2 phosphorylation is inhibited by the (–)-enantiomer of HU-308, designated HU-433, whereas HU-308 has no effect on LPI activity. The carboxylic analogue of HU-910, designated HU-914, potently inhibits LPI-induced ERK1/2 phosphorylation; however, HU-914 was less effective, with potential biphasic effects. Conclusions: This structure-activity-relationship study has identified novel ligands which act both as CB 2 receptor agonists and GPR55 modulators and related compounds that lack GPR55 activity.

Background: CB 1 cannabinoid receptors (CB 1 Rs) stimulate Gi/o-dependent signaling pathways. CB 1 R-mediated cAMP increases were proposed to result from Gs activation, but CB 1 R-stimulated GTPγS binding to Gs has not heretofore been investigated. Methods: Three models of CB 1 R-stimulated cAMP production were tested: pertussis toxin disruption of Gi/o in N18TG2 cells; L341A/A342L-CB 1 R expressed in Chinese hamster ovary (CHO) cells; and CB 1 and D 2 dopamine receptors endogenously co-expressed in MN9D cells. cAMP was assayed by [ 3 H]cAMP binding competition. G protein activation was assayed by the antibody-targeted scintillation proximity assay. Results: In L341A/A342L-CB 1 -CHO cells, cannabinoid agonists significantly stimulated cAMP accumulation over vehicle; (–)-3-[2-hydroxyl-4-(1,1-dimethylheptyl)phenyl]-4-[3-hydroxyl propyl] cyclohexan-1-ol (CP55940)-stimulated [ 35 S]GTPγS binding to Gi1/2/3 was reversed, whereas binding to Gs was not different from CB 1 R. In MN9D cells, CB 1 agonist HU210 or D 2 agonist quinpirole alone inhibited forskolin-activated cAMP accumulation, whereas HU210 plus quinpirole increased cAMP accumulation above basal. HU210 alone stimulated [ 35 S]GTPγS binding to Gi1/2/3, whereas co-stimulation with quinpirole reversed HU210-stimulated [ 35 S]GTPγS binding to Gi1/2/3. Conclusions: CB 1 R couples to Gs but with low efficacy compared to Gi/o. The L341A/A342L mutation in CB 1 R reversed CP55940 activation of Gi to an inhibition, but had no effect on Gs. Combined CB 1 plus D 2 agonists in MN9D cells converted the CB 1 agonist-mediated activation of Gi to inhibition of Gi. In these models, the CB 1 agonist response was converted to an inverse agonist response at Gi activation. Cannabinoid agonist-stimulated cAMP accumulation can be best explained as reduced activation of Gi, thereby attenuating the tonic inhibitory influence of Gi on the major isoforms of adenylyl cyclase.