(-)-Delta9-tetrahydrocannabinol antagonizes the peripheral cannabinoid receptor-mediated inhibition of adenylyl cyclase

Effects of in utero delta-9-tetrahydrocannabinol (THC) exposure on fetal and infant musculoskeletal development in a preclinical nonhuman primate model

The endocannabinoid system (ECS) plays a major role in the maintenance of bodily homeostasis and adaptive response to external insults. It has been shown to regulate crucial physiological processes and behaviors, spanning nervous functions, anxiety, cognition, and pain sensation. Due to this broad activity, the ECS has been explored as a potential therapeutic target in the treatment of select diseases. However, until there is a more comprehensive understanding of how ECS activation by exogenous and endogenous ligands manifests across disparate tissues and cells, discretion should be exercised. Previous work has investigated how endogenous cannabinoid signaling impacts skeletal muscle development and differentiation. However, the effects of activation of the ECS by delta-9-tetrahydrocannabinol (THC, the most psychoactive component of cannabis) on skeletal muscle development, particularly in utero, remain unclear. To address this research gap, we used a highly translational non-human primate model to examine the potential impact of chronic prenatal THC exposure on fetal and infant musculoskeletal development. RNA was isolated from the skeletal muscle and analyzed for differential gene expression using a Nanostring nCounter neuroinflammatory panel comprised of 770 genes. Histomorphological evaluation of muscle morphology and composition was also performed. Our findings suggest that while prenatal THC exposure had narrow overall effects on fetal and infant muscle development, the greatest impacts were observed within pathways related to inflammation and cytokine signaling, which suggest the potential for tissue damage and atrophy. This pilot study establishes feasibility to evaluate neuroinflammation due to prenatal THC exposure and provides rationale for follow-on studies that explore the longer-term implications and functional consequences encountered by offspring as they continue to mature.

Using In Silico Molecular Docking to Explain Differences in Receptor Binding Behavior of HHC and THCV Isomers: Revealing New Binding Modes

Even slight structural differences between phytocannabinoid isomers are usually enough to cause a change in their biological properties. In this study, we used in vitro CB1 agonism/antagonism assays to compare the receptor binding functionality of THCV (tetrahydrocannabivarin) and HHC (hexahydrocannabinol) isomers and applied molecular docking to provide an explanation for the difference in the activities. No CB1 agonism was observed for ∆9- and ∆8-THCV. Instead, both isomers antagonized CP 55940, with ∆9-THCV being approximately two times more potent than the ∆8 counterpart (IC50 = 52.4 nM and 119.6 nM for ∆9- and ∆8-THCV, respectively). Docking simulations found two binding poses for THCV isomers, one very similar to ∆9-THC and one newly discovered pose involving the occupation of side pocket 1 of the CB1 receptor by the alkyl chain of the ligand. We suggested the latter as a potential antagonist pose. In addition, our results established 9R-HHC and 9S-HHC among partial agonists of the CB1 receptor. The 9R-HHC (EC50 = 53.4 nM) isomer was a significantly more potent agonist than 9S (EC50 = 624.3 nM). ∆9-THC and 9R-HHC showed comparable binding poses inside the receptor pocket, whereas 9S-HHC adopted a new and different binding posture that can explain its weak agonist activity.

Endocannabinoid signaling in the central nervous system

It is hard to overestimate the influence of the endocannabinoid signaling (ECS) system on central nervous system (CNS) function. In the 40 years since cannabinoids were found to trigger specific cell signaling cascades, studies of the ECS system continue to cause amazement, surprise, and confusion! CB1 cannabinoid receptors are expressed widely in the CNS and regulate cell-cell communication via effects on the release of both neurotransmitters and gliotransmitters. CB2 cannabinoid receptors are difficult to detect in the CNS but seem to "punch above their weight" as compounds targeting these receptors have significant effects on inflammatory state and behavior. Positive and negative allosteric modulators for both receptors have been identified and examined in preclinical studies. Concentrations of the endocannabinoid ligands, N-arachidonoylethanolamine and 2-arachidonoylglycerol (2-AG), are regulated by a combination of enzymatic synthesis and degradation and inhibitors of these processes are available and making their way into clinical trials. Importantly, ECS regulates many essential brain functions, including regulation of reward, anxiety, inflammation, motor control, and cellular development. While the field is on the cusp of preclinical discoveries providing impactful clinical and therapeutic insights into many CNS disorders, there is still much to be learned about this remarkable and versatile modulatory system.

A critical review of cannabis in medicine and dentistry: A look back and the path forward

Introduction

In the last two decades, our understanding of the therapeutic utility and medicinal properties of cannabis has greatly changed. This change has been accompanied by widespread cannabis use in various communities and different age groups, especially within the United States. With this increase, we should consider the potential effects of cannabis–hemp on general public health and how they could alter therapeutic outcomes.

Material and Methods

The present investigation examined cannabis use for recreational and therapeutic use and a review of pertinent indexed literature was performed. The focused question evaluates “how cannabis or hemp products impact health parameters and do they provide potential therapeutic value in dentistry, and how do they interact with conventional medicines (drugs).” Indexed databases (PubMed/Medline, EMBASE) were searched without any time restrictions but language was restricted to English.

Results

The review highlights dental concerns of cannabis usage, the need to understand the endocannabinoid system (ECS), cannabinoid receptor system, its endogenous ligands, pharmacology, metabolism, current oral health, and medical dilemma to ascertain the detrimental or beneficial effects of using cannabis–hemp products. The pharmacological effects of pure cannabidiol (CBD) have been studied extensively while cannabis extracts can vary significantly and lack empirical studies. Several metabolic pathways are affected by cannabis use and could pose a potential drug interaction. The chronic use of cannabis is associated with health issues, but the therapeutic potential is multifold since there is a regulatory role of ECS in many pathologies.

Conclusion

Current shortcomings in understanding the benefits of cannabis or hemp products are limited due to pharmacological and clinical effects not being predictable, while marketed products vary greatly in phytocompounds warrant further empirical investigation. Given the healthcare challenges to manage acute and chronic pain, this review highlights both cannabis and CBD‐hemp extracts to help identify the therapeutic application for patient populations suffering from anxiety, inflammation, and dental pain.

Parkinson's disease related alterations in cannabinoid transmission

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic (DAergic) neurons of the substantia nigra pars compacta (SNc) by neurodegeneration. Recent findings in animal models of PD propose tonic inhibition of the remaining DA neurons through GABA release from reactive glial cells. Movement dysfunctions could be ameliorated by promotion of activity in dormant DA cells. The endocannabinoid system (ECS) is extensively present in basal ganglia (BG) and is known as an indirect modulator of DAergic neurotransmission, thus drugs designed to target this system have shown promising therapeutic potential in PD patients. Interestingly, down/up-regulation of cannabinoid receptors (CBRs) varies across the different stages of PD, suggesting that some of the motor/ non-motor deficits may be related to changes in CBRs. Determination of the profile of changes of these receptors across the different stages of PD as well as their neural distribution within the BG could improve understanding of PD and identify pathways important in disease pathobiology. In this review, we focus on temporal and spatial alterations of CBRs during PD in the BG. At present, as inconclusive, but suggestive results have been obtained, future investigations should be conducted to extend preclinical studies examining CBRs changes within each stage in controlled clinical trials in order to determine the potential of targeting CBRs in management of PD.

Similarities and differences upon binding of naturally occurring Δ9-tetrahydrocannabinol-derivatives to cannabinoid CB1 and CB2 receptors

We have here assessed, using Δ⁹-tetrahydrocannabinol (Δ⁹-THC) for comparison, the effect of Δ⁹-tetrahydrocannabinolic acid (Δ⁹-THCA) and of Δ⁹-tetrahydrocannabivarin (Δ9-THCV) that is mediated by human versions of CB₁, CB₂, and CB₁-CB₂ receptor functional units, expressed in a heterologous system. Binding to the CB₁ and CB₂ receptors was addressed in living cells by means of a homogeneous assay. A biphasic competition curve for the binding to the CB₂ receptor, was obtained for Δ⁹-THCV in cells expressing the two receptors. Signaling studies included cAMP level determination, activation of the mitogen-activated protein kinase pathway and ß-arrestin recruitment were performed. The signaling triggered by Δ⁹-THCA and Δ⁹-THCV via individual receptors or receptor heteromers disclosed differential bias, i.e. the bias observed using a given phytocannabinoid depended on the receptor (CB₁, CB₂ or CB₁-CB₂) and on the compound used as reference to calculate the bias factor (Δ⁹-THC, a selective agonist or a non-selective agonist). These results are consistent with different binding modes leading to differential functional selectivity depending on the agonist structure, and the state (monomeric or heteromeric) of the cannabinoid receptor. In addition, on studying Gi-coupling we showed that Δ⁹-THCV and Δ⁹-THCA and Δ⁹-THCV were able to revert the effect of a selective CB₂ receptor agonist, but only Δ9-THCV, and not Δ9-THCA, reverted the effect of arachidonyl-2'-chloroethylamide (ACEA 100 nM) a selective agonist of the CB₁ receptor. Overall, these results indicate that cannabinoids may have a variety of binding modes that results in qualitatively different effects depending on the signaling pathway that is engaged upon cannabinoid receptor activation.

Major Phytocannabinoids and Their Related Compounds: Should We Only Search for Drugs That Act on Cannabinoid Receptors?

The most important discoveries in pharmacology, such as certain classes of analgesics or chemotherapeutics, started from natural extracts which have been found to have effects in traditional medicine. Cannabis, traditionally used in Asia for the treatment of pain, nausea, spasms, sleep, depression, and low appetite, is still a good candidate for the development of new compounds. If initially all attention was directed to the endocannabinoid system, recent studies suggest that many of the clinically proven effects are based on an intrinsic chain of mechanisms that do not necessarily involve only cannabinoid receptors. Recent research has shown that major phytocannabinoids and their derivatives also interact with non-cannabinoid receptors such as vanilloid receptor 1, transient receptor ankyrin 1 potential, peroxisome proliferator-activated receptor-gamma or glitazone receptor, G55 protein-coupled receptor, and nuclear receptor, producing pharmacological effects in diseases such as Alzheimer's, epilepsy, depression, neuropathic pain, cancer, and diabetes. Nonetheless, further studies are needed to elucidate the precise mechanisms of these compounds. Structure modulation of phytocannabinoids, in order to improve pharmacological effects, should not be limited to the exploration of cannabinoid receptors, and it should target other courses of action discovered through recent research.

Repurposing Cannabidiol as a Potential Drug Candidate for Anti-Tumor Therapies

In recent years, evidence has accumulated that cannabinoids-especially the non-psychoactive compound, cannabidiol (CBD)-possess promising medical and pharmacological activities that might qualify them as potential anti-tumor drugs. This review is based on multiple studies summarizing different mechanisms for how CBD can target tumor cells including cannabinoid receptors or other constituents of the endocannabinoid system, and their complex activation of biological systems that results in the inhibition of tumor growth. CBD also participates in anti-inflammatory activities which are related to tumor progression, as demonstrated in preclinical models. Although the numbers of clinical trials and tested tumor entities are limited, there is clear evidence that CBD has anti-tumor efficacy and is well tolerated in human cancer patients. In summary, it appears that CBD has potential as a neoadjuvant and/or adjuvant drug in therapy for cancer.

Signaling through the type 2 cannabinoid receptor regulates the severity of acute and chronic graft-versus-host disease

Graft-versus-host disease (GVHD) pathophysiology is a complex interplay between cells that comprise the adaptive and innate arms of the immune system. Effective prophylactic strategies are therefore contingent upon approaches that address contributions from both immune cell compartments. In the current study, we examined the role of the type 2 cannabinoid receptor (CB2R), which is expressed on nearly all immune cells, and demonstrated that absence of the CB2R on donor CD4+ or CD8+ T cells or administration of a selective CB2R pharmacological antagonist exacerbated acute GVHD lethality. This was accompanied primarily by the expansion of proinflammatory CD8+ T cells, indicating that constitutive CB2R expression on T cells preferentially regulated CD8+ T-cell alloreactivity. Using a novel CB2ReGFP reporter mouse, we observed significant loss of CB2R expression on T cells, but not macrophages, during acute GVHD, indicative of differential alterations in receptor expression under inflammatory conditions. Therapeutic targeting of the CB2R with the agonists Δ9-tetrahydrocannabinol (THC) and JWH-133 revealed that only THC mitigated lethal T cell-mediated acute GVHD. Conversely, only JWH-133 was effective in a sclerodermatous chronic GVHD model where macrophages contributed to disease biology. In vitro, both THC and JWH-133 induced arrestin recruitment and extracellular regulated kinase phosphorylation via CB2R, but THC had no effect on CB2R-mediated inhibition of adenylyl cyclase. This study shows that the CB2R plays a critical role in the regulation of GVHD and suggests that effective therapeutic targeting is dependent upon agonist signaling characteristics and receptor selectivity in conjunction with the composition of pathogenic immune effector cells.

The endocannabinoid system

Thirty years ago, the discovery of a cannabinoid (CB) receptor that interacts with the psychoactive compound in Cannabis led to the identification of anandamide, an endogenous receptor ligand or endocannabinoid. Research on endocannabinoids has since exploded, and additional receptors along with their lipid mediators and signaling pathways continue to be revealed. Specifically, in humans, the release of endocannabinoids from membrane lipids occurs on demand and the signaling process is rapidly attenuated by the breakdown of the ligand suggesting a tight regulation of the endocannabinoid system (ECS). Additionally, the varying distribution of CB receptors between the central nervous system and other tissues allows for the ECS to participate in a wide range of cognitive and physiological processes. Select plant-derived 'phyto'cannabinoids such as Δ-9-tetrahydrocannabinol (Δ9-THC) bind to the CB receptors and trigger the ECS, and in the case of Δ9-THC, while it has therapeutic value, can also produce detrimental effects. Current research is aimed at the identification of additional phytocannabinoids with minimal psychotropic effects with potential for therapeutic development. Although decades of research on the ECS and its components have expanded our understanding of the mechanisms and implications of endocannabinoid signaling in mammals, it continues to evolve. Here, we provide a brief overview of the ECS and its overlap with other related lipid-mediated signaling pathways.

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

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

Cannabichromene is a cannabinoid CB2 receptor agonist

BACKGROUND AND PURPOSE

Cannabichromene (CBC) is one of the most abundant phytocannabinoids in Cannabis spp. It has modest antinociceptive and anti-inflammatory effects and potentiates some effects of Δ⁹ -tetrahydrocannabinol in vivo. How CBC exerts these effects is poorly defined and there is little information about its efficacy at cannabinoid receptors. We sought to determine the functional activity of CBC at cannabinoid CB₁ and CB₂ receptors.

EXPERIMENTAL APPROACH

AtT20 cells stably expressing haemagglutinin-tagged human CB₁ and CB₂ receptors were used. Assays of cellular membrane potential and loss of cell surface receptors were performed.

KEY RESULTS

CBC activated CB₂ but not CB₁ receptors to produce hyperpolarization of AtT20 cells. This activation was inhibited by a CB₂ receptor antagonist AM630, and sensitive to Pertussis toxin. Application of CBC reduced activation of CB₂ , but not CB₁ , receptors by subsequent co-application of CP55,940, an efficacious CB₁ and CB₂ receptor agonist. Continuous CBC application induced loss of cell surface CB₂ receptors and desensitization of the CB₂ receptor-induced hyperpolarization.

CONCLUSIONS AND IMPLICATIONS

CBC is a selective CB₂ receptor agonist displaying higher efficacy than tetrahydrocannabinol in hyperpolarizing AtT20 cells. CBC can also recruit CB₂ receptor regulatory mechanisms. CBC may contribute to the potential therapeutic effectiveness of some cannabis preparations, potentially through CB₂ receptor-mediated modulation of inflammation.

Extractions of Medical Cannabis Cultivars and the Role of Decarboxylation in Optimal Receptor Responses

Introduction: Phytocannabinoids, characteristic compounds produced by medical cannabis, interact with cannabinoid (CB) receptors (CB1 and CB2) as well as other receptor systems to exhibit their corresponding pharmacological effects. In their natural form, CBs such as Δ9-tetrahydrocannabinolic acid and cannabidiolic acid are inactive at these receptors, while their decarboxylated forms (Δ9-tetrahydrocannabinol and cannabidiol, respectively) are potent ligands at CB receptors. Thus, extraction and processing of medical cannabis for active constituents are important. Purpose and Methods: Patients consuming medical cannabis often have limited alternative treatment options and in recent years, medical cannabis extracts have been popular as a substitute for dried cannabis plants, despite limited studies on these derivatives. We investigated three disparate cannabis cultivars and compared four chemical extraction methods head to head, viz. Soxhlet, ultrasound-assisted supercritical fluid, and microwave-assisted extractions, for their efficiency. We further characterized the chemical compositions of these extracts. Results: Microwave extraction consistently produced completely decarboxylated phytocannabinoid extracts. Factors such as temperature and exposure time play important roles in the decarboxylation of phytocannabinoids, thereby generating pharmacologically active CBs, and these conditions may differ for each cannabis cultivar. Conclusion: Chemical consistency and potency due to active compounds are in turn important in producing consistent and reliable medical cannabis extracts and their derivatives. These processes must be subject to higher levels of scientific rigor as the patient population around the world are seeking the help of such extracts for various clinical conditions, and as medical cannabis industry is receiving acceptance in various countries.

Enzymatic analysis of glucuronidation of synthetic cannabinoid 1-naphthyl 1-(4-fluorobenzyl)-1H-indole-3-carboxylate (FDU-PB-22)

Recently, there has been a rise in abuse of synthetic cannabinoids (SCBs). The consumption of SCBs results in various effects and can induce toxic reactions, including paranoia, seizures, tachycardia and even death. 1-Naphthyl 1-(4-fluorobenzyl)-1H-indole-3-carboxylate (FDU-PB-22) is a third generation SCB whose metabolic pathway has not been fully characterized. In this study, we conducted in vitro pharmacokinetic analysis of FDU-PB-22 metabolism. Metabolic reactions containing FDU-PB-22 and human liver microsomes (HLMs) were independent of NADPH but not UDP-glucuronic acid (UDPGA), suggesting that UDP-glucuronosyltransferases (UGTs) are the primary enzymes involved in this metabolism. It was further determined that the metabolite extensively formed after incubating FDU-PB-22 with UDPGA in HLMs was the glucuronide of FDU-PB-22 3-carboxyindole (FBI-COOH). Various hepatic UGTs showed enzymatic activity for FBI-COOH. A series of UGT inhibitors showed moderate to strong inhibition of FBI-COOH-glucuronidation in HLMs, suggesting that multiple UGT isoforms are involved in FBI-COOH-glucuronidation in the liver. Interestingly, an extra-hepatic isoform, UGT1A10, exhibited the highest activity with a K_m value of 38 µM and a V_max value of 5.90 nmol/min/mg. Collectively, these results suggest that both genetic mutations of and the co-administration of inhibitors for FDU-PB-22-metabolizing UGTs will likely increase the risk of FDU-PB-22-induced toxicity.

An overview of the cannabinoid type 2 receptor system and its therapeutic potential

PURPOSE OF REVIEW

This narrative review summarizes recent insights into the role of the cannabinoid type 2 (CB2) receptor as potential therapeutic target in neuropathic pain and neurodegenerative conditions.

RECENT FINDINGS

The cannabinoid system continues to receive attention as a therapeutic target. The CB2 receptor is primarily expressed on glial cells only when there is active inflammation and appears to be devoid of undesired psychotropic effects or addiction liability. The CB2 receptor has been shown to have potential as a therapeutic target in models of diseases with limited or no currently approved therapies, such as neuropathic pain and neurodegenerative conditions such as Alzheimer's disease.

SUMMARY

The functional involvement of CB2 receptor in neuropathic pain and other neuroinflammatory diseases highlights the potential therapeutic role of drugs acting at the CB2 receptor.

Decisive role of P42/44 mitogen-activated protein kinase in Δ9-tetrahydrocannabinol-induced migration of human mesenchymal stem cells

In past years, medical interest in Δ⁹-tetrahydrocannabinol (THC), the major psychoactive ingredient of the Cannabis plant, has been renewed due to the elucidation of the endocannabinoid system and diverse other receptor targets involved in biological cannabinoid effects. The present study therefore investigates the impact of THC on the migration of mesenchymal stem cells (MSCs) which are known to be involved in various regenerative processes such as bone healing. Using Boyden chamber assays, THC was found to increase the migration of adipose-derived MSCs. Migration by THC was almost completely suppressed by the CB₁ receptor antagonist AM-251 and to a lesser extent by the CB₂ receptor antagonist AM-630. By contrast, the TRPV1 antagonist capsazepine as well as the G protein-coupled receptor 55 (GRP55) agonist O-1602 did not significantly interfere with the promigratory effect of THC. Furthermore, increased migration by THC was fully suppressed by PD98059, an inhibitor of p42/44 mitogen-activated protein kinase (MAPK) activation, and was accompanied by a time-dependent activation of this pathway accordingly. In line with the migration data, additional inhibitor experiments pointed towards a decisive role of the CB₁ receptor in conferring THC-induced activation of p42/44 MAPK. Collectively, this study demonstrates THC to exert a promigratory effect on MSCs via a CB₁ receptor-dependent activation of p42/44 MAPK phosphorylation. This pathway may be involved in regenerative effects of THC and could be a target of pharmacological intervention.

Effect fingerprinting of new psychoactive substances (NPS): What can we learn from in vitro data?

The use of new psychoactive substances (NPS) is increasing and currently >600 NPS have been reported. However, limited information on neuropharmacological and toxicological effects of NPS is available, hampering risk characterization. We reviewed the literature on the in vitro neuronal modes of action to obtain effect fingerprints of different classes of illicit drugs and NPS. The most frequently reported NPS were selected for review: cathinones (MDPV, α-PVP, mephedrone, 4-MEC, pentedrone, methylone), cannabinoids (JWH-018), (hallucinogenic) phenethylamines (4-fluoroamphetamine, benzofurans (5-APB, 6-APB), 2C-B, NBOMes (25B-NBOMe, 25C-NBOMe, 25I-NBOMe)), arylcyclohexylamines (methoxetamine) and piperazine derivatives (mCPP, TFMPP, BZP). Our effect fingerprints highlight the main modes of action for the different NPS studied, including inhibition and/or reversal of monoamine reuptake transporters (cathinones and non-hallucinogenic phenethylamines), activation of 5-HT₂receptors (hallucinogenic phenethylamines and piperazines), activation of cannabinoid receptors (cannabinoids) and inhibition of NDMA receptors (arylcyclohexylamines). Importantly, we identified additional targets by relating reported effect concentrations to the estimated human brain concentrations during recreational use. These additional targets include dopamine receptors, α- and β-adrenergic receptors, GABA_Areceptors and acetylcholine receptors, which may all contribute to the observed clinical symptoms following exposure. Additional data is needed as the number of NPS continues to increase. Also, the effect fingerprints we have obtained are still incomplete and suffer from a large variation in the reported effects and effect sizes. Dedicated in vitro screening batteries will aid in complementing specific effect fingerprints of NPS. These fingerprints can be implemented in the risk assessments of NPS that are necessary for eventual control measures to reduce Public Health risks.

CB1 and CB2 Receptor Pharmacology

The CB1 and CB2 cannabinoid receptors (CB1R, CB2R) are members of the G protein-coupled receptor (GPCR) family that were identified over 20 years ago. CB1Rs and CB2Rs mediate the effects of Δ9-tetrahydrocannabinol (Δ9-THC), the principal psychoactive constituent of marijuana, and subsequently identified endogenous cannabinoids (endocannabinoids) anandamide and 2-arachidonoyl glycerol. CB1Rs and CB2Rs have both similarities and differences in their pharmacology. Both receptors recognize multiple classes of agonist and antagonist compounds and produce an array of distinct downstream effects. Natural polymorphisms and alternative splice variants may also contribute to their pharmacological diversity. As our knowledge of the distinct differences grows, we may be able to target select receptor conformations and their corresponding pharmacological responses. This chapter will discuss their pharmacological characterization, distribution, phylogeny, and signaling pathways. In addition, the effects of extended agonist exposure and how that affects signaling and expression patterns of the receptors are considered.

Molecular Targets of the Phytocannabinoids: A Complex Picture

For centuries, hashish and marihuana, both derived from the Indian hemp Cannabis sativa L., have been used for their medicinal, as well as, their psychotropic effects. These effects are associated with the phytocannabinoids which are oxygen containing C₂₁ aromatic hydrocarbons found in Cannabis sativa L. To date, over 120 phytocannabinoids have been isolated from Cannabis. For many years, it was assumed that the beneficial effects of the phytocannabinoids were mediated by the cannabinoid receptors, CB₁ and CB₂. However, today we know that the picture is much more complex, with the same phytocannabinoid acting at multiple targets. This contribution focuses on the molecular pharmacology of the phytocannabinoids, including Δ⁹-THC and CBD, from the prospective of the targets at which these important compounds act.

Molecular Pharmacology of Phytocannabinoids

Cannabis sativa has been used for recreational, therapeutic and other uses for thousands of years. The plant contains more than 120 C₂₁ terpenophenolic constituents named phytocannabinoids. The Δ⁹-tetrahydrocannabinol type class of phytocannabinoids comprises the largest proportion of the phytocannabinoid content. Δ⁹-tetrahydrocannabinol was first discovered in 1971. This led to the discovery of the endocannabinoid system in mammals, including the cannabinoid receptors CB₁ and CB₂. Δ⁹-Tetrahydrocannabinol exerts its well-known psychotropic effects through the CB₁ receptor but this effect of Δ⁹-tetrahydrocannabinol has limited the use of cannabis medicinally, despite the therapeutic benefits of this phytocannabinoid. This has driven research into other targets outside the endocannabinoid system and has also driven research into the other non-psychotropic phytocannabinoids present in cannabis. This chapter presents an overview of the molecular pharmacology of the seven most thoroughly investigated phytocannabinoids, namely Δ⁹-tetrahydrocannabinol, Δ⁹-tetrahydrocannabivarin, cannabinol, cannabidiol, cannabidivarin, cannabigerol, and cannabichromene. The targets of these phytocannabinoids are defined both within the endocannabinoid system and beyond. The pharmacological effect of each individual phytocannabinoid is important in the overall therapeutic and recreational effect of cannabis and slight structural differences can elicit diverse and competing physiological effects. The proportion of each phytocannabinoid can be influenced by various factors such as growing conditions and extraction methods. It is therefore important to investigate the pharmacology of these seven phytocannabinoids further, and characterise the large number of other phytocannabinoids in order to better understand their contributions to the therapeutic and recreational effects claimed for the whole cannabis plant and its extracts.

Endo-cannabinoids system and the toxicity of cannabinoids with a biotechnological approach

Cannabinoids have shown diverse and critical effects on the body systems, which alter the physiological functions. Synthetic cannabinoids are comparatively innovative misuse drugs with respect to their nature of synthesis. Synthetic cannabinoids therapy in healthy, chain smokers, and alcoholic individuals cause damage to the immune and nervous system, eventually leading to intoxication throughout the body. Relevant studies were retrieved using major electronic databases such as PubMed, EMBASE, Medline, Scopus, and Google Scholar. The extensive use of Cannabis Sativa L. (C. Sativa) and its derivatives/analogues such as the nonpsychoactive dimethyl heptyl homolog (CBG-DMH), and tetrahydrocannabivarin (THCV) amongst juveniles and adults have been enhanced in recent years. Cannabinoids play a crucial role in the induction of respiratory, reproductive, immune and carcinogenic effects; however, potential data about mutagenic and developmental effects are still insufficient. The possible toxicity associated with the prolong use of cannabinoids acts as a tumor promoter in animal models and humans. Particular synthetic cannabinoids and analogues have low affinity for CB1 or CB2 receptors, while some synthetic members like Δ9-THC have high affinity towards these receptors. Cannabinoids and their derivatives have a direct or indirect association with acute and long-term toxicity. To reduce/attenuate cannabinoids toxicity, pharmaceutical biotechnology and cloning methods have opened a new window to develop cannabinoids encoding the gene tetrahydrocannabinolic acid (THCA) synthase. Plant revolution and regeneration hindered genetic engineering in C. Sativa. The genetic culture suspension of C. Sativa can be transmuted by the use of Agrobacterium tumefaciens to overcome its toxicity. The main aim of the present review was to collect evidence of the endo-cannabinoid system (ECS), cannabinoids toxicity, and the potential biotechnological approach of cannabinoids synthesis.

The endocannabinoid system in the human granulosa cell line KGN

Ovarian steroidogenesis is embedded in a sensitive network of regulatory mechanisms crucial for human fertility. The endocannabinoid system (ECS) represents an intrinsic modulating system involved in the regulation of endocrine functions. In the present study we characterized the ECS in the human granulosa cell line KGN and its impact on gonadotropin sensitivity and steroid hormone synthesis under basal and FSH-stimulated conditions. Expression studies were performed and estradiol was measured. CB1, CB2, DAGL, FAAH, GPR55, MAGL, NAPE-PLD and TRPV1 were expressed without FSH-dependent effects. Treatment with selective cannabinoid receptor agonists reduced basal but not FSH-stimulated estradiol and CYP19. Progesterone was not altered by ECS manipulation. CB1 agonist changed the expression of miRNAs associated with granulosa cell function, e.g. miR-23a, miR-24, miR-181a and miR-320a. Present data indicate a modulating role of the intrinsic ovarian ECS in the regulation of estradiol synthesis.

Ligands for cannabinoid receptors, promising anticancer agents

Cannabinoid compounds are unique to cannabis and provide some interesting biological properties. These compounds along with endocannabinoids, a group of neuromodulator compounds in the body especially in brain, express their effects by activation of G-protein-coupled cannabinoid receptors, CB1 and CB2. There are several physiological properties attributed to the endocannabinoids including pain relief, enhancement of appetite, blood pressure lowering during shock, embryonic development, and blocking of working memory. On the other hand, activation of endocannabinoid system may be suppresses evolution and progression of several types of cancer. According to the results of recent studies, CB receptors are over-expressed in cancer cell lines and application of multiple cannabinoid or cannabis-derived compounds reduce tumor size through decrease of cell proliferation or induction of cell cycle arrest and apoptosis along with desirable effect on decrease of tumor-evoked pain. Therefore, modulation of endocannabinoid system by inhibition of fatty acid amide hydrolase (FAAH), the enzyme, which metabolized endocannabinoids, or application of multiple cannabinoid or cannabis-derived compounds, may be appropriate for the treatment of several cancer subtypes. This review focuses on how cannabinoid affect different types of cancers.

Monoglyceride lipase deficiency modulates endocannabinoid signaling and improves plaque stability in ApoE-knockout mice

Background and aims

Monoglyceride lipase (MGL) catalyzes the final step of lipolysis by degrading monoglyceride (MG) to glycerol and fatty acid. MGL also hydrolyzes and thereby deactivates 2-arachidonoyl glycerol (2-AG), the most abundant endocannabinoid in the mammalian system. 2-AG acts as full agonist on cannabinoid receptor type 1 (CB1R) and CB2R, which are mainly expressed in brain and immune cells, respectively. Thus, we speculated that in the absence of MGL, increased 2-AG concentrations mediate CB2R signaling in immune cells to modulate inflammatory responses, thereby affecting the development of atherosclerosis.

Methods and results

We generated apolipoprotein E (ApoE)/MGL double-knockout (DKO) mice and challenged them with Western-type diet for 9 weeks. Despite systemically increased 2-AG concentrations in DKO mice, CB2R-mediated signaling remains fully functional, arguing against CB2R desensitization. We found increased plaque formation in both en face aortae (1.3-fold, p = 0.028) and aortic valve sections (1.5-fold, p = 0.0010) in DKO mice. Interestingly, DKO mice also presented reduced lipid (12%, p = 0.031) and macrophage content (18%, p = 0.061), elevated intraplaque smooth muscle staining (1.4-fold, p = 0.016) and thicker fibrous caps (1.8-fold, p = 0.0032), together with a higher ratio of collagen to necrotic core area (2.5-fold, p = 0.0003) and expanded collagen content (1.6-fold, p = 0.0007), which suggest formation of less vulnerable atherosclerotic plaques. Treatment with a CB2R inverse agonist prevents these effects in DKO mice, demonstrating that the observed plaque phenotype in DKO mice originates from CB2R activation.

Conclusion

Loss of MGL modulates endocannabinoid signaling in CB2R-expressing cells, which concomitantly affects the pathogenesis of atherosclerosis. We conclude that despite larger lesion size loss of MGL improves atherosclerotic plaque stability. Thus, pharmacological MGL inhibition may be a novel intervention to reduce plaque rupture.

Are cannabidiol and Δ(9) -tetrahydrocannabivarin negative modulators of the endocannabinoid system? A systematic review

Based upon evidence that the therapeutic properties of Cannabis preparations are not solely dependent upon the presence of Δ(9) -tetrahydrocannabinol (THC), pharmacological studies have been recently carried out with other plant cannabinoids (phytocannabinoids), particularly cannabidiol (CBD) and Δ(9) -tetrahydrocannabivarin (THCV). Results from some of these studies have fostered the view that CBD and THCV modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. Here, we review in vitro and ex vivo mechanistic studies of CBD and THCV, and synthesize data from these studies in a meta-analysis. Synthesized data regarding mechanisms are then used to interpret results from recent pre-clinical animal studies and clinical trials. The evidence indicates that CBD and THCV are not rimonabant-like in their action and thus appear very unlikely to produce unwanted CNS effects. They exhibit markedly disparate pharmacological profiles particularly at CB1 receptors: CBD is a very low-affinity CB1 ligand that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant. These cannabinoids illustrate how in vitro mechanistic studies do not always predict in vivo pharmacology and underlie the necessity of testing compounds in vivo before drawing any conclusion on their functional activity at a given target.

HU-446 and HU-465, Derivatives of the Non-psychoactive Cannabinoid Cannabidiol, Decrease the Activation of Encephalitogenic T Cells

Cannabidiol (CBD), the non-psychoactive cannabinoid, has been previously shown by us to decrease peripheral inflammation and neuroinflammation in mouse experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). Here we have studied the anti-inflammatory effects of newly synthesized derivatives of natural (-)-CBD ((-)-8,9-dihydro-7-hydroxy-CBD; HU-446) and of synthetic (+)-CBD ((+)-8,9-dihydro-7-hydroxy-CBD; HU-465) on activated myelin oligodendrocyte glycoprotein (MOG)35-55-specific mouse encephalitogenic T cells (T(MOG) ) driving EAE/MS-like pathologies. Binding assays followed by molecular modeling revealed that HU-446 has negligible affinity toward the cannabinoid CB1 and CB2 receptors while HU-465 binds to both CB1 and CB2 receptors at the high nanomolar concentrations (Ki = 76.7 ± 5.8 nm and 12.1 ± 2.3 nm, respectively). Both, HU-446 and HU-465, at 5 and 10 μm (but not at 0.1 and 1 μm), inhibited the MOG35-55-induced proliferation of autoreactive T(MOG) cells via CB1/CB2 receptor independent mechanisms. Moreover, both HU-446 and HU-465, at 5 and 10 μm, inhibited the release of IL-17, a key autoimmune cytokine, from MOG35-55-stimulated T(MOG) cells. These results suggest that HU-446 and HU-465 have anti-inflammatory potential in inflammatory and autoimmune diseases.

HU-444, a Novel, Potent Anti-Inflammatory, Nonpsychotropic Cannabinoid

Cannabidiol (CBD) is a component of cannabis, which does not cause the typical marijuana-type effects, but has a high potential for use in several therapeutic areas. In contrast to Δ(9)-tetrahydrocannabinol (Δ(9)-THC), it binds very weakly to the CB1 and CB2 cannabinoid receptors. It has potent activity in both in vitro and in vivo anti-inflammatory assays. Thus, it lowers the formation of tumor necrosis factor (TNF)-α, a proinflammatory cytokine, and was found to be an oral antiarthritic therapeutic in murine collagen-induced arthritis in vivo. However, in acidic media, it can cyclize to the psychoactive Δ(9)-THC. We report the synthesis of a novel CBD derivative, HU-444, which cannot be converted by acid cyclization into a Δ(9)-THC-like compound. In vitro HU-444 had anti-inflammatory activity (decrease of reactive oxygen intermediates and inhibition of TNF-α production by macrophages); in vivo it led to suppression of production of TNF-α and amelioration of liver damage as well as lowering of mouse collagen-induced arthritis. HU-444 did not cause Δ(9)-THC-like effects in mice. We believe that HU-444 represents a potential novel drug for rheumatoid arthritis and other inflammatory diseases.

Endocannabinoid metabolism by cytochrome P450 monooxygenases

The endogenous cannabinoid system was first uncovered following studies of the recreational drug Cannabis sativa. It is now recognized as a vital network of signaling pathways that regulate several physiological processes. Following the initial discovery of the cannabinoid receptors 1 (CB1) and 2 (CB2), activated by Cannabis-derived analogs, many endogenous fatty acids termed "endocannabinoids" are now known to be partial agonists of the CB receptors. At present, the most thoroughly studied endocannabinoid signaling molecules are anandamide (AEA) and 2-arachidonylglycerol (2-AG), which are both derived from arachidonic acid. Both AEA and 2-AG are also substrates for the eicosanoid-synthesizing pathways, namely, certain cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) enzymes. In the past, research in the endocannabinoid field focused on the interaction of AEA and 2-AG with the COX and LOX enzymes, but accumulating evidence also points to the involvement of CYPs in modulating endocannabinoid signaling. The focus of this review is to explore the current understanding of CYP-mediated metabolism of endocannabinoids.

Novel triaryl sulfonamide derivatives as selective cannabinoid receptor 2 inverse agonists and osteoclast inhibitors: discovery, optimization, and biological evaluation

Cannabinoid receptors have gained increasing attention as drug targets for developing potential therapeutic ligands. Here, we report the discovery and optimization of triaryl sulfonamides as a novel series possessing significant CB2 receptor affinity and selectivity. Four sets of triaryl ligands were designed and synthesized for further structural modifications and led to the identification of eight compounds as potent and selective CB2 inverse agonists with high binding affinity (CB2K(i) < 10 nM). Especially, compound 57 exhibited the strongest binding affinity on the CB2 receptor (CB2K(i) of 0.5 nM) and the best selectivity over the CB1 receptor (selectivity index of 2594). Importantly, 57 also showed potent inhibitory activity on osteoclast formation, and it was confirmed by a cell viability assay that the inhibition effects were not derived from the cytotoxicity. Finally, 3D QSAR studies confirmed our SAR findings that three bulky groups play an important role for CB2 receptor binding affinity.

Cannabinol and cannabidiol exert opposing effects on rat feeding patterns

RATIONALE

Increased food consumption following ∆(9)-tetrahydrocannabinol-induced cannabinoid type 1 receptor agonism is well documented. However, possible non-∆(9)-tetrahydrocannabinol phytocannabinoid-induced feeding effects have yet to be fully investigated. Therefore, we have assessed the effects of the individual phytocannabinoids, cannabigerol, cannabidiol and cannabinol, upon feeding behaviors.

METHODS

Adult male rats were treated (p.o.) with cannabigerol, cannabidiol, cannabinol or cannabinol plus the CB(1)R antagonist, SR141716A. Prior to treatment, rats were satiated and food intake recorded following drug administration. Data were analyzed for hourly intake and meal microstructure.

RESULTS

Cannabinol induced a CB(1)R-mediated increase in appetitive behaviors via significant reductions in the latency to feed and increases in consummatory behaviors via increases in meal 1 size and duration. Cannabinol also significantly increased the intake during hour 1 and total chow consumed during the test. Conversely, cannabidiol significantly reduced total chow consumption over the test period. Cannabigerol administration induced no changes to feeding behavior.

CONCLUSION

This is the first time cannabinol has been shown to increase feeding. Therefore, cannabinol could, in the future, provide an alternative to the currently used and psychotropic ∆(9)-tetrahydrocannabinol-based medicines since cannabinol is currently considered to be non-psychotropic. Furthermore, cannabidiol reduced food intake in line with some existing reports, supporting the need for further mechanistic and behavioral work examining possible anti-obesity effects of cannabidiol.

Effects of chronic bhang (cannabis) administration on the reproductive system of male mice

BACKGROUND

The purpose of this study was to investigate the effect of chronic uptake of bhang, prepared from the Cannabis sativa, on male reproductive physiology in adult male Parkes strain (P) mice. An attempt was also made to investigate the presence of cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptors, and fatty acid amide hydrolase (FAAH) in the testis and to evaluate any changes in it resulting from chronic intake of bhang in mice.

METHODS AND RESULTS

Adult male mice were given bhang (3 or 6 mg/kg body weight/day) orally for 36 consecutive days. Chronic intake of bhang caused regressive changes in the testes and suppressed sperm count, viability and motility. Bhang intake also caused significant decline in circulating testosterone level due to decline in testicular 3β HSD enzyme activity. An immunohistochemical study demonstrated the presence of CB1, CB2 and FAAH in the testis of mice. The present study also showed significant variation in the CB1 and CB2 receptors and FAAH protein levels in testes of mice exposed to bhang. These suppressive effects may be due to inhibitory effect of bhang on pituitary expression of gonadotrophin releasing hormone (GnRH) I receptor protein. Treatment of testes with bhang in vitro significantly decreased testicular luteinizing hormone receptor (LHR) and FAAH expression suggesting direct action of bhang on testicular activity.

CONCLUSIONS

The findings of this study thus suggest that bhang may impair fertility in male mice through alteration in the testicular endocannabinoid system and that chronic bhang exposure in humans would be predicted to alter male fertility.

CB2 cannabinoid receptor targets mitogenic Gi protein-cyclin D1 axis in osteoblasts

CB2 is a Gi protein-coupled receptor activated by endo- and phytocannabinoids, thus inhibiting stimulated adenylyl cyclase activity. CB2 is expressed in bone cells and Cb2 null mice show a marked age-related bone loss. CB2-specific agonists both attenuate and rescue ovariectomy-induced bone loss. Activation of CB2 stimulates osteoblast proliferation and bone marrow derived colony-forming units osteoblastic. Here we show that selective and nonselective CB2 agonists are mitogenic in MC3T3 E1 and newborn mouse calvarial osteoblastic cultures. The CB2 mitogenic signaling depends critically on the stimulation of Erk1/2 phosphorylation and de novo synthesis of MAP kinase-activated protein kinase 2 (Mapkapk2) mRNA and protein. Further downstream, CB2 activation enhances CREB transcriptional activity and cyclin D1 mRNA expression. The CB2-induced stimulation of CREB and cyclin D1 is inhibitable by pertussis toxin, the MEK-Erk1/2 inhibitors PD098059 and U0126, and Mapkapk2 siRNA. These data demonstrate that in osteoblasts CB2 targets a Gi protein-cyclin D1 mitogenic axis. Erk1/2 phosphorylation and Mapkapk2 protein synthesis are critical intermediates in this axis.

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.

Cannabinoid receptor type 1- and 2-mediated increase in cyclic AMP inhibits T cell receptor-triggered signaling

The aim of this study was to characterize inhibitory mechanisms on T cell receptor signaling mediated by the cannabinoid receptors CB1 and CB2. Both receptors are coupled to G(i/o) proteins, which are associated with inhibition of cyclic AMP formation. In human primary and Jurkat T lymphocytes, activation of CB1 by R(+)-methanandamide, CB2 by JWH015, and both by Delta9-tetrahydrocannabinol induced a short decrease in cyclic AMP lasting less than 1 h. However, this decrease was followed by a massive (up to 10-fold) and sustained (at least up to 48 h) increase in cyclic AMP. Mediated by the cyclic AMP-activated protein kinase A and C-terminal Src kinase, the cannabinoids induced a stable phosphorylation of the inhibitory Tyr-505 of the leukocyte-specific protein tyrosine kinase (Lck). By thus arresting Lck in its inhibited form, the cannabinoids prevented the dephosphorylation of Lck at Tyr-505 in response to T cell receptor activation, which is necessary for the subsequent initiation of T cell receptor signaling. In this way the cannabinoids inhibited the T cell receptor-triggered signaling, i.e. the activation of the zeta-chain-associated protein kinase of 70 kDa, the linker for activation of T cells, MAPK, the induction of interleukin-2, and T cell proliferation. All of the effects of the cannabinoids were blocked by the CB1 and CB2 antagonists AM281 and AM630. These findings help to better understand the immunosuppressive effects of cannabinoids and explain the beneficial effects of these drugs in the treatment of T cell-mediated autoimmune disorders like multiple sclerosis.

Cannabinoids and the immune system: an overview

Cannabinoids can influence the immune network. Data on the impact of exogenous cannabinoid ligands on immune function serve not only to understand how the endocannabinoid system modulates immune phenomena associated with infection or inflammation, but also to identify therapeutic targets for immune diseases. Cannabinoids can modulate immune reactions in the periphery but also in the brain, influence T cell subset balance and cytokine expression and play a role in the balance between neuroinflammation and neurodegeneration. Immune cells can synthesize endocannabinoids and also be influenced by cannabinoid analogues. Cannabinoid receptors show different expression on immune cells depending on activation status and stimuli. The complexity of relation between cannabinoid ligands of various classes and cannabinoid receptors brought the need to refine the simple conceptual frame of agonist-antagonists and offered potential implications for understanding interactions in pathological conditions. The immune influence of cannabinoid ligands is not fully elucidated. However, aspects of their immunomodulatory effects provide the basis for a context-dependent targeted therapeutic approach, thus leading to the possibility for the use of cannabinoids in the treatment of inflammatory disease.

Testicular toxicity in cannabis extract treated mice: association with oxidative stress and role of antioxidant enzyme systems

Intraperitoneal injection of cannabis extract at low doses (total doses ranging from 40 mg to 60 mg per mouse) induced adverse effect on testes and oxidative stress. At low doses, there was a significant increase in lipid peroxidation and decrease in testicular lipid content, but the effects were significantly less at higher doses and at the withdrawal of cannabis treatment (recovery dose). There was a marked decrease in antioxidant enzyme profiles (superoxide dismutase, catalase and glutathione peroxidase) and glutathione content at low doses, but these effects were higher at higher dose and at withdrawal of the treatment (recovery effect). Histology revealed significant shrinkage of tubular diameter and detrimental changes in seminiferous epithelium of testis with resulting lowered serum testosterone and pituitary gonadotropins (follicular stimulating [FSH] and luteinizing hormones [LH]) levels at low doses. But at higher doses and particularly at withdrawal of the treatment, regression of various germ cell layers of testes through the revival of testosterone hormone and pituitary gonadotropins (FSH and LH) were observed, indicating that recovery effects on testes became operative possibly through the corrective measure of endogenous testicular antioxidant enzymes profiles and pituitary gonadotropins hormones feedback mechanisms.

Cannabinoids Delta(9)-tetrahydrocannabinol and cannabidiol differentially inhibit the lipopolysaccharide-activated NF-kappaB and interferon-beta/STAT proinflammatory pathways in BV-2 microglial cells

Cannabinoids have been shown to exert anti-inflammatory activities in various in vivo and in vitro experimental models as well as ameliorate various inflammatory degenerative diseases. However, the mechanisms of these effects are not completely understood. Using the BV-2 mouse microglial cell line and lipopolysaccharide (LPS) to induce an inflammatory response, we studied the signaling pathways engaged in the anti-inflammatory effects of cannabinoids as well as their influence on the expression of several genes known to be involved in inflammation. We found that the two major cannabinoids present in marijuana, Delta(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD), decrease the production and release of proinflammatory cytokines, including interleukin-1beta, interleukin-6, and interferon (IFN)beta, from LPS-activated microglial cells. The cannabinoid anti-inflammatory action does not seem to involve the CB1 and CB2 cannabinoid receptors or the abn-CBD-sensitive receptors. In addition, we found that THC and CBD act through different, although partially overlapping, mechanisms. CBD, but not THC, reduces the activity of the NF-kappaB pathway, a primary pathway regulating the expression of proinflammatory genes. Moreover, CBD, but not THC, up-regulates the activation of the STAT3 transcription factor, an element of homeostatic mechanism(s) inducing anti-inflammatory events. Following CBD treatment, but less so with THC, we observed a decreased level of mRNA for the Socs3 gene, a main negative regulator of STATs and particularly of STAT3. However, both CBD and THC decreased the activation of the LPS-induced STAT1 transcription factor, a key player in IFNbeta-dependent proinflammatory processes. In summary, our observations show that CBD and THC vary in their effects on the anti-inflammatory pathways, including the NF-kappaB and IFNbeta-dependent pathways.

The therapeutic potential of novel cannabinoid receptors

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

Physiological roles of 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand

2-Arachidonoylglycerol is an arachidonic acid-containing monoacylglycerol isolated from the rat brain and canine gut as an endogenous ligand for the cannabinoid receptors (CB1 and CB2). 2-Arachidonoylglycerol binds to both the CB1 receptor, abundantly expressed in the nervous system, and the CB2 receptor, mainly expressed in the immune system, with high affinity, and exhibits a variety of cannabimimetic activities. Notably, anandamide, another endogenous ligand for the cannabinoid receptors, acts as a partial agonist at these cannabinoid receptors, whereas 2-arachidonoylglycerol acts as a full agonist. The results of structure-activity relationship experiments strongly suggested that 2-arachidonoylglycerol rather than anandamide is the true natural ligand for both the CB1 and the CB2 receptors. Evidence is gradually accumulating which shows that 2-arachidonoylglycerol plays physiologically and pathophysiologically essential roles in various mammalian tissues and cells.

Leptin receptor deficiency is associated with upregulation of cannabinoid 1 receptors in limbic brain regions

Leptin receptor dysfunction results in overeating and obesity. Leptin regulates hypothalamic signaling that underlies the motivation to hyperphagia, but the interaction between leptin and cannabinoid signaling is poorly understood. We evaluated the role of cannabinoid 1 receptors (CB(1)R) in overeating and the effects of food deprivation on CB(1)R in the brain. One-month-old Zucker rats were divided into unrestricted and restricted (fed 70% of unrestricted rats) diet groups and maintained until adulthood (4 months). Levels of relative binding sites of CB(1)R (CB(1)R binding levels) were assessed using [(3)H] SR141716A in vitro autoradiography. These levels were higher (except cerebellum and hypothalamus) at 4 months than at 1 month of age. One month CB(1)R binding levels for most brain regions did not differ between Ob and Lean (Le) rats (except in frontal and cingulate cortices in Le and in the hypothalamus in Ob). Four month Ob rats had higher CB(1)R binding levels than Le in most brain regions and food restriction was associated with higher CB(1)R levels in all brain regions in Ob, but not in Le rats. CB(1)R binding levels increased between adolescence and young adulthood which we believe was influenced by leptin and food availability. The high levels of CB(1)R in Ob rats suggest that leptin's inhibition of food-intake is in part mediated by downregulation of CB(1)R and that leptin interferes with CB(1)R upregulation under food-deprivation conditions. These results are consistent with prior findings showing increased levels of endogenous cannabinoids in the Ob rats corroborating the regulation of cannabinoid signaling by leptin.

CB2 receptor-mediated migration of immune cells: it can go either way

Though many studies have examined the role of CB2 receptors in immune cell migration, it has been difficult to form definitive conclusions about the physiopathological role of these receptors in regulating immune responses and how this might be pharmacologically targeted for therapy. Do cannabinoids promote inflammation through the recruitment of immune cells, or reduce inflammation by interfering with the action of other chemoattractants? Is therapeutic intervention with an agonist or antagonist more appropriate for the reduction of inflammation? In this review, we will summarize the progress that has been made in answering these questions and outline current hypotheses.

The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin

Cannabis sativa is the source of a unique set of compounds known collectively as plant cannabinoids or phytocannabinoids. This review focuses on the manner with which three of these compounds, (-)-trans-delta9-tetrahydrocannabinol (delta9-THC), (-)-cannabidiol (CBD) and (-)-trans-delta9-tetrahydrocannabivarin (delta9-THCV), interact with cannabinoid CB1 and CB2 receptors. Delta9-THC, the main psychotropic constituent of cannabis, is a CB1 and CB2 receptor partial agonist and in line with classical pharmacology, the responses it elicits appear to be strongly influenced both by the expression level and signalling efficiency of cannabinoid receptors and by ongoing endogenous cannabinoid release. CBD displays unexpectedly high potency as an antagonist of CB1/CB2 receptor agonists in CB1- and CB2-expressing cells or tissues, the manner with which it interacts with CB2 receptors providing a possible explanation for its ability to inhibit evoked immune cell migration. Delta9-THCV behaves as a potent CB2 receptor partial agonist in vitro. In contrast, it antagonizes cannabinoid receptor agonists in CB1-expressing tissues. This it does with relatively high potency and in a manner that is both tissue and ligand dependent. Delta9-THCV also interacts with CB1 receptors when administered in vivo, behaving either as a CB1 antagonist or, at higher doses, as a CB1 receptor agonist. Brief mention is also made in this review, first of the production by delta9-THC of pharmacodynamic tolerance, second of current knowledge about the extent to which delta9-THC, CBD and delta9-THCV interact with pharmacological targets other than CB1 or CB2 receptors, and third of actual and potential therapeutic applications for each of these cannabinoids.

Medicinal Chemistry Endeavors around the Phytocannabinoids

Over the past 50 years, a considerable research in medicinal chemistry has been carried out around the natural constituents of Cannabis sativa L. Following the identification of Delta9-tetrahydrocannabinol (Delta9-THC) in 1964, critical chemical modifications, e.g., variation of the side chain at C3 and the opening of the tricyclic scaffold, have led to the characterization of potent and cannabinoid receptor subtype-selective ligands. Those ligands that demonstrate high affinity for the cannabinoid receptors and good biological efficacy are still used as powerful pharmacological tools. This review summarizes past as well as recent developments in the structure-activity relationships of phytocannabinoids.