Discovery of Selective Cannabinoid CB2 Receptor Agonists by High-Throughput Screening

The effect of cannabinoids on wound healing: A review

Background and Aims

Cannabis and its various derivatives are commonly used for both recreational and medicinal purposes. Cannabinoids have been shown to have anti-inflammatory properties. Inflammation is an important component of wound healing and the effect of cannabinoids on wound healing has become a recent topic of investigation. The objective of this article is to perform a comprehensive review of the literature to summarize the effects of cannabinoids on wound healing of the skin and to guide future avenues of research.

Methods

A comprehensive literature review was performed to evaluate the effects of cannabinoids on cutaneous wound healing.

Results

Cannabinoids appear to improve skin wound healing through a variety of mechanisms. This is supported through a variety of in vitro and animal studies. Animal studies suggest application of cannabinoids may improve the healing of postsurgical and chronic wounds. There are few human studies which evaluate the effects of cannabinoids on wound healing and many of these are case series and observational studies. They do suggest cannabinoids may have some benefit. However, definitive conclusions cannot be drawn from them.

Conclusion

While further human studies are needed, topical application of cannabinoids may be a potential therapeutic option for postsurgical and chronic wounds.

History of Cannabis Regulation and Medicinal Therapeutics: It's Complicated

The genus Cannabis has a complex history, with great variations in the genus itself, as well as in its current uses worldwide. Today, it is the most commonly used psychoactive substance, with 209 million users in 2020. The legalization of cannabis for medicinal or adult use is complex. From its origins as a therapeutic agent in 2800 bc China, to the current knowledge on cannabinoids and the cannabinoid system, to the complex status of cannabis regulation across continents-knowledge gained from the history of cannabis use can inform research on cannabis-based treatments for patients with medical conditions that remain challenging in 21st century medicine, warranting research and evidence-based policy options. Changes in cannabis-related policymaking, scientific advances, and perceptions may result in increasing patient inquiries about its medicinal usage, regardless of personal opinions, thus meriting education and training of clinicians. This commentary outlines the long history of cannabis use, its current therapeutic potential from a regulatory research perspective, and the continued challenges in research and regulation in the ever-changing era of modern cannabis use. It is crucial to understand the history and complexity of cannabis use as medicine to better understand its potential for clinical therapeutics and the effects of modern-day legalization on other health- and society-related issues.

N-[1,3-Dialkyl(aryl)-2-oxoimidazolidin-4-ylidene]-aryl(alkyl)sulphonamides as Novel Selective Human Cannabinoid Type 2 Receptor (hCB2R) Ligands; Insights into the Mechanism of Receptor Activation/Deactivation

Cannabinoid type 1 (hCB1) and type 2 (hCB2) receptors are pleiotropic and crucial targets whose signaling contributes to physiological homeostasis and its restoration after injury. Being predominantly expressed in peripheral tissues, hCB2R represents a safer therapeutic target than hCB1R, which is highly expressed in the brain, where it regulates processes related to cognition, memory, and motor control. The development of hCB2R ligands represents a therapeutic opportunity for treating diseases such as pain, inflammation and cancer. Identifying new selective scaffolds for cannabinoids and determining the structural determinants responsible for agonism and antagonism are priorities in drug design. In this work, a series of N-[1,3-dialkyl(aryl)-2-oxoimidazolidin-4-ylidene]-aryl(alkyl)sulfonamides is designed and synthesized and their affinity for human hCB1R and hCB2R is determined. Starting with a scaffold selected from the NIH Psychoactive Drug Screening Program Repository, through a combination of molecular modeling and structure-activity relationship studies, we were able to identify the chemical features leading to finely tuned hCB2R selectivity. In addition, an in silico model capable of predicting the functional activity of hCB2R ligands was proposed and validated. The proposed receptor activation/deactivation model enabled the identification of four pure hCB2R-selective agonists that can be used as a starting point for the development of more potent ligands.

Characterization of Subtype Selective Cannabinoid CB2 Receptor Agonists as Potential Anti-Inflammatory Agents

Activation of the CB₂ receptor has been shown to have anti-inflammatory and antinociceptive effects without causing psychoactive effects. Previously, we reported that the compound ethyl 2(2-(N-(2,3-dimethylphenyl) phenylsulfonamido)acetamido)benzoate (ABK5) is a CB₂ subtype selective agonist with anti-inflammatory and antinociceptive effects. In the present study, we tested four ABK5 derivatives, ABK5-1, ABK5-2, ABK5-5, and ABK5-6, to analyze the structure of ABK5 to obtain CB₂-selective agonists with higher affinity and efficacy. Affinity, subtype selectivity, and G-protein coupling were determined by radioligand binding assays. Selected compounds were then subjected to evaluation of anti-inflammatory effects using two different cell lines, Jurkat (ABK5-1 and 5-2) and BV-2 cells (ABK5-1), which are models of T cells and microglia, respectively. ABK5-1, ABK5-2, and ABK5-6 had comparable CB₂ binding affinity with ABK5 (and stimulated G-protein coupling), while only ABK5-1 and ABK5-2 maintained CB₂-subtype selectivity. ABK5-5 did not bind CB₂ in the detectable range. RT-PCR and ELISA analysis showed that the two compounds also inhibit IL-2 and TNF-α production, and they were more efficacious than ABK5 in inhibiting TNF-α production. CXCL-12 mediated chemotaxis was also evaluated by the transwell migration assay, and both ABK5-1 and ABK5-2 inhibited chemotaxis with a stronger effect observed in ABK5-1. In the microglia cell line BV-2, ABK5-1 inhibited IL-1β and IL-6 production, which suggests this compound has anti-inflammatory effects through targeting multiple immune cells, and may be a candidate for treatment of inflammation.

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

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

Identification and biochemical analyses of selective CB2 agonists

Cannabinoid CB₁ and CB₂ receptors are activated by Δ⁹-tetrahydrocannabinol, a psychoactive component of marijuana. The cannabinoid CB₁ receptor is primarily located in the brain and is responsible for the psychoactive side effects, whereas the cannabinoid CB₂ receptor is located in immune cells and is an attractive target for immune-related maladies. We identify small molecules that selectively bind to the cannabinoid CB₂ receptor and can be further developed into therapeutics. The affinity of three molecules, ABK5, ABK6, and ABK7, to the cannabinoid CB₂ receptor was determined with radioligand competition binding. The potency of G-protein coupling was determined with GTPγS binding. The three compounds bound selectively to the cannabinoid CB₂ receptor_, and no binding to the cannabinoid CB₁ receptor was detected up to 10 μM. Immunoblotting studies show that the amount of ERK1/2 and MEK phosphorylation increased in a G_i/o-dependent manner. Furthermore, an immune cell line (Jurkat cells) was treated with ABK5, and as a result, inhibited cell proliferation. These three compounds are novel cannabinoid CB₂ receptor agonists and hold promise to be further developed to treat inflammation and the often-associated pain.

Emerging strategies targeting CB2 cannabinoid receptor: Biased agonism and allosterism

During these last years, the CB₂ cannabinoid receptor has emerged as a potential anti-inflammatory target in diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Huntington's disease, ischemic stroke, autoimmune diseases, osteoporosis, and cancer. However, the development of clinically useful CB₂ agonists reveals to be very challenging. Allosterism and biased-signaling mechanisms at CB₂ receptor may offer new avenues for the development of improved CB₂ receptor-targeted therapies. Although there has been some exploration of CB₁ receptor activation by new CB₁ allosteric or biased-signaling ligands, the CB₂ receptor is still at initial stages in this domain. In an effort to understand the molecular basis behind these pharmacological approaches, we have analyzed and summarized the structural data reported so far at CB₂ receptor.