Cannabinoid Receptors and Their Relationship With Chronic Pain: A Narrative Review

CB1-versus-CB2-receptors “The burden of chronic pain has affected many individuals leading to distress and discomfort, alongside numerous side effects with conventional therapeutic approaches.

Cannabinoid receptors are naturally found in the human body and have long been an interest in antinociception. These include CB1 and CB2 receptors, which are promising candidates for the treatment of chronic inflammatory pain.

The mechanism of action of the receptors and how they approach pain control in inflammatory conditions show that it can be an adjunctive approach towards controlling these symptoms. Numerous studies have shown how the targeted approach towards these receptors has activated them promoting a release in cytokines, all leading to anti-inflammatory effects and immune system regulation.

Cannabinoid activation of glycine and gamma-aminobutyric acid (GABA) models also showed efficacy in pain management. Chronic conditions such as osteoarthritis were shown to also benefit from this considerable treatment. However, it is unclear how the cannabinoid system works in relation with the pain pathway. Therefore, in this review we aim to analyse the role of the cannabinoid system in chronic inflammatory pain.”

https://pubmed.ncbi.nlm.nih.gov/33072446/

https://www.cureus.com/articles/39887-cannabinoid-receptors-and-their-relationship-with-chronic-pain-a-narrative-review

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Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

ijms-logo “The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task.

An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases.

This review focuses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.”

https://pubmed.ncbi.nlm.nih.gov/33080916/

https://www.mdpi.com/1422-0067/21/20/7693

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The immunosuppressive effect of the endocannabinoid system on the inflammatory phenotypes of macrophages and mesenchymal stromal cells: a comparative study

SpringerLink “The inflammatory sequence is the first phase of wound healing. Macrophages (MPhs) and mesenchymal stromal cells (MSCs) respond to an inflammatory microenvironment by adapting their functional activity, which polarizes them into the pro-inflammatory phenotypes M1 and MSC1. Prolongation of the inflammatory phase results in the formation of chronic wounds. The endocannabinoid system (ECS) possesses immunomodulatory properties that may impede this cellular phenotypic switch.

Methods: We investigated the immunosuppressive influence of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) on the M1 and MSC1 cytokine secretion. Lipopolysaccharides (LPS) were used as inflammagen to stimulate MPhs and MSCs. Both inflammatory phenotypes were co-exposed to AEA or 2-AG, the specific cannabinoid receptor CB2 agonist JWH-133 served as reference. The inflammatory responses were detected by CD80/163 immuno-labelling and by ELISA measures of secreted IL-6, IL-8, MIF, TNF-α, TGF-β, and VEGF.

Results: M1 cells were found positive for CD80 expression and secreted less IL-6 and IL-8 than MSC1 cells, while both cell types produced similar amounts of MIF. TNF-α release was increased by M1, and growth factors were secreted by MSC1, only. Cannabinoid receptor ligands efficiently decreased the inflammatory response of M1, while their impact was less pronounced in MSC1.

Conclusions: The ECS down-regulated the inflammatory responses of MPhs and MSCs by decreasing the cytokine release upon LPS treatment, while CB2 appeared to be of particular importance. Hence, stimulating the ECS by manipulation of endo- or use of exogenous cannabinoids in vivo may constitute a potent therapeutic option against inflammatory disorders.”

https://pubmed.ncbi.nlm.nih.gov/33026642/

https://link.springer.com/article/10.1007%2Fs43440-020-00166-3

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Signaling Through the Type 2 Cannabinoid Receptor Regulates the Severity of Acute and Chronic Graft versus Host Disease

Blood“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 CB2R-EGFP 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, 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 contribute to disease biology. In vitro, both THC and JWH-133 induced arrestin recruitment and ERK phosphorylation via CB2R, but THC had no effect on CB2R-mediated inhibition of adenylyl cyclase.

These studies demonstrate that the CB2R plays a critical role in the regulation of GVHD and suggest that effective therapeutic targeting is dependent upon agonist signaling characteristics and receptor selectivity in conjunction with the composition of pathogenic immune effector cells.”

https://pubmed.ncbi.nlm.nih.gov/33027805/

https://ashpublications.org/blood/article-abstract/doi/10.1182/blood.2020004871/464166/Signaling-Through-the-Type-2-Cannabinoid-Receptor?redirectedFrom=fulltext

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The impact of cannabinoid type 2 receptors (CB2Rs) in neuroprotection against neurological disorders

 Acta Pharmacologica Sinica“Cannabinoids have long been used for their psychotropic and possible medical properties of symptom relief. In the past few years, a vast literature shows that cannabinoids are neuroprotective under different pathological situations.

Most of the effects of cannabinoids are mediated by the well-characterized cannabinoid receptors, the cannabinoid type 1 receptor (CB1R) and cannabinoid type 2 receptor (CB2R). Even though CB1Rs are highly expressed in the central nervous system (CNS), the adverse central side effects and the development of tolerance resulting from CB1R activation may ultimately limit the clinical utility of CB1R agonists. In contrast to the ubiquitous presence of CB1Rs, CB2Rs are less commonly expressed in the healthy CNS but highly upregulated in glial cells under neuropathological conditions.

Experimental studies have provided robust evidence that CB2Rs seem to be involved in the modulation of different neurological disorders. In this paper, we summarize the current knowledge regarding the protective effects of CB2R activation against the development of neurological diseases and provide a perspective on the future of this field. A better understanding of the fundamental pharmacology of CB2R activation is essential for the development of clinical applications and the design of novel therapeutic strategies.”

https://pubmed.ncbi.nlm.nih.gov/33024239/

https://www.nature.com/articles/s41401-020-00530-2

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The CB2 Agonist β-Caryophyllene in Male and Female Rats Exposed to a Model of Persistent Inflammatory Pain

frontiers – Page 2 – Retraction Watch “Cannabinoids help in pain treatment through their action on CB1 and CB2 receptors.

β-caryophyllene (BCP), an ancient remedy to treat pain, is a sesquiterpene found in large amounts in the essential oils of various spice and food plants such as oregano, cinnamon, and black pepper. It binds to the CB2 receptor, acting as a full agonist.

Sex differences in the BCP-induced analgesic effect were studied by exposing male and female rats to a persistent/repeated painful stimulation.

In conclusion, long-term intake of BCP appears to be able to decrease pain behaviors in a model of repeated inflammatory pain in both sexes, but to a greater degree in males.”

https://pubmed.ncbi.nlm.nih.gov/33013287/

https://www.frontiersin.org/articles/10.3389/fnins.2020.00850/full

“β-caryophyllene (BCP) is a common constitute of the essential oils of numerous spice, food plants and major component in Cannabis.”   http://www.ncbi.nlm.nih.gov/pubmed/23138934

“Beta-caryophyllene is a dietary cannabinoid.”   https://www.ncbi.nlm.nih.gov/pubmed/18574142

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Endocannabinoids Inhibit the Induction of Virulence in Enteric Pathogens

Cell | Publons
“Endocannabinoids are host-derived lipid hormones that fundamentally impact gastrointestinal (GI) biology. The use of cannabis and other exocannabinoids as anecdotal treatments for various GI disorders inspired the search for mechanisms by which these compounds mediate their effects, which led to the discovery of the mammalian endocannabinoid system. Dysregulated endocannabinoid signaling was linked to inflammation and the gut microbiota. However, the effects of endocannabinoids on host susceptibility to infection has not been explored. Here, we show that mice with elevated levels of the endocannabinoid 2-arachidonoyl glycerol (2-AG) are protected from enteric infection by Enterobacteriaceae pathogens. 2-AG directly modulates pathogen function by inhibiting virulence programs essential for successful infection. Furthermore, 2-AG antagonizes the bacterial receptor QseC, a histidine kinase encoded within the core Enterobacteriaceae genome that promotes the activation of pathogen-associated type three secretion systems. Taken together, our findings establish that endocannabinoids are directly sensed by bacteria and can modulate bacterial function.”
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“Fighting intestinal infections with the body’s own endocannabinoids. By harnessing the power of natural compounds produced in the body and in plants, we may eventually treat infections in a whole new way.”  https://www.sciencedaily.com/releases/2020/10/201007123119.htm

“Study may explain why cannabis plant can reduce symptoms of various bowel conditions” https://www.news-medical.net/news/20201007/Study-could-help-explain-why-cannabis-plant-can-reduce-symptoms-of-various-bowel-conditions.aspx

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An Agathokakological tale of ∆9 -THC: Exploration of Possible Biological Targets

“∆ 9 -Tetrahydrocannabinol (∆9 -THC), the active phytocannabinoid in cannabis, is virtually an adjunct to the endogenous endocannabinoid signaling system.

By interacting with G-protein-coupled receptors CB1 and CB2, ∆9 -THC affects peripheral and central circulation by lowering sympathetic activity, altering gene expression, cell proliferation, and differentiation, decreasing leukocyte migration, modulating neurotransmitter release thereby modulating cardiovascular functioning, tumorigenesis, immune responses, behavioral and locomotory activities respectively.

∆ 9 -THC is effective in suppressing chemotherapy-induced vomiting, retards malignant tumor growth, inhibits metastasis, and promotes apoptosis. Other mechanisms involved are targeting cell cycle at the G2-M phase in human breast cancer, downregulation of E2F transcription factor 1 (E2F1) in human glioblastoma multiforme, and stimulation of ER stress-induced autophagy.

∆ 9 -THC also plays a role in ameliorating neuroinflammation, excitotoxicity, neuroplasticity, trauma, and stroke and is associated with reliving childhood epilepsy, brain trauma, and neurodegenerative diseases.

∆9 -THC via CB1 receptors affects nociception, emotion, memory, and reduces neuronal excitability and excitotoxicity in epilepsy. It also increases renal blood flow, reduces intraocular pressure via a sympathetic pathway, and modulates hormonal release, thereby decreasing the reproductive function and increasing glucose metabolism.

Versatile medical marijuana has stimulated abundant research demonstrating substantial therapeutic promise, suggesting the possibilities of first-in-class drugs in diverse therapeutic segments. In this review, we represent the current pharmacological status of the phytocannabinoid, ∆ 9 -THC, and synthetic analogs in cancer, cardiovascular, and neurodegenerative disorders.”

https://pubmed.ncbi.nlm.nih.gov/33001012/

https://www.eurekaselect.com/186455/article

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A Cannabinoid Type 2 (CB2) Receptor Agonist Augments NOS-Dependent Responses of Cerebral Arterioles during Type 1 Diabetes

Microvascular Research “While activation of cannabinoid (CB2) receptors has been shown to be neuroprotective, no studies have examined whether this neuroprotection is directed at cerebral arterioles and no studies have examined whether activation of CB2 receptors can rescue cerebrovascular dysfunction during a chronic disease state such as type 1 diabetes (T1D).

Our goal was to test the hypothesis that administration of a CB2 agonist (JWH-133) would improve impaired endothelial (eNOS)- and neuronal (nNOS)- dependent dilation of cerebral arterioles during T1D.

In vivo diameter of cerebral arterioles in nondiabetic and T1D rats was measured in response to an eNOS-dependent agonist (adenosine 5′-diphosphate; ADP), an nNOS-dependent agonist (N-methyl-D-aspartate; NMDA), and an NOS-independent agonist (nitroglycerin) before and 1 hour following JWH-133 (1 mg/kg IP). Dilation of cerebral arterioles to ADP and NMDA was greater in nondiabetic than in T1D rats.

Treatment with JWH-133 increased responses of cerebral arterioles to ADP and NMDA in both nondiabetic and T1D rats. Responses of cerebral arterioles to nitroglycerin were similar between nondiabetic and T1D rats, and JWH-133 did not influence responses to nitroglycerin in either group. The restoration in responses to the agonists by JWH-133 could be inhibited by treatment with a specific inhibitor of CB2 receptors (AM-630; 3 mg/kg IP).

Thus, activation of CB2 receptors can potentiate reactivity of cerebral arterioles during physiologic and pathophysiologic states. We speculate that treatment with CB2 receptor agonists may have potential therapeutic benefits for the treatment of cerebral vascular diseases via a mechanism that can increase cerebral blood flow.”

https://pubmed.ncbi.nlm.nih.gov/32979391/

“Activation of CB2 receptors improves cerebral vascular function. Activation of CB2 receptors improves responses in type 1 diabetes. We speculate that treatment with CB2 receptor agonists may have potential therapeutic benefits for the treatment of cerebral vascular disease that can contribute to the pathogenesis of stroke.”

https://www.sciencedirect.com/science/article/pii/S0026286220301370?via%3Dihub

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Cannabidiol and Oxygen-Ozone Combination Induce Cytotoxicity in Human Pancreatic Ductal Adenocarcinoma Cell Lines

cancers-logo“Pancreatic cancer (PC) is related to lifestyle risks, chronic inflammation, and germline mutations in BRCA1/2ATMMLH1TP53, or CDKN2A. Surgical resection and adjuvant chemotherapy are the main therapeutic strategies but are less effective in patients with high-grade tumors.

Oxygen-ozone (O2/O3) therapy is an emerging alternative tool for the treatment of several clinical disorders. O2/O3 therapy has been found to ameliorate mechanisms promoting chronic pain and inflammation, including hypoxia, inflammatory mediators, and infection.

The advantages of using cannabinoids have been evaluated in vitro and in vivo models of several human cancers. Regarding PDAC, activation of cannabinoid receptors was found to induce pancreatic cancer cell apoptosis without affecting the normal pancreas cells.

In a murine model of PDAC, a combination of cannabidiol (CBD) and gemcitabine increased survival length by nearly three times. Herein, we evaluate the anticancer effect of CBD and O2/O3, alone or in combination, on two human PDAC cell lines, PANC-1 and MiaPaCa-2, examining expression profiles of 92 pancreatic adenocarcinoma associated genes, cytotoxicity, migration properties, and cell death. Finally, we assess the combination effects with gemcitabine and paclitaxel.

Summarizing, for the first time the antitumoral effect of combined therapy with CBD and oxygen-ozone therapy in PDAC is evidenced.”

https://pubmed.ncbi.nlm.nih.gov/32992648/

https://www.mdpi.com/2072-6694/12/10/2774

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