Cannabis Pharmacology: The Usual Suspects and a Few Promising Leads.

Advances in Pharmacology

“The golden age of cannabis pharmacology began in the 1960s as Raphael Mechoulam and his colleagues in Israel isolated and synthesized cannabidiol, tetrahydrocannabinol, and other phytocannabinoids. Initially, THC garnered most research interest with sporadic attention to cannabidiol, which has only rekindled in the last 15 years through a demonstration of its remarkably versatile pharmacology and synergy with THC. Gradually a cognizance of the potential of other phytocannabinoids has developed. Contemporaneous assessment of cannabis pharmacology must be even far more inclusive. Medical and recreational consumers alike have long believed in unique attributes of certain cannabis chemovars despite their similarity in cannabinoid profiles. This has focused additional research on the pharmacological contributions of mono- and sesquiterpenoids to the effects of cannabis flower preparations. Investigation reveals these aromatic compounds to contribute modulatory and therapeutic roles in the cannabis entourage far beyond expectations considering their modest concentrations in the plant. Synergistic relationships of the terpenoids to cannabinoids will be highlighted and include many complementary roles to boost therapeutic efficacy in treatment of pain, psychiatric disorders, cancer, and numerous other areas. Additional parts of the cannabis plant provide a wide and distinct variety of other compounds of pharmacological interest, including the triterpenoid friedelin from the roots, canniprene from the fan leaves, cannabisin from seed coats, and cannflavin A from seed sprouts. This chapter will explore the unique attributes of these agents and demonstrate how cannabis may yet fulfil its potential as Mechoulam’s professed “pharmacological treasure trove.””

Cannabinoids and Pain: Sites and Mechanisms of Action.

Advances in Pharmacology

“The endocannabinoid system, consisting of the cannabinoid1 receptor (CB1R) and cannabinoid2 receptor (CB2R), endogenous cannabinoid ligands (endocannabinoids), and metabolizing enzymes, is present throughout the pain pathways. Endocannabinoids, phytocannabinoids, and synthetic cannabinoid receptor agonists have antinociceptive effects in animal models of acute, inflammatory, and neuropathic pain. CB1R and CB2R located at peripheral, spinal, or supraspinal sites are important targets mediating these antinociceptive effects. The mechanisms underlying the analgesic effects of cannabinoids likely include inhibition of presynaptic neurotransmitter and neuropeptide release, modulation of postsynaptic neuronal excitability, activation of the descending inhibitory pain pathway, and reductions in neuroinflammatory signaling. Strategies to dissociate the psychoactive effects of cannabinoids from their analgesic effects have focused on peripherally restricted CB1R agonists, CB2R agonists, inhibitors of endocannabinoid catabolism or uptake, and modulation of other non-CB1R/non-CB2R targets of cannabinoids including TRPV1, GPR55, and PPARs. The large body of preclinical evidence in support of cannabinoids as potential analgesic agents is supported by clinical studies demonstrating their efficacy across a variety of pain disorders.”

Cannabinoids in the Cardiovascular System.

Advances in Pharmacology

“Cannabinoids are known to modulate cardiovascular functions including heart rate, vascular tone, and blood pressure in humans and animal models. Essential components of the endocannabinoid system, namely, the production, degradation, and signaling pathways of endocannabinoids have been described not only in the central and peripheral nervous system but also in myocardium, vasculature, platelets, and immune cells.

The mechanisms of cardiovascular responses to endocannabinoids are often complex and may involve cannabinoid CB1 and CB2 receptors or non-CB1/2 receptor targets.

Preclinical and some clinical studies have suggested that targeting the endocannabinoid system can improve cardiovascular functions in a number of pathophysiological conditions, including hypertension, metabolic syndrome, sepsis, and atherosclerosis.

In this chapter, we summarize the local and systemic cardiovascular effects of cannabinoids and highlight our current knowledge regarding the therapeutic potential of endocannabinoid signaling and modulation.”

Is the Cannabinoid CB2 Receptor a Major Regulator of the Neuroinflammatory Axis of the Neurovascular Unit in Humans?


“The central nervous system (CNS) is an immune privileged site where the neurovascular unit (NVU) and the blood-brain barrier (BBB) act as a selectively permeable interface to control the passage of nutrients and inflammatory cells into the brain parenchyma. However, in response to injury, infection, or disease, CNS cells become activated, and release inflammatory mediators to recruit immune cells to the site of inflammation.

Increasing evidence suggests that cannabinoids may have a neuroprotective role in CNS inflammatory conditions.

For many years, it was widely accepted that cannabinoid receptor type 1 (CB1) modulates neurological function centrally, while peripheral cannabinoid receptor type 2 (CB2) modulates immune function.

As knowledge about the physiology and pharmacology of the endocannabinoid system advances, there is increasing interest in targeting CB2 as a potential treatment for inflammation-dependent CNS diseases (Ashton & Glass, 2007), where recent rodent and human studies have implicated intervention at the level of the NVU and BBB.

These are incredibly important in brain health and disease. Therefore, this review begins by explaining the cellular and molecular components of these systems, highlighting important molecules potentially regulated by cannabinoid ligands and then takes an unbiased look at the evidence in support (or otherwise) of cannabinoid receptor expression and control of the NVU and BBB function in humans.”

The Role of Nuclear Hormone Receptors in Cannabinoid Function.


“Since the early 2000s, evidence has been accumulating that most cannabinoid compounds interact with the nuclear hormone family peroxisome proliferator-activated receptors (PPARs). This can be through direct binding of these compounds to PPARs, metabolism of cannabinoid to other PPAR-activating chemicals, or indirect activation of PPAR through cell signaling pathways. Delivery of cannabinoids to the nucleus may be facilitated by fatty acid-binding proteins and carrier proteins. All PPAR isoforms appear to be activated by cannabinoids, but the majority of evidence is for PPARα and γ. To date, little is known about the potential interaction of cannabinoids with other nuclear hormones. At least some (but not all) of the well-known biological actions of cannabinoids including neuroprotection, antiinflammatory action, and analgesic effects are partly mediated by PPAR-activation, often in combination with activation of the more traditional target sites of action. This has been best investigated for the endocannabinoid-like compounds palmitoylethanolamide and oleoylethanolamine acting at PPARα, and for phytocannabinoids or their derivatives activation acting at PPARγ. However, there are still many aspects of cannabinoid activation of PPAR and the role it plays in the biological and therapeutic effects of cannabinoids that remain to be investigated.”

Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors.


“Of the druggable group of G protein-coupled receptors in the human genome, a number remain which have yet to be paired with an endogenous ligand-orphan GPCRs. Among these 100 or so entities, 3 have been linked to the cannabinoid system. GPR18, GPR55, and GPR119 exhibit limited sequence homology with the established CB1 and CB2 cannabinoid receptors. However, the pharmacology of these orphan receptors displays overlap with CB1 and CB2 receptors, particularly for GPR18 and GPR55. The linking of GPR119 to the cannabinoid receptors is less convincing and emanates from structural similarities of endogenous ligands active at these GPCRs, but which do not cross-react. This review describes the evidence for describing these orphan GPCRs as cannabinoid receptor-like receptors.”

Actions and Regulation of Ionotropic Cannabinoid Receptors.

“Almost three decades have passed since the identification of the two specific metabotropic receptors mediating cannabinoid pharmacology. Thereafter, many cannabinoid effects, both at central and peripheral levels, have been well documented and characterized. However, numerous evidences demonstrated that these pharmacological actions could not be attributable solely to the activation of CB1 and CB2 receptors since several important cannabimimetic actions have been found in biological systems lacking CB1 or CB2 gene such as in specific cell lines or transgenic mice. It is now well accepted that, beyond their receptor-mediated effects, these molecules can act also via CB1/CB2-receptor-independent mechanism. Cannabinoids have been demonstrated to modulate several voltage-gated channels (including Ca2+, Na+, and various type of K+ channels), ligand-gated ion channels (i.e., GABA, glycine), and ion-transporting membranes proteins such as transient potential receptor class (TRP) channels. The first direct, cannabinoid receptor-independent interaction was reported on the function of serotonin 5-HT3 receptor-ion channel complex. Similar effects were reported also on the other above mentioned ion channels. In the early ninety, studies searching for endogenous modulators of L-type Ca2+ channels identified anandamide as ligand for L-type Ca2+ channel. Later investigations indicated that other types of Ca2+ currents are also affected by endocannabinoids, and, in the late ninety, it was discovered that endocannabinoids activate the vanilloid receptor subtype 1 (TRPV1), and nowadays, it is known that (endo)cannabinoids gate at least five distinct TRP channels. This chapter focuses on cannabinoid regulation of ion channels and lays special emphasis on their action at transient receptor channels.”

Functional Selectivity at Cannabinoid Receptors.

Advances in Pharmacology

“It is now clear that, in contrast to traditional descriptions of G protein-coupled receptor signaling, agonists can activate or inhibit characteristic patterns of downstream effector pathways depending on their structures and the conformational changes induced in the receptor. This is referred to as functional selectivity (also known as agonist-directed trafficking, ligand-induced differential signaling, or biased agonism). It is important because even small structural differences can result in significant variations in overall agonist effects (wanted and unwanted) depending on which postreceptor signaling systems are engaged by each agonist/receptor pairing. In addition to the canonical signaling pathways mediated by Gi/o proteins, CB1 and CB2 receptor agonists can have effects via differential activation not only of Gi subtypes but also of Gs and Gq/11 proteins. For example, the classical cannabinoid HU-210 produces maximal activation of both Gi and Go proteins, while the endocannabinoid anandamide and aminoalkylindole WIN 55,212 both produce maximal activation of Gi, but submaximal activation of Go. Cannabinoid agonists can also signal differentially via β-arrestins coupled to mitogen-activated protein kinases, subsequently promoting varying degrees of receptor internalization and agonist desensitization. A recent extensive characterization of the molecular pharmacology of CB2 agonists (Soethoudt et al., 2017) identified marked differences (bias) in the ability of certain agonists to activate distinct signaling pathways (cAMP accumulation, ERK phosphorylation, GIRK activation, GTPγS binding, and β-arrestin recruitment) and to cause off-target effects, exemplifying the need to evaluate functional selectivity in agonist drug development.”

CB1 and CB2 Receptor Pharmacology.

Advances in 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.”

Endocannabinoid Analytical Methodologies: Techniques That Drive Discoveries That Drive Techniques.

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“Identification of the two major endogenous cannabinoid ligands, known as endocannabinoids, N-arachidonoyl-ethanolamine (anandamide, AEA) and 2-arachidonoyl-glycerol (2-AG), opened the way for the identification and isolation of other lipid congeners, all derivatives of fatty acids and related to the Endocannabinoid System. The nomenclature of this anandamide-type class of lipids is evolving as new species are discovered all the time. However, they each fall under the larger umbrella of lipids that are a conjugation of a fatty acid with an amine through and amide bond, which we will refer to as lipoamines. Specific subspecies of lipoamines that have been discovered are the N-acyl-ethanolamides (including AEA), N-acyl-dopamines, N-acyl-serotonins, N-acyl-GABA, N-acyl-taurines, and a growing number of N-acyl amino acids. Emerging data from multiple labs also show that monoacylglycerols (including 2-AG), COX-2 metabolites, and fatty acid esters of hydroxyl fatty acids are interconnected with these lipoamines at both the biosynthetic and metabolic levels. Understanding the molecular relatedness of these lipids is important for studying how they act as signaling molecules; however, a first step in this process hinges on advances in being able to accurately measure them.”