The Endocannabinoid System and Potential Therapeutic Ingredients

Since the discovery of the endocannabinoid system (ECS) in the 1990s, this signalling system has attracted intense attention, especially as it aided understanding of the effects of phytocannabinoids. Furthermore, detailing the various components of the ECS uncovered the fascinating complexity of how this signalling system acts in the functional network of the entire organism, particulary in the brain.

The ECS has been studied to identify the molecular structures present in Cannabis sativa. The ECS consists of cannabinoid receptors, endogenous ligands, and the associated enzymatic apparatus responsible for maintaining energy homeostasis and cognitive processes. Several physiological effects of cannabinoids are exerted through interactions with various receptors, such as CB1 and CB2 receptors, vanilloid receptors, and the recently discovered G-protein-coupled receptors.

Anandamide (AEA) and 2-arachidoylglycerol (2-AG), two small lipids derived from arachidonic acid, showed high-affinity binding to CB1 and CB2 receptors. ECS plays a critical role in chronic pain and mood disorders and has been extensively studied because of its wide therapeutic potential and because it is a promising target for the development of new drugs. Phytocannabinoids and synthetic cannabinoids have shown varied affinities for the ECS and are relevant to the treatment of several neurological diseases¹.

The ECS is a highly versatile signalling system within the nervous system. The endocannabinoid system is a complex network of receptors, enzymes, and endogenous lipid-based retrograde neurotransmitters that play a crucial role in regulating a wide range of physiological and pathological processes^1,2,3. This system is involved in the modulation of pain and inflammation, as well as various other functions such as mood, appetite, and memory. 

The two main cannabinoid receptors, CB1 and CB2, have been extensively studied and are known to mediate the effects of both endocannabinoids and phytocannabinoids, such as the psychoactive compound Δ9-tetrahydrocannabinol found in the cannabis plant. Activation of CB1 receptors, primarily located in the central nervous system, can produce analgesic, anti-inflammatory, and neuroprotective effects, while CB2 receptors, predominantly expressed in the peripheral immune system, are involved in modulating inflammatory and immune responses^2,3,4.

FIGURE 1. CB1 and CB2 cannabinoid receptors and their distribution in the human body

Taken from: Rezende B, Alencar AKN, de Bem GF, Fontes-Dantas FL, Montes GC. Endocannabinoid System: Chemical Characteristics and Biological Activity. Pharmaceuticals (Basel). 2023 Jan 19;16(2):148. doi: 10.3390/ph16020148. PMID: 37017445; PMCID: PMC9966761.

In addition to the cannabinoid receptors, the ECS also includes the endogenous ligands, AEA and 2-AG, as well as the enzymes responsible for their synthesis and degradation². These endocannabinoids have been shown to exhibit a range of therapeutic properties, including pain relief, anti-inflammatory, and neuroprotective effects. It appears that the ECS plays roles in the fine-tuning of physiological processes that keep the body in homeostatic set-points.

The ECS is also widely involved in the regulation of peripheral immune, cardiovascular, metabolic, gastrointestinal, muscular, and peripheral nervous system processes, which in turn can influence central nervous system (CNS) functions. The ECS is evolutionarily well conserved in vertebrates, is widely distributed in the body, and takes a central position in the regulation of a myriad of biological processes, both in neural and non-neural tissues. It is intertwined with many neurotransmitter and lipid signalling systems, thereby integrated into broad functional networks. It appears that the ECS plays roles in the fine-tuning of physiological processes that keep the body in homeostatic set-points.

ECS dysregulation can also be induced by particular life factors, such as living under chronic stress, or by metabolic factors, such as obesity. Pharmacological interventions targeting ECS activity aim to normalize such pathophysiological processes, thereby rescuing the subject from unfavourable allostatic set points.

Functions of the ECS helps to maintain homeostasis in the body, for example, through regulation of the stress response, feeding, and energy metabolism, and for ensuring the excitatory/inhibitory balance in the nervous system. Considering the temporal and spatial activity of the ECS, it is no surprise that a dysregulated ECS can lead to new set points, called allostasis, that might then be implicated in distinct neuropsychiatric disorders.

The biosynthesis of endocannabinoids occurs from membrane precursors, and the ECS degradation products are precursors of eicosanoids. Thus, ECS signalling is integrated into a lipid metabolism and signalling network¹.

Exogenous, plant-based cannabinoids and related compounds, such as terpenes, have also been investigated for their potential therapeutic applications.

Studies have suggested that compounds like cannabidiol and β-caryophyllene, when used in combination, may provide effective pain relief and anti-inflammatory benefits without the psychoactive effects associated with Δ9-tetrahydrocannabinoids^2,3,4.

The endocannabinoid system and its modulation have been implicated in a wide range of pathological conditions, including chronic pain, inflammation, and neurological disorders. Ongoing research continues to explore the therapeutic potential of targeting the endocannabinoid system, with a focus on developing selective agonists and antagonists that can harness the beneficial effects while minimizing undesirable side effects^1,2,4,5.

Recently, the ECS has been expanded, and researchers have named it the endocannabinoidome (ECSome), a meaningful reference that includes all components as well as proteins, enzymes, and lipids that are directly or indirectly involved in cannabinoid system modulation and significantly affect health

Natural products have a long history of interactions with CB receptors. Preparations of the medicinal plant Cannabis sativa have been therapeutically used for thousands of years before their mechanism of action – the activation of CB receptors – had been discovered and the active constituents like THC  had been identified. In addition to cannabis constituents further plant-derived natural products have been reported to interact with the endocannabinoid system, including the terpene beta-caryophyllene, fatty acid derivatives, such as N-linoleoylethanolamide, and various N-alkylamides from Echinacea spp. These compounds may either act directly on CB receptors (beta-caryophyllene) or indirectly by inhibition of endocannabinoid degradation.

Phytocannabinoids, such as cannabidiol (CBD), have wide therapeutic applicability, possibly because of their ability to target numerous receptors. The ECSome plays a role in the microbiota–gut–brain axis, which has emerged as an important player in the control of affective and cognitive functions and their pathological changes. However, the molecular and biochemical bases of the interaction and the biological relationships of the new receptor subtypes with cannabinoid ligands have not been fully elucidated; therefore, further studies are needed.

Endocannabinoids, unlike classical neurotransmitters, are considered atypical messengers because of the modulation of information from postsynaptic terminals to presynaptic terminals, which is known as the retrograde signalling mechanism. Endogenous ligands are synthesized on demand or by activity dependent on the cleavage of the phospholipid membrane and are released immediately after their biosynthesis to act as pro-homeostatic factors through interactions with specific receptors.

Molecules that modulate the endocannabinoid system

Cannabis, an herbal medicine, is a complex mixture of several compounds, including cannabinoid phenols, non-cannabinoid phenols (simple phenols, spiro-indans, dihydrophenanthrenes, and dihydrostilbenes), flavonoids, terpenoids, alcohols, aldehydes, n-alkanes, wax esters, steroids, and alkaloids.

However, in the past, studies were focused on the two most abundant phytocannabinoids, THC and CBD, thus resulting in greater knowledge about their pharmacological activities and increasing interest in the numerous possibilities of the medicinal actions of the plant. CBD has been gaining prominence in pharmacological research since the 1970s.

Since research with derivatives of Cannabis has started and the biological functions of isolated compounds in experimental and human diseases have shown promising outcomes, it is evident that selective ligands of specific Cannabis receptors could induce beneficial outcomes, depending on the clinical condition. More research on the biological function of each Cannabis derivative should be encouraged⁶.

Palmitoylethanolamide (PEA)

N-Palmitoylethanolamide (PEA) is a non-endocannabinoid lipid mediator belonging to the class of the N-acylethanolamine phospholipids and was first isolated from soy lecithin, egg yolk, and peanut meal.

PEA, an endocannabinoid-like lipid mediator, has extensively documented anti-inflammatory, analgesic, antimicrobial, immunomodulatory and neuroprotective effects. It is well tolerated and devoid of side effects in animals and humans. PEA’s actions on multiple molecular targets while modulating multiple inflammatory mediators provide therapeutic benefits in many applications, including immunity, brain health, allergy, pain modulation, joint health, sleep and recovery. PEA’s poor oral bioavailability, a major obstacle in early research, has been overcome by advanced delivery systems now licensed as food supplements. Belongs to the N-acyl-ethanolamine (NAE) fatty acid amide family. It is synthesized on demand within the lipid bilayer, it acts locally and is found in all tissues including the brain.

PEA is thought to be produced as a pro-homeostatic protective response to cellular injury and is usually up-regulated in disease states. PEA’s multi-faceted effects are due to its unique mechanisms of action that affect multiple pathways at different sites; primarily targeting the nuclear receptor peroxisome proliferator-activated alpha (PPAR-α), PEA also acts on novel cannabinoid receptor, G protein-coupled receptor 55 (GPR55) and G protein-coupled receptor 119 (GPR119). Moreover, it indirectly activates cannabinoid receptors 1 and 2 (CB1 and CB2) through inhibiting the degradation of the endocannabinoid, AEA, a phenomenon known as the ‘entourage effect’. Additionally, PEA activates and desensitizes the transient receptor potential vanilloid receptor 1 (TRPV1) channels. PEA-containing products are already licensed for use in humans (generally 1,200 mg/day) as a nutraceutical, a food supplement, or a food for medical purposes, depending on the country. PEA is especially used in humans for its analgesic and anti-inflammatory properties and has demonstrated high safety and tolerability. In the last decade, several studies suggested that PEA might exert protection against neuroinflammation and neurodegeneration, thus indicating that the compound possesses exceptional potential as a novel treatment for neurodegenerative disorders significant anti-nociceptive effect⁷.

Magnolia (Magnolia officinalis)

The bark of Magnolia officinalis is used in Asian traditional medicine for the treatment of anxiety, sleeping disorders, and allergic diseases. Study found that the extract and its main bioactive constituents, magnolol and honokiol, can activate CB receptors⁸.

Commercially available Magnolia bark extracts appear to be marketed based on their high phenolic content, with magnolol and honokiol ranging from 40% to 90% of total polyphenols. Many national institutions in Europe have given safety approval and included M. officinalis in the herbal preparations list suitable for food supplements.

Echinacea (Echinacea purpurea and E. angustifolia)

Echinacea is perhaps the best known medicinal plant of North America and has a long and rich cultural history of use. Classic ethnopharmacology research on echinacea, mostly with E. purpurea (L.) Moench and E. angustifolia DC (Asteraceae), has focused mainly on activities such as antimicrobial action and immunomodulation in relation to traditional pharmacopoeial uses for colds and flu

Recent research has revealed a relevant new mechanism of pain management by echinacea mediated by alkylamides (AKA) acting at the CB receptors (Woelkart et al., 2005; Raduner et al., 2006; Hohmann et al., 2011). In addition to selectively binding and activating CB2 receptors, certain echinacea AKA can modulate ECS activity through effects on endocannabinoid metabolism and transport¹¹.

FIGURE 2. Properties of Echinacea purpurea (L.) Moench.

Taken from: Burlou-Nagy, C., Bănică, F., Jurca, T., Vicaș, L. G., Marian, E., Muresan, M. E., Bácskay, I., Kiss, R., Fehér, P., & Pallag, A. (2022). Echinacea purpurea (L.) Moench: Biological and Pharmacological Properties. A Review. Plants (Basel, Switzerland), 11(9), 1244. https://doi.org/10.3390/plants11091244

Alkylamides have been shown to be effective on CB2, which is thought to be one of the mechanisms behind their immunomodulatory characteristics. Echinacea alkylamides exhibit cannabinomimetic activities on two specific types of G protein-coupled receptors, CB1 and CB2 cannabinoid receptors; this might be owing to structural similarities between them and anandamide, which is a natural cannabinoid receptor ligand.

In contrast to the psychoactive effects of CB1 receptor agonists, drugs that act on CB2 receptors appear as promising drugs to fight inflammatory diseases. The CB2 receptor is located mainly in the periphery, especially in the blood cells and in the organs that produce blood cells. Recently, the results reconfirmed the agonist activity of alkylamide derivatives, which demonstrates selectivity for CB2. Other research found that TNF expression was revealed to be modulated by alkylamides found in Echinacea extracts. In human monocytes and macrophages, Echinacea extracts modulate mRNA through the CB2 receptor, as well as inhibition of stimulated LPS and TNF-α. Based on these data, extracts derived from E. purpurea support the promise of anti-inflammatory and anti-pruritic benefits. It is known that the endocannabinoid system regulates several parts of the immune functions and the skin barrier; therefore, targeting it may be a viable method of reducing the symptoms of atopic eczema.

Cannabinomimetic properties are also important for anxiolitic effect. Echinacea medicines were tested for anxiolytic efficacy among animals used in studies at reduced concentrations as compared to those that utilized unconventional applications. There is little information available about Echinacea and anxiety, but in the future, it will be possible to do research to prevent or even treat anxiety¹².

LCPUFA

N-6 and n-3 long-chain polyunsaturated fatty acids (LCPUFA) are essential components of membrane phospholipids and also precursors to a large and ever-expanding repertoire of bioactive lipid mediators. The brain is highly enriched in the n-6 PUFA, arachidonic acid (ARA), and the n-3 PUFA, docosahexaenoic acid (DHA), with both essential for optimum brain development and function. Elevated dietary intake of DHA and eicosapentaenoic acid (EPA), another n-3 LCPUFA, has beneficial effects on learning and memory, decreases neuroinflammatory processes and enhances synaptic plasticity and neurogenesis.

ARA is the precursor to a wide range of mediators, including the two major endocannabinoids in the brain. Thus, there is considerable overlap in the effects of n-3 PUFA and the endocannabinoid system. ARA and DHA are the two main PUFA in the brain. These LCPUFA can be supplied either preformed from the diet or synthesised in the liver from their shorter chain precursors, linoleic acid (LA, 18:2n-6) and α-linolenic acid (ALA, 18:3n-3).  n-6 and n-3 PUFAs are also precursors to endogenous ligands of the endocannabinoid receptors. Due to their fundamental nature, ARA, DHA, EPA and their mediators and the endocannabinoid system have wide-ranging effects across the CNS and recent evidence strongly indicates a complex interplay between them. The levels of phospholipid-bound ARA determine the levels of 2-AG and AEA, which in addition to their own biological activities act as reservoirs of ARA for subsequent eicosanoid production⁹.

Amount of ω-3 and ω-6 PUFAs provided by food has direct consequences on their bioavailability and it has been established that the ideal ratio in the diet is of about 5:1 of ω-6:ω-3 PUFAs precursors. However, our modern diet is hugely unbalanced with an estimated average ratio of 20:1. The dietary deficit in ω-3 PUFAs has been associated with numerous diseases, and it becomes evident that an imbalance of ω-3/ω-6 PUFAs in the brain is linked to several neurological and neuropsychiatric disorders .

2-AG and AEA, these two canonical endocannabinoids are derived from the ω-6 PUFA ARA and most of studies have focused on these endocannabinoids. However, more and more studies are highlighting the role of ω-3-derived endocannabinoids. These species are agonists of CB1 and CB2 receptors, but their role in neuroplasticity is yet to be unravelled.

Briefly, there is a two-step process to form endocannabinoids from phospholipids. Endocannabinoids are made on demand and they are rapidly degraded, back into PUFAs or oxidized into active metabolites.

Generally, the conclusion from the studies¹⁰ is that modulating dietary PUFAs inevitably modulates levels of endocannabinoids in the organism. In addition, it often emerges from these studies the idea that it exists ‘good endocannabinoids’ and ‘bad endocannabinoids’. In this concept, ARA-derived endocannabinoids need to be down-regulated in pathological states (obesity, inflammation, etc.), and a diet rich in ω-3 decreases the levels of ARA-derived endocannabinoids (the ‘bad’ one), in favor to ω-3-derived endocannabinoids (the ‘good’ one). This appealing hypothesis needs to be studied because the presence of ω-3-derived endocannabinoids in the organism is known, but their function remains to be fully investigated.

In conclusion, dietary ω-6/ω-3 PUFAs appear as potent modulators and homeostatic regulators of endocannabinoids in the brain. The consequences of this modulation need to be investigated to understand its putative role in brain health and diseases (in particular those with endocannabinoid impairment) and develop future therapeutics to target the endocannabinoid system through dietary ω-6/ω-3 PUFAs. The most promising hypothesis that needs to be explored, the opinion is that dietary PUFAs could switch the system from ‘bad’ (ω-6-derived) endocannabinoids to ‘good’ (ω-3-derived) endocannabinoids¹⁰.

Conclusion

In conclusion, the endocannabinoid system (ECS) plays a pivotal role in maintaining homeostasis and regulating various physiological processes, including pain, inflammation, mood, and memory. With its complex receptors, ligands, and enzymes network, the ECS is a crucial target for therapeutic interventions, particularly in neurological and immune-related disorders. Ongoing research into phytocannabinoids, synthetic cannabinoids, and other plant-derived compounds continues to uncover promising avenues for treatment, highlighting the ECS’s potential in developing novel, effective therapies for a wide range of conditions.

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