Tag Archives: CB(1) and CB(2) receptors

An introduction to the endocannabinoid system: from the early to the latest concepts

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Abstract

“A rather complex and pleiotropic endogenous signalling system was discovered in the late 1990s, starting from studies on the mechanism of action of Delta(9)-tetrahydrocannabinol, the major psychoactive principle of the hemp plant Cannabis sativa. This system includes: (1) at least two G-protein-coupled receptors, known as the cannabinoid CB(1) and CB(2) receptors; (2) the endogenous agonists at these receptors, known as endocannabinoids, of which anandamide and 2-arachidonoylglycerol are the best known; and (3) proteins and enzymes for the regulation of endocannabinoid levels and action at receptors. The number of the members of this endocannabinoid signalling system seems to be ever increasing as new non-CB(1) non-CB(2) receptors for endocannabinoids, endocannabinoid-related molecules with little activity at CB(1) and CB(2) receptors, and new enzymes for endocannabinoid biosynthesis and degradation are being identified every year. The complexity of the endocannabinoid system and of its physiological and pathological function is outlined in this introductory chapter, for a better understanding of the subsequent chapters in this special issue.”

http://www.ncbi.nlm.nih.gov/pubmed/19285257

Pharmacological actions of cannabinoids.

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Abstract

“Mammalian tissues express at least two types of cannabinoid receptor, CB1 and CB2, both G protein coupled. CB1 receptors are expressed predominantly at nerve terminals where they mediate inhibition of transmitter release. CB2 receptors are found mainly on immune cells, one of their roles being to modulate cytokine release. Endogenous ligands for these receptors (endocannabinoids) also exist. These are all eicosanoids; prominent examples include arachidonoylethanolamide (anandamide) and 2-arachidonoyl glycerol. These discoveries have led to the development of CB1- and CB2-selective agonists and antagonists and of bioassays for characterizing such ligands. Cannabinoid receptor antagonists include the CB1-selective SR141716A, AM251, AM281 and LY320135, and the CB2-selective SR144528 and AM630. These all behave as inverse agonists, one indication that CB1 and CB2 receptors can exist in a constitutively active state. Neutral cannabinoid receptor antagonists that seem to lack inverse agonist properties have recently also been developed. As well as acting on CB1 and CB2 receptors, there is convincing evidence that anandamide can activate transient receptor potential vanilloid type 1 (TRPV1) receptors. Certain cannabinoids also appear to have non-CB1, non-CB2, non-TRPV1 targets, for example CB2-like receptors that can mediate antinociception and “abnormal-cannabidiol” receptors that mediate vasorelaxation and promote microglial cell migration. There is evidence too for TRPV1-like receptors on glutamatergic neurons, for alpha2-adrenoceptor-like (imidazoline) receptors at sympathetic nerve terminals, for novel G protein-coupled receptors for R-(+)-WIN55212 and anandamide in the brain and spinal cord, for novel receptors for delta9-tetrahydrocannabinol and cannabinol on perivascular sensory nerves and for novel anandamide receptors in the gastro-intestinal tract. The presence of allosteric sites for cannabinoids on various ion channels and non-cannabinoid receptors has also been proposed. In addition, more information is beginning to emerge about the pharmacological actions of the non-psychoactive plant cannabinoid, cannabidiol. These recent advances in cannabinoid pharmacology are all discussed in this review.”

http://www.ncbi.nlm.nih.gov/pubmed/16596770

The endocannabinoid system: a drug discovery perspective.

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Abstract

“The endocannabinoids are lipid messengers that engage the same cell surface receptors targeted by delta9-tetrahydrocannabinol, the active component of marijuana. They are produced by cells in the brain and other tissues and combine with two subtypes of G protein-coupled cannabinoid receptors, CB1 and CB2. Their ability to modulate a variety of pathophysiological processes, including appetite, pain and mood, provides unique opportunities for drug discovery. Three such opportunities are discussed here: reduction of body weight through blockade of CB1 receptors, alleviation of pain through activation of extracerebral cannabinoid receptors, and modulation of pain and anxiety through inhibition of endocannabinoid degradation.”

http://www.ncbi.nlm.nih.gov/pubmed/16044662

[The endocannabinoid system as a target for the development of new drugs for cancer therapy].

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“Studies on the main bioactive components of Cannabis sativa, the cannabinoids, and particularly delta 9-tetrahydrocannabinol (THC), led to the discovery of a new endogenous signalling system that controls several physiological and pathological conditions: the endocannabinoid system. This comprises the cannabinoid receptors, their endogenous agonists–the endocannabinoids–and proteins for endocannabinoid biosynthesis and inactivation.

Recently, evidence has accumulated indicating that stimulation of cannabinoid receptors by either THC or the endocannabinoids influence the intracellular events controlling the proliferation and apoptosis of numerous types of cancer cells, thereby leading to anti-tumour effects both in vitro and in vivo.

This evidence is reviewed here and suggests that future anti-cancer therapy might be developed from our knowledge of how the endocannabinoid system controls the growth and metastasis of malignant cells.”

http://www.ncbi.nlm.nih.gov/pubmed/12723496

Endocannabinoid system modulation in cancer biology and therapy.

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“The discovery of the endocannabinoid system and the recognition of its potential impact in a plethora of pathological conditions, led to the development of therapeutic agents related to either the stimulation or antagonism of CB1 and CB2 cannabinoid receptors, the majority of which are actually tested in preclinical studies for the pharmacotherapy of several diseases. Endocannabinoid-related agents have been reported to affect multiple signaling pathways and biological processes involved in the development of cancer, displaying an interesting anti-proliferative, pro-apoptotic, anti-angiogenic and anti-metastatic activity both in vitro and in vivo in several models of cancer. Emerging evidence suggests that agonists of cannabinoid receptors, which share the useful property to discern between tumor cells and their non-transformed counterparts, could represent novel tumor-selective tools to treat cancer in addition to their already exploited use as palliative drugs to treat chemotherapy-induced nausea, pain and anorexia/weight loss in cancer patients. The aim of this review is to evidence and update the recent emerging knowledge about the role of the endocannabinoid system in cancer biology and the potentiality of its modulation in cancer therapy.”  http://www.ncbi.nlm.nih.gov/pubmed/19559362

http://www.sciencedirect.com/science/article/pii/S1043661809000863

Changes in the Endocannabinoid System May Give Insight into new and Effective Treatments for Cancer

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“The endocannabinoid system comprises specific cannabinoid receptors such as Cb1 and Cb2, the endogenous ligands (anandamide and 2-arachidonyl glycerol among others) and the proteins responsible for their synthesis and degradation. This system has become the focus of research in recent years because of its potential therapeutic value several disease states. The following review describes our current knowledge of the changes that occur in the endocannabinoid system during carcinogenesis and then focuses on the effects of anandamide on various aspects of the carcinogenic process such as growth, migration, and angiogenesis in tumors from various origins.

Marijuana and its derivatives have been used in medicine for centuries, however, it was not until the isolation of the psychoactive component of Cannabis sativa (Δ9-tetrahydrocannabinol; Δ9-THC) and the subsequent discovery of the endogenous cannabinoid signaling system that research into the therapeutic value of this system reemerged. Ongoing research is determining that regulation of the endocannabinoid system may be effective in the treatment of pain (Calignano et al., 1998; Manzanares et al., 1999), glaucoma (Voth and Schwartz, 1997), and neurodegenerative disorders such as Parkinson’s disease (Piomelli et al., 2000) and multiple sclerosis (Baker et al., 2000). In addition, cannabinoids might be effective anti-tumoral agents because of their ability to inhibit the growth of various types of cancer cell lines in culture (De Petrocellis et al., 1998; Ruiz et al., 1999; Sanchez et al., 1998, 2001) and in laboratory animals (Galve-Roperh et al., 2000).

In conclusion, the endocannabinoid system exerts a myriad of effects on tumor cell growth, progression, angiogenesis, and migration. With a notable few exceptions, targeting the endocannabinoid system with agents that activate cannabinoid receptors or increase the endogenous levels of AEA may prove to have therapeutic benefit in the treatment of various cancers. Further studies into the downstream consequences of AEA treatment are required and may illuminate other potential therapeutic targets.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2791688/

The endogenous cannabinoid, anandamide, induces COX-2-dependent cell death in apoptosis-resistant colon cancer cells.

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Abstract

“Despite recent advances in understanding colorectal tumour biology, there is still a need to improve the 5-year survival rate of patients with colorectal cancer as approximately 40% of patients presenting with advanced disease will remain resistant to therapy. One of the major contributing factors in resistance to therapy is the failure of colorectal tumour cells to undergo apoptosis. Hence there is an urgent need to develop novel therapeutic approaches that can target apoptosis-resistant cells. To this end, we investigated the potential efficacy of the endogenous cannabinoid anandamide to induce cell death in apoptosis-resistant colon cancer cells. Here, for the first time, we show that anandamide can induce cell death in the apoptosis-resistant HCT116 Bax-/- colorectal cell line. Importantly, we provide direct genetic evidence that this induction of cell death is dependent on COX-2 expression. Interestingly, increased COX-2 expression also sensitised the SW480 colorectal cancer cell line (low endogenous COX-2) to anandamide-induced death, whereas COX-2 suppression by RNAi inhibited anandamide-induced cell death in the HCA7 colorectal cancer cell line (high endogenous COX-2 expression). This COX-2-dependent death was independent of cannabinoid receptor engagement (CB1 or CB2), and not a direct consequence of reactive oxygen species (ROS) formation. This study demonstrates a novel utilisation for COX-2 expression, targeting apoptotic defective colorectal cancer cells for destruction by anandamide. As COX-2 is not expressed in the normal colorectal epithelium, but highly expressed in colorectal tumours and apoptosis resistance contributes to treatment failure, these data suggest that anandamide has the potential to be an effective therapeutic in colorectal cancer.”

http://www.ncbi.nlm.nih.gov/pubmed/20514410

Effects of anandamide on polyamine levels and cell growth in human colon cancer cells.

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Abstract

“BACKGROUND:

Anandamide (AEA) is an endogenous agonist for cannabinoid receptor CB1-R and seems to be involved in the control of cancer growth. Polyamines are compounds that play an important role in cell proliferation and differentiation. Our aim was to investigate the effect of AEA on the polyamine levels (putrescine, spermidine and spermine) and cell growth of three human colon cancer cell lines, positive for CB1-R.

MATERIALS AND METHODS:

After AEA treatment of DLD-1, HT-29 and SW620 cells, polyamine analysis was performed by high-performance liquid chromatography (HPLC) and cell growth was measured by 3-(4,5 di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. CB1 gene expression was determined using reverse transcription and polymerase chain reaction (RT-PCR).

RESULTS:

AEA significantly reduced polyamine levels and cell proliferation dose-dependently when the tested cell lines were exposed for 24 h and 48 h. This inhibitory effect was mediated by CB1-R, since SR 1411716A, a selective CB-1 receptor antagonist, was able to entirely antagonize the effect of AEA. CB1-R mRNA levels were enhanced after AEA treatment in DLD-1 cells, whereas no induction was found in HT-29 and SW620 cells.

CONCLUSION:

It appears that mechanisms by which AEA may affect growth of colon cancer cells involve a decrease in cell proliferation rate by reducing the polyamine levels.”

http://www.ncbi.nlm.nih.gov/pubmed/20682986

Differential expression of cannabinoid receptors in the human colon: cannabinoids promote epithelial wound healing.

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Abstract

“BACKGROUND & AIMS:

Two G-protein-coupled cannabinoid receptors, termed CB1 and CB2, have been identified and several mammalian enteric nervous systems express CB1 receptors and produce endocannabinoids. An immunomodulatory role for the endocannabinoid system in gastrointestinal inflammatory disorders has been proposed and this study sought to determine the location of both cannabinoid receptors in human colon and to investigate epithelial receptor function.

METHODS:

The location of CB1 and CB2 receptors in human colonic tissue was determined by immunohistochemistry. Primary colonic epithelial cells were treated with both synthetic and endogenous cannabinoids in vitro, and biochemical coupling of the receptors to known signaling events was determined by immunoblotting. Human colonic epithelial cell lines were used in cannabinoid-binding studies and as a model for in vitro wound-healing experiments.

RESULTS:

CB1-receptor immunoreactivity was evident in normal colonic epithelium, smooth muscle, and the submucosal myenteric plexus. CB1- and CB2-receptor expression was present on plasma cells in the lamina propria, whereas only CB2 was present on macrophages. CB2 immunoreactivity was seen in the epithelium of colonic tissue characteristic of inflammatory bowel disease. Cannabinoids enhanced epithelial wound closure either alone or in combination with lysophosphatidic acid through a CB1-lysophosphatidic acid 1 heteromeric receptor complex.

CONCLUSIONS:

CB1 receptors are expressed in normal human colon and colonic epithelium is responsive biochemically and functionally to cannabinoids. Increased epithelial CB2-receptor expression in human inflammatory bowel disease tissue implies an immunomodulatory role that may impact on mucosal immunity.”

http://www.ncbi.nlm.nih.gov/pubmed/16083701

Cannabinoid Receptor Activation Induces Apoptosis through Tumor Necrosis Factor α–Mediated Ceramide De novo Synthesis in Colon Cancer Cells

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Abstract

“PURPOSE:

Cannabinoids have been recently proposed as a new family of potential antitumor agents. The present study was undertaken to investigate the expression of the two cannabinoid receptors, CB1 and CB2, in colorectal cancer and to provide new insight into the molecular pathways underlying the apoptotic activity induced by their activation.

EXPERIMENTAL DESIGN:

Cannabinoid receptor expression was investigated in both human cancer specimens and in the DLD-1 and HT29 colon cancer cell lines. The effects of the CB1 agonist arachinodyl-2′-chloroethylamide and the CB2 agonist N-cyclopentyl-7-methyl-1-(2-morpholin-4-ylethyl)-1,8-naphthyridin-4(1H)-on-3-carboxamide (CB13) on tumor cell apoptosis and ceramide and tumor necrosis factor (TNF)-alpha production were evaluated. The knockdown of TNF-alpha mRNA was obtained with the use of selective small interfering RNA.

RESULTS:

We show that the CB1 receptor was mainly expressed in human normal colonic epithelium whereas tumor tissue was strongly positive for the CB2 receptor. The activation of the CB1 and, more efficiently, of the CB2 receptors induced apoptosis and increased ceramide levels in the DLD-1 and HT29 cells. Apoptosis was prevented by the pharmacologic inhibition of ceramide de novo synthesis. The CB2 agonist CB13 also reduced the growth of DLD-1 cells in a mouse model of colon cancer. The knockdown of TNF-alpha mRNA abrogated the ceramide increase and, therefore, the apoptotic effect induced by cannabinoid receptor activation.

CONCLUSIONS:

The present study shows that either CB1 or CB2 receptor activation induces apoptosis through ceramide de novo synthesis in colon cancer cells. Our data unveiled, for the first time, that TNF-alpha acts as a link between cannabinoid receptor activation and ceramide production.”

http://clincancerres.aacrjournals.org/content/14/23/7691.long