Endocannabinoid system as a regulator of tumor cell malignancy – biological pathways and clinical significance

“The endocannabinoid system (ECS) comprises cannabinoid receptors (CBs), endogenous cannabinoids, and enzymes responsible for their synthesis, transport, and degradation of (endo)cannabinoids.

To date, two CBs, CB1 and CB2, have been characterized; however, orphan G-protein-coupled receptor GPR55 has been suggested to be the third putative CB.

Several different types of cancer present abnormal expression of CBs, as well as other components of ECS, and this has been shown to correlate with the clinical outcome.

Although most effects of (endo)cannabinoids are mediated through stimulation of classical CBs, they also interact with several molecules, either prosurvival or proapoptotic molecules.

It should be noted that the mode of action of exogenous cannabinoids differs significantly from that of endocannabinoid and results from the studies on their activity both in vivo and in vitro could not be easily compared.

This review highlights the main signaling pathways involved in the antitumor activity of cannabinoids and the influence of their activation on cancer cell biology.

We also discuss changes in the expression pattern of the ECS in various cancer types that have an impact on disease progression and patient survival.

A growing amount of experimental data imply possible exploitation of cannabinoids in cancer therapy.”


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Cannabinoid activation of PPARα; a novel neuroprotective mechanism

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“The cannabinoids are a structurally diverse family of compounds with a large number of different biological targets.

Although CB1 receptor activation evokes neuroprotection in response to cannabinoids, some cannabinoids have been reported to be peroxisome proliferator activated receptor (PPAR) ligands, offering an alternative protective mechanism.

We have, therefore, investigated the ability of a range of cannabinoids to activate PPARα and for N-oleoylethanolamine (OEA), an endogenous cannabinoid-like compound (ECL), to evoke neuroprotection.

These data demonstrate the potential for a range of cannabinoid compounds, of diverse structures, to activate PPARα and suggest that at least some of the neuroprotective properties of these agents could be mediated by nuclear receptor activation.

In summary, the data presented here provide strong evidence that selected cannabinoids are PPARα agonists, and suggest a novel means by which the multiple effects of cannabinoids, in both the CNS and periphery, could be brought about.

In addition to its well-recognized role in lipid metabolism, PPARα activation showed obvious beneficial effects in ischaemic brain damage, which is likely to be connected with its anti-inflammatory action through the NF–κB pathway.

These discoveries not only broaden the potential use of cannabinoids as therapeutic agents, but also support PPARα as a new target for neuroprotective treatment.”


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Evaluation of Δ(9)-tetrahydrocannabinol metabolites and oxidative stress in type 2 diabetic rats.

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Cannabis has been known to be the oldest psychoactive plant for years. It is classified in the Cannabis genus, which is part of the Cannabacea family.

Cannabis sativa L. is the most common species. Δ9-tetrahydrocannabinol (THC) is the main psychoactive constituent identified in Cannabis sativa L.

THC is the most notable cannabinoid among all phytocannabinoids.

THC is exposed to degradation and converted into its active and inactive metabolites that are conjugated with glucuronic acid, and excreted in urine. THC is converted to active metabolite, 11-hydroxy-Δ9-THC (11-OH-THC), and then converted to an inactive metabolite, 11-nor-9-carboxy- Δ9-THC (THC – COOH).

ElSohly and Slade mention that C. sativa and its products have been used as medicinal agents.

Cannabinoids show a variety of therapeutic effects against chronic pain and muscle spasms, nausea and anorexia caused by HIV treatment, vomiting and nausea caused by cancer chemotherapy as well as anorexia associated with weight loss caused by immune deficiency syndrome.

Many studies report that THC provides protection against neuronal injury in a cell culture model of Parkinson disease and experimental models of Huntington disease, exhibits anti-oxidative action and mitigates the severity of the autoimmune response in an experimental model of diabetes.

The development and progression of diabetes mellitus and its complications arise out of increased oxidative damage. Kassab and Piwowar report that the best-known pathways of diabetic complications include oxidative stress.

The aims of the study presented in this paper were: (a) to explain the effects of THC on oxidative stress in T2DM treated with THC and (b) to determine the level of THC metabolites in the urine of diabetic and control rats induced by THC injection.

The object of the study is to examine the effects of Δ(9)-tetrahydrocannabinol (THC) against oxidative stress in the blood and excretion of THC metabolites in urine of type 2 diabetic rats.

These findings highlight that THC treatment may attenuate slightly the oxidative stress in diabetic rats.”


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Cannabidiol attenuates cardiac dysfunction, oxidative stress, fibrosis, inflammatory and cell death signaling pathways in diabetic cardiomyopathy

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“CBD, the most abundant nonpsychoactive constituent of Cannabis sativa (marijuana) plant, exerts antiinflammatory effects in various disease models and alleviates pain and spasticity associated with multiple sclerosis in humans.

In this study, we have investigated the effects of cannabidiol (CBD) on myocardial dysfunction, inflammation, oxidative/nitrosative stress, cell death and interrelated signaling pathways, using a mouse model of type I diabetic cardiomyopathy and primary human cardiomyocytes exposed to high glucose.

 A previous study has demonstrated cardiac protection by CBD in myocardial ischemic reperfusion injury; therefore, we have investigated the potential protective effects of CBD in diabetic hearts and in primary human cardiomyocytes exposed to high glucose.
Our findings underscore the potential of CBD for the prevention/treatment of diabetic complications.
Collectively, these results coupled with the excellent safety and tolerability profile of cannabidiol in humans, strongly suggest that it may have great therapeutic potential in the treatment of diabetic complications, and perhaps other cardiovascular disorders, by attenuating oxidative/nitrosative stress, inflammation, cell death and fibrosis.”
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Cannabinoids protect cells from oxidative cell death: a receptor-independent mechanism.

Journal of Pharmacology and Experimental Therapeutics

“Serum is required for the survival and growth of most animal cells. In serum-free medium, B lymphoblastoid cells and fibroblasts die after 2 days.

We report that submicromolar concentrations of Delta(9)-tetrahydrocannabinol (THC), Delta(8)-THC, cannabinol, or cannabidiol, but not WIN 55,212-2, prevented serum-deprived cell death. Delta(9)-THC also synergized with platelet-derived growth factor in activating resting NIH 3T3 fibroblasts.

The cannabinoids‘ growth supportive effect did not correlate with their ability to bind to known cannabinoid receptors and showed no stereoselectivity, suggesting a nonreceptor-mediated pathway.

Direct measurement of oxidative stress revealed that cannabinoids prevented serum-deprived cell death by antioxidation.

The antioxidative property of cannabinoids was confirmed by their ability to antagonize oxidative stress and consequent cell death induced by the retinoid anhydroretinol.

Therefore, cannabinoids act as antioxidants to modulate cell survival and growth of B lymphocytes and fibroblasts.”


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Cannabidiol protects an in vitro model of the blood-brain barrier from oxygen-glucose deprivation via PPARγ and 5-HT1A receptors.

“In vivo and in vitro studies have demonstrated a protective effect of cannabidiol (CBD) in reducing infarct size in stroke models and against epithelial barrier damage in numerous disease models.

We aimed to investigate whether CBD also affects blood-brain barrier (BBB) permeability following ischaemia.


These data suggest that preventing permeability changes at the BBB could represent an as yet unrecognized mechanism of CBD-induced neuroprotection in ischaemic stroke, a mechanism mediated by activation of PPARγ and 5-HT1A receptors.”


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Cannabidiol attenuates high glucose-induced endothelial cell inflammatory response and barrier disruption.

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“Cannabinoids, components of the Cannabis sativa (marijuana) plant, are known to exert potent anti-inflammatory, immunomodulatory and analgesic effects through activation of cannabinoid-1 and -2 (CB1 and CB2) receptors located in the central nervous system and immune cells.

The limitation of the therapeutic utility of the major cannabinoid, Δ9-tetrahydrocannabinol, is the development of psychoactive effects through central nervous system CB1 receptor. In contrast, cannabidiol (CBD), one of the most abundant cannabinoids of Cannabis sativa with reported antioxidant, anti-inflammatory, and immunomodulatory effects is well tolerated without side effects when chronically administered to humans and is devoid of psychoactive properties due to a low affinity for the CB1 and CB2 receptors.

A nonpsychoactive cannabinoid cannabidiol (CBD) has been shown to exert potent anti-inflammatory and antioxidant effects and has recently been reported to lower the incidence of diabetes in nonobese diabetic mice and to preserve the blood-retinal barrier in experimental diabetes.

In this study we have investigated the effects of CBD on high glucose (HG)-induced, mitochondrial superoxide generation, NF-κB activation, nitrotyrosine formation, inducible nitric oxide synthase (iNOS) and adhesion molecules ICAM-1 and VCAM-1 expression, monocyte-endothelial adhesion, transendothelial migration of monocytes, and disruption of endothelial barrier function in human coronary artery endothelial cells (HCAECs).

HG markedly increased mitochondrial superoxide generation (measured by flow cytometry using MitoSOX), NF-κB activation, nitrotyrosine formation, upregulation of iNOS and adhesion molecules ICAM-1 and VCAM-1, transendothelial migration of monocytes, and monocyte-endothelial adhesion in HCAECs. HG also decreased endothelial barrier function measured by increased permeability and diminished expression of vascular endothelial cadherin in HCAECs.

Remarkably, all the above mentioned effects of HG were attenuated by CBD pretreatment.

Since a disruption of the endothelial function and integrity by HG is a crucial early event underlying the development of various diabetic complications, our results suggest that CBD, which has recently been approved for the treatment of inflammation, pain, and spasticity associated with multiple sclerosis in humans, may have significant therapeutic benefits against diabetic complications and atherosclerosis.

Collectively, our results suggest that the nonpsychoactive cannabinoid CBD have significant therapeutic benefits against diabetic complications and atherosclerosis by attenuating HG-induced mitochondrial superoxide generation, increased NF-κB activation, upregulation of iNOS and adhesion molecules, 3-NT formation, monocyte-endothelial adhesion, TEM of monocytes, and disruption of the endothelial barrier function.

This is particularly encouraging in light of the excellent safety and tolerability profile of CBD in humans.”


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Δ9-tetrahydrocannabinol treatment improved endothelium-dependent relaxation on streptozotocin/nicotinamide-induced diabetic rat aorta.

“In this study, we investigated the possible effect of Δ(9)-tetrahydrocannabinol (THC), a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, on metabolic control and vascular complications of diabetes in streptozotocin/nicotinamide (STZ/NIC) induced type 2 diabetes mellitus.

These results suggested that THC improved endothelium-dependent relaxation in STZ/NIC induced diabetic rat aorta and that these effects were mediated at least in part, by control of hyperglycemia and enhanced endothelial nitric oxide bioavailability.”


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Biological effects of THC and a lipophilic cannabis extract on normal and insulin resistant 3T3-L1 adipocytes.

“Type 2 diabetes, a chronic disease, affects about 150 million people world wide.

It is characterized by insulin resistance of peripheral tissues such as liver, skeletal muscle, and fat. Insulin resistance is associated with elevated levels of tumor necrosis factor alpha (TNF-alpha), which in turn inhibits insulin receptor tyrosine kinase autophosphorylation.

It has been reported that cannabis is used in the treatment of diabetes.

A few reports indicate that smoking cannabis can lower blood glucose in diabetics.

Delta(9)-tetrahydrocannabinol (THC) is the primary psychoactive component of cannabis.”


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Decreased prevalence of diabetes in marijuana users: cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) III

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“To determine the association between diabetes mellitus (DM) and marijuana use.

We hypothesised that the prevalence of DM would be reduced in marijuana users due to the presence of one or more cannabinoids because of their immunomodulatory and anti-inflammatory properties.

Our analyses of adults aged 20–59 years in the NHANES III database showed that participants who used marijuana had lower prevalence of DM and had lower odds of DM relative to non-marijuana users.

We did not find an association between the use of marijuana and other chronic diseases, such as hypertension, stroke, myocardial infarction and heart failure.

Marijuana use was independently associated with a lower prevalence of DM.

In conclusion, marijuana use was associated with a decreased prevalence of DM.”


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