Endocannabinoids and the Cardiovascular System in Health and Disease.

“The endocannabinoid system is widely distributed throughout the cardiovascular system.

Endocannabinoids play a minimal role in the regulation of cardiovascular function in normal conditions, but are altered in most cardiovascular disorders.

In shock, endocannabinoids released within blood mediate the associated hypotension through CB1 activation. In hypertension, there is evidence for changes in the expression of CB1, and CB1 antagonism reduces blood pressure in obese hypertensive and diabetic patients.

The endocannabinoid system is also upregulated in cardiac pathologies.

This is likely to be cardioprotective, via CB2 and CB1 (lesser extent).

In the vasculature, endocannabinoids cause vasorelaxation through activation of multiple target sites, inhibition of calcium channels, activation of potassium channels, NO production and the release of vasoactive substances. Changes in the expression or function of any of these pathways alter the vascular effect of endocannabinoids.

Endocannabinoids have positive (CB2) and negative effects (CB1) on the progression of atherosclerosis. However, any negative effects of CB1 may not be consequential, as chronic CB1 antagonism in large scale human trials was not associated with significant reductions in atheroma.

In neurovascular disorders such as stroke, endocannabinoids are upregulated and protective, involving activation of CB1, CB2, TRPV1 and PPARα.

Although most of this evidence is from preclinical studies, it seems likely that cannabinoid-based therapies could be beneficial in a range of cardiovascular disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/26408169

Enhanced vasorelaxation effect of endogenous anandamide on thoracic aorta in renal vascular hypertension rats.

“Emerging evidence indicated that anandamide (AEA) stimulated vasorelaxation in both spontaneously hypertensive rats (SHRs) and L-NAME-induced hypertensive rats. Yet it remains unknown whether AEA modulates vasomotion of aorta in renovascular hypertensive (RVH) rats.

The aim of present study was to explore the effect of AEA on relaxation of thoracic aortas in two-kidney one-clip (2K1C)-induced RVH rats.

Taken together, the present study demonstrated that AEA enhanced endothelium-dependent aortic relaxation through activation of both CB1 and CB2 receptors and P-eNOS/NO pathway in 2K1C rats.”

http://www.ncbi.nlm.nih.gov/pubmed/26173564

Cardioprotective effect of cannabidiol in rats exposed to doxorubicin toxicity.

“The potential protective effect of cannabidiol, the major non-psychotropic Cannabis constituent, was investigated against doxorubicin cardiotoxicity in rats.

Histopathological examination showed that cannabidiol ameliorated doxorubicin-induced cardiac injury.

Immunohistochemical analysis revealed that cannabidiol significantly reduced the expression of inducible nitric oxide synthase, nuclear factor-κB, Fas ligand and caspase-3, and increased the expression of survivin in cardiac tissue of doxorubicin-treated rats.

These results indicate that cannabidiol represents a potential protective agent against doxorubicin cardiac injury.”

http://www.ncbi.nlm.nih.gov/pubmed/23721741

The endogenous cardiac cannabinoid system: a new protective mechanism against myocardial ischemia.

“The pharmacological (and recreational) effects of cannabis have been known for centuries. However, it is only recently that one has identified two subtypes of G-protein-coupled receptors, namely CB1 and CB2-receptors, which mediate the numerous effects of delta9-tetrahydrocannabinol and other cannabinoids.

Logically, the existence of cannabinoid-receptors implies that endogenous ligands for these receptors (endocannabinoids) exist and exert a physiological role. Hence, arachidonoylethanolamide (anandamide) and sn-2 arachidonoylglycerol, the first two endocannabinoids identified, are formed from plasma membrane phospholipids and act as CB1 and/or CB2 agonists.

The presence of both CB1 and CB2-receptors in the rat heart is noteworthy.

This endogenous cardiac cannabinoid system is involved in several phenomena associated with cardioprotective effects.

The reduction in infarct size following myocardial ischemia, observed in rats exposed to either LPS or heat stress 24 hours before, is abolished in the presence of a CB2-receptor antagonist.

Endocannabinoids and synthetic cannabinoids, the latter through either CB1 or CB2-receptors, exert direct cardioprotective effects in rat isolated hearts.

The ability of cannabinoids to reduce infarct size has been confirmed in vivo in anesthetized mice and rats. This latter effect appears to be mediated through CB2-receptors.

Thus, the endogenous cardiac cannabinoid system, through activation of CB2-receptors, appears to be an important mechanism of protection against myocardial ischemia.”

https://pubmed.ncbi.nlm.nih.gov/16618028

An ultra-low dose of tetrahydrocannabinol provides cardioprotection.

“Tetrahydrocannabinol (THC), the major psychoactive component of marijuana, is a cannabinoid agonist that exerts its effects by activating at least two specific receptors (CB1 and CB2) that belong to the seven transmembrane G-protein coupled receptor (GPCR) family.

Both CB1 and CB2 mRNA and proteins are present in the heart.

THC treatment was beneficial against hypoxia in neonatal cardiomyocytes in vitro.

We also observed a neuroprotective effect of an ultra low dose of THC when applied to mice before brain insults.

The present study was aimed to test and characterize the cardioprotective effects of a very low dose of THC…

All protocols of THC administration were found to be beneficial.

CONCLUSION:

A single ultra low dose of THC before ischemia is a safe and effective treatment that reduces myocardial ischemic damage.”

http://www.ncbi.nlm.nih.gov/pubmed/23537701

Delta-9-tetrahydrocannabinol protects cardiac cells from hypoxia via CB2 receptor activation and nitric oxide production.

“Delta-9-tetrahydrocannabinol (THC), the major active component of marijuana, has a beneficial effect on the cardiovascular system during stress conditions…

The present study was designed to investigate the central (CB1) and the peripheral (CB2)cannabinoid receptor expression in neonatal cardiomyoctes and possible function in the cardioprotection of THC from hypoxia.

The antagonist for the CB2, but not CB1 receptor antagonist abolished the protective effect of THC.

In agreement with these results using RT-PCR, it was shown that neonatal cardiac cells express CB2, but not CB1 receptors.

Involvement of NO in the signal transduction pathway activated by THC through CB2 was examined. It was found that THC induces nitric oxide (NO) production by induction of NO synthase (iNOS) via CB2 receptors.

L-NAME (NOS inhibitor, 100 microM) prevented the cardioprotection provided by THC.

Taken together, our findings suggest that THC protects cardiac cells against hypoxia via CB2 receptor activation by induction of NO production.

An NO mechanism occurs also in the classical pre-conditioning process; therefore, THC probably pre-trains the cardiomyocytes to hypoxic conditions.”

http://www.ncbi.nlm.nih.gov/pubmed/16444588

Cannabidiol, a nonpsychoactive Cannabis constituent, protects against myocardial ischemic reperfusion injury

Heart and Circulatory Physiology

“CANNABINOIDS ARE NATURAL and synthetic compounds structurally or pharmacologically related to the constituents of the plant Cannabis sativa or to the endogenous agonists (endocannabinoids) of the cannabinoid CB1 and CB2 receptors.

Cannabidiol (CBD) is a major cannabinoid constituent of Cannabis.

In contrast to tetrahydrocannabinol, CBD binds very weakly to CB1 and CB2 receptors. Contrary to most cannabinoids, CBD does not induce psychoactive or cognitive effects.

CBD has been shown to have anti-inflammatory properties. CBD (together with tetrahydrocannabinol) has been successfully tested in a few preliminary human trials related to autoimmune diseases…

Cannabidiol (CBD) is a major, nonpsychoactive Cannabis constituent with anti-inflammatory activity mediated by enhancing adenosine signaling.

Inasmuch as adenosine receptors are promising pharmaceutical targets for ischemic heart diseases, we tested the effect of CBD on ischemic rat hearts.

Our study shows that CBD induces a substantial in vivo cardioprotective effect from ischemia that is not observed ex vivo.

Inasmuch as CBD has previously been administered to humans without causing side effects, it may represent a promising novel treatment for myocardial ischemia.”

http://ajpheart.physiology.org/content/293/6/H3602

Effect of dietary hempseed intake on cardiac ischemia-reperfusion injury.

Regulatory, Integrative and Comparative Physiology

“Polyunsaturated fatty acids (PUFAs) have significant, cardioprotective effects against ischemia.

Hempseed contains a high proportion of the PUFAs linoleic acid (LA) and alpha-linolenic acid (ALA),

Hearts from rats fed a hempseed-supplemented diet exhibited significantly better postischemic recovery of maximal contractile function and enhanced rates of tension development and relaxation during reperfusion than hearts from the other groups.

Our data demonstrate that dietary hempseed can provide significant cardioprotective effects during postischemic reperfusion. This appears to be due to its highly enriched PUFA content.”  http://www.ncbi.nlm.nih.gov/pubmed/17122327

“Polyunsaturated fatty acids (PUFAs) have received special research attention because of their antiarrhythmic and cardioprotective effects in hearts challenged by an ischemia-reperfusion insult. There are two major types of PUFAs: omega-3 and omega-6. Linoleic acid (LA) and α-linolenic acid (ALA) are common examples of an omega-6 and an omega-3 fatty acid, respectively… We have demonstrated for the first time in this study that dietary hempseed represents an effective, unique method to significantly alter the levels of ALA in the heart. We have also demonstrated for the first time that dietary hempseed will confer beneficial cardioprotective effects in hearts subjected to ischemia-reperfusion challenge.”  http://ajpregu.physiology.org/content/292/3/R1198

CB(2) cannabinoid receptor activation is cardioprotective in a mouse model of ischemia/reperfusion.

“Preventive treatment with cannabinoid agonists has been reported to reduce the infarct size in a mouse model of myocardial ischemia/reperfusion.

Here we investigated the possible cardioprotective effect of selective CB(2) cannabinoid receptor activation during ischemia.

Our data suggest that administration during ischemia reduces the infarct size in a mouse model of myocardial ischemia/reperfusion through a direct cardioprotective activity on cardiomyocytes and neutrophils.”

http://www.ncbi.nlm.nih.gov/pubmed/19162037