Signaling Pathways Involved in the Cardioprotective Effects of Cannabinoids

Re-evaluation of the cardioprotective effects of cannabinoids against ischemia-reperfusion injury according to the IMproving Preclinical Assessment of Cardioprotective Therapies (IMPACT) criteria

Ischemic heart disease, associated with high morbidity and mortality, represents a major challenge for the development of drug-based strategies to improve its prognosis. Results of pre-clinical studies suggest that agonists of cannabinoid CB2 receptors and multitarget cannabidiol might be potential cardioprotective strategies against ischemia-reperfusion injury. The aim of our study was to re-evaluate the cardioprotective effects of cannabinoids against ischemia-reperfusion injury according to the IMproving Preclinical Assessment of Cardioprotective Therapies (IMPACT) criteria published recently by the European Union (EU) CARDIOPROTECTION COST ACTION. To meet the minimum criteria of those guidelines, experiments should be performed (i) on healthy small animals subjected to ischemia with reperfusion lasting for at least 2 hours and (ii) confirmed in small animals with comorbidities and co-medications and (iii) in large animals. Our analysis revealed that the publications regarding cardioprotective effects of CB2 receptor agonists and cannabidiol did not meet all three strict steps of IMPACT. Thus, additional experiments are needed to confirm the cardioprotective activities of (endo)cannabinoids mainly on small animals with comorbidities and on large animals. Moreover, our publication underlines the significance of the IMPACT criteria for a proper planning of preclinical experiments regarding cardiac ischemia-reperfusion injury.

CB2 Cannabinoid Receptor as a Potential Target in Myocardial Infarction: Exploration of Molecular Pathogenesis and Therapeutic Strategies

The lipid endocannabinoid system has recently emerged as a novel therapeutic target for several inflammatory and tissue-damaging diseases, including those affecting the cardiovascular system. The primary targets of cannabinoids are cannabinoid type 1 (CB1) and 2 (CB2) receptors. The CB2 receptor is expressed in the cardiomyocytes. While the pathological changes in the myocardium upregulate the CB2 receptor, genetic deletion of the receptor aggravates the changes. The CB2 receptor plays a crucial role in attenuating the advancement of myocardial infarction (MI)-associated pathological changes in the myocardium. Activation of CB2 receptors exerts cardioprotection in MI via numerous molecular pathways. For instance, delta-9-tetrahydrocannabinol attenuated the progression of MI via modulation of the CB2 receptor-dependent anti-inflammatory mechanisms, including suppression of pro-inflammatory cytokines like IL-6, TNF-α, and IL-1β. Through similar mechanisms, natural and synthetic CB2 receptor ligands repair myocardial tissue damage. This review aims to offer an in-depth discussion on the ameliorative potential of CB2 receptors in myocardial injuries induced by a variety of pathogenic mechanisms. Further, the modulation of autophagy, TGF-β/Smad3 signaling, MPTP opening, and ROS production are discussed. The molecular correlation of CB2 receptors with cardiac injury markers, such as troponin I, LDH1, and CK-MB, is explored. Special attention has been paid to novel insights into the potential therapeutic implications of CB2 receptor activation in MI.

Pharmacological Properties, Therapeutic Potential and Molecular Mechanisms of JWH133, a CB2 Receptor-Selective Agonist

The endocannabinoid system has attracted attention as a pharmacological target for several pathological conditions. Cannabinoid (CB2)-selective agonists have been the focus of pharmacological studies because modulation of the CB2 receptor (CB2R) can be useful in the treatment of pain, inflammation, arthritis, addiction, and cancer among other possible therapeutic applications while circumventing CNS-related adverse effects. Increasing number of evidences from different independent preclinical studies have suggested new perspectives on the involvement of CB2R signaling in inflammation, infection and immunity, thus play important role in cancer, cardiovascular, renal, hepatic and metabolic diseases. JWH133 is a synthetic agonist with high CB2R selectivity and showed to exert CB2R mediated antioxidant, anti-inflammatory, anticancer, cardioprotective, hepatoprotective, gastroprotective, nephroprotective, and immunomodulatory activities. Cumulative evidences suggest that JWH133 protects against hepatic injury, renal injury, cardiotoxicity, fibrosis, rheumatoid arthritis, and cancer as well as against oxidative damage and inflammation, inhibits fibrosis and apoptosis, and acts as an immunosuppressant. This review provides a comprehensive overview of the polypharmacological properties and therapeutic potential of JWH133. This review also presents molecular mechanism and signaling pathways of JWH133 under various pathological conditions except neurological diseases. Based on the available data, this review proposes the possibilities of developing JWH133 as a promising therapeutic agent; however, further safety and toxicity studies in preclinical studies and clinical trials in humans are warranted.

7-Azaindolequinuclidinones (7-AIQD): A novel class of cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptor ligands

A series of N-benzyl-7-azaindolequinuclidinone (7-AIQD) analogs have been synthesized and evaluated for affinity toward CB1 and CB2 cannabinoid receptors and identified as a novel class of cannabinoid receptor ligands. Structure-activity relationship (SAR) studies indicate that 7-AIQD analogs are dual CB1/CB2 receptor ligands exhibiting high potency with somewhat greater selectivity towards CB2 receptors compared to the previously reported indolequinuclidinone (IQD) analogs. Initial binding assays showed that 7-AIQD analogs 8b, 8d, 8f, 8g and 9b (1 μM) produced more that 50% displacement of the CB1/CB2 non-selective agonist CP-55,940 (0.1 nM). Furthermore, Ki values determined from full competition binding curves showed that analogs 8a, 8b and 8g exhibit high affinity (110, 115 and 23.7 nM, respectively) and moderate selectivity (26.3, 6.1 and 9.2-fold, respectively) for CB2 relative to CB1 receptors. Functional studies examining modulation of G-protein activity demonstrated that 8a acts as a neutral antagonist at CB1 and CB2 receptors, while 8b exhibits inverse agonist activity at these receptors. Analogs 8f and 8g exhibit different intrinsic activities, depending on the receptor examined. Molecular docking and binding free energy calculations for the most active compounds (8a, 8b, 8f, and 8g) were performed to better understand the CB2 receptor-selective mechanism at the atomic level. Compound 8g exhibited the highest predicted binding affinity at both CB1 and CB2 receptors, and all four compounds were shown to have higher predicted binding affinities with the CB2 receptor compared to their corresponding binding affinities with the CB1 receptor. Further structural optimization of 7-AIQD analogs may lead to the identification of potential clinical agents.

Innovative Therapeutic Potential of Cannabinoid Receptors as Targets in Alzheimer’s Disease and Less Well-Known Diseases

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The discovery of cannabinoid receptors at the beginning of the 1990s, CB1 cloned in 1990 and CB2 cloned in 1993, and the availability of selective and potent cannabimimetics could only be justified by the existence of endogenous ligands that are capable of binding to them. Thus, the characterisation and cloning of the first cannabinoid receptor (CB1) led to the isolation and characterisation of the first endocannabinoid, arachidonoylethanolamide (AEA), two years later and the subsequent identification of a family of lipid transmitters known as the fatty acid ester 2-arachidonoylglycerol (2-AG).

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The endogenous cannabinoid system is a complex signalling system that comprises transmembrane endocannabinoid receptors, their endogenous ligands (the endocannabinoids), the specific uptake mechanisms and the enzymatic systems related to their biosynthesis and degradation.

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The endocannabinoid system has been implicated in a wide diversity of biological processes, in both the central and peripheral nervous systems, including memory, learning, neuronal development, stress and emotions, food intake, energy regulation, peripheral metabolism, and the regulation of hormonal balance through the endocrine system.

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In this context, this article will review the current knowledge of the therapeutic potential of cannabinoid receptor as a target in Alzheimer’s disease and other less well-known diseases that include, among others, multiple sclerosis, bone metabolism, and Fragile X syndrome.

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The therapeutic applications will be addressed through the study of cannabinoid agonists acting as single drugs and multi-target drugs highlighting the CB2 receptor agonist.

Cannabinoids in the Cardiovascular System

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-CB_1/2 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.

Ligand activation of cannabinoid receptors attenuates hypertrophy of neonatal rat cardiomyocytes

: Endocannabinoids are bioactive amides, esters, and ethers of long-chain polyunsaturated fatty acids. Evidence suggests that activation of the endocannabinoid pathway offers cardioprotection against myocardial ischemia, arrhythmias, and endothelial dysfunction of coronary arteries. As cardiac hypertrophy is a convergence point of risk factors for heart failure, we determined a role for endocannabinoids in attenuating endothelin-1-induced hypertrophy and probed the signaling pathways involved. The cannabinoid receptor ligand anandamide and its metabolically stable analog, R-methanandamide, suppressed hypertrophic indicators including cardiomyocyte enlargement and fetal gene activation (ie, the brain natriuretic peptide gene) elicited by endothelin-1 in isolated neonatal rat ventricular myocytes. The ability of R-methanandamide to suppress myocyte enlargement and fetal gene activation was mediated by CB2 and CB1 receptors, respectively. Accordingly, a CB2-selective agonist, JWH-133, prevented only myocyte enlargement but not brain natriuretic peptide gene activation. A CB1/CB2 dual agonist with limited brain penetration, CB-13, inhibited both hypertrophic indicators. CB-13 activated AMP-activated protein kinase (AMPK) and, in an AMPK-dependent manner, endothelial nitric oxide synthase (eNOS). Disruption of AMPK signaling, using compound C or short hairpinRNA knockdown, and eNOS inhibition using L-NIO abolished the antihypertrophic actions of CB-13. In conclusion, CB-13 inhibits cardiomyocyte hypertrophy through AMPK-eNOS signaling and may represent a novel therapeutic approach to cardioprotection.

Experimental colitis in mice is attenuated by changes in the levels of endocannabinoid metabolites induced by selective inhibition of fatty acid amide hydrolase (FAAH)

BACKGROUND AND AIMS

Pharmacological treatment and/or maintenance of remission in inflammatory bowel diseases (IBD) is currently one of the biggest challenge in the field of gastroenterology. Available therapies are mostly limited to overcoming the symptoms, but not the cause of the disease. Recently, the endocannabinoid system has been proposed as a novel target in the treatment of IBD. Here we aimed to assess the anti-inflammatory action of the novel fatty acid amide hydrolase (FAAH) inhibitor PF-3845 and its effect on the endocannabinoid and related lipid metabolism during the course of experimental colitis.

METHODS

We used two models of experimental colitis in mice (TNBS- and DSS-induced) and additionally, we employed LC/MS/MS spectrometry to determine the changes in biolipid levels in the mouse colon during inflammation.

RESULTS

We showed that the FAAH inhibitor PF-3845 reduced experimental TNBS-induced colitis in mice and its anti-inflammatory action is associated with altering the levels of selected biolipids (arachidonic and oleic acid derivatives, prostaglandins and biolipids containing glycine in the mouse colon).

CONCLUSIONS

We show that FAAH is a promising pharmacological target and the FAAH-dependent biolipids play a major role in colitis. Our results highlight and promote therapeutic strategy based on targeting FAAH-dependent metabolic pathways in order to alleviate intestinal inflammation.

Mitochondrial permeability transition pore plays a role in the cardioprotection of CB2 receptor against ischemia–reperfusion injury

The aim of this study was to investigate whether the mitochondrial permeability transition pore (MPTP) opening was involved in the protective effects of CB2 receptor against ischemia–reperfusion (I-R) injury. For this, isolated perfused rat hearts were subjected to 30 min global ischemia followed by 120 min reperfusion, and left ventricle function was recorded. At the end of reperfusion, the infarct size in the hearts was measured by staining with triphenyltetrazolium chloride. MPTP opening and the mitochondrial membrane potential (ΔΨm) were measured by flow cytometry. Western blot analysis of cytochrome c in the mitochondrion and cytosol, as well as ERK1/2 and p-ERK1/2 were performed. Administration of CB2 receptor agonist JWH133 before ischemia significantly improved the recovery of cardiac ventricular function during reperfusion, increased coronary flow, reduced infarct size, prevented the loss of ΔΨm and MPTP opening, reduced the release of cytochrome c from mitochondria, and increased levels of p-ERK1/2. These effects of JWH133 were abolished by pretreatment with CB2 receptor antagonist AM630, or ERK1/2 inhibitor PD98059. Furthermore, JWH133 reversed the MPTP opening induced by atractyloside. The protective effect of JWH133 on the heart against I-R injury may be through increased ERK1/2 phosphorylation, inhibiting MPTP opening.

Endocannabinoid system as a potential mechanism for n-3 long-chain polyunsaturated fatty acid mediated cardiovascular protection

The presence of an active and functioning endocannabinoid (EC) system within cardiovascular tissues implies that this system has either a physiological or pathophysiological role (or both), and there is a substantial literature to support the notion that, in the main, they are protective in the setting of various CVD states. Moreover, there is an equally extensive literature to demonstrate the cardio- and vasculo-protective effects of n-3 long-chain (LC)-PUFA. It is now becoming evident that there appears to be a close relationship between dietary intervention with n-3 LC-PUFA and changes in tissue levels of EC, raising the question as to whether or not EC may, at least in part, play a role in mediating the cardio-and vasculo-protective effects of n-3 LC-PUFA. This brief review summarises the current understanding of how both EC and n-3 LC-PUFA exert their protective effects in three major cardiovascular disorders (hypertension, atherosclerosis and acute myocardial infarction) and attempts to identify the similarities and differences that may indicate common or integrated mechanisms. From the data available, it is unlikely that in hypertension EC mediate any beneficial effects of n-3 LC-PUFA, since they do not share common mechanisms of blood pressure reduction. However, inhibition of inflammation is an effect shared by EC and n-3 LC-PUFA in the setting of both atherosclerosis and myocardial reperfusion injury, while blockade of L-type Ca2+ channels is one of the possible common mechanisms for their antiarrhythmic effects. Although both EC and n-3 LC-PUFA demonstrate vasculo- and cardio-protection, the literature overwhelmingly shows that n-3 LC-PUFA decrease tissue levels of EC through formation of EC–n-3 LC-PUFA conjugates, which is counter-intuitive to an argument that EC may mediate the effects of n-3 LC-PUFA. However, the discovery that these conjugates have a greater affinity for cannabinoid receptors than the native EC provides a fascinating avenue for further research into novel approaches for the treatment and prevention of atherosclerosis and myocardial injury following ischaemia/reperfusion.

Endogenous cannabinoid system regulates intestinal barrier function in vivo through cannabinoid type 1 receptor activation

The deleterious effects of stress on the gastrointestinal tract seem to be mainly mediated by the induction of intestinal barrier dysfunction and subsequent subtle mucosal inflammation. Cannabinoid 1 receptor (CB1R) is expressed in the mammalian gut under physiological circumstances. The aim of this investigation is to study the possible role of CB1R in the maintenance of mucosal homeostasis after stress exposure. CB1R knockout mice (CB1R(-/-)) and their wild-type (WT) counterparts were exposed to immobilization and acoustic (IA) stress for 2 h per day during 4 consecutive days. Colonic protein expression of the inducible forms of the nitric oxide synthase and cyclooxygenase (NOS2 and COX2), IgA production, permeability to (51)Cr-EDTA, and bacterial translocation to mesenteric lymph nodes were evaluated. Stress exposure induced greater expression of proinflammatory enzymes NOS2 and COX2 in colonic mucosa of CB1R(-/-) mice when compared with WT animals. These changes were related with a greater degree of colonic barrier dysfunction in CB1R(-/-) animals determined by 1) a significantly lower IgA secretion, 2) higher paracellular permeability to (51)Cr-EDTA, and 3) higher bacterial translocation, both under basal conditions and after IA stress exposure. Pharmacological antagonism with rimonabant reproduced stress-induced increase of proinflammatory enzymes in the colon described in CB1R(-/-) mice. In conclusion, CB1R exerts a protective role in the colon in vivo through the regulation of intestinal secretion of IgA and paracellular permeability. Pharmacological modulation of cannabinoid system within the gastrointestinal tract might be therapeutically useful in conditions on which intestinal inflammation and barrier dysfunction takes place after exposure to stress.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Regulatory role of cannabinoid receptor 1 in stress-induced excitotoxicity and neuroinflammation

Exposure to stress elicits excitoxicity and neuroinflammation in the brain, contributing to cell death and damage in stress-related neurological and neuropsychiatric diseases. The endocannabinoid system is present in stress-responsive neural circuits and has been proposed as an endogenous neuroprotective system activated in some neuropathological scenarios to restore homeostasis. To elucidate the possible regulatory role of cannabinoid receptor 1 (CB1) in stress-induced excitotoxicity and neuroinflammation, both genetic and pharmacological approaches were used alternatively: (1) wild-type (WT) and CB1 knockout mice (CB1-KO) were exposed to immobilization/acoustic stress (2 h/day for 4 days) and (2) to specifically activate CB1, the selective CB1 agonist Arachidonyl-2'-chloroethylamide (ACEA) (2.5 mg/kg) was intraperitoneally administered daily to some groups of animals. Stress exposure increased CB1 mRNA and protein expression in the prefrontal cortex of WT mice in a mechanism related to N-methyl-D-aspartate glutamate receptor activation. Daily ACEA pretreatment prevented stress-induced: (1) upregulation of CB1 mRNA and protein, (2) decrease in glutamate uptake and glutamate astroglial transporter excitatory amino acid transporter 2 expression, (3) increase in consecutive proinflammatory molecules, such as cytokines (tumor necrosis factor-α and MCP-1), nuclear factor kappa B, and enzymatic sources, such as inducible nitric oxide synthase (NOS-2) and cyclooxygenase-2 (COX-2), (4) increase in lipid peroxidation; although having no effect on plasma corticosterone. Interestingly, a possible related mechanism could be the positive ACEA modulation of the antiinflammatory pathway deoxyprostaglandin/peroxisome proliferator-activated receptor γ (15d-PGJ(2)/PPARγ). Conversely, KO animal experiments indicated that a lack of CB1 produces hypothalamic/pituitary/adrenal (HPA) axis dysregulation and exacerbates stress-induced excitotoxic/neuroinflammatory responses. These multifaceted neuroprotective effects suggest that CB1 activation could be a new therapeutic strategy against neurological/neuropsychiatric pathologies with HPA axis dysregulation and an excitotoxic/neuroinflammatory component in their pathophysiology.

Is lipid signaling through cannabinoid 2 receptors part of a protective system?

The mammalian body has a highly developed immune system which guards against continuous invading protein attacks and aims at preventing, attenuating or repairing the inflicted damage. It is conceivable that through evolution analogous biological protective systems have been evolved against non-protein attacks. There is emerging evidence that lipid endocannabinoid signaling through cannabinoid 2 (CB₂) receptors may represent an example/part of such a protective system/armamentarium. Inflammation/tissue injury triggers rapid elevations in local endocannabinoid levels, which in turn regulate signaling responses in immune and other cells modulating their critical functions. Changes in endocannabinoid levels and/or CB₂ receptor expressions have been reported in almost all diseases affecting humans, ranging from cardiovascular, gastrointestinal, liver, kidney, neurodegenerative, psychiatric, bone, skin, autoimmune, lung disorders to pain and cancer, and modulating CB₂ receptor activity holds tremendous therapeutic potential in these pathologies. While CB₂ receptor activation in general mediates immunosuppressive effects, which limit inflammation and associated tissue injury in large number of pathological conditions, in some disease states activation of the CB₂ receptor may enhance or even trigger tissue damage, which will also be discussed alongside the protective actions of the CB₂ receptor stimulation with endocannabinoids or synthetic agonists, and the possible biological mechanisms involved in these effects.

Endocannabinoid-like N-arachidonoyl serine is a novel pro-angiogenic mediator

BACKGROUND AND PURPOSE

N-arachidonoyl serine (ARA-S) is a recently identified endocannabinoid-like lipid with weak affinity for the fully characterized cannabinoid receptors (CB(1) and CB(2)) and the transient receptor potential vanilloid receptor 1 (TRPV-1). ARA-S induces vasodilatation and shows vasoprotective potential via activation of key signalling pathways in endothelial cells. Based on these findings, the effect of ARA-S on endothelial functions was further studied.

EXPERIMENTAL APPROACH

Primary human dermal microvascular endothelial cells (HMVEC) were used to investigate effects of ARA-S (0-10 microM) on certain endothelial functions, using cell proliferation, migration and wound repair models in vitro, and angiogenesis assays in vitro and ex vivo. Selective CB receptor antagonists and specific siRNAs were deployed to block individual CB receptors.

KEY RESULTS

We found that ARA-S stimulated angiogenesis and endothelial wound healing through induction of vascular endothelial growth factor C and its cognate receptor expression in primary HMVEC. Moreover, knock-down of G protein-coupled receptor 55 (GPR55) partly inhibited ARA-S-induced signal transduction and endothelial functions.

CONCLUSIONS AND IMPLICATIONS

Our results indicate that ARA-S is a pro-angiogenic factor in addition to a vessel dilator. The GPR55 receptor may serve as one target of ARA-S.

The cannabinoid receptor type 2 promotes cardiac myocyte and fibroblast survival and protects against ischemia/reperfusion-induced cardiomyopathy

Post-myocardial infarction (MI) heart failure is a major public health problem in Western countries and results from ischemia/reperfusion (IR)-induced cell death, remodeling, and contractile dysfunction. Ex vivo studies have demonstrated the cardioprotective anti-inflammatory effect of the cannabinoid type 2 (CB2) receptor agonists within hours after IR. Herein, we evaluated the in vivo effect of CB2 receptors on IR-induced cell death, fibrosis, and cardiac dysfunction and investigated the target role of cardiac myocytes and fibroblasts. The infarct size was increased 24 h after IR in CB2(-/-) vs. wild-type (WT) hearts and decreased when WT hearts were injected with the CB2 agonist JWH133 (3 mg/kg) at reperfusion. Compared with WT hearts, CB2(-/-) hearts showed widespread injury 3 d after IR, with enhanced apoptosis and remodeling affecting the remote myocardium. Finally, CB2(-/-) hearts exhibited exacerbated fibrosis, associated with left ventricular dysfunction 4 wk after IR, whereas their WT counterparts recovered normal function. Cardiac myocytes and fibroblasts isolated from CB2(-/-) hearts displayed a higher H(2)O(2)-induced death than WT cells, whereas 1 microM JWH133 triggered survival effects. Furthermore, H(2)O(2)-induced myofibroblast activation was increased in CB2(-/-) fibroblasts but decreased in 1 microM JWH133-treated WT fibroblasts, compared with that in WT cells. Therefore, CB2 receptor activation may protect against post-IR heart failure through direct inhibition of cardiac myocyte and fibroblast death and prevention of myofibroblast activation.

The preventive effect of cannabinoids on reperfusion-induced ischemia of mouse kidney

Artery occlusion of an organ results in ischemia. When the occlusion is opened and blood flow reinstated there will be tissue injuries identified as reperfusion-induced ischemia (RII). It has been suggested that cannabinoids (CBs) may be involved in the RII. In this study, we assessed the effect of different doses of anandamide analogs and CB receptor agonists: arachidonylcyclopropylamide (ACPA, a CB1 agonist) and JWH133 (a CB2 agonist) in the RII of the mouse kidney. Three doses (0.2, 1 and 5mg/kg, i.p.) of ACPA or JWH133 were used 30min prior initiation of RII. Kidneys were removed 2 and 24h following RII and checked histologically for the grading of ischemic injury. Appropriate control groups were used as well. RII produced lesion comparable with that of ischemia. Different doses of ACPA or JWH133 prevented RII-induced lesions. It is suggestive of the CB system involvement in the kidney RII in mice.

delta-Opioid receptor stimulation enhances the growth of neonatal rat ventricular myocytes via the extracellular signal-regulated kinase pathway

1. The aims of the present study were to determine whether delta-opioid receptor stimulation enhanced proliferation of and to investigate the role of the extracellular signal-regulated kinase (ERK) pathway in ventricular myocytes from neonatal rats. 2. At concentratins ranging from 10 nmol/L to 10 micromol/L, [D-Ala2,D-Leu5]enkephalin (DADLE) concentration-dependently promoted myocardial growth and DNA synthesis and altered the cytoskeleton. 3. At 1 micromol/L, DADLE also increased the expression and phosphorylation of ERK. 4. These effects of 1 micromol/L DADLE were abolished by 10 micromol/L naltrindole, a selective delta-opioid receptor antagonist, 10 nmol/L U0126, a selective ERK antagonist, 1 micromol/L staurosporine, an inhibitor of protein kinase (PK) C, and 100 micromol/L Rp-adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt hydrate (Rp-cAMPS), an inhibitor of PKA. 5. In conclusion, delta-opioid receptor stimulation enhances the proliferation and development of the ventricular myocytes of neonatal rats. The ERK pathway and related signalling mechanisms, namely PKC and PKA, are involved.

Endocannabinoids and cannabinoid receptors in ischaemia-reperfusion injury and preconditioning

Ischaemia-reperfusion (I/R) is a pivotal mechanism of organ injury during stroke, myocardial infarction, organ transplantation and vascular surgeries. Ischaemic preconditioning (IPC) is a potent endogenous form of tissue protection against I/R injury. On the one hand, endocannabinoids have been implicated in the protective effects of IPC through cannabinoid CB1/CB2 receptor-dependent and -independent mechanisms. However, there is evidence suggesting that endocannabinoids are overproduced during various forms of I/R, such as myocardial infarction or whole body I/R associated with circulatory shock, and may contribute to the cardiovascular depressive state associated with these pathologies. Previous studies using synthetic CB1 receptor agonists or knockout mice demonstrated CB1 receptor-dependent protection against cerebral I/R injury in various animal models. In contrast, several follow-up reports have shown protection afforded by CB1 receptor antagonists, but not agonists. Excitedly, emerging studies using potent CB2 receptor agonists and/or knockout mice have provided compelling evidence that CB2 receptor activation is protective against myocardial, cerebral and hepatic I/R injuries by decreasing the endothelial cell activation/inflammatory response (for example, expression of adhesion molecules, secretion of chemokines, and so on), and by attenuating the leukocyte chemotaxis, rolling, adhesion to endothelium, activation and transendothelial migration, and interrelated oxidative/nitrosative damage. This review is aimed to discuss the role of endocannabinoids and CB receptors in various forms of I/R injury (myocardial, cerebral, hepatic and circulatory shock) and preconditioning, and to delineate the evidence supporting the therapeutic utility of selective CB2 receptor agonists, which are devoid of psychoactive effects, as a promising new approach to limit I/R-induced tissue damage.

Protein kinase C as a stress sensor

While there are many reviews which examine the group of proteins known as protein kinase C (PKC), the focus of this article is to examine the cellular roles of two PKCs that are important for stress responses in neurological tissues (PKC gamma and epsilon) and in cardiac tissues (PKC epsilon). These two kinases, in particular, seem to have overlapping functions and interact with an identical target, connexin 43 (Cx43), a gap junction protein which is central to proper control of signals in both tissues. While PKC gamma and PKC epsilon both help protect neural tissue from ischemia, PKC epsilon is the primary PKC isoform responsible for responding to decreased oxygen, or ischemia, in the heart. Both do this through Cx43. It is clear that both PKC gamma and PKC epsilon are necessary for protection from ischemia. However, the importance of these kinases has been inferred from preconditioning experiments which demonstrate that brief periods of hypoxia protect neurological and cardiac tissues from future insults, and that this depends on the activation, translocation, or ability for PKC gamma and/or PKC epsilon to interact with distinct cellular targets, especially Cx43. This review summarizes the recent findings which define the roles of PKC gamma and PKC epsilon in cardiac and neurological functions and their relationships to ischemia/reperfusion injury. In addition, a biochemical comparison of PKC gamma and PKC epsilon and a proposed argument for why both forms are present in neurological tissue while only PKC epsilon is present in heart, are discussed. Finally, the biochemistry of PKCs and future directions for the field are discussed, in light of this new information.