Enhanced function of inhibitory presynaptic cannabinoid CB1 receptors on sympathetic nerves of DOCA-salt hypertensive rats

Comparative assessment of CacyBP/SIP, β-catenin and cannabinoid receptors in the adrenals of hypertensive rats

Taking into account homeostatic disorders resulting from arterial hypertension and the key importance of CacyBP/SIP, β-catenin and endocannabinoids in the functioning of many organs, it was decided to assess the presence and distribution of CacyBP/SIP, β-catenin, CB1 and CB2 in the adrenal glands of hypertensive rats of various aetiology. The study was conducted on the adrenal glands of rats with spontaneous and renovascular hypertension. The expression of CacyBP/SIP, β-catenin, CB1 and CB2 was detected by immunohistochemistry and real-time PCR method. The results of the present study revealed both lower gene expression and immunoreactivity of CacyBP/SIP in the adrenal glands of all hypertensive groups compared to the normotensive rats. This study demonstrated a reduction in the immunoreactivity and expression of the β-catenin, CB1 and CB2 genes in the adrenals of 2K1C rats. While in SHR, the reaction showing β-catenin and CB1 was very weak or negative, and the expression of CB2 in the adrenal glands of these rats increased. The results of this study show, for the first time, marked differences in the expression of CacyBP/SIP, β-catenin and CB1 and CB2 cannabinoid receptors in the adrenal glands of rats with primary (SHR) and secondary hypertension (2K1C).

Function of Presynaptic Inhibitory Cannabinoid CB1 Receptors in Spontaneously Hypertensive Rats and Its Modification by Enhanced Endocannabinoid Tone

We studied whether the function of presynaptic inhibitory cannabinoid CB1 receptors on the sympathetic nerve fibres innervating resistance vessels is increased in spontaneously hypertensive rats (SHR) like in deoxycorticosterone (DOCA)-salt hypertension. An increase in diastolic blood pressure (DBP) was induced by electrical stimulation of the preganglionic sympathetic neurons or by phenylephrine injection in pithed SHR and normotensive Wistar-Kyoto rats (WKY). The electrically (but not the phenylephrine) induced increase in DBP was inhibited by the cannabinoid receptor agonist CP55940, similarly in both groups, and by the endocannabinoid reuptake inhibitor AM404 in SHR only. The effect of CP55940 was abolished/reduced by the CB1 receptor antagonist AM251 (in both groups) and in WKY by endocannabinoid degradation blockade, i.e., the monoacylglycerol lipase (MAGL) inhibitor MJN110 and the dual fatty acid amide hydrolase (FAAH)/MAGL inhibitor JZL195 but not the FAAH inhibitor URB597. MJN110 and JZL195 tended to enhance the effect of CP55940 in SHR. In conclusion, the function of presynaptic inhibitory CB1 receptors depends on the hypertension model. Although no differences occurred between SHR and WKY under basal experimental conditions, the CB1 receptor function was better preserved in SHR when the endocannabinoid tone was increased by the inhibition of MAGL or the endocannabinoid transporter.

Beneficial Changes in Rat Vascular Endocannabinoid System in Primary Hypertension and under Treatment with Chronic Inhibition of Fatty Acid Amide Hydrolase by URB597

Our study aimed to examine the effects of hypertension and the chronic administration of the fatty acid amide hydrolase (FAAH) inhibitor URB597 on vascular function and the endocannabinoid system in spontaneously hypertensive rats (SHR). Functional studies were performed on small mesenteric G3 arteries (sMA) and aortas isolated from SHR and normotensive Wistar Kyoto rats (WKY) treated with URB597 (1 mg/kg; twice daily for 14 days). In the aortas and sMA of SHR, endocannabinoid levels and cannabinoid CB1 receptor (CB1R) expression were elevated. The CB1R antagonist AM251 diminished the methanandamide-evoked relaxation only in the sMA of SHR and enhanced the vasoconstriction induced by phenylephrine and the thromboxane analog U46619 in sMA in SHR and WKY. In the sMA of SHR, URB597 elevated anandamide levels, improved the endothelium-dependent vasorelaxation to acetylcholine, and in the presence of AM251 reduced the vasoconstriction to phenylephrine and enhanced the vasodilatation to methanandamide, and tended to reduce hypertrophy. In the aortas, URB597 elevated endocannabinoid levels improved the endothelium-dependent vasorelaxation to acetylcholine and decreased CB1R expression. Our study showed that hypertension and chronic administration of URB597 caused local, resistance artery-specific beneficial alterations in the vascular endocannabinoid system, which may bring further advantages for therapeutic application of pharmacological inhibition of FAAH.

Vasodilatory effects of cannabidiol in human pulmonary and rat small mesenteric arteries: modification by hypertension and the potential pharmacological opportunities

Objective:

Cannabidiol (CBD) has been suggested as a potential antihypertensive drug. The aim of our study was to investigate its vasodilatory effect in isolated human pulmonary arteries (hPAs) and rat small mesenteric arteries (sMAs).

Methods:

Vascular effects of CBD were examined in hPAs obtained from patients during resection of lung carcinoma and sMAs isolated from spontaneously hypertensive (SHR); 11-deoxycorticosterone acetate (DOCA-salt) hypertensive rats or their appropriate normotensive controls using organ bath and wire myography, respectively.

Results:

CBD induced almost full concentration-dependent vasorelaxation in hPAs and rat sMAs. In hPAs, it was insensitive to antagonists of CB₁ (AM251) and CB₂ (AM630) receptors but it was reduced by endothelium denudation, cyclooxygenase inhibitors (indomethacin and nimesulide), antagonists of prostanoid EP₄ (L161982), IP (Cay10441), vanilloid TRPV1 (capsazepine) receptors and was less potent under KCl-induced tone and calcium-activated potassium channel (K_Ca) inhibitors (iberiotoxin, UCL1684 and TRAM-34) and in hypertensive, overweight and hypercholesteremic patients. The time-dependent effect of CBD was sensitive to the PPARγ receptor antagonist GW9662. In rats, the CBD potency was enhanced in DOCA-salt and attenuated in SHR. The CBD-induced relaxation was inhibited in SHR and DOCA-salt by AM251 and only in DOCA-salt by AM630 and endothelium denudation.

Conclusion:

The CBD-induced relaxation in hPAs that was reduced in hypertensive, obese and hypercholesteremic patients was endothelium-dependent and mediated via K_Ca and IP, EP₄, TRPV1 receptors. The CBD effect in rats was CB₁-sensitive and dependent on the hypertension model. Thus, modification of CBD-mediated responses in disease should be considered when CBD is used for therapeutic purposes.

Blood endocannabinoid levels in patients with panic disorder

BACKGROUND

The development and maintenance of anxiety disorders is not fully understood. There is consensus in the literature that in addition to genetic factors, social, psychological and neurobiological factors are of crucial importance. The present exploratory study investigates the influence of the endocannabinoids (EC) and related N-acylethanolamines (NA) on the maintenance of panic disorder (PD).

METHODS

A total of n = 36 PD and n = 26 healthy controls (HC) were included in the study. Baseline characteristics showed no differences between the two groups. The participants were exposed to the Trier Social Stress Test (TSST) for reliable laboratory stress induction. Blood samples were taken during the TSST by an intravenous catheter to examine the endocannabinoid (EC) stress response. Repeated measures ANOVA was conducted to test for main effects of time and group as well as the respective interaction.

RESULTS

Participants with PD consistently had significantly higher EC and NA blood levels than HC. The consistently high EC and NA levels barely showed any reactivity as indicated by a lack of statistical variance. In line with these findings no reaction to the psychosocial stressor TSST could be detected.

CONCLUSION

Our main results show significant differences in EC concentrations between participants with PD and HC. These findings suggest that an imbalance in the ECS contributes to the maintenance of PD. Increased endocannabinoid levels may have important implications for organic diseases such as cardiovascular disorders. The limitations of the study as well as implications for further investigations are discussed.

Modulation of Cardiovascular Function in Primary Hypertension in Rat by SKA-31, an Activator of KCa2.x and KCa3.1 Channels

The aim of this study was to investigate the hemodynamic effects of SKA-31, an activator of the small (K_Ca2.x) and intermediate (K_Ca3.1) conductance calcium-activated potassium channels, and to evaluate its influence on endothelium-derived hyperpolarization (EDH)-K_Ca2.3/K_Ca3.1 type relaxation in isolated endothelium-intact small mesenteric arteries (sMAs) from spontaneously hypertensive rats (SHRs). Functional in vivo and in vitro experiments were performed on SHRs or their normotensive controls, Wistar-Kyoto rats (WKY). SKA-31 (1, 3 and 10 mg/kg) caused a brief decrease in blood pressure and bradycardia in both SHR and WKY rats. In phenylephrine-pre-constricted sMAs of SHRs, SKA-31 (0.01–10 µM)-mediated relaxation was reduced and SKA-31 potentiated acetylcholine-evoked endothelium-dependent relaxation. Endothelium denudation and inhibition of nitric oxide synthase (eNOS) and cyclooxygenase (COX) by the respective inhibitors l-NAME or indomethacin, attenuated SKA-31-mediated vasorelaxation. The inhibition of K_Ca3.1, K_Ca2.3, K_IR and Na⁺/K⁺-ATPase by TRAM-34, UCL1684, Ba²⁺ and ouabain, respectively, reduced the potency and efficacy of the EDH-response evoked by SKA-31. The mRNA expression of eNOS, prostacyclin synthase, K_Ca2.3, K_Ca3.1 and K_IR were decreased, while Na⁺/K⁺-ATPase expression was increased. Collectively, SKA-31 promoted hypotension and vasodilatation, potentiated agonist-stimulated vasodilation, and maintained K_Ca2.3/K_Ca3.1-EDH-response in sMAs of SHR with downstream signaling that involved K_IR and Na⁺/K⁺-ATPase channels. In view of the importance of the dysfunction of endothelium-mediated vasodilatation in the mechanism of hypertension, application of activators of K_Ca2.3/K_Ca3.1 channels such as SKA-31 seem to be a promising avenue in pharmacotherapy of hypertension.

Cannabinoids in arterial, pulmonary and portal hypertension - mechanisms of action and potential therapeutic significance

The endocannabinoid system is overactivated in arterial, pulmonary and portal hypertension. In this paper, we present limited clinical data concerning the role of cannabinoids in human hypertension including polymorphism of endocannabinoid system components. We underline differences between the acute cannabinoid administration and their potential hypotensive effect after chronic application in experimental hypertension. We discuss pleiotropic effects of cannabinoids on the cardiovascular system mediated via numerous neuronal and non‐neuronal mechanisms both in normotension and in hypertension. The final results are dependent on the model of hypertension, age, sex, the cannabinoid ligands used or the action via endocannabinoid metabolites. More experimental and clinical studies are needed to clarify the role of endocannabinoids in hypertension, not only in the search for new therapeutic strategies but also in the context of cardiovascular effects of cannabinoids and the steadily increasing legalization of cannabis use for recreational and medical purposes.

Linked Articles

This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc

Hypertension and chronic inhibition of endocannabinoid degradation modify the endocannabinoid system and redox balance in rat heart and plasma

The interaction between the endocannabinoid and ROS signaling systems has been demonstrated in different organs. Inhibitors of fatty acid amide hydrolase (FAAH), the key enzyme responsible for degradation of the endocannabinoid anandamide, are postulated to possess anti-hypertensive potential. Here, we compared the effects of hypertension and chronic FAAH inhibition by URB597 on the endocannabinoid system and redox balance in spontaneously hypertensive rats (SHR) and hypertensive deoxycorticosterone acetate (DOCA)-salt rats. Enhanced oxidative stress and lipid peroxidation were found in both hypertension models. Hypertension affected cardiac and plasma endocannabinoid systems in a model-dependent manner: anandamide and 2-arachidonoylglycerol levels decreased in SHR and increased in DOCA-salt. Cardiac CB₁ receptor expression increased in both models while higher CB₂ receptor expression was only in DOCA-salt. URB597 increased endocannabinoid levels in both models but produced the partial reduction of oxidative stress in DOCA-salt but not in SHR. Notably, URB597 decreased antioxidant defense and increased lipid peroxidation products in normotension. Therefore, the therapeutic potential of FAAH inhibitors should be interpreted cautiously.

The endocannabinoid system in cardiovascular function: novel insights and clinical implications

RATIONALE

Cardiovascular disease is now recognized as the number one cause of death in the world, and the size of the population at risk continues to increase rapidly. The dysregulation of the endocannabinoid (eCB) system plays a central role in a wide variety of conditions including cardiovascular disorders. Cannabinoid receptors, their endogenous ligands, as well as enzymes conferring their synthesis and degradation, exhibit overlapping distributions in the cardiovascular system. Furthermore, the pharmacological manipulation of the eCB system has effects on blood pressure, cardiac contractility, and endothelial vasomotor control. Growing evidence from animal studies supports the significance of the eCB system in cardiovascular disorders.

OBJECTIVE

To summarize the literature surrounding the eCB system in cardiovascular function and disease and the new compounds that may potentially extend the range of available interventions.

RESULTS

Drugs targeting CB1R, CB2R, TRPV1 and PPARs are proven effective in animal models mimicking cardiovascular disorders such as hypertension, atherosclerosis and myocardial infarction. Despite the setback of two clinical trials that exhibited unexpected harmful side-effects, preclinical studies are accelerating the development of more selective drugs with promising results devoid of adverse effects.

CONCLUSION

Over the last years, increasing evidence from basic and clinical research supports the role of the eCB system in cardiovascular function. Whereas new discoveries are paving the way for the identification of novel drugs and therapeutic targets, the close cooperation of researchers, clinicians and pharmaceutical companies is needed to achieve successful outcomes.

Chronic inhibition of fatty acid amide hydrolase by URB597 produces differential effects on cardiac performance in normotensive and hypertensive rats

BACKGROUND AND PURPOSE

Fatty acid amide hydrolase (FAAH) inhibitors are postulated to possess anti-hypertensive potential, because their acute injection decreases BP in spontaneously hypertensive rats (SHR), partly through normalization of cardiac contractile function. Here, we examined whether the potential hypotensive effect of chronic FAAH inhibition by URB597 in hypertensive rats correlated with changes in cardiac performance.

EXPERIMENTAL APPROACH

Experiments were performed using perfused hearts and left atria isolated from 8- to 10-week-old SHR, age-matched deoxycorticosterone acetate (DOCA)-salt rats and normotensive controls chronically treated with URB597 (1 mg·kg^-1 ) or vehicle.

KEY RESULTS

URB597 decreased BP only in the DOCA-salt rats, along with a reduction of ventricular hypertrophy and diastolic stiffness, determined in hypertension. We also observed normalization of the negative inotropic atrial response to the cannabinoid receptor agonist CP55940. In the SHR model, URB597 normalized (atria) and enhanced (hearts) the positive ino- and chronotropic effects of the β-adrenoceptor agonist isoprenaline respectively. Ventricular CB₁ and CB₂ receptor expression was decreased only in the DOCA-salt model, whereas FAAH expression was reduced in both models. URB597 caused translocation of CB₁ receptor immunoreactivity to the intercalated discs in the hearts of SHR. URB597 increased cardiac diastolic stiffness and modified the ino- and lusitropic effects of isoprenaline in normotensive rats.

CONCLUSION AND IMPLICATIONS

Hypotensive effect of chronic FAAH inhibition depend on the model of hypertension and partly correlate with improved cardiac performance. In normotensive rats, chronic FAAH inhibition produced several side-effects. Thus, the therapeutic potential of these agents should be interpreted cautiously.

From apelin to exercise: emerging therapies for management of hypertension in pregnancy

Studies over the last couple of decades have provided exciting new insights into mechanisms underlying the pathogenesis of preeclampsia. In addition, several novel and innovative molecules and ideas for management of the syndrome have also come forth. While our basic understanding of the initiating events of preeclampsia continues to be placental ischemia/hypoxia stimulating the release of a variety of factors from the placenta that act on the cardiovascular and renal systems, the number of candidate pathways for intervention continues to increase. Recent studies have identified apelin and its receptor, APJ, as an important contributor to the regulation of cardiovascular and fluid balance that is found to be disrupted in preeclampsia. Likewise, continued studies have revealed a critical role for the complement arm of the innate immune system in placental ischemia induced hypertension and in preeclampsia. Finally, the recent increase in animal models for studying hypertensive disorders of pregnancy has provided opportunities to evaluate the potential role for physical activity and exercise in a more mechanistic fashion. While the exact quantitative importance of the various endothelial and humoral factors that mediate vasoconstriction and elevation of arterial pressure during preeclampsia remains unclear, significant progress has been made. Thus, the goal of this review is to discuss recent efforts towards identifying therapies for hypertension during pregnancy that derive from work exploring the apelinergic system, the complement system as well as the role that exercise and physical activity may play to that end.

Protective role of cannabinoid CB1 receptors and vascular effects of chronic administration of FAAH inhibitor URB597 in DOCA-salt hypertensive rats

AIMS

This study examined whether the fall in blood pressure (BP) induced by the chronic inhibition of fatty acid amide hydrolase (FAAH) by URB597 in deoxycorticosterone acetate (DOCA-salt) hypertensive rats correlates with endocannabinoid-mediated vascular changes.

MAIN METHODS

Functional studies were performed in isolated endothelium-intact aortas and small mesenteric arteries (sMAs) using organ bath technique and wire myography, respectively.

KEY FINDINGS

In the DOCA-salt rats, methanandamide-stimulated relaxation was enhanced in sMAs or diminished in aortas. Its vasorelaxant effect in sMAs was sensitive to the antagonist of the Transient Receptor Potential Vanilloid type 1 (TRPV1), capsazepine, in normo- and hypertensive animals and to the antagonist of the cannabinoid CB1 receptors, AM6545, only in DOCA-salt rats. Cannabinoid CB1 receptors were up-regulated merely in DOCA-salt sMAs. URB597 decreased elevated BP in DOCA-salt rats, medial hypertrophy in DOCA-salt aortas. In sMAs it reduced FAAH expression and restored the augmented phenylephrine-induced contraction in the DOCA-salt rats to the level obtained in normotensive controls. In normotensive rats it diminished endothelium-dependent relaxation and increased phenylephrine-induced contraction.

SIGNIFICANCE

The study showed the protective role of cannabinoid CB1 receptors in DOCA-salt sMAs. Reduction in BP after chronic administration of the FAAH inhibitor URB597 in DOCA-salt hypertensive rats only partially correlates with structural and functional changes in conductance and resistance vessels, respectively. Caution should be taken in studying cannabinoids and FAAH inhibitors as potential therapeutics, because of their vessel- and model-specific activities, and side effects connected with off-target response and activation of alternative pathways of anandamide metabolism.