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Cannabidiol (CBD) is known for its vasorelaxant (including in the human pulmonary artery), anti-proliferative and anti-inflammatory properties. The aim of our study was to examine the potential preventive effect of chronic CBD administration (10 mg/kg/day for three weeks) on monocrotaline (MCT)-induced pulmonary hypertension (PH) rats. PH was connected with elevation of right ventricular systolic pressure; right ventricle hypertrophy; lung edema; pulmonary artery remodeling; enhancement of the vasoconstrictor and decreasing vasodilatory responses; increases in plasma concentrations of tissue plasminogen activator, plasminogen activator inhibitor type 1 and leukocyte count; and a decrease in blood oxygen saturation. CBD improved all abovementioned changes induced by PH except right ventricle hypertrophy and lung edema. In addition, CBD increased lung levels of some endocannabinoids (anandamide, N -arachidonoyl glycine, linolenoyl ethanolamide, palmitoleoyl ethanolamide and eicosapentaenoyl ethanolamide but not 2-arachidonoylglycerol). CBD did not affect the cardiopulmonary system of control rats or other parameters of blood morphology in PH. Our data suggest that CBD ameliorates MCT-induced PH in rats by improving endothelial efficiency and function, normalization of hemostatic alterations and reduction of enhanced leukocyte count determined in PH. In conclusion, CBD may be a safe, promising therapeutic or adjuvant therapy agent for the treatment of human pulmonary artery hypertension.

Background: LY393558 is a combined antagonist of serotonin (5-HT) 5-HT 1B receptors and inhibitor of serotonin transporter (SERT). LY393558 reduces 5-HT-induced vasoconstriction and remodelling of rat and/or mouse pulmonary arteries. The aim of our study was to examine the effect of LY393558 on the 5-HT-stimulated vasoconstriction of human pulmonary arteries (hPAs) and to determine the underlying mechanism(s)., Methods: Vascular effects of 5-HT receptor agonists, antagonists and a SERT inhibitor were examined in organ bath studies on intralobar hPAs obtained from patients during resection of lung carcinoma., Results: Serotonin and agonists of the 5-HT 1B receptor (5-carboxamidotryptamine, 5-CT) and 5-HT 2A receptor (α-methyl-5-HT) contracted endothelium-intact hPAs in a concentration-dependent fashion. The 5-HT 1B antagonists SB224289 and GR55562 reduced responses induced by 5-HT and 5-CT and the 5-HT 2A antagonist ketanserin inhibited the effects of 5-HT and α-methyl-5-HT. Administration of the SERT inhibitor citalopram (at a concentration that failed to modify the 5-HT-induced vasoconstriction) in combination with SB224289 or GR55562 was more effective in inhibiting the response to 5-HT than the 5-HT 1B antagonists alone. LY393558 showed the greatest antagonistic effect against the vasoconstriction elicited by 5-HT, 5-CT and α-methyl-5-HT., Conclusions: LY393558 reduces the 5-HT-induced contraction antagonizing 5-HT 1B and 5-HT 2A receptors probably due to synergic interaction between SERT inhibition and 5-HT 1B receptor antagonism. Thus, it might represent a valuable future option in the pulmonary arterial hypertension therapy.

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 (KCa) 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 KCa 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.

The aim of this study was to investigate the hemodynamic effects of SKA-31, an activator of the small ( K Ca 2.x ) and intermediate ( K Ca 3.1 ) conductance calcium-activated potassium channels, and to evaluate its influence on endothelium-derived hyperpolarization (EDH)- K Ca 2.3 / K Ca 3.1 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 Ca 3.1 , K Ca 2.3 , K IR and Na + /K + -ATPase by TRAM-34, UCL1684, Ba 2+ and ouabain, respectively, reduced the potency and efficacy of the EDH-response evoked by SKA-31. The mRNA expression of eNOS, prostacyclin synthase, K Ca 2.3 , K Ca 3.1 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 Ca 2.3 / K Ca 3.1 -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 Ca 2.3 / K Ca 3.1 channels such as SKA-31 seem to be a promising avenue in pharmacotherapy of hypertension., Competing Interests: The authors declare that there are no conflicts of interest.