We studied the effects of 3‐(5′‐hydroxymethyl‐2′furyl)‐1‐benzyl indazole (YC‐1) on the activity of purified soluble guanylyl cyclase (sGC), the formation of guanosine‐3′: 5′cyclic monophosphate (cyclic GMP) in vascular smooth muscle cells (VSMC), and on the tone of rabbit isolated aortic rings preconstricted by phenylephrine (PE). In addition, we assessed the combined effect of YC‐1, and either NO donors, or superoxide anions on these parameters. YC‐1 elicited a direct concentration‐dependent activation of sGC (EC50 18.6 ± 2.0 μm), which was rapid in onset and quickly reversible upon dilution. YC‐1 altered the enzyme kinetics with respect to GTP by decreasing Km and increasing Vmax. Activation of sGC by a combination of sodium nitroprusside (SNP) and YC‐1 was superadditive at low and less than additive at high concentrations, indicating a synergistic activation of the enzyme by both agents. A specific inhibitor of sGC, 1H‐(1,2,4)‐oxdiazolo‐(4,3‐a)‐6‐bromo‐quinoxazin‐l‐one (NS 2028), abolished activation of the enzyme by either compound. YC‐1 induced a concentration‐dependent increase in intracellular cyclic GMP levels in rat cultured aortic VSMC, which was completely inhibited by NS 2028. YC‐1 applied at the same concentration as SNP elicited 2.5 fold higher cyclic GMP formation. Cyclic GMP‐increases in response to SNP and YC‐1 were additive. YC‐1 relaxed preconstricted endothelium‐denuded rabbit aortic rings in a concentration‐dependent manner (50% at 20 μM) and markedly increased cyclic GMP levels. Relaxations were inhibited by NS 2028. A concentration of YC‐1 (3 μm), which elicited only minor effects on relaxation and cyclic GMP, increased the vasodilator potency of SNP and nitroglycerin (NTG) by 10 fold and markedly enhanced SNP‐and NTG‐induced cyclic GMP formation. Basal and YC‐1‐stimulated sGC activity was sensitive to inhibition by superoxide (O2−) generated by xanthine/xanthine oxidase, and was protected from this inhibition by superoxide dismutase (SOD). YC‐1‐stimulated sGC was also sensitive to inhibition by endogenously generated (O2− in rat preconstricted endothelium‐denuded aortic rings. Relaxation to YC‐1 was significantly attenuated in aortae from spontaneously hypertensive rats (SHR), which generated O2− at a higher rate than aortae from normotensive Wistar Kyoto rats (WKY). SOD restored the vasodilator responsiveness of SHR rings to YC‐1. In conclusion, these results indicate that YC‐1 is an NO‐independent, O2−‐sensitive, direct activator of sGC in VSMC and exerts vasorelaxation by increasing intracellular cyclic GMP levels. The additive or even synergistic responses to NO‐donors and YC‐1 in cultured VSMC and isolated aortic rings apparently reflect the direct synergistic action of YC‐1 and NO on the sGC. The synergism revealed in this in vitro study suggests that low doses of YC‐1 may be of therapeutic value by permitting the reduction of nitrovasodilator dosage.

Background and purpose: Cysteinyl leukotrienes (CysLTs) have been implicated in the pathophysiology of inflammatory and cardiovascular disorders. Their actions are mediated by CysLT1 and CysLT2 receptors. Here we report the discovery of 3-({[(1S,3S)-3-carboxycyclohexyl]amino}carbonyl)-4-(3-{4-[4-(cyclo-hexyloxy)butoxy]phenyl}propoxy) benzoic acid (HAMI3379), the first potent and selective CysLT2 receptor antagonist. Experimental approach: Pharmacological characterization of HAMI3379 was performed using stably transfected CysLT1 and CysLT2 receptor cell lines, and isolated, Langendorff-perfused, guinea pig hearts. Key results: In a CysLT2 receptor reporter cell line, HAMI3379 antagonized leukotriene D4-(LTD4-) and leukotriene C4-(LTC4-) induced intracellular calcium mobilization with IC50 values of 3.8 nM and 4.4 nM respectively. In contrast, HAMI3379 exhibited very low potency on a recombinant CysLT1 receptor cell line (IC50 > 10 000 nM). In addition, HAMI3379 did not exhibit any agonistic activity on both CysLT receptor cell lines. In binding studies using membranes from the CysLT2 and CysLT1 receptor cell lines, HAMI3379 inhibited [ 3 H]-LTD4 binding with IC50 values of 38 nM and >10 000 nM respectively. In isolated Langendorff-perfused guinea pig hearts HAMI3379 concentration-dependently inhibited and reversed the LTC4-induced perfusion pressure increase and contractility decrease. The selective CysLT1 receptor antagonist zafirlukast was found to be inactive in this experimental setting. Conclusions and implications: HAMI3379 was identified as a potent and selective CysLT2 receptor antagonist, which was devoid of CysLT receptor agonism. Using this compound, we showed that the cardiac effects of CysLTs are predominantly mediated by the CysLT2 receptor.

Sildenafil prevents myocardial remodelling in pulmonary hypertension through an indirect action via right-ventricular unloading.

Background and purpose: Rho-kinase (ROCK) has been implicated in the pathophysiology of altered vasoregulation leading to hypertension. Here we describe the pharmacological characterization of a potent, highly selective and orally active ROCK inhibitor, the derivative of a class of azaindoles, azaindole 1 (6-chloro-Experimental approach: Pharmacological characterization of azaindole 1 was performed with human recombinant ROCK in vitro. Vasodilator activity was determined using isolated vessels in vitro and different animal models in vivo. Key results: This compound inhibited the ROCK-1 and ROCK-2 isoenzymes with IC 50 s of 0.6 and 1.1 nM in an ATPcompetitive manner. Although ATP-competitive, azaindole 1 was inactive against 89 kinases (IC 50 410 mM) and showed only weak activity against an additional 21 different kinases (IC 50 ¼ 1 -10 mM). Only the kinases TRK und FLT3 were inhibited by azaindole 1 in the sub-micromolar range, albeit with IC 50 values of 252 and 303 nM, respectively. In vivo, azaindole 1 lowered blood pressure dose-dependently after i.v. administration in anaesthetized normotensive rats. In conscious normotensive and spontaneously hypertensive rats azaindole 1 induced a dose-dependent decrease in blood pressure after oral administration without inducing a significant reflex increase in heart rate. In anaesthetized dogs, azaindole 1 induced vasodilatation with a moderately elevated heart rate. Conclusions and implications: Azaindole 1 is representative of a new class of selective and potent ROCK inhibitors and is a valuable tool for the elucidation of the role of ROCK in the cardiovascular system.

Adenosine is known to be released under a variety of physiological and pathophysiological conditions to facilitate the protection and regeneration of injured ischemic tissues. The activation of myocardial adenosine A receptors (A Rs) has been shown to inhibit myocardial pathologies associated with ischemia and reperfusion injury, suggesting several options for new cardiovascular therapies. When full A R agonists are used, the desired protective and regenerative cardiovascular effects are usually overshadowed by unintended pharmacological effects such as induction of bradycardia, atrioventricular (AV) blocks, and sedation. These unwanted effects can be overcome by using partial A R agonists. Starting from previously reported capadenoson we evaluated options to tailor A R agonists to a specific partiality range, thereby optimizing the therapeutic window. This led to the identification of the potent and selective agonist neladenoson, which shows the desired partial response on the A R, resulting in cardioprotection without sedative effects or cardiac AV blocks. To circumvent solubility and formulation issues for neladenoson, a prodrug approach was pursued. The dipeptide ester neladenoson bialanate hydrochloride showed significantly improved solubility and exposure after oral administration. Neladenoson bialanate hydrochloride is currently being evaluated in clinical trials for the treatment of heart failure.