The orally active urotensin receptor antagonist, KR36676, attenuates cellular and cardiac hypertrophy.

BACKGROUND AND PURPOSE: Blockade of the actions of urotensin-II (U-II) mediated by the urotensin (UT) receptor should improve cardiac function and prevent cardiac remodelling in cardiovascular disease. Here, we have evaluated the pharmacological properties of the recently identified UT receptor antagonist, 2-(6,7-dichloro-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl)-N-methyl-N-(2-(pyrrolidin-1-yl)-1-(4-(thiophen-3-yl)phenyl) ethyl)acetamide (KR36676). EXPERIMENTAL APPROACH: Pharmacological properties of KR36676 were studied in a range of in vitro assays (receptor binding, calcium mobilization, stress fibre formation, cellular hypertrophy) and in vivo animal models such as cardiac hypertrophy induced by transverse aortic constriction (TAC) or myocardial infarction (MI). KEY RESULTS: KR36676 displayed high binding affinity for the UT receptor (Ki : 0.7 nM), similar to that of U-II (0.4 nM), and was a potent antagonist at that receptor (IC50 : 4.0 nM). U-II-induced stress fibre formation and cellular hypertrophy were significantly inhibited with low concentrations of KR36676 (≥0.01 µM). Oral administration of KR36676 (30 mg·kg(-1) ) in a TAC model in mice attenuated cardiac hypertrophy and myocardial fibrosis. Moreover, KR36676 restored cardiac function and myocyte size in rats with MI-induced cardiac hypertrophy. CONCLUSIONS AND IMPLICATIONS: A highly potent UT receptor antagonist exerted anti-hypertrophic effects not only in infarcted rat hearts but also in pressure-overloaded mouse hearts. KR36676 could be a valuable pharmacological tool in elucidating the complicated physiological role of U-II and UT receptors in cardiac hypertrophy.

A novel anti-ischemic ATP-sensitive potassium channel (K(ATP)) opener without vasorelaxation: N-(6-aminobenzopyranyl)-N'-benzyl-N' '-cyanoguanidine analogue.

This paper describes the design, synthesis, and biological evaluation of a novel anti-ischemic compound, (2S,3S,4R)-N-(6-amino-3,4-dihydro-2-dimethoxymethyl-3-hydroxy-2-methyl-2H-benzopyranyl)-N'-benzyl-N"-cyanoguanidine (33), and the structure-activity relationships leading to the discovery of this compound. Compound 33 significantly reduced the myocardial infarct zone to area at risk (IZ/AAR) in the ischemic myocardium rat model with high cardioselectivity. Since the cardioprotective effect of compound 33 is reversed by ATP-sensitive potassium channel (K(ATP)) blockers, its anti-ischemic effect appears to be at least mediated by K(ATP) opening. In addition, compound 33 shows good protective activity on neuronal cells against oxidative stress, and therefore it is suggested that compound 33 may have therapeutic potential both in cardio- and in neuroprotection.

Upstream NF-kappaB site is required for the maximal expression of mouse inducible nitric oxide synthase gene in interferon-gamma plus lipopolysaccharide-induced RAW 264.7 macrophages.

Transient transfection assays with various deletion mutants of the mouse inducible nitric oxide synthase (iNOS) promoter linked to a CAT reporter gene demonstrated that, besides the downstream NF-kappaB site, the region from -973 to -925 which contains a potential binding site for NF-kappaB (upstream NF-kappaB site) also mediated lipopolysaccharide (LPS)-inducibility in mouse macrophage cell line RAW 264.7. Site-specific mutation of three conserved nucleotides within the upstream NF-kappaB site abolished additional induction by LPS as well as maximal expression of iNOS by IFN-gamma plus LPS. In contrast, site-specific mutation of the downstream NF-kappaB site caused almost all reduction in expression of the reporter gene by LPS or LPS plus IFN-gamma. Electrophoretic mobility shift assays with the two NF-kappaB sites showed LPS-induced NF-kappaB binding to both probes and its higher affinity to the upstream NF-kappaB site. Taken together, these suggest that the upstream NF-kappaB site having enhancer function, besides the downstream NF-kappaB site as a core promoter, is essential for maximal expression of the iNOS gene.

A comparative molecular field analysis and molecular modelling studies on pyridylimidazole type of angiotensin II antagonists.

A large number of compounds known as "AII (Angiotensin II) antagonists" have been developed for the treatment of various heart diseases such as hypertension, congestive heart failure, and chronic renal failure. Most of the currently known AII receptor antagonists share a similar chemical structure, consisting of nitrogen atoms, a lipophilic alkyl side chain and an acidic group. As a new series, we have designed and synthesized various pyridylimidazole derivatives. In this report we would like to discuss the structure-activity relationship of these series of compounds using the comparative molecular field analysis (CoMFA) methods. We could come up with a good CoMFA model (cross-validated and conventional r2 values equal to 0.702 and 0.991, respectively) and the validity of the model was confirmed by synthesizing and measuring their biological activity of additional 6 compounds suggested by the model. This result provides additional information on the structural requirement for structurally diverse group of AII receptor antagonists.

Effects of KR-30035, a novel multidrug-resistance modulator, on the cardiovascular system of rats in vivo and on the cell cycle of human cancer cells in vitro.

The present study was performed to evaluate the adverse effects of KR-30035, a multidrug-resistance modulator, on the cardiovascular system in vivo, along with its effect on paclitaxel-induced cell cycle arrest in cultured cancer cells. In anesthetized rats, KR-30035 was about 10-fold less potent than verapamil in lowering blood pressure (i.v. ED20: 0.320+/-0.052 and 0.034+/-0.005 mg/kg, respectively) and in producing electrocardiogram changes. In conscious spontaneously hypertensive rats, verapamil caused a significant antihypertensive effects at the doses tested (p.o. ED20, 7.8+/-4.0 mg/kg), whereas KR-30035 did not significantly change either the blood pressure or the heart rate at any doses tested (up to 100 mg/kg). The estimated i.v. LD50 values in mice were 5.9 and 48.9 mg/kg for verapamil and KR-30035, respectively. In the presence of 10 microM KR-30035, paclitaxel (1 microM) when added to cultures of HCT15/CL02 human cancer cells greatly shifted the cell population from the G0/G1 phases towards G2/M phases (from 42.4, 30.3 and 27.3 to 14.6, 21.5 and 63.9% for the G0/G1, S and G2/M phases, respectively), with a similar magnitude to that of 10 microM verapamil (14.0, 15.7 and 70.3%, respectively). These results suggest that KR-30035 has weaker in vivo effects on the cardiovascular system compared with verapamil, while potentiating the G2/M arresting effect of paclitaxel on the cell cycle.