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The pathophysiological implications of binding of urotensin II (U-II) to urotensin II receptor (UT) in pulmonary arterial hypertension (PAH) have been proposed recently. Besides high expression of U-II in experimental models and patients with PAH, U-II has been shown to increase proliferation of pulmonary vascular smooth muscle cells and inflammatory responses, which were critical for PAH pathophysiology. However, the direct role of the urotensinergic system in the pathogenesis of PAH is yet to be understood. The aim of the present study was to determine whether a novel UT antagonist, KR36676, attenuates the pathophysiological progression of PAH in an animal model of PAH. PAH was induced by a single subcutaneous injection of monocrotaline (MCT, 60mg/kg) in rats. All the animals received KR36676 (30mg/kg/day) or vehicle by oral gavage. Three weeks after MCT-injection, changes in hemodynamic parameters, extent of right ventricular hypertrophy, fibrosis and pulmonary vascular remodeling, and degree of protein expression were determined. Oral administration of KR36676 effectively decreased the MCT-induced increase in right ventricular systolic pressure, hypertrophy and fibrosis. Furthermore, wall thickness of pulmonary arterioles, proliferation of pulmonary vascular cells, and inflammatory response significantly decreased in the KR36676-treated group following MCT injection compared to that in the MCT-treated vehicle group. These preventive effects of KR36676 are mediated, at least in part, by suppression of ERK1/2 and NF-κB signaling pathways. The novel UT antagonist, KR36676, effectively prevented MCT-induced PAH progression and pulmonary vascular remodeling in rat model. Our findings support the therapeutic efficacy of UT antagonist in PAH prevention and elucidate the possible underlying mechanisms of action.

Polymyxin B is widely used antibiotic in the clinic for resistant Gram-negative infections. In addition, polymyxin B-immobilized hemoperfusion cartridge has been used for endotoxin removal therapy in patients with septic shock. The aim of this study was to investigate the anti-fibrotic and anti-cellular hypertrophic effects of polymyxin B, and further to explore its possible mechanism. Polymyxin B (3, 10 μM) significantly inhibited stress fiber formation induced by angiotensin II (Ang II) in rat heart-derived H9c2 cells. Furthermore, polymyxin B (1 - 10 μM) showed a potent inhibitory effect on Ang II-induced cellular hypertrophy in H9c2 cells. Under the mechanism study, the inhibitory activities of polymyxin B against kinases involved in cellular hypertrophy such as AKT1, CAMK, GRK5, GSK3β, MLCK, PKC, PKD2, AMPK, ROCK2, p70S6K, SGK1were evaluated. Polymyxin B possesses a potent G protein related kinase 5 (GKR5) inhibitory activity with IC50 value of 1.1 μM, and has an ATP non-competitive inhibitory mode. Taken together, these results indicate that polymyxin B alleviates Ang II-induced stress fiber formation and cellular hypertrophy, and propose that one mechanism underlying these effects involves inhibition of the GRK5 pathway.

Urotensin II and its receptor are thought to be involved in various cardiovascular diseases such as heart failure, pulmonary hypertension and atherosclerosis. Since the regulation of the urotensin II/urotensin II receptor offers a great potential for therapeutic strategies related to the treatment of cardiovascular diseases, the study of selective and potent antagonists for urotensin II receptor is more fascinating. This study was designed to determine the potential therapeutic effects of a newly developed novel urotensin II receptor antagonist, N-(1-(3-bromo-4-(piperidin-4-yloxy)benzyl)piperidin-4-yl)benzo[b]thiophene-3-carboxamide (KR-36996), in experimental models of heart failure. KR-36996 displayed a high binding affinity (Ki=4.44±0.67nM) and selectivity for urotensin II receptor. In cell-based study, KR-36996 significantly inhibited urotensin II-induced stress fiber formation and cellular hypertrophy in H9c2UT cells. In transverse aortic constriction-induced cardiac hypertrophy model in mice, the daily oral administration of KR-36996 (30mg/kg) for 14 days significantly decreased left ventricular weight by 40% (P

Mitogen-inducible gene 6 (Mig-6) is a negative feedback inhibitor of epidermal growth factor receptor (EGFR) signaling. We previously found that Mig-6 plays a critical role in the regulation of cholesterol homeostasis and in bile acid synthesis. In this study, we investigated the effects of EGFR inhibition to identify a potential new treatment target for hypercholesterolemia. We used a mouse model with conditional ablation of the Mig-6 gene in the liver (Alb(cre/+) Mig-6(f/f); Mig-6(d/d)) to effectively investigate the role of Mig-6 in the regulation of liver function. Mig-6(d/d) mice were treated with either the EGFR inhibitor gefitinib or statin for 6 weeks after administration of a high-fat or standard diet. We then compared lipid profiles and other parameters among each group of mice. After a high-fat diet, Mig-6(d/d) mice showed elevated serum levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides and glucose, characteristics resembling hypercholesterolemia in diabetic patients. We observed decreases in serum levels of lipids and glucose in high-fat-diet-fed Mig-6(d/d) mice after 6 weeks of treatment with gefitinib or statin. Furthermore gefitinib-treated mice showed significantly greater decreases in serum levels of total, HDL and LDL cholesterol compared with statin-treated mice. Taken together, these results suggest that EGFR inhibition is effective for the treatment of hypercholesterolemia in high-fat-diet-fed Mig-6(d/d) mice, and our findings provide new insights into the development of possible treatment targets for hypercholesterolemia via modulation of EGFR inhibition.