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Background: Apelin and its cognate G protein-coupled receptor, APJ, constitute a signaling pathway with a positive inotropic effect on cardiac function. Recently, we and other investigators demonstrated that a reduction in myocardial apelin/APJ expression might play a critical role in experimental models of end-stage heart failure (HF). Therefore, we evaluated whether exogenous apelin infusion restores apelin/APJ expression and improves cardiac function in the failing heart of Dahl salt-sensitive hypertensive (DS) rats., Methods and Results: High salt-loaded DS rats were treated with vehicle and pyroglutamylated apelin-13 (Pyr-AP13; 200µg·kg(-1)·day(-1), IP) from the age of 11 to 18 weeks. Decreased end-systolic elastance and percent fractional shortening in failing rats was significantly ameliorated by Pyr-AP13. Pyr-AP13 effectively inhibited vascular lesion formation and suppressed expression of inflammation factors such as tumor necrosis factor-α and interleukin-1β protein. Downregulation of apelin and APJ expression, and phosphorylation of endothelial nitric oxide synthase at Ser(1177) and Akt at Ser(473) in failing rats was significantly increased by Pyr-AP13. Upregulation of NAD(P)H oxidase p22(phox), p47(phox), and gp91(phox) in DS rats was significantly suppressed by Pyr-AP13., Conclusions: Exogenous apelin-13 may ameliorate cardiac dysfunction and remodeling and restore apelin/APJ expression in DS rats with end-stage HF. Thus, apelin-13 may have significant therapeutic potential for end-stage HF.

Aim: Rho-kinase plays a critical role in various cellular functions. p38 mitogen-activated protein kinase (p38 MAPK) plays a central role in the inflammatory cytokine response to immune challenge. We evaluated the effects of a combination of fasudil, a Rho-kinase inhibitor, and FR167653, a p38 MAPK inhibitor, on cardiovascular remodeling, inflammation, and oxidative stress in Dahl salt-sensitive hypertensive (DS) rats., Methods: DS and Dahl salt-resistant (DR) rats were fed a high-salt diet at 6 weeks of age. Vehicle, fasudil (100 mg/kg per day), FR167653 (2 mg/kg per day), and a combination of fasudil and FR167653 were administered to 6-week-old DS rats for 5 weeks., Results: At the age of 11 weeks, in the left ventricle, DS rats were characterized by increased myocardial fibrosis, phosphorylation of p38 MAPK, and myosin phosphatase targeting subunit (MYPT-1), and NAD(P)H oxidase p22(phox), p47(phox), gp91(phox), tumor necrosis factor-α and interleukin-1β expression compared with DR rats. Fasudil improved cardiovascular remodeling, inflammation, NAD(P)H oxidase subunits, and phosphorylation of p38 MAPK and MYPT-1. FR167653 also similarly ameliorated these indices but not MYPT-1 phosphorylation. Compared with either agent alone, a combination of fasudil and FR167653 was more effective for the improvement of myocardial damage, inflammation and oxidative stress., Conclusion: These findings suggest that the Rho-kinase and p38 MAPK pathways may play a pivotal role in ventricular hypertrophy; thus, we obtained the first evidence that a combination of Rho-kinase inhibitor and p38 MAPK inhibitor may provide a potential therapeutic target in hypertension with cardiovascular remodeling.

Apelin and its cognate G protein-coupled receptor APJ constitute a signaling pathway with a positive inotropic effect on cardiac function, and the apelin/APJ pathway seems to have opposing physiological role to the renin-angiotensin system. We investigated whether angiotensin II receptor blocker olmesartan could improve cardiac function associated with apelin/APJ and Akt/endothelial nitric oxide synthase (eNOS) pathway in Dahl salt-sensitive hypertensive (DS) rats with end-stage heart failure using NOS inhibitor L-N(G)-nitroarginine methyl ester (L-NAME). High salt-loaded DS rats were treated with (1) vehicle, (2) olmesartan, and (3) olmesartan plus L-NAME for 7 weeks. Decreased end-systolic elastance and percent fractional shortening in failing rats were significantly ameliorated by olmesartan. Increased atherosclerosis and vascular remodeling and fibrosis factors such as procollagen type I and III and fibronectin expression in DS rats were inhibited by olmesartan. Downregulation of apelin and APJ expression and phosphorylation of Akt and eNOS in failing rats were significantly increased by olmesartan. In addition,administration of L-NAME completely abrogated the olmesartan-mediated improvement of cardiac function and remodeling, and apelin/APJ expression and Akt/eNOS phosphorylation. These findings suggest that olmesartan may improve cardiac dysfunction and remodeling associated with apelin/APJ and Akt/eNOS pathway in DS rats with end-stage heart failure.