In this study, we reveal that leptin evokes an acute hypotensive effect in 6-hydroxydopamine sympathectomized rats (response to maximal leptin dose, mean blood pressure: from 92 +/- 4 to 78 +/- 2 mmHg, P < 0.01). This hemodynamic effect is related to a direct action of the hormone on vascular tone, since in aortic and mesenteric rings increasing doses of leptin evoke a dose-dependent vasorelaxation (aorta: from 3 +/- 1 to 36 +/- 3, n = 15; mesenteric: from 6 +/- 1 to 30 +/- 5, n = 10), which is impaired by endothelial denudation. In particular, leptin-evoked vasorelaxation is impaired by nitric oxide synthase inhibition in aorta (delta% of maximal response: from 36 +/- 3 to 3 +/- 1, P < 0.01) and by endothelium-derived hyperpolarizing factor (EDHF) inhibition in mesenteric arteries (delta% of maximal response: from 30 +/- 5 to 7 +/- 2, P < 0.01), suggesting that vasorelaxation evoked by leptin is heterogeneous and related to the vascular bed. Finally, the inhibition of nitric oxide synthase by NG-nitro-L-arginine-methyl ester does not modify blood pressure response to leptin, suggesting a predominant role of the EDHF mechanism in the hypotensive effect of leptin.

TGF-beta proteins are main regulators of blood vessel development and maintenance. Here, we report an unprecedented link between TGF-beta signaling and arterial hypertension based on the analysis of mice mutant for Emilin1, a cysteine-rich secreted glycoprotein expressed in the vascular tree. Emilin1 knockout animals display increased blood pressure, increased peripheral vascular resistance, and reduced vessel size. Mechanistically, we found that Emilin1 inhibits TGF-beta signaling by binding specifically to the proTGF-beta precursor and preventing its maturation by furin convertases in the extracellular space. In support of these findings, genetic inactivation of Emilin1 causes increased TGF-beta signaling in the vascular wall. Strikingly, high blood pressure observed in Emilin1 mutants is rescued to normal levels upon inactivation of a single TGF-beta1 allele. This study highlights the importance of modulation of TGF-beta availability in the pathogenesis of hypertension.

Pathological molecular mechanisms involved in myocardial remodeling contribute to alter the existing structure of the heart, leading to cardiac dysfunction. Among the complex signaling network that characterizes myocardial remodeling, the distinct processes are myocyte loss, cardiac hypertrophy, alteration of extracellular matrix homeostasis, fibrosis, defective autophagy, metabolic abnormalities, and mitochondrial dysfunction. Several pathophysiological stimuli, such as pressure and volume overload, trigger the remodeling cascade, a process that initially confers protection to the heart as a compensatory mechanism. Yet chronic inflammation after myocardial infarction also leads to cardiac remodeling that, when prolonged, leads to heart failure progression. Here, we review the molecular pathways involved in cardiac remodeling, with particular emphasis on those associated with myocardial infarction. A better understanding of cell signaling involved in cardiac remodeling may support the development of new therapeutic strategies towards the treatment of heart failure and reduction of cardiac complications. We will also discuss data derived from gene therapy approaches for modulating key mediators of cardiac remodeling.

Recent evidence suggests that besides its action on the central nervous system, leptin can modulate vascular tone through local mechanisms involving nitric oxide (NO) release. In this study, using a fluorescent probe for direct determination of NO, we demonstrated both in endothelial cells and in vessels that leptin is able to stimulate NO release. The effect of leptin on NO is abolished by erbstatin A, a Ca 2؉ -independent tyrosine kinase inhibitor, whereas it is not influenced by calcium removal or by other protein phosphorylation inhibitors, such as genistein (an ATP-dependent tyrosine-kinase inhibitor) or wortmannin and LY294002 (two different phosphatidylinositol [PI] 3-kinase inhibitors). Accordingly, leptin-induced vasorelaxation in aortic rings was abolished only by erbstatin A. Furthermore, immunoblotting studies revealed that leptin evokes Akt phosphorylation, with a comparable time course in both endothelial cells and vessels. Also in this experimental system, the effect of leptin was abolished by erbstatin A and not by other inhibitors. Finally, a considerable increase in endothelial NO synthase (eNOS) phosphorylation in Ser 1177 was found when vessels were treated with leptin. In conclusion, leptin induces NO production by activating a PI 3-kinase-independent Akt-eNOS phosphorylation pathway. Diabetes 51: 168 -173, 2002

To investigate the functional role of different ␣ 1 -adrenergic receptor (␣ 1 -AR) subtypes in vivo, we have applied a gene targeting approach to create a mouse model lacking the ␣ 1b -AR (␣ 1b ؊͞؊). Reverse transcription-PCR and ligand binding studies were combined to elucidate the expression of the ␣ 1 -AR subtypes in various tissues of ␣ 1b ؉͞؉ and ؊͞؊ mice. Total ␣ 1 -AR sites were decreased by 98% in liver, 74% in heart, and 42% in cerebral cortex of the ␣ 1b ؊͞؊ as compared with ؉͞؉ mice. Because of the large decrease of ␣ 1 -AR in the heart and the loss of the ␣ 1b -AR mRNA in the aorta of the ␣ 1b ؊͞؊ mice, the in vivo blood pressure and in vitro aorta contractile responses to ␣ 1 -agonists were investigated in ␣ 1b ؉͞؉ and ؊͞؊ mice. Our findings provide strong evidence that the ␣ 1b -AR is a mediator of the blood pressure and the aorta contractile responses induced by ␣ 1 agonists. This was demonstrated by the finding that the mean arterial blood pressure response to phenylephrine was decreased by 45% in ␣ 1b ؊͞؊ as compared with ؉͞؉ mice. In addition, phenylephrine-induced contractions of aortic rings also were decreased by 25% in ␣ 1b ؊͞؊ mice. The ␣ 1b -AR knockout mouse model provides a potentially useful tool to elucidate the functional specificity of different ␣ 1 -AR subtypes, to better understand the effects of adrenergic drugs, and to investigate the multiple mechanisms involved in the control of blood pressure.

Cardiac hypertrophy is an adaptive response to a variety of mechanical and hormonal stimuli, and represents an early event in the clinical course leading to heart failure. By gene inactivation, we demonstrate here a crucial role of melusin, a muscle-specific protein that interacts with the integrin beta1 cytoplasmic domain, in the hypertrophic response to mechanical overload. Melusin-null mice showed normal cardiac structure and function in physiological conditions, but when subjected to pressure overload--a condition that induces a hypertrophic response in wild-type controls--they developed an abnormal cardiac remodeling that evolved into dilated cardiomyopathy and contractile dysfunction. In contrast, the hypertrophic response was identical in wild-type and melusin-null mice after chronic administration of angiotensin II or phenylephrine at doses that do not increase blood pressure--that is, in the absence of cardiac biomechanical stress. Analysis of intracellular signaling events induced by pressure overload indicated that phosphorylation of glycogen synthase kinase-3beta (GSK-3beta) was specifically blunted in melusin-null hearts. Thus, melusin prevents cardiac dilation during chronic pressure overload by specifically sensing mechanical stress.

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Aims Sodium-glucose-cotransporter-2 inhibitors showed favourable cardiovascular outcomes, but the underlying mechanisms are still elusive. This study investigated the mechanisms of empagliflozin in human and murine heart failure with preserved ejection fraction (HFpEF). Methods and results The acute mechanisms of empagliflozin were investigated in human myocardium from patients with HFpEF and murine ZDF obese rats, which were treated in vivo. As shown with immunoblots and ELISA, empagliflozin significantly suppressed increased levels of ICAM-1, VCAM-1, TNF-α, and IL-6 in human and murine HFpEF myocardium and attenuated pathological oxidative parameters (H2O2, 3-nitrotyrosine, GSH, lipid peroxide) in both cardiomyocyte cytosol and mitochondria in addition to improved endothelial vasorelaxation. In HFpEF, we found higher oxidative stress-dependent activation of eNOS leading to PKGIα oxidation. Interestingly, immunofluorescence imaging and electron microscopy revealed that oxidized PKG1α in HFpEF appeared as dimers/polymers localized to the outer-membrane of the cardiomyocyte. Empagliflozin reduced oxidative stress/eNOS-dependent PKGIα oxidation and polymerization resulting in a higher fraction of PKGIα monomers, which translocated back to the cytosol. Consequently, diminished NO levels, sGC activity, cGMP concentration, and PKGIα activity in HFpEF increased upon empagliflozin leading to improved phosphorylation of myofilament proteins. In skinned HFpEF cardiomyocytes, empagliflozin improved cardiomyocyte stiffness in an anti-oxidative/PKGIα-dependent manner. Monovariate linear regression analysis confirmed the correlation of oxidative stress and PKGIα polymerization with increased cardiomyocyte stiffness and diastolic dysfunction of the HFpEF patients. Conclusion Empagliflozin reduces inflammatory and oxidative stress in HFpEF and thereby improves the NO–sGC–cGMP–cascade and PKGIα activity via reduced PKGIα oxidation and polymerization leading to less pathological cardiomyocyte stiffness.