P. Mendes-Ferreira

Therapeutic potential of neuregulin-1 in cardiovascular disease

Neuregulin-1 (NRG-1)/ErbB signaling has an indispensable role in cardiac development and in the maintenance of the structural and functional integrity of the human adult heart in health and disease. Several animal studies have now demonstrated the therapeutic effects of NRG-1 during acute cardiac injury and during chronic heart failure, with improvements in cardiac performance and animal survival. Phase I and II clinical trials for chronic heart failure in humans are now in progress.

Neuregulin-1 improves right ventricular function and attenuates experimental pulmonary arterial hypertension

AIMS Pulmonary arterial hypertension (PAH) is a serious disease that affects both the pulmonary vasculature and the right ventricle (RV). Current treatment options are insufficient. The cardiac neuregulin (NRG)-1/ErbB system is deregulated during heart failure, and treatment with recombinant human NRG-1 (rhNRG-1) has been shown to be beneficial in animal models and in patients with left ventricular (LV) dysfunction. This study aimed to evaluate the effects of rhNRG-1 in RV function and pulmonary vasculature in monocrotaline (MCT)-induced PAH and RV hypertrophy (RVH). METHODS AND RESULTS Male wistar rats (7- to 8-weeks old, n = 78) were injected with MCT (60 mg/kg, s.c.) or saline and treated with rhNRG-1 (40 µg/kg/day) or vehicle for 1 week, starting 2 weeks after MCT administration. Another set of animals was submitted to pulmonary artery banding (PAB) or sham surgery, and followed the same protocol. MCT administration resulted in the development of PAH, pulmonary arterial and RV remodelling, and dysfunction, and increased RV markers of cardiac damage. Treatment with rhNRG-1 attenuated RVH, improved RV function, and decreased RV expression of disease markers. Moreover, rhNRG-1 decreased pulmonary vascular remodelling and attenuated MCT-induced endothelial dysfunction. The anti-remodelling effects of rhNRG-1 were confirmed in the PAB model, where rhNRG-1 treatment was able to attenuate PAB-induced RVH. CONCLUSION rhNRG-1 treatment attenuates pulmonary arterial and RV remodelling, and dysfunction in a rat model of MCT-induced PAH and has direct anti-remodelling effects on the pressure-overloaded RV.

Myocardial and anti‐inflammatory effects of chronic bosentan therapy in monocrotaline‐induced pulmonary hypertension

INTRODUCTION AND OBJECTIVES Endothelin-1 antagonists are increasingly used in the treatment of pulmonary hypertension despite the lack of knowledge of their myocardial and systemic effects. We assessed the right ventricular myocardial and systemic effects of endothelin-1 antagonists in monocrotaline-induced pulmonary hypertension. METHODS Male Wistar rats (180-200 g, n=57) randomly received 60 mg/kg monocrotaline or vehicle subcutaneously. Two days later, bosentan was randomly started (300 mg/kg/day) by oral route in a subgroup of monocrotaline-injected rats, while the other monocrotaline-injected and control rats received vehicle. At 25-30 days, invasive hemodynamic assessment was performed under anesthesia, arterial blood samples were collected for gas analysis and plasma was extracted for quantification of endothelin-1, cytokines, nitrates and 6-keto-prostaglandin F1α. Right ventricular myocardium was collected for assessment of cyclooxygenase and nitric oxide synthase activity and gene expression. RESULTS The monocrotaline group developed pulmonary hypertension, low cardiac output, right ventricular hypertrophy and dilation, changes in gene expression and inflammatory activation that were attenuated in the group treated with bosentan. From a functional point of view, this group had improved right ventricular function and preserved ventriculo-vascular coupling, without deterioration in arterial gas parameters or systemic hypotension. In molecular terms, they showed reduced endothelin-1 and cytokine levels, decreased right ventricular inducible nitric oxide synthase and cyclooxygenase-2 activity and increased nitrate plasma levels compared with the non-treated group. CONCLUSIONS In this study we demonstrate that besides attenuating pulmonary hypertension, bosentan has beneficial hemodynamic, myocardial and anti-inflammatory effects.

Pulmonary arterial hypertension: Basic knowledge for clinicians.

Pulmonary arterial hypertension is a progressive syndrome based on diverse aetiologies, which is characterized by a persistent increase in pulmonary vascular resistance and overload of the right ventricle, leading to heart failure and death. Currently, none of the available treatments is able to cure pulmonary arterial hypertension; additional research is therefore needed to unravel the associated pathophysiological mechanisms. This review summarizes current knowledge related to this disorder, and the several experimental animal models that can mimic pulmonary arterial hypertension and are available for translational research.

Distinct right ventricle remodeling in response to pressure overload in the rat.

Pulmonary arterial hypertension (PAH), the most serious chronic disorder of the pulmonary circulation, is characterized by pulmonary vasoconstriction and remodeling, resulting in increased afterload on the right ventricle (RV). In fact, RV function is the main determinant of prognosis in PAH. The most frequently used experimental models of PAH include monocrotaline- and chronic hypoxia-induced PAH, which primarily affect the pulmonary circulation. Alternatively, pulmonary artery banding (PAB) can be performed to achieve RV overload without affecting the pulmonary vasculature, allowing researchers to determine the RV-specific effects of their drugs/interventions. In this work, using two different degrees of pulmonary artery constriction, we characterize, in full detail, PAB-induced adaptive and maladaptive remodeling of the RV at 3 wk after PAB surgery. Our results show that application of a mild constriction resulted in adaptive hypertrophy of the RV, with preserved systolic and diastolic function, while application of a severe constriction resulted in maladaptive hypertrophy, with chamber dilation and systolic and diastolic dysfunction up to the isolated cardiomyocyte level. By applying two different degrees of constriction, we describe, for the first time, a reliable and short-duration PAB model in which RV adaptation can be distinguished at 3 wk after surgery. We characterize, in full detail, structural and functional changes of the RV in its response to moderate and severe constriction, allowing researchers to better study RV physiology and transition to dysfunction and failure, as well as to determine the effects of new therapies.

Loss of KCNK3 is a hallmark of RV hypertrophy/dysfunction associated with pulmonary hypertension

Aims Mutations in the KCNK3 gene, which encodes for an outward-rectifier K+ channel, have been identified in patients suffering from pulmonary arterial hypertension (PAH), and constitute the first described channelopathy in PAH. In human PAH and experimental pulmonary hypertension (PH), we demonstrated that KCNK3 expression and function are severely reduced in pulmonary vascular cells, promoting PH-like phenotype at the morphologic and haemodynamic levels. Since KCNK3 channel is also expressed in both the human and rodent heart, we aimed to elucidate the pathophysiological role of KCNK3 channel in right ventricular (RV) hypertrophy (RVH) related to PH. Methods and results Using whole-cell Patch-clamp technique, we demonstrated that KCNK3 is predominantly expressed in adult rat RV cardiomyocytes compared to the left ventricle cardiomyocytes and participates in the repolarizing phase of the RV action potential. We revealed a reduction in KCNK3 function prior to development of RVH and the rise of pulmonary vascular resistance. KCNK3 function is severely reduced in RV cardiomyocytes during the development of RVH in several rat models of PH (exposure to monocrotaline, chronic hypoxia, and Sugen/hypoxia) and chronic RV pressure overload (pulmonary artery banding). In experimental PH, we revealed a reduction in KCNK3 function before any rise in pulmonary vascular resistance and the development of RVH. KCNK3 mRNA level is also reduced in human RV tissues from PAH patients compared to non-PAH patients. In line with these findings, chronic inhibition of KCNK3 in rats with the specific inhibitor (A293) induces RV hypertrophy which is associated with the re-expression of foetal genes, RV fibrosis, RV inflammation, and subsequent loss of RV performance as assessed by echocardiography. Conclusion Our data indicate that loss of KCNK3 function and expression is a hallmark of the RV hypertrophy/dysfunction associated with PH.

Urocortin-2 improves right ventricular function and attenuates pulmonary arterial hypertension

Aims Pulmonary arterial hypertension (PAH) is a devastating disease and treatment options are limited. Urocortin-2 (Ucn-2) has shown promising therapeutic effects in experimental and clinical left ventricular heart failure (HF). Our aim was to analyse the expression of Ucn-2 in human and experimental PAH, and to investigate the effects of human Ucn-2 (hUcn-2) administration in rats with monocrotaline (MCT)-induced pulmonary hypertension (PH). Methods and results Tissue samples were collected from patients with and without PAH and from rats with MCT-induced PH. hUcn-2 (5 μg/kg, bi-daily, i.p., for 10 days) or vehicle was administered to male wistar rats subjected to MCT injection or to pulmonary artery banding (PAB) to induce right ventricular (RV) overload without PAH. Expression of Ucn-2 and its receptor was increased in the RV of patients and rats with PAH. hUcn-2 treatment reduced PAH in MCT rats, resulting in decreased morbidity, improved exercise capacity and attenuated pulmonary arterial and RV remodelling and dysfunction. Additionally, RV gene expression of hypertrophy and failure signalling pathways were attenuated. hUcn-2 treatment also attenuated PAB-induced RV hypertrophy. Conclusions Ucn-2 levels are altered in human and experimental PAH. hUcn-2 treatment attenuates PAH and RV dysfunction in MCT-induced PH, has direct anti-remodelling effects on the pressure-overloaded RV, and improves pulmonary vascular function.

Neuregulin-1 attenuates right ventricular diastolic stiffness in experimental pulmonary hypertension

We have previously shown that treatment with recombinant human neuregulin‐1 (rhNRG‐1) improves pulmonary arterial hypertension (PAH) in a monocrotaline (MCT)‐induced animal model, by decreasing pulmonary arterial remodelling and endothelial dysfunction, as well as by restoring right ventricular (RV) function. Additionally, rhNRG‐1 treatment showed direct myocardial anti‐remodelling effects in a model of pressure loading of the RV without PAH. This work aimed to study the intrinsic cardiac effects of rhNRG‐1 on experimental PAH and RV pressure overload, and more specifically on diastolic stiffness, at both the ventricular and cardiomyocyte level. We studied the effects of chronic rhNRG‐1 treatment on ventricular passive stiffness in RV and LV samples from MCT‐induced PAH animals and in the RV from animals with compensated and decompensated RV hypertrophy, through a mild and severe pulmonary artery banding (PAB). We also measured passive tension in isolated cardiomyocytes and quantified the expression of myocardial remodelling‐associated genes and calcium handling proteins. Chronic rhNRG‐1 treatment decreased passive tension development in RV and LV isolated from animals with MCT‐induced PAH. This decrease was associated with increased phospholamban phosphorylation, and with attenuation of the expression of cardiac maladaptive remodelling markers. Finally, we showed that rhNRG‐1 therapy decreased RV remodelling and cardiomyocyte passive tension development in PAB‐induced RV hypertrophy animals, without compromising cardiac function, pointing to cardiac‐specific effects in both hypertrophy stages. In conclusion, we demonstrated that rhNRG‐1 treatment decreased RV intrinsic diastolic stiffness, through the improvement of calcium handling and cardiac remodelling signalling.

Improvement in left intraventricular pressure gradients after aortic valve replacement in aortic stenosis patients

What is the central question of this study? Normal diastolic and systolic intraventricular pressure gradients are decreased when left ventricular filling and/or emptying are compromised. We hypothesized that in patients with severe aortic valve stenosis, a condition that interferes with ventricular filling and emptying, those gradients would be disturbed. What is the main finding and its importance? We showed the existence of intraventricular pressure gradients throughout the cardiac cycle in the human left ventricle. Moreover, we demonstrated, for the first time, that diastolic and systolic gradients, which are markers of normal ventricular filling and emptying, respectively, improved in patients with severe aortic valve stenosis immediately after valve replacement.