YAP activation promotes the transdifferentiation of cardiac fibroblasts to myofibroblasts in matrix remodeling of dilated cardiomyopathy

Yes-associated protein (YAP) is an important regulator of cellular proliferation and transdifferentiation. However, little is known about the mechanisms underlying myofibroblast transdifferentiation in dilated cardiomyopathy (DCM). We investigated the role of YAP in the pathological process of cardiac matrix remodeling. A classic model of DCM was established in BALB/c mice by immunization with porcine cardiac myosin. Cardiac fibroblasts were isolated from neonatal Sprague-Dawley rats by density gradient centrifugation. The expression levels of α-smooth muscle actin (α-SMA) and collagen volume fraction (CVF) were significantly increased in DCM mice. Angiotensin II (Ang II)-mediated YAP activation promoted the proliferation and transdifferentiation of neonatal rat cardiac fibroblasts, and this effect was significantly suppressed in the shRNA YAP + Ang II group compared with the shRNA Control + Ang II group in vitro (2.98±0.34 ×105 vs 5.52±0.82 ×105, P<0.01). Inhibition of endogenous Ang II-stimulated YAP improved the cardiac function by targeting myofibroblast transdifferentiation to attenuate matrix remodeling in vivo. In the valsartan group, left ventricular ejection fraction and fractional shortening were significantly increased compared with the DCM group (52.72±5.51% vs 44.46±3.01%, P<0.05; 34.84±3.85% vs 26.65±3.12%, P<0.01). Our study demonstrated that YAP was a regulator of cardiac myofibroblast differentiation, and regulation of YAP signaling pathway contributed to improve cardiac function of DCM mice, possibly in part by decreasing myofibroblast transdifferentiation to inhibit matrix remodeling.

El inflamasoma: mecanismos de activación / Inflammasome: activation mechanisms

La inflamación es una respuesta biológica rápida del sistema inmune en tejidos vasculares, dirigida a eliminar estímulos capaces de producir daño y a iniciar la curación y la reparación. Los complejos macromoleculares denominados inflamasomas están constituidos por un receptor NOD (NLR), un receptor de AIM2 (ausente en melanoma 2) el ALR, la proteína tipo punto asociada a apoptosis (ASC) y la procaspasa-1, los cuales pueden ser activados por variación en la concentración iónica y de ATP intracelular y extracelular, por desestabilización del fagolisosoma, por internalización de cristales insolubles y por mecanismos de oxidoreducción, lo cual permitirá la activación de la plataforma molecular y el consiguiente procesamiento de las prointerleuquinas inflamatorias a sus formas activas. En la actualidad existen dos nodos de señalización utilizados por los inflamasomas: canónica y no canónica para generar respuestas efectoras. Datos recientes vinculan al inflamasoma NLRP3, la IL-1b y a la IL-18, en el desarrollo y evolución de enfermedades tales como: ateroesclerosis, diabetes tipo II, hiperhomocisteinemia, gota, malaria e hipertensión arterial e identificaron esta cascada, como un blanco quimioterapéutico ideal para la prevención de estas patologías. En esta revisión se discutirán los mecanismos de activación y regulación del inflamasoma que estimulan, modulan y resuelven los procesos inflamatorios.

Inflammation is a rapid biologic response of the immune system in vascular tissues, directed to eliminate stimuli capable of causing damage and begin the process of repair. The macromolecular complexes known as “inflammasomes” are formed by a receptor, either NOD (NLR) or ALR, the receptor absent in melanoma 2 (AIM2). In addition, the inflammasome is formed by the speck-like protein associated to apoptosis (ASC) and procaspase-1, that may be activated by variations in the ionic and intracellular and extracellular ATP concentrations; and the loss of stabilization of the fagolisosomme by internalization of insoluble crystals and redox mechanisms. As a result, there is activation of the molecular platform and the processing of inflammatory prointerleukins to their active forms. There are two modalities of activation of the inflammasome: canonical and non-canonical, both capable of generating effector responses. Recent data associate NLRP 3, IL-1b and IL-18 in the pathogenesis of a variety of diseases, including atherosclerosis, type II diabetes, hyperhomocysteinemia, gout, malaria and hypertension. The inflammasome cascade is emerging as a new chemotherapeutic target in these diseases. In this review we shall discuss the mechanisms of activation and regulation of the inflammasome that stimulate, modulate and resolve inflammation.