Angiotensin II stimulates apoptosis via TGF-β1 signaling in ventricular cardiomyocytes of rat

Abstract

Elevations in angiotensin II (AngII) and transforming growth factor (TGF-beta1) levels are often found under conditions leading to progression of heart failure. From several studies, it is evident that AngII enhances TGF-beta1 expression via activator protein 1 (AP-1) activation, and that this pathway is involved in hypertrophic growth of the heart muscle and in the development of cardiac fibrosis. We now continued characterization of the signaling pathway stimulated by AngII in ventricular cardiomyocytes of rat and analyzed if the enhancement of TGF-beta1 expression by AngII may also contribute to apoptosis induction, which is another predictor of heart failure progression. Stimulation of cardiomyocytes with 100 nM AngII for 2 h activated the transcription factors AP-1 and GATA by 68.6+/-23.9 or 70.7+/-9.8%. Induction of both factors was mediated by p38 mitogen-activated protein kinase (MAPK) because it was totally blocked using a specific inhibitor of the kinase (SB202190). When GATA was inhibited by transformation of cardiomyocytes with decoy oligonucleotides, AngII could not enhance TGF-beta1 expression. This inhibition was observed on the mRNA level in real-time polymerase chain reaction and on the protein level in Western blots. As a consequence, upon AngII stimulation for 24 h, release of TGF-beta1 from cardiomyocytes was also reduced from 240.5+/-50.4 to 130.5+/-22.1% (p<0.05). In contrast to the early induction of GATA and AP-1, the transcription factor similar to mothers against decapentaplegic homolog (SMAD) was induced by AngII after 24 h. This stimulation was dependent on TGF-beta1 because it was blocked by antibodies specific for TGF-beta1. Twenty-four hours after AngII addition, the number of apoptotic cardiomyocytes increased by 6.5+/-1.2%, and this apoptosis induction was blocked when SMAD activity was inhibited by transformation of cardiomyocytes with SMAD decoy oligonucleotides. In conclusion, the transcription factors AP-1 and GATA are activated by p38 MAPK upon AngII stimulation, and both are needed to enhance TGF-beta1 expression in ventricular cardiomyocytes. TGF-beta1 acts in an autocrine loop on the cells to induce apoptosis via SMAD signaling. Thus, the often-found correlation between AngII, TGF-beta1, AP-1, and SMAD in pathogenesis of heart disease reflects the proapoptotic signaling pathway induced by AngII in cardiomyocytes.

Tanshinone IIA attenuates angiotensin II-induced apoptosis via Akt pathway in neonatal rat cardiomyocytes

“…The Akt pro- The results of our study demonstrated that Ang II caused cardiomyocyte apoptosis; this finding is consistent with that of previous studies and shows that Ang II acts as an efficient inducer of apoptosis in adult and neonatal cardiomyo cytes [5,6] . A statistically significant reduction of TUNEL-positive cardiomyocytes was observed when tanshinone IIA was added to Ang-II treated cells.…”

“…Pharmacological blockade of the renin-angiotensin system is beneficial in patients with heart failure [4] . Experiments using cultured cardiomyocytes have demonstrated that apoptosis can be stimulated in vitro by angiotensin II (Ang II) [5,6] . Ang II induces cardiomyocyte apoptosis, which contributes to heart failure possibly through enhanced ROS production [6] .…”

MiR‐133a regulates collagen 1A1: Potential role of miR‐133a in myocardial fibrosis in angiotensin II‐dependent hypertension

“…In the cardiovascular system, Angiotensin II (Ang II) promotes fibrosis by its hemodynamic and cellular effects, such as the modulation of TGFb signaling (Dzau, 2001;Schultz et al, 2002;Schroder et al, 2006;Gao et al, 2009;Leask, 2010) and the extracellular matrix turnover, through the major class of proteolitic enzymes (Campos et al, 2003;Castoldi et al, 2003Castoldi et al, , 2007Takenaka et al, 2006). Ang II has two main receptors, the Ang II type 1 receptors (AT1) and the Ang II type 2 receptors (AT2) (Timmermans et al, 1993).…”

Caspase-3 activation and increased procollagen type I in irradiated hearts

“…Its increased expression is followed by increased collagen deposition in irradiated tissue (Krüse et al 2001, Boerma et al 2002, Wynn 2008, Ferreira-Machado et al 2010. TGF-β1 can also be the primary mediator for apoptosis (Schröder et al 2006), but this relationship is unclear in the irradiated heart. Animals or patients, studies have demonstrated increased apoptosis pathway, evidenced particularly by the presence of cleaved-caspase-3, especially in the following heart diseases: ischemic cardiomyopathy, dilated cardiomyopathy, myocardial infarction, myocarditis, and arrhythmias (Condorelli et al 1999, Feuerstein and Young 2000, Philipp et al 2004, Kunapuli et al 2006, Ferrari et al 2009).…”

“…Growth stimulation initially occurs as a compensatory effort to meet chronically altered hemodynamic demands on the failing myocardium and is mediated by systemic and/or local up-regulation of mediators of adrenergic or rennin-angiotensin axes (Goldspink et al 2003, Schlüter and Wenzel 2008, Whelan et al 2010. Similarly, certain cytokines, like TGF-β1 can induce growth as well as apoptosis (Schröder et al 2006). The induction of apoptosis as a form of cell death distinct from necrosis is associated with activation of aspartate-specifc cysteine proteases such as caspase-3 (Goldspink et al 2003).…”