Abstract-Data from the Women's Health Study show that serum levels of growth-differentiation factor-15 (GDF-15), a distant member of the transforming growth factor-␤ superfamily, are an independent risk indicator for adverse cardiovascular events. However, the cellular sources, upstream regulators, and functional effects of GDF-15 in the cardiovascular system have not been elucidated. We have identified GDF-15 by cDNA expression array analysis as a gene that is strongly upregulated by nitrosative stress in cultured cardiomyocytes isolated from 1-to 3-day-old rats. GDF-15 mRNA and pro-peptide expression levels were also induced in cardiomyocytes subjected to simulated ischemia/reperfusion (I/R) via NO-peroxynitrite-dependent signaling pathways. GDF-15 was actively secreted into the culture supernatant, suggesting that it might exert autocrine/paracrine effects during I/R. To explore the in vivo relevance of these findings, mice were subjected to transient or permanent coronary artery ligation. Myocardial GDF-15 mRNA and pro-peptide abundance rapidly increased in the area-at-risk after ischemic injury. Similarly, patients with an acute myocardial infarction had enhanced myocardial GDF-15 pro-peptide expression levels. As shown by immunohistochemistry, cardiomyocytes in the ischemic area contributed significantly to the induction of GDF-15 in the infarcted human heart. To delineate the function of GDF-15 during I/R, Gdf-15 gene-targeted mice were subjected to transient coronary artery ligation for 1 hour followed by reperfusion for 24 hours. Gdf-15-deficient mice developed greater infarct sizes and displayed more cardiomyocyte apoptosis in the infarct border zone after I/R compared with wild-type littermates, indicating that endogenous GDF-15 limits myocardial tissue damage in vivo. Moreover, treatment with recombinant GDF-15 protected cultured cardiomyocytes from apoptosis during simulated I/R as shown by histone ELISA, TUNEL/Hoechst staining, and annexin V/propidium iodide fluorescence-activated cell sorting (FACS) analysis. Mechanistically, the prosurvival effects of GDF-15 in cultured cardiomyocytes were abolished by phosphoinositide 3-OH kinase inhibitors and adenoviral expression of dominant-negative Akt1 (K179M mutation). In conclusion, our study identifies induction of GDF-15 in the heart as a novel defense mechanism that protects from I/R injury. Key Words: growth-differentiation factor-15 Ⅲ ischemia/reperfusion Ⅲ apoptosis Ⅲ PI3K Ⅲ Akt C oronary reperfusion is the primary therapeutic goal in patients with acute myocardial infarction (AMI). Although reperfusion is essential for myocardial salvage, it may at first exacerbate cellular damage sustained during the ischemic period, a phenomenon known as reperfusion injury. 1 There is growing evidence that the myocardium adapts to ischemia/reperfusion (I/R) by synthesizing and responding to a variety of stress-induced growth factors and cytokines, and that identification of these endogenous homeostatic mechanisms may open new avenues to limit I/R injury. 2,3 ...

Adverse left ventricular (LV) remodeling after myocardial infarction (MI) is a major cause for heart failure. Molecular modifiers of the remodeling process remain poorly defined. Patients with heart failure after MI have reduced LV expression levels of muscle LIM protein (MLP), a component of the sarcomeric Z-disk that is involved in the integration of stress signals in cardiomyocytes. By using heterozygous MLP mutant (MLP ؉/؊ ) mice, we explored the role of MLP in post-MI remodeling. LV dimensions and function were similar in sham-operated WT and MLP ؉/؊ mice. After MI, however, MLP ؉/؊ mice displayed more pronounced LV dilatation and systolic dysfunction and decreased survival compared with WT mice, indicating that reduced MLP levels predispose to adverse LV remodeling. LV dilatation in MLP ؉/؊ mice was associated with reduced thickening but enhanced elongation of cardiomyocytes. Activation of the stress-responsive, prohypertrophic calcineurinnuclear factor of activated T-cells (NFAT) signaling pathway was reduced in MLP ؉/؊ mice after MI, as shown by a blunted transcriptional activation of NFAT in cardiomyocytes isolated from MLP ؉/؊ ͞NFAT-luciferase reporter gene transgenic mice. Calcineurin was colocalized with MLP at the Z-disk in WT mice but was displaced from the Z-disk in MLP ؉/؊ mice, indicating that MLP is essential for calcineurin anchorage to the Z-disk. In vitro assays in cardiomyocytes with down-regulated MLP confirmed that MLP is required for stress-induced calcineurin-NFAT activation. Our study reveals a link between the stress sensor MLP and the calcineurin-NFAT pathway at the sarcomeric Z-disk in cardiomyocytes and indicates that reduced MLP-calcineurin signaling predisposes to adverse remodeling after MI.heart failure ͉ stress signaling C hronic heart failure is a worldwide epidemic. Recently, a fundamental shift in the underlying etiology of heart failure has occurred, in which the most common cause of heart failure is no longer hypertension or valvular disease, but myocardial infarction (MI) (1). MI induces profound alterations of left ventricular (LV) architecture with scar formation, ventricular dilatation, and hypertrophy of the noninfarcted (remote) myocardium (2). Biomechanical stress and humoral growth factors are important mediators of this remodeling process (3, 4). At the level of the single cardiomyocyte, post-MI LV remodeling is characterized by increases in cell diameter and cell length and alterations in gene expression levels (5-7).The Z-disk is a multiprotein complex located at the interface of the cytoskeleton, the contractile apparatus, and the sarcolemma in cardiomyocytes (8). Muscle LIM protein (MLP), which is tethered to the Z-disk via its interacting partners, ␣-actinin and telethonin, has been proposed to be an essential part of the mechanical stretch sensor machinery (9) and to be involved in the transmission of humoral growth signals in cardiomyocytes (10). Intriguingly, myocardial MLP levels are reduced by Ϸ50% in patients with heart failure after MI (11). However, ...

on behalf of the German Heart Failure Network Background-Ischemic heart disease and heart failure are associated with an increased loss of cardiomyocytes due to apoptosis. Whether cardiomyocyte apoptosis plays a causal role in the pathogenesis of heart failure remains enigmatic. The apoptosis repressor with caspase recruitment domain (ARC) is a recently discovered antiapoptotic factor with a highly specific expression pattern in striated muscle and neurons. ARC is a master regulator of cardiac death signaling because it is the only known factor that specifically inhibits both the intrinsic and extrinsic apoptotic death pathway. In this study we attempted to elucidate the physiological role of ARC and to understand pathophysiological consequences resulting from its deletion. Methods and Results-We generated ARC-deficient mice, which developed normally to adulthood and had no abnormality in cardiac morphology and function under resting conditions. On biomechanical stress induced by aortic banding, ARC-deficient mice developed accelerated cardiomyopathy compared with littermate controls, which was characterized by reduced contractile function, cardiac enlargement, and myocardial fibrosis. Likewise, ischemia/ reperfusion injury of ARC-deficient mice resulted in markedly increased myocardial infarct sizes. Although in both instances a significant increase in apoptotic cardiomyocytes could be observed in ARC-deficient mice, neither in vitro nor in vivo studies revealed any effect of ARC on classic hypertrophic cardiomyocyte growth responses. The pathophysiological relevance of downregulated ARC levels was underscored by specimens from failing human hearts showing markedly reduced ARC protein levels. Conclusions-Our study identifies a tissue-specific antiapoptotic factor that is downregulated in human failing myocardium and that is required for cardioprotection in pressure overload and ischemia.