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Background— In patients with myocardial infarction, high serum levels of interleukin-6 cytokines predict a poor outcome. The common receptor of interleukin-6 cytokines, glycoprotein-130 (gp130), signals via janus kinase/signal transducer and activator of transcription (STAT), cytoplasmic protein tyrosine phosphatase/extracellular signal-regulated kinase, and phosphoinositide-3-kinase/Akt pathways, and the regulation of these pathways depends at least in part on the gp130 tyrosine-757 residue. By analyzing cardiomyocyte-specific gp130 Y757F mutant mice, we investigated the effect of disturbed gp130 signaling after myocardial infarction. Methods and Results— The cardiomyocyte-restricted α-myosin heavy chain-Cre-recombinase-loxP system was used to generate mice with gp130 Y757F mutant cardiomyocytes ( αMHC-Cre tg/− ;gp130 fl/Y757F [Y 757 F]); all other cells carried at least 1 functional gp130 gene, ensuring normal gp130 signaling. Y 757 F mice displayed normal cardiac function and morphology at 3 months of age comparable to their nonmutant littermates. In response to myocardial infarction, Y 757 F mice displayed higher mortality associated with increased left ventricular rupture rate, sustained cardiac inflammation, and heart failure. These adverse effects were associated with prolonged and enhanced STAT3 activation and increased expression of interleukin-6 and of the complement-activating mannose-binding lectin C. Pharmacological inhibition of the complement system by cobra venom factor attenuated inflammation, prevented left ventricular rupture, and improved cardiac function in Y 757 F mice. Stronger effects were observed with a genetic reduction of STAT3 (STAT3 flox/+ ) restricted to cardiomyocytes in Y 757 F mice, which prevented extensive upregulation of interleukin-6, complement activation, and sustained inflammation and lowered left ventricular rupture rate, heart failure, and mortality in subacute myocardial infarction. Conclusion— Impaired downregulation of gp130-mediated STAT3 activation in subacute infarction promotes cardiac inflammation, adverse remodeling, and heart failure, suggesting a potential causative role of high interleukin-6 serum levels after myocardial infarction.

Background— MicroRNA are essential posttranscriptional modulators of gene expression implicated in various chronic diseases. Because microRNA-145 is highly expressed in vascular smooth muscle cells (VSMC) and regulates VSMC fate and plasticity, we hypothesized that it may be a novel regulator of atherosclerosis and plaque stability. Methods and Results— Apolipoprotein E knockout mice ( ApoE −/− ) mice were treated with either a microRNA-145 lentivirus under the control of the smooth muscle cell (SMC)-specific promoter SM22 α or a SM22 α control lentivirus before commencing the Western diet for 12 weeks. The SMC-targeted microRNA-145 treatment markedly reduced plaque size in aortic sinuses, ascending aortas, and brachiocephalic arteries. It also significantly increased fibrous cap area, reduced necrotic core area, and increased plaque collagen content. Cellular plaque composition analyses revealed significantly less macrophages in ApoE −/− mice treated with the SMC-specific microRNA-145. These mice also demonstrated marked increases in calponin levels and α-smooth muscle actin–positive SMC areas in their atherosclerotic lesions. Furthermore, lentiviral delivery of microRNA-145 resulted in reduced KLF4 and elevated myocardin expression in aortas from ApoE −/− mice, consistent with an effect of microRNA-145 to promote a contractile phenotype in VSMC. Conclusions— VSMC-specific overexpression of microRNA-145 is a novel in vivo therapeutic target to limit atherosclerotic plaque morphology and cellular composition, shifting the balance toward plaque stability vs plaque rupture.

Background— Adropin is a recently identified protein that has been implicated in the maintenance of energy homeostasis and insulin resistance. Because vascular function and insulin sensitivity are closely related, we hypothesized that adropin may also exert direct effects on the endothelium. Methods and Results— In vitro cell culture models were partnered with an in vivo murine injury model to determine the potential vascular effects of adropin. Adropin was expressed in human umbilical vein and coronary artery endothelial cells (ECs). Adropin-treated endothelial cells exhibited greater proliferation, migration and capillary-like tube formation and less permeability and tumor necrosis factor-α–induced apoptosis. In keeping with a vascular protective effect, adropin stimulated Akt Ser 473 and endothelial nitric oxide (NO) synthase Ser 1177 phosphorylation. The former was abrogated in the presence of the phosphatidylinositol 3-kinase inhibitor LY294002, whereas the latter was attenuated by LY294002 and by mitogen-activated protein kinase kinase 1 inhibition with PD98059. Together, these findings suggest that adropin regulates NO bioavailability and events via the phosphatidylinositol 3-kinase-Akt and extracellular signal regulated kinase 1/2 signaling pathways. Adropin markedly upregulated vascular endothelial growth factor receptor-2 (VEGFR2) transcript and protein levels, and in VEGFR2-silenced endothelial cells, adropin failed to induce phosphorylation of endothelial NO synthase, Akt, and extracellular signal regulated kinase 1/2, supporting VEGFR2 as an upstream target of adropin-mediated endothelial NO synthase activation. Last, adropin improved murine limb perfusion and elevated capillary density following induction of hindlimb ischemia. Conclusions— We report a potential endothelial protective role of adropin that is likely mediated via upregulation of endothelial NO synthase expression through the VEGFR2-phosphatidylinositol 3-kinase-Akt and VEGFR2-extracellular signal regulated kinase 1/2 pathways. Adropin represents a novel target to limit diseases characterized by endothelial dysfunction in addition to its favorable metabolic profile.

INTRODUCTION: Preservation of structure and function of the myocardium is critically dependent upon improving the survival of existing cardiomyocytes (CM), through strategies that limit CM apoptosis and DNA damage. BRCA1 is a tumor suppressor gene which functions to promote DNA repair, and protect cells against oxidative and genotoxic stress. We hypothesized that BRCA1 is a novel cellular target to limit CM apoptosis, and prevent aberrant cardiac remodeling. METHODS AND RESULTS: Experimental MI in mice caused a profound 16-fold upregulation in BRCA1 expression, which peaked at 72 hours (pIn vitro gain-of-function experiments demonstrated that Ad-BRCA1 overexpression protected neonatal rat CM against doxorubicin- and H 2 O 2 -induced apoptosis, as assessed by FACS (p2 O 2 . Co-immunoprecipitation studies demonstrated a distinct physical interaction of BRCA1 with p53. Inhibition of p53, with pifithrin-alpha, blocked doxorubicin-induced CM apoptosis in a manner similar to BRCA1, but BRCA1-overexpressing CM, when treated with doxorubicin did not show further reduction with pifithrin-alpha, indicating an essential requirement of BRCA1 to modulate p53. In vivo gain-of-function studies demonstrated that systemic Ad-BRCA1 delivery completely prevented doxorubicin-induced cardiac dysfunction in mice (echocardiography, pIn vivo loss-of-function studies were performed in CM -specific BRCA1-KO mice (developed using Cre-lox P technology), which demonstrated marked cardiac dysfunction and mortality in response to doxorubicin administration (p< 0.01 vs. WT + Dox). CONCLUSIONS: We report for the first time an essential role of BRCA1 to limit CM apoptosis, and improve cardiac function in response to genotoxic and oxidative stress. Heart specific deletion of BRCA1 promotes severe systolic dysfunction, and limits survival. In addition to the immediate implications for cardiovascular repair, these data may have ramifications for individuals with BRCA1 mutations or cancer syndromes, particularly in the setting of adjuvant chemotherapy.

INTRODUCTION: Endothelial cell apoptosis, in response to inflammatory, ischemic and hypoxic stressors, has been identified as an essential target for therapies aimed at improving graft patency. BRCA1 is a tumor suppressor gene which functions primarily to promote DNA repair, and afford protection against various genotoxic stimuli, including immunosuppressant and chemotherapeutic regimens often employed post-transplantation. We hypothesized that BRCA1 is a novel target to limit inflammation-induced endothelial cell apoptosis and to restore endothelial function. METHODS AND RESULTS: In the first series of studies, we used a gain-of-function approach by adenoviral BRCA1 overexpression in human umbilical vein endothelial cells (HUVECs). Ad-BRCA1-expressing HUVECs exhibited profound protection against TNFα (20 ng/ml)-induced apoptosis, as assessed by flow cytometry, DNA laddering, COMET assay and cleaved procaspase 3 (P < 0.01). This response was mediated by complete prevention of TNFα-induced increases in endothelial ROS production (P < 0.001, vs. Ad-BRCA1). Furthermore, Ad-BRCA1 overexpression prevented TNFα-induced reduction in key indices of endothelial function, namely capillary-like tube formation (P < 0.01) and cell migration (P < 0.01). The protective effects of BRCA1 were not mediated by changes in total or phosphorylated p53 (P = 0.1) but were associated with a significant 6-fold upregulation in eNOS (P < 0.05). A loss-of-function strategy with BRCA1 gene silencing reversed the effects on endothelial apoptosis, ROS production and eNOS phosporylation. CONCLUSIONS: BRCA1 protects endothelial cells against inflammation-induced apoptosis, through a mechanism that involves up-regulation of eNOS and reduced ROS production, and is a novel candidate gene to limit aberrant vascular remodeling. These data also suggest that patients with BRCA1 mutations or cancer syndromes may be at an exaggerated risk of native and transplant atherosclerosis and graft dysfunction, particularly in the setting of DNA damaging immunosuppressants.