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-␣-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. (Circulation. 2010;122[suppl 1]:S185-S192.)Key Words: adropin Ⅲ angiogenesis Ⅲ endothelium Ⅲ nitric oxide T he endothelium plays a central role in the maintenance of vascular homeostasis, and impaired endothelial function contributes to the development and progression of diverse cardiovascular, inflammatory, metabolic, infectious, and renal diseases, of which atherothrombosis has the largest clinical impact. 1 Endothelial cell (EC) homeostasis is maintained in part through the synthesis of nitric oxide (NO), from the precursor L-arginine, under the influence of endothelial NO synthase (eNOS). Aside from exerting several critical antiinflammatory, antithrombotic, and antiatherosclerotic roles within blood vessels, NO also promotes postnatal angiogenesis and reparative vasculogenesis. Furthermore, there is good evidence that NO bioavailability serves an important role in metabol...

dothelium plays a central role in the maintenance of vascular homeostasis. One of the main effectors of endothelial dysfunction is ANG II, and pharmacological approaches to limit ANG II bioactivity remain the cornerstone of cardiovascular therapeutics. Angiotensin converting enzyme-2 (ACE2) has been identified as a critical negative modulator of ANG II bioactivity, counterbalancing the effects of ACE in determining net tissue ANG II levels; however, the role of ACE2 in the vasculature remains unknown. In the present study, we hypothesized that ACE2 is a novel target to limit endothelial dysfunction and atherosclerosis. To this aim, we performed in vitro gain and loss of function experiments in endothelial cells and evaluated in vivo angiogenesis and atherosclerosis in apolipoprotein E-knockout mice treated with AdACE2. ACE2-deficient mice exhibited impaired endothelium-dependent relaxation. Overexpression of ACE2 in human endothelial cells stimulated endothelial cell migration and tube formation, and limited monocyte and cellular adhesion molecule expression; effects that were reversed in ACE2 gene silenced and endothelial cells isolated from ACE2-deficient animals. ACE2 attenuated ANG II-induced reactive oxygen species production in part through decreasing the expression of p22phox. The effects of ACE2 on endothelial activation were attenuated by pharmacological blockade of ANG-(1-7) with A779. ACE2 promoted capillary formation and neovessel maturation in vivo and reduced atherosclerosis in apolipoprotein E-knockout mice These data indicate that ACE2, in an ANG-(1-7)-dependent fashion, functions to improve endothelial homeostasis via a mechanism that may involve attenuation of NADPHox-induced reactive oxygen species production. ACE2-based treatment approaches may be a novel approach to limit aberrant vascular responses and atherothrombosis. endothelium; atherogenesis; angiogenesis THE ENDOTHELIUM FUNCTIONS as a protective biocompatible barrier between all tissues and the circulating blood (17). Endothelial cells also function as a selective sieve to facilitate bidirectional passage of macromolecules and blood gases to and from tissues and blood (17). The strategic location of the endothelium allows it to "sense" changes in hemodynamic forces and blood-borne signals and "respond" by releasing a number of autocrine and paracrine substances. A balanced release of these bioactive factors facilitates vascular homeostasis. Endothelial cell dysfunction disrupts this balance, thereby predisposing the vessel wall to vasoconstriction, leukocyte adherence, platelet activation, mitogenesis, prooxidation, thrombosis, impaired coagulation, vascular inflammation, and atherosclerosis. Improving endothelial function is a major goal of cardiovascular risk reduction.The renin-angiotensin system (RAS) is a pivotal transducer of cardiovascular function and plays a causal role in the development and progression of endothelial dysfunction and atherosclerosis (7,15,17). RAS supports a series of complex enzymatic reactions that culmina...

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 Ϫ/Ϫ ) mice were treated with either a microRNA-145 lentivirus under the control of the smooth muscle cell (SMC)-specific promoter SM22␣ or a SM22␣ 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 Ϫ/Ϫ mice treated with the SMC-specific microRNA-145. These mice also demonstrated marked increases in calponin levels and ␣-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 Ϫ/Ϫ 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.

The tumour suppressor BRCA1 is mutated in familial breast and ovarian cancer but its role in protecting other tissues from DNA damage has not been explored. Here we show a new role for BRCA1 as a gatekeeper of cardiac function and survival. In mice, loss of BRCA1 in cardiomyocytes results in adverse cardiac remodelling, poor ventricular function and higher mortality in response to ischaemic or genotoxic stress. Mechanistically, loss of cardiomyocyte BRCA1 results in impaired DNA double-strand break repair and activated p53-mediated pro-apoptotic signalling culminating in increased cardiomyocyte apoptosis, whereas deletion of the p53 gene rescues BRCA1-deficient mice from cardiac failure. In human adult and fetal cardiac tissues, ischaemia induces double-strand breaks and upregulates BRCA1 expression. These data reveal BRCA1 as a novel and essential adaptive response molecule shielding cardiomyocytes from DNA damage, apoptosis and heart dysfunction. BRCA1 mutation carriers, in addition to risk of breast and ovarian cancer, may be at a previously unrecognized risk of cardiac failure.