Background-Shed membrane microparticles circulate in the peripheral blood of nonischemic (NI) patients and patients with myocardial infarction (MI). We investigated whether or not these microparticles would affect endotheliumdependent responses. Methods and Results-Rat aortic rings with endothelium were exposed for 24 hours to circulating microparticles isolated from 7 patients with NI syndromes and 19 patients with acute MI. Endothelium-dependent relaxations to acetylcholine were not affected by high concentrations of microparticles from NI patients (Pϭ0.80). However, significant impairment was observed in preparations exposed to microparticles from patients with MI at low and high concentrations, corresponding to 0.7-fold and 2-fold circulating plasma levels (Pϭ0.05 and 0.001, respectively). Impairment was not affected by diclofenac (Pϭ0.47), nor by the cell-permeable superoxide dismutase mimetic Mn(III)tetra(4-benzoic acid) porphyrin chloride (Pϭ0.33), but it was abolished by endothelium removal or by N monomethyl-L-arginine. Relaxations to the calcium ionophore ionomycin were decreased in rings exposed to microparticles from MI patients (Pϭ0.05 and 0.009 for low and high concentrations, respectively), but microparticles from NI patients had no effect (Pϭ0.81). Finally, high concentrations of microparticles from MI patients affected neither endothelium-independent relaxation to sodium nitroprusside (Pϭ0.59) nor expression of the endothelial nitric oxide synthase (Pϭ0.43). Key Words: endothelium-derived factors Ⅲ nitric oxide synthase Ⅲ arteries Ⅲ vasodilation Ⅲ myocardial infarction M icroparticles generated in vitro from activated platelets or leukocytes stimulate cultured endothelial cells to produce prostacyclin and cytokines and to express adhesion molecules. [1][2][3][4] Recently, apoptotic microparticles have been identified in the circulating blood of patients with acute coronary syndromes and in nonischemic (NI) patients. 5 Acute myocardial infarction (MI) is associated with substantial impairment of vasodilator function in both infarcted myocardium and myocardium perfused by normal vessels. The determinants of this vasomotor dysfunction that may contribute to the extent of ischemia and necrosis after coronary occlusion are not fully elucidated. 6 In the present study, we examined whether or not microparticles circulating in the peripheral blood of NI patients and patients with acute MI affect endothelium-dependent responses in a normal blood vessels. Conclusions-Circulating Methods Patient SelectionWe prospectively included 19 patients with acute MI and 7 NI patients. Patients with MI had clinical, electrocardiographic, and enzymatic changes that were diagnostic of acute MI and were subsequently documented as having significant coronary atherosclerosis by angiography (Table). Control NI patients consisted of 4 patients recruited from the same cardiology department and 3 healthy subjects. Because relaxations did not differ among them (Pϭ0.35), these 7 subjects were pooled into one control NI group (me...

Abstract-The metabolic syndrome represents a constellation of cardiovascular risk factors that promote the development of cardiovascular disease. Oxidative stress is a mediator of endothelial dysfunction and vascular remodeling. We investigated vascular dysfunction in the metabolic syndrome and the oxidant mechanisms involved. New Zealand obese (NZO) mice with metabolic syndrome and New Zealand black control mice were studied. NZO mice showed insulin resistance and increased visceral fat and blood pressure compared with New Zealand black mice. Mesenteric resistance arteries from NZO mice exhibited increased media:lumen ratio and media cross-sectional area, demonstrating hypertrophic vascular remodeling. Endothelium-dependent relaxation to acetylcholine, assessed by pressurized myography, was impaired in NZO mice, not affected by N G -nitro-L-arginine methyl ester, inhibitor of endothelial NO synthase, and improved by the antioxidant Tempol, suggesting reduced NO bioavailability and increased oxidative stress. Dimer:monomer ratio of endothelial NO synthase was decreased in NZO mice compared with New Zealand black mice, suggesting endothelial NO synthase uncoupling. Furthermore, vascular superoxide and peroxynitrite production was increased, as well as adhesion molecule expression. Perivascular adipose tissue of NZO mice showed increased superoxide production and NADPH oxidase activity, as well as adipocyte hypertrophy, associated with inflammatory Mac-3-positive cell infiltration. Vasoconstriction to norepinephrine decreased in the presence of perivascular adipose tissue in New Zealand black mice but was unaffected by perivascular adipose tissue in NZO mice, suggesting loss of perivascular adipose tissue anticontractile properties. Our data suggest that this rodent model of metabolic syndrome is associated with perivascular adipose inflammation and oxidative stress, hypertrophic resistance artery remodeling, and endothelial dysfunction, the latter a result of decreased NO and enhanced superoxide generated by uncoupled endothelial NO synthase. Key Words: obesity Ⅲ hypertension Ⅲ NO Ⅲ eNOS Ⅲ superoxide Ⅲ NADPH T he metabolic syndrome represents a constellation of cardiovascular risk factors of metabolic origin that promote the development of cardiovascular disease and type 2 diabetes mellitus. 1 In the past few years, to identify patients with metabolic syndrome, several clinical and biochemical criteria have been established, such as visceral obesity, increased plasma glucose, atherogenic dyslipidemia, and increased blood pressure (BP). 2,3 Among them, visceral obesity is widely accepted as a diagnostic prerequisite, and it is believed to be involved in the pathogenesis of the metabolic disarray itself by inducing insulin resistance.Although the clinical association of metabolic risk factors and BP increase is well established, the underlying mechanisms are still a matter of debate. Vascular dysfunction of resistance arteries plays a key role in the development of hypertension and is mediated, at least in part, b...

Nitric oxide (NO) has been implicated in the development of heart failure, although the source, significance, and functional role of the different NO synthase (NOS) isoforms in this pathology are controversial. The presence of a neuronal-type NOS isoform (NOS1) in the cardiac sarcoplasmic reticulum has been recently discovered, leading to the hypothesis that NOS1-derived NO may notably alter myocardial inotropy. However, the regulation and role(s) of NOS1 in cardiac diseases remain to be determined. Using an experimental model of myocardial infarction (MI) in senescent rats, we demonstrated a significant increase in cardiac NOS1 expression and activity in MI, coupled with the translocation of this enzyme to the sarcolemma through interactions with caveolin-3. The enhanced NOS1 activity counteracts the decrease in cardiac NOS3 expression and activity observed in heart failure. We demonstrated an increased interaction between NOS1 and its regulatory protein HSP90 in post-MI hearts, a potential mechanism for the higher NOS1 activity in this setting. Finally, preferential in vivo inhibition of NOS1 activity enhanced basal post-MI left ventricular dysfunction in senescent rats. These results provide the first evidence that increased NOS1-derived NO production may play a significant role in the autocrine regulation of myocardial contractility after MI in aging rats.

Abstract-Endothelial progenitor cells (EPCs) contribute to endothelial regeneration. Angiotensin II (Ang II) through Ang II type 1 receptor (AT 1 -R) activation plays an important role in vascular damage. The effect of Ang II on EPCs and the involved molecular mechanisms are incompletely understood. Stimulation with Ang II decreased the number of cultured human early outgrowth EPCs, which express both AT 1 -R and Ang II type 2 receptor, mediated through AT 1 -R activation and induction of oxidative stress. Ang II redox-dependently induced EPC apoptosis through increased apoptosis signal-regulating kinase 1, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase phosphorylation; decreased Bcl-2 and increased Bax expression; and activation of caspase 3 but had no effect on the low cell proliferation. In addition, Ang II impaired colony-forming and migratory capacities of early outgrowth EPCs. Ang II infusion diminished numbers and functional capacities of EPCs in wild-type (WT) but not AT 1 a-R knockout mice (AT 1 a Ϫ/Ϫ). Reendothelialization after focal carotid endothelial injury was decreased during Ang II infusion. Salvage of reendothelialization by intravenous application of spleen-derived progenitor cells into Ang II-treated WT mice was pronounced with AT 1 a Ϫ/Ϫ cells compared with WT cells, and transfusion of Ang II-pretreated WT cells into WT mice without Ang II infusion was associated with less reendothelialization. Transplantation of AT 1 a Ϫ/Ϫ bone marrow reduced atherosclerosis development in cholesterol-fed apolipoprotein E-deficient mice compared with transplantation of apolipoprotein E-deficient or WT bone marrow. Randomized treatment of patients with stable coronary artery disease with the AT 1 -R blocker telmisartan significantly increased the number of circulating CD34/KDR-positive EPCs. Ang II through AT 1 -R activation, oxidative stress, and redox-sensitive apoptosis signal-regulating kinase 1-dependent proapoptotic pathways impairs EPCs in vitro and in vivo, resulting in diminished vascular regeneration. (Hypertension. 2011;58:394-403.) • Online Data Supplement

Key Words: aldosterone Ⅲ AT 1 R Ⅲ AT 1a R Ⅲ AT 1b R Ⅲ intracellular signaling P athophysiological synergistic effects between angiotensin II (Ang II) and aldosterone have been described on vascular cells and support the concept that combination of aldosterone and Ang II receptor blockade may be therapeutically beneficial. [1][2][3][4] In the past few years, investigators have demonstrated that blockade of mineralocorticoid receptor (MR) reduced mortality caused by progressive heart failure and sudden death from cardiac causes, as well as rate of hospitalization for heart failure. These results were observed in patients with severe heart failure who were also being treated with an angiotensin-converting enzyme inhibitor and included subjects developing heart failure after myocardial infarction. 5,6 Growing evidence has shown that aldosterone could influence the signaling or trafficking of the Ang II type 1 receptor (AT 1 R). Indeed, mineralocorticoids such as deoxycorticosterone and aldosterone caused upregulation of Ang II binding to blood vessels and cultured VSMCs. 4,7,8 Spironolactone, a specific antagonist of MR, has been shown to inhibit Ang II-stimulated proliferation of VSMCs. 9 Recent studies have unraveled further evidence of a crosstalk between AT 1 R and MR. Ang II could directly stimulated nuclear localization of MR in human coronary and aortic VSMCs, supporting a role of MR in gene expression after Ang II stimulation. 10 Spironolactone also inhibits Ang II-induced senescence of VSMCs. These studies suggest that vascular responses to Ang II could be mediated via direct signaling crosstalk between MR and AT 1 R. 11 Among rodents, mice have 2 subtypes of AT 1 R, AT 1a R and Ang II type 1b receptor (AT 1b R). In the present study, we hypothesized that AT 1a R and AT 1b R interact differentially with MR to signal intracellularly. We sought to understand more precisely the molecular mechanisms underlying crosstalk between the 2 subtypes of AT 1 R present in the mouse, AT 1a R and AT 1b R, and MR. We focused on the effects that potential crosstalk had on activation of extracel- Original received February 27, 2009; revision received September 8, 2009; accepted September 9, 2009 Methods Cell Culture and TransfectionVSMCs derived from mesenteric arteries of 8 weeks male C57Bl/6 and AT 1a R knockout mice were isolated and characterized as described previously. 12,13 AT 1a R knockout mice were produced at Duke University 14 and later bred in the animal facility at the Lady Davis Institute. Briefly, mesenteric arteries were cleaned of adipose and connective tissue and VSMCs were dissociated by the enzymatic digestion of vascular arcades. Quantitative RT-PCREfficiency of siRNA targeting AT 1a R, AT 1b R, and MR was verified by quantitative real-time polymerase chain reaction (QRT-PCR). VSMC RNA was isolated by homogenization in TRIzol reagent (Invitrogen) followed by chloroform extraction and isopropanol precipitation. One microgram of total RNA was reversed-transcribed with random hexamers and Superscript II (...

Mmp2 knockout impaired Ang II-induced vascular injury but not BP elevation. BM transplantation revealed a role for immune cells in Ang II-induced BP elevation, and for both vascular and immune cell MMP2 in Ang II-induced endothelial dysfunction.

Ang II, via AT2R, facilitates vasodilation through NOS/NO-mediated pathways and upregulation [corrected] of CGK1 [corrected] after chronic AT1R antagonism. These effects may contribute in part to beneficial actions of AT1R blockers in the treatment of hypertension.

Monocyte/macrophage deficiency in Op/+ mice results in absence of aldosterone-induced oxidative stress and endothelial dysfunction, but does not play a role in aldosterone-induced arterial stiffness. Thus, although monocyte/macrophage-mediated inflammatory responses play a role in oxidative stress and endothelial dysfunction, vascular stiffening in response to aldosterone may be independent of inflammation.