Abdelali Agouni

Endothelial Dysfunction Caused by Circulating Microparticles from Patients with Metabolic Syndrome

Microparticles are membrane vesicles that are released during cell activation and apoptosis. Elevated levels of microparticles occur in many cardiovascular diseases; therefore, we characterized circulating microparticles from both metabolic syndrome (MS) patients and healthy patients. We evaluated microparticle effects on endothelial function; however, links between circulating microparticles and endothelial dysfunction have not yet been demonstrated. Circulating microparticles and their cellular origins were examined by flow cytometry of blood samples from patients and healthy subjects. Microparticles were used either to treat human endothelial cells in vitro or to assess endothelium function in mice after intravenous injection. MS patients had increased circulating levels of microparticles compared with healthy patients, including microparticles from platelet, endothelial, erythrocyte, and procoagulant origins. In vitro treatment of endothelial cells with microparticles from MS patients reduced both nitric oxide (NO) and superoxide anion production, resulting in protein tyrosine nitration. These effects were associated with enhanced phosphorylation of endothelial NO synthase at the site of inhibition. The reduction of O2(-) was linked to both reduced expression of p47 phox of NADPH oxidase and overexpression of extracellular superoxide dismutase. The decrease in NO production was triggered by nonplatelet-derived microparticles. In vivo injection of MS microparticles into mice impaired endothelium-dependent relaxation and decreased endothelial NO synthase expression. These data provide evidence that circulating microparticles from MS patients influence endothelial dysfunction.

The phosphoinositide 3-kinase/Akt pathway: a new target in human renal cell carcinoma therapy.

Metastatic renal cell carcinoma is resistant to current therapies. The phosphoinositide 3-kinase (PI3K)/Akt signaling cascade induces cell growth, cell transformation, and neovascularization. We evaluated whether targeting this pathway could be of therapeutic value against human renal cell carcinoma. The activation of the PI3K/Akt pathway and its role in renal cell carcinoma progression was evaluated in vitro in seven human cell lines by Western blot, cell counting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, terminal deoxyribonucleotide transferase-mediated nick-end labeling assays, and fluorescence-activated cell sorting analysis, using two PI3K inhibitors, LY294002 and wortmannin, as well as by transfection with various Akt constructs and through Akt knockdown by small interfering RNA (siRNA). In vivo nude mice bearing human renal cell carcinoma tumor xenografts were treated with LY294002 (75 mg/kg/wk, 4 weeks, i.p.). Tumor growth was measured and tumors were subjected to Western blot and immunohistochemical analysis. Akt was constitutively activated in all cell lines. Constitutive phosphorylation of glycogen synthase kinase-3 (GSK-3) was observed in all cell lines, whereas forkhead transcription factor and mammalian target of rapamycin, although expressed, were not constitutively phosphorylated. Exposure to LY294002 or wortmannin decreased Akt activation and GSK-3 phosphorylation and reduced cell growth by up to 70% through induction of cell apoptosis. These effects were confirmed by transfection experiments with Akt constructs or Akt siRNA. Importantly, LY294002 induced up to 50% tumor regression in mice through tumor cell apoptosis. Tumor neovascularization was significantly increased by LY294002 treatment. Blood chemistries showed no adverse effects of the treatment. Our results suggest an important role of PI3K/Akt inhibitors as a potentially useful treatment for patients with renal cell carcinoma.

Sonic hedgehog carried by microparticles corrects endothelial injury through nitric oxide release

Microparticles (MPs) are small fragments generated from the plasma membrane after cell stimulation. Among the candidate proteins harbored by MPs, we recently showed that sonic hedgehog (Shh) is present in MPs generated from activated/apoptotic human T lymphocytes [Martinez et al., Blood (2006) vol. 108, 3012–3020]. We show here that Shh carried by MPs induces nitric oxide (NO) release from endothe‐lial cells, triggers changes in the expression and phos‐phorylation of enzymes related to the NO pathway, and decreases production of reactive oxygen species. When PI3‐kinase and ERK signaling were specifically inhibited, the effects of MPs were reversed. In vivo injection of MPs in mice was also able to improve endothelial function by increasing NO release, and it reversed endothelial dysfunction after ischemia/reperfusion. Silencing the effects of Shh with cyclopamine, a specific inhibitor of Shh, or siRNA, an inhibitor of the Shh receptor Patched, strongly reduced production of NO elicited by MPs. Taken together, we propose that the biological message carried by MPs harboring Shh may represent a new therapeutic approach against endothe‐lial dysfunction during acute severe endothelial injury.—Agouni A., Mostefai, H. A., Porro, C., Carusio, N., Favre, J., Richard, V., Henrion, D., Martinez, M. C., Andriantsitohaina R. Sonic hedgehog carried by micro‐particles corrects endothelial injury through nitric oxide release. FASEB J. 21, 2735–2741 (2007)

Circulating Microparticles from Patients with Septic Shock Exert Protective Role in Vascular Function

RATIONALEnSepsis is an archetypal condition with molecular links between inflammation and coagulation. Both events can be orchestrated by the interaction between circulating and vascular cells that under activation release microparticles.nnnOBJECTIVESnWe characterized circulating microparticles from both nonseptic subjects and patients with septic shock and evaluated their contribution to vascular function.nnnMETHODSnCirculating microparticles and their cell origin were measured in blood from 36 patients with septic shock and 18 nonseptic subjects by flow cytometry. Microparticles were then injected intravenously into mice and vascular reactivity was assessed in aorta. Expression and activity of enzymes involved in nitric oxide (NO) and cyclooxygenase metabolite production were analyzed.nnnMEASUREMENTS AND MAIN RESULTSnCirculating levels of microparticles and platelet- and endothelial-derived microparticles were increased in septic patients. Surprisingly, septic microparticles enhanced the sensitivity of contraction of mouse aorta in response to serotonin. Interestingly, septic microparticles enhanced the contraction of aorta from lipopolysaccharide-treated mice. This effect was linked neither to increased calcium entry nor to Rho kinase inhibitor-sensitive mechanisms. In addition, the effect of septic microparticles was not modified either by NO-synthase or cyclooxygenase-2 inhibitors, and was not associated with NO or O2- overproduction. The nonselective cyclooxygenase-2 inhibitor indomethacin reduced, and the specific thromboxane A2 antagonist SQ-29548 abolished, aortic contraction in mice treated with nonseptic and septic microparticles. The effect of septic microparticles was associated with increased thromboxane A2 production, and was sensitive to a selective thromboxane A2 antagonist.nnnCONCLUSIONSnWe provide evidence that increased circulating microparticles are protective against vascular hyporeactivity accounting for hypotension in patients with septic shock.

Red wine polyphenols prevent metabolic and cardiovascular alterations associated with obesity in Zucker fatty rats (Fa/Fa).

Background Obesity is associated with increased risks for development of cardiovascular diseases. Epidemiological studies report an inverse association between dietary flavonoid consumption and mortality from cardiovascular diseases. We studied the potential beneficial effects of dietary supplementation of red wine polyphenol extract, Provinols™, on obesity-associated alterations with respect to metabolic disturbances and cardiovascular functions in Zucker fatty (ZF) rats. Methodology/Principal Findings ZF rats or their lean littermates received normal diet or supplemented with Provinols™ for 8 weeks. Provinols™ improved glucose metabolism by reducing plasma glucose and fructosamine in ZF rats. Moreover, it reduced circulating triglycerides and total cholesterol as well as LDL-cholesterol in ZF rats. Echocardiography measurements demonstrated that Provinols™ improved cardiac performance as evidenced by an increase in left ventricular fractional shortening and cardiac output associated with decreased peripheral arterial resistances in ZF rats. Regarding vascular function, Provinols™ corrected endothelial dysfunction in aortas from ZF rats by improving endothelium-dependent relaxation in response to acetylcholine (Ach). Provinols™ enhanced NO bioavailability resulting from increased nitric oxide (NO) production through enhanced endothelial NO-synthase (eNOS) activity and reduced superoxide anion release via decreased expression of NADPH oxidase membrane sub-unit, Nox-1. In small mesenteric arteries, although Provinols™ did not affect the endothelium-dependent response to Ach; it enhanced the endothelial-derived hyperpolarizing factor component of the response. Conclusions/Significance Use of red wine polyphenols may be a potential mechanism for prevention of cardiovascular and metabolic alterations associated with obesity.

Phosphatidylinositol 3-Kinase and Xanthine Oxidase Regulate Nitric Oxide and Reactive Oxygen Species Productions by Apoptotic Lymphocyte Microparticles in Endothelial Cells

Microparticles (MPs) are membrane vesicles released during cell activation and apoptosis. We have previously shown that MPs from apoptotic T cells induce endothelial dysfunction, but the mechanisms implicated are not completely elucidated. In this study, we dissect the pathways involved in endothelial cells with respect to both NO and reactive oxygen species (ROS). Incubation of endothelial cells with MPs decreased NO production that was associated with overexpression and phosphorylation of endothelial NO synthase (eNOS). Also, MPs enhanced expression of caveolin-1 and decreased its phosphorylation. Microparticles enhanced ROS by a mechanism sensitive to xanthine oxidase and P-IκBα inhibitors. PI3K inhibition reduced the effects of MPs on eNOS, but not on caveolin-1, whereas it enhanced the effects of MPs on ROS production. Microparticles stimulated ERK1/2 phosphorylation via a PI3K-depedent mechanism. Inhibition of MEK reversed eNOS phosphorylation but had no effect on ROS production induced by MPs. In vivo injection of MPs in mice impaired endothelial function. In summary, MPs activate pathways related to NO and ROS productions through PI3K, xanthine oxidase, and NF-κB pathways. These data underscore the pleiotropic effects of MPs on NO and ROS, leading to an increase oxidative stress that may account for the deleterious effects of MPs on endothelial function.

Endothelial Dysfunction and Circulating Microparticles from Patients with Obstructive Sleep Apnea

Endothelial dysfunction is involved in vascular complications of obstructive sleep apnea (OSA). In this study, circulating microparticles (MPs) from patients with OSA-induced nocturnal desaturations were characterized and their effects on endothelial function were evaluated. Two age-matched groups of patients undergoing polysomnography for OSA were compared: 35 desaturators with a 3% oxyhemoglobin desaturation index (ODI) > or = 10 events per hour of sleep and 27 nondesaturators with ODI <10 events per hour. MPs were characterized by flow cytometry and then either used to treat in vitro human endothelial cells or to study endothelial function in mice. Circulating MPs did not differ between groups, but MPs from granulocytes and activated leukocytes (CD62L(+)) were found at higher levels in desaturators. In vitro, MPs from desaturators reduced endothelial nitric oxide (NO) production by enhancing phosphorylation of endothelial NO synthase at the site of inhibition and expression of caveolin-1. CD62L(+) MPs positively correlated with ODI. Endothelial NO production negatively correlated with both CD62L(+) MPs and ODI. MPs from desaturators increased expression of endothelial adhesion molecules including E-selectin, ICAM-1 and ITGA5, and cyclooxygenase 2. Moreover, injection of MPs from desaturators into mice impaired endothelium-dependent relaxation in aorta and flow-induced dilation in small mesenteric arteries. This study demonstrates an association between endothelial dysfunction and increased circulating levels of CD62L(+) MPs. This may initiate atherogenic processes in patients with OSA and severe nighttime hypoxia.

Role of Gi/o-Src kinase-PI3K/Akt pathway and caveolin-1 in β2-adrenoceptor coupling to endothelial NO synthase in mouse pulmonary artery

Activation of the β₂-adrenoceptor (β₂-AR) elicits an endothelial nitric oxide synthase (eNOS)-dependent relaxation in mouse pulmonary artery, which, contrary to the muscarinic receptor-dependent relaxation, is preserved in hypoxic pulmonary arterial hypertension. We therefore characterized the signaling pathways underlying the β₂-AR-mediated eNOS activation, with special focus on G(i/o) proteins, protein kinases and caveolae. Functional studies (for evaluation of vasorelaxant response), Western blotting (for assessment of eNOS and caveolin-1 phosphorylation) and transmission electron microscopy (for visualization of caveolae) were conducted in pulmonary arteries from wild-type or caveolin-1 knockout mice. In wild-type isolated arteries, relaxation to the selective β₂-AR agonist procaterol was reduced by inhibitors of G(i/o) proteins (pertussis toxin, PTX), phosphatidylinositol 3-kinase (PI3K; wortmannin or LY 294002), Akt (Akt inhibitor X) and Src-kinase (PP2) and by cholesterol depletion (using methyl-β-cyclodextrin). Procaterol induced eNOS phosphorylation at Ser(1177), which was prevented by PTX, PP2 or Akt inhibitor. Procaterol also promoted caveolin-1 phosphorylation at Tyr(14), which was decreased by PTX or PP2. Caveolin-1 gene deletion resulted in endothelial caveolae disruption in mouse pulmonary artery and in potentiation of procaterol-induced relaxation. Unlike procaterol, acetylcholine-induced relaxation was unaffected by PTX, methyl-β-cyclodextrin or caveolin-1 gene deletion. To conclude, the mouse pulmonary endothelial β₂-AR is coupled to a G(i/o)-Src kinase-PI3K/Akt pathway to promote eNOS phosphorylation at Ser(1177) leading to a NO-dependent vasorelaxation. Caveolin-1 exerts a negative control on this response that is abrogated by its phosphorylation at Tyr(14), through a G(i/o)-Src kinase pathway. Since pulmonary β₂-AR- and muscarinic receptor-mediated relaxations differentiate in their respective signaling pathways leading to eNOS activation and sensitivities during hypoxia-induced pulmonary arterial hypertension, mechanisms underlying eNOS activation might be key determinants of pulmonary endothelial dysfunction.

Microparticles from apoptotic monocytes enhance nitrosative stress in human endothelial cells.

Microparticles are membrane vesicles with procoagulant and proinflammatory properties released during cell activation or apoptosis. Microparticles from monocytes have been implicated in atherosclerosis and vascular inflammation, but their direct effects on endothelial cells are not completely elucidated. The present study was designed to dissect the signaling pathways of monocytic microparticles in endothelial cells with respect to both NO pathway and reactive oxygen species. Microparticles were produced by treatment of human monocytic cell line THP‐1 with the apoptotic agent VP‐16. Human endothelial cells were treated with monocytic microparticles and then, we studied their effects on nitrosative and oxidative stresses. Incubation of human endothelial cells with microparticles enhanced the production of NO without affecting superoxide anions generation. Microparticles did not affect endothelial NO synthase expression and its phosphorylation. Interestingly, microparticles decreased caveolin‐1 expression and increased its phosphorylation. Inhibition of PI‐3‐kinase or MEK1/2 reversed the effects of microparticles on caveolin‐1 expression but not its phosphorylation. Moreover, microparticles increased nitration of several proteins, reflecting peroxynitrite production, which was prevented by blockade of PI‐3‐kinase pathway. In summary, monocyte microparticles active multiple pathways related to nitrosative stress in endothelial cells including both PI‐3‐kinase and ERK1/2 in the regulation of caveolin‐1 expression. These data underscore the pleiotropic effect of microparticles on endothelial cells and suggest that they probably play a critical role on vascular function.

Microparticles as biomarkers of vascular dysfunction in metabolic syndrome and its individual components

Heterogeneous in size (0.1-1 µm), microparticles are small membrane vesicles released from activated and/or apoptotic cells. Although described since 1967 by Wolf, it is only since the 1990s that microparticles have been considered as biomarkers as well as potential mediators of biological messages between cells by acting as paracrine and endocrine vectors. Detection of microparticles has been performed in biological fluids (blood, synovial fluid, saliva for instance) and some solid tissues but also from the culture medium. Levels of circulating microparticles are enhanced in a large number of pathological states including cardiovascular and metabolic disorders associated with insulin resistance and this has been linked to deleterious effects on cells from the vascular wall, mainly, endothelial cells. This review highlights the increasing impact of microparticles in major cardiovascular pathological situations associated with metabolic derangements.