Abderahim Gaceb

Extracellular vesicles: new players in cardiovascular diseases.

Extracellular vesicles, particles released by all cell types, represent a new way to convey information between cells such as proteins, second messengers, and genetic information to modify the phenotype and function of the target cells. Recent data suggest that extracellular vesicles play a crucial role in both physiology and pathology, including coagulation, angiogenesis, cell survival, modulation of the immune response, and inflammation. Thus extracellular vesicles participate in the processes of cardiovascular diseases from atherosclerosis, myocardial infarction to heart failure. Consequently, extracellular vesicles can potentially be exploited for therapy, prognosis, and biomarkers for health and disease. This review focuses on the role of extracellular vesicles in the development of cardiovascular diseases, as well as the deleterious and beneficial effects that they may provide in vascular cells and myocardium.

Microparticles as regulators of cardiovascular inflammation.

Microparticles are a heterogeneous group of membrane-coated vesicles that can act as signaling elements in the inflammatory processes. Once released from cells by membrane blebbing, microparticles become efficient vectors that exchange biological information between cells. Detectable in small amounts in peripheral blood of healthy individuals, elevated concentrations of microparticles originating from platelet, leukocyte, erythrocyte, and endothelial lineages are associated with a variety of pathophysiological conditions, including thrombosis, inflammation, sepsis, and metabolic disorders. This review summarizes the role of microparticles in modulating inflammation during cardiovascular diseases.

Circulating microparticles from patients with obstructive sleep apnea enhance vascular contraction: mandatory role of the endothelium.

Obstructive sleep apnea (OSA) is characterized by repetitive apnea-hypopnea cycles during sleep associated with oxygen desaturation and sleep disruption. We evaluated the role of circulating microparticles (MPs) from patients with OSA in the regulation of vascular function. MPs from whole blood from patients with OSA or control subjects were injected i.v. into mice. Injection of MPs from patients with OSA induced ex vivo vascular hyperreactivity in aortas with functional endothelium but, in contrast, hyporeactivity in vessels without functional endothelium. Vascular hyperreactivity was blunted in the presence of a nitric oxide synthase inhibitor alone or combined with the cyclooxygenase inhibitor indomethacin. MPs from patients with OSA reduced endothelial nitric oxide synthase activity and nitric oxide production, increased aortic cyclooxygenase-1 and cyclooxygenase-2 expression, and increased thromboxane A(2) and prostacyclin production. Blockade of thromboxane A(2) receptor did not affect the serotonin response in arteries from OSA MP-treated mice. A superoxide dismutase mimetic reduced the vascular hyperreactivity induced by MPs from patients with OSA but had no effect on contraction in vessels from control and non-OSA MP-treated mice. These data provide evidence that circulating MPs from patients with OSA induce ex vivo vascular hyperreactivity with the obligatory role of the endothelium and subtle interactions between the nitric oxide and cyclooxygenase pathways and metabolites. These results highlight the participation of MPs in vascular dysfunction associated with OSA.

PPARα Regulates Endothelial Progenitor Cell Maturation and Myeloid Lineage Differentiation Through a NADPH Oxidase-Dependent Mechanism in Mice

Peroxisome proliferator‐activated receptor‐alpha (PPARα) is a key modulator of lipid metabolism. Here, we propose that PPARα regulates the maturation and function of bone marrow (BM) progenitor cells. Although PPARα deletion increased the number of BM‐resident cells and the differentiation of endothelial progenitor cells (EPCs) and monocytic progenitor cells, it impaired re‐endothelialization of injured carotid artery that was associated with reduced circulating EPCs. Also, PPARα deletion diminished the in vivo proangiogenic effect of PPARα agonist without affecting EPC differentiation markers. Macrophage colony‐stimulating factor treatment increased the population of monocytic progenitor cells as well as secretome of BM‐derived cells in PPARα wild‐type but not in knockout mice. In addition, PPARα‐null mice displayed reduced lymphocytes and increased monocytes and neutrophils in the blood. Furthermore, PPARα‐null mice exhibited increments in the number of total cells (as well as of phenotypically distinct subpopulations of lymph node cells) but also a significant alteration in the number of various subpopulations of splenocytes and thymocytes. Finally, PPARα negatively regulated reactive oxygen species derived by NADPH oxidase in BM‐resident progenitor cells. Taken together, our data provide evidence that PPARα is a critical regulator of recruitment, homing, and maturation of BM‐derived progenitor cells. Stem Cells 2015;33:1292–1303

Vascular and hepatic impact of short-term intermittent hypoxia in a mouse model of metabolic syndrome.

Background Experimental models of intermittent hypoxia (IH) have been developed during the last decade to investigate the consequences of obstructive sleep apnea. IH is usually associated with detrimental metabolic and vascular outcomes. However, paradoxical protective effects have also been described depending of IH patterns and durations applied in studies. We evaluated the impact of short-term IH on vascular and metabolic function in a diet-induced model of metabolic syndrome (MS). Methods Mice were fed either a standard diet or a high fat diet (HFD) for 8 weeks. During the final 14 days of each diet, animals were exposed to either IH (1 min cycle, FiO2 5% for 30s, FiO2 21% for 30s; 8 h/day) or intermittent air (FiO2 21%). Ex-vivo vascular reactivity in response to acetylcholine was assessed in aorta rings by myography. Glucose, insulin and leptin levels were assessed, as well as serum lipid profile, hepatic mitochondrial activity and tissue nitric oxide (NO) release. Results Mice fed with HFD developed moderate markers of dysmetabolism mimicking MS, including increased epididymal fat, dyslipidemia, hepatic steatosis and endothelial dysfunction. HFD decreased mitochondrial complex I, II and IV activities and increased lactate dehydrogenase (LDH) activity in liver. IH applied to HFD mice induced a major increase in insulin and leptin levels and prevented endothelial dysfunction by restoring NO production. IH also restored mitochondrial complex I and IV activities, moderated the increase in LDH activity and liver triglyceride accumulation in HFD mice. Conclusion In a mouse model of MS, short-term IH increases insulin and leptin levels, restores endothelial function and mitochondrial activity and limits liver lipid accumulation.

Increased monocyte/neutrophil and pro-coagulant microparticle levels and overexpression of aortic endothelial caveolin-1β in dyslipidemic sand rat, Psammomys obesus

AIMS To compare the effects of a high-energy diet (HED) with those of a low-energy diet (LED) on biochemical parameters, microparticle (MP) subpopulations and endothelial caveolin-1 (cav-1) protein expression in Psammomys obesus (P. obesus). METHODS After 12weeks of feeding with either the HED or LED, fasting plasma glucose and lipid parameters were measured using an enzymatic colorimetric kit while serum insulin concentration was determined with radioimmunoassay kits. MP subpopulations and cav-1 protein expression were quantified using flow cytometry and western blot analysis, respectively. RESULTS We observed that the HED caused a marked increase in lipid parameters, even in normoglycemic P. obesus. The total number of circulating MPs and the numbers of platelet-, leukocyte-, and erythrocyte-derived MPs were unaltered in the HED group. However, the HED induced increases in the numbers of monocytes/neutrophils and procoagulant MPs and a decrease in the endothelial MP levels. Cav-1β protein expression and reactive oxygen species production were increased in the vascular endothelium of HED-treated P. obesus. CONCLUSION From these findings, it is indicated that the HED exerts deleterious effects on the vascular system by increasing the monocyte/neutrophil and procoagulant MP levels, which may lead to cav-1β protein overexpression in dyslipidemic P. obesus.

Activation of Endothelial Pro-resolving Anti-Inflammatory Pathways by Circulating Microvesicles from Non-muscular Myosin Light Chain Kinase-Deficient Mice

Microvesicles, small membrane vesicles released from cells, have beneficial and/or deleterious effects in sepsis. We previously reported that non-muscle myosin light chain kinase (nmMLCK) deletion protects mice against endotoxic shock by reducing inflammation. Here, we have evaluated the consequences of nmMLCK deletion on microvesicle phenotypes and their effects on mouse aortic endothelial cells in association with vascular inflammation and endothelial dysfunction during endotoxic shock induced by lipopolysaccharide in mice. Treatment with lipopolysaccharide induced an increase in levels of circulating microvesicles in wild type but not in nmMLCK-deficient mice. Microvesicles from nmMLCK-deficient mice (MVsnmMLCK-/-) prevented the inflammatory effects of lipopolysaccharide with concomitant increase of anti- inflammatory and reduction of pro-inflammatory secretome in mouse aortic endothelial cells. In addition, MVsnmMLCK-/- reduced the efficacy of lipopolysaccharide to increase aortic oxidative and nitrosative stresses as well as macrophage infiltration in the aorta. Moreover, MVsnmMLCK-/- prevented ex vivo endothelial dysfunction, vascular hyporeactivity, and in vivo overproduction of nitric oxide in heart and liver in response to lipopolysaccharide. Altogether, these findings provide evidence that nmMLCK deletion generates circulating microvesicles displaying protective effects by activating endothelial pro-resolving anti-inflammatory pathways allowing the effective down-regulation of oxidative and nitrative stresses associated with endotoxic shock. Thus, nmMLCK plays a pivotal role in susceptibility to sepsis via the control of cellular activation and release of circulating microvesicles.