Circulating microparticles from pulmonary hypertensive rats are vectors of oxidative stress

Date du colloque : 04/2010National audienc

Exogenous Transforming Growth Factor-β1 and Its Helminth-Derived Mimic Attenuate the Heart\u27s Inflammatory Response to Ischemic Injury and Reduce Mature Scar Size

\ua9 2024 American Society for Investigative Pathology. Coronary reperfusion after acute ST-elevation myocardial infarction (STEMI) is standard therapy to salvage ischemic heart muscle. However, subsequent inflammatory responses within the infarct lead to further loss of viable myocardium. Transforming growth factor (TGF)-β1 is a potent anti-inflammatory cytokine released in response to tissue injury. The aim of this study was to investigate the protective effects of TGF-β1 after MI. In patients with STEMI, there was a significant correlation (P = 0.003) between higher circulating TGF-β1 levels at 24 hours after MI and a reduction in infarct size after 3 months, suggesting a protective role of early increase in circulating TGF-β1. A mouse model of cardiac ischemia reperfusion was used to demonstrate multiple benefits of exogenous TGF-β1 delivered in the acute phase. It led to a significantly smaller infarct size (30% reduction, P = 0.025), reduced inflammatory infiltrate (28% reduction, P = 0.015), lower intracardiac expression of inflammatory cytokines IL-1β and chemokine (C-C motif) ligand 2 (>50% reduction, P = 0.038 and 0.0004, respectively) at 24 hours, and reduced scar size at 4 weeks (21% reduction, P = 0.015) after reperfusion. Furthermore, a low-fibrogenic mimic of TGF-β1, secreted by the helminth parasite Heligmosomoides polygyrus, had an almost identical protective effect on injured mouse hearts. Finally, genetic studies indicated that this benefit was mediated by TGF-β signaling in the vascular endothelium

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

Circulating microparticles from a rat model of pulmonary arterial hypertension induce endothelial dysfunction

Pulmonary arterial hypertension (PAH) is a rare and severe disease characterized by an increase of pulmonary vascular resistance and right heart failure. Chronic hypoxia induces PAH, which is accompanied by functional (endothelial dysfunction, increased vasoconstriction) and structural (thickening of media) changes in pulmonary arteries. However, the mechanisms of these alterations remain unsolved. Among biological hallmark of this disease, level of circulating microparticles (MPs), small vesicles of plasma membrane released during cell activation and apoptosis, is increased in PAH patients. Although MPs can act as biological vectors of endothelial dysfunction, their role in PAH are not elucidated yet. We studied circulating MP effects on endothelial function during hypoxic PAH. Male Wistar rats were exposed or not to chronic hypoxia (3 weeks, 0.5 atmosphere) and normoxic or hypoxic MPs were isolated from peripheral blood and characterized by flow cytometry. Endothelial cells from rat normoxic aorta or pulmonary arteries were incubated for 24 h with MPs. We studied also effects of in vivo treatment of MPs on vasomotricity, for this, normoxic or hypoxic MPs or vehicle were i.v. injected into rats, and 24 h after, endothelial function were studied. Levels of circulating MPs from hypoxic rats was twice than MPs from normoxic rats (1568 ± 174 vs 852 ± 80 MPs/Âμl of plasma). In vitro treatment of endothelial cells with hypoxic MPs reduced NO production both in aortas and pulmonary arteries ; these effects were associated with enhanced phosphorylation of endothelial NO-synthase at their inhibitory site. By contrast, O2- production was increased only in endothelial cells from pulmonary arteries. In vivo injection of normoxic or hypoxic MPs into rats impaired to the same extent the endotheliumdependent relaxation induced by acetylcholine in aorta. Although pulmonary arteries from rat treated either with normoxic or hypoxic MPs displayed reduction of endothelium-dependent relaxation to carbachol compared to control, the deleterious effect of hypoxic MPs was greater than normoxic MPs. These data provide evidence that hypoxic circulating MPs induce in vitro and in vivo endothelial dysfunction by increasing oxydative stress and by decreasing NO production

Circulating microparticles from pulmonary hypertensive rats induce endothelial dysfunction

RATIONALE: Pulmonary arterial hypertension (PAH) is a severe disease characterized by an increase of pulmonary vascular resistance, which is accompanied by functional and structural changes in pulmonary arteries. Microparticles (MPs) have been described as biological vector of endothelial dysfunction in other pathologies.OBJECTIVES: The purpose of this work was to characterize circulating MPs during hypoxic PAH and to study their effects on endothelial function. METHODS: Male Wistar rats were exposed or not to chronic hypoxia, and normoxic or hypoxic MPs from blood were characterized by flow cytometry. Endothelial cells (ECs) from rat aorta or pulmonary arteries were incubated with MPs, and then expression and phosphorylation of enzymes involved in nitric oxide (NO) and reactive oxygen species productions were analyzed. Hypoxic MPs were injected into rats, and endothelium-dependent relaxation was assessed. MEASUREMENTS AND MAIN RESULTS: Circulating levels of MPs from hypoxic rats were twofold higher than those present in normoxic rats. In vitro treatment of ECs with hypoxic MPs reduced NO production in aortas and pulmonary arteries by enhancing phosphorylation of endothelial NO synthase at the inhibitory site. Hypoxic MPs increased oxidative stress only in pulmonary ECs via xanthine oxidase and mitochondrial implication. In vivo injection of hypoxic MPs into rat impaired endothelium-dependent relaxation both in aorta and pulmonary arteries. CONCLUSIONS: These data provide evidence that hypoxic circulating MPs induce endothelial dysfunction in rat aorta and pulmonary arteries by decreasing NO production. Moreover, MPs display tissue specificity with respect to increased oxidative stress, which occurs only in pulmonary ECs

Loss of endothelial endoglin promotes high-output heart failure through peripheral arteriovenous shunting driven by VEGF signaling

Rationale: ENG (endoglin) is a coreceptor for BMP (bone morphogenetic protein) 9/10 and is strongly expressed in endothelial cells. Mutations in ENG lead to the inherited vascular disorder hereditary hemorrhagic telangiectasia characterized by local telangiectases and larger arteriovenous malformations (AVMs); but how ENG functions to regulate the adult vasculature is not understood. Objective: The goal of the work was to determine how ENG maintains vessel caliber in adult life to prevent AVM formation and thereby protect heart function. Methods and Results: Genetic depletion of endothelial Eng in adult mice led to a significant reduction in mean aortic blood pressure. There was no evidence of hemorrhage, anemia, or AVMs in major organs to explain the reduced aortic pressure. However, large AVMs developed in the peripheral vasculature intimately associated with the pelvic cartilaginous symphysis—a noncapsulated cartilage with a naturally high endogenous expression of VEGF (vascular endothelial growth factor). The increased blood flow through these peripheral AVMs explained the drop in aortic blood pressure and led to increased cardiac preload, and high stroke volumes, ultimately resulting in high-output heart failure. Development of pelvic AVMs in this region of high VEGF expression occurred because loss of ENG in endothelial cells leads to increased sensitivity to VEGF and a hyperproliferative response. Development of AVMs and associated progression to high-output heart failure in the absence of endothelial ENG was attenuated by targeting VEGF signaling with an anti-VEGFR2 (VEGF receptor 2) antibody. Conclusions: ENG promotes the normal balance of VEGF signaling in quiescent endothelial cells to maintain vessel caliber—an essential function in conditions of increased VEGF expression such as local hypoxia or inflammation. In the absence of endothelial ENG, increased sensitivity to VEGF drives abnormal endothelial proliferation in local regions of high VEGF expression, leading to AVM formation and a rapid injurious impact on heart function

Role of the gap junctions in the contractile response to agonists in pulmonary artery from two rat models of pulmonary hypertension

International audienceBackground: Pulmonary hypertension (PH) is characterized by arterial vascular remodelling and alteration in vascular reactivity. Since gap junctions are formed with proteins named connexins (Cx) and contribute to vasoreactivity, we investigated both expression and role of Cx in the pulmonary arterial vasoreactivity in two rat models of PH. Methods: Intrapulmonary arteries (IPA) were isolated from normoxic rats (N), rats exposed to chronic hypoxia (CH) or treated with monocrotaline (MCT). RT-PCR, Western Blot and immunofluorescent labelling were used to study the Cx expression. The role of Cx in arterial reactivity was assessed by using isometric contraction and specific gap junction blockers. Contractile responses were induced by agonists already known to be involved in PH, namely serotonin, endothelin-1 and phenylephrine. Results: Cx 37, 40 and 43 were expressed in all rat models and Cx43 was increased in CH rats. In IPA from N rats only, the contraction to serotonin was decreased after treatment with 37-43Gap27, a specific Cx-mimetic peptide blocker of Cx 37 and 43. The contraction to endothelin-1 was unchanged after incubation with 40Gap27 (a specific blocker of Cx 40) or 37-43Gap27 in N, CH and MCT rats. In contrast, the contraction to phenylephrine was decreased by 40Gap27 or 37-43Gap27 in CH and MCT rats. Moreover, the contractile sensitivity to high potassium solutions was increased in CH rats and this hypersensitivity was reversed following 37-43Gap27 incubation. Conclusion: Altogether, Cx 37, 40 and 43 are differently expressed and involved in the vasoreactivity to various stimuli in IPA from different rat models. These data may help to understand alterations of pulmonary arterial reactivity observed in PH and to improve the development of innovative therapies according to PH aetiology

Transport of small anionic and neutral solutes through chitosan membranes: Dependence on cross-linking and chelation of divalent cations

Chitosan membranes were prepared by solvent casting and cross-linked with glutaraldehyde at several ratios under homogeneous conditions. The cross-linking degree, varying from 0 to 20%, is defined as the ratio between the total aldehyde groups and the amine groups of chitosan. Permeability experiments were conducted using a side-by-side diffusion cell to determine the flux of small molecules of similar size but with different chemical moieties, either ionized (benzoic acid, salicylic acid, and phthalic acid) or neutral (2-phenylethanol) at physiological pH. The permeability of the different model molecules revealed to be dependent on the affinity of those structurally similar molecules to chitosan. The permeability of the salicylate anion was significantly enhanced by the presence of metal cations commonly present in biological fluids, such as calcium and magnesium, but remained unchanged for the neutral 2-phenylethanol. This effect could be explained by the chelation of metal cations on the amine groups of chitosan, which increased the partition coefficient. The cross-linking degree was also correlated with the permeability and partition coefficient. The change in the permeation properties of chitosan to anionic solutes in the presence of these metallic cations is an important result and should be taken into consideration when trying to make in vitro predictions of the drug release from chitosan-based controlled release systems

Living in several languages: Language, gender and identities

Living in several languages encompasses experiencing and constructing oneself differently in each language. The research study on which this article is based takes an intersectional approach to explore insider accounts of the place of language speaking in individuals’ constructions of self, family relationships and the wider context. Twenty-four research interviews and five published autobiographies were analysed using grounded theory, narrative and discursive analysis. A major finding was that learning a new language inducted individuals into somewhat ‘stereotyped’ gendered discourses and power relations within the new language, while also enabling them to view themselves differently in the context of their first language. This embodied process could be challenging and often required reflection and discursive work to negotiate the dissimilarities, discontinuities and contradictions between languages and cultures. However, the participants generally claimed that their linguistic multiplicity generated creativity. Women and men used their language differences differently to ‘perform their gender’. This was particularly evident in language use within families, which involved gendered differences in the choice of language for parenting – despite the fact that both men and women experience their first languages as conveying intimacy in their relationships with their children. The article argues that the notion of ‘mother tongue’ (rather than ‘first language’) is unhelpful in this process as well as in considering the implications of living in several languages for systemic therapy