Pulmonary arterial hypertension (PAH) remains a disease with limited therapeutic options and dismal prognosis. Despite its etiologic heterogeneity, the underlying unifying pathophysiology is characterized by increased vascular tone and adverse remodeling of the pulmonary circulation. Myeloperoxidase (MPO), an enzyme abundantly expressed in neutrophils, has potent vasoconstrictive and profibrotic properties, thus qualifying as a potential contributor to this disease. Here, we sought to investigate whether MPO is causally linked to the pathophysiology of PAH. Investigation of 2 independent clinical cohorts revealed that MPO plasma levels were elevated in subjects with PAH and predicted adverse outcome. Experimental analyses showed that, upon hypoxia, right ventricular pressure was less increased in Mpo-/- than in WT mice. The hypoxia-induced activation of the Rho-kinase pathway, a critical subcellular signaling pathway yielding vasoconstriction and structural vascular remodeling, was blunted in Mpo-/- mice. Mice subjected to i.v. infusion of MPO revealed activation of Rho-kinase and increased right ventricular pressure, which was prevented by coinfusion of the Rho-kinase inhibitor Y-27632. In the Sugen5416/hypoxia rat model, PAH was attenuated by the MPO inhibitor AZM198. The current data demonstrate a tight mechanistic link between MPO, the activation of Rho-kinase, and adverse pulmonary vascular function, thus pointing toward a potentially novel avenue of treatment.
- MeSH
- amidy aplikace a dávkování MeSH
- arteria pulmonalis patologie patofyziologie MeSH
- dospělí MeSH
- hypoxie krev etiologie patologie MeSH
- intravenózní infuze MeSH
- Kaplanův-Meierův odhad MeSH
- kinázy asociované s rho antagonisté a inhibitory metabolismus MeSH
- kohortové studie MeSH
- krysa rodu rattus MeSH
- lidé středního věku MeSH
- lidé MeSH
- modely nemocí na zvířatech MeSH
- myši inbrední C57BL MeSH
- myši knockoutované MeSH
- myši MeSH
- peroxidasa aplikace a dávkování krev metabolismus MeSH
- plíce patologie MeSH
- plicní hypertenze krev mortalita patologie patofyziologie MeSH
- potkani Sprague-Dawley MeSH
- pyridiny aplikace a dávkování MeSH
- rekombinantní proteiny aplikace a dávkování krev metabolismus MeSH
- remodelace cév účinky léků fyziologie MeSH
- vazokonstrikce účinky léků fyziologie MeSH
- zvířata MeSH
- Check Tag
- dospělí MeSH
- krysa rodu rattus MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
RATIONALE: Ventricular arrhythmias remain the leading cause of death in patients suffering myocardial ischemia. Myeloperoxidase, a heme enzyme released by polymorphonuclear neutrophils, accumulates within ischemic myocardium and has been linked to adverse left ventricular remodeling. OBJECTIVE: To reveal the role of myeloperoxidase for the development of ventricular arrhythmias. METHODS AND RESULTS: In different murine models of myocardial ischemia, myeloperoxidase deficiency profoundly decreased vulnerability for ventricular tachycardia on programmed right ventricular and burst stimulation and spontaneously as assessed by ECG telemetry after isoproterenol injection. Experiments using CD11b/CD18 integrin-deficient (CD11b(-/-)) mice and intravenous myeloperoxidase infusion revealed that neutrophil infiltration is a prerequisite for myocardial myeloperoxidase accumulation. Ventricles from myeloperoxidase-deficient (Mpo(-/-)) mice showed less pronounced slowing and decreased heterogeneity of electric conduction in the peri-infarct zone than wild-type mice. Expression of the redox-sensitive gap junctional protein Cx43 (Connexin 43) was reduced in the peri-infarct area of wild-type compared with Mpo(-/-) mice. In isolated wild-type cardiomyocytes, Cx43 protein content decreased on myeloperoxidase/H2O2 incubation. Mapping of induced pluripotent stem cell-derived cardiomyocyte networks and in vivo investigations linked Cx43 breakdown to myeloperoxidase-dependent activation of matrix metalloproteinase 7. Moreover, Mpo(-/-) mice showed decreased ventricular postischemic fibrosis reflecting reduced accumulation of myofibroblasts. Ex vivo, myeloperoxidase was demonstrated to induce fibroblast-to-myofibroblast transdifferentiation by activation of p38 mitogen-activated protein kinases resulting in upregulated collagen generation. In support of our experimental findings, baseline myeloperoxidase plasma levels were independently associated with a history of ventricular arrhythmias, sudden cardiac death, or implantable cardioverter-defibrillator implantation in a cohort of 2622 stable patients with an ejection fraction >35% undergoing elective diagnostic cardiac evaluation. CONCLUSIONS: Myeloperoxidase emerges as a crucial mediator of postischemic myocardial remodeling and may evolve as a novel pharmacological target for secondary disease prevention after myocardial ischemia.
- MeSH
- ischemická choroba srdeční metabolismus patologie MeSH
- kardiomyocyty metabolismus patologie MeSH
- kultivované buňky MeSH
- lidé MeSH
- myši inbrední C57BL MeSH
- myši knockoutované MeSH
- myši MeSH
- orgánové kultury - kultivační techniky MeSH
- peroxidasa nedostatek MeSH
- remodelace komor fyziologie MeSH
- srdeční arytmie metabolismus patologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Myeloperoxidase (MPO) is a heme enzyme abundantly expressed in polymorphonuclear neutrophils. MPO is enzymatically capable of catalyzing the generation of reactive oxygen species (ROS) and the consumption of nitric oxide (NO). Thus MPO has both potent microbicidal and, upon binding to the vessel wall, pro-inflammatory properties. Interestingly, MPO - a highly cationic protein - has been shown to bind to both endothelial cells and leukocyte membranes. Given the anionic surface charge of red blood cells, we investigated binding of MPO to erythrocytes. Red blood cells (RBCs) derived from patients with elevated MPO plasma levels showed significantly higher amounts of MPO by flow cytometry and ELISA than healthy controls. Heparin-induced MPO-release from patient-derived RBCs was significantly increased compared to controls. Ex vivo experiments revealed dose and time dependency for MPO-RBC binding, and immunofluorescence staining as well as confocal microscopy localized MPO-RBC interaction to the erythrocyte plasma membrane. NO-consumption by RBC-membrane fragments (erythrocyte "ghosts") increased with incrementally greater concentrations of MPO during incubation, indicating preserved catalytic MPO activity. In vivo infusion of MPO-loaded RBCs into C57BL/6J mice increased local MPO tissue concentrations in liver, spleen, lung, and heart tissue as well as within the cardiac vasculature. Further, NO-dependent relaxation of aortic rings was altered by RBC bound-MPO and systemic vascular resistance significantly increased after infusion of MPO-loaded RBCs into mice. In summary, we find that MPO binds to RBC membranes in vitro and in vivo, is transported by RBCs to remote sites in mice, and affects endothelial function as well as systemic vascular resistance. RBCs may avidly bind circulating MPO, and act as carriers of this leukocyte-derived enzyme.
- MeSH
- akutní koronární syndrom krev patologie MeSH
- aorta účinky léků MeSH
- biologický transport MeSH
- cévní endotel účinky léků MeSH
- cévní rezistence účinky léků MeSH
- erytrocyty metabolismus patologie MeSH
- heparin chemie MeSH
- kultivované buňky MeSH
- lidé MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- orgánové kultury - kultivační techniky MeSH
- oxid dusnatý metabolismus farmakologie MeSH
- peroxidasa krev farmakologie MeSH
- srdce účinky léků MeSH
- srdeční selhání krev patologie MeSH
- techniky tkáňových kultur MeSH
- vazba proteinů MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: Myeloperoxidase (MPO) is an abundant hemoprotein expressed by neutrophil granulocytes that is recognized to play an important role in the development of vascular diseases. Upon degranulation from circulating neutrophil granulocytes, MPO binds to the surface of endothelial cells in an electrostatic-dependent manner and undergoes transcytotic migration to the underlying extracellular matrix (ECM). However, the mechanisms governing the binding of MPO to subendothelial ECM proteins, and whether this binding modulates its enzymatic functions are not well understood. METHODS: We investigated MPO binding to ECM derived from aortic endothelial cells, aortic smooth muscle cells, and fibroblasts, and to purified ECM proteins, and the modulation of these associations by glycosaminoglycans. The oxidizing and chlorinating potential of MPO upon binding to ECM proteins was tested. RESULTS: MPO binds to the ECM proteins collagen IV and fibronectin, and this association is enhanced by the pre-incubation of these proteins with glycosaminoglycans. Correspondingly, an excess of glycosaminoglycans in solution during incubation inhibits the binding of MPO to collagen IV and fibronectin. These observations were confirmed with cell-derived ECM. The oxidizing and chlorinating potential of MPO was preserved upon binding to collagen IV and fibronectin; even the potentiation of MPO activity in the presence of collagen IV and fibronectin was observed. CONCLUSIONS: Collectively, the data reveal that MPO binds to ECM proteins on the basis of electrostatic interactions, and MPO chlorinating and oxidizing activity is potentiated upon association with these proteins. GENERAL SIGNIFICANCE: Our findings provide new insights into the molecular mechanisms underlying the interaction of MPO with ECM proteins.
- MeSH
- cévní endotel cytologie metabolismus MeSH
- dimerizace MeSH
- dusičnany metabolismus MeSH
- extracelulární matrix - proteiny chemie metabolismus MeSH
- fibronektiny metabolismus MeSH
- glykosaminoglykany metabolismus MeSH
- kolagen typu IV metabolismus MeSH
- kultivované buňky MeSH
- lidé MeSH
- oxidační stres MeSH
- peroxidasa metabolismus MeSH
- tyrosin metabolismus MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
