Mitochondria are a subset of extracellular vesicles released by stressed monocytes and induce inflammatory responses in endothelial cells

Mikrovesikel sind eine wichtige Untergruppe extrazellulärer Vesikel, welche vermehrt als wichtige Bestandteile interzellulärer Kommunikation in Herz- und Kreislauferkrankungen wahrgenommen werden. Es wird angenommen, dass ihre biologische Aktivität, einschließlich ihrer Fähigkeit Entzündungen auszulösen, von ihrer Zusammensetzung bestimmt wird. Im Kreislaufsystem ist die Kommunikation zwischen Monozyten und Endothelzellen ein essentieller Bestandteil der Weiterverbreitung von Entzündungssignalen. Welche Rolle Mikrovesikel in diesem Kontext spielen ist jedoch kaum bekannt. In dieser Dissertation habe ich die Beschaffenheit von Mikrovesikel, die von gestressten monozytischen Zellen freigesetzt wurden, untersucht. Weiters, habe ich analysiert welche zellulärer Antwort diese Mikrovesikel in Endothelzellen auslösen und wodurch ihre biologische Aktivität bestimmt wird. Ich konnte zeigen, dass LPS (Lipopolysaccharid)-aktivierte monozytische Zellen Mitochondrien in freier Form und von Mikrovesikeln umhüllt sezernieren. Diese freigesetzten Mitochondrien und direkt aus aktivierten Monozyten isolierte Mitochondrien, so wie Mikrovesikel, isoliert aus dem Plasma von Individuen, welche niedrig dosierte LPS-Injektionen erhalten hatten, induzierten TNF (Tumornekrosefaktor) und Typ I IFN (Interferon) Signalwege in Endothelzellen. Weiters beobachtete ich, dass zwei Komponenten für diese biologische Aktivität der Mitochondrien und Mikrovesikel verantwortlich waren: RNA gestresster Mitochondrien und mit Mitochondrien assoziierter TNF, welche jeweils für die induktion der Typ I IFN und TNF Antwort verantwortlich waren. Schließlich konnte ich zeigen, dass das Entzündungspotential isolierter Mitochondrien und freigesetzter Mikrovesikel drastisch verringert war, wenn die Zellatmung in Mutterzellen gehemmt war, oder wenn diese Zellen in Gegenwart eines für Mitochondrien spezifischen Antioxidans oder Pyruvat mit LPS aktiviert wurden. Diese Beobachtungen ließen folgende Schlüsse zu: Erstens, von gestressten Monozyten freigesetzte Mitochondrien (frei bzw. eingebettet in Mikrovesikeln) stellen eine biologisch aktive Untergruppe extrazellulärer Vesikel dar. Zweitens, ihr Potenzial Entzündungsreaktionen in Endothelzellen auszulösen, wird vom Aktivierungszustand der Monozyten, welche die Mikrovesikel freisetzen, bestimmt. Ausgehend von diesen Befunden können von gestressten Zellen freigesetzte Mitochondrien eine wichtige Rolle in entzündlichen Erkrankungen, die mit TNF und Typ I IFN Signalwegen assoziiert werden, spielen.Microvesicles, a major subtype of extracellular vesicles, have recently gained attention as important mediators of cell-to-cell communication in cardiovascular disease. Their biological activity, including inflammatory properties, is considered to be defined by their composition. Furthermore, communication between monocytes and endothelial cells is an essential component to propagate inflammatory responses in the circulation. However, little is known about the role of microvesicles in this context. In this thesis, I studied the content of microvesicles released from stressed monocytic cells and their biological activity towards endothelial cells, as well as what defines this activity. I could show that LPS (Lipopolysaccharide)-activated monocytic cells release microvesicle-encapsulated and free mitochondria. Notably, mitochondria released in free form or embedded in microvesicles, as well as mitochondria directly isolated from LPS-activated cells and circulating microvesicles isolated from donors receiving low-dose LPS-injections, induced TNF (tumor necrosis factor) and type I IFN (interferon) responses in endothelial cells. RNA from stressed mitochondria and TNF-associated with mitochondria were identified as the principal components mediating this effect. Finally, the proinflammatory potential of isolated mitochondria and released microvesicles was dramatically reduced when they were released from nonrespiring cells or when these cells had been cultured in presence of a mitochondrial ROS (reactive oxygen species) scavenger or pyruvate. In conclusion, free mitochondria and microvesicle-encapsulated mitochondria are a biologically active subset of extracellular vesicles released by stressed monocytic cells. Moreover, their potential to induce proinflammatory responses in endothelial cells was determined by the activation status of their parental cells. Therefore, mitochondria released by stressed cells may represent important intercellular mediators in inflammatory diseases associated with TNF and type I IFN signaling.Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersArbeit an der Bibliothek noch nicht eingelangt - Daten nicht geprüftMedizinische Universität Wien, Diss., 2019(VLID)443811

Platelet reactivity to thrombin differs between patients with COVID-19 and those with ARDS unrelated to COVID-19.

In addition to preserving homeostasis and contributing to immunity, platelets may exhibit a dysregulated state in acute respiratory distress syndrome (ARDS), and potentially exacerbate lung injury. Although thrombocytopenia has been associated with increased mortality in ARDS and particularly in H1N1 influenza-infected patients, analysis of quantitative changes in platelet activation levels in ARDS, and how these may differ between the various etiologies of ARDS remains limited.non

Mitochondria Are a Subset of Extracellular Vesicles Released by Activated Monocytes and Induce Type I IFN and TNF Responses in Endothelial Cells.

Extracellular vesicles, including microvesicles, are increasingly recognized as important mediators in cardiovascular disease. The cargo and surface proteins they carry are considered to define their biological activity, including their inflammatory properties. Monocyte to endothelial cell signaling is a prerequisite for the propagation of inflammatory responses. However, the contribution of microvesicles in this process is poorly understood. OBJECTIVE: To elucidate the mechanisms by which microvesicles derived from activated monocytic cells exert inflammatory effects on endothelial cells. METHODS AND RESULTS: LPS (lipopolysaccharide)-stimulated monocytic cells release free mitochondria and microvesicles with mitochondrial content as demonstrated by flow cytometry, quantitative polymerase chain reaction, Western Blot, and transmission electron microscopy. Using RNAseq analysis and quantitative reverse transcription-polymerase chain reaction, we demonstrated that both mitochondria directly isolated from and microvesicles released by LPS-activated monocytic cells, as well as circulating microvesicles isolated from volunteers receiving low-dose LPS-injections, induce type I IFN (interferon), and TNF (tumor necrosis factor) responses in endothelial cells. Depletion of free mitochondria significantly reduced the ability of these microvesicles to induce type I IFN and TNF-dependent genes. We identified mitochondria-associated TNFα and RNA from stressed mitochondria as major inducers of these responses. Finally, we demonstrated that the proinflammatory potential of microvesicles and directly isolated mitochondria were drastically reduced when they were derived from monocytic cells with nonrespiring mitochondria or monocytic cells cultured in the presence of pyruvate or the mitochondrial reactive oxygen species scavenger MitoTEMPO. CONCLUSIONS: Mitochondria and mitochondria embedded in microvesicles constitute a major subset of extracellular vesicles released by activated monocytes, and their proinflammatory activity on endothelial cells is determined by the activation status of their parental cells. Thus, mitochondria may represent critical intercellular mediators in cardiovascular disease and other inflammatory settings associated with type I IFN and TNF signaling