Rationale: 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.

Thrombosis is the defining feature of the most prevalent causes of cardiovascular mortality, such as myocardial infarction, stroke, and pulmonary artery embolism. Although platelet activation and activation of the plasmatic coagulation system are the hallmarks of thrombus formation, inflammatory processes and the cellular responses involved are increasingly being recognized as critical modulators of thrombosis. In the context of many chronic inflammatory diseases that are associated with a high thrombotic risk, oxidized lipoproteins represent a prominent sterile trigger of inflammation. Oxidized low-density lipoprotein and its components play a central role in the initiation and progression of atherosclerotic plaques, but also in other processes that lead to thrombotic events. Moreover, dying cells and microvesicles can be decorated with some of the same oxidized lipid components that are found on oxidized lipoproteins, and thereby similar mechanisms of thromboinflammation may also be active in venous thrombosis. In this review, we summarize the current knowledge on how oxidized lipoproteins and components thereof affect the cells and pathways involved in thrombosis.

Atherosclerotic cardiovascular disease (CVD) is the leading cause of mortality worldwide 1,2 . Atherosclerotic plaque formation is initiated upon trapping of low-density lipoprotein (LDL) in the subendothelial space of large and medium size arteries that initially involves binding of LDL to heparan-sulfate proteoglycans (HSPGs) 3 , followed by a chronic inflammation and remodelling of the artery wall 3 . A Proliferation Inducing Ligand (APRIL), a cytokine produced by many cell types, binds to HSPGs 4 , but the physiology of this interaction is largely unknown. Here, we show that genetic ablation or antibody-mediated depletion of APRIL aggravates atherosclerosis in mice.Mechanistically, we demonstrate that APRIL confers atheroprotection via binding to heparan sulfate (HS) chains of heparan-sulfate proteoglycan 2 (HSPG2), which limits LDL retention, macrophage accumulation and necrotic core formation. Indeed, antibody-mediated depletion of APRIL in mice expressing HS-deficient HSPG2 had no effect on atherosclerosis development.Consistent with these data, treatment with a specific anti-APRIL antibody that promotes the binding of APRIL to HSPGs reduces experimental atherosclerosis. Furthermore, the serum levels of a previously unknown form of human APRIL protein that binds to HSPGs, which we termed non-canonical APRIL (nc-APRIL), are associated independently of traditional risk factors with long term (10-to 12-year follow up) cardiovascular mortality in patients with atherosclerosis. Our data reveal hitherto unknown properties of APRIL that have broad pathophysiological implications for vascular homeostasis.