Many attempts to modulate leukocyte-endothelial interaction to prevent or reduce excessive inflammatory reactions were made in the past. However, the basic regulatory principles of the endothelial inflammatory process remain unclear. It seems that the inhibition of individual components of the inflammatory cascade, for example, by a single antibody against an adhesion molecule, may not be enough to achieve a sustained effect on vascular inflammation.In the past years, microRNAs have been identified as important regulators of gene expression in a wide range of Molecular Medicine© 2017 American Heart Association, Inc. Rationale:The interaction of circulating cells within the vascular wall is a critical event in chronic inflammatory processes, such as atherosclerosis, but the control of the vascular inflammatory state is still largely unclear.Objective: This study was undertaken to characterize the function of the endothelial-enriched microRNA miR-100 during vascular inflammation and atherogenesis. Methods and Results:Based on a transcriptome analysis of endothelial cells after miR-100 overexpression, we identified miR-100 as a potent suppressor of endothelial adhesion molecule expression, resulting in attenuated leukocyte-endothelial interaction in vitro and in vivo as shown by flow cytometry and intravital imaging. Mechanistically, miR-100 directly repressed several components of mammalian target of rapamycin complex 1-signaling, including mammalian target of rapamycin and raptor, which resulted in a stimulation of endothelial autophagy and attenuated nuclear factor κB signaling in vitro and in vivo. In a low-density lipoprotein receptordeficient atherosclerotic mouse model, pharmacological inhibition of miR-100 resulted in enhanced plaque lesion formation and a higher macrophage content of the plaque, whereas a systemic miR-100 replacement therapy had protective effects and attenuated atherogenesis, resulting in a decrease of plaque area by 45%. Finally, analysis of miR-100 expression in >70 samples obtained during carotid endarterectomy revealed that local miR-100 expression was inversely correlated with inflammatory cell content in patients. Conclusions: In summary, we describe an anti-inflammatory function of miR-100 in the vascular response to injury and inflammation and identify an important novel modulator of mammalian target of rapamycin signaling and autophagy

During the course of atherosclerotic vascular disease, the adaptive growth of blood vessels is a naturally occurring process that can partly compensate for the decrease in blood flow after the narrowing or occlusion of a major artery. It includes both the sprouting of new endothelial capillaries (angiogenesis) and the enlargement of pre-existing arteriolar and arterial anastomoses to functional collateral arteries (arteriogenesis).1 During angiogenesis, a drop in tissue oxygen tension results in increased expression of hypoxiainducible transcription factors and cytokines, stimulating endothelial proliferation and sprouting in the ischemic tissue, improving distribution and use of the remaining blood flow. On the other hand, arteriogenesis is characterized by a well-orchestrated inflammatory response that is not restricted to the endothelial cell (EC) layer but facilitated by the perivascular infiltration of bone marrow-derived cell populations, mediating the proliferation of both endothelial and vascular smooth muscle cells. During the past decade, monocytes and macrophages were especially demonstrated to exert an important stimulatory function in the regulation of collateral artery growth.2 Although our knowledge about these contributing cell populations in the different forms of vascular growth steadily increases, our understanding of the basic regulatory principles controlling these processes is still limited. Other than canonical mediators of blood vessel growth, such as growth factors and their receptors, an additional functional group of regulators has recently emerged: microRNAs (miRNAs). These short (17-24 nucleotides), single-stranded regulatory RNA sequences are transcribed as precursor hairpin structures from intergenic or intronic regions of the genome that undergo several nuclear and cytoplasmatic processing steps to the mature miRNA.3 Together with Argonaute proteins, they form the RNA-induced silencing complex and recognize specific sequences mostly located in the 3′ untranslated region of their target mRNA, resulting either in inhibition of translation or degradation of Background-Adaptive neovascularization after arterial occlusion is an important compensatory mechanism in cardiovascular disease and includes both the remodeling of pre-existing vessels to collateral arteries (arteriogenesis) and angiogenic capillary growth. We now aimed to identify regulatory microRNAs involved in the modulation of neovascularization after femoral artery occlusion in mice. Methods and Results-Using microRNA-transcriptome analysis, we identified miR-155 as a downregulated microRNA during hindlimb ischemia. Correspondingly, inhibition of miR-155 in endothelial cells had a stimulatory effect on proliferation and angiogenic tube formation via derepression of its direct target gene angiotensin II type 1 receptor. Surprisingly, miR-155-deficient mice showed an unexpected phenotype in vivo, with a strong reduction of blood flow recovery after femoral artery ligation (arteriogenesis) dependent on the attenuation of leuko...

The inflammatory sequelae of ischemia-reperfusion injury (IRI) are a major causal factor of tissue injury in various clinical settings. MicroRNAs (miRs) are short, non-coding RNAs, which regulate protein expression. Here, we investigated the role of miR-155 in IR-related tissue injury. Quantifying microRNA-expression levels in a human muscle tissue after IRI, we found miR-155 expression to be significantly increased and to correlate with the increased expression of TNF-α, IL-1β, CD105, and Caspase3 as well as with leukocyte infiltration. The direct miR-155 target gene SOCS-1 was downregulated. In a mouse model of myocardial infarction, temporary LAD ligation and reperfusion injury resulted in a smaller area of necrosis in miR-155-/- animals compared to wildtype animals. To investigate the underlying mechanisms, we evaluated the effect of miR-155 on inflammatory cell recruitment by intravital microscopy and on the generation of reactive oxygen species (ROS) of macrophages. Our intravital imaging results demonstrated a decreased recruitment of inflammatory cells in miR-155-/- animals during IRI. The generation of ROS in leukocytic cells of miR-155-/- animals was also reduced. RNA silencing of the direct miR-155 target gene SOCS-1 abrogated this effect. In conclusion, miR-155 aggravates the inflammatory response, leukocyte infiltration and tissue damage in IRI via modulation of SOCS-1-dependent generation of ROS. MiR-155 is thus a potential target for the treatment or prevention of IRI.

miR-155 deficiency alleviates AAI by diminishing Th2 priming capacity and ATP-/P2R-induced activation of DCs in mice, suggesting this miRNA as a potential therapeutic target of AAI.

MicroRNAs are small non-coding RNAs that negatively regulate posttranscriptional gene expression. Several microRNAs have been described to regulate the process of angiogenesis. Previously, we have shown that bone morphogenetic protein 4 (BMP4) increased the pro-angiogenic activity of endothelial cells. In this project, we now investigated how the pro-angiogenic BMP4 effect is mediated by microRNAs. First, we performed a microRNA array with BMP4-stimulated human umbilical vein endothelial cells (HUVECs). Among the top-regulated microRNAs, we detected a decreased expression of miR-494 and increased expression of miR-126-5p. Next, we analysed the canonical Smad and alternative signalling pathways, through which BMP4 would regulate miR-126-5p and miR-494 expression. Furthermore, the functional effect of miR-494 and miR-126-5p on endothelial cells was investigated. MicroRNA-494 overexpression decreased endothelial cell proliferation, migration and sprout formation. Consistently, miR-494 inhibition increased endothelial cell function. As potential miR-494 targets, bFGF and BMP endothelial cell precursor-derived regulator (BMPER) were identified and confirmed by western blot. Luciferase assays showed direct miR-494 binding in BMPER 3'UTR. In contrast, miR-126-5p overexpression increased pro-angiogenic endothelial cell behaviour and, accordingly, miR-126-5p inhibition decreased endothelial cell function. As a direct miR-126-5p target we identified the anti-angiogenic thrombospondin-1 which was confirmed by western blot analysis and luciferase assays. In the Matrigel plug assay application of antagomiR-494 increased endothelial cell ingrowth, whereas antagomiR-126-5p treatment decreased cell ingrowth in vivo. Taken together, through differential regulation of the anti-angiomiR-494 and the angiomiR-126-5p by BMP4 both microRNAs contribute to the pro-angiogenic BMP4 effect on endothelial cells.

Background Diet-induced obesity can result in the development of a diverse spectrum of cardiovascular and metabolic diseases, including type 2 diabetes, dyslipidemia, non-alcoholic liver steatosis and atherosclerotic disease. MicroRNAs have been described to be important regulators of metabolism and disease development. Methods In the current study, we investigated the effects of ubiquitous miR-100 overexpression on weight gain and the metabolic phenotype in a newly generated transgenic mouse strain under normal chow and high fat diet and used microarray expression analysis to identify new potential target genes of miR-100. Results While transgenic overexpression of miR-100 did not significantly affect weight and metabolism under a normal diet, miR-100 overexpressing mice showed a reduced weight gain under a high fat diet compared to wildtype mice, despite an equal calorie intake. This was accompanied by less visceral and subcutaneous fat development and lover serum LDL cholesterol. In addition, transgenic miR-100 mice were more glucose tolerant and insulin sensitive and demonstrated increased energy expenditure under high fat diet feeding. A comprehensive gene expression profiling revealed the differential expression of several genes involved in lipid storage- and metabolism, among them CD36 and Cyp4A14. Our data showed a direct regulation of CD36 by miR-100, leading to a reduced fatty acid uptake in primary hepatocytes overexpressing miR-100 and the downregulation of several downstream mediators of lipid metabolism such as ACC1, FABP4, FAS and PPARγ in the liver. Conclusions Our findings demonstrate a protective role of miR-100 in high fat diet induced metabolic syndrome and liver steatosis, partially mediated by the direct repression of CD36 and attenuation of hepatic lipid storage, implicating miR-100 as a possible therapeutic target in liver steatosis.

Aims The endothelium plays an important role during vascular inflammation. Previous data have demonstrated a high expression level of manganese-superoxide dismutase (MnSOD) in endothelial cells and suggested an important role of MnSOD in several cardiovascular diseases. Manganese (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) has been shown to mimic some of the effects of MnSOD and prevented the development of diabetes and obesity. However, its effect on vascular inflammation and the underlying mechanism is still unknown. Methods and results Leukocyte adhesion was evaluated in-vivo and in-vitro using dynamic flow chamber and intravital microscopy in mice. Expression of adhesion molecules induced by TNFα and adhesion of leukocytes to the vessel wall were inhibited by MnTBAP. The anti-inflammatory effect of MnTBAP was partly mediated by up-regulation of the BMPR-II and Smad dependent pathway. Additionally, MnTBAP decelerated the turn-over of endogenous BMPR-II. Conclusion Our data demonstrate that MnTBAP activates Smad signaling, preserves the turn-over of BMPR-II and elicits anti-inflammatory effects in endothelial cells, partly mediated by BMPR-II. This finding suggests a potential therapeutic impact of MnTBAP in the treatment of vascular inflammation.

Dedifferentiated vascular smooth muscle cells (vSMCs) play an essential role in neointima formation, and we now aim to investigate the role of the bone morphogenetic protein (BMP) modulator BMPER (BMP endothelial cell precursor-derived regulator) in neointima formation. To assess BMPER expression in arterial restenosis, we used a mouse carotid ligation model with perivascular cuff placement. Overall BMPER expression after vessel injury was increased; however, expression in the tunica media was decreased compared to untreated control. Consistently, BMPER expression was decreased in proliferative, dedifferentiated vSMC in vitro. C57BL/6_Bmper+/− mice displayed increased neointima formation 21 days after carotid ligation and enhanced expression of Col3A1, MMP2, and MMP9. Silencing of BMPER increased the proliferation and migration capacity of primary vSMCs, as well as reduced contractibility and expression of contractile markers, whereas stimulation with recombinant BMPER protein had the opposite effect. Mechanistically, we showed that BMPER binds insulin-like growth factor-binding protein 4 (IGFBP4), resulting in the modulation of IGF signaling. Furthermore, perivascular application of recombinant BMPER protein prevented neointima formation and ECM deposition in C57BL/6N mice after carotid ligation. Our data demonstrate that BMPER stimulation causes a contractile vSMC phenotype and suggest that BMPER has the potential for a future therapeutic agent in occlusive cardiovascular diseases.