Objective: Macrophages are immune cells, capable to remodel the extracellular matrix, which can harbor extracellular DNA incorporated into neutrophil extracellular traps (NETs). To study the breakdown of NETs we studied the capability of macrophage subsets to degrade these structures in vitro and in vivo in a murine thrombosis model. Furthermore, we analyzed human abdominal aortic aneurysm samples in support of our in vitro and in vivo results. Approach and Results: Macrophages were seeded onto blood clots or isolated NETs and polarized. All macrophages were capable to degrade NETs. For initial breakdown, macrophages relied on extracellular deoxyribonucleases. Proinflammatory polarization enhanced NET degradation. The boost in degradation was because of increased macropinocytosis, as inhibition by imipramine diminished their NET breakdown. Inhibition of macropinocytosis in a murine thrombosis model led to increased NET burden and reduced thrombus resolution in vivo. When analyzing abdominal aortic aneurysm samples, macrophage density furthermore corresponded negatively with the amount of local NETs in the intraluminal thrombi as well as in the vessel wall, as increased macrophage density was associated with a reduction in NET burden. Conclusions: We provide evidence that macrophages degrade NETs by extracellular predigestion and subsequent uptake. Furthermore, we show that proinflammatory macrophages increase NET degradation through enhanced macropinocytosis, priming them for NET engulfment. Based on our findings, that inhibition of macropinocytosis in mice corresponded to increased NET amounts in thrombi and that local macrophage density in human abdominal aortic aneurysm is negatively associated with surrounding NETs, we hypothesize, that macrophages are able to degrade NETs in vivo.

Training of the innate immune system with orally ingested bacterial extracts was demonstrated to have beneficial effects on infection clearance and disease outcome. The aim of our study was to identify cellular and molecular processes responsible for these immunological benefits. We used a murine coronavirus (MCoV) A59 mouse model treated with the immune activating bacterial extract Broncho-Vaxom (BV) OM-85. Tissue samples were analysed with qPCR, RNA sequencing, histology, and flow cytometry. After BV OM-85 treatment, interstitial macrophages accumulated in lung tissue leading to a faster response of type I interferon (IFN) signalling after MCoV infection resulting in overall lung tissue protection. Moreover, RNA sequencing showed that lung tissue from mice receiving BV OM-85 resembled an intermediate stage between healthy and viral infected lung tissue at day 4, indicating a faster return to normal tissue homoeostasis. The pharmacologic effect was mimicked by adoptively transferring naive lung macrophages into lungs from recipient mice before virus infection. The beneficial effect of BV OM-85 was abolished when inhibiting initial type I IFN signalling. Overall, our data suggest that BV OM-85 enhances lung macrophages allowing for a faster IFN response towards a viral challenge as part of the oral-induced innate immune system training.

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Background Plg‐RKT, a unique transmembrane plasminogen receptor, enhances the activation of plasminogen to plasmin, and localizes the proteolytic activity of plasmin on the cell surface. Objectives We investigated the role of Plg‐RKT in adipose function, metabolic homeostasis, and obesity. Methods We used adipose tissue (AT) sections from bariatric surgery patients and from high fat diet (HFD)‐induced obese mice together with immunofluorescence and real‐time polymerase chain reaction to study adipose expression of Plg‐RKT. Mice genetically deficient in Plg‐RKT and littermate controls fed a HFD or control low fat diet (LFD) were used to determine the role of Plg‐RKT in insulin resistance, glucose tolerance, type 2 diabetes, and associated mechanisms including adipose inflammation, fibrosis, and ectopic lipid storage. The role of Plg‐RKT in adipogenesis was determined using 3T3‐L1 preadipocytes and primary cultures established from Plg‐RKT–deficient and littermate control mice. Results Plg‐RKT was highly expressed in both human and mouse AT, and its levels dramatically increased during adipogenesis. Plg‐RKT–deficient mice, when fed a HFD, gained more weight, developed more hepatic steatosis, and were more insulin resistant/glucose intolerant than HFD‐fed wild‐type littermates. Mechanistically, these metabolic defects were linked with increased AT inflammation, AT macrophage and T‐cell accumulation, adipose and hepatic fibrosis, and decreased insulin signaling in the AT and liver. Moreover, Plg‐RKT regulated the expression of PPARγ and other adipogenic molecules, suggesting a novel role for Plg‐RKT in the adipogenic program. Conclusions Plg‐RKT coordinately regulates multiple aspects of adipose function that are important to maintain efficient metabolic homeostasis.

Background Monocyte–platelet aggregates (MPAs) are a sensitive marker of in vivo platelet activation in acute coronary syndrome (ACS) and associated with clinical outcomes. MicroRNAs (miRs) play an important role in the regulation of platelet activation, and may influence MPA formation. Both, miRs and MPA, could be influenced by the type of P2Y12 inhibitor. Aim To study the association of platelet-related miRs with MPA formation in ACS patients on dual antiplatelet therapy (DAPT), and to compare miRs and MPA levels between prasugrel- and ticagrelor-treated patients. Methods and Results We analyzed 10 circulating platelet-related miRs in 160 consecutive ACS patients on DAPT with low-dose aspirin and either prasugrel (n = 80) or ticagrelor (n = 80). MPA formation was measured by flow cytometry without addition of platelet agonists and after simulation with the toll-like receptor (TLR)-1/2 agonist Pam3CSK4, adenosine diphosphate (ADP), or arachidonic acid (AA). In multivariate regression analyses, we identified miR-21 (β = 9.50, 95% confidence interval [CI]: 1.60–17.40, p = 0.019) and miR-126 (β = 7.50, 95% CI: 0.55–14.44, p = 0.035) as independent predictors of increased MPA formation in vivo and after TLR-1/2 stimulation. In contrast, none of the investigated miRs was independently associated with MPA formation after stimulation with ADP or AA. Platelet-related miR expression and MPA formation did not differ significantly between prasugrel- and ticagrelor-treated patients. Conclusion Platelet-related miR-21 and miR-126 are associated with MPA formation in ACS patients on DAPT. miRs and MPA levels were similar in prasugrel- and ticagrelor-treated patients.