Glycolytic reprogramming fuels myeloid cell-driven hypercoagulability.

BACKGROUND: Myeloid cell metabolic reprogramming is a hallmark of inflammatory disease; however, its role in inflammation-induced hypercoagulability is poorly understood. OBJECTIVES: We aimed to evaluate the role of inflammation-associated metabolic reprogramming in regulating blood coagulation. METHODS: We used novel myeloid cell-based global hemostasis assays and murine models of immunometabolic disease. RESULTS: Glycolysis was essential for enhanced activated myeloid cell tissue factor expression and decryption, driving increased cell-dependent thrombin generation in response to inflammatory challenge. Similarly, inhibition of glycolysis enhanced activated macrophage fibrinolytic activity through reduced plasminogen activator inhibitor 1 activity. Macrophage polarization or activation markedly increased endothelial protein C receptor (EPCR) expression on monocytes and macrophages, leading to increased myeloid cell-dependent protein C activation. Importantly, inflammation-dependent EPCR expression on tissue-resident macrophages was also observed in vivo. Adipose tissue macrophages from obese mice fed a high-fat diet exhibited significantly enhanced EPCR expression and activated protein C generation compared with macrophages isolated from the adipose tissue of healthy mice. Similarly, the induction of colitis in mice prompted infiltration of EPCR+ innate myeloid cells within inflamed colonic tissue that were absent from the intestinal tissue of healthy mice. CONCLUSION: Collectively, this study identifies immunometabolic regulation of myeloid cell hypercoagulability, opening new therapeutic possibilities for targeted mitigation of thromboinflammatory disease.

Heterogeneity in Bleeding Tendency and Arthropathy Development in Individuals with Hemophilia.

People with hemophilia (PWH) have an increased tendency to bleed, often into their joints, causing debilitating joint disease if left untreated. To reduce the incidence of bleeding events, PWH receive prophylactic replacement therapy with recombinant factor VIII (FVIII) or FIX. Bleeding events in PWH are typically proportional to their plasma FVIII or IX levels; however, in many PWH, bleeding tendency and the likelihood of developing arthropathy often varies independently of endogenous factor levels. Consequently, many PWH suffer repeated bleeding events before correct dosing of replacement factor can be established. Diagnostic approaches to define an individual's bleeding tendency remain limited. Multiple modulators of bleeding phenotype in PWH have been proposed, including the type of disease-causing variant, age of onset of bleeding episodes, plasma modifiers of blood coagulation or clot fibrinolysis pathway activity, interindividual differences in platelet reactivity, and endothelial anticoagulant activity. In this review, we summarize current knowledge of established factors modulating bleeding tendency and discuss emerging concepts of additional biological elements that may contribute to variable bleeding tendency in PWH. Finally, we consider how variance in responses to new gene therapies may also necessitate consideration of patient-specific tailoring of treatment. Cumulatively, these studies highlight the need to reconsider the current "one size fits all" approach to treatment regimens for PWH and consider therapies guided by the bleeding phenotype of each individual PWH at the onset of therapy. Further characterization of the biological bases of bleeding heterogeneity in PWH, combined with the development of novel diagnostic assays to identify those factors that modulate bleeding risk in PWH, will be required to meet these aspirations.

The vaccine adjuvant alum promotes IL-10 production that suppresses Th1 responses.

The effectiveness of many vaccines licensed for clinical use relates to the induction of neutralising antibodies, facilitated by the inclusion of vaccine adjuvants, particularly alum. However, the ability of alum to preferentially promote humoral rather than cellular, particularly Th1-type responses, is not well understood. We demonstrate that alum activates immunosuppressive mechanisms following vaccination, which limit its capacity to induce Th1 responses. One of the key cytokines limiting excessive immune responses is IL-10. Injection of alum primed draining lymph node cells for enhanced IL-10 secretion ex vivo. Moreover, at the site of injection, macrophages and dendritic cells were key sources of IL-10 expression. Alum strongly enhanced the transcription and secretion of IL-10 by macrophages and dendritic cells. The absence of IL-10 signalling did not compromise alum-induced cell infiltration into the site of injection, but resulted in enhanced antigen-specific Th1 responses after vaccination. In contrast to its decisive regulatory role in regulating Th1 responses, there was no significant change in antigen-specific IgG1 antibody production following vaccination with alum in IL-10-deficient mice. Overall, these findings indicate that injection of alum promotes IL-10, which can block Th1 responses and may explain the poor efficacy of alum as an adjuvant for inducing protective Th1 immunity.