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Deep vein thrombosis (DVT) is the third most common cause of cardiovascular mortality. Several studies suggest that DVT occurs at the intersection of dysregulated inflammation and coagulation upon activation of inflammasome and secretion of interleukin 1β (IL-1β) in restricted venous flow conditions. Our recent studies showed a signaling adapter protein, Gab2 (Grb2-associated binder 2), plays a crucial role in propagating inflammatory signaling triggered by IL-1β and other inflammatory mediators in endothelial cells. The present study shows that Gab2 facilitates the assembly of the CBM (CARMA3 [CARD recruited membrane-associated guanylate kinase protein 3]–BCL-10 [B-cell lymphoma 10]–MALT1 [mucosa-associated lymphoid tissue lymphoma translocation protein 1]) signalosome, which mediates the activation of Rho and NF-κB in endothelial cells. Gene silencing of Gab2 or MALT1, the effector signaling molecule in the CBM signalosome, or pharmacological inhibition of MALT1 with a specific inhibitor, mepazine, significantly reduced IL-1β–induced Rho-dependent exocytosis of P-selectin and von Willebrand factor (VWF) and the subsequent adhesion of neutrophils to endothelial cells. MALT1 inhibition also reduced IL-1β–induced NF-κB–dependent expression of tissue factor and vascular cell adhesion molecule 1. Consistent with the in vitro data, Gab2 deficiency or pharmacological inhibition of MALT1 suppressed the accumulation of monocytes and neutrophils at the injury site and attenuated venous thrombosis induced by the inferior vena cava ligation-induced stenosis or stasis in mice. Overall, our data reveal a previously unrecognized role of the Gab2–MALT1 axis in thromboinflammation. Targeting the Gab2–MALT1 axis with MALT1 inhibitors may become an effective strategy to treat DVT by suppressing thromboinflammation without inducing bleeding complications.

Coagulation protease, factor VIIa (FVIIa), binds to endothelial cell protein C receptor (EPCR) and induces anti-inflammatory and endothelial barrier protective responses via protease-activated receptor-1 (PAR1)–mediated, biased signaling. Our recent studies had shown that the FVIIa-EPCR-PAR1 axis induces the release of extracellular vesicles (EVs) from endothelial cells. In the present study, we investigated the mechanism of FVIIa release of endothelial EVs (EEVs) and the contribution of FVIIa-released EEVs to anti-inflammatory and vascular barrier protective effects, in both in vitro and in vivo models. Multiple signaling pathways regulated FVIIa release of EVs from endothelial cells, but the ROCK-dependent pathway appeared to be a major mechanism. FVIIa-released EEVs were enriched with anti-inflammatory microRNAs (miRs), mostly miR10a. FVIIa-released EEVs were taken up readily by monocytes/macrophages and endothelial cells. The uptake of FVIIa-released EEVs by monocytes conferred anti-inflammatory phenotype to monocytes, whereas EEV uptake by endothelial cells resulted in barrier protection. In additional experiments, EEV-mediated delivery of miR10a to monocytes downregulated the expression of TAK1 and activation of the NF-κB–mediated inflammatory pathway. In in vivo experiments, administration of FVIIa-released EEVs to wild-type mice attenuated LPS-induced increased inflammatory cytokines in plasma and vascular leakage into vital tissues. The incorporation of anti-miR10a into FVIIa-released EEVs diminished the ability of FVIIa-released EEVs to confer cytoprotective effects. Administration of the ROCK inhibitor Y27632, which significantly inhibits FVIIa release of EEVs into the circulation, to mice attenuated the cytoprotective effects of FVIIa. Overall, our study revealed novel insights into how FVIIa induces cytoprotective effects and communicates with various cell types.

Peripheral T-cell lymphomas (PTCL) - especially angioimmunoblastic (AITL) and follicular TCL - have a dismal prognosis due to lack of efficient therapies, and patients` symptoms are often dominated by an inflammatory phenotype including fever, night sweats, weight loss and skin rash. In this study, we investigated the role of inflammatory granulocytes and activated cytokine signaling on PTCL-TFH (T-follicular helper type) disease progression and symptoms. We show, that ITK-SYK driven murine PTCLs and primary human PTCL-TFH xenografts both induce inflammation in mice including murine neutrophil expansion and massive cytokine release. Granulocyte/lymphoma interactions were mediated by positive autoregulatory cytokine loops involving INF-γ (CD4+malignant T-cells) and IL-6 (activated granulocytes), ultimately inducing broad JAK kinase activation (Jak1/2/3, Tyk2) in both cell types. Depletion of inflammatory granulocytes via antibodies (Ly6G), genetic granulocyte depletion (LyzM-Cre/MCL1flox/flox) or the deletion of IL-6 within microenvironmental cells blocked inflammatory symptoms, reduced lymphoma infiltration and enhanced mouse survival. Furthermore, unselective JAK kinase inhibitors (ruxolitinib) inhibited both, TCL progression and granulocyte activation in various PTCL mouse models. Our results support the important role of granulocyte-driven inflammation, cytokine-induced granulocyte/CD4+ TCL interactions and the requirement of an intact JAK/STAT signaling pathway for PTCL-TFH development, and support broad JAK kinase inhibition as an effective treatment strategy in early disease stages.

Recombinant factor FVIIa (rFVIIa) is used as a hemostatic agent to treat bleeding disorders in hemophilia patients with inhibitors and other groups of patients. Our recent studies showed that FVIIa binds endothelial cell protein C receptor (EPCR) and induces protease-activated receptor 1 (PAR1)-mediated biased signaling. The importance of FVIIa-EPCR-PAR1–mediated signaling in hemostasis is unknown. In the present study, we show that FVIIa induces the release of extracellular vesicles (EVs) from endothelial cells both in vitro and in vivo. Silencing of EPCR or PAR1 in endothelial cells blocked the FVIIa-induced generation of EVs. Consistent with these data, FVIIa treatment enhanced the release of EVs from murine brain endothelial cells isolated from wild-type (WT), EPCR-overexpressing, and PAR1-R46Q–mutant mice, but not EPCR-deficient or PAR1-R41Q–mutant mice. In vivo studies revealed that administration of FVIIa to WT, EPCR-overexpressing, and PAR1-R46Q–mutant mice, but not EPCR-deficient or PAR1-R41Q–mutant mice, increased the number of circulating EVs. EVs released in response to FVIIa treatment exhibit enhanced procoagulant activity. Infusion of FVIIa-generated EVs and not control EVs to platelet-depleted mice increased thrombin generation at the site of injury and reduced blood loss. Administration of FVIIa-generated EVs or generation of EVs endogenously by administering FVIIa augmented the hemostatic effect of FVIIa. Overall, our data reveal that FVIIa treatment, through FVIIa-EPCR-PAR1 signaling, releases EVs from the endothelium into the circulation, and these EVs contribute to the hemostatic effect of FVIIa.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with the hypercoagulable state. Tissue factor (TF) is the primary cellular initiator of coagulation. Most of the TF expressed on cell surfaces remains cryptic. Sphingomyelin (SM) is responsible for maintaining TF in the encrypted state, and hydrolysis of SM by acid sphingomyelinase (ASMase) increases TF activity. ASMase was shown to play a role in virus infection biology. In the present study, we investigated the role of ASMase in SARS-CoV-2 infection-induced TF procoagulant activity. Infection of human monocyte–derived macrophages (MDMs) with SARS-CoV-2 spike protein pseudovirus (SARS-CoV-2–SP-PV) markedly increased TF procoagulant activity at the cell surface and released TF+ extracellular vesicles. The pseudovirus infection did not increase either TF protein expression or phosphatidylserine externalization. SARS-CoV-2–SP-PV infection induced the translocation of ASMase to the outer leaflet of the plasma membrane, which led to the hydrolysis of SM in the membrane. Pharmacologic inhibitors or genetic silencing of ASMase attenuated SARS-CoV-2–SP-PV–induced increased TF activity. Inhibition of the SARS-CoV-2 receptor, angiotensin-converting enzyme-2, attenuated SARS-CoV-2–SP-PV–induced increased TF activity. Overall, our data suggest that SARS-CoV-2 infection activates the coagulation by decrypting TF through activation of ASMase. Our data suggest that the US Food and Drug Administration–approved functional inhibitors of ASMase may help treat hypercoagulability in patients with COVID-19.

We recently showed that clotting factor VIIa (FVIIa) binding to endothelial cell protein C receptor (EPCR) induces anti-inflammatory signaling and protects vascular barrier integrity. Inflammation and vascular permeability are thought to be major contributors to the development of hemophilic arthropathy following hemarthrosis. The present study was designed to investigate the potential influence of FVIIa interaction with EPCR in the pathogenesis of hemophilic arthropathy and its treatment with recombinant FVIIa (rFVIIa). For this, we first generated hemophilia A (FVIII−/−) mice lacking EPCR (EPCR−/−FVIII−/−) or overexpressing EPCR (EPCR++ FVIII−/−). Joint bleeding was induced in FVIII−/−, EPCR−/−FVIII−/−, and EPCR++FVIII−/− mice by needle puncture injury. Hemophilic synovitis was evaluated by monitoring joint bleeding, change in joint diameter, and histopathological analysis of joint tissue sections. EPCR deficiency in FVIII−/− mice significantly reduced the severity of hemophilic synovitis. EPCR deficiency attenuated the elaboration of interleukin-6, infiltration of macrophages, and neoangiogenesis in the synovium following hemarthrosis. A single dose of rFVIIa was sufficient to fully prevent the development of milder hemophilic synovitis in EPCR−/−FVIII−/− mice. The development of hemophilic arthropathy in EPCR-overexpressing FVIII−/− mice did not significantly differ from that of FVIII−/− mice, and 3 doses of rFVIIa partly protected against hemophilic synovitis in these mice. Consistent with the data that EPCR deficiency protects against developing hemophilic arthropathy, administration of a single dose of EPCR-blocking monoclonal antibodies markedly reduced hemophilic synovitis in FVIII−/− mice subjected to joint bleeding. The present data indicate that EPCR could be an attractive new target to prevent joint damage in hemophilia patients.