Mice expressing nonpolymerizable fibrinogen have reduced arterial and venous thrombosis with preserved hemostasis.

ABSTRACT: Elevated circulating fibrinogen levels correlate with increased risk for both cardiovascular and venous thromboembolic diseases. In vitro studies show that formation of a highly dense fibrin matrix is a major determinant of clot structure and stability. Here, we analyzed the impact of nonpolymerizable fibrinogen on arterial and venous thrombosis as well as hemostasis in vivo using FgaEK mice that express normal levels of a fibrinogen that cannot be cleaved by thrombin. In a model of carotid artery thrombosis, FgaWT/EK and FgaEK/EK mice were protected from occlusion with 4% ferric chloride (FeCl3) challenges compared with wild-type (FgaWT/WT) mice, but this protection was lost, with injuries driven by higher concentrations of FeCl3. In contrast, fibrinogen-deficient (Fga-/-) mice showed no evidence of occlusion, even with high-concentration FeCl3 challenge. Fibrinogen-dependent platelet aggregation and intraplatelet fibrinogen content were similar in FgaWT/WT, FgaWT/EK, and FgaEK/EK mice, consistent with preserved fibrinogen-platelet interactions that support arterial thrombosis with severe challenge. In an inferior vena cava stasis model of venous thrombosis, FgaEK/EK mice had near complete protection from thrombus formation. FgaWT/EK mice also displayed reduced thrombus incidence and a significant reduction in thrombus mass relative to FgaWT/WT mice after inferior vena cava stasis, suggesting that partial expression of nonpolymerizable fibrinogen was sufficient for conferring protection. Notably, FgaWT/EK and FgaEK/EK mice had preserved hemostasis in multiple models as well as normal wound healing times after skin incision, unlike Fga-/- mice that displayed significant bleeding and delayed healing. These findings indicate that a nonpolymerizable fibrinogen variant can significantly suppress occlusive thrombosis while preserving hemostatic potential in vivo.

C1 inhibitor deficiency enhances contact pathway-mediated activation of coagulation and venous thrombosis.

C1 inhibitor (C1INH) is a multifunctional serine protease inhibitor that functions as a major negative regulator of several biological pathways, including the contact pathway of blood coagulation. In humans, congenital C1INH deficiency results in a rare episodic bradykinin-mediated swelling disorder called hereditary angioedema (HAE). Patients with C1INH deficiency-associated HAE (C1INH-HAE) have increased circulating markers of activation of coagulation. Furthermore, we recently reported that patients with C1INH-HAE had a moderate but significant increased risk of venous thromboembolism. To further investigate the impact of C1INH deficiency on activation of coagulation and thrombosis, we conducted studies using patient samples and mouse models. Plasmas from patients with C1INH-HAE had significantly increased contact pathway-mediated thrombin generation. C1INH-deficient mice, which have been used as a model of C1INH-HAE, had significantly increased baseline circulating levels of prothrombin fragment 1+2 and thrombin-antithrombin complexes. In addition, whole blood from C1INH-deficient mice supported significantly increased contact pathway-mediated thrombin generation. Importantly, C1INH-deficient mice exhibited significantly enhanced venous, but not arterial, thrombus formation. Furthermore, purified human C1INH normalized contact pathway-mediated thrombin generation and venous thrombosis in C1INH-deficient mice. These findings highlight a key role for endogenous C1INH as a negative regulator of contact pathway-mediated coagulation in humans and mice. Further, this work identifies endogenous C1INH as an important negative regulator of venous thrombus formation in mice, complementing the phenotype associated with C1INH-HAE.

Both G protein-coupled and immunoreceptor tyrosine-based activation motif receptors mediate venous thrombosis in mice.

Platelets are critical in hemostasis and a major contributor to arterial thrombosis (AT). (Pre)clinical studies suggest platelets also contribute to venous thrombosis (VT), but the mechanisms are largely unknown. We hypothesized that in VT, platelets use signaling machinery distinct from AT. Here we aimed to characterize the contributions of platelet G protein-coupled (GPCR) and immunoreceptor tyrosine-based activation motif (ITAM) receptor signaling to VT. Wild-type (WT) and transgenic mice were treated with inhibitors to selectively inhibit platelet-signaling pathways: ITAM-CLEC2 (Clec2mKO), glycoprotein VI (JAQ1 antibody), and Bruton's tyrosine kinase (ibrutinib); GPCR-cyclooxygenase 1 (aspirin); and P2Y12 (clopidogrel). VT was induced by inferior vena cava stenosis. Thrombin generation in platelet-rich plasma and whole-blood clot formation were studied ex vivo. Intravital microscopy was used to study platelet-leukocyte interactions after flow restriction. Thrombus weights were reduced in WT mice treated with high-dose aspirin + clopidogrel (dual antiplatelet therapy [DAPT]) but not in mice treated with either inhibitor alone or low-dose DAPT. Similarly, thrombus weights were reduced in mice with impaired ITAM signaling (Clec2mKO + JAQ1; WT + ibrutinib) but not in Clec2mKO or WT + JAQ1 mice. Both aspirin and clopidogrel, but not ibrutinib, protected mice from FeCl3-induced AT. Thrombin generation and clot formation were normal in blood from high-dose DAPT- or ibrutinib-treated mice; however, platelet adhesion and platelet-neutrophil aggregate formation at the vein wall were reduced in mice treated with high-dose DAPT or ibrutinib. In summary, VT initiation requires platelet activation via GPCRs and ITAM receptors. Strong inhibition of either signaling pathway reduces VT in mice.

CREB Coactivator CRTC2 Plays a Crucial Role in Endothelial Function.

The cAMP pathway is known to stabilize endothelial barrier function and maintain vascular physiology. The family of cAMP-response element binding (CREB)-regulated transcription coactivators (CRTC)1-3 activate transcription by targeting the basic leucine zipper domain of CREB. CRTC2 is a master regulator of glucose metabolism in liver and adipose tissue. However, the role of CRTC2 in endothelium remains unknown. The aim of this study was to evaluate the effect of CRTC2 on endothelial function. We focused the effect of CRTC2 in endothelial cells and its relationship with p190RhoGAP-A. We examined the effect of CRTC2 on endothelial function using a mouse aorta ring assay ex vivo and with photothrombotic stroke in endothelial cell-specific CRTC2-knock-out male mice in vivo CRTC2 was highly expressed in endothelial cells and related to angiogenesis. Among CRTC1-3, only CRTC2 was activated under ischemic conditions at endothelial cells, and CRTC2 maintained endothelial barrier function through p190RhoGAP-A expression. Ser171 was a pivotal regulatory site for CRTC2 intracellular localization, and Ser307 functioned as a crucial phosphorylation site. Endothelial cell-specific CRTC2-knock-out mice showed reduced angiogenesis ex vivo, exacerbated stroke via endothelial dysfunction, and impaired neurologic recovery via reduced vascular beds in vivo These findings suggest that CRTC2 plays a crucial protective role in vascular integrity of the endothelium via p190RhoGAP-A under ischemic conditions.SIGNIFICANCE STATEMENT Previously, the role of CRTC2 in endothelial cells was unknown. In this study, we firstly clarified that CRTC2 was expressed in endothelial cells and among CRTC1-3, only CRTC2 was related to endothelial function. Most importantly, only CRTC2 was activated under ischemic conditions at endothelial cells and maintained endothelial barrier function through p190RhoGAP-A expression. Ser307 in CRTC2 functioned as a crucial phosphorylation site. Endothelial cell-specific CRTC2-knock-out mice showed reduced angiogenesis ex vivo, exacerbated stroke via endothelial dysfunction, and impaired neurologic recovery via reduced vascular beds in vivo These results suggested that CRTC2 maybe a potential therapeutic target for reducing blood-brain barrier (BBB) damage and improving recovery.

Short-term experience with aspiration embolectomy using a ACE68 reperfusion catheter to treat embolic superior mesenteric artery occlusion.

We report the short-term results with aspiration embolectomy using an ACE68 reperfusion catheter to treat patients with acute embolic superior mesenteric artery (SMA) occlusion. Our study included 4 consecutive male patients ranging in age from 72 to 86 years (mean age 79 years). In all patients, the main trunk of the SMA was occluded. The technical success rate was 100% for all procedures. There were no major procedure-related complications. One patient underwent laparotomy with intestinal resection after successful recanalization. No patient reported clinical symptoms of abdominal ischemia at follow-up. Our short-term experience shows that percutaneous aspiration embolectomy using an ACE68 reperfusion catheter is an effective treatment for acute mesenteric ischemia.

Hematological Abnormalities and Malnutrition Mediate Pathway between Cancer and Outcomes in Ischemic Stroke Patients.

BACKGROUND: The present study aimed to examine whether variables including D-dimer, high-sensitivity C-reactive protein (hsCRP), hemoglobin, platelet count, and nutritional status mediate the pathway between cancer and ischemic stroke outcomes. METHODS: We reviewed data from consecutive patients with ischemic stroke admitted to Osaka University Hospital between January 1, 2006, and December 31, 2016. Patients with ischemic stroke were grouped according to the presence of cancer. Nutritional status was assessed using Controlling Nutritional Status (CONUT) scores. Mediation analyses were utilized to address the study aims. RESULTS: Among 1,570 patients with ischemic stroke, 185 (12%) had active cancer. Relative to patients with ischemic stroke in the non-cancer group, those in the cancer group exhibited higher National Institutes of Health Stroke Scale scores on admission, higher D-dimer and hsCRP levels, lower hemoglobin levels and platelet counts, higher CONUT scores, and poorer modified Rankin Scale scores at discharge. Mediation analysis revealed that D-dimer, hsCRP, hemoglobin, platelet count, and CONUT scores acted as mediators of poor prognosis in the cancer group. The association between the exposure and outcome variables was no longer significant in the models containing D-dimer and CONUT scores as mediator variables, suggesting that they were strong mediators. Regarding the association between the mediator and outcome variables, hemoglobin, platelet count, and CONUT exhibited non-linearity (p for non-linearity < 0.001). CONCLUSIONS: D-dimer, hsCRP, hemoglobin, platelet count, and CONUT score act as mediators of poor prognosis in patients with ischemic stroke with comorbid cancer. Such abnormalities can help to predict ischemic stroke outcomes.

[A Case of Transorbital Penetrating Cavernous Sinus Injury by a Bamboo Stick Treated by Craniotomy in the Hybrid Operating Room].

Herein, we report a rare case of penetrating transorbital cavernous sinus injury caused by a bamboo stick, treated by craniotomy in a hybrid operating room. A 63-year-old gardener presented at our hospital with right upper orbital injury after falling on a bamboo basket. Neurological examination revealed right II, III, IV, and VI cranial nerve palsies. CT and MRI revealed a right transorbital penetrating injury by a small sharp wooden foreign body, extending from the orbit to the cavernous sinus via the superior orbital fissure. Preoperative digital subtraction angiography revealed partial occlusion of the right cavernous sinus by the foreign body and no internal carotid artery(ICA)injury. There was a nine-day waiting period after the injury because the patient was on dual antiplatelet therapy for ischemic heart disease. Subsequently, the bamboo stick was completely removed through the right fronto-temporo-orbito-zygomatic approach in a hybrid operating room. To treat the potential massive hemorrhage, a five-French balloon catheter was inserted in the right ICA at its origin via the right transfemoral approach before the craniotomy. The bamboo stick was completely removed with minor hemorrhage in the cavernous sinus; this was controlled using hemostatic materials. The postoperative course was uneventful. The patient was discharged with blindness and total ophthalmoplegia in the right eye but he was able to return to his prior job. This is the first report of such a treatment of a transorbital penetrating injury in a hybrid operating room.

Glial fibrillary acidic protein (GFAP) is a novel biomarker for the prediction of autoimmune diabetes.

Glial fibrillary acidic protein (GFAP) is expressed in peri-islet Schwann cells, as well as in glia cells, and has been reported to be an autoantigen candidate for type 1 diabetes mellitus (T1DM). We confirmed that the production of the autoantibodies GFAP and glutamic acid decarboxylase 65 (GAD65) was increased and inversely correlated with the concentration of secreted C peptide in female nonobese diabetic mice (T1DM model). Importantly, the development of T1DM in female nonobese diabetic mice at 30 wk of age was predicted by the positive GFAP autoantibody titer at 17 wk. The production of GFAP and GAD65 autoantibodies was also increased in KK-Ay mice [type 2 diabetes mellitus (T2DM) model]. In patients with diabetes mellitus, GFAP autoantibody levels were increased in patients with either T1DM or T2DM, and were significantly associated with GAD65 autoantibodies but not zinc transporter 8 autoantibodies. Furthermore, we identified a B-cell epitope of GFAP corresponding to the GFAP autoantibody in both mice and patients with diabetes. Thus, these results indicate that autoantibodies against GFAP could serve as a predictive marker for the development of overt autoimmune diabetes.-Pang, Z., Kushiyama, A., Sun, J., Kikuchi, T., Yamazaki, H., Iwamoto, Y., Koriyama, H., Yoshida, S., Shimamura, M., Higuchi, M., Kawano, T., Takami, Y., Rakugi, H., Morishita, R., Nakagumi, H. Glial fibrillary acidic protein (GFAP) is a novel biomarker for the prediction of autoimmune diabetes.

Aortic transgraft hemorrhage after intravenous tissue plasminogen activator therapy in patients with acute ischemic stroke.

BACKGROUND: The safety of intravenous recombinant tissue plasminogen activator (IV tPA) therapy for patients with an aortic aneurysm or undergoing aortic graft replacement has not been established. We evaluated the incidence, bleeding site, coagulation factors, and clinical outcomes of patients treated with IV tPA for acute stroke. METHODS: Between October 2005 and May 2013, 394 ischemic stroke patients were treated in our stroke center with IV tPA. Among these patients, we investigated those who had a history of aortic aneurysm with or without aortic graft replacement before IV tPA therapy and underwent computed tomography imaging. We compared the levels of D-dimer and hemoglobin (Hb) around IV tPA therapy between the patients with and without tPA-associated periaortic bleeding. RESULTS: Seven patients with a history of aortic aneurysm (3 men; mean age: 80.4 years) were examined; 3 had undergone aortic graft replacement, and 2 had experienced tPA-associated bleeding around vascular grafts. The serum D-dimer levels in those with bleeding were only slightly higher before tPA than in those without (median: 10.5 vs. 1.5 µg/mL) but were elevated 1 day after tPA (107.4 vs. 8.6 µg/mL). The Hb levels 2 days after tPA were comparable with those before tPA (11.9 vs. 11.8 g/dL) but were lower in the patients with bleeding than in those without (8.5 vs. 11.7 g/dL). Surgical intervention was not required, although 1 patient required blood transfusion. CONCLUSIONS: Our analysis provides reassurance regarding the risk of IV tPA therapy in patients undergoing aortic graft replacement.

Cancer patients and ischemic stroke.

Patients with cancer have an increased risk of ischemic stroke compared to the general population. Additionally, these patients have a worse prognosis compared to stroke patients without cancer. Activation of coagulation appears to play a key role in the pathophysiology of ischemic stroke in patients with cancer. However, the underlying mechanisms remain unknown. Moreover, we do not have a way to identify cancer patients with a high risk of stroke and cannot develop prevention strategies. Therefore, there is an urgent need for neurologists and oncologists to develop screening and prevention strategies for stroke in patients with cancer. In this review, we summarize the characteristics of cancer patients at a high risk of stroke, the predictors for the development of stroke and survival in cancer patients, and possible treatments.

Arterial Thromboembolism in Japanese Patients With Cancer: Incidence, Predictors, and Survival Impact.

Background: Thromboembolism is a significant complication for patients with cancer, leading to treatment interruptions and poor outcomes. Objectives: The aim of this study was to investigate the incidence of arterial thromboembolism (ATE) within cancer populations, identify the predictors of ATE, and determine its survival impact. Methods: A retrospective multicenter study was performed using data from the Osaka Cancer Registry linked with administrative data from 2010 to 2015. Patients were monitored for 5 years after cancer diagnosis, and ATE incidence was calculated with death as a competing risk. Fine and Gray competing risk regression models and Cox proportional hazards models were used to evaluate the predictors of ATE and the survival impact. Restricted mean survival time (RMST) was used to assess whether antithrombotic therapy after ATE contributed to improved survival. Results: The cohort comprised 97,448 patients with cancer (42.3% women, median age 70 years). ATE incidence displayed an annual increase, peaking 1 year after cancer diagnosis (1-, 2-, 3-, 4-, and 5-year cumulative incidences were 1.29%, 1.77%, 2.05%, 2.22%, and 2.32%, respectively). Male sex, advanced age, advanced cancer stage, and hematologic malignancies correlated with a high risk for ATE. Patients with ATE had a 2-fold increased risk for mortality compared with those without ATE. The 90-day and 1-year RMST differences for those on antithrombotic therapy were 13.3 days (95% CI: 10.4-16.2 days; P < 0.001) and 57.8 days (95% CI: 43.1-72.5 days; P < 0.001), favoring the antithrombotic therapy group. The RMST differences varied by cancer stage. Conclusions: The risk for ATE varies according to sex, age, and cancer progression and type. Antithrombotic therapy after ATE is associated with improved survival among patients with cancer.

Mucin 1 and venous thrombosis in tumor-bearing mice and patients with cancer.

INTRODUCTION: Mucins released from epithelial tumors have been proposed to play a role in cancer-associated thrombosis. Mucin1 (MUC1) is a transmembrane mucin that is overexpressed in a variety of human malignancies, including breast and pancreatic cancer. We analyzed the association of MUC1 and venous thrombosis in a mouse tumor model and in patients with cancer. MATERIALS AND METHODS: We used a human pancreatic cancer cell line HPAF-II that expresses a high level of MUC1. We grew HPAF-II tumors in the pancreas of Crl:NU-Foxn1nu male mice. MUC1 in plasma and extracellular vesicles (EVs) isolated from plasma was measured using an enzyme-linked immunosorbent assay. MUC1 in EVs and venous thrombi from tumor-bearing mice was assessed by western blotting. We measured MUC1 in plasma from healthy controls and patients with stomach, colorectal or pancreatic cancer with or without venous thromboembolism. RESULTS AND DISCUSSION: MUC1 was detected in the plasma of mice bearing HPAF-II tumors and was associated with EVs. MUC1 was present in venous thrombi from mice bearing HFAP-II tumors. Recombinant MUC1 did not induce platelet aggregation. Levels of MUC1 were higher in patients with pancreatic cancer compared with healthy controls. In contrast to the mouse model, MUC1 was present in EV-free plasma in samples from healthy controls and patients with cancer. There was no significant difference in the levels of MUC1 in cancer patients with or without VTE. Our data did not find any evidence that MUC1 contributed to VTE in patients with cancer.

Von Willebrand Factor Antigen Levels Predict Poor Outcomes in Patients With Stroke and Cancer: Findings From the Multicenter, Prospective, Observational SCAN Study.

BACKGROUND: Patients with acute ischemic stroke and active cancer have more severe neurological symptoms, elevated risks of stroke recurrence, and death compared with the general population. We examined whether von Willebrand factor (vWF) antigen levels at stroke onset were associated with the poor outcomes of patients with stroke and cancer. METHODS AND RESULTS: Using data from 90 patients with acute ischemic stroke and active cancer who were registered in the SCAN (Ischemic Stroke in Patients With Cancer and Neoplasia) study, a prospective multicenter, observational study in Japan, we divided patients into 2 groups according to their median vWF antigen levels (high, n=46; or low, n=44). The high-vWF group had a significantly higher initial National Institutes of Health Stroke Scale score (median, 7 [interquartile range, 3-11.25] versus 3 [interquartile range, 1-8.5]; P<0.05) and a significantly higher incidence of cryptogenic stroke (32 [70%] versus 16 [36%]; P<0.01) and venous thromboembolism (7 [15%] versus 0 [0%]; P<0.01), as well as multiple lesions (28 [62%] versus 12 [27%]; P<0.001), than the low-vWF group. We observed no significant difference in the rate of stroke recurrence within 1 year between the groups. However, increased vWF levels were an independent predictor of death within 1 year of stroke onset, after adjusting for potential confounders (odds ratio, 6.77 [95% CI, 1.49-30.78]; P<0.05). CONCLUSIONS: Elevated vWF antigen levels were associated with adverse outcomes in patients with cancer-associated stroke and may represent a useful biomarker to guide future therapeutic interventions.

Tissue factor activates the coagulation cascade in mouse models of acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is associated with a high risk of bleeding and thrombosis. APL patients have an activated coagulation system, hyperfibrinolysis, and thrombocytopenia. APL cells express tissue factor (TF), a receptor and cofactor for factor VII/VIIa. This study had 2 goals. Firstly, we measured biomarkers of coagulation and fibrinolysis activation as well as platelet counts and bleeding in both mouse xenograft and allograft models of APL. Secondly, we determined the effect of inhibiting TF on the activation of coagulation in these models. We observed increased levels of plasma thrombin-antithrombin complexes (TAT), D-dimer, and plasmin-antiplasmin complexes, reduced platelet counts, and increased tail bleeding in both mouse models of APL. Fibrinogen levels decreased in the xenograft model but not in the allograft model. In contrast, the red blood cell count decreased in the allograft model but not in the xenograft model. Inhibition of APL-derived human TF with an anti-human TF monoclonal antibody reduced the level of TAT, increased platelet count, and normalized tail bleeding in a xenograft model. Inhibition of all sources of TF (APL cells and host cells) in the allograft model with a rat anti-mouse TF monoclonal antibody decreased the levels of TAT but did not affect the platelet count. Our study demonstrates that TF plays a central role in the activation of coagulation in both the xenograft and allograft mouse models of APL. These APL mouse models can be used to investigate the mechanisms of coagulopathy and thrombocytopenia in APL.

Role of Polymorphonuclear Myeloid-Derived Suppressor Cells and Neutrophils in Ischemic Stroke.

Background Immune cells play a vital role in the pathology of ischemic stroke. Neutrophils and polymorphonuclear myeloid-derived suppressor cells share a similar phenotype and have attracted increasing attention in immune regulation research, yet their dynamics in ischemic stroke remain elusive. Methods and Results Mice were randomly divided into 2 groups and intraperitoneally treated with anti-Ly6G (lymphocyte antigen 6 complex locus G) monoclonal antibody or saline. Distal middle cerebral artery occlusion and transient middle cerebral artery occlusion were applied to induce experimental stroke, and mice mortality was recorded until 28 days after stroke. Green fluorescent nissl staining was used to measure infarct volume. Cylinder and foot fault tests were used to evaluate neurological deficits. Immunofluorescence staining was conducted to confirm Ly6G neutralization and detect activated neutrophils and CD11b+Ly6G+ cells. Fluorescence-activated cell sorting was performed to evaluate polymorphonuclear myeloid-derived suppressor cell accumulation in brains and spleens after stroke. Anti-Ly6G antibody successfully depleted Ly6G expression in mice cortex but did not alter cortical physiological vasculature. Prophylactic anti-Ly6G antibody treatment ameliorated ischemic stroke outcomes in the subacute phase. Moreover, using immunofluorescence staining, we found that anti-Ly6G antibody suppressed activated neutrophil infiltration into parenchyma and decreased neutrophil extracellular trap formation in penumbra after stroke. Additionally, prophylactic anti-Ly6G antibody treatment reduced polymorphonuclear myeloid-derived suppressor cell accumulation in the ischemic hemisphere. Conclusions Our study suggested a protective effect of prophylactic anti-Ly6G antibody administration against ischemic stroke by reducing activated neutrophil infiltration and neutrophil extracellular trap formation in parenchyma and suppressing polymorphonuclear myeloid-derived suppressor cell accumulation in the brain. This study may provide a novel therapeutic approach for ischemic stroke.

Decreased Platelet Reactivity and Function in a Mouse Model of Human Pancreatic Cancer.

Cancer patients have increased thrombosis and bleeding compared with the general population. Cancer is associated with activation of both platelets and coagulation. Mouse models have been used to study the dysregulation of platelets and coagulation in cancer. We established a mouse model of pancreatic cancer in which tissue factor-expressing human pancreatic tumors (BxPC-3) are grown in nude mice. Tumor-bearing mice have an activated coagulation system and increased venous thrombosis compared to control mice. We also showed that tumor-derived, tissue factor-positive extracellular vesicles activated platelets ex vivo and in vivo. In this study, we determined the effect of tumors on a platelet-dependent arterial thrombosis model. Unexpectedly, we observed significantly reduced carotid artery thrombosis in tumor-bearing mice compared to controls. In addition, we observed significantly increased tail bleeding in tumor-bearing mice compared to controls. These results suggested that the presence of the tumor affected platelets. Indeed, tumor-bearing mice exhibited a significant decrease in platelet count and an increase in mean platelet volume and percentage of reticulated platelets, findings that are consistent with increased platelet turnover. Levels of the platelet activation marker platelet factor 4 were also increased in tumor-bearing mice. We also observed decreased platelet receptor expression in tumor-bearing mice and reduced levels of active αIIb/ß3 integrin in response to PAR4 agonist peptide and convulxin in platelets from tumor-bearing mice compared with platelets from control mice. In summary, our study suggests that in tumor-bearing mice there is chronic platelet activation, leading to thrombocytopenia, decreased receptor expression, and impaired platelet adhesive function.

Spontaneous malignant transformation of trigeminal schwannoma: consideration of responsible gene alterations for tumorigenesis-a case report.

Malignant peripheral nerve sheath tumors (MPNSTs) arising from the trigeminal nerves are extremely rare (only 45 cases, including the present case, have been published) and have been reported to develop de novo from the peripheral nerve sheath and are not transformed from a schwannoma or neurofibroma. Here, we report a case of MPNSTs of the trigeminal nerve caused by the malignant transformation of a trigeminal schwannoma, with a particular focus on genetic considerations. After undergoing a near-total resection of a histologically typical benign schwannoma, the patient presented with regrowth of the tumor 10 years after the primary excision. Histopathologic and immunochemical examinations confirmed the recurrent tumor to be an MPNST. Comprehensive genomic analyses (FoundationOne panel-based gene assay) showed that only the recurrent MPNST sample, not the initial diagnosis of schwannoma, harbored genetic mutations, including NF1-p.R2637* and TP53-p.Y234H, candidate gene mutations associated with malignant transformation. Moreover, the results of reverse transcription polymerase chain reaction showed that the fusion of SH3PXD2A and HTRA1, which has been reported as one of the responsible genetic aberrations of schwannoma, was detected in the recurrent tumor. Taken together, we could illustrate the accumulation process of gene abnormalities for developing MPNSTs from normal cells via schwannomas.

Loss of P2Y1 receptor desensitization does not impact hemostasis or thrombosis despite increased platelet reactivity in vitro.

BACKGROUND: The hemostatic plug formation at sites of vascular injury is strongly dependent on rapid platelet activation and integrin-mediated adhesion and aggregation. However, to prevent thrombotic complications, platelet aggregate formation must be a self-limiting process. The second-wave mediator adenosine diphosphate (ADP) activates platelets via Gq-coupled P2Y1 and Gi-coupled P2Y12 receptors. After ADP exposure, the P2Y1 receptor undergoes rapid phosphorylation-induced desensitization, a negative feedback mechanism believed to be critical for limiting thrombus growth. OBJECTIVE: The objective of this study was to examine the role of rapid P2Y1 receptor desensitization on platelet function and thrombus formation in vivo. METHODS: We analyzed a novel knock-in mouse strain expressing a P2Y1 receptor variant that cannot be phosphorylated beyond residue 340 (P2Y1340-0P), thereby preventing the desensitization of the receptor. RESULTS: P2Y1340-0P mice followed a Mendelian inheritance pattern, and peripheral platelet counts were comparable between P2Y1340-0P/340-0P and control mice. In vitro, P2Y1340-0P/340-0P platelets were hyperreactive to ADP, showed a robust activation response to the P2Y1 receptor-selective agonist, MRS2365, and did not desensitize in response to repeated ADP challenge. We observed increased calcium mobilization, protein kinase C substrate phosphorylation, alpha granule release, activation of the small GTPase Rap1, and integrin inside-out activation/aggregation. This hyperreactivity, however, did not lead to increased platelet adhesion or excessive plug formation under physiological shear conditions. CONCLUSION: Our studies demonstrate that receptor phosphorylation at the C-terminus is critical for P2Y1 receptor desensitization in platelets and that impaired desensitization leads to increased P2Y1 receptor signaling in vitro. Surprisingly, desensitization of the P2Y1 receptor is not required for limiting platelet adhesion/aggregation at sites of vascular injury, likely because ADP is degraded quickly or washed away in the bloodstream.

Genetic deletion of platelet PAR4 results in reduced thrombosis and impaired hemostatic plug stability.

BACKGROUND: Protease-activated receptor 4 (PAR4) is expressed by a wide variety of cells, including megakaryocytes/platelets, immune cells, cardiomyocytes, and lung epithelial cells. It is the only functional thrombin receptor on murine platelets. A global deficiency of PAR4 is associated with impaired hemostasis and reduced thrombosis. OBJECTIVE: We aimed to generate a mouse line with a megakaryocyte/platelet-specific deletion of PAR4 (PAR4fl/fl ;PF4Cre+ ) and use the mouse line to investigate the role of platelet PAR4 in hemostasis and thrombosis in mice. METHODS: Platelets from PAR4fl/fl ;PF4Cre+ were characterized in vitro. Arterial and venous thrombosis was analyzed. Hemostatic plug formation was analyzed using a saphenous vein laser injury model in mice with global or megakaryocyte/platelet-specific deletion of PAR4 or wild-type mice treated with thrombin or glycoprotein VI (GPVI) inhibitors. RESULTS: PAR4fl/fl ;PF4Cre+ platelets were unresponsive to thrombin or specific PAR4 stimulation but not to other agonists. PAR4-/- and PAR4fl/fl ;PF4Cre+ mice both exhibited a similar reduction in arterial thrombosis compared to their respective controls. More importantly, we show for the first time that platelet PAR4 is critical for venous thrombosis in mice. In addition, PAR4-/- mice and PAR4fl/fl ;PF4Cre+ mice exhibited a similar impairment in hemostatic plug stability in a saphenous vein laser injury model. Inhibition of thrombin in wild-type mice gave a similar phenotype. Combined PAR4 deficiency on platelets with GPVI inhibition did not impair hemostatic plug formation but further reduced plug stability. CONCLUSION: We generated a novel PAR4fl/fl ;PF4Cre+ mouse line. We used this mouse line to show that PAR4 signaling in platelets is critical for arterial and venous thrombosis and hemostatic plug stability.

MiRNA-132/212 regulates tight junction stabilization in blood-brain barrier after stroke.

MicroRNA-132/212 has been supposed as a critical gene related to the blood-brain barrier (BBB) protection after stroke, but its regulation pathway including the upstream regulator and downstream targets is still unclear. Herein, we demonstrated the cAMP response element-binding protein (CREB)-regulated transcription coactivator-1 (CRTC1) to be the upstream regulator of miRNA-132/212 using CRTC1 knockout and wild-type mice. CRTC1 deletion led to the reduction of miRNA-132/212 expression in mice brain after ischemic stroke, significantly increased infarct volume, and aggravated BBB permeability with worsening neurological deficits. Furthermore, we identified that miRNA-132 repressed Claudin-1, tight junction-associated protein-1 (TJAP-1), and RNA-binding Fox-1 (RBFox-1) by directly binding to their respective 3'-untranslated regions, which alleviated the ischemic damage by enhancing neuronal survival and BBB integrity. Moreover, the co-culture of endothelial cells with CRTC1-deficient neurons aggravated the cell vulnerability to hypoxia, also supporting the idea that miRNA-132/212 cluster is regulated by CRTC1 and acts as a crucial role in the mitigation of ischemic damage. This work is a step forward for understanding the role of miRNA-132/212 in neurovascular interaction and may be helpful for potential gene therapy of ischemic stroke.