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  • 1
    In: Arteriosclerosis, Thrombosis, and Vascular Biology, Ovid Technologies (Wolters Kluwer Health), Vol. 21, No. 9 ( 2001-09), p. 1531-1537
    Abstract: Mutations in the gene encoding thrombomodulin (TM), a thrombin regulator, are suspected risk factors for venous and arterial thrombotic disease. We have previously described the generation of TM Pro/Pro mice carrying a TM gene mutation that disrupts the TM-dependent activation of protein C. Here, it is shown that inbred C57BL/6J TM Pro/Pro mice exhibit a hypercoagulable state and an increased susceptibility to thrombosis and sepsis. Platelet thrombus growth after FeCl 3 -induced acute endothelial injury was accelerated in mutant mice. Vascular stasis after permanent ligation of the carotid artery precipitated thrombosis in mutant but not in normal mice. Mutant mice showed increased mortality after exposure to high doses of endotoxin and demonstrated altered cytokine production in response to low-dose endotoxin. The severity of the hypercoagulable state and chronic microvascular thrombosis caused by the TM Pro mutation is profoundly influenced by mouse strain-specific genetic differences between C57BL/6 and 129SvPas mice. These data demonstrate that in mice, TM is a physiologically relevant regulator of platelet- and coagulation-driven large-vessel thrombosis and modifies the response to endotoxin-induced inflammation. The phenotypic penetrance of the TM Pro mutation is determined by as-yet-uncharacterized genetic modifiers of thrombosis other than TM.
    Type of Medium: Online Resource
    ISSN: 1079-5642 , 1524-4636
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2001
    detail.hit.zdb_id: 1494427-3
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  • 2
    In: Blood, American Society of Hematology, Vol. 120, No. 21 ( 2012-11-16), p. 1045-1045
    Abstract: Abstract 1045 In patients with FLT3-ITD mutated AML, FLT3-inhibitors have been used successfully as a ‘bridging therapy’ before allogeneic transplantation. Inhibitors of other kinases (such as imatinib for BCR-ABL positive CML) have previously been used successfully after allogeneic transplantation – even before discontinuation of immunosuppressive medication. However, it is known that some BCR-ABL inhibitors such as dasatinib exert strong inhibitory effects on primary T-cells through inhibition of Src-kinases relevant for T-cell receptor signaling. Even imatinib and nilotinib - although not affecting Src kinase activity – showed decreased T-cell activation and reactivity to some extent. Thus, the influence of FLT3-kinase inhibitors on T-cell function may be critical in the context of allogeneic bone marrow transplantation for FLT3-ITD-positive AML. Besides inhibition of FLT3-kinase, midostaurin (PKC412) exerts activity against PDGFR, VEGFR or c-KIT. In contrast, second generation inhibitors such as quizartinib (AC220) act in a far more FLT3-specific manner. Therefore, we aimed to investigate the effects of both clinically relevant FLT3-inhibitors on T-cell receptor signaling in comparison to the well characterized and potent BCR-ABL inhibitor dasatinib. Investigating primary T-cells derived from healthy donors, we applied a dose range of 10–50 nM dasatinib, 5–50nM midostaurin and 10–50 nM quizartinib. These dose ranges have been previously described to be achievable as trough levels during inhibitor therapy in early clinical trials. Upon incubation with dasatinib (10nM and 50nM), we found overall reduction in global tyrosine phosphorylation as detected by Western-blotting using the 4G10 antibody. In contrast, treatment with midostaurin left the activation of T-cell receptor signaling pathways unaffected. Comparable to DMSO control, overall phosphorylation was induced almost immediately after stimulation. Western-blotting of LCK and Plcg1 showed similar time dependent activation compared to total phosphorylation. Likewise, quizartinib did not reduce overall tyrosine phosphorylation level and left activation of downstream kinases (ZAP70, MAPK, LCK, Plcg1) largely unaffected. As activation of primary T-cells is a critical step in immune responses against viral and tumor antigens we aimed to investigate the influence of FLT3-kinase inhibitors quizartinib and midostaurin on activation of CD8+ T-cells. T-cells from healthy donors were stimulated using either PHA 0.5% or CD3/CD28 beads to ensure a more T-cell receptor specific stimulation. Using CD3/CD28 stimulation, CD69 expression was almost abrogated following dasatinib treatment. Applying clinically relevant doses of midostaurin or quizartinib to isolated T-cells did not influence CD69 expression. Expression levels upon PHA or CD3/CD28 stimulation were comparable to DMSO-control - even in the presence of 50nM midostaurin or quizartinib. Proliferation of T-cells upon CD3/CD28 stimulation was impaired by dasatinib treatment, while midostaurin and quizartinib left T-cell proliferation largely unaffected – as determined by CSFE staining. In order to investigate the T cell allo-reactivity, mixed lymphocyte culture was performed, where human pan-T-cells are co-cultured with allogeneic antigen presenting cells. T-cell proliferation – as measured by 3H-thymidine incorporation – was significantly impaired by dasatanib but neither midostaurin nor quizartinib treatment. Investigation of leukemia- and virus-antigen-specific T-cell responses are currently under way to gain deeper insight regarding this clinically relevant scenario. Overall, we found FLT3-kinase inhibitors midostaurin and quizartinib to leave T-cell activation, proliferation and function unaffected in-vitro. This information may be useful for the design of up-coming clinical trials testing the safety and efficacy of FLT3-kinase inhibitors in combination with allogeneic stem-cell transplantation. Disclosures: Lipka: Novartis Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Heidel:Novartis Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2012
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 3
    In: Blood, American Society of Hematology, Vol. 124, No. 21 ( 2014-12-06), p. 1410-1410
    Abstract: Inhibitors of JAK2-kinase (Ruxolitinib, Momelotinib) are already approved or currently investigated in advanced clinical trials for treatment of myeloproliferative neoplasia (MPN). Besides their effect on mutated JAK2-kinase these compounds inhibit wildtype JAK and thereby impair JAK-STAT-signaling, which is an important pathway for proliferation and activation of other cell types such as human T-cells. Accumulating evidence suggests that they may also exert substantial immunosuppressive activity. Very recent reports highlighting hepatitis B reactivation complemented the series of severe infections in ruxolitinib-treated patients among which cryptococcus neoformans pneumonia, toxoplasmosis retinitis, disseminated tuberculosis, and progressive multifocal leukencephalopathy are the most alarming. We hypothesized that JAK-kinase inhibitors may act as immunosuppressant drugs by impairment of T-cell responses through inhibition of T-cell signaling (JAK-STAT pathway) and that specificity of JAK-kinase inhibition may be of major importance for the degree of T-cell inhibition. Therefore we investigated the effects of pharmacological JAK-kinase inhibition on healthy donor (HD-) and MPN patient T-cells. Selective inhibitors of JAK2-kinase (BSK805) and JAK3-kinase (BQM245) as well as clinically relevant inhibitors of JAK1/2-kinases (Ruxolitinib and Momelotinib) were used for pharmacologic inhibition. The SRC-kinase inhibitor Dasatinib served as a positive control for T-cell inhibition. Knockdown of specific JAK-kinases by RNAi was used to control for target specificity. In regard to T-cell receptor (TCR)-mediated signaling we investigated bona fide signaling molecules downstream of the TCR by Western Blotting. Besides SRC-kinases like LCK also ZAP70, PLCG1 and the MAPK/ERK pathway have been described to play a pivotal role in T-cell activation. In our data set, selectivity of JAK-kinase inhibition (JAK2, JAK3 or JAK1/2) influenced TCR-signaling in regard to overall tyrosine phosphorylation but also in regard to downstream effectors such as ERK. As activation and proliferation of primary T-cells is a critical step in immune responses against viral and tumor antigens we aimed to investigate the influence of JAK-kinase inhibition on activation and proliferation of human T-cells. T-cells from healthy donors were stimulated using either PHA 0.5% or CD3/CD28 beads to ensure a more T-cell receptor specific stimulation. CD69 expression was used as a marker for T-cell activation and CFSE staining was applied to assess for T-cell proliferation. Using CD3/CD28 stimulation, CD69 expression was almost abrogated following Dasatinib treatment and proliferation was significantly reduced. Applying relevant doses of specific JAK2 and JAK3 inhibitors to isolated T-cells did neither influence CD69 expression nor T-cell proliferation. These findings are confirmed by RNAi. In contrast, clinically relevant doses of JAK1/2 inhibitors Ruxolitinib and Momelotinib, respectively reduced CD69 expression and T-cell proliferation. Likewise, T-cells derived from MPN patients treated with Ruxolitinib revealed decreased CD69 expression and decreased proliferative capacity upon stimulation, compared to untreated patients or HD-controls. In order to investigate T-cell function, we assessed for allo-reactivity in a mixed lymphocyte culture. Human pan-T-cells were co-cultured with allogeneic antigen presenting cells. T-cell reactivity – as measured by 3H-thymidine incorporation – was significantly impaired by Ruxolitinib and Momelotinib. Specific inhibition of JAK2 or JAK3 kinase, however, did not affect T-cell reactivity. These effects could be confirmed using T-cells derived from Ruxolitinib-treated MPN patients. Investigation of leukemia- and virus-antigen-specific T-cell responses are currently under way to gain deeper insight regarding this clinically relevant scenario. Taken together, specificity of JAK-kinase inhibition influences the inhibitory potential on T-cell function. JAK1 kinase seems to play an important role in T-cell activation, as unspecific inhibitors of JAK1 & JAK2 Kinase inhibit T-cell function while selective inactivation of JAK2 kinase leaves T-cell function almost unaffected. Heterogeneity in T-cell function of Ruxolitinib-treated patients is an important finding that deserves detailed investigation. Disclosures Heidel: Novartis: Consultancy.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2014
    detail.hit.zdb_id: 1468538-3
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  • 4
    In: Diabetes Care, American Diabetes Association, Vol. 29, No. 1 ( 2006-01-01), p. 89-94
    Abstract: OBJECTIVE—We studied the association between polymorphisms in the UCP genes and diabetes complications in patients with type 1 diabetes. RESEARCH DESIGN AND METHODS—We analyzed 227 patients with type 1 diabetes using PCR and subsequent cleavage by restriction endonucleases for the promoter variants A-3826G in the UCP1 gene, G-866A in the UCP2 gene, and C-55T in the UCP3 gene. RESULTS—No effect of the A-3826G polymorphism in the UCP1 gene on diabetes complications was found. Patients who were heterozygous or homozygous for the G-866A polymorphism in the UCP2 gene or the C-55T polymorphism in the UCP3 gene had a significantly reduced prevalence of diabetic neuropathy (UCP2: odds ratio 0.44 [95% CI 0.24–0.79], P = 0.007; UCP3: 0.48 [0.25–0.92] , P = 0.031), whereas there was no association with other diabetes complications. This effect was stronger when G-866A and C-55T occurred in a cosegregatory manner (UCP2 and UCP3: 0.28 [0.12–0.65], P = 0.002). Furthermore, a multiple logistic regression model showed an age- and diabetes duration–independent effect of the cosegregated polymorphisms on the prevalence of diabetic neuropathy (P = 0.013). CONCLUSIONS—Our data indicate that both the G-866A polymorphism in the UCP2 gene and the C-55T polymorphism in the UCP3 gene are associated with a reduced risk of diabetic neuropathy in type 1 diabetes. Thus, the results presented here support the hypothesis that higher expression of uncoupling protein might prevent mitochondria-mediated neuronal injury and, ultimately, diabetic neuropathy.
    Type of Medium: Online Resource
    ISSN: 0149-5992 , 1935-5548
    Language: English
    Publisher: American Diabetes Association
    Publication Date: 2006
    detail.hit.zdb_id: 1490520-6
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  • 5
    Online Resource
    Online Resource
    American Society of Hematology ; 2011
    In:  Blood Vol. 118, No. 21 ( 2011-11-18), p. 2204-2204
    In: Blood, American Society of Hematology, Vol. 118, No. 21 ( 2011-11-18), p. 2204-2204
    Abstract: Abstract 2204 Introduction: Previously it has been shown that activated protein C (APC) protects against diabetic nephropathy (DN). APC's cytoprotective effect in DN may be related to its in vitro ability to downregulate reactive oxygen species (ROS) and maintain mitochondrial membrane potential in glucose stressed cells. Cellular targets, through which APC, an extracellular serine protease, regulates mitochondrial function, are unknown. Since mice lacking the ROS-inducing mitochondrial protein p66shc are protected from DN we hypothesized that APC's cytoprotective effect may be mechanistically linked to p66shc. Material & methods: Immortalized mouse podocytes and murine endothelial cells were stressed in vitro with glucose (30 mM). In mice persistent hyperglycaemia was induced by streptozotocin injections. Markers of DN were analysed in wild-type mice, mice expressing a thrombomodulin (TM) mutant lacking cofactor activity towards protein C activation (TMPro/Pro), mice expressing high levels of APC (hPChigh), and p66−/− x TMPro/Pro double mutant mice. Immunoblotting, RT-PCR, cellular subfractionation, immunohistochemistry and immunofluorescensce were employed for analyses. Results: 8-OH-Desoxyguanosine, a marker for ROS, is induced in diabetic mice. Nitrotyrosine, a marker for ROS-dependent damage, localizes mainly to podocytes. This is paralleled by p66shc-upregulation in glomerular podocytes. These effects are aggravated in diabetic TMPro/Pro, ameliorated in aPChigh, and reversed in p66shc x TMPro/Pro mice. In vitro APC counteracts glucose dependent upregulation of p66shc and inhibits mitochondrial translocation of p66shc in mouse podocytes, but not in endothelial cells in vitro. Conclusion: This study identifies a novel mechanism through which APC mediates cytoprotection. In glucose stressed podocytes, but not endothelial cells, APC prevents mitochondrial translocation of the ROS-inducing redox-protein p66shc, which is required for protection against DN in vivo. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2011
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 6
    In: Blood, American Society of Hematology, Vol. 122, No. 21 ( 2013-11-15), p. 4589-4589
    Abstract: Acute graft-versus-host disease (GVHD) is a major complication after allogeneic stem cell transplantation (allo-SCT). With the current treatment approaches focussing on escalating immunosuppression, mortality rates of therapy-refractory disease courses are approx. 80-90%, underlining the medical need for novel therapeutic concepts. The pathophysiology of refractory GVHD is incompletely understood, however, recent evidence points towards a crucial role for endothelial damage. We have previously shown that steroid-refractory GVHD associates with increasing serum thrombomodulin (TM) levels 1, 2 and loss of endothelial TM expression 3, a constellation that indicates endothelial stress. However prior to allo-SCT, baseline TM levels did not predict steroid-refractory GVHD or survival. We hypothesized that endothelial vulnerability caused by single nucleotide polymorphisms within the TM gene (THBD) is a risk factor for refractory GVHD predicting outcome after allo-SCT. Patients and Methods Seven SNPs within the THBD gene were studied (rs1962.TC, rs1042579.TC, rs1042580.AG, rs3176123.TG, rs3176124GA, rs3176126.GA and rs3176134.CT) in a training cohort of 465 allografted patients. The relevant genotypes were then re-assessed in an independent validation cohort (n=386). Results Allele frequencies of seven THBD SNPs allowed meaningful statistical correlation with outcome after allo-SCT. An increased risk of non-relapse mortality (NRM) was associated with three SNPs: rs1962.CC, rs1042579.TT (455V) and rs1042580.GG. When patients were divided into risk cohorts (one vs. no high-risk SNP), a strong correlation with NRM was observed in both cohorts (training cohort: p=0.002, HR 2.32 CI 1.36-3.95; validation cohort: p=0.007, HR 2.13, CI 1.23-3.70) (Figure 1). NRM was predicted by THBD SNPs in particular for patients who later develop GVHD (validation cohort: p=0.00056, HR 3.03 CI 5.68-1.61, training cohort: p=0.012, HR 2.38 CI 1.21-4.69) but not in patients without GVHD. In contrast, THBD SNPs did not predict incidence of acute GVHD. Multivariate analyses adjusting for clinical variables confirmed the independent effect of THBD SNPs on NRM in both cohorts. Conclusions Our results demonstrate that THBD-SNPs predict mortality of GVHD patients without influencing GVHD incidence. This supports our hypothesis that endothelial vulnerability contributes to therapy refractory courses of the disease. Rather than focussing on the escalation of combinations of (endothelial cell toxic) immunosuppressive drugs, therapeutic approaches aiming at endothelial protection should be evaluated. 1. Dietrich S, Falk CS, Benner A, et al. Endothelial vulnerability and endothelial damage are associated with risk of graft-versus-host disease and response to steroid treatment. Biol Blood Marrow Transplant 2013; 19(1): 22-7. 2. Luft T, Dietrich S, Falk C, et al. Steroid-refractory GVHD: T-cell attack within a vulnerable endothelial system. Blood 2011; 118(6): 1685-92. 3. Andrulis M, Dietrich S, Longerich T, et al. Loss of endothelial thrombomodulin predicts response to steroid therapy and survival in acute intestinal graft-versus-host disease. Haematologica 2012; 97(11): 1674-7. Disclosures: Dreger: Riemser Pharma : Consultancy, Honoraria, Research Funding.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2013
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 7
    In: Blood, American Society of Hematology, Vol. 102, No. 9 ( 2003-11-01), p. 3085-3092
    Abstract: Sepsis is associated with systemic inflammation, coagulopathy, and disrupted protein C (PC) pathway function. The effect of prothrombotic polymorphism, factor V Leiden (Arg506Gln; FV Leiden), was examined in a large clinical trial (PROWESS) of severe sepsis and a mouse endotoxemia model. In PROWESS, 4.1% (n = 65) of patients were heterozygous FV Leiden (VL+/–) carriers. The 28-day mortality was lower in VL+/– (13.9%) than in non-FV Leiden (VL–/–; 27.9%) patients (P = .013). The mortality benefit of recombinant human activated PC (rhAPC) treatment was similar in VL+/– (placebo, 15.6%; rhAPC,12.1%) and VL–/– patients (placebo, 31.0%; rhAPC, 24.7%; interaction P = .981). VL+/– status did not appear to influence baseline biomarkers of coagulopathy and inflammation or disease severity, with the exception that vasopressor usage was less in VL+/– patients (46.2% versus 63.0%; P = .009). In a median lethal dose (40 mg/kg) endotoxin mouse model, VL+/– mice had lower mortality than wild-type mice (19% versus 57%; P = .008), whereas the mortality of homozygous (VL+/+) mice was almost identical to that of wild-type mice (65% versus 57%; P = .76). The findings suggest that FV Leiden constitutes a rare example of a balanced gene polymorphism that maintains the FV Leiden mutation in the general gene pool due to a survival advantage of VL+/– in severe sepsis.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2003
    detail.hit.zdb_id: 1468538-3
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  • 8
    In: Blood, American Society of Hematology, Vol. 118, No. 21 ( 2011-11-18), p. 1012-1012
    Abstract: Abstract 1012 Graft-versus-host disease (GvHD) is the major complication of allogeneic stem cell transplantation (alloSCT) and its therapy-resistant form causes significant morbidity and mortality. The pathomechanism of steroid resistance is currently not completely understood; however, we have recently suggested that endothelial dysfunction seems to play an important role (Luft et al., Blood 2011). The aim of this study was to validate in a large cohort of patients that steroid refractory acute GvHD is associated with endothelial stress. Secondly we assessed if this endothelial stress can be overcome by statins, which are known to have endothelial protective effects. We have therefore performed a retrospective study of 393 patients who underwent alloSCT in our institution between 2002–2010. Endothelial stress serum markers were correlated with the course of GvHD, non relapse mortality (NRM) and statins intake. Overall, 169 of 393 patients (43%) developed GVHD. Of these, 101 patients (60%) had steroid-sensitive GvHD grade 1–2, 26 patients (15%) steroid-sensitive GvHD grade 3–4 and 42 patients (25%) had steroid-refractory GvHD which was always grade 3–4 at its maximum severity. 224 patients had no signs of GvHD. In order to elucidate the pathomechanisms that contribute to steroid resistance, serum markers of endothelial stress and vascular growth (Angiopoietin-2 (ANG2), IL-8, soluble thrombomodulin (sTM), and vascular endothelial growth factor (VEGF)) were measured by ELISA and multiplex assays before and on days +50 and +100 after alloSCT. RESULTS: Landmark analyses at days +50 and +100 after alloSCT showed that NRM was dramatically high in the steroid refractory group but was equivalently low in the no GvHD-, sensitive grade 1–2 - and grade 3–4 - groups (p 〈 0.001, Figure 1). ANG2, a mediator of endothelial cell vulnerability, measured before transplant was predictive for a steroid refractory course of GvHD (p=0.05) and higher NRM (p=0.06) under the prerequisite that patients developed grade 3–4 GvHD. Moreover, patients who developed an acute steroid refractory GvHD displayed significantly higher levels of the endothelial stress markers IL-8 (day +50: p 〈 0.001; day +100: p 〈 0.001) and sTM (day +50: p 〈 0.009; day +100: p=0.003) compared to steroid-sensitive GvHD patients and patients with no GvHD. High levels of sTM, IL8 and ANG2 were significantly associated with increased NRM rates (day +50: IL8 p=0.02, sTM p=0.0008, ANG2 p=0.0001; day +100: IL8 p=0.0007, sTM p 〈 0.0001, ANG2 p=0.05); even after multivariate adjustment for donor, conditioning intensity, disease status at alloSCT and sex mismatch. In contrast, no influence of VEGF levels on steroid-refractory GvHD. When IL8, sTM, ANG2 and VEGF kinetics were compared in patients with and without concomitant statin therapy (n=81), no differences were observed in the whole patient cohort nor in the subset with steroid-refractory GVHD. Consequently, patients with or without statins had similar NRM, relapse rates and overall survival in univariate as well as multivariate analysis. CONCLUSION: This supports the hypothesis that steroid-refractory GVHD is associated with progressive microangiopathy. Statins, although reported to have protective effects on endothelial cells, were inefficient to alleviate endothelial stress in this context and, accordingly, did not change the outcome of acute GVHD patients. Disclosures: Luft: Celgene: Research Funding.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2011
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 9
    In: Blood, American Society of Hematology, Vol. 103, No. 5 ( 2004-03-01), p. 1728-1734
    Abstract: Elevated plasma levels of fibrinogen are associated with the presence of cardiovascular disease, but it is controversial whether elevated fibrinogen causally imparts an increased risk, and as such is a true modifier of cardiovascular disease, or is merely associated with disease. By investigating a transgenic mouse model of hyperfibrinogenemia, we show that elevated plasma fibrinogen concentration (1) elicits augmented fibrin deposition in specific organs, (2) interacts with an independent modifier of hemostatic activity to regulate fibrin turnover/deposition, (3) exacerbates neointimal hyperplasia in an experimental model of stasis-induced vascular remodeling, yet (4) may suppress thrombin generation in response to a procoagulant challenge. These findings provide direct experimental evidence that hyperfibrinogenemia is more than a by-product of cardiovascular disease and may function independently or interactively to modulate the severity and/or progression of vascular disease.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2004
    detail.hit.zdb_id: 1468538-3
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  • 10
    Online Resource
    Online Resource
    American Society of Hematology ; 2012
    In:  Blood Vol. 120, No. 21 ( 2012-11-16), p. 3354-3354
    In: Blood, American Society of Hematology, Vol. 120, No. 21 ( 2012-11-16), p. 3354-3354
    Abstract: Abstract 3354 Diabetic nephropathy (DN) is a multifactorial disease associated with substantial changes in the haemostatic system. A hallmark of diabetes induced haemostatic dysfunction is impaired thrombomodulin (TM) dependent-protein C (PC) activation. Impaired PC activation triggers glomerular podocyte and endothelial cell dysfunction, thus promoting DN. The intracellular mechanism through which loss of TM and PC activation contributes to DN is not known. Here we show that the haemostatic mediator activated PC (aPC) regulates cellular homeostasis by inhibiting hyperglycemia induced endoplasmic reticulum (ER)-stress in DN. Hyperglycaemia was induced in wild-type (wt) mice or mice with altered activity of the TM-PC system (loss of function secondary to impaired PC activation (TMPro/LacZ) or gain of function with high aPC plasma levels (APChigh)). Subsets of diabetic mice were treated with the chemical ER-chaperone TUDCA. After 26 weeks of persistent hyperglycaemia markers of DN were determined and tissue samples were isolated for ex vivo analysis. Supplementary in vitro assays were performed in podocytes and endothelial cells. Persistent hyperglycaemia in wt mice caused severe ER-stress and DN. Ex vivo analysis of transcription factors regulating the ER-stress response showed an increase of the ER-stress markers CHOP and ATF6, while nuclear translocation of the highly conserved transcription factor X-box binding protein-1 (XBP1) was reduced in DN. These changes were aggravated in diabetic TMPro/LacZ mice. Conversely, in a mouse model with constitutively higher aPC levels (APChigh mice) nuclear levels of XBP1 were normalized and expression of ATF6 and CHOP was reduced despite persistent hyperglycaemia. In addition, aPC reverses the pathological ER-stress alterations in diabetic TMPro/LacZ mice. Pharmacological inhibition of ER-stress by TUDCA normalized nuclear levels of XBP1, inhibited CHOP/ATF6 expression, and protected against DN in diabetic wt and TMPro/LacZ mice. In vitro hyperglycaemia inhibited nuclear translocation of XBP1 in endothelial cells and podocytes, the two cellular components of glomerular filtration barrier. Activated PC directly promotes the nuclear translocation of XBP1 in these cells, which is required to inhibit hyperglycaemia induced ER-stress. Deletion of XBP1 in podocyte or endothelial cells abolished the cytoprotective effect of aPC. Furthermore, aPC regulates the interaction of PI3K regulatory subunit p85α with XBP1 which is known to mediate its nuclear translocation and diminished hyperglycaemia induced ER-stress. These studies demonstrate that hyperglycemia induced ER-stress is causally linked to DN and establish a novel link between haemostatic system and ER function in regulating cellular homeostasis in chronic kidney disease. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2012
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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