scholarly journals The serum- and glucocorticoid-inducible kinase 1 (SGK1) influences platelet calcium signaling and function by regulation of Orai1 expression in megakaryocytes

Blood ◽  
2012 ◽  
Vol 119 (1) ◽  
pp. 251-261 ◽  
Author(s):  
Oliver Borst ◽  
Eva-Maria Schmidt ◽  
Patrick Münzer ◽  
Tanja Schönberger ◽  
Syeda T. Towhid ◽  
...  

Abstract Platelets are activated on increase of cytosolic Ca2+ activity ([Ca2+]i), accomplished by store-operated Ca2+ entry (SOCE) involving the pore-forming ion channel subunit Orai1. Here, we show, for the first time, that the serum- and glucocorticoid-inducible kinase 1 (SGK1) is expressed in platelets and megakaryocytes. SOCE and agonist-induced [Ca2+]i increase are significantly blunted in platelets from SGK1 knockout mice (sgk1−/−). Similarly, Ca2+-dependent degranulation, integrin αIIbβ3 activation, phosphatidylserine exposure, aggregation, and in vitro thrombus formation were significantly impaired in sgk1−/− platelets, whereas tail bleeding time was not significantly enhanced. Platelet and megakaryocyte Orai1 transcript levels and membrane protein abundance were significantly reduced in sgk1−/− mice. In human megakaryoblastic cells (MEG-01), transfection with constitutively active S422DSGK1 but not with inactive K127NSGK1 significantly enhanced Orai1 expression and SOCE, while effects reversed by the SGK1 inhibitor GSK650394 (1μM). Transfection of MEG-01 cells with S422DSGK1 significantly increased phosphorylation of IκB kinase α/β and IκBα resulting in nuclear translocation of NF-κB subunit p65. Treatment of S422DSGK1-transfected MEG-01 cells with the IκB kinase inhibitor BMS-345541 (10μM) abolished SGK1-induced increase of Orai1 expression and SOCE. The present observations unravel SGK1 as novel regulator of platelet function, effective at least in part by NF-κB–dependent transcriptional up-regulation of Orai1 in megakaryocytes and increasing platelet SOCE.

2020 ◽  
Vol 4 (4) ◽  
pp. 638-643
Author(s):  
Manuel Salzmann ◽  
Sonja Bleichert ◽  
Bernhard Moser ◽  
Marion Mussbacher ◽  
Mildred Haase ◽  
...  

Abstract Platelets are small anucleate cells that release a plethora of molecules to ensure functional hemostasis. It has been reported that IκB kinase 2 (IKK2), the central enzyme of the inflammatory NF-κB pathway, is involved in platelet activation, because megakaryocyte/platelet-specific deletion of exons 6 and 7 of IKK2 resulted in platelet degranulation defects and prolonged bleeding. We aimed to investigate the role of IKK2 in platelet physiology in more detail, using a platelet-specific IKK2 knockout via excision of exon 3, which makes up the active site of the enzyme. We verified the deletion on genomic and transcriptional levels in megakaryocytes and were not able to detect any residual IKK2 protein; however, platelets from these mice did not show any functional impairment in vivo or in vitro. Bleeding time and thrombus formation were not affected in platelet-specific IKK2-knockout mice. Moreover, platelet aggregation, glycoprotein GPIIb/IIIa activation, and degranulation were unaltered. These observations were confirmed by pharmacological inhibition of IKK2 with TPCA-1 and BMS-345541, which did not affect activation of murine or human platelets over a wide concentration range. Altogether, our results imply that IKK2 is not essential for platelet function.


1991 ◽  
Vol 65 (04) ◽  
pp. 355-359 ◽  
Author(s):  
E Gray ◽  
J Watton ◽  
S Cesmeli ◽  
T W Barrowcliffe ◽  
D P Thomas

SummaryThe in vitro anticoagulant activities of recombinant desulphatohirudin (r-hirudin) were studied in the activated partial thromboplastin time (APTT) and the thrombin generation test : systems. In the APTT at concentrations below 5 μg/ml, r-hirudin showed a dose-response curye. At concentrations above 5 μg/ml, the plasma became unclottable, but in the thrombin generation test , at least 10 μg/ml of r-hirudin was required for full inhibition of thrombin generation. The antithrombotic effect was assessed using a rabbit venous stasis model; 150 μg/ml r-hirudin completely prevented thrombus formation at 10 and 20 min stasis. At antithrombotic dose, the mean bleeding time ratio measured in a rabbit ear template model, was not prolonged over control values. At higher doses, the bleeding time ratios were higher than those observed for the same dosage of heparin. These data indicate that while r-hirudin is an effective antithrombotic agent, antithrombotic doses have to be carefully titrated to avoid excessive bleeding.


Hypertension ◽  
2014 ◽  
Vol 64 (suppl_1) ◽  
Author(s):  
Hongmei Peng ◽  
Oscar Carretero ◽  
Xiao-Ping Yang ◽  
Pablo Nakagawa ◽  
Jiang Xu ◽  
...  

Elevated interleukin-4 (IL-4) levels are positively related to cardiac fibrosis in heart failure and hypertension. Using Balb/c exhibiting high circulating IL-4, Balb/c- Il4 tm2Nnt (IL-4 knockout with Balb/c background, IL-4 -/- ) and C57BL/6 mice, as well as cultured cardiac fibroblasts (CFs), we hypothesized that 1) high levels of IL-4 result in cardiac fibrosis, making the heart susceptible to angiotensin II (Ang II)-induced damage, and 2) IL-4 potently stimulates collagen production by CFs. Each strain (9- to 12-week old male) received vehicle or Ang II (1.4 mg/kg/day, s.c. via osmotic mini-pump) for 8 weeks. Cardiac fibrosis and function were determined by histology and echocardiography, respectively. Compared to C57BL/6, Balb/c mice had doubled interstitial collagen in the heart, enlarged left ventricle and decreased cardiac function along with elevated cardiac IL-4 protein (1.00±0.08 in C57BL/6 vs 2.61±0.46 in Balb/c, p <0.05); all those changes were significantly attenuated in IL-4 -/- (Table 1). Ang II further deteriorated cardiac fibrosis and dysfunction in Balb/c; these detrimental effects were attenuated in IL-4 -/- , although the three strains had a similar level of hypertension. In vitro study revealed that IL-4Rα was constitutively expressed in CFs (Western blot), and IL-4 potently stimulated collagen production by CFs (hydroxproline assay, from 18.89±0.85 to 38.81±3.61 μg/mg at 10 ng/ml, p <0.01). Our study demonstrates for the first time that IL-4, as a potent pro-fibrotic cytokine in the heart, contributes to cardiac fibrotic remodeling and dysfunction. Thus IL-4 may be a potential therapeutic target for cardiac fibrosis and dysfunction.


2021 ◽  
Vol 22 (23) ◽  
pp. 12921
Author(s):  
Irina Giralt ◽  
Gabriel Gallo-Oller ◽  
Natalia Navarro ◽  
Patricia Zarzosa ◽  
Guillem Pons ◽  
...  

The Wnt/β-catenin signaling pathway plays a pivotal role during embryogenesis and its deregulation is a key mechanism in the origin and progression of several tumors. Wnt antagonists have been described as key modulators of Wnt/β-catenin signaling in cancer, with Dickkopf-1 (DKK-1) being the most studied member of the DKK family. Although the therapeutic potential of DKK-1 inhibition has been evaluated in several diseases and malignancies, little is known in pediatric tumors. Only a few works have studied the genetic inhibition and function of DKK-1 in rhabdomyosarcoma. Here, for the first time, we report the analysis of the therapeutic potential of DKK-1 pharmaceutical inhibition in rhabdomyosarcoma, the most common soft tissue sarcoma in children. We performed DKK-1 inhibition via shRNA technology and via the chemical inhibitor WAY-2626211. Its inhibition led to β-catenin activation and the modulation of focal adhesion kinase (FAK), with positive effects on in vitro expression of myogenic markers and a reduction in proliferation and invasion. In addition, WAY-262611 was able to impair survival of tumor cells in vivo. Therefore, DKK-1 could constitute a molecular target, which could lead to novel therapeutic strategies in RMS, especially in those patients with high DKK-1 expression.


2018 ◽  
Vol 19 (8) ◽  
pp. 2306 ◽  
Author(s):  
Tong-Dan Liu ◽  
Shen-Hong Ren ◽  
Xue Ding ◽  
Zhou-Ling Xie ◽  
Yi Kong

Integrin αIIbβ3 plays a pivotal role in platelet aggregation. Three αIIbβ3 antagonists have been approved by the Food and Drug Administration (FDA) for the treatment of cardiovascular diseases. Unfortunately, all of these three drugs can cause the side effect of severe bleeding. Therefore, developing a new αIIbβ3 antagonist with low bleeding was needed. In the present study, we screened compounds by using a fibrinogen/integrin αIIbβ3 enzyme-linked immunosorbent assay (ELISA), and a novel αIIbβ3 antagonist ANTP266 was attained. The antithrombotic effects of ANTP266 were estimated by using two animal models, the bleeding risk was estimated by using a mice tail cutting assay, and the plasma half-life time was tested by LC-MS/MS. The results showed that ANTP266 potently decreased thrombosis formation, while not prolonging bleeding time at its effective dosage. The bleeding of ANTP266 reduced rapidly as time went on from 5 to 60 min, but tirofiban produced high bleeding continuously. The plasma half-life of ANTP266 in rats was 10.8 min. Taken together, ANTP266 is an effective antithrombotic agent with a low bleeding risk. The shorter bleeding time benefits from its short plasma half-life. ANTP266 could be a candidate for developing the αIIbβ3 antagonist of rapid elimination for a patient undergoing percutaneous coronary intervention.


Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3501-3501
Author(s):  
Jiansong Huang ◽  
Xiaofeng Shi ◽  
Wenda Xi ◽  
Ping Liu ◽  
Xiaodong Xi

Abstract The RGT sequences of the integrin β3 tail directly and constitutively bind the inactive c-Src, regulating integrin αIIbβ3 signaling and platelet function. Previous work has shown that disrupting the interaction of c-Src with β3 via myristoylated RGT peptide or deletion of the RGT sequences in β3 selectively inhibits integrin αIIbβ3 outside-in signaling in platelets. However, the precise molecular mechanisms by which the Src-β3 association regulates integrin αIIbβ3 signaling need to be clarified. We found that active c-Src phosphoylated the Y747 and Y759 residues of β3 directly at the in vitro protein/protein level or in CHO cell models bearing Tac-β3 chimeras, which were devoid of the intact β3 signal transduction. Furthermore, data from mass spectrometry, [γ-32P] ATP incorporation assays and CHO cell/Tac-β3 chimeras demonstrated that the direct phosphorylation of Y747 and Y759 by active c-Src did not depend on the binding of c-Src to the RGT sequences of the β3 tail. To further investigate the biological functions of Src-β3 association in signal transduction we employed a cell-permeable and reduction-sensitive peptide (myr-AC∼CRGT), which disrupted the Src-β3 association in platelets independent of membrane-anchorage, and found that when platelets were stimulated by thrombin the c-Src activation and the phosphorylation of the tyrosine residues of the β3 tail were substantially inhibited by the presence of the peptide. These results suggest that one of the crucial biological functions of Src-β3 association is to serve as a “bridge” linking integrin signaling with the c-Src full activation and phosphorylation of the tyrosines of the β3 tail. To answer whether the RGT peptide binding to Src is able to alter the enzymatic activity of c-Src, we examined the Src-Csk association, the phosphorylation status of Y416 and Y527 of c-Src and the c-Src kinase catalytic activity. Results showed that myr-AC∼CRGT did not dissociate Csk from c-Src in resting platelets and the phosphorylation level of Y416 and Y527 of c-Src remained unaltered. Consistent data were also obtained from in vitro analysis of the c-Src kinase catalytic activity in the presence of CRGT peptide. These results suggest that myr-AC∼CRGT peptide per se does not fully activate c-Src. Myr-AC∼CRGT was also found to inhibit integrin αIIbβ3 outside-in signaling in human platelets. To examine the effect of the myr-AC∼CRGT on platelet adhesion and aggregation under flow conditions, we measured the platelet thrombus formation under different shear rates. Myr-AC∼CRGT did not affect the platelet adhesion at a wall shear rate of 125 s-1. The inability of myr-AC∼CRGT to affect platelet adhesion and aggregation remained at 500 s-1 shear rates. At 1,500 s-1, or 5,000 s-1 rates, myr-AC∼CRGT partially inhibited platelet adhesion and aggregation. These observations indicate that the Src-regulated outside-in signaling plays a pivotal role in the stable thrombus formation and the thrombus growth under flow conditions. The present study reveals novel insights into the molecular mechanisms by which c-Src regulates integrin αIIbβ3 signaling, particularly the phorsphorylation of the β3 cytoplasmic tyrosines, and provides first evidence in human platelets that the RGT peptide or derivatives regulate thrombus formation through dissociating the Src-β3 interaction. The data of this work allow us to anticipate that intracellular delivery of the RGT peptide or its analogues may have potential in the development of a new antithrombotic strategy where only the Src-β3 interaction is specifically interrupted so as to provide an effective inhibition on thrombosis together with a decent hemostasis. Disclosures: No relevant conflicts of interest to declare.


2001 ◽  
Vol 193 (4) ◽  
pp. 417-426 ◽  
Author(s):  
Tsuneyasu Kaisho ◽  
Kiyoshi Takeda ◽  
Tohru Tsujimura ◽  
Taro Kawai ◽  
Fumiko Nomura ◽  
...  

IκB kinase (IKK) α and β phosphorylate IκB proteins and activate the transcription factor, nuclear factor (NF)-κB. Although both are highly homologous kinases, gene targeting experiments revealed their differential roles in vivo. IKKα is involved in skin and limb morphogenesis, whereas IKKβ is essential for cytokine signaling. To elucidate in vivo roles of IKKα in hematopoietic cells, we have generated bone marrow chimeras by transferring control and IKKα-deficient fetal liver cells. The mature B cell population was decreased in IKKα−/− chimeras. IKKα−/− chimeras also exhibited a decrease of serum immunoglobulin basal level and impaired antigen-specific immune responses. Histologically, they also manifested marked disruption of germinal center formation and splenic microarchitectures that depend on mature B cells. IKKα−/− B cells not only showed impairment of survival and mitogenic responses in vitro, accompanied by decreased, although inducible, NF-κB activity, but also increased turnover rate in vivo. In addition, transgene expression of bcl-2 could only partially rescue impaired B cell development in IKKα−/− chimeras. Taken together, these results demonstrate that IKKα is critically involved in the prevention of cell death and functional development of mature B cells.


2016 ◽  
Vol 115 (01) ◽  
pp. 99-108 ◽  
Author(s):  
Kousi Alzoubi ◽  
Madhumita Chatterjee ◽  
Britta Walker ◽  
Patrick Münzer ◽  
Dong Luo ◽  
...  

SummaryCD44 is required for signalling of macrophage migration inhibitory factor (MIF), an anti-apoptotic pro-inflammatory cytokine. MIF is expressed and released from blood platelets, key players in the orchestration of occlusive vascular disease. Nothing is known about a role of CD44 in the regulation of platelet function. The present study thus explored whether CD44 modifies degranulation (P-selectin exposure), integrin activation, caspase activity, phosphatidylserine exposure on the platelet surface, platelet volume, Orai1 protein abundance and cytosolic Ca2+-activity ([Ca2+]i). Platelets from mice lacking CD44 (cd44-/- ) were compared to platelets from corresponding wild-type mice (cd44+/+ ). In resting platelets, P-selectin abundance, αllbβ3 inte-grin activation, caspase-3 activity and phosphatidylserine exposure were negligible in both genotypes and Orai1 protein abundance, [Ca2+]i, and volume were similar in cd44-/- and cd44+/+ platelets. Platelet degranulation and αllbβ3 integrin activation were significantly increased by thrombin (0.02 U/ml), collagen related peptide (CRP, 2 µg/ml and Ca2+-store depletion with thapsigargin (1 µM), effects more pronounced in cd44-/- than in cd44+/+ platelets. Thrombin (0.02 U/ml) increased platelet [Ca2+]i, caspase-3 activity, phosphatidylserine exposure and Orai1 surface abundance, effects again significantly stronger in cd44-/- than in cd44+/+ platelets. Thrombin further decreased forward scatter in cd44-/- and cd44+/+ platelets, an effect which tended to be again more pronounced in cd44-/- than in cd44+/+ platelets. Platelet adhesion and in vitro thrombus formation under high arterial shear rates (1,700 s-1) were significantly augmented in cd44-/- mice. In conclusion, genetic deficiency of CD44 augments activation, apoptosis and prothrombotic potential of platelets.


1995 ◽  
Vol 73 (02) ◽  
pp. 318-323 ◽  
Author(s):  
K Azzam ◽  
L I Garfinkel ◽  
C Bal dit Sollier ◽  
M Cisse Thiam ◽  
L Drouet

SummaryTo assess the antithrombotic effectiveness of blocking the platelet glycoprotein (GP) Ib/IX receptor for von Willebrand factor (vWF), the antiaggregating and antithrombotic effects were studied in guinea pigs using a recombinant fragment of vWF, Leu 504-Lys 728 with a single intrachain disulfide bond linking residues Cys 509-Cys 695. The inhibitory effect of this peptide, named VCL, was tested in vitro on ristocetin- and botrocetin-induced platelet aggregation and compared to the ADP-induced platelet aggregation. In vivo, the antithrombotic effect of VCL was tested in a model of laser-injured mesentery small arteries and correlated to the ex vivo ristocetin-induced platelet aggregation. In this model of laser-induced thrombus formation, five mesenteric arteries were studied in each animal, and the number of recurrent thrombi during 15 min, the time to visualization and time to formation of first thrombus were recorded.In vitro, VCL totally abolished ristocetin- and botrocetin-induced platelet aggregation, but had no effect on ADP-induced platelet aggregation. Ex vivo, VCL (0.5 to 2 mg/kg) administered as a bolus i. v. injection inhibits ristocetin-induced platelet aggregation with a duration of action exceeding 1 h. The maximum inhibition was observed 5 min after injection of VCL and was dose related. The same doses of VCL had no significant effect on platelet count and bleeding time. In vivo, VCL (0.5 to 2 mg/kg) had no effect on the appearance of the thrombi formed but produced dose-dependent inhibition of the mean number of recurrent thrombi (the maximal effect was obtained at 5 min following i. v. injection of the highest dose: 0.8 ± 0.2 thrombi versus 4 ± 0.4 thrombi in controls). The three doses of VCL increased the time in which the first thrombus in a concentration-dependent manner was formed. However, the time to visualize the first thrombus was only prolonged in the higher dose-treated group.These in-vivo studies confirm that VCL induces immediate, potent, and transient antithrombotic effects. Most importantly, this inhibition was achieved without inducing thrombocytopenia nor prolongation of the bleeding time.


2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Ahmed Hachem ◽  
Daniel Yacoub ◽  
Younes Zaid ◽  
Walid Mourad ◽  
Yahye Merhi

Introduction and hypothesis: CD40 ligand (CD40L) is a thrombo-inflammatory molecule that predicts cardiovascular events. Platelets constitute the major source of soluble CD40L (sCD40L), which has been shown to influence platelet activation. We have previously shown that upon ligation, CD40 potentiates platelet activation and aggregation via p38 mitogen activated protein kinase (MAPK) and Rac1 signaling. In B lymphocytes, CD40 induces activation and nuclear translocation of nuclear factor kappa B (NF-κB), which is dependent on the phosphorylation and dissociation of the inhibitor of kappa B α (IκBα). Given that platelets contain NF-κB, we hypothesized that it may be involved in platelet CD40 signaling. Methods and results: In human platelets, sCD40L induced association of tumor necrosis factor receptor associated factor 2 to CD40, and a time-dependant phosphorylation of IκBα, which is indicative of NF-κB activation. Activation of NF-κB in platelets treated with sCD40L was abolished by CD40L blockade. Pretreatment of platelets with the IκBα inhibitor, BAY 11-7082, reversed IκBα phosphorylation induced by sCD40L, without affecting p38 MAPK activation. On the other hand, pretreatment of platelets with the p38 MAPK phosphorylation inhibitor, SB203580, had no effect on IκBα phosphorylation, indicating a divergence in the signaling pathway originating from CD40 upon its ligation. Finally, inhibition of IκBα phosphorylation by either BAY 11-7082 or the IκB kinase inhibitor VII reversed sCD40L induced platelet activation, as measured by P-selectin expression, and the potentiation of platelet aggregation induced by a priming dose of collagen. Conclusion: This study demonstrates the implication of NF-κB in platelet signaling downstream of CD40, where it plays a role in platelet activation and aggregation upon sCD40L stimulation.


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