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Glucose depletion of erythrocytes triggers suicidal erythrocyte death or eryptosis, which leads to cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptotic erythrocytes adhere to endothelial cells by a mechanism involving phosphatidylserine at the erythrocyte surface and CXCL16 as well as CD36 at the endothelial cell membrane. Nothing has hitherto been known about an interaction between eryptotic erythrocytes and platelets, the decisive cells in primary hemostasis and major players in thrombotic vascular occlusion. The present study thus explored whether and how glucose-depleted erythrocytes adhere to platelets. To this end, adhesion of phosphatidylserine-exposing erythrocytes to platelets under flow conditions was examined in a flow chamber model at arterial shear rates. Platelets were immobilized on collagen and further stimulated with adenosine diphosphate (ADP, 10 µM) or thrombin (0.1 U/ml). As a result, a 48-h glucose depletion triggered phosphatidylserine translocation to the erythrocyte surface and augmented the adhesion of erythrocytes to immobilized platelets, an effect significantly increased upon platelet stimulation. Adherence of erythrocytes to platelets was blunted by coating of erythrocytic phosphatidylserine with annexin V or by neutralization of platelet phosphatidylserine receptors CXCL16 and CD36 with respective antibodies. In conclusion, glucose-depleted erythrocytes adhere to platelets. The adhesive properties of platelets are augmented by platelet activation. Erythrocyte adhesion to immobilized platelets requires phosphatidylserine at the erythrocyte surface and CXCL16 as well as CD36 expression on platelets. Thus platelet-mediated erythrocyte adhesion may foster thromboocclusive complications in diseases with stimulated phosphatidylserine exposure of erythrocytes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Protection motivation messages more effective than in-use anti-speeding messages. [•] Severity and vulnerability most effective for developing anti-speeding messages. [•] Males reported lower intention than females to drive within speed limits. [•] Third-person effect for males – messages seen as more effective for others. [•] Reverse effect for females – messages seen as more effective for themselves. [ABSTRACT FROM AUTHOR]

Background/Aims: Platelets are critically important for primary haemostasis and the major players in thrombotic vascular occlusion. Platelets are activated by agonists, such as thrombin and collagen-related peptide as well as second-wave mediators including thromboxane A2 via different intracellular signaling pathways resulting in degranulation, aggregation and thrombus formation. Platelet activation is paralleled by phosphorylation and activation of p38 MAPK. The limited specificity of hitherto known p38 MAPK inhibitors precluded safe conclusions on the precise role of p38 MAPK in the regulation of platelet function. The present study examined the impact of Skepinone-L, a novel and highly selective inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), on platelet activation and thrombus formation. Methods: Experiments were performed in freshly isolated human platelets. Protein phosphorylation was quantified by Western blotting, thromboxane B2 synthesis by enzyme immunoassay, ATP release by ChronoLume luciferin assay, cytosolic Ca2+ concentration by Fura-2 fluorescence-measurements, platelet aggregation by a light transmissions measurement and in vitro thrombus formation by a flow chamber. Results: Skepinone-L (1 μM) virtually abrogated the phosphorylation of platelet p38 MAPK substrate Hsp27 following stimulation with CRP (1 μg/ml), thrombin (5 mU/ml) or thromboxane A2 analogue U-46619 (1 μM). Furthermore, Skepinone-L significantly blunted activation-dependent platelet secretion and aggregation following threshold concentrations of CRP, thrombin and thromboxane A2 analogue U-46619. Skepinone-L did not impair platelet Ca2+ signaling but prevented agonist-induced thromboxane A2 synthesis through abrogation of p38 MAPK-dependent phosphorylation of platelet cytosolic phospholipase A2 (cPLA2). Skepinone-L further markedly blunted thrombus formation under low (500-s) and high (1700-s) arterial shear rates. Conclusions: The present study discloses a powerful inhibiting effect of p38 MAPK-blocker Skepinone-L on platelet activation and thrombus formation. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: Regulatory T cell (Treg) is required for the maintenance of tolerance to various tissue antigens and to protect the host from autoimmune disorders. However, Treg may, indirectly, support cancer progression and bacterial infections. Therefore, a balance of Treg function is pivotal for adequate immune responses. Acid sphingomyelinase (ASM) is a rate limiting enzyme involved in the production of ceramide by breaking down sphingomyelin. Previous studies in T-cells have suggested that ASM is involved in CD28 signalling, T lymphocyte granule secretion, degranulation, and vesicle shedding similar to the formation of phosphatidylserine-exposing microparticles from glial cells. However, whether ASM affects the development of Treg has not yet been described. Methods: Splenocytes, isolated Naive T lymphocytes and cultured T cells were characterized for various immune T cell markers by flow cytometery. Cell proliferation was measured by Carboxyfluorescein succinimidyl ester (CFSE) dye, cell cycle analysis by Propidium Iodide (PI), mRNA transcripts by q-RT PCR and protein expression by Western Blotting respectively. Results: ASM deficient mice have higher number of Treg compared with littermate control mice. In vitro induction of ASM deficient T cells in the presence of TGF-β and IL-2 lead to a significantly higher number of Foxp3+ induced Treg (iTreg) compared with control T-cells. Further, ASM deficient iTreg has less AKT (serine 473) phosphorylation and Rictor levels compared with control iTreg. Ceramide C6 led to significant reduction of iTreg in both ASM deficient and WT mice. The reduction in iTreg leads to induction of IL-1β, IL-6 and IL-17 but not IFN-γ mRNA levels. Conclusion: ASM is a negative regulator of natural and iTreg. [ABSTRACT FROM AUTHOR]

Sphingosine 1-phosphate (S1P) is a powerful regulator of platelet formation. Enzymes generating S1P include sphingosine kinase 1. The present study thus explored the role of sphingosine kinase 1 in platelet formation and function. Activationdependent platelet integrin αIIbβ3 activation and secretion of platelets lacking functional sphingosine kinase 1 (sphkl-/- and of wild-type platelets (sphkl+/+) were determined utilizing flow cytometry and chronolume luciferin assay. Cytosolic Ca2+ activity ([Ca2+]i) and aggregation were measured using fura-2 fluorescence and aggregometry, respectively. In vitro platelet adhesion and thrombus formation were evaluated using a flow chamber with shear rates of 1,700 s-1. Activation-dependent increase of [Ca2+]i, degranulation (release of alpha and dense granules), integrin αIIbβ3 activation, and aggregation were all significantly increased in sphkl platelets compared with sphkl+/+platelets. Moreover, while platelet adhesion and thrombus formation under arterial shear rates were significantly augmented in Sphk1-deficient platelets, bleeding time and blood count were unaffected in sphkl-/- mice. In conclusion, sphingosine kinase 1 is a powerful negative regulator of platelet function counteracting degranulation, aggregation, and thrombus formation. [ABSTRACT FROM AUTHOR]

Background Cardiac inflammation has been suggested to play a critical role in the pathogenesis of inflammatory cardiomyopathy as well as in progressive heart failure (HF). CXC motif ligand 16 (CXCL16) is a recently discovered chemokine produced by several inflammatory cells and representing an important pathogenic mediator in the development of HF. The present study evaluates the diagnostic and prognostic relevance of CXCL16 expression in endomyocardial biopsies of consecutive patients with congestive HF. Methods and results 174 patients (age 54.4 ± 14.6 years) with congestive HF undergoing endomyocardial biopsy for diagnostic reasons were prospectively enrolled. Biopsies were analyzed using established histopathological and immunohistological criteria together with CXCL16 staining. CXCL16 was significantly enhanced in patients with inflammatory cardiomyopathy (78/127, 61.4%) as compared to patients with non-inflammatory cardiomyopathy (17/47, 36.2%, p = 0.003). During a mean follow-up of 27.5 months, 20 patients (11.5%) reached the primary endpoint (death of all causes). Of all clinical (age, gender, NYHA functional class, systolic pulmonary artery pressure, left ventricular ejection fraction), laboratory (brain natriuretic peptide) and immunohistological (CXCL16) parameters tested, CXCL16 was the only independent predictor of death (hazard ratio 5.4; 95% confidence interval 1.2 to 24.0; p = 0.027). Subgroup analysis revealed CXCL16 as a predictor of death in both patients with inflammatory and with non-inflammatory cardiomyopathy. Conclusion According to the present observations CXCL16 is enhanced in inflammatory cardiomyopathy and turned out as an independent predictor of death in patients with HF undergoing endomyocardial biopsy. [ABSTRACT FROM AUTHOR]

Thrombosis and inflammation are intricately linked in several major clinical disorders, including disseminated intravascular coagulation and acute ischemic events. The damage-associated molecular pattern molecule high-mobility group box 1 (HMGB1) is upregulated by activated platelets in multiple inflammatory diseases; however, the contribution of platelet-derived HMGB1 in thrombosis remains unexplored. Here, we generated transgenic mice with platelet-specific ablation of HMGB1 and determined that platelet-derived HMGB1 is a critical mediator of thrombosis. Mice lacking HMGB1 in platelets exhibited increased bleeding times as well as reduced thrombus formation, platelet aggregation, inflammation, and organ damage during experimental trauma/hemorrhagic shock. Platelets were the major source of HMGB1 within thrombi. In trauma patients, HMGB1 expression on the surface of circulating platelets was markedly upregulated. Moreover, evaluation of isolated platelets revealed that HMGB1 is critical for regulating platelet activation, granule secretion, adhesion, and spreading. These effects were mediated via TLR4- and MyD88-dependent recruitment of platelet guanylyl cyclase (GC) toward the plasma membrane, followed by MyD88/GC complex formation and activation of the cGMP-dependent protein kinase I (cGKI). Thus, we establish platelet-derived HMGB1 as an important mediator of thrombosis and identify a HMGB1-driven link between MyD88 and GC/cGKI in platelets. Additionally, these findings suggest a potential therapeutic target for patients sustaining trauma and other inflammatory disorders associated with abnormal coagulation. [ABSTRACT FROM AUTHOR]

Platelets are activated by increased cytsolic Ca2+ concentration ([Ca2+]i) following store-operated calcium entry (SOCE) accomplished by calcium release-activated calcium (CRAC) channel moiety Orail and its regulator STIM1. In other cells, Ca2+ transport is regulated by 1,25(OH) 2 vitamin D3 [1,25(OH) 2D3] 1,25(OH) 2D3 formation is inhibited by klotho and excessive in klotho-deficient mice (kl/kl). The prese study explored the effect of klotho deficiency o platelet Ca2+ signaling and activation. Platelets an megakaryocytes isolated from WT and kl/kl-mice we analyzed by RT-PCR, Western blotting, confocal microscopy, Fura-2-fluorescence, patch clamp, flow cytometry, aggregometry, and flow chamber. STIM1/Orail transcript and protein levels, SOCE, agonist-induce [Ca2+]i increase, activation-dependent degranulation, integrin αIIbβ3 activation and aggregation, and thrombus formation were significantly blunted in kl/kl platelets (by 27-90%). STIM1/Orail transcript and protein levels, as well as CRAC currents, were significantly reduced in kl/kl megakaryocytes (by 38-73%) 1,25(OH)2D3-treated WT megakaryocytes. Nuclear NF-ΚB subunit p50/p65 abundance was significant reduced in kl/kl-megakaryocytes (by 51-76%). Transfection with p50/p65 significantly increased STIM1 Orall transcript and protein levels in megakaryocytic MEG-01 cells (by 46-97%). Low-vitamin D diet (LVD of kl/kl mice normalized plasma 1,25(OH)2D3 concentration and function of platelets and megakaryocyte. Klotho deficiency inhibits platelet Ca2+ signaling and activation, an effect at least partially due to 1,25(OH)2D3-dependent down-regulation of NF-ΚB activity and STIM1/Orail expression in megakaryocytes. [ABSTRACT FROM AUTHOR]

Background/Aims: Renal tissue fibrosis contributes to the development of end-stage renal disease. Causes for renal tissue fibrosis include obstructive nephropathy. The development of renal fibrosis following unilateral ureteral obstruction (UUO) is blunted in gene-targeted mice lacking functional serum- and glucocorticoid-inducible kinase SGK1. Similar to Akt isoforms, SGK1 phosphorylates and thus inactivates glycogen synthase kinase GSK-3. The present study explored whether PKB/SGK-dependent phoshorylation of GSK-3α/β impacts on pro-fibrotic signaling following UUO. Methods: UUO was induced in mice carrying a PKB/SGK-resistant GSK-3α/β (gsk-3KI) and corresponding wild-type mice (gsk-3WT). Three days after the obstructive injury, expression of fibrosis markers in kidney tissues was analyzed by quantitative RT-PCR and western blotting. Results: GSK-3α and GSK-3β phosphorylation was absent in both, the non-obstructed and the obstructed kidney tissues from gsk-3KI mice but was increased by UUO in kidney tissues from gsk-3WT mice. Expression of α-smooth muscle actin, type I collagen and type III collagen in the non-obstructed kidney tissues was not significantly different between gsk-3KI mice and gsk-3WT mice but was significantly less increased in the obstructed kidney tissues from gsk-3KI mice than from gsk-3WT mice. After UUO treatment, renal β-catenin protein abundance and renal expression of the β-catenin sensitive genes: c-Myc, Dkk1, Twist and Lef1 were again significantly less increased in kidney tissues from gsk-3KI mice than from gsk-3WT mice. Conclusions: PKB/SGK-dependent phosphorylation of glycogen synthase kinase GSK-3 contributes to the pro-fibrotic signaling leading to renal tissue fibrosis in obstructive nephropathy. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Alzheimer’s disease (AD) is characterized by neurotoxic amyloid-ß plaque formation in brain parenchyma and cerebral blood vessels known as cerebral amyloid angiopathy (CAA). Besides CAA, AD is strongly related to vascular diseases such as stroke and atherosclerosis. Cerebrovascular dysfunction occurs in AD patients leading to alterations in blood flow that might play an important role in AD pathology with neuronal loss and memory deficits. Platelets are the major players in hemostasis and thrombosis, but are also involved in neuroinflammatory diseases like AD. For many years, platelets were accepted as peripheral model to study the pathophysiology of AD because platelets display the enzymatic activities to generate amyloid-ß (Aß) peptides. In addition, platelets are considered to be a biomarker for early diagnosis of AD. Effects of Aß peptides on platelets and the impact of platelets in the progression of AD remained, however, ill-defined. The present study explored the cellular mechanisms triggered by Aß in platelets. Treatment of platelets with Aß led to platelet activation and enhanced generation of reactive oxygen species (ROS) and membrane scrambling, suggesting enhanced platelet apoptosis. More important, platelets modulate soluble Aß into fibrillar structures that were absorbed by apoptotic but not vital platelets. This together with enhanced platelet adhesion under flow ex vivo and in vivo and platelet accumulation at amyloid deposits of cerebral vessels of AD transgenic mice suggested that platelets are major contributors of CAA inducing platelet thrombus formation at vascular amyloid plaques leading to vessel occlusion critical for cerebrovascular events like stroke. [ABSTRACT FROM AUTHOR]

Background/Aims: The serum- and glucocorticoid-inducible kinase Sgk1 contributes to cardiac remodeling and development of heart failure, which is paralelled by Sgk1-dependent stimulation of the cardiac Na+/H+ exchanger Nhe1. Glucocorticoids are powerful stimulators of Sgk1 expression and influence cardiac remodeling. The present study thus explored whether the glucocorticoid receptor agonist dexamethasone influenced cardiac Sgk1 expression, as well as activity, expression and phosphorylation at Ser703 of the cardiac Na+/H+ exchanger Nhe1. Methods: Experiments were performed in HL-1 cardiomyocytes and gene targeted mice lacking functional Sgk1 (sgk1-/-) and respective wild type mice (sgk1+/+). Gene expression was determined by quantitative RT-PCR and Nhe1 phosphorylation was determined utilizing a specific antibody against a 14-3-3 binding motif at P-Ser703, which represents a putative phosphorylation site recognition motif for Sgk1 and is involved in Nhe1 activation. Cytosolic pH (pHi) was determined utilizing 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence and Nhe activity by the Na+-dependent realkalinization after an ammonium pulse. Results: Treatment of HL-1 cardiomyocytes with dexamethasone was followed by a significant increase in Sgk1 mRNA expression, parallelled by increased Na+/H+ exchanger activity. Furthermore, dexamethasone significantly increased Nhe1 and Spp1 mRNA expression. The effects of dexamethasone were blunted by cotreatment of HL-1 cardiomyocytes with the Sgk1 inhibitor EMD638683. Cotreatment with Nhe1 inhibitor cariporide similarly prevented dexamethasone-stimulated Spp1 mRNA expression. In sgk1+/+ mice, dexamethasone significantly increased cardiac Sgk1 mRNA levels. In sgk1+/+ mice, but not in sgk1-/- mice, dexamethasone significantly increased cardiac Nhe1 mRNA expression and Nhe1 phosphorylation at Ser703. Furthermore, cardiac Spp1, Ctgf, Nppa and Nppb mRNA levels were significantly increased in dexamethasone treated sgk1+/+ mice, effects significantly blunted in sgk1-/- mice. Conclusions: Sgk1 is critically involved in the phosphorylation and activation of the cardiac Na+/H+ exchanger Nhe1. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Chorea-acanthocytosis (ChAc), a lethal disease caused by defective chorein, is characterized by neurodegeneration and erythrocyte acanthocytosis. The functional significance of chorein in other cell types remained ill-defined. The present study revealed chorein expression in blood platelets. As compared to platelets from healthy volunteers, platelets from patients with ChAc displayed a 47% increased globular/filamentous actin ratio, indicating actin depolymerization. Moreover, phosphoinositide-3-kinase subunit p85 phosphorylation, p21 protein-activated kinase (PAK1) phosphorylation, as well as vesicle-associated membrane protein 8 (VAMP8) expression were significantly reduced in platelets from patients with ChAc (by 17, 22, and 39%, respectively) and in megakaryocytic (MEG-01) cells following chorein silencing (by 16, 54, and 11%, respectively). Activation-induced platelet secretion from dense granules (ATP release) and α granules (P-selectin exposure) were significantly less (by 55% after stimulation with 1 µg/ml CRP and by 33% after stimulation with 5 µM TRAP, respectively) in ChAc platelets than in control platelets. Furthermore, platelet aggregation following stimulation with different platelet agonists was significantly impaired. These observations reveal a completely novel function of chorein, i.e., regulation of secretion and aggregation of blood platelets. [ABSTRACT FROM AUTHOR]

Highlights: [•] In blood platelets, thrombin upregulates protein abundance of Ca2+ channel Orai1. [•] The effect is paralleled by transient formation of mRNA from pre-RNA. [•] The effect is blunted by inhibition of translation but not by inhibition of transcription. [•] The effect is blunted by pharmacological inhibition of phosphoinositide-3-kinase. [ABSTRACT FROM AUTHOR]

Background: The WNK-dependent STE20/SPS1-related proline/alanine-rich kinase (SPAK) regulates the renal thiazide sensitive NaCl cotransporter (NCC) and the renal furosemide sensitive Na+,K+,2Cl- cotransporter (NKCC2) and thus participates in the regulation of renal salt excretion, extracellular fluid volume and blood pressure. Inhibition of NCC leads to anticalciuria. Moreover, NCC is also expressed in osteoblasts where it is implicated in the regulation of bone mineralization. Osteoblasts further influence mineral metabolism by releasing the phosphaturic hormone FGF23. The present study explored, whether SPAK participates in the regulation of calcium-phosphate homeostasis. Methods: FGF23 serum levels and phosphate homeostasis were analyzed in gene targeted mice expressing SPAK resistant to WNK-dependent activation (spaktg/tg) and in mice expressing wild type SPAK (spakwt/wt). Results: Serum FGF23 level was significantly higher, urinary phosphate excretion significantly larger and serum phosphate concentration significantly lower in spaktg/tg mice than in spakwt/wt mice. Urinary calcium excretion was significantly decreased in spaktg/tg mice. Serum levels of calcitriol and PTH were not significantly different between the genotypes. Bone density was significantly increased in spaktg/tg mice compared to spakwt/wt mice. Treatment of spakwt/wt mice with HCT increased FGF23 serum levels, and led to phosphaturia and hypophosphatemia. Conclusions: SPAK is a strong regulator of FGF23 formation, bone mineralization and renal Ca2+ and phosphate excretion. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Activation of platelets by thrombin opens pore forming channel protein Orai1 with subsequent store operated Ca2+ entry (SOCE) and Ca2+ dependent platelet granule release, integrin αIIbβ3 activation, adhesion, aggregation and thrombus formation. Orai1 and thus SOCE as well as platelet activation are up-regulated by the serum- and glucocorticoid-inducible kinase-1 (SGK1), which transcriptionally regulates Orai1 expression in megakaryocytes and thus determines Orai1 protein abundance in mature, circulating platelets. As platelets are devoid of nuclei, they are unable to modify protein abundance by regulation of transcription. However, they contain mRNA and thus could express novel protein by stimulation of protein translation. Translation is sensitive to actin polymerization and phosphoinositide-3-kinase (PI3K). Translational regulation of SGK1 expression has never been described before. The present study thus explored whether thrombin regulates SGK1 expression in platelets. As a result, according to RT-PCR mRNA encoding SGK1 is present in circulating platelets and significantly decreased by activation of platelets with thrombin (1U/ml). The protein abundance of SGK1 is significantly enhanced by thrombin treatment, an effect significantly decreased by inhibition of translation with puromycin (100nM) but not by inhibition of transcription with actinomycin (4μg/ml). The increase of SGK1 protein abundance is blunted by inhibition of PI3K with wortmannin (100nM) or LY294002 (25μM), and by disruption of the cytoskeleton with cytochalasin B (1μM). In conclusion, activation of platelets with thrombin stimulates the translation of SGK1. [Copyright &y& Elsevier]