TRAF3 Negatively Regulates Platelet Activation and Thrombosis

CD40 ligand (CD40L), a member of the tumor necrosis factor (TNF) superfamily, binds to CD40, leading to many effects depending on target cell type. Platelets express CD40L and are a major source of soluble CD40L. CD40L has been shown to potentiate platelet activation and thrombus formation, involving both CD40-dependent and -independent mechanisms. A family of proteins called TNF receptor associated factors (TRAFs) plays key roles in mediating CD40L-CD40 signaling. Platelets express several TRAFs. It has been shown that TRAF2 plays a role in CD40L-mediated platelet activation. Here we show that platelet also express TRAF3, which plays a negative role in regulating platelet activation. Thrombin- or collagen-induced platelet aggregation and secretion are increased in TRAF3 knockout mice. The expression levels of collagen receptor GPVI and integrin αIIbβ3 in platelets were not affected by deletion of TRAF3, suggesting that increased platelet activation in the TRAF3 knockout mice was not due to increased expression platelet receptors. Time to formation of thrombi in a FeCl3-induced thrombosis model was significantly shortened in the TRAF3 knockout mice. However, mouse tail-bleeding times were not affected by deletion of TRAF3. Thus, TRAF3 plays a negative role in platelet activation and in thrombus formation in vivo

The P2Y(12) antagonists, 2MeSAMP and cangrelor, inhibit platelet activation through P2Y(12)/G(i)-dependent mechanism

BACKGROUND: ADP is an important physiological agonist that induces integrin activation and platelet aggregation through its receptors P2Y(1) (Gα(q)-coupled) and P2Y(12) (Gα(i)-coupled). P2Y(12) plays a critical role in platelet activation and thrombosis. Adenosine-based P2Y(12) antagonists, 2-methylthioadenosine 5\u27-monophosphate triethylammonium salt hydrate (2MeSAMP) and Cangrelor (AR-C69931MX) have been widely used to demonstrate the role of P2Y(12) in platelet function. Cangrelor is being evaluated in clinical trials of thrombotic diseases. However, a recent study reported that both 2MeSAMP and Cangrelor raise intra-platelet cAMP levels and inhibit platelet aggregation through a P2Y(12)-independent mechanism. METHODOLOGY/PRINCIPAL FINDINGS: The present work, using P2Y(12) deficient mice, sought to clarify previous conflicting reports and to elucidate the mechanisms by which 2MeSAMP and Cangrelor inhibit platelet activation and thrombosis. 2MeSAMP and Cangrelor inhibited aggregation and ATP release of wild-type but not P2Y(12) deficient platelets. 2MeSAMP and Cangrelor neither raised intracellular cAMP concentrations nor induced phosphorylation of vasodilator-stimulated phosphoprotein (VASP) in washed human or mouse platelets. Furthermore, unlike the activators (PGI(2) and forskolin) of the cAMP pathway, 2MeSAMP and Cangrelor failed to inhibit Ca(2+) mobilization, Akt phosphorylation, and Rap1b activation in P2Y(12) deficient platelets. Importantly, while injection of Cangrelor inhibited thrombus formation in a FeCl(3)-induced thrombosis model in wild-type mice, it failed to affect thrombus formation in P2Y(12) deficient mice. CONCLUSIONS: These data together demonstrate that 2MeSAMP and Cangrelor inhibit platelet function through the P2Y(12)-dependent mechanism both in vitro and in vivo

The Src Family Kinases and Protein Kinase C Synergize to Mediate G q -dependent Platelet Activation

The Src family kinases (SFKs) play essential roles in collagen- and von Willebrand factor (VWF)-mediated platelet activation. However, the roles of SFKs in G protein-coupled receptor-mediated platelet activation and the molecular mechanisms whereby SFKs are activated by G protein-coupled receptor stimulation are not fully understood. Here we show that the thrombin receptor protease-activated receptor 4 agonist peptide AYPGKF elicited SFK phosphorylation in P2Y12 deficient platelets but stimulated minimal SFK phosphorylation in platelets lacking Gq. We have previously shown that thrombin-induced SFK phosphorylation was inhibited by the calcium chelator 5,5′-dimethyl-bis-(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (dimethyl-BAPTA). The calcium ionophore A23187 induced SFK phosphorylation in both wild-type and Gq deficient platelets. Together, these results indicate that SFK phosphorylation in response to thrombin receptor stimulation is downstream from Gq/Ca2+ signaling. Moreover, {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187-induced thromboxane A2 synthesis, platelet aggregation, and secretion were inhibited by preincubation of platelets with a selective SFK inhibitor, PP2. AYPGKF-induced thromboxane A2 production in wild-type and P2Y12 deficient platelets was abolished by PP2, and AYPGKF-mediated P-selectin expression, integrin αIIbβ3 activation, and aggregation of P2Y12 deficient platelets were partially inhibited by the PKC inhibitor Ro-31-8220, PP2, dimethyl-BAPTA, or LY294002, but were abolished by Ro-31-8220 plus PP2, dimethyl-BAPTA, or LY294002. These data indicate that Ca2+/SFKs/PI3K and PKC represent two alternative signaling pathways mediating Gq-dependent platelet activation

Autophagy Is Induced Upon Platelet Activation and Is Essential for Hemostasis and Thrombosis

Autophagy is important for maintaining cellular homeostasis, and thus its deficiency is implicated in a broad spectrum of human diseases. Its role in platelet function has only recently been examined. Our biochemical and imaging studies demonstrate that the core autophagy machinery exists in platelets, and that autophagy is constitutively active in resting platelets. Moreover, autophagy is induced upon platelet activation, as indicated by agonist-induced loss of the autophagy marker LC3II. Additional experiments, using inhibitors of platelet activation, proteases, and lysosomal acidification, as well as platelets from knockout mouse strains, show that agonist-induced LC3II loss is a consequence of platelet signaling cascades and requires proteases, acidic compartments, and membrane fusion. To assess the physiological role of platelet autophagy, we generated a mouse strain with a megakaryocyte- and platelet-specific deletion of Atg7, an enzyme required for LC3II production. Ex vivo analysis of platelets from these mice shows modest defects in aggregation and granule cargo packaging. Although these mice have normal platelet numbers and size distributions, they exhibit a robust bleeding diathesis in the tail-bleeding assay and a prolonged occlusion time in the FeCl3-induced carotid injury model. Our results demonstrate that autophagy occurs in platelets and is important for hemostasis and thrombosis

Planck Galactic Cold Clumps at High Galactic Latitude-a Study with CO Lines

Gas at high Galactic latitude is a relatively little noticed component of the interstellar medium. In an effort to address this, 41 Planck Galactic Cold Clumps at high Galactic latitude (HGal; divide b divide > 25 degrees) were observed in (CO)-C-12, (CO)-C-13, and (CO)-O-18 J = 1-0 lines, using the Purple Mountain Observatory 13.7 m telescope. (CO)-C-12 (1-0) and (CO)-C-13 (1-0) emission was detected in all clumps, while (CO)-O-18 (1-0) emission was only seen in 16 clumps. The highest and average latitudes are 71.degrees 4 and 37.degrees 8, respectively. Fifty-one velocity components were obtained, and then each was identified as a single clump. Thirty-three clumps were further mapped at 1 ' resolution, and 54 dense cores were extracted. Among dense cores, the average excitation temperature T (ex) of (CO)-C-12 is 10.3 K. The average line widths of thermal and nonthermal velocity dispersions are 0.19 and 0.46 km s(-1), respectively, suggesting that these cores are dominated by turbulence. Distances of the HGal clumps given by Gaia dust reddening are about 120-360 pc. The ratio of X (13)/X (18) is significantly higher than that in the solar neighborhood, implying that HGal gas has a different star formation history compared to the gas in the Galactic disk. HGal cores with sizes from 0.01 to 0.1 pc show no notable Larson's relation, and the turbulence remains supersonic down to a scale of slightly below 0.1 pc. None of the HGal cores that bear masses from 0.01 to 1 M (circle dot) are gravitationally bound, and all appear to be confined by outer pressure.Peer reviewe

Wind-Solar-Biogas Renewable Energy Distributed Power system

2 Halama

Numerical investigation of the impact of thermoelectric effect on electron beam welding of dissimilar materials

Electron beam welding of GH4169 and Ni is required in the manufacture of the regenerative cooling system of the liquid rocket motor. The thermoelectric effect is observed during the welding of dissimilar metals; however, there has been a lack of investigation into the influence of this effect on electron beam welding joint formation and its dependence on test plate thickness. The thermoelectric effect of electron beam welding between GH4169 and Ni with varying thicknesses, as well as the influence of induced magnetic fields on electron beam trajectories, are investigated through the establishment of a numerical model incorporating thermal-electric-magnetic coupling.The results show that when the test plate increases from 2.5 mm to 10 mm the peak current density increases from 5.1 × 106 A/m2 to 7.6 × 106 A/m2, and the maximum magnetic flux density increases from 1.49× 10−2 T to 1.77 × 10−2 T. The increase in magnetic flux density results in a greater displacement of the electron beam spot away from the interface between the two materials, thereby causing incomplete fusion defects in the joints. This study elucidates the fundamental physical principles underlying the occurrence of incomplete fusion defects in electron beam welding joints, thereby furnishing essential theoretical underpinnings for enhancing the quality of dissimilar metal electron beam weld joints

Tunable backbone-degradable robust tissue adhesives via in situ radical ring-opening polymerization

Abstract Adhesives with both robust adhesion and tunable degradability are clinically and ecologically vital, but their fabrication remains a formidable challenge. Here we propose an in situ radical ring-opening polymerization (rROP) strategy to design a backbone-degradable robust adhesive (BDRA) in physiological environment. The hydrophobic cyclic ketene acetal and hydrophilic acrylate monomer mixture of the BDRA precursor allows it to effectively wet and penetrate substrates, subsequently forming a deep covalently interpenetrating network with a degradable backbone via redox-initiated in situ rROP. The resulting BDRAs show good adhesion strength on diverse materials and tissues (e.g., wet bone >16 MPa, and porcine skin >150 kPa), higher than that of commercial cyanoacrylate superglue (~4 MPa and 56 kPa). Moreover, the BDRAs have enhanced tunable degradability, mechanical modulus (100 kPa-10 GPa) and setting time (seconds-hours), and have good biocompatibility in vitro and in vivo. This family of BDRAs expands the scope of medical adhesive applications and offers an easy and environmentally friendly approach for engineering