Summary
Macrophages represent a multi‐functional cell type in innate immunity that contributes to bacterial clearance by recognition, phagocytosis and killing. In acute inflammation, infiltrating ...neutrophils release a wide array of preformed granule proteins which interfere functionally with their environment. Here, we present a novel role for neutrophil‐derived granule proteins in the anti‐microbial activity of macrophages. Neutrophil secretion obtained by antibody cross‐linking of the integrin subunit CD18 (X‐link secretion) or by treatment with N‐Formyl‐Met‐Leu‐Phe (fMLP secretion) induced a several‐fold increase in bacterial phagocytosis by monocytes and macrophages. This response was associated with a rapid activation of the monocytes and macrophages as depicted by an increase in cytosolic free Ca2+. Interestingly, fMLP secretion had a more pronounced effect on monocytes than the X‐link secretion, while the opposite was observed for macrophages. In addition, polymorphonuclear cells (PMN) secretion caused a strong enhancement of intracellular reactive oxygen species (ROS) formation compared to incubation with bacteria. Thus, secretion of neutrophil granule proteins activates macrophages to increase the phagocytosis of bacteria and to enhance intracellular ROS formation, indicating pronounced intracellular bacterial killing. Both mechanisms attribute novel microbicidal properties to PMN granule proteins, suggesting their potential use in anti‐microbial therapy.
Median bias reduction in cumulative link models Gioia, V.; Kenne Pagui, E. C.; Salvan, A.
Communications in statistics. Simulation and computation,
03/2023, Letnik:
52, Številka:
3
Journal Article
Recenzirano
Odprti dostop
This paper presents a novel estimation approach for cumulative link models, based on median bias reduction. The median bias reduced estimator is obtained as solution of an estimating equation based ...on an adjustment of the score. It allows to obtain higher-order median centering of maximum likelihood estimates without requiring their finiteness. The estimator is equivariant under componentwise monotone reparameterizations and the method is effective in preventing boundary estimates. Through simulation studies and an application, we compare the median bias reduced estimator with the two main competitors, the maximum likelihood and the mean bias reduced estimators. The method is seen to be highly successful in achieving median centering and shows remarkable properties under reparameterizations related to effect measure.
Blood coagulation is essential for hemostasis, however excessive coagulation can lead to thrombosis. Factor XII starts the intrinsic coagulation pathway and contact-induced factor XII activation ...provides the mechanistic basis for the diagnostic aPTT clotting assay. Despite its function for fibrin formation in test tubes, patients and animals lacking factor XII have a completely normal hemostasis. The lack of a bleeding tendency observed in factor XII deficiency states is in sharp contrast to deficiencies of other components of the coagulation cascade and factor XII has been considered to have no function for coagulation in vivo. Recently, experimental animal models showed that factor XII is activated by an inorganic polymer, polyphosphate, which is released from procoagulant platelets and that polyphosphate-driven factor XII activation has an essential role in pathologic thrombus formation. Cumulatively, the data suggest to target polyphosphate, factor XII, or its activated form factor XIIa for anticoagulation. As the factor XII pathway specifically contributes to thrombosis but not to hemostasis, interference with this pathway provides a unique opportunity for safe anticoagulation that is not associated with excess bleeding. The review summarizes current knowledge on factor XII functions, activators and inhibitors.
Umbilical cord blood (UCB) as a source of hematopoietic stem cells for transplantation is limited by the low number of cells and delayed engraftment. UCB cells are infused i.v. for transplantation, ...although only a proportion of the cells reach the BM. We investigated whether UCB could be administered safely using superselective intra-arterial (i.a.) injection. We injected human UCB (5 × 10(6)) into the aorta in rats, into the iliac artery in mice and into the femoral nutrient artery (FNA) in rabbits. We used angiography, immunohistochemistry, intravital microscopy and qPCR to assess safety end points and the distribution of injected cells. All animals showed normal behavior. No evidence of organ infarction was noted. UCB injected into the FNA of rabbits did not change the flow rates, measured by angiography. By qPCR, we found significantly higher fold-change values in the injected BM compared with i.v. injection (P=0.0087). Using intravital microscopy we visualized the mouse capillary bed during i.a. injection without cellular congestion. In summary, we show that i.a. infusion of UCB is safe and reaches an eightfold increase in engraftment in the BM compared with i.v. infusion. These studies lay the foundation for clinical trials.
ABSTRACTAcute lung injury (ALI) and respiratory distress can develop as a consequence of sepsis with pathogens such as group A Streptococcus (GAS). In the pathogenesis of sepsis‐associated ALI, ...endothelial barrier disruption brought on by phagocyte activation is considered a causative factor. Here, we find that sevuparin, a heparinoid with low anticoagulant activity, prevents neutrophil‐induced lung plasma leakage in a murine model of systemic inflammation evoked by heat‐killed GAS (hkGAS). Furthermore, using human neutrophils and endothelial cell monolayers, we demonstrate that sevuparin inhibits hkGAS‐induced endothelial barrier disruption by neutralizing the activity of neutrophil‐derived proteins. By mass spectrometry of neutrophil secretion, we identify proteins, including serprocidins, S100 proteins, and histone H4, that interact with sevuparin and that are responsible for the disruptive effect on endothelial integrity. Collectively, our results demonstrate the critical role of neutrophil‐derived proteins in vascular hyperpermeability caused by GAS and suggest sevuparin as a potential therapeutic in acute neutrophilic inflammation.—Rasmuson, J., Kenne, E., Wahlgren, M., Soehnlein, O., Lindbom, L. Heparinoid sevuparin inhibits Streptococcus‐induced vascular leak through neutralizing neutrophil‐derived proteins. FASEB J. 33, 10443–10452 (2019). www.fasebj.org
Brain edema as a result of secondary injury following traumatic brain injury (TBI) is a major clinical concern. Neutrophils are known to cause increased vascular permeability leading to edema ...formation in peripheral tissue, but their role in the pathology following TBI remains unclear.
In this study we used controlled cortical impact (CCI) as a model for TBI and investigated the role of neutrophils in the response to injury. The outcome of mice that were depleted of neutrophils using an anti-Gr-1 antibody was compared to that in mice with intact neutrophil count. The effect of neutrophil depletion on blood-brain barrier function was assessed by Evan's blue dye extravasation, and analysis of brain water content was used as a measurement of brain edema formation (24 and 48 hours after CCI). Lesion volume was measured 7 and 14 days after CCI. Immunohistochemistry was used to assess cell death, using a marker for cleaved caspase-3 at 24 hours after injury, and microglial/macrophage activation 7 days after CCI. Data were analyzed using Mann-Whitney test for non-parametric data.
Neutrophil depletion did not significantly affect Evan's blue extravasation at any time-point after CCI. However, neutrophil-depleted mice exhibited a decreased water content both at 24 and 48 hours after CCI indicating reduced edema formation. Furthermore, brain tissue loss was attenuated in neutropenic mice at 7 and 14 days after injury. Additionally, these mice had a significantly reduced number of activated microglia/macrophages 7 days after CCI, and of cleaved caspase-3 positive cells 24 h after injury.
Our results suggest that neutrophils are involved in the edema formation, but not the extravasation of large proteins, as well as contributing to cell death and tissue loss following TBI in mice.
Polyphosphate is an inorganic polymer that can potentiate several interactions in the blood coagulation system. Blood platelets contain polyphosphate, and the secretion of platelet-derived ...polyphosphate has been associated with increased thrombus formation and activation of coagulation factor XII. However, the small polymer size of secreted platelet polyphosphate limits its capacity to activate factor XII in vitro. Thus, the mechanism by which platelet polyphosphate contributes to thrombus formation remains unclear. Using live-cell imaging, confocal and electron microscopy, we show that activated platelets retain polyphosphate on their cell surface. The apparent polymer size of membrane-associated polyphosphate largely exceeds that of secreted polyphosphate. Ultracentrifugation fractionation experiments revealed that membrane-associated platelet polyphosphate is condensed into insoluble spherical nanoparticles with divalent metal ions. In contrast to soluble polyphosphate, membrane-associated polyphosphate nanoparticles potently activate factor XII. Our findings identify membrane-associated polyphosphate in a nanoparticle state on the surface of activated platelets. We propose that these polyphosphate nanoparticles mechanistically link the procoagulant activity of platelets with the activation of coagulation factor XII.
•Activated platelets expose insoluble membrane-associated polyphosphate nanoparticles that are complexed with divalent metal ions.•Platelet polyphosphate nanoparticles, but not soluble polyphosphate polymers, activate the contact system.
We establish conditions for full efficiency of the maximum composite likelihood estimator, related to proportionality of the full and composite score functions. A major application is in exponential ...family models. An illustrative example is considered.
Background Anaphylaxis is an acute, potentially lethal, multisystem syndrome resulting from the sudden release of mast cell–derived mediators into the circulation. Objectives and Methods We report ...here that a plasma protease cascade, the factor XII–driven contact system, critically contributes to the pathogenesis of anaphylaxis in both murine models and human subjects. Results Deficiency in or pharmacologic inhibition of factor XII, plasma kallikrein, high-molecular-weight kininogen, or the bradykinin B2 receptor, but not the B1 receptor, largely attenuated allergen/IgE-mediated mast cell hyperresponsiveness in mice. Reconstitutions of factor XII null mice with human factor XII restored susceptibility for allergen/IgE-mediated hypotension. Activated mast cells systemically released heparin, which provided a negatively charged surface for factor XII autoactivation. Activated factor XII generates plasma kallikrein, which proteolyzes kininogen, leading to the liberation of bradykinin. We evaluated the contact system in patients with anaphylaxis. In all 10 plasma samples immunoblotting revealed activation of factor XII, plasma kallikrein, and kininogen during the acute phase of anaphylaxis but not at basal conditions or in healthy control subjects. The severity of anaphylaxis was associated with mast cell degranulation, increased plasma heparin levels, the intensity of contact system activation, and bradykinin formation. Conclusions In summary, the data collectively show a role of the contact system in patients with anaphylaxis and support the hypothesis that targeting bradykinin generation and signaling provides a novel and alternative treatment strategy for anaphylactic attacks.
Polyphosphate is an inorganic procoagulant polymer. Here we develop specific inhibitors of polyphosphate and show that this strategy confers thromboprotection in a factor XII-dependent manner. ...Recombinant Escherichia coli exopolyphosphatase (PPX) specifically degrades polyphosphate, while a PPX variant lacking domains 1 and 2 (PPX_Δ12) binds to the polymer without degrading it. Both PPX and PPX_Δ12 interfere with polyphosphate- but not tissue factor- or nucleic acid-driven thrombin formation. Targeting polyphosphate abolishes procoagulant platelet activity in a factor XII-dependent manner, reduces fibrin accumulation and impedes thrombus formation in blood under flow. PPX and PPX_Δ12 infusions in wild-type mice interfere with arterial thrombosis and protect animals from activated platelet-induced venous thromboembolism without increasing bleeding from injury sites. In contrast, targeting polyphosphate does not provide additional protection from thrombosis in factor XII-deficient animals. Our data provide a proof-of-concept approach for combating thrombotic diseases without increased bleeding risk, indicating that polyphosphate drives thrombosis via factor XII.
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