Dataset Information

Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis.

ABSTRACT: Sepsis is associated with thrombocytopenia and microvascular thrombosis. Studies have described platelets implication in this pathology but their kinetics of activation and behavior remain poorly known. We show in a mouse model of peritonitis, the appearance of platelet-rich thrombi in organ microvessels and organ damage. Complementary methods are necessary to characterize platelet activation during sepsis as circulating soluble markers and platelet-monocyte aggregates revealed early platelet activation, while surface activation markers were detected at later stage. A microfluidic based ex-vivo thrombosis assay demonstrated that platelets from septic mice have a prothrombotic behavior at shear rate encountered in microvessels. Interestingly, we found that even though phosphoinositide-3-kinase ?-deficient platelet mice formed less thrombi in liver microcirculation, peritoneal sepsis activates a platelet alternative pathway to compensate the otherwise mandatory role of this lipid-kinase to form stable thrombi at high shear rate. Platelets are rapidly activated during sepsis. Thrombocytopenia can be attributed in part to platelet-rich thrombi formation in capillaries and platelet-leukocytes interactions. Platelets from septic mice have a prothrombotic phenotype at a shear rate encountered in arterioles. Further studies are necessary to unravel molecular mechanisms leading to this prothrombotic state of platelets in order to guide the development of future treatments of polymicrobial sepsis.

SUBMITTER: Vardon Bounes F

PROVIDER: S-EPMC6131186 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis.

Vardon Bounes Fanny F Mémier Vincent V Marcaud Marina M Jacquemin Aemilia A Hamzeh-Cognasse Hind H Garcia Cédric C Series Jennifer J Sié Pierre P Minville Vincent V Gratacap Marie-Pierre MP Payrastre Bernard B

Scientific reports 20180910 1

Sepsis is associated with thrombocytopenia and microvascular thrombosis. Studies have described platelets implication in this pathology but their kinetics of activation and behavior remain poorly known. We show in a mouse model of peritonitis, the appearance of platelet-rich thrombi in organ microvessels and organ damage. Complementary methods are necessary to characterize platelet activation during sepsis as circulating soluble markers and platelet-monocyte aggregates revealed early platelet ac ...[more]

PMID: 30201980

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Project description:Sepsis is characterized by an intense systemic inflammatory response activating a cascade of proinflammatory events resulting in leukocyte dysregulation and host tissue damage. The lung is particularly susceptible to systemic inflammation, leading to acute lung injury. Key to inflammation-induced lung damage is the excessive migration of neutrophils across the vascular endothelium. The mechanisms which regulate neutrophil activation and migration in sepsis are not well defined but there is growing evidence that platelets are actively involved and play a key role in microvascular permeability and neutrophil-mediated organ damage. We previously identified PKC-delta (PKC?) as a critical regulator of the inflammatory response in sepsis and demonstrated PKC? inhibition was lung protective. However, the role of PKC? in sepsis-induced platelet activation and platelet-leukocyte interactions is not known. In this study, rats underwent sham surgery or cecal ligation and puncture (CLP) to induce sepsis. Following surgeries, a PKC? inhibitor (200?g/kg) or vehicle (PBS) was administered intra-tracheally. At 24 hours post-surgeries, lung tissue, BAL fluid, and blood samples were collected. While sepsis caused thrombocytopenia, the remaining circulating platelets were activated as demonstrated by increased p-selectin expression, elevated plasma PF4, and enhanced platelet-leukocyte aggregate formation compared to Sham animals. Platelet activation was associated with increased platelet PKC? activity. Inhibition of PKC? attenuated sepsis-induced platelet activation, secretion and aggregate formation. Sepsis-induced thrombocytopenia was also significantly reduced and circulating platelet numbers were similar to sham animals. In the lung, sepsis induced significant influx of platelets and neutrophils and the development of lung injury. Administration of the PKC? inhibitor decreased platelet and neutrophil influx, and was lung protective. Thus, PKC? inhibition modulated platelet activity both locally and systemically, decreased neutrophil influx into the lung, and was lung protective. We demonstrate for the first time that PKC? plays an important role in platelet activation and platelet-neutrophil interaction during sepsis.

Project description:Platelet-activating factor (PAF) is an important mediator of the systemic inflammatory response. In the case of sepsis, proper activation and function of neutrophils as the first line of cellular defense are based on a well-balanced physiological response. However, little is known about the role of PAF in cellular changes of neutrophils during sepsis. Therefore, this study investigates the reaction patterns of neutrophils induced by PAF with a focus on membrane potential (MP), intracellular pH, and cellular swelling under physiological and pathophysiological conditions and hypothesizes that the PAF-mediated response of granulocytes is altered during sepsis. The cellular response of granulocytes including MP, intracellular pH, cellular swelling, and other activation markers were analyzed by multiparametric flow cytometry. In addition, the chemotactic activity and the formation of platelet-neutrophil complexes after exposure to PAF were investigated. The changes of the (electro-)physiological response features were translationally verified in a human ex vivo whole blood model of endotoxemia as well as during polymicrobial porcine sepsis. In neutrophils from healthy human donors, PAF elicited a rapid depolarization, an intracellular alkalization, and an increase in cell size in a time- and dose-dependent manner. Mechanistically, the alkalization was dependent on sodium-proton exchanger 1 (NHE1) activity, while the change in cellular shape was sodium flux- but only partially NHE1-dependent. In a pathophysiological altered environment, the PAF-induced response of neutrophils was modulated. Acidifying the extracellular pH in vitro enhanced PAF-mediated depolarization, whereas the increases in cell size and intracellular pH were largely unaffected. Ex vivo exposure of human whole blood to lipopolysaccharide diminished the PAF-induced intracellular alkalization and the change in neutrophil size. During experimental porcine sepsis, depolarization of the MP was significantly impaired. Additionally, there was a trend for increased cellular swelling, whereas intracellular alkalization remained stable. Overall, an impaired (electro-)physiological response of neutrophils to PAF stimulation represents a cellular hallmark of those cells challenged during systemic inflammation. Furthermore, this altered response may be indicative of and causative for the development of neutrophil dysfunction during sepsis.

Dataset Information

Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis.

Publications

Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis.

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