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See detailATP-gated P2X1 ion channels protect from endotoxemia by dampening neutrophil activation
Lecut, Christelle ULg; Faccinetto, Céline ULg; Delierneux, Céline ULg et al

in Journal of Thrombosis and Haemostasis [=JTH] (2012), 10(3), 453-65

Background: In sepsis, extracellular ATP, secreted by activated platelets and leukocytes, may contribute to the crosstalk between hemostasis and inflammation. Previously, we showed that, in addition to ... [more ▼]

Background: In sepsis, extracellular ATP, secreted by activated platelets and leukocytes, may contribute to the crosstalk between hemostasis and inflammation. Previously, we showed that, in addition to their role in platelet activation, ATP-gated P2X1 ion channels are involved in promoting neutrophil chemotaxis. <br />Objectives: To elucidate the contribution of P2X1 ion channels to sepsis and associated disturbance of hemostasis. <br />Methods: We used P2X1-/- mice in a model of lipopolysaccharide (LPS)-induced sepsis. Hemostasis and inflammation parameters were analysed together with outcome. Mechanisms were further studied ex vivo using mouse and human blood or isolated neutrophils and monocytes. <br />Results: P2X1-/- mice were more susceptible to LPS-induced shock than wild-type mice despite normal cytokine production. Plasma levels of thrombin-antithrombin complexes were higher, thrombocytopenia was worsened and whole blood coagulation time was markedly reduced, pointing to aggravated hemostasis disturbance in the absence of P2X1. However, whole blood platelet aggregation occurred normally and P2X1-/- macrophages displayed normal levels of total tissue factor activity. We found that P2X1-/- neutrophils produced higher amounts of reactive oxygen species. Increased amounts of myeloperoxidase were released in the blood of LPS-treated P2X1-/- mice, and circulating neutrophils and monocytes expressed higher levels of CD11b. Neutrophil accumulation into the lungs was also significantly augmented, as was lipid peroxidation in the liver. Desensitization of P2X1 ion channels led to increased activation of human neutrophils and enhanced formation of platelet-leukocyte aggregates. [less ▲]

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See detailLack of P2X1 ion channels increases endotoxemia associated coagulation and organ damage through neutrophil hyperresponsiveness.
Lecut, Christelle ULg; Faccinetto, Céline ULg; Evans, Richard J et al

in Journal of Thrombosis and Haemostasis [=JTH] (2011), 9(suppl S2),

ATP-gated P2X1 ion channels contribute to arterial thrombosis by amplifying platelet activation. In the search for novel anti-platelet strategies, targeting P2X1 ion channels is appealing. However, in ... [more ▼]

ATP-gated P2X1 ion channels contribute to arterial thrombosis by amplifying platelet activation. In the search for novel anti-platelet strategies, targeting P2X1 ion channels is appealing. However, in this study we found that lack or inhibition of P2X1 channels enhanced neutrophil respiratory burst activity ex vivo. <br />To study the consequence of P2X1 deficiency on neutrophil function in vivo, P2X1-/- mice were used in a model of endotoxin-induced sepsis. Upon injection of lipopolysaccharides (LPS), plasma myeloperoxidase (MPO) concentrations reached higher levels in the P2X1-/- mice, and circulating neutrophils expressed higher levels of surface CD11b compared to wild-type mice. Neutrophil relocalization into the lungs of LPS-treated P2X1-/- mice was also significantly augmented, reflecting a higher activation state of P2X1-/- neutrophils under conditions of sepsis. Accordingly, more extensive lipid peroxidation was observed in the liver of LPS-treated P2X1-/- mice, indicative of exaggerated oxidative damage. Concomitantly, the levels of thrombin-antithrombin complexes were higher in the plasma of LPS-treated P2X1-/- mice and thrombocytopenia was worsened as compared to wild type mice. Elevated numbers of microthrombi were also found in the lungs of these mice. These observations coincided with a higher susceptibility of P2X1-/- mice to LPS-induced septic shock than wild type animals. <br />Our results strongly suggest that P2X1 ion channels play a protective role in sepsis by negatively regulating systemic neutrophil activation, thereby limiting oxidative damage, activation of coagulation and platelet accumulation into the lungs. Therefore, since antagonists of P2X1 ion channels may not only target platelets but also affect neutrophils, inhibiting these channels in the highly inflammatory environment of severe sepsis or of acute coronary syndromes might be detrimental. [less ▲]

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See detailP2X1 Ion Channels Promote Neutrophil Chemotaxis through Rho Kinase Activation
Lecut, Christelle ULg; Frederix, Kim ULg; Johnson, Daniel M et al

in Journal of Immunology (2009)

This study shows that activation of P2X1 ion channels by ATP promotes neutrophil chemotaxis, a process involving Rho kinase-dependent actomyosin-mediated contraction at the cell rear. These ion channels ... [more ▼]

This study shows that activation of P2X1 ion channels by ATP promotes neutrophil chemotaxis, a process involving Rho kinase-dependent actomyosin-mediated contraction at the cell rear. These ion channels may therefore play a significant role in host defense and inflammation. [less ▲]

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See detailContribution of ATP-gated P2X1 ion channels to the control of neutrophil chemotaxis.
Lecut, Christelle ULg; Frederix, Kim ULg; Johnson, Daniel et al

in Purinergic Signalling (2008), 4

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See detailP2X1 receptors as new regulators of neutrophil life span
Faccinetto, Céline ULg; Lecut, Christelle ULg; Jacobs, Nathalie ULg et al

in Journal of Thrombosis and Haemostasis [=JTH] (2007)

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See detailDe novo C16- and C24-ceramide generation contributes to spontaneous neutrophil apoptosis.
Seumois, Gregory; Fillet, Marianne ULg; Gillet, Laurent ULg et al

in Journal of Leukocyte Biology (2007), 81(6), 1477-1486

Neutrophils rapidly undergo spontaneous apoptosis following their release from the bone marrow. Although central to leukocyte homeostasis, the mechanisms that regulate neutrophil apoptosis remain poorly ... [more ▼]

Neutrophils rapidly undergo spontaneous apoptosis following their release from the bone marrow. Although central to leukocyte homeostasis, the mechanisms that regulate neutrophil apoptosis remain poorly understood. We show here that apoptosis of cultured neutrophils is preceded by a substantial increase in the intracellular levels of 16 and 24 carbon atom (C(16)- and C(24))-ceramides, which are lipid second messengers of apoptosis and stress signaling. Treatment of neutrophils with fumonisin B(2), a selective inhibitor of the de novo pathway of ceramide synthesis, prevented accumulation of C(16)- and C(24)-ceramides. Moreover, fumonisin B(2) significantly reduced caspase-3, -8, and -9 activation and apoptosis in these cells. Conversely, 3-O-methylsphingomyelin and fantofarone, which are specific inhibitors of neutral and acid sphingomyelinases, respectively, neither inhibited C(16)- and C(24)-ceramide production nor decreased the apoptosis rate in neutrophils, indicating that in these cells, ceramides are not generated from membrane sphingomyelin. Further experiments showed that increasing endogenous C(16)- and C(24)-ceramide levels by using DL-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol and (1S,2R)-D-erythro-2-(N-myristoylamino)-1-phenyl-1-propanol, two inhibitors of ceramide metabolism, enhances caspase-3, -8, and -9 activity and increases neutrophil apoptosis. Similarly, apoptosis was induced rapidly when synthetic C(16)- and/or C(24)-ceramides were added to neutrophil cultures. Finally, GM-CSF, a cytokine that delays neutrophil apoptosis, abrogated C(16)- and C(24)-ceramide accumulation totally in cultured neutrophils, whereas Fas ligation accelerated apoptosis in these cells without affecting de novo ceramide production. We conclude that de novo generation of C(16)- and C(24)-ceramides contributes to spontaneous neutrophil apoptosis via caspase activation and that GM-CSF exerts its antiapoptotic effects on neutrophils, at least partly through inhibition of ceramide accumulation. [less ▲]

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