ATP-gated P2X1 ion channels protect against endotoxemia by dampening neutrophil activation.
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 P2X(1) ion channels are involved in promoting neutrophil chemotaxis.


OBJECTIVE
To elucidate the contribution of P2X(1) ion channels to sepsis and the associated disturbance of hemostasis.


METHODS
We used P2X(1) (-/-) mice in a model of lipopolysaccharide (LPS)-induced sepsis. Hemostasis and inflammation parameters were analyzed together with outcome. Mechanisms were further studied ex vivo with mouse and human blood or isolated neutrophils and monocytes.


RESULTS
P2X(1) (-/-) 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 P2X(1). However, whole blood platelet aggregation occurred normally, and P2X(1) (-/-) macrophages displayed normal levels of total tissue factor activity. We found that P2X(1) (-/-) neutrophils produced higher amounts of reactive oxygen species. Increased amounts of myeloperoxidase were released in the blood of LPS-treated P2X(1) (-/-) mice, and circulating neutrophils and monocytes expressed higher levels of CD11b. Neutrophil accumulation in the lungs was also significantly augmented, as was lipid peroxidation in the liver. Desensitization of P2X(1) ion channels led to increased activation of human neutrophils and enhanced formation of platelet-leukocyte aggregates.


CONCLUSIONS
P2X(1) ion channels play a protective role in endotoxemia by negatively regulating systemic neutrophil activation, thereby limiting the oxidative response, coagulation, and organ damage.
GIGA-Research, Human Genetics Unit, Laboratory of Cardiovascular Research, University of Liège, Liège, Belgium, France.
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Lecut
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Faccinetto
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Delierneux
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van Oerle
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Spronk
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Evans
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El Benna
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Bours
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Oury
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001777:Blood Coagulation; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism; D039481:CD11b Antigen / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D019446:Endotoxemia / Q000097:blood / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D006801:Humans; D015640:Ion Channel Gating; D008070:Lipopolysaccharides; D008099:Liver / Q000276:immunology / Q000378:metabolism; D008168:Lung / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000378:metabolism; D018375:Neutrophil Activation; D020556:Neutrophil Infiltration; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism; D010973:Platelet Adhesiveness; D017382:Reactive Oxygen Species / Q000378:metabolism; D058474:Receptors, Purinergic P2X1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018805:Sepsis / Q000097:blood / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D013997:Time Factors
D039481:CD11b Antigen; D016207:Cytokines; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D058474:Receptors, Purinergic P2X1; C440499:lipopolysaccharide, Escherichia coli O111 B4; D000255:Adenosine Triphosphate; D009195:Peroxidase