Septic shock is the most serious stage of infection and the leading cause of death in intensive care. It is characterized by an exaggerated systemic inflammatory state in response to infection of the body by a pathogen, which can lead to organ dysfunction and circulatory failure. In practical terms, treatments for septic shock have not changed much over the past two decades and continue to be focused on fighting infection and supporting or supplementing failed systems. This acute inflammation may have repercussions on coagulation with activation of blood platelets and onset of disseminated intravascular coagulation (DIC), which considerably worsens the prognosis of patients with septic shock. Among the activators of inflammation cells and platelets, extracellular nucleotides (ADP and ATP) play a central role. ADP and ATP, released by dead cells or damaged tissues or by activated platelets, constitute danger signals or DAMP “damage-associated molecular pattern”, capable of recruiting and activating the cells of the inflammation. ADP and ATP also activate blood platelets, which play a central role in stopping bleeding but also in the formation of thrombosis. There are three platelet ADP and ATP receptors: two ADP-activated G protein-coupled receptors, P2Y1 and P2Y12, and an ATP-activated P2X1 ion channel. The P2Y12 receptor is the molecular target of clopidogrel (Plavix®) and prasugrel (Efient®), among the most prescribed antithrombotic drugs. Apart from platelets, these receptors are expressed on many cells involved in the inflammatory response, namely leukocytes (neutrophils, monocytes / macrophages), endothelial cells and vascular smooth muscle cells. To date, the roles of these P2 receptors during septic shock have yet to be elucidated. The objective is to better understand the role of P2Y1, P2Y12 and P2X1 receptors in septic shock.

We will use a mouse model of polymicrobial septic shock (peritonitis induced by ligation and caecal perforation) in place in the laboratory. The role of the P2Y1, P2Y12 and P2X1 receptors will be evaluated in this model using mutated mice for each of these receptors and available in the laboratory. Pharmacological inhibitors of these receptors will also be evaluated. In the following, to determine the respective contribution of these receptors present on the different cell populations (platelets, endothelial cells, leukocytes), mice having a deletion of these receptors in a specific tissue manner will be evaluated. For each condition, parameters such as tissue damage, infiltration of neutrophils and platelets will be evaluated by histological analysis of the various organs (lung, liver, kidney). In the blood, we will evaluate the systemic inflammation by ELISA assay of different cytokines and chemokines, activation of coagulation and fibrinolysis. The intensity of activation of platelets and neutrophils will be determined using surface markers by flow cytometry as well as by the release of NETs (Neutrophil Extracellular Traps).
All of this work will better define the role of P2 receptors in septic shock. It should make it possible to identify new pharmacological targets for new and effective therapeutic strategies.

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