Purinergic receptor signaling: toward the identification of therapeutic targets in inflammatory lung diseases – PurPID

Inflammation is a fundamental immune mechanism of defense to infection or to non infectious tissue or cellular damage which allows eliminating pathogen or repairing damaged tissue allowing recovering normal conditions. Nevertheless, non regulated inflammation often leads to abnormal situation where the inflammatory response induces or worsens the pathology in infectious, auto-inflammatory and auto-immune diseases. Lung inflammation plays an important role in pulmonary diseases such as asthma, COPD and lung fibrosis with infiltrated immune cells which produce immune mediators such as chemokines and cytokines and induces the adaptive immune response leading to tissue destruction or abnormal repair. Recently important cellular and molecular mechanisms of inflammatory processes were put in light in particular by the discovery of the NLRP3 inflammasome which activation allows the maturation and secretion of interleukin-1beta (IL-1beta), an essential inflammatory cytokine (Martinon et al., 2009). NLRP3 inflammasome was discovered studying orphan auto-inflammatory diseases which were all due to different mutations in the NLRP3 receptor leading to constitutive activation of the NLRP3 inflammasome and excessive production of IL-1beta. NLRP3 inflammasome activation, IL-1beta production and secretion are the cornerstone of many inflammatory diseases and in particular of lung inflammatory disease (Martinon and Tschopp, 2004; McGonagle et al., 2007). We have shown the essential role of IL-1beta and NLRP3 activation in inflammation upon lung injury (Gasse et al., 2007; Gasse et al., 2009). A better understanding of the molecular and cellular mechanisms of pulmonary inflammation leading to fibrosis is absolutely required to identify new therapeutic targets in the fibrotic pathology without any efficient therapy. We propose to study the mechanisms of inflammation upon lung injury at different levels: at the organism level with studies in mice, at the tissue level with studies on patient biopsies, at the cellular level with studies with murine and human cells from experimental models or from patients and finally at the molecular level with the analysis of signaling protein partners of cellular receptors involved in the inflammatory responses.
The aims of this project are to determine whether extracellular ATP is a danger signal released upon lung injury, alerting the immune system and leading to IL-1ß-mediated lung inflammation and fibrosis. This program will focus on the role of purinergic signaling and particularly on P2X7, P2X4 receptors and pannexin-1 in ATP driven inflammation. The relationship between purinergic signaling and inflammation will be analyzed at the organism level with studies in mice, at the cellular level with murine and human primary or established cell lines and finally down to the molecular level with the identification of P2XR signaling complex involved in inflammation through a proteomic approach. Intracellular pathways linking P2XR to inflammatory phenotypes will be established through the combination of molecular, cellular and integrated models. In parallel, further characterization of ATP as endogenous danger signal induced and/or released by dying cells will be address in clinical material obtained from patients with interstitial pulmonary fibrosis (IPF). Analysis of the expression of P2XR and inflammatory associated molecules in the lungs of patients with interstitial pulmonary fibrosis will be performed. Ultimately, this program should not only allow to validate purinergic receptors as potential therapeutic target in the treatment of lung inflammation, but also to identify new potential signaling targets downstream of these receptors.