Président du jury Le Moine, Alain
Promoteur Communi, Didier
Publication Non publié, 2012-08-20
| Résumé : | Amongst respiratory diseases, inflammatory lung diseases constitute a major part of public health problem. As a consequence, investigating the immune mechanisms that contribute to the pathogenesis of these diseases is essential to identify candidate targets for the development of new therapeutic drugs. Furthermore, over the past 20 years, the growing awareness that purinergic signalling events shape the immune and inflammatory responses to infection and allergic reactions warranted the development of animal models to assess their importance in vivo in acute lung injury and chronic airway diseases. The field of purinergic inflammation formulated the unifying concept that ATP is released as a «danger signal» to induce inflammatory responses upon binding purinergic receptors. According to these elements, we began in 2007 to evaluate lung inflammation in mice deficient for the P2Y2 purinergic receptor in TH2 and TH1 models. The most convincing evidence that the P2Y2 receptor is engaged during alarm situations comes from studies related to cystic fibrosis and asthma. Indeed, chronic respiratory diseases are commonly associated with elevated airway ATP concentrations, as reported in cystic fibrosis, but also in idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease (COPD) patients, and they are raised by allergens in asthmatic patients. First, we demonstrated a significant role of the P2Y2R in a TH2-ovalbumin(OVA)-induced asthma model. We observed that eosinophil accumulation, a distinctive feature of lung allergic inflammation, was defective in OVA-treated P2Y2-deficient mice compared with OVA-treated wild type animals. Interestingly, the upregulation of VCAM-1 was lower on lung endothelial cells of OVA-treated P2Y2 knockout mice compared with OVA-treated wild type animals. Adhesion assays demonstrated that the action of UTP on leukocyte adhesion through the regulation of endothelial VCAM-1 was abolished in P2Y2-deficient lung endothelial cells. Additionally, the level of soluble VCAM-1, reported as an inducer of eosinophil chemotaxis, was strongly reduced in the bronchoalveolar lavage fluid of P2Y2-deficient mice. Secondly, we studied the consequences of P2Y2R loss in lung inflammation initiated after pneumonia virus of mice (PVM) infection in collaboration with the group of Pr. Daniel Desmecht (ULg). We demonstrated here that P2Y2 -/- mice display a severe increase in morbidity and mortality rate in response to PVM. Lower survival of P2Y2 -/- mice was not correlated with excessive inflammation despite the higher level of neutrophil recruiters in their broncho-alveolar fluids. Interestingly, we observed lower numbers of dendritic cells, CD4 + T cells and CD8 + T cells in P2Y2 -/- mice compared to P2Y2 +/+ infected lungs. Lower level of IL-12 and higher level of IL-6 in broncho-alveolar fluid support an inhibition of Th1 response in P2Y2 -/- mice. Quantification of DC recruiter expression revealed comparable IP-10 and MIP-3 levels but a reduced BRAK level in P2Y2 -/- compared to P2Y2 +/+ broncho-alveolar fluids. Higher morbidity and mortality of P2Y2 -/- mice appear to result from defective dendritic cell and T cell infiltration that could affect viral clearance in the lungs. In conclusion, our study reveals that the purinergic P2Y2 receptor previously described as a target in cystic fibrosis therapy, is a mediator of Th2 response in asthma, and is also involved in the initiation of Th1 response protecting mice against lung viral infection. |
