Project

Discipline

Protease; Neutrophils; Lung; Inflammation; Serpins; Apoptosis

Lead
Le but de notre recherche est d’identifier de nouveaux mécanismes cellulaires et moléculaires liés à la régulation des protéases par les serpines intracellulaires des cellules du système immunitaire dans les processus de mort cellulaire et dans les maladies inflammatoires.
Lay summary
Les protéases stockées dans les granules des cellules du système immunitaire sont des enzymes qui contribuent à la fois aux fonctions protectrices et destructrices de l’inflammation. Ces protéases tuent directement les agents pathogènes, les cellules cancéreuses ou celles infectées par des virus, et inactivent les toxines bactériennes. Cependant, un excès de protéases contribue également à la destruction des tissus et amplifie la réaction inflammatoire au détriment de l’hôte. La mort des cellules inflammatoires comme les neutrophiles contribue dans une large mesure à la libération d’un excès de protéases et alimente un cercle vicieux pro-inflammatoire. De nombreuses études ont porté sur la régulation des protéases par des inhibiteurs sécrétés tels que l’antitrypsine du plasma. Nos recherches récentes ont permis d’identifier un rôle protecteur prépondérant pour l’inhibiteur intracellulaire serpinB1 qui bloque l’activité des protéases des neutrophiles dans les infections pulmonaires et qui régule la survie des neutrophiles in vivo. Nous proposons d'élucider le rôle d’un groupe de serpines intracellulaires (dont serpinB1) dans les mécanismes de mort cellulaire et de l’inflammation et d'identifier l'importance relative des différentes protéases et serpines dans ces processus. Ces études seront utiles pour mieux cibler les protéases impliquées dans la mort cellulaire et l'inflammation dans les pathologies infectieuses et non infectieuses.

Direct link to Lay Summary

Last update: 08.10.2013

Active participation

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Inflammatory responses are vital to preserve host integrity and survival following infection with pathogens. Genetic and environmental factors, however, contribute to modify, enhance or sustain these responses leading inflammatory diseases. Excessive acute amplification can lead to severe disease and lethality such as in acute respiratory distress syndrome and septic shock. Chronic inflammation is associated with sustained release of cytokines and enzymes leading to altered antimicrobial responses, reduced organ function and tissue destruction such as in cystic fibrosis (CF), asthma or chronic obstructive pulmonary disease (COPD) and emphysema. Serine proteases carried in neutrophil and mast cell granules are indiscriminate in their activity and have been shown to contribute to both protective and destructive inflammatory functions. These proteases directly kill pathogens and inactivate toxins but they also induce discrete proteolysis of host proteins with often detrimental consequences. Chronic release of these enzymes in the extracellular milieu, like in CF lung disease, COPD and arthritis, is thought to drive sustained tissue injury and inflammation. At these inflammatory sites, neutrophil death contributes to a large extent to excess protease release and fuels a cycle of that leads to increased neutrophil recruitment and tissue damage. Many studies have focused on neutrophil elastase, its targets and its regulation by plasma and secreted protease inhibitors such as a1-antitrypsin. We propose to investigate the role of the little studied, but increasingly recognized, family of intracellular (clade B) serpins in cellular homeostasis and inflammation.We have previously established that serpinB1, a potent intracellular inhibitor of neutrophil granule proteases (elastase, cathepsin G and proteinase-3), is required to prevent early neutrophil death both at inflammatory sites as well as in the bone marrow. Mice lacking serpinB1 have a severely reduced reserve of mature neutrophils in the bone marrow; they fail to clear Pseudomonas lung infection and have increased morbidity in influenza A virus infection. In these models, lack of serpinB1 is also associated with increased and sustained production of pro-inflammatory cytokines. We have recently identified that the cytoprotective role of serpinB1 depends on the inhibition of cathepsin G in a cell-intrinsic manner. Cathepsin G, but not neutrophil elastase, induced neutrophil death upon granule membrane permeabilization. In the first aim of this proposal, we will define the molecular and cellular signals that trigger the intracellular release of cathepsin G from granules leading to cell death in neutrophils in steady state and in inflammation. We will also investigate the function of serpinB1 and related serpins in mast cell homeostasis and granule-mediated death. In the second aim, we will investigate molecular mechanisms by which serpinB1 regulates neutrophil proteases in mouse models of inflammation. The proposed studies will generate novel findings on the fundamental cytoprotective functions of intracellular serpins and identify the relative importance of different granule proteases and serpins in amplifying and sustaining inflammation. These studies will be highly relevant for better targeting detrimental feedback loops involved in cell death and inflammation in infectious and non-infectious pathologies.