B-Cell Activating Factor Secreted by Neutrophils Is a Critical Player in Lung Inflammation to Cigarette Smoke Exposure.

Cigarette smoke (CS) is the major cause of chronic lung injuries, such as chronic obstructive pulmonary disease (COPD). In patients with severe COPD, tertiary lymphoid follicles containing B lymphocytes and B cell-activating factor (BAFF) overexpression are associated with disease severity. In addition, BAFF promotes adaptive immunity in smokers and mice chronically exposed to CS. However, the role of BAFF in the early phase of innate immunity has never been investigated. We acutely exposed C57BL/6J mice to CS and show early BAFF expression in the bronchoalveolar space and lung tissue that correlates to airway neutrophil and macrophage influx. Immunostaining analysis revealed that neutrophils are the major source of BAFF. We confirmed in vitro that neutrophils secrete BAFF in response to cigarette smoke extract (CSE) stimulation. Antibody-mediated neutrophil depletion significantly dampens lung inflammation to CS exposure but only partially decreases BAFF expression in lung tissue and bronchoalveolar space suggesting additional sources of BAFF. Importantly, BAFF deficient mice displayed decreased airway neutrophil recruiting chemokines and neutrophil influx while the addition of exogenous BAFF significantly enhanced this CS-induced neutrophilic inflammation. This demonstrates that BAFF is a key proinflammatory cytokine and that innate immune cells in particular neutrophils, are an unconsidered source of BAFF in early stages of CS-induced innate immunity

Restaurer une pelouse sèche Méditerranéenne en France par l'utilisation de diverses méthodes de transfert d'espèces

International audienceMediterranean dry grasslands are characterized by a high biodiversity which is threatened by significant changes in land-use in the last decades. The La Crau area is the only French Mediterranean steppe located in South-Eastern France. From the 45,000ha occurring in the 16th century, only 11,500ha are currently remaining. Moreover numerous studies have shown a very low resilience of this plant community after major disturbances, such as cultivation, even on the very long term (150 yrs). This has stressed both the importance of conserving remnant patches and restoring plant community. Several experiments testing species-transfer methods have been carried out in the last decade. In 2002 the transplantation of two perennial target species: Thymus vulgaris and Brachypodium retusum in former cultivated fields showed that their establishment was successful if the stone cover had been previously restored. The transfer of vacuum-harvested hay was assessed in 2007 on an area disturbed by pipeline burying. This method allowed the plant composition to be close to that of the reference community, with many target annual species, but without some dominant perennial species. In 2009, a multi-treatment experiment was implemented on a larger area disturbed by intense peach cultivation where hay transfer and soil transfer, combined or not with topsoil removal were experimented. The best results were obtained when both abiotic conditions were restored (topsoil removal, soil transfer) and species were transferred (soil transfer, hay transfer combined with topsoil removal). In 2011, large scale soil transfers with or without soil compaction were implemented again on an area degraded by an oil spill where soil had been excavated. On the very short term, soil transfers showed a species-rich community composed of numerous target species. Their combination with soil compaction or topsoil removal allowed decreasing the sometimes too dense cover of grasses occurring on other restoration treatments. Results from these ten years of diverse experiments and monitoring highlight the difficulties of restoring this unique habitat. Nevertheless they provide insights on possibilities of approaching the target communities, especially when the transfer of the whole community is combined with the restoration of appropriate abiotic conditions

Restaurer une pelouse sèche Méditerranéenne en France par l'utilisation de diverses méthodes de transfert d'espèces

International audienceMediterranean dry grasslands are characterized by a high biodiversity which is threatened by significant changes in land-use in the last decades. The La Crau area is the only French Mediterranean steppe located in South-Eastern France. From the 45,000ha occurring in the 16th century, only 11,500ha are currently remaining. Moreover numerous studies have shown a very low resilience of this plant community after major disturbances, such as cultivation, even on the very long term (150 yrs). This has stressed both the importance of conserving remnant patches and restoring plant community. Several experiments testing species-transfer methods have been carried out in the last decade. In 2002 the transplantation of two perennial target species: Thymus vulgaris and Brachypodium retusum in former cultivated fields showed that their establishment was successful if the stone cover had been previously restored. The transfer of vacuum-harvested hay was assessed in 2007 on an area disturbed by pipeline burying. This method allowed the plant composition to be close to that of the reference community, with many target annual species, but without some dominant perennial species. In 2009, a multi-treatment experiment was implemented on a larger area disturbed by intense peach cultivation where hay transfer and soil transfer, combined or not with topsoil removal were experimented. The best results were obtained when both abiotic conditions were restored (topsoil removal, soil transfer) and species were transferred (soil transfer, hay transfer combined with topsoil removal). In 2011, large scale soil transfers with or without soil compaction were implemented again on an area degraded by an oil spill where soil had been excavated. On the very short term, soil transfers showed a species-rich community composed of numerous target species. Their combination with soil compaction or topsoil removal allowed decreasing the sometimes too dense cover of grasses occurring on other restoration treatments. Results from these ten years of diverse experiments and monitoring highlight the difficulties of restoring this unique habitat. Nevertheless they provide insights on possibilities of approaching the target communities, especially when the transfer of the whole community is combined with the restoration of appropriate abiotic conditions

The NLRP3 inflammasome is activated by nanoparticles through ATP, ADP and adenosine.

International audienceThe NLR pyrin domain containing 3 (NLRP3) inflammasome is a major component of the innate immune system, but its mechanism of activation by a wide range of molecules remains largely unknown. Widely used nano-sized inorganic metal oxides such as silica dioxide (nano-SiO2) and titanium dioxide (nano-TiO2) activate the NLRP3 inflammasome in macrophages similarly to silica or asbestos micro-sized particles. By investigating towards the molecular mechanisms of inflammasome activation in response to nanoparticles, we show here that active adenosine triphosphate (ATP) release and subsequent ATP, adenosine diphosphate (ADP) and adenosine receptor signalling are required for inflammasome activation. Nano-SiO2 or nano-TiO2 caused a significant increase in P2Y1, P2Y2, A2A and/or A2B receptor expression, whereas the P2X7 receptor was downregulated. Interestingly, IL-1β secretion in response to nanoparticles is increased by enhanced ATP and ADP hydrolysis, whereas it is decreased by adenosine degradation or selective A2A or A2B receptor inhibition. Downstream of these receptors, our results show that nanoparticles activate the NLRP3 inflammasome via activation of PLC-InsP3 and/or inhibition of adenylate cyclase (ADCY)-cAMP pathways. Finally, a high dose of adenosine triggers inflammasome activation and IL-1β secretion through adenosine cellular uptake by nucleotide transporters and by its subsequent transformation in ATP by adenosine kinase. In summary, we show for the first time that extracellular adenosine activates the NLRP3 inflammasome by two ways: by interacting with adenosine receptors at nanomolar/micromolar concentrations and through cellular uptake by equilibrative nucleoside transporters at millimolar concentrations. These findings provide new molecular insights on the mechanisms of NLRP3 inflammasome activation and new therapeutic strategies to control inflammation

Interaction Proteomics Suggests a New Role for the Tfs1 Protein in Yeast

International audienceThe PEBP (phosphatidylethanolamine-binding protein) family is a large group of proteins whose human member, hPEBP1, has been shown to play multiple functions, influencing intracellular signaling cascades, cell cycle regulation, neurodegenerative processes, and reproduction. It also acts, by an unknown mechanism, as a metastasis suppressor in a number of cancers. A more complete understanding of its biological role is thus necessary. As the yeast Saccharomyces cerevisiae is a powerful and easy to handle model organism, we focused on Tfs1p, the yeast ortholog of hPEBP1. In a previous study based on a two-hybrid approach, we showed that Tfs1p interacts and inhibits Ira2p, a GTPase Activating Protein (GAP) of the small GTPase Ras. To further characterize the molecular functions of Tfs1p, we undertook the identification of protein complexes formed around Tfs1p using a targeted proteomics approach. Complexed proteins were purified by tandem-affinity, cleaved with trypsin, and identified by nanoflow liquid chromatography coupled with tandem mass spectrometry. Overall, 14 new interactors were identified, including several proteins involved in intermediate metabolism. We confirmed by co-immunoprecipitation that Tfs1p interacts with Glo3p, a GAP for Arf GTPases belonging to the Ras superfamily of small GTPases, indicating that Tfs1p may be involved in the regulation of another GAP. We similarly confirmed the binding of Tfs1p with the metabolic enzymes Idp1p and Pro1p. Integration of these results with known functional partners of Tfs1p shows that two subnetworks meet through the Tfs1p node, suggesting that it may act as a bridge between cell signaling and intermediate metabolism in yeast