STRESS, MEMBRANE ET SIGNALISATION

Plasma membranes undergo environmental stresses induced for example by polycyclic aromatic hydrocarbons (PAH), ethanol or therapeutical agents such as cisplatin. We have previously shown that early membrane remodeling (alterations of fluidity and reorganization of lipid rafts) plays an important role in cell death induced by these types of stress. Our project is aimed at identifying the early molecular mechanisms involved in the toxicity of PAH or the cytokine TRAIL (TNF-Related Apoptosis Inducing Ligand), possibly in association with lifestyle or diet factors (PUFA, ethanol, long-chain n-3 polyunsaturated fatty acids), short chain fatty acids (SCFA; propionibacteria or acidic stress). The outcome of this work will help prevent cytotoxic effects of chemical compounds  and might help render TRAIL more efficient thus improving anti-cancer therapy. The contribution of lipid rafts and ceramide to cystic fibrosis (CF), an inflammatory disease from a pulmonary and systemic point of view, are also being studied. Our project is based on the development of the Membrane Stress Platform.

Effects of lifestyle (PUFA and ethanol intake) on the membrane signaling induced by PAH. Membrane remodeling is studied during the course of treatment with benzo(a)pyrene and/or ethanol or dietary lipids (PUFA). Various factors involved in membrane remodeling such as production of reactive metabolites or alteration of lipid metabolism enzymes (e.g. acid sphingomyelinase, HMGCoA reductase, D9desaturase), oxidative stress, ionic homeostasis (H⁺ and Ca²⁺), organelle dysfunction (mitochondria, cytoskeleton or lysosomes) are being investigated. In addition, we explore the connection between the modulation of the plasma membrane biophysical parameters and the signaling of cell death.

Modulation of TRAIL signaling by SCFA/propionibacteria or acidic extracellular pH (pHe). We study the molecular mechanisms responsible for synergy of TRAIL with SCFA at the plasma membrane and in mitochondria. The synergy between propionibacteria and TRAIL is investigated in in vivo colon cancer models. A propionibacterial expression and secretion plasmid newly developed in STLO (INRA, Agrocampus Ouest, Rennes) is being adapted for a strong and constitutive secretion of TRAIL (brevet FR10/53750); the recombinant strain will be tested in vivo. An acidic pHe is a characteristic of human solid tumors and switches TRAIL-induced apoptosis to necroptosis. In this context, we search for new RIPK1 partners and new potential RIPK1 inhibitors.

Role of lipids in inflammation associated with cystic fibrosis. The loss of CFTR function might cause impairments in lipid homeostasis which could contribute to chronic inflammation in cystic fibrosis (CF). Macrophages are involved early in the inflammatory process. However they are poorly studied in CF owing to invasive collection of bronchoalveolar lavage in CF patients. Moreover, it was demonstrated that determining how CFTR is involved in the metabolism of some lipids, cholesterol and ceramide, seems to be important for understanding the pathophysiology of CF. In this context, we seek to understand how defective CFTR affects cellular lipid homeostasis and if there is a link with inflammation  in primary human macrophage which should help elucidate the importance of CFTR’s role in CF pathophysiology (supported by “Vaincre La Mucoviscidose”).