Acides gras polyinsaturés oméga 3 et toxicité hépatique de l'éthanol : rôle du remodelage membranaire

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A role for lipid rafts in the protection afforded by docosahexaenoic acid against ethanol toxicity in primary rat hepatocytes.

International audience: Previously, we demonstrated that eicosapentaenoic acid enhanced ethanol-induced oxidative stress and cell death in primary rat hepatocytes via an increase in membrane fluidity and lipid raft clustering. In this context, another n-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), was tested with a special emphasis on physical and chemical alteration of lipid rafts. Pretreatment of hepatocytes with DHA reduced significantly ethanol-induced oxidative stress and cell death. DHA protection could be related to an alteration of lipid rafts. Indeed, rafts exhibited a marked increase in membrane fluidity and packing defects leading to the exclusion of a raft protein marker, flotillin. Furthermore, DHA strongly inhibited disulfide bridge formation, even in control cells, thus suggesting a disruption of protein-protein interactions inside lipid rafts. This particular spatial organization of lipid rafts due to DHA subsequently prevented the ethanol-induced lipid raft clustering. Such a prevention was then responsible for the inhibition of phospholipase C-γ translocation into rafts, and consequently of both lysosome accumulation and elevation in cellular low-molecular-weight iron content, a prooxidant factor. In total, the present study suggests that DHA supplementation could represent a new preventive approach for patients with alcoholic liver disease based upon modulation of the membrane structures

Role of plasma membrane lipid composition on cellular homeostasis: learning from cell line models expressing fatty acid desaturases

Experimental evidence has suggested that plasma membrane (PM)-associated signaling and hence cell metabolism and viability depend on lipid composition and organization. The aim of the present work is to develop a cell model to study the endogenous polyunsaturated fatty acids (PUFAs) effect on PM properties and analyze its influence on cholesterol (Chol) homeostasis. We have previously shown that by using a cell line over-expressing stearoyl-CoA-desaturase, membrane composition and organization coordinate cellular pathways involved in Chol efflux and cell viability by different mechanisms. Now, we expanded our studies to a cell model over-expressing both Δ5 and Δ6 desaturases, which resulted in a permanently higher PUFA content in PM. Furthermore, this cell line showed increased PM fluidity, Chol storage, and mitochondrial activity. In addition, human apolipoprotein A-I-mediated Chol removal was less efficient in these cells than in the corresponding control. Taken together, our results suggested that the cell functionality is preserved by regulating PM organization and Chol exportation and homeostasis.Fil: Jaureguiberry, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Bioquímicas de la Plata; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Tricerri, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Bioquímicas de la Plata; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Sanchez, Susana A.. University Of California At Irvine. Laboratory of Fluorescence Dynamics; Estados UnidosFil: Finarelli, Gabriela Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Bioquímicas de la Plata; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Montanaro, Mauro Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Bioquímicas de la Plata; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Prieto, Eduardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Bioquímicas de la Plata; ArgentinaFil: Rimoldi, Omar Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Bioquímicas de la Plata; Argentina. Universidad Nacional de La Plata; Argentin

Physical and chemical modulation of lipid rafts by a dietary n-3 polyunsaturated fatty acid increases ethanol-induced oxidative stress.

International audienceDietary n-3 polyunsaturated fatty acids (n-3 PUFAs) have been reported to modulate lipid raft-dependent signaling, but not yet lipid raft-dependent oxidative stress. Previously, we have shown that ethanol-induced membrane remodeling, i.e., an increase in membrane fluidity and alterations in physical and biochemical properties of lipid rafts, participated in the development of oxidative stress. Thus, we decided to study n-3 PUFA effects in this context, by pretreating hepatocytes with eicosapentaenoic acid (EPA), a long-chain n-3 PUFA, before addition of ethanol. EPA was found to increase ethanol-induced oxidative stress through membrane remodeling. Addition of EPA resulted in a marked increase in lipid raft aggregation compared to ethanol alone. In addition, membrane fluidity of lipid rafts was markedly enhanced. Interestingly, EPA was found to preferentially incorporate into nonraft membrane regions, leading to raft cholesterol increase. Lipid raft aggregation by EPA enhanced phospholipase Cγ translocation into these microdomains. Finally, phospholipase Cγ was shown to participate in the potentiation of oxidative stress by promoting lysosome accumulation, a major source of low-molecular-weight iron. To conclude, the ability of EPA to modify lipid raft physical and chemical properties plays a key role in the enhancement, by this dietary n-3 PUFA, of ethanol-induced oxidative stress