Optimisation de la production des acides gras polyinsaturés à longue chaine oméga-3 et de leurs métabolites oxygénés chez Ostreococcus tauri

Les acides gras polyinsaturés (AGPIs) à longue chaine oméga-3, essentiels à la santé et au développement chez l'homme, sont les précurseurs de médiateurs lipidiques jouant des rôles importants au maintien de l'homéostasie tissulaire. Ces métabolites oxygénés, et collectivement appelés oxylipines, sont impliqués dans la régulation de nombreux processus physiopathologiques tels que l'inflammation ou le cancer. De nouvelles sources alternatives et durables d'AGPIs n-3 étant requises pour répondre à la demande mondiale croissante, les microalgues, producteurs primaires d'AGPIs n-3, représentent une source naturelle d'intérêt pour la production de ces macromolécules à haute valeur ajoutées. Dans ce contexte, le présent travail visait à évaluer le potentiel de la microalgue pico-eucaryote Ostreococcus comme source alternative d'AGPIs n-3 et de leurs oxylipines dérivées. Cette étude a démontré que les microalgues du genre Ostreococcus contiennent de forts taux d'AGPIs, les oméga-3 étant majoritaires. En particulier, les cellules d'Ostreococcus ont montré de forts taux de DHA qui restaient relativement stables au cours de la croissance des cultures ainsi qu’avec des conditions de température, intensités lumineuses et salinité très variables. La biomasse d'Ostreococcus a montré un ensemble d'oxylipines dérivées d’AGPIs n-3 et n-6. Deux mono-hydroxy acides dérivés du DHA, les 17-HDoHE et 14-HDoHE, se sont avérés majoritaires dans les cellules d’Ostreococcus, et ce, indépendamment de la souche et des conditions de culture. En outre, des approches de génie génétique ont été réalisées avec succès pour augmenter les concentrations cellulaires d’oxylipines.Omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs) that are essential to human health and development are precursors of lipid mediators that play important roles for tissue homeostasis. These metabolites derived from lipid oxidation processes and collectively named oxylipins, are involved in the regulation of various physiopathological processes including inflammation and cancer. As the global consumer needs for n-3 LC-PUFAs is increasing the fishes market will likely not be sufficient and new alternative sources of n-3 LC-PUFAs are needed. Microalgae are an interesting natural source as primary producers of n-3 LC-PUFAs and therefore, a possible source of these high-values added macromolecules. In this context, the present work aimed to evaluate the potential of the green picoeukaryote Ostreococcus as a source of n-3 PUFAs and derived oxylipins. This study clearly revealed microalgae of the genus Ostreococcus contain high levels of PUFAs, the omega-3 being predominant over the omega-6. Particularly, Ostreococcus cells showed high docosahexaenoic acid (DHA, C22:6 n-3) levels that remained fairly stable throughout the growth cycle and under various temperature, light intensity and salinity stress conditions. The biomass of Ostreococcus showed an array of oxylipins derived from PUFAs from the n-3 and n-6 series. In particular, two monohydroxy acids derived from DHA, 17-HDoHE and 14-HDoHE, were found to be predominant in Ostreococcus cells regardless the strain or the culture conditions tested. Furthermore, genetic engineering approach was successfully used to increase oxylipins content

Peptide Vectors Carry Pyrene to Cell Organelles Allowing Real‐Time Quantification of Free Radicals in Mitochondria by Time‐Resolved Fluorescence Microscopy

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Oxidative stress does not play a primary role in the toxicity induced with clinical doses of doxorubicin in myocardial H9c2 cells

International audienceThe implication of oxidative stress as primary mechanism inducing doxorubicin (DOX) cardiotoxicity is still questionable as many in vitro studies implied supra-clinical drug doses or unreliable methodologies for reactive oxygen species (ROS) detection. The aim of this study was to clarify whether oxidative stress is involved in compliance with the conditions of clinical use of DOX, and using reliable tools for ROS detection. We examined the cytotoxic mechanisms of 2 μM DOX 1 day after the beginning of the treatment in differentiated H9c2 rat embryonic cardiac cells. Cells were exposed for 2 or 24 h with DOX to mimic a single chronic dosage or to favor accumulation, respectively. We found that apoptosis was prevalent in cells exposed for a short period with DOX: cells showed typical hallmarks as loss of anchorage ability, mitochondrial hyperpolarization followed by the collapse of mitochondrial activity, and nuclear condensation. Increasing the exposure period favored a shift to necrosis as the cells preferentially exhibited early DNA impairment and nuclear swelling. In either case, measuring the fluorescence lifetime of 1-pyrenebutyric acid or the intensities of dihydroethidium or amplex red showed a consistent pattern in ROS production which was a slight increased level far from representative of an oxidative stress. Moreover, pre-treatment with dexrazoxane provided a cytoprotective effect although it failed to detoxify ROS. Our data support that oxidative stress is unlikely to be the primary mechanism of DOX cardiac toxicity in vitro