La signalisation redox en hypertension artérielle

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

A contribution to the study of the germination and conservation of Argania spinosa (L.) Skeels seeds in Tindouf area (Algeria)

Les graines d’Arganier perdent rapidement leur faculté germinative lors de la conservation. La fragilité des graines est probablement due à leur richesse en huile dont les produits d’oxydation seraient toxiques pour l’embryon. L'objectif de la présente étude est de tester la capacité germinative des graines et à comprendre les changements biochimiques provoquant sa perte lors de la conservation de graines. Les graines étudiées provenaient du peuplement naturel de la région de Tindouf (Algérie). L’évolution de la faculté germinative, de la teneur en acides gras et en malondialdehyde a été suivie durant la conservation des graines dans des conditions ambiantes et à basse température. Les résultats ont révélé que les graines fraîchement récoltées présentent un taux de germination élevé (92 %). Après trois ans de conservation, une perte significative de la capacité de germination a été observée. Cette perte est fortement corrélée à une diminution de la teneur en acide gras polyinsaturées et à une importante accumulation en malondialdéhyde. Par contre, les graines d’Arganier stockées à basses températures (4°C) présentent des baisses du pouvoir germinatif plus faibles et une accumulation du malondialdéhyde moins importante que les graines stockées dans des conditions ambiantes. Le froid permet de limiter la peroxydation des lipides ainsi que la perte de la faculté germinative et la détérioration des graines d’Arganier.Argan seeds easily lose their germination capacity during storage. The fragility of these seeds is probably due to their content of oil of which oxidation products are toxic to the embryo. This study aims at testing germinal capacity and understanding the biochemical changes causing its loss during storage of Argan seeds coming from the natural population of the Tindouf region (Algeria). The evolution of the fatty acid content and the accumulation of malondialdehyde during seeds storage at ambient conditions and low temperature (+4°C) was followed. The overall results showed a high germination rate (92%) of freshly harvested seeds as well as a significant loss of germination capacity after three years of seeds stored whatever the storage conditions are. This loss of germinal capacity is strongly related to a decrease in polyunsaturated fatty acid content and to a significant accumulation of malondialdehyde. However when seeds were stored in cold conditions (+4°C) the loss of germinal capacity and the accumulation of malondialdehyde were less than for seeds stored under ambient conditions. Cold would therefore limit the loss of germinal capacity by reducing the lipid peroxidation of Argan seed reserves

MicroRNA-223 coordinates cholesterol homeostasis

Results from this study represent a breakthrough in our understanding of posttranscriptional control of cholesterol metabolism and how microRNAs (miRNAs) are at the heart of cholesterol regulatory circuitry and homeostasis. Although cells are adept at maintaining proper cholesterol levels, it was unknown how cells posttranscriptionally coordinate cholesterol uptake, efflux, and synthesis. MicroRNA-223 (miR-223) transcription and expression are maintained by cholesterol, and, as a feedback network, miR-223 inhibits cholesterol biosynthesis and uptake and increases cholesterol efflux. This study clearly demonstrates the extensive role that miRNAs play in coordinating metabolic adaptation to disease and general homeostasis. This work highlights a unique regulatory control point for cholesterol homeostasis and illustrates how important the study of miRNAs is to the greater understanding of dyslipidemia and cardiovascular disease

HDL-transferred microRNA-223 regulates ICAM-1 expression in endothelial cells

High-density lipoproteins (HDL) have many biological functions, including reducing endothelial activation and adhesion molecule expression. We recently reported that HDL transport and deliver functional microRNAs (miRNA). Here we show that HDL suppresses expression of intercellular adhesion molecule 1 (ICAM-1) through the transfer of miR-223 to endothelial cells. After incubation of endothelial cells with HDL, mature miR-223 levels are significantly increased in endothelial cells and decreased on HDL. However, miR-223 is not transcribed in endothelial cells and is not increased in cells treated with HDL from miR-223−/− mice. HDL inhibit ICAM-1 protein levels, but not in cells pretreated with miR-223 inhibitors. ICAM-1 is a direct target of HDL-transferred miR-223 and this is the first example of an extracellular miRNA regulating gene expression in cells where it is not transcribed. Collectively, we demonstrate that HDL’s anti-inflammatory properties are conferred, in part, through HDL-miR-223 delivery and translational repression of ICAM-1 in endothelial cells

Nouveaux polyamphiphiles cationiques (synthèse et étude de leur organisation en milieu aqueux et aux interfaces en relation avec leur structure)

Dans le but d approfondir les connaissances fondamentales entre la structure des polymères associatifs intramoléculaires (polysavons) et leurs propriétés physico-chimiques en milieux aqueux, trois nouvelles familles de polymères amphiphiles cationiques ont été synthétisées par deux méthodes complémentaires permettant une grande variabilité de structure. Les polymères obtenus sont des poly(méth)acrylamides en peigne avec des groupes latéraux de type ammonium quaternaire portant une chaîne alkyle de taille variable. Une étude du comportement physico-chimique de ces polymères en solution, par viscosimétrie et spectroscopie de fluorescence avec deux sondes aux caractéristiques complémentaires, montre qu ils présentent des propriétés de polysavons qui varient progressivement avec la structure des polymères amphiphiles étudiés, notamment la longueur de la chaîne alkyle latérale, la taille de l espaceur entre les deux sites polaires amide et ammonium quaternaire et la masse molaire moyenne en nombre. En parallèle, la tensiométrie a montré que ces polyamphiphiles ont une très faible activité à l interface eau/air confirmant la prédominance de l effet hydrophobe, alors que les modèles moléculaires correspondants présentent d excellentes propriétés tensio-actives. Des films de Langmuir ont ensuite été réalisés dans le cadre de la première étude de cette importance sur des polyamphiphiles cationiques. Dans ce domaine également, la grande variabilité de structure des polymères a permis des observations originales et de dégager de nouvelles relations entre la structure du polymère et les caractéristiques des isothermes de compression obtenuesIn order to improve the fundamental knowledge of the relationships between the chemical structure of intramolecular associative polymers (polysoaps) and their physical chemical properties in aqueous media, three new families of cationic amphiphilic polymers were obtained by complementary methods offering great structure variability. The corresponding polymers were comb poly(meth)acrylamides with pendant ammonium groups with alkyl side chains of variable lengths. A first investigation of their physical chemical behaviour in aqueous solutions, by viscometry and fluorescence spectrometry with two complementary fluorescent probes, showed that they displayed polysoap properties which varied progressively with their chemical features, in particular the length of the alkyl side chain, the size of the spacer between the two polar amide and ammonium groups and the polymer molecular weight. Tensiometry confirmed the prevailing of the hydrophobic effect by showing that these polymers displayed a very weak activity at the water/air interface although the corresponding molecular models showed excellent tensio-active properties. Langmuir s films were eventually obtained in the first study of this importance on cationic amphiphilic polymers. Here again, the great structural variability enabled original observations and new structure/properties relationships were obtained for the corresponding compression isothermsNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

Contribution à l’étude de la germination et de la conservation des graines d’Argania spinosa (L.) Skeels de la région de Tindouf (Algérie)

A contribution to the study of the germination and conservation of Argania spinosa (L.) Skeels seeds in Tindouf area (Algeria). Argan seeds easily lose their germination capacity during storage. The fragility of these seeds is probably due to their content of oil of which oxidation products are toxic to the embryo. This study aims at testing germinal capacity and understanding the biochemical changes causing its loss during storage of Argan seeds coming from the natural population of the Tindouf region (Algeria). The evolution of the fatty acid content and the accumulation of malondialdehyde during seeds storage at ambient conditions and low temperature (+ 4 ° C) was followed. The overall results showed a high germination rate (92 %) of freshly harvested seeds as well as a significant loss of germination capacity after three years of seeds stored whatever the storage conditions are. This loss of germinal capacity is strongly related to a decrease in polyunsaturated fatty acid content and to a significant accumulation of malondialdehyde. However when seeds were stored in cold conditions (+ 4 ° C) the loss of germinal capacity and the accumulation of malondialdehyde were less than for seeds stored under ambient conditions. Cold would therefore limit the loss of germinal capacity by reducing the lipid peroxidation of Argan seed reserves.Les graines d’Arganier perdent rapidement leur faculté germinative lors de la conservation. La fragilité des graines est probablement due à leur richesse en huile dont les produits d’oxydation seraient toxiques pour l’embryon . L'objectif de la présente étude est de tester la capacité germinative des graines et à comprendre les changements biochimiques provoquant sa perte lors de la conservation de graines. Les graines étudiées provenaient du peuplement naturel de la région de Tindouf (Algérie). L’évolution de la faculté germinative, de la teneur en acides gras et en malondialdehyde a été suivie durant la conservation des graines dans des conditions ambiantes et à basse température. Les résultats ont révélé que les graines fraîchement récoltées présentent un taux de germination élevé (92 %). Après trois ans de conservation, une perte significative de la capacité de germination a été observée. Cette perte est fortement corrélée à une diminution de la teneur en acide gras polyinsaturées et à une importante accumulation en malondialdéhyde. Par contre, les graines d’Arganier stockées à basses températures (4 ° C) présentent des baisses du pouvoir germinatif plus faibles et une accumulation du malondialdéhyde moins importante que les graines stockées dans des conditions ambiantes. Le froid permet de limiter la peroxydation des lipides ainsi que la perte de la faculté germinative et la détérioration des graines d’Arganier .Berka Souhila, Hacene Hocine, Taguemount Djamel, Tabet Mohamed, Aïd Fatiha. Contribution à l’étude de la germination et de la conservation des graines d’Argania spinosa (L.) Skeels de la région de Tindouf (Algérie). In: Revue d'Écologie (La Terre et La Vie), tome 73, n°3, 2018. pp. 309-317

High-Density Lipoprotein-Associated miR-223 Is Altered after Diet-Induced Weight Loss in Overweight and Obese Males.

microRNAs (miRNAs) are small, endogenous non-coding RNAs that regulate metabolic processes, including obesity. The levels of circulating miRNAs are affected by metabolic changes in obesity, as well as in diet-induced weight loss. Circulating miRNAs are transported by high-density lipoproteins (HDL) but the regulation of HDL-associated miRNAs after diet-induced weight loss has not been studied. We aim to determine if HDL-associated miR-16, miR-17, miR-126, miR-222 and miR-223 levels are altered by diet-induced weight loss in overweight and obese males.HDL were isolated from 47 subjects following 12 weeks weight loss comparing a high protein diet (HP, 30% of energy) with a normal protein diet (NP, 20% of energy). HDL-associated miRNAs (miR-16, miR-17, miR-126, miR-222 and miR-223) at baseline and after 12 weeks of weight loss were quantified by TaqMan miRNA assays. HDL particle sizes were determined by non-denaturing polyacrylamide gradient gel electrophoresis. Serum concentrations of human HDL constituents were measured immunoturbidometrically or enzymatically.miR-16, miR-17, miR-126, miR-222 and miR-223 were present on HDL from overweight and obese subjects at baseline and after 12 weeks of the HP and NP weight loss diets. The HP diet induced a significant decrease in HDL-associated miR-223 levels (p = 0.015), which positively correlated with changes in body weight (r = 0.488, p = 0.032). Changes in miR-223 levels were not associated to changes in HDL composition or size.HDL-associated miR-223 levels are significantly decreased after HP diet-induced weight loss in overweight and obese males. This is the first study reporting changes in HDL-associated miRNA levels with diet-induced weight loss

High-Density Lipoprotein-Associated miR-223 Is Altered after Diet-Induced Weight Loss in Overweight and Obese Males.

microRNAs (miRNAs) are small, endogenous non-coding RNAs that regulate metabolic processes, including obesity. The levels of circulating miRNAs are affected by metabolic changes in obesity, as well as in diet-induced weight loss. Circulating miRNAs are transported by high-density lipoproteins (HDL) but the regulation of HDL-associated miRNAs after diet-induced weight loss has not been studied. We aim to determine if HDL-associated miR-16, miR-17, miR-126, miR-222 and miR-223 levels are altered by diet-induced weight loss in overweight and obese males.HDL were isolated from 47 subjects following 12 weeks weight loss comparing a high protein diet (HP, 30% of energy) with a normal protein diet (NP, 20% of energy). HDL-associated miRNAs (miR-16, miR-17, miR-126, miR-222 and miR-223) at baseline and after 12 weeks of weight loss were quantified by TaqMan miRNA assays. HDL particle sizes were determined by non-denaturing polyacrylamide gradient gel electrophoresis. Serum concentrations of human HDL constituents were measured immunoturbidometrically or enzymatically.miR-16, miR-17, miR-126, miR-222 and miR-223 were present on HDL from overweight and obese subjects at baseline and after 12 weeks of the HP and NP weight loss diets. The HP diet induced a significant decrease in HDL-associated miR-223 levels (p = 0.015), which positively correlated with changes in body weight (r = 0.488, p = 0.032). Changes in miR-223 levels were not associated to changes in HDL composition or size.HDL-associated miR-223 levels are significantly decreased after HP diet-induced weight loss in overweight and obese males. This is the first study reporting changes in HDL-associated miRNA levels with diet-induced weight loss