Lessons from an estivating frog: sparing muscle protein despite starvation and disuse

Long (6- to 9-mo) bouts of estivation in green-striped burrowing frogs lead to 28% atrophy of cruralis oxidative fibers (P < 0.05) and some impairment of in vitro gastrocnemius endurance (P < 0.05) but no significant deficit in maximal twitch force production. These data suggest the preferential atrophy of oxidative fibers at a rate slower than, but comparable to, laboratory disuse models. We tested the hypothesis that the frog limits atrophy by modulating oxidative stress. We assayed various proteins at the transcript level and verified these results for antioxidant enzymes at the biochemical level. Transcript data for NADH ubiquinone oxidoreductase subunit 1 (71% downregulated, P < 0.05) and ATP synthase (67% downregulated, P < 0.05) are consistent with mitochondrial quiescence and reduced oxidant production. Meanwhile, uncoupling protein type 2 transcription (P < 0.31), which is thought to reduce mitochondrial leakage of reactive oxygen species, was maintained. Total antioxidant defense of water-soluble (22.3 +/- 1.7 and 23.8 +/- 1.5 mu M/mu g total protein in control and estivator, respectively, P = 0.53) and membrane-bound proteins (31.5 +/- 1.9 and 42.1 +/- 7.3 mu M/mu g total protein in control and estivator, respectively, P = 0.18) was maintained, equivalent to a bolstering of defense relative to oxygen insult. This probably decelerates muscle atrophy by preventing accumulation of oxidative damage in static protein reserves. Transcripts of the mitochondrially encoded antioxidant superoxide dismutase type 2 ( 67% downregulated, P < 0.05) paralleled mitochondrial activity, whereas nuclear-encoded catalase and glutathione peroxidase were maintained at control values (P = 0.42 and P = 0.231), suggesting a dissonance between mitochondrial and nuclear antioxidant expression. Pyruvate dehydrogenase kinase 4 transcription was fourfold lower in estivators (P = 0.11), implying that, in contrast to mammalian hibernators, this enzyme does not drive the combustion of lipids that helps spare hypometabolic muscle.

Effects of anitoxidant supplementation and exercise training on erythrocyte antioxidant enzymes

Erythrocytes transport oxygen to tissues and exercise-induced oxidative stress increases erythrocyte damage and turnover. Increased use of antioxidant supplements may alter protective erythrocyte antioxidant mechanisms during training. Aim of study: To examine the effects of antioxidant supplementation, (alpha-lipoic acid and a-tocopherol) and/or endurance training on the antioxidant defenses of erythrocytes. Methods: Young male Wistar rats were. assigned to (1) sedentary; (2) sedentary and antioxidant-supplemented; (3) endurance-trained; or (4) endurance-trained and antioxidant-supplemented groups for 14 weeks. Erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) activities, and plasma malondialdehyde (MDA) were then measured. Results: Antioxidant supplementation had no significant effect (p > 0.05) on activities of antioxidant enzymes in sedentary animals. Similarly, endurance training alone also bad no effect (p > 0.05). GPX (125.9 2.8 vs. 121.5 3.0 U.gHb(-1), p < 0.05) and CAT (6.1 0.2 vs. 5.6 0.2 U.mgHb-1, p < 0.05) activities were increased in supplemented trained animals compared to non-supplemented sedentary animals whereas SOD (61.8 4.3 vs. 52.0 5.2 U.mgHb(-1), p < 0.05) activity was decreased. Plasma MDA was not different among groups (p > 0.05). Conclusions: In a rat model, the combination of exercise training and antioxidant supplementation increased antioxidant enzyme activities (GPX, CAT) compared with each individual intervention.

The selective protection afforded by ebselen against lipid peroxidation in an ROS-dependent model of inflammation

The effects of an experimental model of hydrogen-peroxide-induced foot pad oedema on indices of oxidative damage to biomolecules have been investigated. We have demonstrated increased levels of fluorescent protein and lipid peroxides occurring in plasma at 24 and 48 h post-injection. In addition, a decrease in the degree of galactosylation of IgG was observed which kinetically related the degree of inflammation and to the increase in protein autofluorescence (a specific index of oxidative damage). The effects of ebselen, a novel organoselenium compound which protects against oxidative tissue injury in a glutathione-peroxidase-like manner, have also been examined in this model. Pretreatment of animals with a dose of 50 mg/kg ebselen afforded significant and selective protection against lipid peroxidation only. This effect may contribute to the anti-inflammatory effect of this agent in hydroperoxide-linked tissue damage.

Synthetic ceramides inhibit CD36 expression in U937 cells through a reduction in cytosolic peroxide

Ceramide (a sphingolipid) and reactive oxygen species (ROS) are each partly responsible for the intracellular signal transduction of a variety of physiological, pharmacological or environmental agents. It has been reported that synthesis of ceramide and ROS are intimately linked, and show reciprocal regulation. The levels of ceramide are reported to be elevated in atherosclerotic plaques providing circumstantial evidence for a pro-atherogenic role for ceramide. Indeed, LDL may be important sources of ceramide from sphingomyelin, where it promotes LDL aggregation. Using synthetic, short chain ceramides to mimic the cellular responses to fluctuations in natural endogenous ceramides, we have investigated ceramide effects on both intracellular redox state (as glutathione and ROS) and redox-sensitive gene expression, specifically the scavenger receptor CD36 (using RT-PCR and flow cytometry), in U937 monocytes and macrophages. We describe that the principal redox altering properties of ceramide are to lower cytosolic peroxide and to increase mitochondrial ROS formation, where growth arrest of U937 monocytes is also observed. In addition, cellular glutathione was depleted, which was independent of an increase in glutathione peroxidase activity. Examination of the effects of ceramide on stress induced CD36 expression in macrophages, revealed a dose dependent reduction in CD36 mRNA and protein levels, which was mimicked by N-acetyl cysteine. Taken together, these data suggest that ceramides differentially affect ROS within different cellular compartments, and that loss of cytosolic peroxide inhibits expression of the redox sensitive gene, CD36. This may attenuate both the uptake of oxidised LDL and the interaction of HDL with macrophages. The resulting sequelae in vivo remain to be determined.

An ideal ocular nutritional supplement?

The role of nutritional supplementation in prevention of onset or progression of ocular disease is of interest to health care professionals and patients. The aim of this review is to identify those antioxidants most appropriate for inclusion in an ideal ocular nutritional supplement, suitable for those with a family history of glaucoma, cataract, or age-related macular disease, or lifestyle factors predisposing onset of these conditions, such as smoking, poor nutritional status, or high levels of sunlight exposure. It would also be suitable for those with early stages of age-related ocular disease. Literature searches were carried out on Web of Science and PubMed for articles relating to the use of nutrients in ocular disease. Those highlighted for possible inclusion were vitamins A, B, C and E, carotenoids beta-carotene, lutein, and zeaxanthin, minerals selenium and zinc, and the herb, Ginkgo biloba. Conflicting evidence is presented for vitamins A and E in prevention of ocular disease; these vitamins have roles in the production of rhodopsin and prevention of lipid peroxidation respectively. B vitamins have been linked with a reduced risk of cataract and studies have provided evidence supporting a protective role of vitamin C in cataract prevention. Beta-carotene is active in the prevention of free radical formation, but has been linked with an increased risk of lung cancer in smokers. Improvements in visual function in patients with age-related macular disease have been noted with lutein and zeaxanthin supplementation. Selenium has been linked with a reduced risk of cataract and activates the antioxidant enzyme glutathione peroxidase, protecting cell membranes from oxidative damage while zinc, although an essential component of antioxidant enzymes, has been highlighted for risk of adverse effects. As well as reducing platelet aggregation and increasing vasodilation, Gingko biloba has been linked with improvements in pre-existing field damage in some patients with normal tension glaucoma. We advocate that vitamins C and E, and lutein/zeaxanthin should be included in our theoretically ideal ocular nutritional supplement.

Effects of oxidative stress and neuroprotection in apoptosis in neuronal cell models

The PC12 and SH-SY5Y cell models have been proposed as potentially realistic models to investigate neuronal cell toxicity. The effects of oxidative stress (OS) caused by both H2O2 and Aβ on both cell models were assessed by several methods. Cell toxicity was quantitated by measuring cell viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) viability assay, an indicator of the integrity of the electron transfer chain (ETC), and cell morphology by fluorescence and video microscopy, both of which showed OS to cause decreased viability and changes in morphology. Levels of intracellular peroxide production, and changes in glutathione and carbonyl levels were also assessed, which showed OS to cause increases in intracellular peroxide production, glutathione and carbonyl levels. Differentiated SH-SY5y cells were also employed and observed to exhibit the greatest sensitivity to toxicity. The neurotrophic factor, nerve growth factor (NGF) was shown to cause protection against OS. Cells pre-treated with NGF showed higher viability after OS, generally less apoptotic morphology, recorded less apoptotic nucleiods, generally lower levels of intracellular peroxides and changes in gene expression. The neutrophic factor, brain derived growth factor (BDNF) and ascorbic acid (AA) were also investigated. BDNF showed no specific neuroprotection, however the preliminary data does warrant further investigation. AA showed a 'janus face' showing either anti-oxidant action and neuroprotection or pro-oxidant action depending on the situation. Results showed that the toxic effects of compounds such as Aβ and H2O2 are cell type dependent, and that OS alters glutathione metabolism in neuronal cells. Following toxic insult, glutathione levels are depleted to low levels. It is herein suggested that this lowering triggers an adaptive response causing alterations in glutathione metabolism as assessed by evaluation of glutathione mRNA biosynthetic enzyme expression and the subsequent increase in glutathione peroxidase (GPX) levels.

Free radicals as potential antitumour agents

The aim of this work was to use extremely low concentrations of free radical generating compounds as a 'catalyst' to trigger endogenous free radical chain reactions in the host and to selectively eliminate neoplastic cells in the host. To test the hypothesis, a number of free radical generating compounds were screened on several malignant cell lines in vitro to select model compounds that were used against tumour models in vivo. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and its derivatives were selected at the model compounds for in vivo experiments in view of their high cytotoxic potency against several malignant cell lines in vitro. The water soluble derivative, 2,2-diphenyl-1-(2', 4'-dinitro-6'-sulphophenyl) hydrazyl (DDSH) given by subcutaneous injections demonstrated significant antitumour activities against the MAC 16 murine colon adenocarcinoma implanted subcutaneously in male NMRI mice at nanomolar concentration range. 40-60% of long term survival of over 60 days was achieved (compared with control survival of 20 days) with total tumour elimination. This compound was also active against both P388 leukaemia in male BDF1 mice and TLX5 lymphoid tumour in male CBA/CA mice at a similar concentration range. However, some of these animals died suddenly after treatment with no evidence of disease present at post mortem. The cause of death was unknown but thought to be related to the treatment. There was significant increase in serum level of malondialdehyde (MDA) following treatment, but did not correlate to the antitumour activities of these compounds. Induction of supcroxide dismutase (SOD), and glutathione peroxidase (GPx) occurred around day 8 after the administration of DDSH. Histological sections of MAC16 tumours showed areas of extensive massive haemorrhagic necrosis and vascular collapse associated with perivascular cell death following the administration of nanomolar concentration of DDSH which was probably compatible with the effects of free radicals. It was concluded that the antitumour activities of these compounds may be related to free radical and cytokine production.

Fatty acid composition, antioxidants and lipid oxidation in chicken breasts from different production regimes

Chicken breast from nine products and from the following production regimes: conventional (chilled and frozen), organic and free range, were analysed for fatty acid composition of total lipids, preventative and chain breaking antioxidant contents and lipid oxidation during 5 days of sub-ambient storage following purchase. Total lipids were extracted with an optimal amount of a cold chloroform methanol solvent. Lipid compositions varied, but there were differences between conventional and organic products in their contents of total polyunsaturated fatty acids and n-3 and n-6 fatty acids and n-6:n-3 ratio. Of the antioxidants, a-tocopherol content was inversely correlated with lipid oxidation. The antioxidant enzyme activities of catalase, glutathione peroxidase and glutathione reductase varied between products. Modelling with partial least squares regression showed no overall relationship between total antioxidants and lipid data, but certain individual antioxidants showed a relationship with specific lipid fractions.

Chemometric modelling to relate antioxidants, neutral lipid fatty acids and flavour components in chicken breast

Relationships among quality factors in retailed free-range, corn-fed, organic, and conventional chicken breasts (9) were modeled using chemometric approaches. Use of principal component analysis (PCA) to neutral lipid composition data explained the majority (93%) of variability (variance) in fatty acid contents in 2 significant multivariate factors. PCA explained 88 and 75% variance in 3 factors for, respectively, flame ionization detection (FID) and nitrogen phosphorus (NPD) components in chromatographic flavor data from cooked chicken after simultaneous distillation extraction. Relationships to tissue antioxidant contents were modeled. Partial least square regression (PLS2), interrelating total data matrices, provided no useful models. By using single antioxidants as Y variables in PLS (1), good models (r2 values > 0.9) were obtained for alpha-tocopherol, glutathione, catalase, glutathione peroxidase, and reductase and FID flavor components and among the variables total mono and polyunsaturated fatty acids and subsets of FID, and saturated fatty acid and NPD components. Alpha-tocopherol had a modest (r2 = 0.63) relationship with neutral lipid n-3 fatty acid content. Such factors thus relate to flavor development and quality in chicken breast meat.

Dapsone induces oxidative stress and impairs antioxidant defenses in rat liver

Dapsone (DDS) is currently used in the treatment of leprosy, malaria and in infections with Pneumocystis jirovecii and Toxoplasma gondii in AIDS patients. Adverse effects of DDS involve methemoglobinemia and hemolysis and, to a lower extent, liver damage, though the mechanism is poorly characterized. We evaluated the effect of DDS administration to male and female rats (30 mg/kg body wt, twice a day, for 4 days) on liver oxidative stress through assessment of biliary output and liver content of reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation, and expression/activities of the main antioxidant enzymes glutathione peroxidase, superoxide dismutase, catalase and glutathione S-transferase. The influence of DDS treatment on express ion/activity of the main DDS phase-II- metabolizing system, UDP-glucuronosyltransferase (UGT), was additionally evaluated. The involvement of dapsone hydroxylamine (DDS-NHOH) generation in these processes was estimated by comparing the data in male and female rats since N-hydroxylation of DDS mainly occurs in males. Our studies revealed an increase in the GSSG/GSH biliary output ratio, a sensitive indicator of oxidative stress, and in lipid peroxiclation, in male but not in female rats treated with DDS. The activity of all antioxidant enzymes was significantly impaired by DDS treatment also in male rats, whereas UGT activity was not affected in any sex. Taken together, the evidence indicates that DDS induces oxidative stress in rat liver and that N-hydroxylation of DDS was the likely mediator. Impairment in the activity of enzymatic antioxidant systems, also associated with DDS-NHOH formation, constituted a key aggravating factor.

Synthesis and Biological Evaluation of Novel Folic Acid Receptor-Targeted, β-Cyclodextrin-Based Drug Complexes for Cancer Treatment

Drug targeting is an active area of research and nano-scaled drug delivery systems hold tremendous potential for the treatment of neoplasms. In this study, a novel cyclodextrin (CD)-based nanoparticle drug delivery system has been assembled and characterized for the therapy of folate receptor-positive [FR(+)] cancer. Water-soluble folic acid (FA)-conjugated CD carriers (FACDs) were successfully synthesized and their structures were confirmed by 1D/2D nuclear magnetic resonance (NMR), matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS), high performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), and circular dichroism. Drug complexes of adamatane (Ada) and cytotoxic doxorubicin (Dox) with FACD were readily obtained by mixed solvent precipitation. The average size of FACD-Ada-Dox was 1.5–2.5 nm. The host-guest association constant Ka was 1,639 M−1 as determined by induced circular dichroism and the hydrophilicity of the FACDs was greatly enhanced compared to unmodified CD. Cellular uptake and FR binding competitive experiments demonstrated an efficient and preferentially targeted delivery of Dox into FR-positive tumor cells and a sustained drug release profile was seen in vitro. The delivery of Dox into FR(+) cancer cells via endocytosis was observed by confocal microscopy and drug uptake of the targeted nanoparticles was 8-fold greater than that of non-targeted drug complexes. Our docking results suggest that FA, FACD and FACD-Ada-Dox could bind human hedgehog interacting protein that contains a FR domain. Mouse cardiomyocytes as well as fibroblast treated with FACD-Ada-Dox had significantly lower levels of reactive oxygen species, with increased content of glutathione and glutathione peroxidase activity, indicating a reduced potential for Dox-induced cardiotoxicity. These results indicate that the targeted drug complex possesses high drug association and sustained drug release properties with good biocompatibility and physiological stability. The novel FA-conjugated β-CD based drug complex might be promising as an anti-tumor treatment for FR(+) cancer.

Selenium Distribution in the Human Retina

Selenium is known to occur in the enzyme, glutathione peroxidase, and plays an important role as an antioxidant. The objective of this investigation was to determine if amounts of selenium are selectively accumulated in different regions of the retina or uniformly distributed with eccentricity. 20 human retinas were analyzed for selenium. 18 of these were sectioned into a disc and two concentric annuli centered on the fovea using trephines having diameters of 3, 11, and 21 mm. The sections had areas of7.1, 93, and 343 mm2, respectively. Corresponding sections of these retinas were combined and analyzed together in sets of n = 5 and n = 11. For two donors, the whole retina of one eye was analyzed for selenium and the other retina was sectioned for analysis as described above. Selenium was determined using atomic fluorescence spectroscopy after digestion of the retinal tissues in nitric acid. The two whole retinas were found to have an average of 0.89 ± 0.49 pmoles/mm2 of selenium as compared to the companion which had 0.84 ± 0.28 pmoles/mm2 as determined from the sum of the selenium amounts measured in the individual sections. The inner, medial, and outer portions of these two sectioned retinas were found to contain an average of5.28 ± 1.1, 1.28 ± 0.44, 0.63 ± 0.22 pmoles/mm2, respectively. The five retinas that were sectioned and pooled for analysis were found to have average amounts of3.64, 1.26, and 0.56 pmoles/mm2 • The 11-sectioned retinas were found to have 1.16, 0.61, and 0.38 pmoles/mm2 respectively in the same three sections. This limited data set indicates that selenium is not uniformly distributed within the human retina but rather concentrated to a greater extent within the macula. If confirmed, these data would support the hypothesis that selenium may be an important antioxidant involved in protection of the macula from radical oxidants.

Alterações hepáticas na expressão gênica e atividade da catalase e superóxido dimutase em ratos diabéticos induzidos por estreptozootocina

The correlation between the type 1 diabetes mellitus and oxidative stress have been described in several studies, however its underlying mechanisms are not fully elucidated. The present work aimed to evaluate the effects of four weeks of streptozootocin-induced (STZ) diabetes in the redox homeostasis of rat hepatocytes. Thus, the liver of male Wistar rats from control and diabetic groups were collected and the activity and expression of antioxidant enzymes, as well the main markers of oxidative stress and content of H2O2 in these tissues were measured. The diabetes induced the activity of superoxide dismutase (SOD) and the gene expression of its mitochondrial isoform, SOD2. However, the expression of SOD1, the cytoplasmic isoform, was reduced by this disease. The activity and expression of catalase (CAT), as well the expression of glutathione peroxidase 1 (GPX1) and peroxiredoxin 4 (PRX4) were drastically reduced in the hepatocytes of diabetics rats. Even with this debility in the peroxidases mRNA expression, the content of H2O2 was reduced in the liver of diabetics rats when compared to the control group. The diabetes caused an increase of lipid peroxidation and a decrease of protein thiol content, showing that this disease causes distinct oxidative effects in different cell biomolecules. Our results indicate that four week of diabetes induced by STZ is already enough to compromise the enzymatic antioxidant systems of the hepatocytes.

Efeitos da terapia fotodinâmica com aluminio – cloro ftalocianina sobre a peroxidação lipídica e produtos antioxidantes em tecidos inflamados animais

Photodynamic therapy (PDT) consists of a non-toxic photosensitizing agent (FS) administration followed by a laser source resulting in a sequence of photochemical and photobiological processes that generate reactive oxygen species (ROS) that damaging cells. The present work evaluated the effects of PDT nanoemulsion-aluminum chloride phthalocyanine (AlClFc) mediated on malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels, which represent indicators involved in oxidative stress and antioxidant defenses. For this purpose, this study used 120 female rats of the Rattus norvegicus species, Wistar race, divided into 5 groups: Healthy (H), with periodontal disease (PD), with periodontal disease and treatment with FS (F), with periodontal disease and treatment with the laser (L); and periodontal disease and treatment with PDT (FL). An experimental model for represent periodontal disease (PD) was induced by ligature (split-mouth). Seven days later the induction of PD, the treatments were instituted according to the groups. In the group treated with PDT was applied 40μl FS (5μM) followed by laser irradiation diode InGaAlP (660nm, 100J / cm2). The rats were sacrificed on the 7th and 28th day after treatment and tissue specimens were removed and subjected to histological, immunohistochemical methods and enzymatic colorimetric measurements with detection by UV / VIS spectroscopy. Inflammatory changes, connective tissue disorganization and alveolar bone loss were displaying in groups with PD induced. The enzyme dosages showed that MDA levels were higher in PD induced groups, with no statistically significant differences (p> 0.05). High levels of GSH were found in groups L (p = 0.028) and FL (p = 0.028) compared with PD group, with statistically significant differences. Immunohistochemistry for SOD showed higher immunostaining in L and FL groups, compared to the PD group without statistically significant differences (p> 0.05). GPx showed lower immunoreactivity in the DP group when compared to the other groups and statistically significant differences were observed between the DPxL groups (p <0.05). TFD administered in this experiment did not induce elevation of MDA levels significantly increased the GSH levels and showed intense immunostaining pada SOD and GPx, showing that this therapy does not accentuated lipid peroxidation, however, it was able to induce effects on the antioxidant defenses processes. The LBI therapy appeared to show photomodulatory promoting effects reduction of the MDA levels, increasing GSH levels and with intense immunostaining for SOD and GPx, demonstrating that laser therapy induced antioxidant effects.

Régulation épigénétique de la défense antioxydante et de l'Angiopoietin-like 2 dans le contexte du vieillissement et des maladies cardiovasculaires

Suite à l’exposition à des facteurs de risque incluant la malnutrition, la dyslipidémie, la sédentarité et les désordres métaboliques, les maladies cardiovasculaires (MCV) sont caractérisées par un état pro-oxydant et pro-inflammatoire, et une dérégulation de l’expression de divers facteurs responsables de l’homéostasie de l’environnement rédox et inflammatoire. L’implication d’enzymes antioxydantes telles que les superoxyde dismutases (SOD) et les glutathion peroxydases (Gpx), ainsi que la contribution de médiateurs pro-inflammatoires tels que l’angiopoietin-like 2 (Angptl2) ont été rapportées dans le cadre des MCV. Toutefois, les mécanismes moléculaires sensibles aux facteurs de risque et menant au développement des MCV sont peu connus. L’épigénétique est un mécanisme de régulation de l’expression génique sensible aux stimuli extracellulaires et pourrait donc contribuer au développement des MCV. La méthylation de l’ADN est un des mécanismes épigénétiques pouvant varier tant de manière gène-spécifique qu’à l’échelle génomique, et la conséquence de tels changements sur l’expression des gènes ciblés dépend du site de méthylation. Puisqu’il a été démontré que des variations au niveau de la méthylation de l’ADN peuvent être associées à divers contextes pathologiques incluant les MCV, le but de nos travaux était d’étudier le lien entre la méthylation de gènes antioxydants et pro-inflammatoires avec leurs répercussions fonctionnelles biologiques en présence de facteurs de risques associés aux MCV, tels que le vieillissement, la dyslipidémie et la sédentarité. Dans la première étude, nous avons observé que dans l’artère fémorale de souris vieillissantes, la méthylation au niveau du promoteur du gène Sod2, codant pour l’enzyme antioxydante superoxyde dismutase de type 2 (SOD2 ou MnSOD), diminue avec l’âge. Ceci serait associé à l’induction de l’expression de MnSOD, renforçant ainsi la défense antioxydante endogène. Le vieillissement étant associé à une accumulation de la production de radicaux libres, nous avons étudié la vasodilatation dépendante de l’endothélium qui est sensible au stress oxydant. Nous avons observé que la capacité vasodilatatrice globale a été maintenue chez les souris âgées, aux dépens d’une diminution des facteurs hyperpolarisants dérivés de l’endothélium (EDHF) et d’une contribution accentuée de la voie du monoxyde d’azote (NO). Nous avons ensuite utilisé deux approches visant à réduire les niveaux de stress oxydant in vivo, soit la supplémentation avec un antioxydant, la catéchine, et l’exposition chronique à de l’exercice physique volontaire. Ces interventions ont permis de prévenir à la fois les changements au niveau de la fonction endothéliale et de l’hypométhylation de Sod2. Cette première étude démontre donc la sensibilité de la méthylation de l’ADN à l’environnement rédox. Dans la deuxième étude, nous avons démontré une régulation de l’expression de l’enzyme antioxydante glutathion peroxydase 1 (Gpx1) en lien avec la méthylation de son gène codant, Gpx1, dans un contexte de dyslipidémie sévère. Nos résultats démontrent que dans le muscle squelettique de souris transgéniques sévèrement dyslipidémiques (LDLr-/-; hApoB+/+), Gpx1 est hyperméthylé, ce qui diminue l’expression de Gpx1 et affaiblit la défense antioxydante endogène. Chez ces souris, l’exercice physique chronique a permis d’augmenter l’expression de Gpx1 en lien avec une hypométhylation transitoire de son gène. Cette étude démontre que le stress oxydant associé à la dyslipidémie sévère altère les mécanismes de défense antioxydante, en partie via un mécanisme épigénétique. De plus, on observe également que l’exercice physique permet de renverser ces effets et peut induire des changements épigénétiques, mais de manière transitoire. La troisième étude avait pour but d’étudier la régulation de l’Angptl2, une protéine circulante pro-inflammatoire, dans le contexte des MCV. Nous avons observé que chez des patients coronariens, la concentration circulante d’Angptl2 est significativement plus élevée que chez des sujets sains et ce, en lien avec une hypométhylation de son gène, ANGPTL2, mesurée dans les leucocytes circulants. Nous sommes les premiers à démontrer qu’en réponse à l’environnement pro-inflammatoire associé à une MCV, l’expression de l’Angptl2 est stimulée par un mécanisme épigénétique. Nos études ont permis d’identifier des nouvelles régions régulatrices différentiellement méthylées situées dans les gènes impliqués dans la défense antioxydante, soit Sod2 en lien avec le vieillissement et Gpx1 en lien avec la dyslipidémie et l’exercice. Nous avons également démontré un mécanisme de régulation de l’Angptl2 dépendant de la méthylation d’ANGPTL2 et ce, pour la première fois dans un contexte de MCV. Ces observations illustrent la nature dynamique de la régulation épigénétique par la méthylation de l’ADN en réponse aux stimuli environnementaux. Nos études contribuent ainsi à la compréhension et l’identification de mécanismes moléculaires impliqués dans le développement du phénotype pathologique suite à l’exposition aux facteurs de risque, ce qui ouvre la voie à de nouvelles approches thérapeutiques.