24 research outputs found
Stress oxydatif, fonction mitochondriale et maladie inflammatoire de l'intestin
CONTEXTE: Bien que la dysfunction mitochondriale et le stress oxydant jouent des rôles
prépondérants dans plusieurs conditions pathologiques, ils n’ont pas été étudiés de façon
extensive au niveau du tube digestif qui est constamment exposé aux oxydants (provenant
de l’alimentation) et à divers agents pathogènes. L’ingestion simultanée de sels ferreux et
d’acide ascorbique peut causer le dommage des macromolécules par oxydation. Le
‘’Nuclear factor erythroid 2 related factor’’ (Nrf2) est un important facteur de transcription
sensible au potentiel redox et qui protège contre le stress oxydant en induisant des gènes
anti-oxydants et de detoxification par sa liaison à l’élément de réponse antioxydante (ARE).
Les fonctions anti-oxydantes et anti-inflammatoires de Nrf2 ont été décrites dans une
variété de types cellulaires et de tissus. Cependant son rôle est très peu connu au niveau du
tube digestif. OBJECTIFS: Les objectifs sont d’évaluer comment la peroxydation
lipidique médiée par le fer/ascorbate (FE/ASC) affecte les fonctions mitochondriales dans
les cellules Caco-2/15, et de déterminer l’ampleur de l’implication de Nrf2.
MÉTHODES: Le stress oxydant a été induit dans les cellules Caco2/15 en les traitant
avec 0.2mm/2mm de FE/ASC. L’augmentation de l’expression de Nrf2 a été obtenue suite
au prétraitement des cellules Caco2/15 avec 50 μM d’Olitpraz (OPZ), un puissant
activateur. L’invalidation du gène de Nrf2 a été réalisée dans les cellules par transfection
avec un vecteur lentiviral contenant un shRNA contre Nrf2. RÉSULTATS: Nos
résultats montrent que le traitement des cellules Caco-2/15 avec du FE/ASC (0.2 mm/2
mm) augmente les niveaux du malondialdehyde (MDA), réduit la production d’ATP,
entraîne une surcharge mitochondriale de calcium, active l’expression protéique du
cytochrome C et de l’AIF (apoptotic inducing factor), réduit l’activité des complexes I, II,
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III et IV de la chaîne respiratoire mitochondriale, augmente les niveaux de 8-OHdG, un
marqueur des dommages à l’ADN mitochondrial, diminue la DNA glycosylase, et altère les
expressions génique et protéique des facteurs de transcription mitochondriaux (mtTFA,
mtTFB1, mtTFB2).
De plus, nos observations montrent que l’induction et l’activation de Nrf2 dans les cellules
Caco-2/15 résultent en: une augmentation des enzymes anti-oxydantes endogènes
(catalase, glutathion peroxydase, et superoxyde dismutase), une réduction du facteur
nucléaire NFκβ et de TNF-α, une augmentation de la production d’ ATP et de l’activité
des complexes respiratoires (I, II, III, IV) et de PGC-1α, et une régulation des niveaux de
la prohibitine mitochondriale, du Bcl-2 anti-apoptotique et de l’occludine.
CONCLUSION: Dans l’ensemble, nos résultats montrent que l’exposition aigüe des
cellules Caco-2/15 à la peroxydation par le FE/ASC entraîne des effets pathologiques sur
les fonctions mitochondriales et l’intégrité de l’ADN, qui sont abolis par l’induction de
Nrf2. Il en ressort que Nrf2 joue un rôle majeur dans la protection de l’épithélium intestinal
contre le stress oxydant.Background: Although mitochondrial dysfunction and oxidative stress are key mechanisms in various
pathological conditions, they have not been extensively studied in the gastrointestinal tract,
which is known to be constantly exposed to luminal oxidants from ingested foods and
pathogens. Key among these is the simultaneous ingestion of iron salts and ascorbic acid,
which can cause oxidative damage to macromolecules. The protein ‘’Nuclear factorerythroid
2- related factor’’ (Nrf2) is an important redox-sensitive transcription factor,
which protects against oxidative stress by inducing antioxidant and detoxifying genes
through binding with antioxidant response element (ARE). Many of Nrf2 antioxidant
protective and anti-inflammatory functions have been established in various cells and
tissues. However, limited information is available on its role in the gastrointestinal tract.
Objectives:
The objectives are to evaluate how iron-ascorbate (FE/ASC)-mediated lipid peroxidation
affects mitochondrion functioning in Caco-2/15 cells, and to mechanistically determine the
role of Nrf2.
Methods:
Caco2/15 cells were treated with 0.2mm/2mm of FE/ASC to induce oxidative stress. To
increase Nrf2 expression, cultured Caco2/15 cells were pre-treated with 50 μM Olitpraz
(OPZ). To down regulate the Nrf2 function, Nrf2 gene was knocked down by transfecting
Caco-2/15 cells with a pGFP-RS lentiviral vector containing shRNA against Nrf2.
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RESULTS:
Our results show that the treatment of Caco-2/15 cells with FE/ASC (0.2 mm/2 mm):
increased the levels of malondialdehyde (MDA), a marker of oxidative stress; reduced ATP
production; raised mitochondrial calcium content; regulated the protein expression of
cytochrome C and apoptotic inducing factor (AIF); decreased mitochondrial respiratory
chain complexes I, II, III and IV activity; prevented mtDNA damage as illustrated by the
raised levels of 8-OHdG; lowered DNA Glycosylase, and altered the gene expression and
protein mass of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2).
Furthermore, our observations indicate that the induction and activation of Nrf2 in
Caco2/15 cells resulted in an augmentated endogenous antioxidants enzymes (catalase,
glutathione peroxidase, and superoxide dismutase), a reduction of nuclear factor-kappaB
(NFκβ) and Tumor Necrosis Factor- Alpha (TNF-α), an increase in the ATP production,
mitochondrial respiratory complexes (I, II, III, VI), PGC1α , and a regulation of the
mitochondrial Prohibitin, anti-apoptotic Bcl-2 protein, and Occludin level.
CONCLUSION:
Findings indicate that acute exposure of Caco-2/15 cells to FE/ASC-catalyzed peroxidation
produces pathological effects on mitochondrial functions and DNA integrity, which were
diminished by Nrf2 induction. It appears that Nrf2 plays a critical cytoprotective role in
intestinal epithelial cells against oxidative stress
Oxidative Stress and Mitochondrial Functions in the Intestinal Caco-2/15 Cell Line
Although mitochondrial dysfunction and oxidative stress are central mechanisms in various pathological conditions, they have not been extensively studied in the gastrointestinal tract, which is known to be constantly exposed to luminal oxidants from ingested foods. Key among these is the simultaneous consumption of iron salts and ascorbic acid, which can cause oxidative damage to biomolecules.The objective of the present work was to evaluate how iron-ascorbate (FE/ASC)-mediated lipid peroxidation affects mitochondrion functioning in Caco-2/15 cells. Our results show that treatment of Caco-2/15 cells with FE/ASC (0.2 mM/2 mM) (1) increased malondialdehyde levels assessed by HPLC; (2) reduced ATP production noted by luminescence assay; (3) provoked dysregulation of mitochondrial calcium homeostasis as evidenced by confocal fluorescence microscopy; (4) upregulated the protein expression of cytochrome C and apoptotic inducing factor, indicating exaggerated apoptosis; (5) affected mitochondrial respiratory chain complexes I, II, III and IV; (6) elicited mtDNA lesions as illustrated by the raised levels of 8-OHdG; (7) lowered DNA glycosylase, one of the first lines of defense against 8-OHdG mutagenicity; and (8) altered the gene expression and protein mass of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2) without any effects on RNA Polymerase. The presence of the powerful antioxidant BHT (50 microM) prevented the occurrence of oxidative stress and most of the mitochondrial abnormalities.Collectively, our findings indicate that acute exposure of Caco-2/15 cells to FE/ASC-catalyzed peroxidation produces harmful effects on mitochondrial functions and DNA integrity, which are abrogated by the powerful exogenous BHT antioxidant. Functional derangements of mitochondria may have implications in oxidative stress-related disorders such as inflammatory bowel diseases
Fractional Analysis of Th2-Type Cytokines in Sequential Samples of Induced Sputum
BACKGROUND: Recent studies have demonstrated the usefulness of induced sputum in detecting the expression of Th2-type cytokines in asthmatics and have shown that the profile of inflammatory cells in induced sputum differs with time
Effects of Hydrofluoroalkane and Dry Powder-Formulated Corticosteroids on Sputum Inflammatory Markers in Asthmatic Patients
BACKGROUND: Inhaled corticosteroids are powerful drugs that can suppress airway inflammation in asthmatic patients. Deposition of most of the inhaled corticosteroid occurs mainly in the central airways. However, a new hydrofluoroalkane formulation of beclomethasone dipropionate (HFA-BDP) is preferentially deposited in the distal airways. Inflammatory characteristics of induced sputum have been shown to differ in samples collected early after sputum induction compared with later
Increased Alveolar and Plasma Gelatinases Activity during Postpump Syndrome: Inhibition by Inhaled Nitric Oxide
Article deposited with permission from the publisher (Wolters Kluwer) granted December 2, 2010.Ye