7,137 research outputs found

    Resveratrol mediated modulation of Sirt-1/Runx2 promotes osteogenic differentiation of mesenchymal stem cells: potential role of Runx2 deacetylation.

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    Osteogenic repair in response to bone injury is characterized by activation and differentiation of mesenchymal stem cells (MSCs) to osteoblasts. This study determined whether activation of Sirt-1 (a NAD(+)-dependent histone deacetylase) by the phytoestrogen resveratrol affects osteogenic differentiation. Monolayer and high-density cultures of MSCs and pre-osteoblastic cells were treated with an osteogenic induction medium with/without the Sirt-1 inhibitor nicotinamide or/and resveratrol in a concentration dependent manner. MSCs and pre-osteoblastic cells differentiated to osteoblasts when exposed to osteogenic-induction medium. The osteogenic response was blocked by nicotinamide, resulting in adipogenic differentiation and expression of the adipose transcription regulator PPAR-Îł (peroxisome proliferator-activated receptor). However, in nicotinamide-treated cultures, pre-treatment with resveratrol significantly enhanced osteogenesis by increasing expression of Runx2 (bone specific transcription factor) and decreasing expression of PPAR-Îł. Activation of Sirt-1 by resveratrol in MSCs increased its binding to PPAR-Îł and repressed PPAR-Îł activity by involving its cofactor NCoR (nuclear receptor co-repressor). The modulatory effects of resveratrol on nicotinamide-induced expression of PPAR-Îł and its cofactor NCoR were found to be mediated, at least in part, by Sirt-1/Runx2 association and deacetylation of Runx2. Finally, knockdown of Sirt-1 by using antisense oligonucleotides downregulated the expression of Sirt-1 protein and abolished the inhibitory effects of resveratrol, namely nicotinamide-induced Sirt-1 suppression and Runx2 acetylation, suggesting that the acetylated content of Runx2 is related to downregulated Sirt-1 expression. These data support a critical role for Runx2 acetylation/deacetylation during osteogenic differentiation in MSCs in vitro. (242 words in abstract)


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    Objective: Resveratrol, a trihydroxystilbene, has been claimed to be a potent activator to SIRT-1 enzyme activity, which in turn could have a useful future application in the management of many chronic conditions such as metabolic syndrome and obesity. A group of novel tetrahydroxystilbene derivatives were isolated from Kangaroo Island propolis in Australia. Due to its structural similarities with resveratrol, the aim of this research was to explore the activity of Kangaroo Island prenylated stilbenes on SIRT-1 enzyme.Methods: In vitro fluorometry measurement of SIRT-1 enzyme activity using SIRT-1 assay kit (Cayman¼).Results: None of the tested compounds had shown any activation to SIRT-1 enzyme, on contrary, they produced mild inhibition to the enzyme. Compound 3 (C20H22O4, 3,5,4'-trihydroxy-3'-methoxy-2-prenyl-E-stilbene) was the most potent inhibitor.Conclusion: Compound 3, in addition to compounds 2, 4, and 6 are candidate compounds for further investigation. A discussion of the results as well as the contradictory results in the literature has been presented in this article.Â

    Role of Sirtuin-1 in the pathogenesis of hypertension in spontaneously hypertensive rats : molecular mechanisms

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    Il a Ă©tĂ© dĂ©montrĂ© que la sirtuine 1 (Sirt-1), une histone dĂ©sacĂ©tylase de classe III, est surexprimĂ©e dans le coeur des rats spontanĂ©ment hypertendus (SHR). Nous avons rĂ©cemment montrĂ© que les cellules musculaires lisses vasculaires (CMLV) des SHR prĂ©sentent une expression accrue de Sirt-1 par rapport aux rats Wistar Kyoto (WKY) de mĂȘme Ăąge qui contribue Ă  l’augmentation de la rĂ©gulation de la protĂ©ine Giα impliquĂ©e dans la pathogenĂšse de l'hypertension. La prĂ©sente Ă©tude a Ă©tĂ© effectuĂ©e pour Ă©tudier le rĂŽle de l'augmentation de l'expression de la Sirt-1 dans la pathogenĂšse de l'hypertension chez les SHR et pour explorer les mĂ©canismes molĂ©culaires impliquĂ©s dans cette rĂ©ponse. Dans cette Ă©tude, un inhibiteur sĂ©lectif de la Sirt-1, EX-527 (5 mg/kg de poids corporel), a Ă©tĂ© injectĂ© par voie intrapĂ©ritonĂ©ale chez des rats SHR adultes de 8 semaines et des rats WKY de mĂȘme Ăąge, deux fois par semaine pendant 3 semaines. La pression artĂ©rielle (PA) et la frĂ©quence cardiaque ont Ă©tĂ© mesurĂ©es deux fois par semaine par la mĂ©thode non invasive du brassard autour de la queue. Le traitement avec l’inhibiteur spĂ©cifique de la Sirt-1, l'EX-527, a attĂ©nuĂ© les augmentations de PA (de 76 mmHg) et de frĂ©quence cardiaque chez les rats SHR. La surexpression de Sirt-1 et des protĂ©ines Giα dans le coeur, les CMLV et l'aorte a Ă©tĂ© attĂ©nuĂ©e au niveau des contrĂŽles par l'inhibiteur de la Sirt-1. L'inhibition de la Sirt-1 a Ă©galement attĂ©nuĂ© les niveaux accrus des anions superoxydes, l’activitĂ© de la NADPH oxydase et la surexpression des sous-unitĂ©s de la NADPH oxydase ; les protĂ©ines Nox2, Nox4 et P47phox dans les CMLV isolĂ©es des SHR traitĂ©s par l’EX-527. De plus, les niveaux rĂ©duits du monoxyde d'azote synthase endothĂ©lial (eNOS) et du monoxyde d'azote (NO) et les niveaux accrus de la peroxynitrite (ONOO-) dans les CMLV des SHR ont Ă©galement Ă©tĂ© rĂ©tablis Ă  des niveaux contrĂŽles par l'inhibiteur de la Sirt-1. Ces rĂ©sultats suggĂšrent que l'inhibition de la surexpression de la Sirt-1, en diminuant les niveaux accrus des protĂ©ines Giα et du stress nitro-oxydant, attĂ©nue la PA Ă©levĂ©e chez les rats SHR. Il est donc possible de suggĂ©rer que les inhibiteurs de la Sirt-1 puissent ĂȘtre utilisĂ©s comme des agents thĂ©rapeutiques dans le traitement des complications cardiovasculaires associĂ©es Ă  l'hypertension.Sirtuin-1 (Sirt-1), class III histone deacetylase, has been shown to be overexpressed in hearts from spontaneously hypertensive rats (SHR). We recently showed that vascular smooth muscle cells (VSMC) from SHR exhibit enhanced expression of Sirt-1 as compared to age-matched Wistar Kyoto (WKY) rats, which contributes to the upregulation of Giα protein implicated in the pathogenesis of hypertension. The present study was undertaken to investigate the role of upregulated Sirt-1 expression in the pathogenesis of hypertension in SHR and to explore the underlying molecular mechanisms involved in this response. For this study, a selective inhibitor of Sirt-1, EX-527 (5mg/kg of body weight), was injected intraperitoneally into 8-week-old adult SHR and age-matched WKY rats twice per week for 3 weeks. The blood pressure (BP) and heart rate was measured twice a week by the CODAℱ non-invasive tail cuff method. Treatment of SHR with Sirt-1-specific inhibitor, EX-527, attenuated high BP by 76 mmHg and inhibited the augmented heart rate. The overexpression of Sirt-1 and Giα proteins in heart, VSMC and aorta was attenuated to the control levels by Sirt-1 inhibitor. Inhibition of Sirt-1 also attenuated the enhanced levels of superoxide anion, NADPH oxidase activity and the overexpression of NADPH oxidase subunits; Nox2, Nox4 and P47phox proteins in VSMC isolated from EX-527-treated SHR. Furthermore, the decreased levels of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) and increased levels of peroxynitrite (ONOO-) in VSMC from SHR were also restored to control levels by Sirt-1 inhibitor. These results suggest that the inhibition of overexpression of Sirt-1 through decreasing the enhanced levels of Giα proteins and nitro-oxidative stress attenuates the high BP in SHR. It may thus be suggested that inhibitors of Sirt-1 may have the potential to be used as therapeutic agents in the treatment of cardiovascular complications associated with hypertension

    Human Sirt-1: Molecular Modeling and Structure-Function Relationships of an Unordered Protein

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    BACKGROUND: Sirt-1 is a NAD+-dependent nuclear deacetylase of 747 residues that in mammals is involved in various important metabolic pathways, such as glucose metabolism and insulin secretion, and often works on many different metabolic substrates as a multifunctional protein. Sirt-1 down-regulates p53 activity, rising lifespan, and cell survival; it also deacetylases peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and its coactivator 1 alpha (PGC-1alpha), promoting lipid mobilization, positively regulating insulin secretion, and increasing mitochondrial dimension and number. Therefore, it has been implicated in diseases such as diabetes and the metabolic syndrome and, also, in the mechanisms of longevity induced by calorie restriction. Its whole structure is not yet experimentally determined and the structural features of its allosteric site are unknown, and no information is known about the structural changes determined by the binding of its allosteric effectors. METHODOLOGY: In this study, we modelled the whole three-dimensional structure of Sirt-1 and that of its endogenous activator, the nuclear protein AROS. Moreover, we modelled the Sirt-1/AROS complex in order to study the structural basis of its activation and regulation. CONCLUSIONS: Amazingly, the structural data show that Sirt-1 is an unordered protein with a globular core and two large unordered structural regions at both termini, which play an important role in the protein-protein interaction. Moreover, we have found on Sirt-1 a conserved pharmacophore pocket of which we have discussed the implication

    Effects of niacin restriction on sirtuin and PARP responses to photodamage in human skin.

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    Sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs), NAD(+)-dependent enzymes, link cellular energy status with responses to environmental stresses. Skin is frequently exposed to the DNA damaging effects of UV irradiation, a known etiology in skin cancer. Thus, understanding the defense mechanisms in response to UV, including the role of SIRTs and PARPs, may be important in developing skin cancer prevention strategies. Here, we report expression of the seven SIRT family members in human skin. SIRTs gene expressions are progressively upregulated in A431 epidermoid carcinoma cells (SIRTs1 and 3), actinic keratoses (SIRTs 2, 3, 5, 6, and 7) and squamous cell carcinoma (SIRTs 1-7). Photodamage induces dynamic changes in SIRT expression with upregulation of both SIRT1 and SIRT4 mRNAs. Specific losses of SIRT proteins occur early after photodamage followed by accumulation later, especially for SIRT4. Niacin restriction, which decreases NAD(+), the sirtuin substrate, results in an increase in acetylated proteins, upregulation of SIRTs 2 and 4, increased inherent DNA damage, alterations in SIRT responses to photodamage, abrogation of PARP activation following photodamage, and increased sensitivity to photodamage that is completely reversed by repleting niacin. These data support the hypothesis that SIRTs and PARPs play important roles in resistance to photodamage and identify specific SIRTs that respond to photodamage and may be targets for skin cancer prevention

    Quantitative pretreatment VOI analysis of liver metastases 99mTc-MAA SPECT/CT and FDG PET/CT in relation with treatment response to SIRT

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    Using quantitive VOI analysis, the percentage Tc-99m-MAA uptake and SUVmax and mean values of liver metastases obtained prior to SIRT were related to treatment response using both a lesion-based and clinical dichotomous approach. Based on the VOI % of Tc-99m-MAA activity, the estimated Y-90-microspheres activity/cc (MBq/cc) was calculated from the effective dose injected. Baseline VOI FDG PET SUVmean and max values and estimated MBq/cc values were related to treatment response using a lesion-based approach (% change in SUVmean >= 50%) and a clinical dichotomous approach. Fifteen treatment sessions were analyzed (13 patients). Using the lesion-based approach (12 treatment sessions) 40 lesions responded and 37 did not. SUVmax and mean values proved significantly different between non-responding and responding lesions; 18:6 (SD 10.8) versus 13.5 (SD 8.4) for SUVmax (p = 0.02) and 11.4 (SD 3.8) versus 6.3 (SD 4.5) for SUVmean (p = 0.002). Using the clinical dichotomous approach (15 treatment sessions / 11 responding), 91 lesions were analyzed; 57 responded. VOI volumes and estimated Y-90-loaded glass microspheres activity (MBq/cc) did not differ between responders and non responders; 24 cc (SD 27) versus 21 cc (SD 21 cc) (p = 0.4) and 1.95 MBq/cc (SD 1.1 MBq/cc) versus 1.90 MB/cc (SD 2.7 MBq/cc) (p = 0.92). On the contrary, SUVmax and mean values proved significantly different between responders and non-responders; 23.7 (SD 9.8) versus 9.4 (SD 3.8) for SUVmax (p = 0.0001) and 13.1 (SD 8.1) versus 4.9 (SD 1.4) for SUVmean. Conclusion: These findings suggest that in patients presenting with high baseline SUVmax and mean values, the administration of higher activities or alternatively, other potentially more useful treatment options might be considered

    Quercetin prevents progression of disease in elastase/LPS-exposed mice by negatively regulating MMP expression

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    Abstract Background Chronic obstructive pulmonary disease (COPD) is characterized by chronic bronchitis, emphysema and irreversible airflow limitation. These changes are thought to be due to oxidative stress and an imbalance of proteases and antiproteases. Quercetin, a plant flavonoid, is a potent antioxidant and anti-inflammatory agent. We hypothesized that quercetin reduces lung inflammation and improves lung function in elastase/lipopolysaccharide (LPS)-exposed mice which show typical features of COPD, including airways inflammation, goblet cell metaplasia, and emphysema. Methods Mice treated with elastase and LPS once a week for 4 weeks were subsequently administered 0.5 mg of quercetin dihydrate or 50% propylene glycol (vehicle) by gavage for 10 days. Lungs were examined for elastance, oxidative stress, inflammation, and matrix metalloproteinase (MMP) activity. Effects of quercetin on MMP transcription and activity were examined in LPS-exposed murine macrophages. Results Quercetin-treated, elastase/LPS-exposed mice showed improved elastic recoil and decreased alveolar chord length compared to vehicle-treated controls. Quercetin-treated mice showed decreased levels of thiobarbituric acid reactive substances, a measure of lipid peroxidation caused by oxidative stress. Quercetin also reduced lung inflammation, goblet cell metaplasia, and mRNA expression of pro-inflammatory cytokines and muc5AC. Quercetin treatment decreased the expression and activity of MMP9 and MMP12 in vivo and in vitro, while increasing expression of the histone deacetylase Sirt-1 and suppressing MMP promoter H4 acetylation. Finally, co-treatment with the Sirt-1 inhibitor sirtinol blocked the effects of quercetin on the lung phenotype. Conclusions Quercetin prevents progression of emphysema in elastase/LPS-treated mice by reducing oxidative stress, lung inflammation and expression of MMP9 and MMP12.http://deepblue.lib.umich.edu/bitstream/2027.42/78260/1/1465-9921-11-131.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78260/2/1465-9921-11-131.pdfPeer Reviewe

    Pharmacological activation of endogenous protective pathways against oxidative stress under conditions of sepsis

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    Funding The study was funded entirely by institutional funds.Peer reviewedPostprin