Browsing by Subject "SIRT1"

Now showing 1 - 4 of 4
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    Decreased SIRT1 Activity Is Involved in the Acute Injury Response of Chondrocytes to Ex Vivo Injurious Mechanical Overload
    (MDPI, 2023-03-30) Karnik, Sonali; Noori-Dokht, Hessam; Williams, Taylor; Joukar, Amin; Trippel, Stephen B.; Sankar, Uma; Wagner, Diane R; Mechanical and Energy Engineering, School of Engineering and Technology
    A better understanding of molecular events following cartilage injury is required to develop treatments that prevent or delay the onset of trauma-induced osteoarthritis. In this study, alterations to SIRT1 activity in bovine articular cartilage explants were evaluated in the 24 h following a mechanical overload, and the effect of pharmacological SIRT1 activator SRT1720 on acute chondrocyte injury was assessed. SIRT1 enzymatic activity decreased as early as 5 min following the mechanical overload, and remained suppressed for at least 24 h. The chondrocyte injury response, including apoptosis, oxidative stress, secretion of inflammatory mediators, and alterations in cartilage matrix expression, was prevented with pharmacological activation of SIRT1 in a dose-dependent manner. Overall, the results implicate SIRT1 deactivation as a key molecular event in chondrocyte injury following a mechanical impact overload. As decreased SIRT1 signaling is associated with advanced age, these findings suggest that downregulated SIRT1 activity may be common to both age-related and injury-induced osteoarthritis.
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    Irradiated riboflavin over nonradiated one: Potent antimigratory, antiproliferative and cytotoxic effects on glioblastoma cells
    (Wiley, 2024) Kacar, Sedat; Hacioglu, Ceyhan; Kar, Fatih; Surgery, School of Medicine
    Riboflavin is a water-soluble yellowish vitamin and is controversial regarding its effect on tumour cells. Riboflavin is a powerful photosensitizer that upon exposure to radiation, undergoes an intersystem conversion with molecular oxygen, leading to the production of ROS. In the current study, we sought to ascertain the impact of irradiated riboflavin on C6 glioblastoma cells regarding proliferation, cell death, oxidative stress and migration. First, we compared the proliferative behaviour of cells following nonradiated and radiated riboflavin. Next, we performed apoptotic assays including Annexin V and caspase 3, 7 and 9 assays. Then we checked on oxidative stress and status by flow cytometry and ELISA kits. Finally, we examined inflammatory change and levels of MMP2 and SIRT1 proteins. We caught a clear antiproliferative and cytotoxic effect of irradiated riboflavin compared to nonradiated one. Therefore, we proceeded with our experiments using radiated riboflavin. In all apoptotic assays, we observed a dose-dependent increase. Additionally, the levels of oxidants were found to increase, while antioxidant levels decreased following riboflavin treatment. In the inflammation analysis, we observed elevated levels of both pro-inflammatory and anti-inflammatory cytokines. Additionally, after treatment, we observed reduced levels of MMP2 and SIRT. In conclusion, radiated riboflavin clearly demonstrates superior antiproliferative and apoptotic effects on C6 cells at lower doses compared to nonradiated riboflavin.
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    Mismatch repair proteins recruit DNA methyltransferase 1 to sites of oxidative DNA damage
    (Oxford University Press, 2016-06) Ding, Ning; Bonham, Emily M.; Hannon, Brooke E.; Amick, Thomas R.; Baylin, Stephen B.; O'Hagan, Heather M.; Medical and Molecular Genetics, School of Medicine
    At sites of chronic inflammation, epithelial cells are exposed to high levels of reactive oxygen species and undergo cancer-associated DNA methylation changes, suggesting that inflammation may initiate epigenetic alterations. Previously, we demonstrated that oxidative damage causes epigenetic silencing proteins to become part of a large complex that is localized to GC-rich regions of the genome, including promoter CpG islands that are epigenetically silenced in cancer. However, whether these proteins were recruited directly to damaged DNA or during the DNA repair process was unknown. Here we demonstrate that the mismatch repair protein heterodimer MSH2-MSH6 participates in the oxidative damage-induced recruitment of DNA methyltransferase 1 (DNMT1) to chromatin. Hydrogen peroxide treatment induces the interaction of MSH2-MSH6 with DNMT1, suggesting that the recruitment is through a protein–protein interaction. Importantly, the reduction in transcription for genes with CpG island-containing promoters caused by oxidative damage is abrogated by knockdown of MSH6 and/or DNMT1. Our findings provide evidence that the role of DNMT1 at sites of oxidative damage is to reduce transcription, potentially preventing transcription from interfering with the repair process. This study uniquely brings together several factors that are known to contribute to colon cancer, namely inflammation, mismatch repair proteins, and epigenetic changes.
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    SIRT1 DEFICIENCY COMPROMISES MOUSE EMBRYONIC STEM CELL DIFFERENTIATION, AND EMBRYONIC AND ADULT HEMATOPOIESIS IN THE MOUSE
    (2011-03-16) Ou, Xuan; Broxmeyer, Hal E.; Pelus, Louis; Roman, Ann; Yoder, Mervin C.
    SIRT1 (Sirtuin 1) is a founding member of a family of seven proteins and histone deacetylases. It is involved in cellular resistance to stress, metabolism, differentiation, aging, and tumor suppression. SIRT1-/- mice demonstrate embryonic and postnatal development defects. We examined hematopoietic and endothelial cell differentiation of SIRT1-/- mouse embryonic stem (mES) cells in vitro, and hematopoietic progenitors in SIRT1+/+, SIRT1+/-, and SIRT1-/- mice. SIRT1-/- ES cells exhibited markedly delayed/immature formation of blast colony-forming cells (BL-CFCs). When individual blast colonies were analyzed for hematopoietic and endothelial potential, replated SIRT1-/- BL-CFC possessed limited hematopoietic potential, whereas endothelial potential was essentially unaltered. The ability of SIRT1-/- ES cells to form primitive erythroid progenitors was not only delayed but greatly decreased. Moreover, after differentiation of SIRT1-/- mES cells, there were also significant decreases in granulocyte-macrophage (CFU-GM) and multipotential (CFU-GEMM) progenitor cells. Differentiation delay/defects were associated with delayed capacity to switch off Oct4, Nanog and Fgf5, decreased β-H1 globin, β-major globin, and Scl gene expression and reduced activation of the Erk1/2 pathway upon SIRT1-/- ES cell commitment. Reintroduction of WT SIRT1 into SIRT1-/- cells partially rescued the primitive erythroid progenitor formation of SIRT1-/- cells and the expression of hemoglobin genes, Hbb-bh1 and Hbb-b1, suggesting that the defect of hematopoietic commitment is due to deletion of SIRT1, and not to genetic drifting of SIRT1-/- cells. To confirm the requirement for SIRT1 for normal development of hematopoietic progenitor cells, we assessed embryonic and adult hematopoiesis in SIRT1+/+, SIRT1+/- and SIRT1-/- mice. Yolk sacs from SIRT1 mutant embryos generated fewer primitive erythroid precursors compared to wild-type (WT) and heterozygous mice. Moreover, knockout of SIRT1 decreased primary bone marrow hematopoietic progenitor cells (HPCs) in 5 week and 12 month old mice, which was especially notable at lower (5%) O2 tension. In addition these progenitors survived less well in vitro under conditions of delayed growth factor addition. Taken together, these results demonstrate that SIRT1 plays a role in ES cell hematopoietic differentiation and mouse hematopoiesis.