EX 527 (SEN0014196)

EX 527 (SEN0014196) is a novel, potential, and specific small-molecule inhibitor of SIRT1 catalytic activity to examine the role of SIRT1 in p53 acetylation and cell survival after DNA damage. Significantly, inhibition of SIRT1 catalytic activity by EX 527 had no effect on cell growth, viability, or p53-controlled gene expression in cells treated with etoposide. EX-527 is found to be 200- to 500-fold more selective for SIRT1 than SIRT2 and SIRT3. EX-527 is a racemic mixture, and its optical isomers were separated by chiral high-performance liquid chromatography and designated EX-242 and EX-243.

Reference

Jonathan M. Solomon, Rao Pasupuleti, Lei Xu, Thomas McDonagh, Rory Curtis, Peter S. DiStefano, L. Julie Huber. Inhibition of SIRT1 Catalytic Activity Increases p53 Acetylation but Does Not Alter Cell Survival following DNA Damage. Molecular Cellular Biology January 2006 vol. 26 no. 1 28-38.

The protective effects of Resveratrol against radiation-induced intestinal injury.[Pubmed:28814292]

BMC Complement Altern Med. 2017 Aug 16;17(1):410.

BACKGROUND: Intestinal injury is a potential cause of death after high-dose radiation exposure. The aim of the present study was to investigate the protective effects of resveratrol against radiation-induced small intestine injury. METHODS: C57BL/6 N mice were irradiated and treated with resveratrol and/or Ex527 (a potent Sirt1 inhibitor), and subsequent examining intestinal morphological changes, and crypt cell apoptosis. Then, the expression and enzyme activity of SOD2 in the small intestine were examined. Furthermore, Sirt1 and acetylated p53 expression was analysed. RESULTS: Compared to the vehicle control, treatment with resveratrol improved intestinal morphology, decreased apoptosis of crypt cells, maintained cell regeneration, and ameliorated SOD2 expression and activity. Resveratrol also regulated Sirt1 and acetylated p53 expression perturbed by irradiation in the small intestine. The protective effect of resveratrol against ionizing radiation induced small intestine injury was significantly inhibited by Ex527. CONCLUSION: Our results suggest that resveratrol decreases the effects of radiation on intestinal injury at least partly via activation of Sirt1.

SIRT1 enzymatically potentiates 1,25-dihydroxyvitamin D3 signaling via vitamin D receptor deacetylation.[Pubmed:28636886]

J Steroid Biochem Mol Biol. 2017 Sep;172:117-129.

The hormonal metabolite of vitamin D, 1,25-dihydroxyvitamin D3 (1,25D), binds to the vitamin D receptor (VDR) and promotes heterodimerization of VDR with a retinoid-X-receptor (RXR) to genomically regulate diverse cellular processes. Herein, it is revealed for the first time that VDR is post-translationally acetylated, and that VDR immunoprecipitated from human embryonic kidney (HEK293) cells displays a dramatic decrease in acetylated receptor in the presence of 1,25D-ligand, sirtuin-1 (SIRT1) deacetylase, or the resveratrol activator of SIRT1. To elucidate the functional significance of VDR deacetylation, vitamin-d-responsive-element (VDRE)-based transcriptional assays were performed to determine if deacetylase overexpression affects VDR/VDRE-driven transcription. In HEK293 kidney and TE85 bone cells, co-transfection of low amounts (1-5ng) of a SIRT1-expression vector elicits a reproducible and statistically significant enhancement (1.3- to 2.6-fold) in transcription mediated by VDREs from the CYP3A4 and cyp24a1 genes, where the magnitude of response to 1,25D-ligand is 6- to 30-fold. Inhibition of SIRT1 via EX-527, or utilization of a SIRT1 loss-of-function mutant (H363Y), resulted in abrogation of SIRT1-mediated VDR potentiation. Studies with a novel, non-acetylatable VDR mutant (K413R) showed that the mutant VDR possesses enhanced responsiveness to 1,25D, in conjunction with reduced, but still significant, sensitivity to exogenous SIRT1, indicating that acetylation of lysine 413 is relevant, but that other acetylated residues in VDR contribute to modulation of its activity. We conclude that the acetylation of VDR comprises a negative feedback loop that attenuates 1,25D-VDR signaling. This regulatory loop is reversed by SIRT1-catalyzed deacetylation of VDR to amplify VDR signaling and 1,25D actions.

[Effect of lipopolysaccharides from Porphyromonas endodontalis on the expression of interleukin-34 in mouse osteoblasts].[Pubmed:28474064]

Shanghai Kou Qiang Yi Xue. 2017 Feb;26(1):37-41.

PURPOSE: To investigate the effects of lipopolysaccharides (LPS) extracted from Porphyromonas endodontalis (P.e) on the expression of interleukin-34 (IL-34) mRNA in MC3T3-E1 cells and the role of p38MAPK, ERK1/2, NF-kappaB and SIRT1 in the process. METHODS: MC3T3-E1 cells were treated with different concentrations of P.e-LPS(0-50 mg/L) and 20 mg/L P.e-LPS for different time (0-24 h). The expression of IL-34 mRNA was detected by real-time reverse transcription-polymerase chain reaction (real time RT-PCR). MC3T3-E1 cells were pretreated with inhibitor of NF-kappaB(BAY 11-7082),inhibitor of p38MAPK (SB203580), inhibitor of ERK1/2 (PD98059), agonist of sirtuin1 (SIRT1) [resveratrol (RES)] and inhibitor of SIRT1 (EX-527) for 1 h, and then were treated with 20 mg/L P.e-LPS. The expression of IL-34 mRNA was detected by real time RT-PCR. Statistical analysis was performed using one-way ANOVA and Dunnett t test with SPSS 13.0 software package. RESULTS: The level of IL-34 mRNA increased significantly after treatment with different concentrations of P.e-LPS(0-50 mg/L)which indicated that P.e-LPS induced osteoblasts to express IL-34 mRNA in a dose-dependent manner. Maximal induction of IL-34 mRNA expression was observed in MC3T3-E1 cells treated with 20 mg/L P.e-LPS for 24 h.At 48 h, the expression of IL-34 mRNA decreased gradually. The mRNA of IL-34 decreased significantly after pretreatment with 10 mumol/L BAY-117082, SB203580 and PD98059 for 1 h. P.e-LPS-induced IL-34 upregulation was attenuated by pretreatment with RES, but increased by EX-527. CONCLUSIONS: These results suggest that P.e-LPS may mediate IL-34 mRNA expression in MC3T3-E1 cells. This process is dependent, at least in part, on p38MAPK, ERK1/2, NF-kappaB and SIRT1 signaling pathways.

Astaxanthin attenuated pressure overload-induced cardiac dysfunction and myocardial fibrosis: Partially by activating SIRT1.[Pubmed:28300638]

Biochim Biophys Acta Gen Subj. 2017 Jul;1861(7):1715-1728.

BACKGROUND: Myocardial fibrosis contributes to cardiac dysfunction. Astaxanthin (AST), a member of the carotenoid family, is a well-known antioxidant, but its effect on and underlying mechanisms in myocardial fibrosis are poorly understood. METHODS: In vivo, myocardial fibrosis and cardiac dysfunction were induced using transverse aortic constriction (TAC). AST was administered to mice for 12weeks post-surgery. In vitro, transforming growth factor beta1 (TGF-beta1) was used to stimulate human cardiac fibroblasts (HCFs). EX-527 (6-chloro-2, 3, 4, 9-tetrahydro-1H-carbazole-1-carboxamide) and SIRT1 siRNA were used to inhibit SIRT1 in vivo and in vitro, respectively. The effects of AST on cardiac function and fibrosis were determined. SIRT1 expression and activity were measured to explore the mechanisms underlying its effects. RESULTS: AST improved cardiac function and attenuated fibrosis. Receptor activated-SMADs (R-SMADs), including SMAD2 and SMAD3, played important roles in these processes. The TAC surgery-induced increases in the expression of phosphorylated and acetylated R-SMADs were attenuated by treatment with AST, the translocation and transcriptional activity of R-SMADs were also restrained. These effects were accompanied by an increase in the expression and activity of SIRT1. Inhibiting SIRT1 attenuated the acetylation and transcriptional activity of R-SMADs, but not their phosphorylation and translocation. CONCLUSIONS: Our data demonstrate that AST improves cardiac function and attenuates fibrosis by decreasing phosphorylation and deacetylation of R-SMADs. SIRT1 contributes to AST's protective function by reducing acetylation of R-SMADs. GENERAL SIGNIFICANCE: These data suggest that AST may be useful as a preventive/therapeutic agent for cardiac dysfunction and myocardial fibrosis.

Berberine protects against ischemia/reperfusion injury after orthotopic liver transplantation via activating Sirt1/FoxO3alpha induced autophagy.[Pubmed:28077277]

Biochem Biophys Res Commun. 2017 Feb 5;483(2):885-891.

The effects and mechanism of berberine (BBR) on hepatic injury after orthotopic liver transplantation (OLT) have not been well characterized. We examined the role of Sirt1/FoxO3alpha axis in the protective effect of BBR on ischemia/reperfusion injury after OLT. Adult male Wistar rats were randomly allocated into four groups: Sham, OLT, OLT with BBR pretreatment (BBR), OLT with BBR and Sirt1 inhibitor (EX527) pretreatment group (EX527). The liver function and oxidative stress level were measured by biochemical and histopathologic examinations. The formation of autophagosome was observed by transmission electron microscopy. The apoptotic rate was determined by TUNEL analysis and the apoptotic mRNA expression. The expression of Sirt1, FoxO3alpha, Beclin-1, LC3-II/LC3-I, p62 and the acetylation of FoxO3alpha were assayed by western blot assay and immunoprecipitation. Compared with the OLT group, BBR dramatically attenuated the histopathologic damage, restored the liver function, and decreased the oxidative stress level. Simultaneously, BBR significantly ameliorated apoptosis by decreasing the apoptotic rate and the expression of apoptotic mRNA in rats subjected to OLT. The level of Beclin-1 and LC3-II/LC3-I were upregulated with the inhibition of p62. The deacetylation of FoxO3alpha by Sirt1 was enhanced in the nuclear of liver after pretreated with BBR. However, the inhibition of Sirt1 by EX527 counteracted the protective effects of BBR. Thus, BBR preconditioning promotes liver transplant ischemia/reperfusion injury partly via activating Sirt1/FoxO3alpha mediated autophagy.

The 2.5 A crystal structure of the SIRT1 catalytic domain bound to nicotinamide adenine dinucleotide (NAD+) and an indole (EX527 analogue) reveals a novel mechanism of histone deacetylase inhibition.[Pubmed:23311358]

J Med Chem. 2013 Feb 14;56(3):963-9.

The sirtuin SIRT1 is a NAD(+)-dependent histone deacetylase, a Sir2 family member, and one of seven human sirtuins. Sirtuins are conserved from archaea to mammals and regulate transcription, genome stability, longevity, and metabolism. SIRT1 regulates transcription via deacetylation of transcription factors such as PPARgamma, NFkappaB, and the tumor suppressor protein p53. EX527 (27) is a nanomolar SIRT1 inhibitor and a micromolar SIRT2 inhibitor. To elucidate the mechanism of SIRT inhibition by 27, we determined the 2.5 A crystal structure of the SIRT1 catalytic domain (residues 241-516) bound to NAD(+) and the 27 analogue compound 35. 35 binds deep in the catalytic cleft, displacing the NAD(+) nicotinamide and forcing the cofactor into an extended conformation. The extended NAD(+) conformation sterically prevents substrate binding. The SIRT1/NAD(+)/35 crystal structure defines a novel mechanism of histone deacetylase inhibition and provides a basis for understanding, and rationally improving, inhibition of this therapeutically important target by drug-like molecules.

Inhibition of SIRT1 catalytic activity increases p53 acetylation but does not alter cell survival following DNA damage.[Pubmed:16354677]

Mol Cell Biol. 2006 Jan;26(1):28-38.

Human SIRT1 is an enzyme that deacetylates the p53 tumor suppressor protein and has been suggested to modulate p53-dependent functions including DNA damage-induced cell death. In this report, we used EX-527, a novel, potent, and specific small-molecule inhibitor of SIRT1 catalytic activity to examine the role of SIRT1 in p53 acetylation and cell survival after DNA damage. Treatment with EX-527 dramatically increased acetylation at lysine 382 of p53 after different types of DNA damage in primary human mammary epithelial cells and several cell lines. Significantly, inhibition of SIRT1 catalytic activity by EX-527 had no effect on cell growth, viability, or p53-controlled gene expression in cells treated with etoposide. Acetyl-p53 was also increased by the histone deacetylase (HDAC) class I/II inhibitor trichostatin A (TSA). EX-527 and TSA acted synergistically to increase acetyl-p53 levels, confirming that p53 acetylation is regulated by both SIRT1 and HDACs. While TSA alone reduced cell survival after DNA damage, the combination of EX-527 and TSA had no further effect on cell viability and growth. These results show that, although SIRT1 deacetylates p53, this does not play a role in cell survival following DNA damage in certain cell lines and primary human mammary epithelial cells.

Discovery of indoles as potent and selective inhibitors of the deacetylase SIRT1.[Pubmed:16335928]

J Med Chem. 2005 Dec 15;48(25):8045-54.

High-throughput screening against the human sirtuin SIRT1 led to the discovery of a series of indoles as potent inhibitors that are selective for SIRT1 over other deacetylases and NAD-processing enzymes. The most potent compounds described herein inhibit SIRT1 with IC50 values of 60-100 nM, representing a 500-fold improvement over previously reported SIRT inhibitors. Preparation of enantiomerically pure indole derivatives allowed for their characterization in vitro and in vivo. Kinetic analyses suggest that these inhibitors bind after the release of nicotinamide from the enzyme and prevent the release of deacetylated peptide and O-acetyl-ADP-ribose, the products of enzyme-catalyzed deacetylation. These SIRT1 inhibitors are low molecular weight, cell-permeable, orally bioavailable, and metabolically stable. These compounds provide chemical tools to study the biology of SIRT1 and to explore therapeutic uses for SIRT1 inhibitors.