Dependent Protein Deacetylase Research Articles

Stabilization of P/CAF, as a ubiquitin ligase toward MDM2, suppresses mitotic cell death through p53-p21 activation in HCT116 cells with SIRT2 suppression

We previously reported that the suppression of SIRT2, an NAD + -dependent protein deacetylases, induces p53 accumulation via degradation of p300 and the subsequent MDM2 degradation, eventually leading to apoptosis in HeLa cells. The present study identified a novel pathway of p53 accumulation by SIRT2 suppression in HCT116(p53+/+) cells in which SIRT2 suppression led to escape from mitotic cell death caused by spindle assembly checkpoint activation induced by microtubule inhibitors such as nocodazole but not apoptosis or G1 or G2 arrest. We found that SIRT2 interacts with P/CAF, a histone acetyltransferase, which also acts as a ubiquitin ligase against MDM2. SIRT2 suppression led to an increase of P/CAF acetylation and its stabilization followed by a decrease in MDM2 and activation of the p53-p21 pathway. Depression of mitotic cell death in HCT116(p53+/+) cells with SIRT2 suppression was released by suppression of P/CAF or p21. Thus, the P/CAF-MDM2-p53-p21 axis enables the escape from mitotic cell death and confers resistance to nocodazole in HCT116(p53+/+) cells with SIRT2 suppression. As SIRT2 has attracted attention as a potential target for cancer therapeutics for p53 regulation, the present study provides a molecular basis for the efficacy of SIRT2 for future cancer therapy based on p53 regulation. These findings also suggest an undesirable function of the SIRT2 suppression associated with activation of the p53-p21 pathway in the suppression of mitotic cell death caused by spindle assembly checkpoint activation.

Sirtuin 2 Isoform 1 Enhances Hepatitis B Virus RNA Transcription and DNA Synthesis through the AKT/GSK-3β/β-Catenin Signaling Pathway.

Sirtuin 2 (Sirt2), a NAD+-dependent protein deacetylase, is overexpressed in many hepatocellular carcinomas (HCCs) and can deacetylate many proteins, including tubulins and AKT, prior to AKT activation. Here, we found that endogenous Sirt2 was upregulated in wild-type hepatitis B virus (HBV WT)-replicating cells, leading to tubulin deacetylation; however, this was not the case in HBV replication-deficient-mutant-transfected cells and 1.3-mer HBV WT-transfected and reverse transcriptase inhibitor (entecavir or lamivudine)-treated cells, but all HBV proteins were expressed. In HBV WT-replicating cells, upregulation of Sirt2 induced AKT activation, which consequently downregulated glycogen synthase kinase 3β (GSK-3β) and increased β-catenin levels; however, downregulation of Sirt2 in HBV-nonreplicating cells impaired AKT/GSK-3β/β-catenin signaling. Overexpression of Sirt2 isoform 1 stimulated HBV transcription and consequently HBV DNA synthesis, which in turn activated AKT and consequently increased β-catenin levels, possibly through physical interactions with Sirt2 and AKT. Knockdown of Sirt2 by short hairpin RNAs (shRNAs), inhibition by 2-cyano-3-[5-(2,5-dichlorophenyl)-2-furanyl]-N-5-quinolinyl-2-propenamide (AGK2), or dominant negative mutant expression inhibited HBV replication, reduced AKT activation, and decreased β-catenin levels. Through HBV infection, we demonstrated that Sirt2 knockdown inhibited HBV replication from transcription. Although HBx itself activates AKT and upregulates β-catenin, Sirt2-mediated signaling and upregulated HBV replication were HBx independent. Since constitutively active AKT inhibits HBV replication, the results suggest that upregulated Sirt2 and activated AKT may balance HBV replication to prolong viral replication, eventually leading to the development of HCC. Also, the results indicate that Sirt2 inhibition may be a new therapeutic option for controlling HBV infection and preventing HCC.IMPORTANCE Even though Sirt2, a NAD+-dependent protein deacetylase, is overexpressed in many HCCs, and overexpressed Sirt2 promotes hepatic fibrosis and associates positively with vascular invasion by primary HCCs through AKT/GSK-3β/β-catenin signaling, the relationship between Sirt2, HBV, HBx, and/or HBV-associated hepatocarcinogenesis is unclear. Here, we show that HBV DNA replication, not HBV expression, correlates positively with Sirt2 upregulation and AKT activation. We demonstrate that overexpression of Sirt2 further increases HBV replication, increases AKT activation, downregulates GSK-3β, and increases β-catenin levels. Conversely, inhibiting Sirt2 decreases HBV replication, reduces AKT activation, and decreases β-catenin levels. Although HBx activates AKT to upregulate β-catenin, Sirt2-mediated effects were not dependent on HBx. The results also indicate that a Sirt2 inhibitor may control HBV infection and prevent the development of hepatic fibrosis and HCC.

MicroRNAs in Skeletal Muscle Aging: Current Issues and Perspectives.

Skeletal muscle is one of the major organs responsible for body movements and metabolism making up approximately 40% of the total body mass. During aging, skeletal muscle exhibits a degenerative age-associated decline in mass and function termed sarcopenia. This age-associated dysfunction of skeletal muscle is a major criterion of morbidity, mortality, and overall declines of quality of life in the elderly people. Therefore, researchers have focused on identifying modulators of muscle aging process including messenger RNAs, proteins, and recently small noncoding RNAs such as microRNAs (miRNAs). In particular, miRNAs have been demonstrated to play a critical role in skeletal muscle development and homeostasis. Recent studies revealed that miRNAs were also involved in muscle aging processes and the rejuvenation of aged muscle by regulating important molecules and pathways of aging including insulin-like growth factors, nicotine-adenine dinucleotide (+)-dependent protein deacetylase sirtuin-1, telomerase reverse transcriptase, and transforming growth factor-β signaling pathway. Over the years, miRNAs have emerged as promising candidates for biomarkers of sarcopenia and targets for interventions to slow muscle aging. Here, we comprehensively review the current knowledge on the role of miRNAs in skeletal muscle aging and highlight their potential as biomarkers or therapeutic targets for skeletal muscle health.

Lysine benzoylation is a histone mark regulated by SIRT2

Metabolic regulation of histone marks is associated with diverse biological processes through dynamically modulating chromatin structure and functions. Here we report the identification and characterization of a histone mark, lysine benzoylation (Kbz). Our study identifies 22 Kbz sites on histones from HepG2 and RAW cells. This type of histone mark can be stimulated by sodium benzoate (SB), an FDA-approved drug and a widely used chemical food preservative, via generation of benzoyl CoA. By ChIP-seq and RNA-seq analysis, we demonstrate that histone Kbz marks are associated with gene expression and have physiological relevance distinct from histone acetylation. In addition, we demonstrate that SIRT2, a NAD+-dependent protein deacetylase, removes histone Kbz both in vitro and in vivo. This study therefore reveals a new type of histone marks with potential physiological relevance and identifies possible non-canonical functions of a widely used chemical food preservative.

SIRT3 Overexpression Inhibits Growth of Kidney Tumor Cells and Enhances Mitochondrial Biogenesis.

SIRT3 is a NAD+-dependent mitochondrial protein deacetylase implicated in the regulation of central metabolism and mitochondrial proteostasis. SIRT3 is downregulated in clear cell renal cell carcinoma (ccRCC), which is the most common form of renal cancer. Although ccRCC is characterized by a typical Warburg-like phenotype, mitochondrial dysfunction and elevated fat deposition, it is unknown whether SIRT3 plays a role in tumorigenesis and the development of this disease. In the present study, we found that SIRT3 overexpression and knockdown had opposing effects on the growth of ccRCC cells, decreasing and increasing the rate of cell proliferation, respectively. SIRT3 overexpression also increased mitochondrial mass in ccRCC cells. Unexpectedly, SIRT3 overexpression increased ROS levels, and sensitized cells to oxidative stress. Metabolomics and quantitative proteomics showed that SIRT3 overexpression alterd cellular metabolism and reversed the Warburg effect in ccRCC cells. Further studies demonstrated that SIRT3 promoted mitochondrial biogenesis by increasing both the expression and deacetylation of TFAM (transcription factor A, mitochondrial). Mutagenesis experiments revealed that acetylation of TFAM at K154 impaired TFAM interaction with mitochondrial DNA, thereby decreasing the activity of the protein and, consequently, mitochondrial biogenesis. Overall, our results suggest that SIRT3 regulates mitochondrial biogenesis and that its downregulation promotes a Warburg phenotype in ccRCC.

A novel small-molecule activator of Sirtuin-1 induces autophagic cell death/mitophagy as a potential therapeutic strategy in glioblastoma

Sirtuin-1 (SIRT1), the mammalian ortholog of yeast Sir2p, is well known to be a highly conserved NAD+-dependent protein deacetylase that has been emerging as a key cancer target. Autophagy, an evolutionarily conserved, multi-step lysosomal degradation process, has been implicated in cancer. Accumulating evidence has recently revealed that SIRT1 may act as a tumor suppressor in several types of cancer, and thus activating SIRT1 would represent a possible therapeutic strategy. Thus, in our study, we identified that SIRT1 was a key prognostic factor in brain cancer based upon The Cancer Genome Atlas and tissue microarray analyses. Subsequently, we screened a series of potential small-molecule activators of SIRT1 from Drugbank, and found the best candidate compound F0911-7667 (hereafter, named Comp 5), which showed a good deacetylase activity for SIRT1 rather than other Sirtuins. In addition, we demonstrated that Comp 5-induced autophagic cell death via the AMPK-mTOR-ULK complex in U87MG and T98G cells. Interestingly, Comp 5-induced mitophagy by the SIRT1–PINK1–Parkin pathway. Further iTRAQ-based proteomics analyses revealed that Comp 5 could induce autophagy/mitophagy by downregulating 14-3-3γ, catalase, profilin-1, and HSP90α. Moreover, we showed that Comp 5 had a therapeutic potential on glioblastoma (GBM) and induced autophagy/mitophagy by activating SIRT1 in vivo. Together, these results demonstrate a novel small-molecule activator of SIRT1 that induces autophagic cell death/mitophagy in GBM cells, which would be utilized to exploit this compound as a leading drug for future cancer therapy.

Remodeling of the Acetylproteome by SIRT3 Manipulation Fails to Affect Insulin Secretion or β Cell Metabolism in the Absence of Overnutrition

SUMMARYSIRT3 is a nicotinamide adenine dinucleotide (NAD+)- dependent mitochondrial protein deacetylase purported to influence metabolism through post-translational modification of metabolic enzymes. Fuel-stimulated insulin secretion, which involves mitochondrial metabolism, could be susceptible to SIRT3-mediated effects. We used CRISPR/Cas9 technology to manipulate SIRT3 expression in β cells, resulting in widespread SIRT3-dependent changes in acetylation of key metabolic enzymes but no appreciable changes in glucose- or pyruvate-stimulated insulin secretion or metabolomic profile during glucose stimulation. Moreover, these broad changes in the SIRT3-targeted acetylproteome did not affect responses to nutritional or ER stress. We also studied mice with global SIRT3 knockout fed either standard chow (STD) or high-fat and high-sucrose (HFHS) diets. Only when chronically fed HFHS diet do SIRT3 KO animals exhibit a modest reduction in insulin secretion. We conclude that broad changes in mitochondrial protein acetylation in response to manipulation of SIRT3 are not sufficient to cause changes in islet function or metabolism.

BK channel deacetylation by SIRT1 in dentate gyrus regulates anxiety and response to stress

Previous genomic studies in humans indicate that SIRT1, a nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylase, is involved in anxiety and depression, but the mechanisms are unclear. We previously showed that SIRT1 is highly activated in the nuclear fraction of the dentate gyrus of the chronically stressed animals and inhibits memory formation and increases anhedonic behavior during chronic stress, but specific functional targets of cytoplasmic SIRT1 are unknown. Here, we demonstrate that SIRT1 activity rapidly modulates intrinsic and synaptic properties of the dentate gyrus granule cells and anxiety behaviors through deacetylation of BK channel α subunits in control animals. Chronic stress decreases BKα channel membrane expression, and SIRT1 activity has no rapid effects on synaptic transmission or intrinsic properties in the chronically stressed animal. These results suggest SIRT1 activity rapidly modulates the physiological function of the dentate gyrus, and this modulation participates in the maladaptive stress response.

Activation of Sirtuin 1 Attenuates High Glucose-Induced Neuronal Apoptosis by Deacetylating p53.

Diabetes mellitus (DM) has been proven to be a key risk factor for cognitive impairment. Previous studies have implicated hippocampal neuronal apoptosis in diabetes-related cognitive impairment. However, the underlying mechanism remains unknown. Sirtuin 1 (SIRT1) is a protein deacetylase depended on nicotinamide adenine dinucleotide. Furthermore, it is indispensable in normal learning and memory. Whether SIRT1 is taken part in diabetes-induced neuronal apoptosis and thus involve in the development of diabetic cognitive impairment is still not clear. To address this issue, we examined the possible role of SIRT1 in hippocampal neuronal apoptosis in streptozotocin-induced diabetic mice. Furthermore, the possible mechanism was investigated in high glucose-induced SH-SY5Y cells. We found that downregulation of the activity and expression of SIRT1 was associated with increased hippocampal neuronal apoptosis in mice. In vitro, cell apoptosis induced by high glucose which was accompanied by a downregulation of SIRT1 and an increased acetylation of p53. On the contrary, activation of SIRT1 using its agonist resveratrol ameliorated cell apoptosis via deacetylating p53. Our data suggest that high concentration of glucose can induce neuronal apoptosis through downregulation of SIRT1 and increased acetylation of p53, which likely contribute to the development of cognitive impairment in diabetes.

Sirt3 deficiency impairs neurovascular recovery in ischemic stroke.

Sirt3 is one member of the NAD+ -dependent protein deacetylase family and plays crucial roles in diverse aspects of mammalian biological function. Then the role of Sirt3 on ischemia stroke is unknown. To examine the effect of Sirt3 on ischemic stroke, we performed transient middle cerebral artery occlusion (tMCAO) in adult male Sirt3 knockout (KO) and wild-type (WT) mice. The level of Sirt3 in infarct region is decreased after ischemic stroke. In addition, we found that Sirt3 KO mice showed worse neurobehavioral outcome compared with WT mice, accompanied by decreased neurogenesis and angiogenesis as shown by the reduction in number of DCX+ /BrdU+ cells, NeuN+ /BrdU+ cells, and CD31+ /BrdU+ cells in the perifocal region during recovery phase after ischemic stroke. Furthermore, Sirt3 deficiency reduced the activation of vascular endothelial growth factor (VEGF), AKT, and extracellular signal-regulated kinases (ERK) signaling pathways. Our results indicated that Sirt3 is beneficial to neurovascular and functional recovery following chronic ischemic stroke.

SphK1/S1P Axis Regulate PPARγ Levels to Program Metabolically Fit Anti-Tumor T Cells

Abstract Metabolic competition with highly glycolytic tumor and overcoming tumor-induced suppression are prerequisites for achieving prolonged tumor control by adoptive T cell therapy (ACT). Given the importance of sphingosine-1-phosphate (S1P) signaling that are independent of immune cell trafficking, we evaluated if altering sphingosine kinase (SphK) mediated S1P level have benefits for anti-tumor T cell response. A comparison of melanoma epitope gp100 reactive T cell receptor transgenic pMel vs. pMel-SphK1−/− mice derived splenic T cells showed better control of subcutaneously established murine B16-F10 melanoma, increased infiltration at the tumor site with activated pMel-SphK1−/− T cells. Additionally, pMel-Sphk1−/−T cells also exhibited enhanced recall response tracked in different organs after secondary antigen exposure. Mechanistically, we found that attenuation of SphK1/S1P signaling results in higher Sirt1 (an NAD+ dependent protein deacetylase) activity, lower PPARγ activity and higher retention of FOXO1 in the nucleus. While higher nuclear localization of FOXO1 regulates higher migration of SphK1−/− CD8+ T cells, lower PPARγ activity endows them with increased ability to use their stored lipid content even in starved condition and decreased iTreg generation. Owing to their efficacious utilization of lipid as fuel, Sphk1−/− T cells persist longer in nutrient deprived tumor microenvironment. In reciprocal studies, endogenous production of S1P in Sphk1−/− T cells (transfected with WT Sphk1 vector) enhanced PPARγ expression and thereby reversed their phenotype in terms of iTreg generation and lipid utilization. Overall, these data highlight that strategies targeting SphK/S1P axis improves efficacy of ACT.

MiR-373 exacerbates renal injury and fibrosis via NF-κB/MatrixMetalloproteinase-9 signaling by targeting Sirtuin1

BackgroundRenal fibrosis is a final common pathway of chronic kidney disease. SIRT1, a NAD+-dependent protein deacetylase, deacetylates the p65 of NF-κB and shows protective effects in kidney disorders. miR-373 directly targets the 3′UTR of SIRT1. However, roles of miR-373 in renal fibrosis are unclear. MethodsTGF-β1, a critical regulator of fibrosis, was used to stimulate human kidney-2 cells to establish cell model for renal fibrosis. Unilateral ureteral obstruction (UUO) was performed as an in vivo model. ResultsTGF-β1 induced the level of miR-373, reduced level of SIRT1, and promoted p65 acetylation and MMP-9 expression. These effects were reversed by the miR-373 inhibitor. In the animal model, UUO caused a consistent pattern as demonstrated in vitro. ConclusionThese results indicated an undesired effect of miR-373 in the regulation of renal injury and fibrosis by targeting SIRT1-mediated NF-κB/MMP-9 signaling, which might provide a potential therapeutic strategy for renal fibrosis.

High Basolateral Glucose Increases Sodium-Glucose Cotransporter 2 and Reduces Sirtuin-1 in Renal Tubules through Glucose Transporter-2 Detection

Under diabetic conditions, sodium–glucose cotransporter 2 (SGLT2) for glucose uptake in proximal tubules (PTs) increases, whereas NAD+-dependent protein deacetylase silent mating type information regulation 2 homolog 1 (Sirtuin-1; SIRT1) for PT survival decreases. Therefore, we hypothesized that increased glucose influx by SGLT2 reduces SIRT1 expression. To test this hypothesis, db/db mice with diabetes and high-glucose (HG)-cultured porcine PT LLC-PK1 cells in a two-chamber system were treated with the SGLT2 inhibitor canagliflozin. We also examined SIRT1 and SGLT2 expression in human kidney biopsies. In db/db mice, SGLT2 expression increased with concomitant decreases in SIRT1, but was inhibited by canagliflozin. For determination of the polarity of SGLT2 and SIRT1 expression, LLC-PK1 cells were seeded into Transwell chambers (pore size, 0.4 µm; Becton Dickinson, Oxford, UK). HG medium was added to either or to both of the upper and lower chambers, which corresponded to the apical and basolateral sides of the cells, respectively. In this system, the lower chamber with HG showed increased SGLT2 and decreased SIRT1 expression. Canagliflozin reversed HG-induced SIRT1 downregulation. Gene silencing and inhibitors for glucose transporter 2 (GLUT2) blocked HG-induced SGLT2 expression upregulation. Gene silencing for the hepatic nuclear factor-1α (HNF-1α), whose nuclear translocation was enhanced by HG, blocked HG-induced SGLT2 expression upregulation. Similarly, gene silencing for importin-α1, a chaperone protein bound to GLUT2, blocked HG-induced HNF-1α nuclear translocation and SGLT2 expression upregulation. In human kidney, SIRT1 immunostaining was negatively correlated with SGLT2 immunostaining. Thus, under diabetic conditions, SIRT1 expression in PTs was downregulated by an increase in SGLT2 expression, which was stimulated by basolateral HG through activation of the GLUT2/importin-α1/HNF-1α pathway.

1200 SIRT7 epigenetically regulates MITF to promote melanoma growth

Sirtuins comprise a family of NAD+-dependent protein deacetylases, among which SIRT6 and SIRT7 are exclusively located in nucleus and have attracted considerable attention for their great pathogenic importance in cancer. Our previous study has reported that aberrant SIRT6 expression contributed to melanoma growth by regulating AKT signaling and autophagy. However, whether another nucleus-located sirtuin SIRT7 is involved in melanoma development remains unknown. Herein, we first found that SIRT7 was significantly up-regulated in both melanoma tissues and cell lines, compared with melanocytic nevus and normal human melanocytes respectively. Moreover, the knockdown of SIRT7 led to impaired proliferative ability and colonigenic capacity of melanoma cells. Subsequently, we found that SIRT7 positively regulated MITF expression at the transcriptional level and the tumorigenic effect of SIRT7 was dependent on MITF pathway. Further mechanistic study showed that SIRT7 directly bond to promoters of the MITF locus and deacetylated H3K18Ac. Altogether, our results demonstrate that SIRT7 promotes melanoma growth by epigenetically regulating MITF.

Cdk5 suppression blocks SIRT1 degradation via the ubiquitin-proteasome pathway in Parkinson's disease models

The NAD+-dependent protein deacetylase sirtuin 1 (SIRT1), a member of the sirtuin family, may have a neuroprotective effect in multiple neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD) and Amyotrophic lateral sclerosis (ALS). Many studies have suggested that overexpression-induced or resveratrol-treated activation of SIRT1 could significantly ameliorate several neurodegenerative diseases in mouse models. However, the type of SIRT1, protein expression levels and underlying mechanisms remain unclear, especially in PD. In this study, the results demonstrated that SIRT1 knockout markedly worsened the movement function in MPTP-lesioned animal model of PD. SIRT1 expression was found to be markedly decreased not only in environmental factor PD models, neurotoxin MPP+-treated primary culture neurons and MPTP-induced mice but also in genetic factor PD models, overexpressed α-synuclein-A30PA53T SH-SY5Y stable cell line and hm2α-SYN-39 transgenic mouse strain. Importantly, the degradation of SIRT1 during MPP+ treatment was mediated by the ubiquitin-proteasome pathway. Furthermore, the results indicated that cyclin-dependent kinase 5 (Cdk5) was also involved in the decrease of SIRT1 expression, which could be efficiently blocked by the inhibition of Cdk5. In conclusion, our findings revealed that the Cdk5-dependent ubiquitin-proteasome pathway mediated degradation of SIRT1 plays a vital role in the progression of PD.

A novel SIRT1 activator E6155 improves insulin sensitivity in type 2 diabetic KKAy mice

Sirtuin 1 (SIRT1) is an NAD+-dependent protein deacetylase that plays a critical role in controlling energy metabolism, stress response and aging. Hence, enhancing SIRT1 activity could be a potential therapeutic strategy to treat metabolic diseases such as diabetes. However, pharmacological activators for SIRT1 are scarce to date. In this study, using the optimized high throughput screening, we identified E6155, a piperazine 1, 4- diamide compound, as a new small molecular activator of SIRT1. We further found that E6155 significantly upregulated glucose uptake in cultured normal liver cells and skeletal muscle cells through increasing SIRT1 deacetylase activity. In type 2 diabetic KKAy mice, E6155 treatment markedly decreased the level of fasting glucose. Moreover, E6155 improved oral glucose tolerance and insulin tolerance. Euglycemic clamp and the homeostasis model assessment of insulin resistance index showed that E6155 ameliorated the insulin resistance and increased insulin sensitivity in diabetic mice. Mechanistically, we observed that the antidiabetic effects of E6155 were involved in SIRT1 dependent activation of LKB1/AMPK and IRS1/AKT pathways. In conclusion, our findings identified E6155 as a novel SIRT1 activator and suggested that E6155 could be a promising drug candidate for treating insulin resistance and diabetes.

SA1/SA2 cohesion proteins and SIRT1-NAD+ deacetylase modulate telomere homeostasis in cumulus cells and are eligible biomarkers of ovarian aging.

Are cohesins SA1/SA2 and the NAD-dependent deacetylase SIRT1 involved in telomere homeostasis of cumulus cells and thus eligible as biomarkers of follicular physiology and ovarian aging? SA1/SA2 cohesins and SIRT1 are associated with telomere length in cumulus cells and may be eligible biomarkers of follicular physiology and ovarian aging. In somatic cells, cohesins SA1/SA2 mediate sister chromatid cohesion at the telomere termini (for SA1) and along chromatid arms (for SA2). The NAD+-dependent protein deacetylase Sirtuin 1 (SIRT1), which preserves DNA integrity from oxidative stress, may also modulate genome stability and telomere length. Collectively 280 cumulus/oocyte complex samples were recovered from a total of 50 women undergoing in vitro fertilization. Cumulus cells were separated from the oocyte-cumulus complex. DNA and total mRNA were extracted from cumulus cells and assayed for telomere length and for SA1, SA2 and SIRT1 gene expression profiling. Telomere length was determined by quantitave PCR and analyzed relative to the single copy of the housekeeping gene (albumin) to generate a T/S ratio (Telomere/single copy gene). Gene expression levels of SA1, SA2 and SIRT1 mRNA were assayed by quantitative RT-PCR and confirmed by western blotting and immunofluorescent studies (SIRT1). SA1/SA2 and SIRT1 gene expression levels and telomere length analysis of patients/samples were ranked in relation to their clinical setting parameters (BMI, age) and to the number of oocyte retrieved. SA1 and SA2 transcripts were both detected in all cumulus cells analyzed and the relative amount showed a clear decreasing trend according to the age of patients. A significant increase in SA1 and SA2 was disclosed in high responder women (>6 oocytes retrieved) compared to poor responders (<4 oocytes) (P < 0.05). Furthermore, statistically significant positive correlations were also recorded between the transcripts levels of the two cohesin molecules (r = 0.89; P < 0.05) and, to a lesser extent, between telomere length and SA1 (r = 0.42; P < 0.001) and SA2 (r = 0.36; P < 0.001) mRNA levels. SIRT1 expression was also significantly increased in high responders (>6 oocytes) compared to poor responders. Significant correlations were found between SIRT1 and SA1 (r = 0.69; P < 0.001), between SIRT1 and SA2 (r = 0.78; P < 0.001), and between SIRT1 and telomere length (r = 0.36; P < 0.001). However, in the older patient group (>38 years), SIRT1 mRNA levels were twice as high as the levels recorded in the younger patient cohort (<34 years). Western blot analysis and immunofluorescent studies confirmed the increments in SIRT1 protein levels in patients over 38 years old. N/A. Cumulus/oocyte complexes were retrieved by patients undergoing ovarian stimulation protocol for IVF. We cannot exclude the possibility that different stimulation protocols affect the correlations highlighted in this study. Future investigations should shed light on cumulus cells molecular profile according to different stimulation protocols. The overall results of our study point to the involvement of cohesins SA1/SA2 and SIRT1 deacetylase in telomere homeostasis in cumulus cells and highlight their possible eligibility as biomarkers of follicular physiology and ovarian aging. Merck Serono S.P.A Italy sponsored the study with financial support. There are no competing interests to declare.

SIRT1 induces epithelial-mesenchymal transition by promoting autophagic degradation of E-cadherin in melanoma cells

Melanoma is highly metastatic, and understanding of its molecular mechanism is urgently needed for the development of therapeutic targets and prognostic assessment for metastatic melanoma. SIRT1 is a nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylase, belonging to the mammalian sirtuin family. It has been reported that SIRT1 is associated with metastasis in various cancers. However, the molecular mechanism of SIRT1 in melanoma metastasis remains to be clarified. Here we report that SIRT1 induces the epithelial–mesenchymal transition (EMT) by accelerating E-cadherin degradation via autophagy and facilitates melanoma metastasis. Initially, we found that SIRT1 expression was frequently elevated in metastatic melanoma compared with primary melanoma. In addition, SIRT1 induced the EMT and promoted cell migration and invasion by decreasing E-cadherin expression. Further work demonstrated that SIRT1 accelerated the autophagic degradation of E-cadherin through deacetylation of Beclin 1. In addition, inhibition of autophagy recovered E-cadherin expression and suppressed cell migration and invasion by delaying the degradation of E-cadherin in SIRT1-overexpressing cells. Overall, our findings reveal a novel molecular mechanism for SIRT1 in melanoma metastasis, indicating that SIRT1 may serve as a viable therapeutic target for metastatic melanoma.

Resveratrol Promotes Recovery of Hearing following Intense Noise Exposure by Enhancing Cochlear SIRT1 Activity

The sirtuin SIRT1 is a highly conserved nicotinamide adenine dinucleotide (NAD)-dependent protein deacetylase known to have protective effects against a wide range of neurological disorders. In the present study, we discovered that C57BL/6 mice fed a long-term diet supplemented with high-dose resveratrol exhibited increased cochlear SIRT1 activity and presented a better recovery of hearing and less loss of hair cells after intense noise exposure compared with those fed a standard chew. Moreover, resveratrol attenuated cochlear SIRT1 decrease and reduced oxidative stress in the cochlea after noise exposure. These results suggest a considerable therapeutic potential of resveratrol for the treatment of noise-induced hearing loss.

Downregulation of SIRT6 is associated with poor prognosis in patients with non-small cell lung cancer.

ObjectiveTo explore the prognostic significance of nicotinamide adenine dinucleotide (NAD)-dependent protein deacetylase sirtuin-6 (SIRT6), encoded by the sirtuin 6 (SIRT6) gene, in a population of Chinese Han patients with non-small cell lung cancer (NSCLC).MethodsCancer tissues and normal lung tissues (>5 cm adjacent to cancer tissue) were collected from Chinese Han patients with NSCLC. Expression levels of SIRT6 and histone H3-acetyl K56 (H3K56), in cancer and normal lung tissues from patients with NSCLC, were detected by reverse-transcription polymerase chain reaction, Western blot and immunohistochemistry. Correlations between SIRT6 expression and various clinicopathologic features were investigated.ResultsOut of 86 patients included in the study, mRNA and protein SIRT6 levels were down-regulated in NSCLC tissue versus normal lung tissue, and SIRT6 levels were inversely correlated with H3K56 levels. Positive rates of SIRT6 were significantly correlated with degree of cell differentiation, TNM stage, lymph node metastasis, overall survival and metastasis-free survival.ConclusionDownregulation of SIRT6 expression may promote NSCLC malignancy in the Chinese Han population. SIRT6 may be a potential therapeutic target in Chinese Han patients with NSCLC.