Tumor suppressor HIC1 directly regulates SIRT1 to modulate p53-dependent DNA-damage responses

Icariin enhances youth-like features by attenuating the declined gut microbiota in the aged mice

We previously reported the neuroprotective effects of icariin in rat cortical neurons. Here, we present a study on icariin's anti-aging effect in 24-month aged mice by treating them with a single daily dose of 100 mg/kg of icariin for 15 consecutive days. Icariin treatment improved motor coordination and learning skills while lowered oxidative stress biomarkers in the serum, brain, kidney, and liver of the aged mice. In addition, icariin improved the intestinal integrity of the aged mice by upregulating tight junction adhesion molecules and the Paneth and goblet cells, along with the reduction of iNOS and pro-inflammatory cytokines (IL-1β, TNF-α, IL-2 and IL-6, and IL-12). Icariin treatments also significantly upregulated aging-related signaling molecules, Sirt 1, 3 & 6, Pot1α, BUB1b, FOXO1, Ep300, ANXA3, Calb1, SNAP25, and BDNF in old mice. Through gut microbiota (GM) analysis, we observed icariin-associated improvements in GM composition of aged mice by reinstating bacteria found in the young mice, while suppressing some bacteria found in the untreated old mice. To clarify whether icariin's anti-aging effect is rooted in the GM, we performed fecal microbiota transfer (FMT) from icariin-treated old mice to the old mice. FMT-recipients exhibited similar improvements in the rotarod score and age-related biomarkers as observed in the icariin-treated old mice. Equal or better improvement on the youth-like features was noticed when aged mice were FMT with feces from young mice. Our study shows that both direct treatments with icariin and fecal transplant from the icariin-treated aged mice produce similar anti-aging phenotypes in the aged mice. We prove that GM plays a pivotal role in the healing abilities of icariin. Icariin has the potentials to be developed as a medicine for the wellness of the aged adults.

Phosphorylation of HIC1 (Hypermethylated in Cancer 1) Ser694 by ATM is essential for DNA repair

The tumor suppressor gene HIC1 (Hypermethylated in Cancer 1) encodes a transcriptional repressor involved in the DNA-damage response. A SUMOylation increase on HIC1 Lysine314 favors the direct transcriptional repression of SIRT1 and thus the P53-dependent apoptotic response to irreparable DNA double strand breaks (DSBs). HIC1 is also essential for DSBs repair but in a SUMOylation-independent manner. Here, we show that repairable DSBs induced by a 1 h Etoposide treatment results in three specific posttranslational modifications (PTMs) of HIC1. Two of these PTMs, phosphorylation of Serine 694 and Acetylation of Lysine 623 are located in the conserved HIC1 C-terminal region located downstream of the Zinc Finger DNA-binding domain. By contrast, phosphorylation of Serine 285 found in the poorly conserved central region is unique to the human protein. We showed that Ser694 phosphorylation is mediated mainly by the PIKK kinase ATM and is essential for the DNA repair activity of HIC1 as demonstrated by the lack of efficiency of the S694A point mutant in Comet assays. Thus, our results provide the first evidence for a functional role of the conserved HIC1 C-terminal region as a novel ATM substrate that plays an essential role in the cellular HIC1-mediated cellular response to repairable DSBs.

Surtuin 1 as a potential prognostic biomarker in very elderly patients with colorectal cancer

BACKGROUND/AIMS

Colorectal cancer (CRC) rate increases with aging. Aging-related proteins, such as sirtuins (SIRTs) may be a potential therapeutic target in the elderly patients with CRC. The clinical implications of SIRT1 and SIRT2 have not been reported for elderly patients with cancer. The aim of this study was to evaluate the impact of expression of SIRT1 and SIRT2 on clinical outcome in two extreme age groups of patients with CRC.

METHODS

The expression of SIRT1 and SIRT2 were evaluated in CRC tissues of 101 patients aged ≥ 80 years and 29 patients aged ≤ 40 years by immunohistochemistry. We defined the patients aged ≥ 80 years as the very elderly and patients aged ≤ 40 years as the young patients. Correlations between the expression of these proteins and clinicopathological features were analyzed.

RESULTS

The prognosis for the very elderly patients with high expressions of SIRT1 was significantly worse than that for patients showing low expression (median survival, 24.9 months vs. 38.6 months, p = 0.027) whereas high expression of SIRT2 better prognosis (median survival, 37.9 months vs. 17.3 months, p = 0.006). However, the young patients did not show any difference in prognosis according to expression of SIRT1 and SIRT2. In multivariate analysis, high SIRT1 expression retained statistical significance as a poor prognostic factor in the very elderly patients with CRC.

CONCLUSION

The results suggest that high SIRT1 expression could be predictive of a poor outcome for very elderly patients with CRC.

Germline and Somatic Whole-Exome Sequencing Identifies New Candidate Genes Involved in Familial Predisposition to Serrated Polyposis Syndrome

The serrated polyposis syndrome (SPS) is the most common and yet underdiagnosed colorectal polyposis syndrome. It is characterized by multiple and/or large colonic serrated polyps and a higher associated risk for colorectal cancer (CRC). The main objective of this study was to identify new candidate genes involved in the germline predisposition to SPS/CRC. Thirty-nine SPS patients from 16 families (≥2 patients per family) were recruited without alterations in well-known hereditary CRC genes, and germline and somatic whole-exome sequencing were performed. Germline rare variants with plausible pathogenicity, located in genes involved in cancer development, senescence and epigenetic regulation were selected. Somatic mutational profiling and signature analysis was pursued in one sample per family, when possible. After data filtering, ANXA10, ASXL1, CFTR, DOT1L, HIC1, INO80, KLF3, MCM3AP, MCM8, PDLIM2, POLD1, TP53BP1, WNK2 and WRN were highlighted as the more promising candidate genes for SPS germline predisposition with potentially pathogenic variants shared within families. Somatic analysis characterized mutational profiles in advanced serrated polyps/tumors, revealing a high proportion of hypermutated samples, with a prevalence of clock-like mutational signatures in most samples and the presence of DNA mismatch repair-defective signatures in some cases. In conclusion, we identified new candidate genes to be involved in familial SPS. Further functional studies and replication in additional cohorts are required to confirm the selected candidates.

Neuroprotective Effects of Exercise Postconditioning After Stroke via SIRT1-Mediated Suppression of Endoplasmic Reticulum (ER) Stress

While it is well-known that pre-stroke exercise conditioning reduces the incidence of stroke and the development of comorbidities, it is unclear whether post-stroke exercise conditioning is also neuroprotective. The present study investigated whether exercise postconditioning (PostE) induced neuroprotection and elucidated the involvement of SIRT1 regulation on the ROS/ER stress pathway. Adult rats were subjected to middle cerebral artery occlusion (MCAO) followed by either: (1) resting; (2) mild exercise postconditioning (MPostE); or (3) intense exercise postconditioning (IPostE). PostE was initiated 24 h after reperfusion and performed on a treadmill. At 1 and 3 days thereafter, we determined infarct volumes, neurological defects, brain edema, apoptotic cell death through measuring pro- (BAX and Caspase-3) and anti-apoptotic (Bcl-2) proteins, and ER stress through the measurement of glucose-regulated protein 78 (GRP78), inositol-requiring 1α (IRE1α), protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), Caspase-12, and SIRT1. Proteins were measured by Western blot. ROS production was detected by flow cytometry.Compared to resting rats, both MPostE and IPostE significantly decreased brain infarct volumes and edema, neurological deficits, ROS production, and apoptotic cell death. MPostE further increased Bcl-2 expression and Bcl-2/BAX ratio as well as BAX and Caspase-3 expressions and ROS production (*p < 0.05). Both PostE groups saw decreases in ER stress proteins, while MPostE demonstrated a further reduction in GRP78 (***p < 0.001) and Caspase-12 (*p < 0.05) expressions at 1 day and IRE1α (**p < 0.01) and CHOP (*p < 0.05) expressions at 3 days. Additionally, both PostE groups saw significant increases in SIRT1 expression.In this study, both mild and intense PostE levels induced neuroprotection after stroke through SIRT1 and ROS/ER stress pathway. Additionally, the results may provide a base for our future study regarding the regulation of SIRT1 on the ROS/ER stress pathway in the biochemical processes underlying post-stroke neuroprotection. The results suggest that mild exercise postconditioning might play a similar neuroprotective role as intensive exercise and could be an effective exercise strategy as well.

SIRT1-NOX4 signaling axis regulates cancer cachexia

Approximately one third of cancer patients die due to complexities related to cachexia. However, the mechanisms of cachexia and the potential therapeutic interventions remain poorly studied. We observed a significant positive correlation between SIRT1 expression and muscle fiber cross-sectional area in pancreatic cancer patients. Rescuing Sirt1 expression by exogenous expression or pharmacological agents reverted cancer cell–induced myotube wasting in culture conditions and mouse models. RNA-seq and follow-up analyses showed cancer cell–mediated SIRT1 loss induced NF-κB signaling in cachectic muscles that enhanced the expression of FOXO transcription factors and NADPH oxidase 4 (Nox4), a key regulator of reactive oxygen species production. Additionally, we observed a negative correlation between NOX4 expression and skeletal muscle fiber cross-sectional area in pancreatic cancer patients. Knocking out Nox4 in skeletal muscles or pharmacological blockade of Nox4 activity abrogated tumor-induced cachexia in mice. Thus, we conclude that targeting the Sirt1–Nox4 axis in muscles is an effective therapeutic intervention for mitigating pancreatic cancer–induced cachexia.

Epigenetics of Aging and Aging-Associated Diseases

Aging represents the multifactorial decline in physiological function of every living organism. Over the past decades, several hallmarks of aging have been defined, including epigenetic deregulation. Indeed, multiple epigenetic events were found altered across different species during aging. Epigenetic changes directly contributing to aging and aging-related diseases include the accumulation of histone variants, changes in chromatin accessibility, loss of histones and heterochromatin, aberrant histone modifications, and deregulated expression/activity of miRNAs. As a consequence, cellular processes are affected, which results in the development or progression of several human pathologies, including cancer, diabetes, osteoporosis, and neurodegenerative disorders. In this review, we focus on epigenetic mechanisms underlying aging-related processes in various species and describe how these deregulations contribute to human diseases.

The transcription factor Hypermethylated in Cancer 1 (Hic1) regulates neural crest migration via interaction with Wnt signaling

The transcription factor Hypermethylated in Cancer 1 (HIC1) is associated with both tumorigenesis and the complex human developmental disorder Miller-Dieker Syndrome. While many studies have characterized HIC1 as a tumor suppressor, HIC1 function in development is less understood. Loss-of-function mouse alleles show embryonic lethality accompanied with developmental defects, including craniofacial abnormalities that are reminiscent of human Miller-Dieker Syndrome patients. However, the tissue origin of the defects has not been reported. In this study, we use the power of the Xenopus laevis model system to explore Hic1 function in early development. We show that hic1 mRNA is expressed throughout early Xenopus development and has a spatial distribution within the neural plate border and in migrating neural crest cells in branchial arches. Targeted manipulation of hic1 levels in the dorsal ectoderm that gives rise to neural and neural crest tissues reveals that both overexpression and knockdown of hic1 result in craniofacial defects with malformations of the craniofacial cartilages. Neural crest specification is not affected by altered hic1 levels, but migration of the cranial neural crest is impaired both in vivo and in tissue explants. Mechanistically, we find that Hic1 regulates cadherin expression profiles and canonical Wnt signaling. Taken together, these results identify Hic1 as a novel regulator of the canonical Wnt pathway during neural crest migration.

Development and function of smooth muscle cells is modulated by Hic1 in mouse testis

In mammalian testis, contractile peritubular myoid cells (PMCs) regulate the transport of sperm and luminal fluid, while secreting growth factors and extracellular matrix proteins to support the spermatogonial stem cell niche. However, little is known about the role of testicular smooth muscle cells during postnatal testicular development. Here we report age-dependent expression of hypermethylated in cancer 1 (Hic1; also known as ZBTB29) in testicular smooth muscle cells, including PMCs and vascular smooth muscle cells, in the mouse. Postnatal deletion of Hic1 in smooth muscle cells led to their increased proliferation and resulted in dilatation of seminiferous tubules, with increased numbers of PMCs. These seminiferous tubules contained fewer Sertoli cells and more spermatogonia, and fibronectin was not detected in their basement membrane. The expression levels of genes encoding smooth muscle contractile proteins, Acta2 and Cnn1, were downregulated in the smooth muscle cells lacking Hic1, and the seminiferous tubules appeared to have reduced contractility. These data imply a role for Hic1 in determining the size of seminiferous tubules by regulating postnatal smooth muscle cell proliferation, subsequently affecting spermatogenesis in adulthood.

Hepatocellular Expression of SIRT1 and Its Effect on Hepatocellular Carcinoma Progression: A Future Therapeutic Perspective

Hepatocellular carcinoma (HCC) is an aggressive primary hepatic malignancy with a significant morbidity and mortality rate. Although chemotherapy along with surgical incision is believed to be an effective therapeutic approach, to date recurrence is being lifted a major concern. Thus, identifying another best therapeutic approach is becoming the main aim of physicians and scholars. In support of this, recently, several studies reported a significant observation of Sirtuin1 (SIRT1) overexpression in the malignant tumor cells, including HCC. As a result, they believed that overexpression of SIRT1 may have an effect on the progression of HCC by targeting growth and/or apoptotic controlling transcriptional factors/signaling pathways. Similarly, other reports confirmed that SIRT1 inhibition had a direct or indirect role in the control of tumor cell growth and metastasis. Therefore, inhibiting the expression and activity of SIRT1 might have a therapeutic effect to handle HCC. However, there are a limited number of reviews regarding the issue, and here, we summarized hepatocellular expression of SIRT1 and its role on HCC progression.

Opposite Roles of the JMJD1A Interaction Partners MDFI and MDFIC in Colorectal Cancer

MyoD family inhibitor (MDFI) and MDFI domain-containing (MDFIC) are homologous proteins known to regulate myogenic transcription factors. Hitherto, their role in cancer is unknown. We discovered that MDFI is up- and MDFIC downregulated in colorectal tumors. Mirroring these different expression patterns, MDFI stimulated and MDFIC inhibited growth of HCT116 colorectal cancer cells. Further, MDFI and MDFIC interacted with Jumonji C domain-containing (JMJD) 1 A, a histone demethylase and epigenetic regulator involved in colorectal cancer. JMJD1A influenced transcription of several genes that were also regulated by MDFI or MDFIC. Notably, the HIC1 tumor suppressor gene was stimulated by JMJD1A and MDFIC, but not by MDFI, and HIC1 overexpression phenocopied the growth suppressive effects of MDFIC in HCT116 cells. Similar to colorectal cancer, MDFI was up- and MDFIC downregulated in breast, ovarian and prostate cancer, but both were overexpressed in brain, gastric and pancreatic tumors that implies MDFIC to also promote tumorigenesis in certain tissues. Altogether, our data suggest a tumor modulating function for MDFI and MDFIC in colorectal and other cancers that may involve their interaction with JMJD1A and a MDFIC→HIC1 axis.

Association between HIC1 promoter methylation and solid tumor: A meta-analysis

The epigenetic silencing of tumor suppressor genes by promoter methylation plays an increasingly important role in cancer research. A number of studies have reported the contribution of HIC1 promoter methylation towards the occurrence and development of solid tumors, even though HIC1 promoter methylation has also been found in normal and benign tissue samples. We sought to perform a more accurate and comprehensive meta-analysis to assess the association between HIC1 promoter methylation and cancer risk. We searched and retrieved all published studies on HIC1 promoter methylation in PubMed, Google Scholar, Embase, Cochrane Library, and Web of Science databases. After two reviewers checked the studies and extracted the necessary data independently, the meta-analysis was performed using STATA 12.0 software. A total of 14 case-control studies (949 cancer patients, 282 benign, and 371 normal controls) were included in our study. We report a significantly elevated HIC1 promoter methylation in tumor samples compared to normal (OR = 7.02, 95 % CI 3.12-15.78, P < 0.001) and benign controls (OR = 2.69, 95 % CI 1.13-6.42, P = 0.025). Subgroup analysis stratified by ethnicity showed a significantly reduced heterogeneity among North American (I² = 0.0 %, P = 0.502) and European (I² = 33.7 %, P = 0.183) samples. In addition, heterogeneity was significantly reduced among MSP based detection method (I² = 36.4 %, P = 0.139) when samples were stratified based on the methylation detection methods. The overall outcome demonstrated that HIC1 promoter methylation may be involved in the occurrence and development of solid tumors and has the potential to serve as an epigenetic maker in various specific tumors.

Long noncoding RNA-GAS5 attenuates progression of glioma by eliminating microRNA-10b and Sirtuin 1 in U251 and A172 cells

Long noncoding RNA (lncRNA) growth arrest-specific 5 (GAS5) is implicated in several cancers via modulating microRNAs (miRs). However, little information is available about the correlation between GAS5 and miR-10b. Therefore, we sought out to investigate the biological role of GAS5-miR-10b node mainly in glioma cells. We artificially modulated GAS5 to explore its roles in viability assayed by cell counting kit-8 (CCK-8), motile activities by 24-Transwell assay, as well as apoptosis by a flow cytometer and Western blot assay. miR-10b and Sirtuin 1 (Sirt1) were quantified by qRT-PCR. After co-transfection, we analyzed the viability, migration, invasion, apoptosis, and Sirt1 expression. Western blot was implemented to detect the phosphorylated forms of PTEN, PI3K, AKT, MEK, and ERK. GAS5 inhibited proliferation and motile behaviors, and fortified apoptosis. As for the viability and motile activities, the property of GAS5 was reversed in miR-10b-replenished U251 and A172 cells, while maintained in miR-10b-deficient cells. Additionally, GAS5-induced apoptosis was abolished by miR-10b overexpression while fortified by miR-10b silence. Besides, GAS5 negatively modulated Sirt1 via miR-10b. Moreover, Sirt1 negatively modulated PTEN and positively mediated the abovementioned regulators. GAS5 represses the process of glioma cells by decreasing miR-10b, which as accompanied by Sirt1 silence-induced inactivation of PTEN/PI3K/AKT and MEK/ERK cascades.

SIRT1 Regulation in Ageing and Obesity

Ageing and obesity have common hallmarks: altered glucose and lipid metabolism, chronic inflammation and oxidative stress are some examples. The downstream effects of SIRT1 activity have been thoroughly explored, and their research is still in expanse. SIRT1 activation has been shown to regulate pathways with beneficiary effects on 1) ageing and obesity-associated metabolic disorders such as metabolic syndrome, insulin resistance and type-II diabetes with, 2) chronic inflammatory processes such as arthritis, atherosclerosis and emphysema, 3) DNA damage and oxidative stress with impact on neurodegenerative diseases, cardiovascular health and some cancers. This knowledge intensified the interest in uncovering the mechanisms regulating the expression and activity of SIRT1. This review focuses on the upstream regulatory mechanisms controlling SIRT1, and how this knowledge could potentially contribute to the development of therapeutic interventions.

PHF20L1 as a H3K27me2 reader coordinates with transcriptional repressors to promote breast tumorigenesis

TUDOR domain-containing proteins (TDRDs) are chiefly responsible for recognizing methyl-lysine/arginine residue. However, how TDRD dysregulation contributes to breast tumorigenesis is poorly understood. Here, we report that TUDOR domain-containing PHF20L1 as a H3K27me2 reader exerts transcriptional repression by recruiting polycomb repressive complex 2 (PRC2) and Mi-2/nucleosome remodeling and deacetylase (NuRD) complex, linking PRC2-mediated methylation and NuRD-mediated deacetylation of H3K27. Furthermore, PHF20L1 was found to serve as a potential MYC and hypoxia-driven oncogene, promoting glycolysis, proliferation, and metastasis of breast cancer cells by directly inhibiting tumor suppressors such as HIC1, KISS1, and BRCA1. PHF20L1 expression was also strongly correlated with higher histologic grades of breast cancer and markedly up-regulated in several cancers. Meanwhile, Phf20l1 deletion not only induces growth retardation and mammary ductal outgrowth delay but also inhibits tumorigenesis in vivo. Our data indicate that PHF20L1 promotes tumorigenesis, supporting the pursuit of PHF20L1 as a target for cancer therapy.

Knockdown of TFAM in Tumor Cells Retarded Autophagic Flux through Regulating p53 Acetylation and PISD Expression

Mitochondrial transcription factor A (TFAM) is required for mitochondrial DNA replication and transcription, which are essential for mitochondrial biogenesis. Previous studies reported that depleting mitochondrial functions by genetic deletion of TFAM impaired autophagic activities. However, the underlying mechanisms remain largely unknown. In the current study, we identified that knockdown of TFAM repressed the synthesis of autophagy bio-marker LC3-II in tumor cells and decreased the expression of phosphatidyl-serine decarboxylase (PISD). Besides, downregulation of PISD with siRNA reduced the level of LC3-II, indicating that depletion of TFAM retarded autophagy via inhibiting PISD expression. Furthermore, it was found that the tumor repressor p53 could stimulate the transcription and expression of PISD by binding the PISD enhancer. Additionally, the protein stability and transcriptional activity of p53 in TFAM knockdown tumor cells was attenuated, and this was associated with decreased acetylation, especially the acetylation of lysine 382 of p53. Finally, we identified that TFAM knockdown increased the NAD⁺/NADH ratio in tumor cells. This led to the upregulation of Sirtuin1 (SIRT1), a NAD-dependent protein deacetylase, to deacetylate p53 and attenuated its transcriptional activation on PISD. In summary, our study discovered a new mechanism regarding disturbed autophagy in tumor cells with mitochondrial dysfunction due to the depletion of TFAM.

Aberrations of miR-126-3p, miR-181a and sirtuin1 network mediate Di-(2-ethylhexyl) phthalate-induced testicular damage in rats: The protective role of hesperidin

Recently, oxidative stress was implicated in the environmental contaminant Di-(2-ethylhexyl) phthalate (DEHP)-induced testicular toxicity, however the mechanism is unclear. We investigated the role of oxidative stress-responsive microRNAs in DEHP-induced aberrations and the protective effect of the citrus flavonoid, hesperidin (HSP). Male Wistar rats were randomly allocated into four groups as vehicle-treated control, DEHP-alone group (500 mg/kg/day) for 30 days, and HSP (25 or 50 mg/kg) for 60 days; testicular damage was triggered by oral administration of DEHP (500 mg/kg/day) after thirty days of oral administration of HSP (25 or 50 mg/kg). DEHP administration reduced testis weight coefficient, serum testosterone, testicular 3β-hydroxysteroid dehydrogenase and antioxidant enzyme activities, and elevated serum fatty acid-binding protein-9, testicular malondialdehyde, and Bax/Bcl2 ratio. Aberrant testicular miR-126-3p and miR-181a expression was observed, along with decreased expression of sirtuin1 (SIRT1) and its targets; nuclear factor-erythroid 2-related factor2, haeme oxygenase-1, and superoxide dismutase2. HSP administration significantly ameliorated these changes and restored testicular function in a dose-dependent manner. We highlight a novel role of oxidative stress-miR-126/miR-181a-SIRT1 network in mediating DEHP-induced changes which were reversed by the antioxidant HSP.

The Citrus Flavonoid Naringenin Protects the Myocardium from Ageing-Dependent Dysfunction: Potential Role of SIRT1

Sirtuin 1 (SIRT1) enzyme plays a pivotal role in the regulation of many physiological functions. In particular, it is implicated in ageing-related diseases, such as cardiac hypertrophy, myocardial infarct, and endothelial dysfunction; moreover, its expression decreases with age. Therefore, an effective strategy to extend the lifespan and improve cardiovascular function is the enhancement of the expression/activity of SIRT1 with exogenous agents. The Citrus flavonoid naringenin (NAR) presents structural similarity with the natural SIRT1 activator resveratrol. In this study, we demonstrate through in vitro assays that NAR significantly activates SIRT1 enzyme and shows antisenescence effects. The binding mode of NAR into SIRT1 was detailed investigated through in silico studies. Moreover, chronic administration (for six months) of NAR (100 mg/kg/day) to 6-month-old mice leads to an enhancement of SIRT1 expression and a marked reduction of reactive oxygen species production in myocardial tissue. Furthermore, at the end of the treatment, the plasma levels of two well-known markers of cardiovascular inflammation, TNF-α and IL6, are significantly reduced in 12-month-old mice treated with NAR, as well as the cardiovascular risk (total cholesterol/HDL ratio) compared to control mice. Finally, the age-associated fibrotic remodeling, which is well detected through a Mallory trichrome staining in the vehicle-treated 12-month-old mice, is significantly reduced by the chronic treatment with NAR. Moreover, an improvement of myocardium functionality is highlighted by the enhancement of citrate synthase activity and stabilization of the mitochondrial membrane potential after NAR treatment. Taken together, these results suggest that a nutraceutical approach with NAR may have positive impacts on many critical hallmarks of myocardial senescence, contributing to improve the cardiac performance in aged subjects.

Noninvasive quantification of SIRT1 expression-activity and pharmacologic inhibition in a rat model of intracerebral glioma using 2-[18F]BzAHA PET/CT/MRI

Background

Several studies demonstrated that glioblastoma multiforme progression and recurrence is linked to epigenetic regulatory mechanisms. Sirtuin 1 (SIRT1) plays an important role in glioma progression, invasion, and treatment response and is a potential therapeutic target. The aim of this study is to test the feasibility of 2-[¹⁸F]BzAHA for quantitative imaging of SIRT1 expression–activity and monitoring pharmacologic inhibition in a rat model of intracerebral glioma.

Methods

Sprague Dawley rats bearing 9L (N = 12) intracerebral gliomas were injected with 2-[¹⁸F]BzAHA (300–500 µCi/animal i.v.) and dynamic positron-emission tomography (PET) imaging was performed for 60 min. Then, SIRT1 expression in 9L tumors (N = 6) was studied by immunofluorescence microscopy (IF). Two days later, rats with 9L gliomas were treated either with SIRT1 specific inhibitor EX-527 (5 mg/kg, i.p.; N = 3) or with histone deacetylases class IIa specific inhibitor MC1568 (30 mg/kg, i.p.; N = 3) and 30 min later were injected i.v. with 2-[¹⁸F]BzAHA. PET-computerized tomography-magnetic resonance (PET/CT/MR) images acquired after EX-527 and MC1568 treatments were co-registered with baseline images.

Results

Standard uptake values (SUVs) of 2-[¹⁸F]BzAHA in 9L tumors measured at 20 min post-radiotracer administration were 1.11 ± 0.058 and had a tumor-to-brainstem SUV ratio of 2.73 ± 0.141. IF of 9L gliomas revealed heterogeneous upregulation of SIRT1, especially in hypoxic and peri-necrotic regions. Significant reduction in 2-[¹⁸F]BzAHA SUV and distribution volume in 9L tumors was observed after administration of EX-527, but not MC1568.

Conclusions

PET/CT/MRI with 2-[¹⁸F]BzAHA can facilitate studies to elucidate the roles of SIRT1 in gliomagenesis and progression, as well as to optimize therapeutic doses of novel SIRT1 inhibitors.

Regulation of the SIRT1 signaling pathway in NMDA-induced Excitotoxicity

Silent Information Regulator 1 (SIRT1), an NAD⁺-dependent deacetylase, contributes to the neuroprotective effect. However, intracellular signaling pathways that affect SIRT1 function remain unknown. It is well known that N-methyl-D-aspartate (NMDA) receptor activation induces calcium influx which then activates PKC, and SIRT1 is a mRNA target for HuR protein. We hypothesize that Ca²⁺-PKC-HuR-SIRT1 pathway modulates SIRT1 function. The present study is to investigate the potential pathway of SIRT1 in the SH-SY5Y cell line as an in vitro model of NMDA-induced neurotoxicity. The results showed that: (1) SIRT1 levels were downregulated in NMDA model; (2) NMDA induced an increase in serine phosphorylation of HuR, while inhibition of serine phosphorylation of HuR increased SIRT1 levels, promoting cell survival; (3) PKC inhibitor (Gö 6976) reversed NMDA insults and also suppressed serine phosphorylation of HuR; (4) 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM), an intracellular calcium chelator, fully reversed NMDA insults and also inhibited PKC activity evoked by NMDA. These results indicate that intracellular elevated Ca²⁺ activates PKC, which phosphorylates HuR and then promotes SIRT1 mRNA decay and subsequent neuronal death in NMDA model. Therefore, the study suggests that inhibition of Ca²⁺-PKC-HuR-SIRT1 pathway could be an effective strategy for preventing certain neurological diseases related to NMDA excitotoxicity.

SIRT6, a Mammalian Deacylase with Multitasking Abilities

Mammalian sirtuins have emerged in recent years as critical modulators of multiple biological processes, regulating cellular metabolism, DNA repair, gene expression, and mitochondrial biology. As such, they evolved to play key roles in organismal homeostasis, and defects in these proteins have been linked to a plethora of diseases, including cancer, neurodegeneration, and aging. In this review, we describe the multiple roles of SIRT6, a chromatin deacylase with unique and important functions in maintaining cellular homeostasis. We attempt to provide a framework for such different functions, for the ability of SIRT6 to interconnect chromatin dynamics with metabolism and DNA repair, and the open questions the field will face in the future, particularly in the context of putative therapeutic opportunities.

Duck Oil-loaded Nanoemulsion Inhibits Senescence of Angiotensin II-treated Vascular Smooth Muscle Cells by Upregulating SIRT1

Cellular senescence is associated with age-related vascular disorders and has been implicated in vascular dysfunctions. Here, we show that duck oil-loaded nanoemulsion (DO-NE) attenuates premature senescence of vascular smooth muscle cells (VSMCs) triggered by angiotensin II (Ang II). Compared with control nanoemulsion (NE), DO-NE significantly inhibited the activity of senescence-associated β-galactosidase, which is a biomarker of cellular senescence, in Ang II-treated VSMCs. SIRT1 protein expression was dose- and time-dependently induced in VSMCs exposed to DO-NE, but not in those exposed to NE, and SIRT1 promoter activity was also elevated. Consistently, DO-NE also dose-dependently rescued Ang II-induced repression of SIRT1 expression, indicating that SIRT1 is linked to the anti-senescence action of DO-NE in VSMCs treated with Ang II. Furthermore, the SIRT1 agonist resveratrol potentiated the effects of DO-NE on VSMCs exposed to Ang II, whereas the SIRT1 inhibitor sirtinol elicited the opposite effect. These findings indicate that DO-NE inhibits senescence by upregulating SIRT1 and thereby impedes vascular aging triggered by Ang II.

Ghrelin induces autophagy and CXCR4 expression via the SIRT1/AMPK axis in lymphoblastic leukemia cell lines

T cell acute lymphoblastic leukemia (T-ALL) is one of the most frequent malignancies in children, and the CXCR4 receptor plays an important role in the metastasis of this malignancy. Ghrelin is a hormone with various functions including stimulation of the release of growth hormone and autophagy in cancer cells. Moreover, SIRT1 and AMPK (AMP-activated protein kinase) stimulate expression of proteins involved in autophagy. On the other hand, autophagic cell death can be an alternative target for cancer therapy, in the absence of apoptosis. The relationship between ghrelin and the SIRT1/AMPK axis and the resulting effects on autophagy, apoptosis, proliferation, and expression of CXCR4 and the ghrelin receptor (GHS-R1a), in Jurkat and Molt-4 human lymphoblastic cell lines was not previously clear. Here we demonstrate that SIRT1 expression is upregulated during the induction of autophagy by ghrelin, an effect that is inhibited by inactivation of SIRT1/AMPK axis. In addition, ghrelin can affect CXCR4 and GHS-R1a expression. In conclusion, this work reveals that ghrelin induces autophagy, invasion, and downregulation of ghrelin receptor expression via the SIRT1/AMPK axis in lymphoblastic cell lines. However, in these cell lines ghrelin-induced autophagy does not lead to cell death due to weak induction of apoptosis.

Chidamide Enhances the Cytotoxicity of Cytarabine and Sorafenib in Acute Myeloid Leukemia Cells by Modulating H3K9me3 and Autophagy Levels

Previous studies showed that chidamide enhances the cytotoxicity of drugs in acute myeloid leukemia (AML) cells. Therefore, we examined whether chidamide enhanced the cytotoxicity of drugs in AML cells by affecting H3K9me3 and autophagy levels. AML cells (THP-1 and MV4-11 cells) were treated with chidamide, cytarabine (Ara-c), or sorafenib alone or in combination. Cell proliferation and survival rates were analyzed by MTT, flow cytometry, and Western blotting assays. The results showed that a low dose of chidamide enhanced the cytotoxicity of Ara-c or sorafenib in AML cells, decreasing proliferation and increasing apoptosis. H3K9me3 levels as assessed by Western blotting were upregulated by chidamide treatment. Chromatin immunoprecipitation sequencing, which was used to investigate potential signaling pathways, indicated that the autophagy pathway might play a role in the effects of chidamide. The level of autophagy induced in AML cells upon treatment with Ara-c or sorafenib was inhibited by chidamide, and autophagy markers (LC3, P62) were tested by Western blotting. SIRT1 messenger RNA (mRNA) and protein levels were lower in AML cells treated with Ara-c or sorafenib in combination with chidamide than those in cells treated with these drugs alone. Additionally, the Integrative Genomics Viewer results indicate that the H3K9me3 changes were related to SIRT1-binding sites. Together, these results show that chidamide enhances the cytotoxicity of two chemotherapy drugs in AML cells by increasing the H3K9me3 level and inhibiting autophagy via decreasing the expression of SIRT1. Chidamide may be a potential treatment strategy for AML in the future, especially for refractory AML patients.

USP7 Deubiquitinates and Stabilizes SIRT1

The NAD⁺ -dependent protein deacetylase silent information regulator 1 (SIRT1) targets multiple proteins for deacetylation, and it has been implicated in a variety of cellular pathways and human diseases. However, it remains unclear how the abundance of SIRT1 is regulated. Here, by mass spectrometry analysis of SIRT1-containing protein complexes, we revealed that SIRT1 is physically associated with the ubiquitin-specific protease USP7. Importantly, we found that USP7 cleaves K48-linked polyubiquitin chains of SIRT1 and promotes SIRT1 stabilization. Accordingly, we demonstrated that treatment of cells with an enzymatic inhibitor of USP7 led to a decreased level of SIRT1 expression and accumulation of SIRT1 polyubiquitination. Collectively, our findings indicate that USP7 is a critical regulator of SIRT1 and provide a new pathway for the maintenance of SIRT1 abundance in cells. Anat Rec, 303:1337-1345, 2020. © 2019 American Association for Anatomy.

miR-128 Functions as an OncomiR for the Downregulation of HIC1 in Breast Cancer

Hypermethylated in cancer 1 (HIC1) is continually decreased in breast cancer. However, the underlying molecular basis of the upstream regulation of HIC1 remains elusive. Here, we showed that HIC1 was downregulated in breast cancer tissues. Bioinformatics analysis identified that miR-128 might potentially target HIC1. HIC1 was proved as the target gene of miR-128 by overexpressing or knocking down miR-128. Additionally, we observed that HIC1 suppression by miR-128 increased cell invasion, proliferation, and reduced apoptosis. Lastly, we found that miR-128 accelerated tumor growth in xenograft mice by inhibiting HIC1. Altogether, this study presents the first evidence that miR-128 suppresses the expression of HIC1 to accelerate breast cancerogenesis.

KMT2D deficiency enhances the anti-cancer activity of L48H37 in pancreatic ductal adenocarcinoma

BACKGROUND

Novel therapeutic strategies are urgently needed for patients with a delayed diagnosis of pancreatic ductal adenocarcinoma (PDAC) in order to improve their chances of survival. Recent studies have shown potent anti-neoplastic effects of curcumin and its analogues. In addition, the role of histone methyltransferases on cancer therapeutics has also been elucidated. However, the relationship between these two factors in the treatment of pancreatic cancer remains unknown. Our working hypothesis was that L48H37, a novel curcumin analog, has better efficacy in pancreatic cancer cell growth inhibition in the absence of histone-lysine N-methyltransferase 2D (KMT2D).

AIM

To determine the anti-cancer effects of L48H37 in PDAC, and the role of KMT2D on its therapeutic efficacy.

METHODS

The viability and proliferation of primary (PANC-1 and MIA PaCa-2) and metastatic (SW1990 and ASPC-1) PDAC cell lines treated with L48H37 was determined by CCK8 and colony formation assay. Apoptosis, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) levels, and cell cycle profile were determined by staining the cells with Annexin-V/7-AAD, JC-1, DCFH-DA, and PI respectively, as well as flow cytometric acquisition. In vitro migration was assessed by the wound healing assay. The protein and mRNA levels of relevant factors were analyzed using Western blotting, immunofluorescence and real time-quantitative PCR. The in situ expression of KMT2D in both human PDAC and paired adjacent normal tissues was determined by immunohistochemistry. In vivo tumor xenografts were established by injecting nude mice with PDAC cells. Bioinformatics analyses were also conducted using gene expression databases and TCGA.

RESULTS

L48H37 inhibited the proliferation and induced apoptosis in SW1990 and ASPC-1 cells in a dose- and time-dependent manner, while also reducing MMP, increasing ROS levels, arresting cell cycle at the G2/M stages and activating the endoplasmic reticulum (ER) stress-associated protein kinase RNA-like endoplasmic reticulum kinase/eukaryotic initiation factor 2α/activating transcription factor 4 (ATF4)/CHOP signaling pathway. Knocking down ATF4 significantly upregulated KMT2D in PDAC cells, and also decreased L48H37-induced apoptosis. Furthermore, silencing KMT2D in L48H37-treated cells significantly augmented apoptosis and the ER stress pathway, indicating that KMT2D depletion is essential for the anti-neoplastic effects of L48H37. Administering L48H37 to mice bearing tumors derived from control or KMT2D-knockdown PDAC cells significantly decreased the tumor burden. We also identified several differentially expressed genes in PDAC cell lines expressing very low levels of KMT2D that were functionally categorized into the extrinsic apoptotic signaling pathway. The KMT2D high- and low-expressing PDAC patients from the TCGA database showed similar survival rates,but higher KMT2D expression was associated with poor tumor grade in clinical and pathological analyses.

CONCLUSION

L48H37 exerts a potent anti-cancer effect in PDAC, which is augmented by KMT2D deficiency.

Epigenetic Reprogramming and Emerging Epigenetic Therapies in CML

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder characterized by BCR-ABL1, an oncogenic fusion gene arising from the Philadelphia chromosome. The development of tyrosine kinase inhibitors (TKIs) to overcome the constitutive tyrosine kinase activity of the BCR-ABL protein has dramatically improved disease management and patient outcomes over the past 20 years. However, the majority of patients are not cured and developing novel therapeutic strategies that target epigenetic processes are a promising avenue to improve cure rates. A number of epigenetic mechanisms are altered or reprogrammed during the development and progression of CML, resulting in alterations in histone modifications, DNA methylation and dysregulation of the transcriptional machinery. In this review these epigenetic alterations are examined and the potential of epigenetic therapies are discussed as a means of eradicating residual disease and offering a potential cure for CML in combination with current therapies.

Epigenetic Regulation of TRAIL Signaling: Implication for Cancer Therapy

One of the main characteristics of carcinogenesis relies on genetic alterations in DNA and epigenetic changes in histone and non-histone proteins. At the chromatin level, gene expression is tightly controlled by DNA methyl transferases, histone acetyltransferases (HATs), histone deacetylases (HDACs), and acetyl-binding proteins. In particular, the expression level and function of several tumor suppressor genes, or oncogenes such as c-Myc, p53 or TRAIL, have been found to be regulated by acetylation. For example, HATs are a group of enzymes, which are responsible for the acetylation of histone proteins, resulting in chromatin relaxation and transcriptional activation, whereas HDACs by deacetylating histones lead to chromatin compaction and the subsequent transcriptional repression of tumor suppressor genes. Direct acetylation of suppressor genes or oncogenes can affect their stability or function. Histone deacetylase inhibitors (HDACi) have thus been developed as a promising therapeutic target in oncology. While these inhibitors display anticancer properties in preclinical models, and despite the fact that some of them have been approved by the FDA, HDACi still have limited therapeutic efficacy in clinical terms. Nonetheless, combined with a wide range of structurally and functionally diverse chemical compounds or immune therapies, HDACi have been reported to work in synergy to induce tumor regression. In this review, the role of HDACs in cancer etiology and recent advances in the development of HDACi will be presented and put into perspective as potential drugs synergizing with TRAIL's pro-apoptotic potential.

HIC2, a new transcription activator of SIRT1

The protein deacetylase SIRT1 is crucial to numerous physiological processes, such as aging, metabolism, and autoimmunity, and is repressed by various transcription factors, including HIC1. Conversely, we found that HIC2, which is highly homologous to HIC1, is a transcriptional activator of SIRT1 due to opposite activity of the intermediate domains of the two homologs. Importantly, this relationship between HIC2 and SIRT1 could be important for cardiac development, where both proteins are implicated. Here, we assessed whether ectopic expression of HIC2, and subsequent upregulation of SIRT1, might decrease apoptosis in H9c2 cardiomyocytes under simulated ischemia/reperfusion (I/R) injury conditions. Our results demonstrate that unlike its structural homolog HIC1, HIC2 is a pivotal transcriptional activator of SIRT1 and, consequently, may protect the heart from I/R injury.

Sirtuin 1 knockdown inhibits glioma cell proliferation and potentiates temozolomide toxicity via facilitation of reactive oxygen species generation

Malignant glioma is one of the most common types of primary malignancies in the human central nervous system. Temozolomide (TMZ) is the most commonly used drug in clinical therapy of glioma; however, chemoresistance makes glioma difficult to cure and relapse likely. Sirtuin 1 (SIRT1) serves important roles in cell proliferation, differentiation and metabolism, but the role of SIRT1 in human glioma remains largely unexplored. In the present study, SIRT1 expression was assessed in human glioma tissues and cells. RNA interference and SIRT1 inhibitor were used to determine the effect of SIRT1 on glioma growth inhibition and glioma cell chemoresistance in vitro and in vivo. The levels of reactive oxygen species (ROS) in glioma cells were detected with the dihydroethidium probe following SIRT1 inhibition. The results demonstrated that SIRT1 was overexpressed in glioma tissues and cells, and patients with higher SIRT1 expression exhibited poorer prognosis. SIRT1 inhibition inhibited the proliferation of U87 and U251 cells. In addition, SIRT1 knockdown and SIRT1 inhibitor could significantly sensitize glioma cells to TMZ treatment in vitro and in vivo. The expression of Ki67 and p53 was demonstrated to be regulated by SIRT1. Finally, SIRT1 could regulate intracellular ROS generation in TMZ. In summary, SIRT1 was essential for glioma tumorigenesis and glioma cell chemoresistance. SIRT1 inhibition increased the sensitivity of glioma cells for TMZ via the facilitation of intracellular ROS generation, which suggested that SIRT1 may serve as a target for clinical therapy of glioma.

Transcriptional Repressor HIC1 Contributes to Suppressive Function of Human Induced Regulatory T Cells

Regulatory T (Treg) cells are critical in regulating the immune response. In vitro induced Treg (iTreg) cells have significant potential in clinical medicine. However, applying iTreg cells as therapeutics is complicated by the poor stability of human iTreg cells and their variable suppressive activity. Therefore, it is important to understand the molecular mechanisms of human iTreg cell specification. We identified hypermethylated in cancer 1 (HIC1) as a transcription factor upregulated early during the differentiation of human iTreg cells. Although FOXP3 expression was unaffected, HIC1 deficiency led to a considerable loss of suppression by iTreg cells with a concomitant increase in the expression of effector T cell associated genes. SNPs linked to several immune-mediated disorders were enriched around HIC1 binding sites, and in vitro binding assays indicated that these SNPs may alter the binding of HIC1. Our results suggest that HIC1 is an important contributor to iTreg cell development and function.

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Hypermethylated in cancer 1 (HIC1) is upregulated in iTreg cells

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HIC1-deficient iTreg cells express FOXP3 but have reduced suppressive ability

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Autoimmune-disease-associated SNPs are enriched within HIC1 binding loci

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HIC1 is an important regulator of iTreg development and function

Micromanaging aerobic respiration and glycolysis in cancer cells

BACKGROUND

Cancer cells possess a common metabolic phenotype, rewiring their metabolic pathways from mitochondrial oxidative phosphorylation to aerobic glycolysis and anabolic circuits, to support the energetic and biosynthetic requirements of continuous proliferation and migration. While, over the past decade, molecular and cellular studies have clearly highlighted the association of oncogenes and tumor suppressors with cancer-associated glycolysis, more recent attention has focused on the role of microRNAs (miRNAs) in mediating this metabolic shift. Accumulating studies have connected aberrant expression of miRNAs with direct and indirect regulation of aerobic glycolysis and associated pathways.

SCOPE OF REVIEW

This review discusses the underlying mechanisms of metabolic reprogramming in cancer cells and provides arguments that the earlier paradigm of cancer glycolysis needs to be updated to a broader concept, which involves interconnecting biological pathways that include miRNA-mediated regulation of metabolism. For these reasons and in light of recent knowledge, we illustrate the relationships between metabolic pathways in cancer cells. We further summarize our current understanding of the interplay between miRNAs and these metabolic pathways. This review aims to highlight important metabolism-associated molecular components in the hunt for selective preventive and therapeutic treatments.

MAJOR CONCLUSIONS

Metabolism in cancer cells is influenced by driver mutations but is also regulated by posttranscriptional gene silencing. Understanding the nuanced regulation of gene expression in these cells and distinguishing rapid cellular responses from chronic adaptive mechanisms provides a basis for rational drug design and novel therapeutic strategies.

Metformin and tenovin-6 synergistically induces apoptosis through LKB1-independent SIRT1 down-regulation in non-small cell lung cancer cells

Sirtuin 1 (SIRT1) is known to play a role in a variety of tumorigenesis processes by deacetylating histone and non‐histone proteins; however, antitumour effects by suppressing SIRT1 activity in non‐small cell lung cancer (NSCLC) remain unclear. This study was designed to scrutinize clinicopathological significance of SIRT1 in NSCLC and investigate effects of metformin on SIRT1 inhibition. This study also evaluated new possibilities of drug combination using a SIRT1 inhibitor, tenovin‐6, in NSCLC cell lines. It was found that SIRT1 was overexpressed in 300 (62%) of 485 formalin‐fixed paraffin‐embedded NSCLC tissues. Its overexpression was significantly associated with reduced overall survival and poor recurrence‐free survival after adjusted for histology and pathologic stage. Thus, suppression of SIRT1 expression may be a reasonable therapeutic strategy for NSCLC. Metformin in combination with tenovin‐6 was found to be more effective in inhibiting cell growth than either agent alone in NSCLC cell lines with different liver kinase B1 (LKB1) status. In addition, metformin and tenovin‐6 synergistically suppressed SIRT1 expression in NSCLC cells regardless of LKB1 status. The marked reduction in SIRT1 expression by combination of metformin and tenovin‐6 increased acetylation of p53 at lysine 382 and enhanced p53 stability in LKB1‐deficient A549 cells. The combination suppressed SIRT1 promoter activity more effectively than either agent alone by up‐regulating hypermethylation in cancer 1 (HIC1) binding at SIRT1 promoter. Also, suppressed SIRT1 expression by the combination synergistically induced caspase‐3‐dependent apoptosis. The study concluded that metformin with tenovin‐6 may enhance antitumour effects through LKB1‐independent SIRT1 down‐regulation in NSCLC cells.

Mapping Retinoic Acid-Dependant 5mC Derivatives in Mouse Embryonic Fibroblasts

Methylase-assisted bisulfite sequencing (MAB-seq) is a derivatization technique to evaluate the presence of 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC) at base-pair resolution. Although MAB-seq was originally designed to study these metabolites under steady-state conditions, we have developed an alternative protocol to evaluate the dynamics of 5-fC/5-caC accumulation in response to agonists, such as all-trans retinoic acid (ATRA). In addition, this protocol utilizes a lower quantity of the M.SssI enzyme without compromising methylation efficiency and requires less bench time. Herein, we describe the use of MAB-seq assay to evaluate the generation of 5-fC/5-caC in response to ATRA in mouse embryonic fibroblasts, using the hypermethylated in cancer 1 (Hic1) locus as a model system.

Retracted Article: Aclarubicin regulates glioma cell growth and DNA damage through the SIRT1/PI3K/AKT signaling pathway

Aclarubicin (ACR), an anthracycline anti-tumor agent, is known to play important roles in cancer. Evidence has suggested that ACR has therapeutic effects on rats intracranially implanted with C6 glioma cells. However, the function and mechanism of ACR in glioma cells remain elusive. In this study, we examined the effects of ACR on glioma cell growth, apoptosis, and DNA damage. Our results showed that treatment with different concentrations of ACR (1, 2, and 5 μM) markedly impeded glioma cell survival, significantly decreased cell proliferation, and increased cell apoptosis and caspase-3 activity. Furthermore, ACR treatment promoted DNA damage through phosphorylation of ATM and CHK1 in U87 and U251 cells. Treatment with ACR also increased sirtuin 1 (SIRT1) expression and inhibited phosphatidylinositol 3′-kinase (PI3K)/AKT pathway activation. Interestingly, we found that AKT overexpression reversed the effects of ACR on glioma cell survival, proliferation, apoptosis, and DNA damage. Thus, our data suggest that ACR induces apoptosis and DNA damage in U87 and U251 cells through the SIRT1/PI3K/AKT signaling pathway.

Aclarubicin (ACR), an anthracycline anti-tumor agent, is known to play important roles in cancer.

The Beneficial Roles of SIRT1 in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) as a result of accumulated drugs in the human body metabolized into toxic agents and helps generate heavy oxidative stress, inflammation, and apoptosis, which induces necrosis in hepatocytes and ultimately damages the liver. Sirtuin 1 (SIRT1) is said to have multiple vital roles in cell proliferation, aging, and antistress systems of the human body. The levels of SIRT1 and its activation precisely modulate its critical role in the interaction between multiple step procedures of DILI. The nuclear factor kappa-light-chain-enhancer of activated B cell- (NF-κB-) mediated inflammation signaling pathway, reactive oxygen species (ROS), DNA damage, mitochondrial membrane potential collapse, and endoplasmic reticulum (ER) stress also contribute to aggravate DILI. Apoptosis is regarded as the terminal reaction followed by multiple signaling cascades including caspases, p53, and mitochondrial dysfunction which have been said to contribute in DILI. The SIRT1 activator is regarded as a potential candidate for DILI, because the former could inhibit signaling of p53, NF-κB, and ER stress. On the other hand, overexpression of SIRT1 also enhances the activation of antioxidant responses via Kelch-like ECH-associated protein 1- (Keap1-) nuclear factor- (erythroid-derived 2-) like 2 (Nrf2) signaling. The current manuscript will highlight the mechanism of DILI and the interaction of SIRT1 with various cytoplasmic factors leading to DILI along with the summary of potent SIRT1 agonists.

Circular RNA hsa_circ_0076248 promotes oncogenesis of glioma by sponging miR-181a to modulate SIRT1 expression

Glioma is one of the most common primary malignancies of the central nervous system, which has aggressive clinical behavior and a poorer prognosis. MicroRNAs (miRs) are a class of small noncoding RNAs that function as mediators of gene expression, which can be sponged by circRNA provided with a closed circular structure. Dysregulations of circular RNAs (circRNAs) and miRs have been implicated in the development and progression of glioma. In the current study, we investigated the role of circular RNA hsa_circ_0076248 in mediating the oncogenesis of glioma by sponging miR‐181a to modulate silent information regulator 1 (SIRT1) expression in vitro and in vivo. The quantitative real‐time polymerase chain reaction results showed that the expression of miR‐181a was significantly decreased in glioma tissues and cell lines compared with normal brain tissues and normal gliocyte, respectively, and the expression of hsa_circ_0076248 and SIRT1 demonstrated the opposite. Bioinformatics analysis identified hsa_circ_0076248 could sponge miR‐181a, and miR‐181a could target the mRNA of SIRT1. Our results verified that downregulating hsa_circ_0076248 or upregulating miR‐181a could depress the proliferation and invasion of glioma in vitro and in vivo. The experiment also showed that downregulating hsa_circ_0076248 or upregulating miR‐181a could remarkably promote the temozolomide chemotherapy sensitivity. Furthermore, Western blot analysis testified that downregulating hsa_circ_0076248 or upregulating miR‐181a could promote the expression of p53 and SIRT1. In summary, our study sheds light on the regulatory mechanism of hsa_circ_0076248 in glioma growth and invasion via sponging miR‐181a, which downregulates the SIRT1 expression and also suggests that hsa_circ_0076248, miR‐181a, and SIRT1 may serve as potential therapeutic targets for glioma.

The Role of Sirt1 in Ischemic Stroke: Pathogenesis and Therapeutic Strategies

Silent mating type information regulation 2 homolog 1 (Sirt1), a nicotine adenine dinucleotide (NAD⁺)-dependent enzyme, is well-known in playing a part in longevity. Ischemic stroke is a major neurological disorder and is a leading cause of death and adult disability worldwide. Recently, many studies have focused on the role of Sirt1 in ischemic stroke. Numerous studies consider Sirt1 as a protective factor and investigate the signaling pathways involved in the process under ischemic stress. However, the answer to whether upregulation of Sirt1 improves the outcome of stroke is still a controversy. In this review, we discuss the role and mechanisms of Sirt1 in the setting of ischemic stroke.

Hypermethylated in cancer 1 (HIC1) suppresses bladder cancer progression by targeting yes-associated protein (YAP) pathway

OBJECTIVES

Bladder cancer (BCa) is the most common malignant tumor in the urinary system. Growing evidence suggests that as a tumor suppressor gene, hypermethylated in cancer 1 (HIC1) is correlated with various malignancies in the modulation of tumor progression. This study aims to investigate the effect of HIC1 on regulating the proliferation, migration, and invasion of BCa.

METHODS

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot (WB) were used to evaluate the expression of HIC1 messenger RNA and protein in human BCa tissues and cells. Proliferation, migration and invasion assays, and flow cytometry assay were performed to assess the biological functional role of HIC1 in BCa. Co-immunoprecipitation (Co-IP) examined the protein-protein interaction. The signaling pathways involved in the mode of action of HIC1 in BCa were also investigated.

RESULTS

HIC1 was found downregulated in tested samples. Cloning formation assay and cell-proliferation activity analysis showed that overexpression of HIC1 significantly inhibited the proliferation of BCa cells, while knockdown led to the opposite, namely the promotion of the proliferation. Flow cytometry assay confirmed the arrest of the cell cycle at the G1 phase with overexpression of HIC1 observed. Moreover, HIC1 inhibited migration and invasion of BCa. Co-IP showed the binding between YAP (yes-associated protein) and TEAD (TEA domain/transcription enhancer factor family members) as well as the cancerostatic activity of HIC1, partially manifested via its negative regulation of YAP signaling pathway.

CONCLUSIONS

Our data unprecedently showed that HIC1 was responsible for the inhibition of proliferation, migration, and invasion of BCa via the YAP signaling pathway. These findings suggested that therapeutic strategies regulating HIC1 expression might provide effective treatments for BCa.

HIC1 deletion promotes breast cancer progression by activating tumor cell/fibroblast crosstalk

Breast cancer (BrCa) is the malignant tumor that most seriously threatens female health; however, the molecular mechanism underlying its progression remains unclear. Here, we found that conditional deletion of hypermethylated in cancer 1 (HIC1) in the mouse mammary gland might contribute to premalignant transformation in the early stage of tumor formation. Moreover, the chemokine (C-X-C motif) ligand 14 (CXCL14) secreted by HIC1-deleted BrCa cells bound to its cognate receptor GPR85 on mammary fibroblasts in the microenvironment and was responsible for activating these fibroblasts via the ERK1/2, Akt, and neddylation pathways, whereas the activated fibroblasts promoted BrCa progression via the induction of epithelial-mesenchymal transition (EMT) by the C-C chemokine ligand 17 (CCL17)/CC chemokine receptor 4 (CCR4) axis. Finally, we confirmed that the HIC1-CXCL14-CCL17 loop was associated with the malignant progression of BrCa. Therefore, the crosstalk between HIC1-deleted BrCa cells and mammary fibroblasts might play a critical role in BrCa development. Exploring the progression of BrCa from the perspective of microenvironment will be beneficial for identifying the potential prognostic markers of breast tumor and providing more effective treatment strategies.

Detection of Sirtuin-1 protein expression in peripheral blood leukocytes in dogs

Sirtuin-1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylase with a large number of protein substrates. It has attracted a lot of attention in association with extending lifespan. The objective of this study was to enable the evaluation of SIRT1 expression in peripheral blood mononuclear cells (PBMCs) from dogs by flow cytometry. Three transcript variants were amplified from PBMCs by reverse transcription PCR and the nucleotide sequences were analyzed. On the basis of deduced amino acid sequence, a monoclonal antibody against human SIRT1, 1F3, was selected to detect canine SIRT1. Canine SIRT1 in peripheral blood mononuclear cells was successfully detected by western blotting using this antibody. Intracellular canine SIRT1 was also detected in permeabilized 293T cells transfected with a canine SIRT1 expression plasmid by flow cytometry using this antibody. SIRT1 was detected in all leukocyte subsets including lymphocytes, granulocytes and monocytes. The expression level was markedly different among individual dogs. These results indicated that the method applied in this study is useful for evaluating canine SIRT1 levels in PBMCs from dogs.

Landscape of transcription and long non-coding RNAs reveals new insights into the inflammatory and fibrotic response following ventilator-induced lung injury

BACKGROUND

Mechanical ventilation can cause ventilator-induced lung injury (VILI) and lung fibrosis; however, the underlying mechanisms are still not fully understood. RNA sequencing is a powerful means for detecting vitally important protein-coding transcripts and long non-coding RNAs (lncRNAs) on a genome-wide scale, which may be helpful for reducing this knowledge gap.

METHODS

Ninety C57BL/6 mice were subjected to either high tidal volume ventilation or sham operation, and then mice with ventilation were randomly allocated to periods of recovery for 0, 1, 3, 5, 7, 14, 21, or 28 days. Lung histopathology, wet-to-dry weight ratio, hydroxyproline concentration, and transforming growth factor beta 1 (TGF-β1) levels were determined to evaluate the progression of inflammation and fibrosis. To compare sham-operated lungs, and 0- and 7-day post-ventilated lungs, RNA sequencing was used to elucidate the expression patterns, biological processes, and functional pathways involved in inflammation and fibrosis.

RESULTS

A well-defined fibrotic response was most pronounced on day 7 post-ventilation. Pairwise comparisons among the sham and VILI groups showed a total of 1297 differentially expressed transcripts (DETs). Gene Ontology analysis determined that the stimulus response and immune response were the most important factors involved in inflammation and fibrosis, respectively. Kyoto Encyclopedia of Genes and Genomes analysis revealed that mechanistic target of rapamycin (mTOR), Janus kinase-signal transducer and activator of transcription (JAK/STAT), and cyclic adenosine monophosphate (cAMP) signaling were implicated in early inflammation; whereas TGF-β, hypoxia inducible factor-1 (HIF-1), Toll-like receptor (TLR), and kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathways were significantly involved in subsequent fibrosis. Additionally, 332 DE lncRNAs were identified and enriched in the processes of cellular and biological regulation. These lncRNAs may potentially regulate fibrosis through signaling pathways such as wingless/integrase-1 (Wnt), HIF-1, and TLR.

CONCLUSIONS

This is the first transcriptome study to reveal all of the transcript expression patterns and critical pathways involved in the VILI fibrotic process based on the early inflammatory state, and to show the important DE lncRNAs regulated in inflammation and fibrosis. Together, the results of this study provide novel perspectives into the potential molecular mechanisms underlying VILI and subsequent fibrosis.

The role of extracellular and intracellular Nicotinamide phosphoribosyl-transferase in cancer: Diagnostic and therapeutic perspectives and challenges

Nicotinamide phosphoribosyl-transferase (Nampt) or pre-B cell colony-enhancing factor or visfatin represents a pleiotropic molecule acting as an enzyme, a cytokine and a growth factor. Intracellular Nampt plays an important role in cellular bioenergetics and metabolism, particularly NAD biosynthesis. NAD biosynthesis is critical in DNA repair, oncogenic signal transduction, transcription, genomic integrity and apoptosis. Although its insulin-mimetic function remains a controversial issue, extracellular Nampt presents proliferative, anti-apoptotic, pro-inflammatory, pro-angiogenic and metastatic properties. Nampt is upregulated in many malignancies, including obesity-associated cancers, and is associated with worse prognosis. Serum Nampt may be a potential diagnostic and prognostic biomarker in cancer. Pharmacologic agents that neutralize Nampt or medications that decrease Nampt levels or downregulate signaling pathways downstream of Nampt may prove to be useful anti-cancer treatments. In particular, Nampt inhibitors as monotherapy or in combination therapy have displayed anti-cancer activity in vivo and in vitro. The aim of this review is to explore the role of Nampt in cancer pathophysiology as well as to synopsize the mechanisms underlying the association between extracellular and intracellular Nampt, and malignancy. Exploring the interplay of cellular bioenergetics, inflammation and adiposopathy is expected to be of importance in the development of preventive and therapeutic strategies against cancer.

Role of Sirtuin1-p53 regulatory axis in aging, cancer and cellular reprogramming

Regulatory role of Sirtuin 1 (SIRT1), one of the most extensively studied members of its kind in histone deacetylase family in governing multiple cellular fates, is predominantly linked to p53 activity. SIRT1 deacetylates p53 in a NAD+-dependent manner to inhibit transcription activity of p53, in turn modulate pathways that are implicated in regulation of tissue homoeostasis and many disease states. In this review, we discuss the role of SIRT1-p53 pathway and its regulatory axis in the cellular events which are implicated in cellular aging, cancer and reprogramming. It is noteworthy that these cellular events share few common regulatory pathways, including SIRT1-p53-LDHA-Myc, miR-34a,-Let7 regulatory network, which forms a positive feedback loop that controls cell cycle, metabolism, proliferation, differentiation, epigenetics and many others. In the context of aging, SIRT1 expression is reduced as a protective mechanism against oncogenesis and for maintenance of tissue homeostasis. Interestingly, its activation in aged cells is evidenced in response to DNA damage to protect the cells from p53-dependent apoptosis or senescence, predispose these cells to neoplastic transformation. Importantly, the dual roles of SIRT1-p53 axis in aging and tumourigenesis, either as tumour suppressor or tumour promoter are determined by SIRT1 localisation and type of cells. Conceptualising the distinct similarity between tumorigenesis and cellular reprogramming, this review provides a perspective discussion on involvement of SIRT1 in improving efficiency in the induction and maintenance of pluripotent state. Further research in understanding the role of SIRT1-p53 pathway and their associated regulators and strategies to manipulate this regulatory axis very likely foster the development of therapeutics and strategies for treating cancer and aging-associated degenerative diseases.

Dysregulation of the epigenetic landscape of normal aging in Alzheimer's disease

Aging is the strongest risk factor for Alzheimer's disease (AD), although the underlying mechanisms remain unclear. The chromatin state, in particular through the mark H4K16ac, has been implicated in aging and thus may play a pivotal role in age-associated neurodegeneration. Here we compare the genome-wide enrichment of H4K16ac in the lateral temporal lobe of AD individuals against both younger and elderly cognitively normal controls. We found that while normal aging leads to H4K16ac enrichment, AD entails dramatic losses of H4K16ac in the proximity of genes linked to aging and AD. Our analysis highlights the presence of three classes of AD-related changes with distinctive functional roles. Furthermore, we discovered an association between the genomic locations of significant H4K16ac changes with genetic variants identified in prior AD genome-wide association studies and with expression quantitative trait loci. Our results establish the basis for an epigenetic link between aging and AD.