Resveratrol Induced Premature Senescence Is Associated with DNA Damage Mediated SIRT1 and SIRT2 Down-Regulation

The natural polyphenolic compound resveratrol (3,4,5-trihydroxy-trans-stilbene) has broad spectrum health beneficial activities including antioxidant, anti-inflammatory, anti-aging, anti-cancer, cardioprotective, and neuroprotective effects. Remarkably, resveratrol also induces apoptosis and cellular senescence in primary and cancer cells. Resveratrol's anti-aging effects both in vitro and in vivo attributed to activation of a (NAD)-dependent histone deacetylase family member sirtuin-1 (SIRT1) protein. In mammals seven members (SIRT1-7) of sirtuin family have been identified. Among those, SIRT1 is the most extensively studied with perceptive effects on mammalian physiology and suppression of the diseases of aging. Yet no data has specified the role of sirtuins, under conditions where resveratrol treatment induces senescence. Current study was undertaken to investigate the effects of resveratrol in human primary dermal fibroblasts (BJ) and to clarify the role of sirtuin family members in particular SIRT1 and SIRT2 that are known to be involved in cellular stress responses and cell cycle, respectively. Here, we show that resveratrol decreases proliferation of BJ cells in a time and dose dependent manner. In addition the increase in senescence associated β-galactosidase (SA-β-gal) activity and methylated H3K9-me indicate the induction of premature senescence. A significant increase in phosphorylation of γ-H2AX, a surrogate of DNA double strand breaks, as well as in levels of p53, p21CIP1 and p16INK4A is also detected. Interestingly, at concentrations where resveratrol induced premature senescence we show a significant decrease in SIRT1 and SIRT2 levels by Western Blot and quantitative RT-PCR analysis. Conversely inhibition of SIRT1 and SIRT2 via siRNA or sirtinol treatment also induced senescence in BJ fibroblasts associated with increased SA-β-gal activity, γ-H2AX phosphorylation and p53, p21CIP1 and p16INK4A levels. Interestingly DNA damaging agent doxorubicin also induced senescence in BJ fibroblasts associated with decreased SIRT1/2 levels. In conclusion our data reveal that resveratrol induced premature senescence is associated with SIRT1 and SIRT2 down regulation in human dermal fibroblasts. Here we suggest that the concomitant decline in SIRT1/2 expression in response to resveratrol treatment may be a cause for induction of senescence, which is most likely mediated by a regulatory mechanism activated by DNA damage response.

Hydrogen-rich saline protects against oxidative damage and cognitive deficits after mild traumatic brain injury

Oxidative stress is the principal factor in traumatic brain injury (TBI) that initiates events that result in protracted neuronal dysfunction and remodeling. Importantly, antioxidants can protect the brain against oxidative damage and modulate the capacity of the brain to cope with synaptic dysfunction and cognitive impairment. However, no studies have investigated the effects of hydrogen-rich saline on cognitive deficits after TBI. In the present study, rats with fluid percussion injury (FPI) were used to investigate the protective effects of hydrogen-rich saline. The results showed that hydrogen-rich saline reduced the level of malondialdehyde (MDA) and elevated the level of silent information regulator 2 (Sir2). In addition, treatment with hydrogen-rich saline, which elevated the levels of molecules associated with brain-derived neurotropic factor (BDNF)-mediated synaptic plasticity, improved cognitive performance in the Morris water maze after mild TBI. These results suggest that hydrogen-rich saline can protect the brain against the deleterious effects of mild TBI on synaptic plasticity and cognition and that hydrogen-rich saline could be an effective therapeutic strategy for patients with cognitive deficits after TBI.

Altered levels of sirtuin genes (SIRT1, SIRT2, SIRT3 and SIRT6) and their target genes in adipose tissue from individual with obesity

INTRODUCTION

Sirtuins regulate energy metabolism and insulin sensitivity through their ability to act as energy sensors and regulators in several metabolic tissues.

AIM

To evaluate the expression levels of sirtuin genes SIRT1, SIRT2, SIRT3 and SIRT6 and their target genes (PPAR-α, PGC1-α, NRF1, DGAT1, PPAR-γ and FOXO3a) in subcutaneous adipose tissue collected from individuals with normoweight, overweight and obesity.

METHODS

Adipose tissue samples, obtained by lipoaspiration during liposuction surgery, were processed to obtain RNA, which was reverse-transcribed to cDNA. Then, we measured the expression levels of each gene by qPCR.

RESULTS

We found differences in the mRNA expression of SIRT1, SIRT2, SIRT3 and SIRT6 and their target genes (PPAR-α, PGC1-α, NRF1, DGAT1, PPAR-γ and FOXO3a) in adipose tissue from overweight or obese subjects when compared to normoweight subjects. All genes analyzed, except SIRT2, showed correlation with BMI.

CONCLUSIONS

Our findings in human subcutaneous adipose tissue show that increased body mass index modifies the expression of genes encoding sirtuins and their target genes, which are metabolic regulators of adipose tissue. Therefore, these could be used as biomarkers to predict the ability of adipose tissue to gain mass of adipose tissue.

Reduced gene expression of sirtuins and active AMPK levels in children and adolescents with obesity and insulin resistance

BACKGROUND

Sirtuins, including SIRT1 and SIRT2, are longevity-associated deacetylase enzymes that modulate metabolic homeostasis in response to the cellular energy state. Adenosine monophosphate activated protein kinase (AMPK) and SIRT1 are interrelated and share several common target pathways. This study aimed to evaluate the SIRT1 and SIRT2 gene expression in peripheral blood mononuclear cells (PBMCs) as well as plasma levels of AMPK, in obese children and adolescents.

MATERIALS AND METHODS

Participants included 60 children and adolescents (30 obese and 30 age- and gender-matched control subjects). Real-time polymerase chain reaction (PCR) was used to assess the SIRT1 and SIRT2 gene expression in PBMCs. Serum phospho-AMPK and insulin were measured using enzyme-linked immunosorbent assay (ELISA), and insulin resistance (IR) was calculated by the Homeostasis Model of Assessment of Insulin Resistance (HOMA-IR). Glucose and lipid profile were also measured.

RESULTS

SIRT1 gene expression and phospho-AMPK plasma levels were significantly diminished in obese subjects compared to the control group, and both SIRT1 and SIRT2 were significantly lower in obese children with IR compared to those without IR. SIRT1 expression revealed significant negative correlations with body mass index and waist circumference as well as insulin and HOMA-IR and a positive correlation with AMPK. SIRT2 negatively correlated with SIRT1 and positively correlated with high density lipoprotein-cholesterol (HDL-C).

CONCLUSION

SIRT1 and SIRT2 expression and AMPK levels decrease in children with obesity and IR. Targeting SIRT1 can be valuable in preventing obesity-associated IR in childhood and adolescence.

AGK2 Alleviates Lipopolysaccharide Induced Neuroinflammation through Regulation of Mitogen-Activated Protein Kinase Phosphatase-1

Neuroinflammation is associated with the progression of multiple neurological diseases. Many studies show that SIRT2 involves in multiple inflammatory processes. While, the mechanisms remain unclear. The purpose of this study was to explore the effect of SIRT2 inhibitor AGK2 on inflammatory responses and MAPK signaling pathways in LPS activated microglia in vitro and in vivo. The effect of AGK2 on cell viability of BV2 microglial cells was detected by CCK-8 assay. The expression of inflammatory cytokine iNOS was analyzed by western blotting and immunofluorescence. The mRNA expressions of iNOS, TNF-α, and IL-1β were detected by real-time polymerase chain reaction (RT-PCR). The SIRT2, phospho-P38, P38, phospho-JNK, JNK, phospho-ERK, ERK, α-tubulin, and acetyl-α-tubulin were analyzed by western blotting respectively. The interaction between SIRT2 and MKP-1 was measured by Co-immunoprecipitation (Co-IP) assay. Double immunofluorescent staining was performed to detect the expressions of CD11b and iNOS or SIRT2 in brain tissues. We found that AGK2 could suppress LPS-induced inflammatory cytokines (iNOS, TNF-α, and IL-1β) expression levels in BV2 microglial cells. Moreover, it could effectively reduce the expression of SIRT2 and increase the acetylation of α-tubulin in LPS activated BV2 microglial cells and LPS induced mice neuroinflammation. In addition, our results showed that AGK2 could reduce the increase of phosphorylation p38, JNK, and ERK after LPS challenge. Co-IP results showed that there was no direct interaction between MKP-1 and SIRT2. However, AGK2 by inhibition of SIRT2 could increase the expression of MKP-1. Furthermore, AGK2 could inhibit the activation of BV2 microglia and expression of iNOS and SIRT2 in LPS treated mice brain tissue. Taken together, our results suggested that AGK2 might alleviate lipopolysaccharide induced neuroinflammation through regulation of mitogen-activated protein kinase phosphatase-1. Graphical abstract.

Regulation of the mitogen-activated protein kinase kinase (MEK)-1 by NAD(+)-dependent deacetylases

Sirtuins are class III deacetylases that regulate many essential processes, including cellular stress, genome stability and metabolism. Although these NAD(+)-dependent deacetylases control adaptive cellular responses, identification of sirtuin-regulated signaling targets remain under-studied. Here, we demonstrate that acetylation of the mitogen-activated protein kinase kinase-1 (MEK1) stimulates its kinase activity, and that acetylated MEK1 is under the regulatory control of the sirtuin family members SIRT1 and SIRT2. Treatment of cells with sirtuin inhibitors, or siRNA knockdown of SIRT1 or SIRT2 proteins, increases MEK1 acetylation and subsequent phosphorylation of the extracellular signal-regulated kinase. Generation of an acetyl-specific MEK1 antibody demonstrates that endogenous acetylated MEK1 is extensively enriched in the nucleus following epidermal growth factor  stimulation. An acetyl-mimic of MEK1 increases inappropriate growth properties, suggesting that acetylation of MEK1 has oncogenic potential.

Helicobacter pylori infection increases sirt2 gene expression in gastric epithelial cells of gastritis patients

BACKGROUND

Helicobacter pylori Infection causes some clinical features of the human stomach such as gastritis, duodenal ulcer, and gastric cancer. It has been shown that Helicobacter pylori infection increases proinflammatory cytokine gene expressions in Gastric Epithelial Cells by activation of NF-kB signaling. Sirt1 and sirt2 as deacetylases play a certain role in the progress of inflammation in arthritis and lung infection by impacting the NF-kB.

AIMS

Sirt1 and sirt2 gene expressions in Gastric Epithelial cells of gastritis patients were surveyed with and without Helicobacter pylori infection and rate of prevalence of cagA and hopQ genes in Helicobacter pylori strains were investigated.

METHODS

25 biopsy samples of gastritis patients with Helicobacter pylori infection and 25 biopsy samples of gastritis patients without Helicobacter pylori infection were collected from Tohid Hospital in the city of Sanandaj throughout the year 2016. CDNA was made from total RNA extracted from biopsy samples (Qiagen® Kit). Sirt1 and sirt2 gene expressions were determined using the Corbett machine (Rotor-Gene 6000 Software). CagA and hopQ genes of Helicobacter pylori strains were determined by PCR using specific primers.

RESULTS

The sirt2 gene expression was increased in Gastric Epithelial Cells of gastritis patients with Helicobacter pylori infection. No significant relationship was found between sirt1 and sirt2 gene expressions as well as cagA and hopQ as Helicobacter pylori virulence genes.

CONCLUSIONS

This study shows the Helicobacter pylori infection duo to sirt2 gene up-expression. There is not a statistically significance relationship between cagA and hopQ Helicobacter pylori genotypes and sirt2 gene up-expression in Gastric Epithelial Cells of gastritis patients.

Sirtuin 2 (Sirt2) Expression Predicts Lymph Node Metastasis and Poor Overall Survival of Patients with Esophageal Squamous Cell Carcinoma

BACKGROUND

Altered expression of Sirtuin 2 (Sirt2) was associated with cancer development and progression. This study further assessed the association of Sirt2 expression with clinicopathological data and prognosis of patients with esophageal squamous cell carcinoma (ESCC) after postoperative concurrent chemoradiotherapy.

METHODS

Tissue specimens from 95 ESCC patients were collected for immunohistochemical analysis of Sirt2 expression, which was used to determine association with patient clinicopathological and survival data.

RESULTS

Sirt2 protein was expressed in 53.7% of ESCC tissue specimens but only in 25.3% of normal squamous epithelium (p = 0.000). Sirt2 expression was associated with tumor invasion (p = 0.005), lymph node metastasis (p = 0.003), and advanced clinical stage (p = 0.000), but not with tumor size (p = 0.199), or differentiation (p = 0.177). Sirt2 expression was associated with poor overall and progression-free survival (p = 0.034). The multivariate analysis showed that Sirt2 expression was an independent predictor for overall survival of patients with resected ESCC followed by concurrent chemoradiotherapy (p = 0.048).

CONCLUSIONS

Sirt2 protein expression in ESCC tissue specimens was associated with ESCC invasion, lymph node metastasis, and advanced tumor clinical stage, as well as poor overall and poor progression-free survival. Sirt2 expression is an independent prognostic predictor for ESCC patients.

[Cloning and expression analysis of Sirt2 in HEK293 cells]

AIM

To construct eukaryotic expression vector of Sirt2 and detect its expression in HEK293 cells.

METHODS

Total RNA was isolated from brain tissue of adult SD rat. A 1 130 bp fragment containing the coding region of Sirt2 was amplified by RT-PCR and the resulting PCR product was subcloned into PMD20-T vector and sequenced. Coding region of Sirt2 was generated with PCR by using the PMD20-T-Sirt2 as template, the amplified PCR fragment was inserted into the EcoR I and Hind III sites of the pcDNA3.1myc-his(-)A expression vector, and the sequence was confirmed by DNA sequencing. The expression of new construct pcDNA3.1 myc-his(-)A-Sirt2 in HEK293 cells was detected by immunofluorescence.

RESULTS

The full length coding region of Sirt2 was obtained and confirmed by sequencing, the expression of Sirt2 was detected successfully in HEK293 cells.

CONCLUSION

The eukaryotic expression vector of Sirt2 has been successfully constructed, which will provide a useful tool for designing an in-depth investigation of the role of Sirt2.

Effect of Resveratrol on Leptin and Sirtuin 2 Expression in the Kidneys in Streptozotocin-induced Diabetic Rats

OBJECTIVE

To investigate the effect of resveratrol (RSV) on the histopathology and leptin and sirtuin 2 expression levels of the kidneys in streptozotocin (STZ)-induced diabetic rats.

STUDY DESIGN

The study was carried out with 33 young, healthy, female Wistar Albino rats. STZ was given (50 mg/kg, intraperitoneal, single dose) to the rats to induce and constitute a diabetes model. After 1 month of STZ, resveratrol (10 mg/kg) was given for 15 days. Then the kidneys were evaluated histopathologically and the leptin and sirtuin 2 expressions were analyzed immunohistochemically.

RESULTS

High glucose and fewer weight levels were seen in the STZ-induced diabetes mellitus group. The glucose levels in the RSV-administered diabetic group showed a tendency to decrease but not significantly. Decreased signs of histopathologic kidney damage was seen in the RSV-administered diabetic group, and an increased expression of leptin was seen in the diabetic kidney tissues. There were no significant differences of sirtuin 2 expression levels among the groups.

CONCLUSION

It was observed that resveratrol caused changes in the diabetic kidney histology and leptin expression level. Resveratrol may be effective, with its antioxidant and antidiabetic effects, in the prevention of kidney damage caused by long-term hyperglycemia.

USP39 promotes retinal pathological angiogenesis in retinopathy of prematurity by stabilizing SIRT2 expression through deubiquitination

BACKGROUND

Retinopathy of prematurity (ROP) is a major cause of childhood blindness worldwide, highlighted by retinal neovascularization. Ubiquitin is present throughout the retina. The deubiquitinating enzyme ubiquitin-specific protease 39 (USP39) has been reported to be involved in angiogenesis. Here, this study aimed to investigate the effects of USP39 on ROP and its associated mechanism.

METHODS

Hypoxia-induced human retinal microvascular endothelial cells (hRMECs) were adopted for functional analyses. Detection of mRNA and protein was conducted using quantitative real-time PCR and western blotting. Cell migration, invasion and angiogenesis were evaluated using transwell and tube formation assays. Protein interaction was determined by immunoprecipitation assay. Oxygen-induced retinopathy (OIR) mouse models were used for in vivo analysis.

RESULTS

USP39 level was higher in hypoxia-induced hRMECs, functionally, USP39 silencing reversed hypoxia-induced migration, invasion and angiogenesis in hRMECs. In further mechanism analysis, we found that USP39 stabilized SIRT2 protein expression in hRMECs by inducing SIRT2 deubiquitination. Moreover, SIRT2 up-regulation abated hypoxia-evoked migration, invasion and angiogenesis in hRMECs. Besides that, the inhibitory effects of USP39 silencing on hypoxia-induced metastatic and angiogenic behaviors were abolished after SIRT2 overexpression. In addition, USP39 silencing blocked the activation of phosphoinositide 3-kinase (PI3K)/protein kinase B pathway (AKT) by regulating SIRT2. In vivo assay showed that levels of USP39, SIRT2, matrix metalloproteinase (MMP)-2 (MMP-2), MMP-9 and Vascular endothelial growth factor A (VEGFA) were increased in the retinas of OIR mice, while intravitreal injection of USP39 short hairpin RNA (shRNA) could reduce their expression.

CONCLUSION

USP39 stabilized SIRT2 expression by deubiquitination and promoted hypoxia-induced metastatic and angiogenic behaviors of RMECs in vitro, as well as retinal angiogenesis in vivo.