SIRT1 as a therapeutic target in inflammaging of the pulmonary disease

Exogenous neutrophil elastase enters bronchial epithelial cells and suppresses cigarette smoke extract-induced heme oxygenase-1 by cleaving sirtuin 1

An imbalance between oxidative stress and antioxidant activity plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Cigarette smoke, a major risk factor of COPD, induces cellular oxidative stress, but levels of antioxidants such as heme oxygenase-1 (HO-1) are reduced in individuals with severe COPD. In this study, we evaluated the molecular mechanism of reduced HO-1 expression in human bronchial epithelial cells. We found that cigarette smoke extract (CSE) increases HO-1 levels via activation of NFE2-related factor 2 (Nrf2). However, pretreating cells with the protease neutrophil elastase (NE) suppressed the CSE-induced expression of HO-1 mRNA and protein. NE also decreased the sirtuin 1 (SIRT1) level, but did not inhibit CSE-induced nuclear translocation and DNA-binding activity of Nrf2. Transfection of cells with a Myc/His-tagged SIRT1 expression vector completely blocked the NE-mediated suppression of HO-1 expression. We further noted that the NE-induced down-regulation of SIRT1 was not due to decreased transcription or proteasomal/lysosomal degradation or loss of solubility. Immunofluorescence staining revealed that NE enters the cell cytoplasm, and we observed that NE directly cleaved SIRT1 in vitro, indicating that SIRT1 levels are decreased via direct degradation by internalized NE. Of note, we observed decreased SIRT1 levels in NE-treated primary human bronchial epithelial cells and in lung homogenates from both smokers and patients with COPD. In conclusion, NE suppresses CSE-induced HO-1 expression by cleaving SIRT1. This finding indicates the importance of cross-talk between oxidative stress and protease responses in the pathogenesis of COPD.

Melatonin regulates the aging mouse hippocampal homeostasis via the sirtuin1-FOXO1 pathway

Sirtuin1 (SIRT1) and forkhead box transcription factor O subfamily 1 (FOXO1) play vital roles in the maintenance of hippocampal neuronal homeostasis during aging. Our previous study showed that melatonin, a hormone mainly secreted by the pineal gland, restored the impaired memory of aged mice. Age-related neuronal energy deficits contribute to the pathogenesis of several neurodegenerative disorders. An attempt has been made to determine whether the effect of melatonin is mediated through the SIRT1-FOXO1 pathways. The present results showed that aged mice (22 months old) exhibited significantly downregulated SIRT1, FOXO1, and melatonin receptors MT1 and MT2 protein expression but upregulated tumor suppressor protein 53 (p53), acetyl-p53 protein (Ac-p53), mouse double minute 2 homolog (MDM2), Dickkopf-1 (DKK1) protein expression in mouse hippocampus compared with the young group. Melatonin treatment (10 mg/kg, daily in drinking water for 6 months) in aged mice significantly attenuated the age-induced downregulation of SIRT1, FOXO1, MT1 and MT2 protein expression and attenuated the age-induced increase in p53, ac-p53, MDM2, and DKK1 protein and mRNA expression. Melatonin decreased p53 and MDM2 expression, which led to a decrease in FOXO1 degradation. These present results suggest that melatonin may help the hippocampal neuronal homeostasis by increasing SIRT1, FOXO1 and melatonin receptors expression while decreasing DKK1 expression in the aging hippocampus. DKK1 can be induced by the accumulation of amyloid β (Aβ) which is the major hallmark of Alzheimer's disease.

Caveolin1/protein arginine methyltransferase1/sirtuin1 axis as a potential target against endothelial dysfunction

Endothelial dysfunction (ED), an established response to cardiovascular risk factors, is characterized by increased levels of soluble molecules secreted by endothelial cells (EC). Evidence suggest that ED is an independent predictor of cardiac events and that it is associated with a deficiency in production or bioavailability of nitric oxide (NO) and/or an imbalance in the relative contribution of endothelium-derived relaxing and contracting factors. ED can be reversed by treating cardiovascular risk factors, hence, beyond ambiguity, ED contributes to initiation and progression of atherosclerotic disease. Majority of cardiovascular risk factors act by a common pathway, oxidative stress (OS), characterized by an imbalance in bioavailability of NO and reactive oxygen species (ROS). Enhanced ROS, through several mechanisms, alters competence of EC that leads to ED, reducing its potential to maintain homeostasis and resulting in development of cardiovascular disease (CVD). Influential mechanisms that have been implicated in the development of ED include (i) presence of elevated levels of NOS inhibitor, asymmetric dimethylarginine (ADMA) due to augmented enzyme activity of protein arginine methyl transferase-1 (PRMT1); (ii) decrease in NO generation by endothelial nitric oxide synthase (eNOS) uncoupling, or by reaction of NO with free radicals and (iii) impaired post translational modification of protein (PTM) such as eNOS, caveolin-1 (cav1) and sirtuin-1 (SIRT1). However, the inter-related mechanisms that concur to developing ED is yet to be understood. The events that possibly overlay include OS-induced sequestration of SIRT1 to caveolae facilitating cav1-SIRT1 association; potential increase in lysine acetylation of enzymes such as eNOS and PRMT1 leading to enhanced ADMA formation; imbalance in acetylation-methylation ratio (AMR); diminished NO generation and ED. Here we review current literature from research showing interdependent association between cav1-PRMT1-SIRT1 to the outcomes of experimental and clinical research aiming to preserve endothelial function with gene- or pharmaco-therapy.

Fermented Chinese formula Shuan-Tong-Ling attenuates ischemic stroke by inhibiting inflammation and apoptosis

The fermented Chinese formula Shuan-Tong-Ling is composed of radix puerariae (Gegen), salvia miltiorrhiza (Danshen), radix curcuma (Jianghuang), hawthorn (Shanzha), salvia chinensis (Shijianchuan), sinapis alba (Baijiezi), astragalus (Huangqi), panax japonicas (Zhujieshen), atractylodes macrocephala koidz (Baizhu), radix paeoniae alba (Baishao), bupleurum (Chaihu), chrysanthemum (Juhua), rhizoma cyperi (Xiangfu) and gastrodin (Tianma), whose aqueous extract was fermented with lactobacillus, bacillus aceticus and saccharomycetes. Shuan-Tong-Ling is a formula used to treat brain diseases including ischemic stroke, migraine, and vascular dementia. Shuan-Tong-Ling attenuated H₂O₂-induced oxidative stress in rat microvascular endothelial cells. However, the potential mechanism involved in these effects is poorly understood. Rats were intragastrically treated with 5.7 or 17.2 mL/kg Shuan-Tong-Ling for 7 days before middle cerebral artery occlusion was induced. The results indicated Shuan-Tong-Ling had a cerebral protective effect by reducing infarct volume and increasing neurological scores. Shuan-Tong-Ling also decreased tumor necrosis factor-α and interleukin-1β levels in the hippocampus on the ischemic side. In addition, Shuan-Tong-Ling upregulated the expression of SIRT1 and Bcl-2 and downregulated the expression of acetylated-protein 53 and Bax. Injection of 5 mg/kg silent information regulator 1 (SIRT1) inhibitor EX527 into the subarachnoid space once every 2 days, four times, reversed the above changes. These results demonstrate that Shuan-Tong-Ling might benefit cerebral ischemia/reperfusion injury by reducing inflammation and apoptosis through activation of the SIRT1 signaling pathway.

SIRT1‑mediated regulation of oxidative stress induced by Pseudomonas aeruginosa lipopolysaccharides in human alveolar epithelial cells

Sirtuin1 (SIRT1) is an NAD+‑dependent deacetylase that exhibits multiple biological functions, including cell differentiation inhibition, transcription regulation, cell cycle regulation and anti‑apoptosis. Lipopolysaccharides (LPS) are crucial virulence factors produced by Pseudomonas aeruginosa and serve an important role in adjusting the interactions between the host and the pathogen. However, the effect of SIRT1 in the regulation of LPS‑induced A459 human alveolar epithelial cells (AECs) oxidative stress remains unclear. The cellular reactive oxygen species (ROS) production was examined in A549 cells that were supplemented with LPS. Relative cell signaling pathway proteins were further investigated by western blot analysis. It was identified that LPS downregulated SIRT1 expression, however, upregulated ROS generation, which was associated with the increase of nuclear factor (NF)‑κB and acetyl‑NF‑κB. Activation of SIRT1 by resveratrol significantly reversed the effects of LPS on A549 cells. By contrast, inhibition of SIRT1 by nicotinamide had the opposite effects that enhance cell ROS production. Thus, the results indicated that SIRT1 serves an important role in the regulation of oxidative stress induced by LPS in human AECs.

SRT1720, a SIRT1 specific activator, protected H2O2-induced senescent endothelium

Silent information regulator 1 (SIRT1) plays a critical role in maintaining vascular homeostasis via modulating senescent-related signal pathway, however, the molecular mechanism remains modest clarified. The purpose of this study was to examine whether SIRT1 specific activator SRT1720 would exhibit pro-angiogenic and anti-aging properties in response to hydrogen peroxide (H2O2)-induced endothelial senescence, and determine the underlying mechanisms. We pre-treated senescent human umbilical vein endothelial cells (HUVECs) with SRT1720, senescence-associated beta-galactosidase activity, apoptosis, migration, tube formation, proliferation and angiogenic factors were quantitatively examined. The results revealed that pharmacologic activation of SIRT1 by SRT1720 rescued apoptotic HUVECs and upregulated angiogenic response through reinforcing the protein expressions of angiogenic and survival factors in vitro. Furthermore, we confirmed that the expressions of endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF) and phosphoryl-Akt were augmented in SRT1720-treated senescent HUVECs. In conclusion, our data indicated that SRT1720 could protect against endothelial senescence and maintain cell function via Akt/eNOS/VEGF axis.

Effect of Daisaikoto on Expressions of SIRT1 and NF-kappaB of Diabetic Fatty Liver Rats Induced by High-Fat Diet and Streptozotocin

BACKGROUND

Daisaikoto (DSKT), a classical traditional Chinese herbal formula, has been used for treating digestive diseases for 1800 years in China. Therefore, in this study, we are going to investigate the effect of DSKT on diabetic fatty liver rats induced by a high-fat diet and streptozotocin (STZ), and the effects of DSKT on silent mating type information regulation 2 homolog 1 (SIRT1) and nuclear factor kappa B (NF-kappaB).

METHODS

Diabetic fatty liver rat model was selected to establish a high-fat diet and STZ. Sixty Wistar rats were divided into six groups (n = 10): control group, high-fat diet + STZ group, simvastatin treatment group, DSKT low dose, medial dose and high dose treatment groups. After 8 weeks of drug intervention, body and liver weights, blood chemistry, blood glucose and insulin were examined. The expressions of sirtuin 1 and NF-kappaB in the liver were observed by RT-PCR and immunohistochemistry, respectively.

RESULTS

A high-fat diet increased body, liver weights, and serum cholesterol concentrations. Intraperitoneal injection of STZ increased blood glucose and decreased body weights. DSKT improved them. Homeostasis model assessment-estimated insulin resistance (HOMA-IR) indices were increased in the high-fat diet groups. DSKT improved them too. In histological examinations of the liver, we observed a significant improvement after treatment. Immunostaining expression of NF-kappaB in the liver was improved by DSKT and simvastatin. The mRNA expressions of SIRT1 in the liver were increased by DSKT and simvastatin.

CONCLUSION

We have demonstrated that DSKT is capable of reversing dyslipidemia and insulin resistance induced by a high-fat diet and STZ. High dose DSKT reveals a stronger effect than simvastatin on the expressions of SIRT1 and NF-kappaB. Furthermore, DSKT has shown a strong dose-depended protective effect on diabetic fatty liver.

Cellular senescence and autophagy in the pathogenesis of chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF)

Aging is associated with impairments in homeostasis. Although aging and senescence are not equivalent, the number of senescent cells increases with aging. Cellular senescence plays important roles in tissue repair or remodeling, as well as embryonic development. Autophagy is a process of lysosomal self-degradation that maintains a homeostatic balance between the synthesis, degradation, and recycling of cellular proteins. Autophagy diminishes with aging; additionally, accelerated aging can be attributed to reduced autophagy. Cellular senescence has been widely implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD), a disease of accelerated lung aging, presumably by impairing cell repopulation and by aberrant cytokine secretion in the senescence-associated secretory phenotype. The possible participation of autophagy in the pathogenic sequence of COPD has been extensively explored. Although it has been reported that increased autophagy may induce epithelial cell death, an insufficient reserve of autophagy can induce cellular senescence in bronchial epithelial cells of COPD. Furthermore, advanced age is one of the most important risk factors for the development of idiopathic pulmonary fibrosis (IPF). Telomere shortening is found in blood leukocytes and alveolar epithelial cells from patients with IPF. Accelerated senescence of epithelial cells plays a role in IPF pathogenesis by perpetuating abnormal epithelial-mesenchymal interactions. Insufficient autophagy may be an underlying mechanism of accelerated epithelial cell senescence and myofibroblast differentiation in IPF. Herein, we review the molecular mechanisms of cellular senescence and autophagy and summarize the role of cellular senescence and autophagy in both COPD and IPF.

SIRT 1 Overexpression is Associated with Metastasis of Pancreatic Ductal Adenocarcinoma (PDAC) and Promotes Migration and Growth of PDAC Cells

Background

SIRT 1, as a class III histone deacetylase (HDAC), is implicated in the initiation and progression of malignancies. However, the association of SIRT 1 with tumorigenesis or progression of pancreatic ductal adenocarcinoma (PDAC) is not clear.

Material/Methods

In our study we investigated SIRT 1 expression in PDAC samples and evaluated the association of SIRT 1 level with the clinical and pathological characteristics of PDAC patients. We investigated the role of SIRT 1 in the migration and growth of PDAC PANC-1 or BxPC-3 cells using gain-of-function and loss-of-function approach.

Results

We demonstrated that SIRT 1 mRNA level was significantly promoted in intra-tumor tissues compared to peri-tumor tissues of PDAC; and SIRT 1 overexpression was markedly associated with distant or lymph node (LN) metastasis of these PDAC tissues. Moreover, the in vitro wound healing assay demonstrated that SIRT 1 overexpression with lentivirus vector markedly promoted the migration of PANC-1 or BxPC-3 cells, whereas SIRT 1 knockdown using SIRT 1 specific siRNA transfection significantly inhibited the migration of PDAC cells. The colony forming assay confirmed SIRT 1 promotion of the growth of PANC-1 or BxPC-3 cells.

Conclusions

In summary, SIRT 1 overexpression is significantly associated with metastasis of PDAC, and overexpressed SIRT 1 plays an important role in pancreatic cancer cell migration and growth. Our data warrants further studies on SIRT 1 as a novel chemotherapeutic target in PDAC.

Conditioned Medium from Early-Outgrowth Bone Marrow Cells Is Retinal Protective in Experimental Model of Diabetes

Bone marrow-derived cells were demonstrated to improve organ function, but the lack of cell retention within injured organs suggests that the protective effects are due to factors released by the cells. Herein, we tested cell therapy using early outgrowth cells (EOCs) or their conditioned media (CM) to protect the retina of diabetic animal models (type 1 and type 2) and assessed the mechanisms by in vitro study. Control and diabetic (db/db) mice (8 weeks of age) were randomized to receive a unique intravenous injection of 5×10⁵EOCs or 0.25 ml thrice weekly tail-vein injections of 10x concentrated CM and Wystar Kyoto rats rendered diabetic were randomized to receive 0.50 ml thrice weekly tail-vein injections of 10x concentrated CM. Four weeks later, the animals were euthanized and the eyes were enucleated. Rat retinal Müller cells (rMCs) were exposed for 24 h to high glucose (HG), combined or not with EOC-conditioned medium (EOC-CM) from db/m EOC cultures. Diabetic animals showed increase in diabetic retinopathy (DR) and oxidative damage markers; the treatment with EOCs or CM infusions significantly reduced this damage and re-established the retinal function. In rMCs exposed to diabetic milieu conditions (HG), the presence of EOC-CM reduced reactive oxygen species production by modulating the NADPH-oxidase 4 system, thus upregulating SIRT1 activity and deacetylating Lys-310-p65-NFκB, decreasing GFAP and VEGF expressions. The antioxidant capacity of EOC-CM led to the prevention of carbonylation and nitrosylation posttranslational modifications on the SIRT1 molecule, preserving its activity. The pivotal role of SIRT1 on the mode of action of EOCs or their CM was also demonstrated on diabetic retina. These findings suggest that EOCs are effective as a form of systemic delivery for preventing the early molecular markers of DR and its conditioned medium is equally protective revealing a novel possibility for cell-free therapy for the treatment of DR.

Alteration of Aging-Dependent MicroRNAs in Idiopathic Pulmonary Fibrosis

Preclinical Research Idiopathic Pulmonary Fibrosis (IPF) is the most severe fibrotic lung disease and characterized by the accumulation of (myo)fibroblasts and collagen within the alveolar wall resulting in obliteration of the gas-exchange surface. Although the detailed pathogenesis is not understood, recent studies have found that several microRNAs (miRNAs) are associated with the progression of lung diseases including IPF. IPF is a fibrotic disease and, most frequently found in an aged population. In this review, the functional roles of miRNAs that are deregulated in IPF progression are discussed together with how aging affects the miRNA signature, altering the fibroblast phenotype and promoting lung fibrosis. Finally, the possibility of targeting miRNAs as a therapeutic approach for the treatment of IPF is discussed.

Effect of Nasal CPAP on SIRT1 and Endothelial Function in Obstructive Sleep Apnea Syndrome

BACKGROUND

Sirtuin 1 (SIRT1), a histone/protein deacetylase, has been implicated in aging, metabolism, and stress resistance. SIRT1 regulates endothelial nitric oxide (NO) synthase, restores NO availability, and is involved in different aspects of cardiovascular disease. The aim of this study was to evaluate any abnormalities with regard to SIRT1 protein level in the blood, SIRT1 activity, and impaired endothelial function in patients with obstructive sleep apnea syndrome (OSAS). We also investigated whether or not OSAS patients who received nasal continuous positive airway pressure (CPAP) treatment showed improvements in the levels of SIRT1.

METHODS

Thirty-five patients with moderately severe to severe OSAS who requested nasal CPAP treatment and 20 healthy controls were prospectively enrolled. The SIRT1 protein levels in blood and its activity, and the serum levels of nitric oxide derivative (NO x ) were assessed. All subjects participated in sleep studies, which were repeated 3 months after nasal CPAP treatment in the patients with OSAS.

RESULTS

In the patients with OSAS, the level of SIRT1 in the blood, its activity, and that of NO x was lower than those of normal subjects before nasal CPAP treatment. After nasal CPAP treatment, the level of SIRT1 in the blood and its activity increased from 0.55 ± 0.32 pg/μg of total protein and 3085.53 ± 1071.57 arbitrary fluorescence units (AFUs)/μg of total protein to 1.13 ± 0.43 pg/μg of total protein and 5344.65 ± 1579.71 AFUs/μg of total protein. The serum levels of NO x in the patients with OSAS increased from 16.36 ± 5.78 to 25.94 ± 5.17 µM.

CONCLUSIONS

Successful treatment for OSAS with nasal CPAP can restore blood levels of the SIRT1 protein and its activity and serum levels of NO x .

Sirtuins, aging, and cardiovascular risks

The sirtuins comprise a highly conserved family proteins present in virtually all species from bacteria to mammals. Sirtuins are members of the highly conserved class III histone deacetylases, and seven sirtuin genes (sirtuins 1-7) have been identified and characterized in mammals. Sirtuin activity is linked to metabolic control, apoptosis, cell survival, development, inflammation, and healthy aging. In this review, we summarize and discuss the potential mutual relations between each sirtuin and cardiovascular health and the impact of sirtuins on oxidative stress and so age-related cardiovascular disorders, underlining the possibility that sirtuins will be novel targets to contrast cardiovascular risks induced by aging.

Interleukin-13 interferes with activation-induced t-cell apoptosis by repressing p53 expression

The etiology and the underlying mechanism of CD4(+) T-cell polarization are unclear. This study sought to investigate the mechanism by which interleukin (IL)-13 prevents the activation-induced apoptosis of CD4(+) T cells. Here we report that CD4(+) T cells expressed IL-13 receptor α2 in the intestine of sensitized mice. IL-13 suppressed both the activation-induced apoptosis of CD4(+) T cells and the expression of p53 and FasL. Exposure to recombinant IL-13 inhibited activation-induced cell death (AICD) along with the expression of p53, caspase 3, and tumor necrosis factor-α in CD4(+) T cells. Administration of an anti-IL-13 antibody enhanced the effect of specific immunotherapy on allergic inflammation in the mouse intestine, enforced the expression of p53 in intestinal CD4(+) T cells, and enhanced the frequency of CD4(+) T-cell apoptosis upon challenge with specific antigens. In summary, blocking IL-13 enhances the therapeutic effect of antigen-specific immunotherapy by regulating apoptosis and thereby enforcing AICD in CD4(+) T cells.

Dysfunction of endothelial progenitor cells from smokers and chronic obstructive pulmonary disease patients due to increased DNA damage and senescence

Cardiovascular disease (CVD) is a major cause of death in smokers, particularly in those with chronic obstructive pulmonary disease (COPD). Circulating endothelial progenitor cells (EPC) are required for endothelial homeostasis, and their dysfunction contributes to CVD. To investigate EPC dysfunction in smokers, we isolated and expanded blood outgrowth endothelial cells (BOEC) from peripheral blood samples from healthy nonsmokers, healthy smokers, and COPD patients. BOEC from smokers and COPD patients showed increased DNA double-strand breaks and senescence compared to nonsmokers. Senescence negatively correlated with the expression and activity of sirtuin-1 (SIRT1), a protein deacetylase that protects against DNA damage and cellular senescence. Inhibition of DNA damage response by silencing of ataxia telangiectasia mutated (ATM) kinase resulted in upregulation of SIRT1 expression and decreased senescence. Treatment of BOEC from COPD patients with the SIRT1 activator resveratrol or an ATM inhibitor (KU-55933) also rescued the senescent phenotype. Using an in vivo mouse model of angiogenesis, we demonstrated that senescent BOEC from COPD patients are dysfunctional, displaying impaired angiogenic ability and increased apoptosis compared to cells from healthy nonsmokers. Therefore, this study identifies epigenetic regulation of DNA damage and senescence as pathogenetic mechanisms linked to endothelial progenitors' dysfunction in smokers and COPD patients. These defects may contribute to vascular disease and cardiovascular events in smokers and could therefore constitute therapeutic targets for intervention.

Protective effects of resveratrol on postmenopausal osteoporosis: regulation of SIRT1-NF-κB signaling pathway

Postmenopausal osteoporosis severely jeopardizes human health. Seeking for therapeutic drugs without side effects is of great necessity. Our study was designed to investigate whether resveratrol, an agonist of SIRT1, could have favorable effect on osteoporosis and to explore the underlying mechanisms. Rat osteoporosis model (ovariectomy group, OVX) was established by bilateral ovariectomy. Three different doses of resveratrol were used: 5 mg/kg/d (low-dosed, RES(LD)), 25 mg/kg/d (medium-dosed, RES(MD)), and 45 mg/kg/d (high-dosed, RES(HD)). Results showed that RES(LD) did not show any significant effect on OVX alterations, while RES(MD) and RES(HD) significantly elevated the decreased bone mineral density induced by osteoporosis (RES(MD) 0.205 ± 0.023, RES(HD) 0.214 ± 0.053 vs. OVX 0.165 ± 0.050 g/cm(2) respectively; P < 0.05). Serum markers alkaline phosphatase (ALP) and osteocalcin were moderately restored by resveratrol. Moreover, resveratrol improved bone structure in OVX rats, demonstrated by hematoxylin-eosin staining and micro-computed tomographic results. In vitro results revealed that resveratrol promoted osteoblast differentiation of bone marrow mesenchymal stromal cells, evidenced by the increase of ALP generation and mRNA expression of collagen 1 (P < 0.05; RES(MD), RES(HD) vs. control group). SIRT1 gene silencing by siRNA transfection blocked these beneficial effects of resveratrol (P < 0.05; RES + SIRT1(KD) vs. RES(HD)). Western blot results showed that resveratrol activated SIRT1 and subsequently suppressed the activity of NF-κB with decreased expression level of p-IκBα and NF-κB p65 (P < 0.05). Our findings verified the effects of specific dosed resveratrol on postmenopausal osteoporosis through osteoblast differentiation via SIRT1-NF-κB signaling pathway. This study suggested the therapeutic potential of resveratrol against osteoporosis and stressed the importance of effective doses.

Resveratrol exerts an anti-apoptotic effect on human bronchial epithelial cells undergoing cigarette smoke exposure

Cigarette smoke can cause endoplasmic reticulum stress and induce apoptosis, both of which are important pathogenic factors contributing to chronic obstructive pulmonary disease. The aim of the present study was to produce a cigarette smoke extract (CSE)-induced apoptosis human bronchial epithelial cell (HBEpC) model, to investigate the protective effects of resveratrol (RES). The role of oxygen-regulated protein 150 (ORP150) in the RES-induced activation of Sirtuin 1 (SIRT1) was additionally studied. Cultured HBEpCs were initially treated with CSE to induce apoptosis, followed by an incubation either with or without RES. Numerous techniques were used to evaluate the outcomes of the present study, including cell counting kit-8 assay, quantitative polymerase chain reaction, western blotting, Hoechst 33342 staining and AnnexinV-PI flow cytometry apoptosis analyses, and gene knockdown. It was identified that 24 h 2% CSE incubation induced apoptosis in HBEpC, accompanied by an overexpression of the apoptosis molecular markers CCAAT-enhancer-binding protein homologous protein, caspase 4 and caspase 3. Pre-treatment of the cells with RES markedly alleviated the severity of apoptosis, as confirmed by apoptosis analyses and the expression levels of the apoptosis molecular markers. SIRT1 was shown to be overexpressed following RES treatment. However, following the gene knockdown of ORP150, the anti-apoptotic effects of RES were significantly attenuated. The results of the present study demonstrate that RES may have a protective effect against CSE-induced apoptosis, and a molecular pathway involving SIRT1 and ORP150 may be associated with the anti-apoptotic functions of RES in HBEpC.

Sirtuin gene polymorphisms are associated with chronic obstructive pulmonary disease in patients in Muğla province

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is an irreversible progressive chronic inflammatory disease that causes shortness of breath in consequence of a decrease in pulmonary functions. The pulmonary inflammatory pathogenesis is multifactorial. We have too little up-to-date information about the relation between COPD and genetics. In our study, the relation with the SIRT1 gene's mononucleotide polymorphisms (SNP) rs7895833, rs7069102 and rs2273773 was analyzed through various laboratory data.

MATERIAL AND METHODS

One hundred COPD patients from the archive records of the Chest Diseases Department of Muğla Sitki Kocman University Medical Faculty were included in the study. A control group was constituted from 100 healthy individuals who live in the same geographical region. The SIRT1 genotypes for these patients were determined using polymerase chain reaction (PCR) and confronting two-pair primers (CTPP) methods. The SIRT1 gene polymorphisms rs7895833, rs7069102 and rs2273773 were analyzed. GG, AG, AA genotypes and G and A alleles of rs7895833, TT, TC, CC genotypes and T and C alleles of rs2273773, and CC, CG, GG genotypes and C and G alleles of rs7069102 were examined. The data in both groups were compared.

CONCLUSIONS

A significant difference between GG, AG and AA genotypes of rs7895833 was found. Especially, the AG genotype was observed more in the group with COPD, with a significant difference. A significant difference between TT, TC and CC genotypes of rs2273773 was found. There was a significant difference between two groups with regards to C and G alleles of rs7069102. A significant difference was not found between the groups with regards to G and A alleles of rs7895833. A difference was not found for both groups between T and C alleles of rs2273773. It shows that these polymorphisms of the SIRT1 gene may be associated with COPD.

Celecoxib sensitizes Staphylococcus aureus to antibiotics in macrophages by modulating SIRT1

We have previously shown that celecoxib in combination with an antibiotic, increase the bacterial sensitivity to antibiotics. However, the underlying molecular mechanism remained elusive. Efficacy of the combinatorial treatment of celecoxib and ampicillin in vitro was evaluated on macrophage-phagocytosed S. aureus. To elucidate the mechanism, signaling pathway of infection and inflammation involving TLR2, JNK, SIRT1 and NF-κB was studied by FACS, Western blot, ELISA and activity assays. Combinatorial treatment of ampicillin and celecoxib reduced the bacterial load in the macrophages. Further studies clearly suggested the activation of the master regulator of oxidative stress and inflammation SIRT1, by celecoxib when used alone and/or in combination with ampicillin. Also, the results indicated that celecoxib inhibited JNK phosphorylation thereby stabilizing and activating SIRT1 protein that inhibited the COX-2 gene transcription with a significant decrease in the levels of protein inflammatory cytokines like IL-6, MIP-1α and IL-1β via inhibition of NF-κB. SIRT1 activation by celecoxib also resulted in increase of catalase and peroxidase activity with a decrease in Nitric oxide levels. In conclusion, we demonstrate a novel role of celecoxib in controlling inflammation as an enhancer of antibiotic activity against bacteria by modulating SIRT1.

Age-related activation of MKK/p38/NF-κB signaling pathway in lung: from mouse to human

We and others previously reported that the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 significantly accumulate with age in mouse lung. This is accompanied by elevated phosphorylation of p38. Here, we further investigate whether aging affects activation of p38 signaling and the inflammatory reaction after exposure to lipopolysaccharide (LPS) in the lungs of mice in vivo and humans ex vivo. The data showed that activation of p38 peaked at 0.5h and then rapidly declined in young (2-month-old) mouse lung, after intranasal inhalation challenge with LPS. In contract, activation of p38 peaked at 24h and was sustained longer in aged (20-month-old) mice. As well as altered p38, activations of its upstream activator MKK and downstream substrate NF-κB were also changed in the lungs of aged mice, which corresponded with the absence in the early phase but delayed increases in concentrations of TNF-α, IL-1β and IL-6. Consistent with the above observations in mice, similar patterns of p38 signaling also occurred in human lungs. Compared with younger lungs from adult-middle aged subjects, the activation of p38, MKK and NF-κB, as well as the production of pro-inflammatory cytokines were significantly increased in the lungs of older subjects ex vivo. Exposure of human lung cells to LPS induced rapid activation of p38, MKK and NF-κB in these cells from adult-middle aged subjects, but not older subjects, with increases in the production of the pro-inflammatory cytokines. The LPS-induced rapid activation in the lung cells from adult-middle aged subjects occurred as early as 0.25h after exposure, and then declined. Compared with adult-middle aged subjects, the LPS exposure did not induce marked changes in the early phase, either in the activation of p38, MKK and NF-κB, or in the production of TNF-α, IL-1β or IL-6 in the lung cells from older subjects. In contrast, these changes occurred relatively late, peaked at 16h and were sustained longer in the lungs of older subjects. These data support the hypothesis that the sustained activation of the p38 signaling pathway at baseline and the absence in the early phase but delayed of p38 signaling pathway response to LPS in the elderly may play important roles in increased susceptibility of aged lungs to inflammatory injury.

SIRT1 protects against cigarette smoke-induced lung oxidative stress via a FOXO3-dependent mechanism

Oxidative and carbonyl stress is increased in lungs of smokers and patients with chronic obstructive pulmonary disease (COPD), as well as in cigarette smoke (CS)-exposed rodent lungs. We previously showed that sirtuin1 (SIRT1), an antiaging protein, is reduced in lungs of CS-exposed mice and patients with COPD and that SIRT1 attenuates CS-induced lung inflammation and injury. It is not clear whether SIRT1 protects against CS-induced lung oxidative stress. Therefore, we determined the effect of SIRT1 on lung oxidative stress and antioxidants in response to CS exposure using loss- and gain-of-function approaches, as well as a pharmacological SIRT1 activation by SRT1720. We found that CS exposure increased protein oxidation and lipid peroxidation in lungs of wild-type (WT) mice, which was further augmented in SIRT1-deficient mice. Furthermore, both SIRT1 genetic overexpression and SRT1720 treatment significantly decreased oxidative stress induced by CS exposure. FOXO3 deletion augmented lipid peroxidation products but reduced antioxidants in response to CS exposure, which was not affected by SRT1720. Interestingly, SRT1720 treatment exhibited a similar effect on lipid peroxidation and antioxidants (i.e., manganese superoxide dismutase, heme oxygenase-1, and NADPH quinone oxidoreductase-1) in WT and nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-deficient mice in response to CS exposure. This indicates that SIRT1 protects against CS-induced oxidative stress, which is mediated by FOXO3, but is independent of Nrf2. Overall, these findings reveal a novel function of SIRT1, which is to reduce CS-induced oxidative stress, and this may contribute to its protective effects against lung inflammation and subsequent development of COPD.

Melatonin and the theories of aging: a critical appraisal of melatonin's role in antiaging mechanisms

The classic theories of aging such as the free radical theory, including its mitochondria-related versions, have largely focused on a few specific processes of senescence. Meanwhile, numerous interconnections have become apparent between age-dependent changes previously thought to proceed more or less independently. Increased damage by free radicals is not only linked to impairments of mitochondrial function, but also to inflammaging as it occurs during immune remodeling and by release of proinflammatory cytokines from mitotically arrested, DNA-damaged cells that exhibit the senescence-associated secretory phenotype (SASP). Among other effects, SASP can cause mutations in stem cells that reduce the capacity for tissue regeneration or, in worst case, lead to cancer stem cells. Oxidative stress has also been shown to promote telomere attrition. Moreover, damage by free radicals is connected to impaired circadian rhythmicity. Another nexus exists between cellular oscillators and metabolic sensing, in particular to the aging-suppressor SIRT1, which acts as an accessory clock protein. Melatonin, being a highly pleiotropic regulator molecule, interacts directly or indirectly with all the processes mentioned. These influences are critically reviewed, with emphasis on data from aged organisms and senescence-accelerated animals. The sometimes-controversial findings obtained either in a nongerontological context or in comparisons of tumor with nontumor cells are discussed in light of evidence obtained in senescent organisms. Although, in mammals, lifetime extension by melatonin has been rarely documented in a fully conclusive way, a support of healthy aging has been observed in rodents and is highly likely in humans.

Evaluation of DNA damage in COPD patients and its correlation with polymorphisms in repair genes

BACKGROUND

We investigated a potential link between genetic polymorphisms in genes XRCC1 (Arg399Gln), OGG1 (Ser326Cys), XRCC3 (Thr241Met), and XRCC4 (Ile401Thr) with the level of DNA damage and repair, accessed by comet and micronucleus test, in 51 COPD patients and 51 controls.

METHODS

Peripheral blood was used to perform the alkaline and neutral comet assay; and genetic polymorphisms by PCR/RFLP. To assess the susceptibility to exogenous DNA damage, the cells were treated with methyl methanesulphonate for 1-h or 3-h. After 3-h treatment the % residual damage was calculated assuming the value of 1-h treatment as 100%. The cytogenetic damage was evaluated by buccal micronucleus cytome assay (BMCyt).

RESULTS

COPD patients with the risk allele XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) showed higher DNA damage by comet assay. The residual damage was higher for COPD with risk allele in the four genes. In COPD patients was showed negative correlation between BMCyt (binucleated, nuclear bud, condensed chromatin and karyorrhexic cells) with pulmonary function and some variant genotypes.

CONCLUSION

Our results suggest a possible association between variant genotypes in XRCC1 (Arg399Gln), OGG1 (Ser326Cys), XRCC3 (Thr241Met), and XRCC4 (Ile401Thr), DNA damage and progression of COPD.

Premature lung aging and cellular senescence in the pathogenesis of idiopathic pulmonary fibrosis and COPD/emphysema

Different anatomic and physiological changes occur in the lung of aging people that can affect pulmonary functions, and different pulmonary diseases, including deadly diseases such as chronic obstructive pulmonary disease (COPD)/emphysema and idiopathic pulmonary fibrosis (IPF), can be related to an acceleration of the aging process. The individual genetic background, as well as exposure to a variety of toxic substances (cigarette smoke in primis) can contribute significantly to accelerating pulmonary senescence. Premature aging can impair lung function by different ways: by interfering specifically with tissue repair mechanisms after damage, thus perturbing the correct crosstalk between mesenchymal and epithelial components; by inducing systemic and/or local alteration of the immune system, thus impairing the complex mechanisms of lung defense against infections; and by stimulating a local and/or systemic inflammatory condition (inflammaging). According to recently proposed pathogenic models in COPD and IPF, premature cellular senescence likely affects distinct progenitors cells (mesenchymal stem cells in COPD, alveolar epithelial precursors in IPF), leading to stem cell exhaustion. In this review, the large amount of data supporting this pathogenic view are discussed, with emphasis on the possible molecular and cellular mechanisms leading to the severe parenchymal remodeling that characterizes, in different ways, these deadly diseases.

Redox regulation of SIRT1 in inflammation and cellular senescence

Sirtuin 1 (SIRT1) regulates inflammation, aging (life span and health span), calorie restriction/energetics, mitochondrial biogenesis, stress resistance, cellular senescence, endothelial functions, apoptosis/autophagy, and circadian rhythms through deacetylation of transcription factors and histones. SIRT1 level and activity are decreased in chronic inflammatory conditions and aging, in which oxidative stress occurs. SIRT1 is regulated by a NAD(+)-dependent DNA repair enzyme, poly(ADP-ribose) polymerase-1 (PARP1), and subsequent NAD(+) depletion by oxidative stress may have consequent effects on inflammatory and stress responses as well as cellular senescence. SIRT1 has been shown to undergo covalent oxidative modifications by cigarette smoke-derived oxidants/aldehydes, leading to posttranslational modifications, inactivation, and protein degradation. Furthermore, oxidant/carbonyl stress-mediated reduction of SIRT1 leads to the loss of its control on acetylation of target proteins including p53, RelA/p65, and FOXO3, thereby enhancing the inflammatory, prosenescent, and apoptotic responses, as well as endothelial dysfunction. In this review, the mechanisms of cigarette smoke/oxidant-mediated redox posttranslational modifications of SIRT1 and its roles in PARP1 and NF-κB activation, and FOXO3 and eNOS regulation, as well as chromatin remodeling/histone modifications during inflammaging, are discussed. Furthermore, we have also discussed various novel ways to activate SIRT1 either directly or indirectly, which may have therapeutic potential in attenuating inflammation and premature senescence involved in chronic lung diseases.

Potential mechanisms linking atherosclerosis and increased cardiovascular risk in COPD: focus on Sirtuins

The development of atherosclerosis is a multi-step process, at least in part controlled by the vascular endothelium function. Observations in humans and experimental models of atherosclerosis have identified monocyte recruitment as an early event in atherogenesis. Chronic inflammation is associated with ageing and its related diseases (e.g., atherosclerosis and chronic obstructive pulmonary disease). Recently it has been discovered that Sirtuins (NAD⁺-dependent deacetylases) represent a pivotal regulator of longevity and health. They appear to have a prominent role in vascular biology and regulate aspects of age-dependent atherosclerosis. Many studies demonstrate that SIRT1 exhibits anti-inflammatory properties in vitro (e.g., fatty acid-induced inflammation), in vivo (e.g., atherosclerosis, sustainment of normal immune function in knock-out mice) and in clinical studies (e.g., patients with chronic obstructive pulmonary disease). Because of a significant reduction of SIRT1 in rodent lungs exposed to cigarette smoke and in lungs of patients with chronic obstructive pulmonary disease (COPD), activation of SIRT1 may be a potential target for chronic obstructive pulmonary disease therapy. We review the inflammatory mechanisms involved in COPD-CVD coexistence and the potential role of SIRT1 in the regulation of these systems.

Oxidative stress and chromatin remodeling in chronic obstructive pulmonary disease and smoking-related diseases

SIGNIFICANCE

Chronic obstructive pulmonary disease (COPD) is predominantly a tobacco smoke-triggered disease with features of chronic low-grade systemic inflammation and aging (inflammaging) of the lung associated with steroid resistance induced by cigarette smoke (CS)-mediated oxidative stress. Oxidative stress induces various kinase signaling pathways leading to chromatin modifications (histone acetylation/deacetylation and histone methylation/demethylation) in inflammation, senescence, and steroid resistance.

RECENT ADVANCES

Histone mono-, di-, or tri-methylation at lysine residues result in either gene activation (H3K4, H3K36, and H3K79) or repression (H3K9, H3K27, and H3K20). Cross-talk occurs between various epigenetic marks on histones and DNA methylation. Both CS and oxidants alter histone acetylation/deacetylation and methylation/demethylation leading to enhanced proinflammatory gene expression. Chromatin modifications occur in lungs of patients with COPD. Histone deacetylase 2 (HDAC2) reduction (levels and activity) is associated with steroid resistance in response to oxidative stress.

CRITICAL ISSUES

Histone modifications are associated with DNA damage/repair and epigenomic instability as well as premature lung aging, which have implications in the pathogenesis of COPD. HDAC2/SIRTUIN1 (SIRT1)-dependent chromatin modifications are associated with DNA damage-induced inflammation and senescence in response to CS-mediated oxidative stress.

FUTURE DIRECTIONS

Understanding CS/oxidative stress-mediated chromatin modifications and the cross-talk between histone acetylation and methylation will demonstrate the involvement of epigenetic regulation of chromatin remodeling in inflammaging. This will lead to identification of novel epigenetic-based therapies against COPD and other smoking-related lung diseases. Pharmacological activation of HDAC2/SIRT1 or reversal of their oxidative post-translational modifications may offer therapies for treatment of COPD and CS-related diseases based on epigenetic histone modifications.

Targeting class I histone deacetylases in cancer therapy

INTRODUCTION

Class I histone deacetylases (HDACs) are often overexpressed in cancer, and their inhibition typically leads cancer cells, but not normal cells, to apoptosis. Hence, the field of cancer therapy has experienced a continued surge in the development of HDAC inhibitors.

AREAS COVERED

Class I comprises of HDAC1, 2, 3 and 8. HDAC1, 2 and 3 are active as subunits of multiprotein complexes while an HDAC8 complex has not been identified. Besides being a major contributor to poor prognosis in childhood neuroblastoma, little is known of HDAC8 functions and substrates. The targeting and activities of HDAC1 - 3 are modulated by post-translational modifications and association with numerous proteins. The composition of the various HDAC complexes is cell type dependent and fluctuates with intra- and intercellular stimuli. These HDAC complexes play roles at multiple levels in gene expression and genome stability. The application of isoform-specific HDAC inhibitors has met with varying success in clinical trials.

EXPERT OPINION

To elucidate the mechanism and cellular impact of HDAC inhibitors, we need to identify the spectrum of class I HDAC complexes and their functions. In the cases of HDAC1 - 3, selectivity of HDAC inhibitors should be directed against relevant complexes. HDAC8 active site unique features facilitate the design of selective inhibitors.

Strategies to decrease ongoing oxidant burden in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity globally, and its development is mainly associated with tobacco/biomass smoke-induced oxidative stress. Hence, targeting systemic and local oxidative stress with agents that can balance the antioxidant/redox system can be expected to be useful in the treatment of COPD. Preclinical and clinical trials have revealed that antioxidants/redox modulators can detoxify free radicals and oxidants, control expression of redox and glutathione biosynthesis genes, chromatin remodeling and inflammatory gene expression; and are especially useful in preventing COPD exacerbations. In this review, various novel approaches and problems associated with these approaches in COPD are reviewed.

Perspectives on translational and therapeutic aspects of SIRT1 in inflammaging and senescence

Sirtuin1 (SIRT1), a type III protein deacetylase, is considered as a novel anti-aging protein involved in regulation of cellular senescence/aging and inflammation. SIRT1 level and activity are decreased during lung inflammaging caused by oxidative stress. The mechanism of SIRT1-mediated protection against inflammaging is associated with the regulation of inflammation, premature senescence, telomere attrition, senescence associated secretory phenotype, and DNA damage response. A variety of dietary polyphenols and pharmacological activators are shown to regulate SIRT1 so as to intervene the progression of type 2 diabetes, cancer, cardiovascular diseases, and chronic obstructive pulmonary disease associated with inflammaging. However, recent studies have shown the non-specific regulation of SIRT1 by the aforementioned pharmacological activators and polyphenols. In this perspective, we have briefly discussed the role of SIRT1 in regulation of cellular senescence and its associated secretory phenotype, DNA damage response, particularly in lung inflammaging and during the development of chronic obstructive pulmonary diseases. We have also discussed the potential directions for future translational therapeutic avenues for SIRT1 in modulating lung inflammaging associated with senescence in chronic lung diseases associated with increased oxidative stress.

SIRT1 protects against emphysema via FOXO3-mediated reduction of premature senescence in mice

Chronic obstructive pulmonary disease/emphysema (COPD/emphysema) is characterized by chronic inflammation and premature lung aging. Anti-aging sirtuin 1 (SIRT1), a NAD+-dependent protein/histone deacetylase, is reduced in lungs of patients with COPD. However, the molecular signals underlying the premature aging in lungs, and whether SIRT1 protects against cellular senescence and various pathophysiological alterations in emphysema, remain unknown. Here, we showed increased cellular senescence in lungs of COPD patients. SIRT1 activation by both genetic overexpression and a selective pharmacological activator, SRT1720, attenuated stress-induced premature cellular senescence and protected against emphysema induced by cigarette smoke and elastase in mice. Ablation of Sirt1 in airway epithelium, but not in myeloid cells, aggravated airspace enlargement, impaired lung function, and reduced exercise tolerance. These effects were due to the ability of SIRT1 to deacetylate the FOXO3 transcription factor, since Foxo3 deficiency diminished the protective effect of SRT1720 on cellular senescence and emphysematous changes. Inhibition of lung inflammation by an NF-κB/IKK2 inhibitor did not have any beneficial effect on emphysema. Thus, SIRT1 protects against emphysema through FOXO3-mediated reduction of cellular senescence, independently of inflammation. Activation of SIRT1 may be an attractive therapeutic strategy in COPD/emphysema.