SIRT6 protects human endothelial cells from DNA damage, telomere dysfunction, and senescence

Senescent endothelial cells: Potential modulators of immunosenescence and ageing

Recent studies have demonstrated that the accumulation of senescent endothelial cells may be the primary cause of cardiovascular diseases. Because of their multifunctional properties, endothelial cells actively take part in stimulating the immune system and inflammation. In addition, ageing is characterized by the progressive deterioration of immune cells and a decline in the activation of the immune response. This results in a loss of the primary function of the immune system, which is eliminating damaged/senescent cells and neutralizing potential sources of harmful inflammatory reactions. In this review, we discuss cellular senescence and the senescence-associated secretory phenotype (SASP) of endothelial cells and summarize the link between endothelial cells and immunosenescence. We describe the possibility that age-related changes in Toll-like receptors (TLRs) and microRNAs can affect the phenotypes of senescent endothelial cells and immune cells via a negative feedback loop aimed at restraining the excessive pro-inflammatory response. This review also addresses the following questions: how do senescent endothelial cells influence ageing or age-related changes in the inflammatory burden; what is the connection between ECs and immunosenescence, and what are the crucial hypothetical pathways linking endothelial cells and the immune system during ageing.

Ergothioneine oxidation in the protection against high-glucose induced endothelial senescence: Involvement of SIRT1 and SIRT6

Ergothioneine (Egt), the betaine of 2-mercapto-L-histidine, is a dietary antioxidant protecting against many diseases, including cardiovascular disease (CVD), through a redox mechanism different from alkylthiols. Here, experiments were designed to evaluate the mechanisms underlying the beneficial effect of Egt against hyperglycaemia-induced senescence in endothelial cells. To this end, cells were incubated with increasing concentrations of Egt (0.01-1.00mM) for 12h followed by incubation for 48h with high-glucose (25mM). Cell evaluation indicated that viability was not affected by mM concentrations of Egt and that the high-glucose cytotoxicity was prevented with the highest efficacy at 0.5mM Egt. The cytoprotective effect of Egt was paralleled by reduced ROS production, cell senescence, and, interestingly, the formation of hercynine (EH), a betaine we recently found to be produced during the Egt oxidation pathway. Notably, the Egt beneficial effect was exerted through the upregulation of sirtuin 1 (SIRT1) and sirtuin 6 (SIRT6) expression and the downregulation of p66Shc and NF-κB. SIRT1 activity inhibition and SIRT6 gene silencing by small interfering RNA abolished the protective effect of Egt against the high-glucose-induced endothelial senescence. These data provide the first evidence of the Egt ability to interfere with endothelial senescence linked to hyperglycaemia through the regulation of SIRT1 and SIRT6 signaling, thus further strengthening the already assessed role of these two histone deacetylases in type 2 diabetes.

From Ancient Pathways to Aging Cells-Connecting Metabolism and Cellular Senescence

Cellular senescence is a complex stress response that permanently arrests the proliferation of cells at risk for oncogenic transformation. However, senescent cells can also drive phenotypes associated with aging. Although the senescence-associated growth arrest prevents the development of cancer, and the metabolism of cancer cells has been studied in depth, the metabolic causes and consequences of cellular senescence were largely unexplored until recently. New findings reveal key roles for several aspects of cellular metabolism in the establishment and control of senescent phenotypes. These discoveries have important implications for both cancer and aging. In this review, we highlight some of the recent links between metabolism and phenotypes that are commonly associated with senescent cells.

Deletion of sirtuin 6 accelerates endothelial dysfunction and atherosclerosis in apolipoprotein E-deficient mice

Sirtuin 6 (SIRT6) is a chromatin-associated deacetylase that plays a leading role in genomic stability and aging. However, the precise role of SIRT6 in atherosclerosis, an aging-associated cardiovascular disease, remains elusive. This study aims at defining the role of SIRT6 in atherosclerotic lesion development. SIRT6 messenger RNA and protein expression are markedly decreased in atherosclerotic aortas of apolipoprotein E-deficient (ApoE(-/-)) mice fed a high-cholesterol diet. SIRT6 was knocked down in ApoE(-/-) mice using small hairpin RNAs (shRNAs) lentivirus injection. SIRT6-shRNA-treated ApoE(-/-) mice showed impaired endothelium-dependent vasodilation, increased plaque size (in aortic sinus, aortic root and en face aorta), and augmented plaque vulnerability (evidenced by increased necrotic core areas and macrophage accumulation and reduced collagen content). At the cellular level, SIRT6 depletion by RNA interference in human umbilical vein endothelial cells significantly increased monocyte adhesion to endothelial cells by inducing the expression of intracellular adhesion molecule-1. Consistently, intracellular adhesion molecule-1 expression was significantly upregulated in aortic endothelium of SIRT6-shRNA-treated ApoE(-/-) mice compared with controls. In sum, the aforementioned findings suggest that SIRT6 is a primary negative regulation factor in endothelial dysfunction and atherosclerosis development. As a result, SIRT6 is a promising therapeutic target for treating atherosclerosis and its cardiovascular complications.

Two tagSNPs rs352493 and rs3760908 within SIRT6 Gene Are Associated with the Severity of Coronary Artery Disease in a Chinese Han Population

SIRT6 has been demonstrated to exert protective effects on endothelial cells and is closely associated with lipid metabolism, glucose metabolism, and obesity, indicating an important role in the pathogenesis and progression of coronary artery disease (CAD). Nonetheless, the biological significance of SIRT6 variants on CAD is far to be elucidated. Here we aimed to investigate the influence of SIRT6 polymorphisms on individual susceptibility and severity of CAD. Multivariate logistic regression analysis exhibited no significant association between these five polymorphisms and CAD risk in the genotype and allele frequencies. However, we found that the rs352493 polymorphism in SIRT6 exhibited a significant effect on the severity of CAD; C allele (χ² = 7.793, adjusted P = 0.013) and the combined CC/CT genotypes (χ² = 5.609, adjusted P = 0.031) presented the greater CAD severity. In addition, A allele (χ² = 5.208, adjusted P = 0.046) and AA (χ² = 4.842, adjusted P = 0.054) of rs3760908 were also associated with greater CAD severity in Chinese subjects. Our data provided the first evidence that SIRT6 tagSNPs rs352493 and rs3760908 play significant roles in the severity of CAD in Chinese Han subjects, which might be useful predictors of the severity of CAD.

Knockdown of SIRT6 Enables Human Bone Marrow Mesenchymal Stem Cell Senescence

Autologous bone marrow mesenchymal stem cell (BM-MSC) transplantation is a novel strategy for treating ischemic heart disease. However, limited benefits have been reported in aging patients. Rejuvenation of aged human BM-MSCs (hBM-MSCs) could be a means to improve the efficacy of stem cell transplantation in older patients. While it has been shown that sirtuin 6 (SIRT6) is an important antiaging factor in various cells, the role of SIRT6 in hBM-MSCs remains unknown. The hBM-MSCs from different ages were cultured for quantifying SIRT6 expression by mRNA and Western blotting. The cell proliferative and migration abilities were evaluated by BrdU staining, cell growth curves, and scratch assay. Senescence-associated β-galactosidase (SA-β-Gal) activity and aging-associated p16 (cyclin-dependent kinase inhibitor 2A) expression were also quantified. The knockdown of SIRT6 in hBM-MSCs was used to investigate its impact on aging. SIRT6 expression increased with age, while the proliferative and migration abilities of aged hBM-MSCs were decreased compared with young cells. Knockdown of SIRT6 impaired the proliferative, migration, and oxidative stress resistance potentials of BM-MSCs. SA-β-Gal activity and p16 expression were increased in aged cells compared with young ones and in siRNA SIRT6 knockdown cells compared with their controls. Aging results in compensatory overexpression of SIRT6 in hBM-MSCs. Downregulation of SIRT6 in these cells resulted in less cell proliferation and migration but increased SA-β-Gal activity and p16 expression. These results suggest that SIRT6 regulates the aging process in hBM-MSCs and could serve as a target for their rejuvenation.

The role of sirtuins in aging and age-related diseases

Sirtuins, initially described as histone deacetylases and gene silencers in yeast, are now known to have much more functions and to be much more abundant in living organisms. Sirtuins gained much attention when they were first acknowledged to be responsible for some beneficial and longevity-promoting effects of calorie restriction in many species of animals - from fruit flies to mammals. In this paper, we discuss some detailed molecular mechanisms of inducing these effects, and wonder if they could be possibly mimicked without actually applying calorie restriction, through induction of sirtuin activity. It is known now that sirtuins, when adjusting the pattern of cellular metabolism to nutrient availability, can regulate many metabolic functions significant from the standpoint of aging research - including DNA repair, genome stability, inflammatory response, apoptosis, cell cycle, and mitochondrial functions. While carrying out these regulations, sirtuins cooperate with many transcription factors, including PGC-1a, NFKB, p53 and FoxO. This paper contains some considerations about possible use of facilitating activity of the sirtuins in prevention of aging, metabolic syndrome, chronic inflammation, and other diseases.

Sequence Variants of SIRT6 Gene Promoter in Myocardial Infarction

AIMS

Coronary artery disease (CAD), including myocardial infarction (MI), is a common complex disease caused by atherosclerosis. Although more than 50 genetic variants have been associated with CAD, these loci collectively account for only 10% of CAD cases. Genetic variants of low and rare frequencies have been proposed as the main causes of CAD. SIRT6, one of the highly conserved NAD-dependent class III deacetylases, has been implicated in cardiovascular diseases. Considering the important roles that SIRT6 plays in the cardiovascular system, inflammation, and lipid and cholesterol metabolism, genetic variants were hypothesized to contribute to MI development.

METHODS

The promoter regions of the SIRT6 gene were genetically analyzed in large cohorts of MI patients (n = 371) and ethnically-matched controls (n = 383).

RESULTS

A total of 15 DNA sequence variants (DSVs) were identified, including seven single-nucleotide polymorphisms (SNPs). Two novel heterozygous DSVs, g.4183823G>C and g.4183742G>A, were identified in two MI patients but in none of the controls. Two SNPs, g.4183685T>C (rs4359565) and g.4182942C>A (rs3760905), were found in MI patients with significantly higher frequencies compared with controls.

CONCLUSIONS

These DSVs identified in MI patients may alter the transcriptional activity of the SIRT6 gene promoter and alter SIRT6 levels which might contribute to the risk of MI.

Sirtuins, Cell Senescence, and Vascular Aging

The sirtuins (SIRTs) constitute a class of proteins with nicotinamide adenine dinucleotide-dependent deacetylase or adenosine diphosphate-ribosyltransferase activity. Seven SIRT family members have been identified in mammals, from SIRT1, the best studied for its role in vascular aging, to SIRT7. SIRT1 and SIRT2 are localized in the nucleus and cytoplasm. SIRT3, SIRT4, and SIRT5 are mitochondrial, and SIRT6 and SIRT7 are nuclear. Extensive studies have clearly revealed that SIRT proteins regulate diverse cell functions and responses to stressors. Vascular aging involves the aging process (senescence) of endothelial and vascular smooth muscle cells. Two types of cell senescence have been identified: (1) replicative senescence with telomere attrition; and (2) stress-induced premature senescence without telomere involvement. Both types of senescence induce vascular cell growth arrest and loss of vascular homeostasis, and contribute to the initiation and progression of cardiovascular diseases. Previous mechanistic studies have revealed in detail that SIRT1, SIRT3, and SIRT6 show protective functions against vascular aging, and definite vascular function of other SIRTs is under investigation. Thus, direct SIRT modulation and nicotinamide adenine dinucleotide stimulation of SIRT are promising candidates for cardiovascular disease therapy. A small number of pilot studies have been conducted to assess SIRT modulation in humans. These clinical studies have not yet provided convincing evidence that SIRT proteins alleviate morbidity and mortality in patients with cardiovascular diseases. The outcomes of multiple ongoing clinical trials are awaited to define the efficacy of SIRT modulators and SIRT activators in cardiovascular diseases, along with the potential adverse effects of chronic SIRT modulation.

Overexpression of Sirtuin 6 suppresses cellular senescence and NF-κB mediated inflammatory responses in osteoarthritis development

The aim of our study was to evaluate if Sirt6, a NAD + dependent histone deacetylase, plays a protective role in cartilage degeneration by suppressing cellular senescence and inflammatory responses. The expression level of sirt6 in normal and OA human knee articular cartilage was compared by immunofluorescence and western blotting. The effect of sirt6 overexpression on replicative senescence of chondrocytes and NF-κB target genes expression was evaluated. Histological assessment of OA mice knee joint was carried out to assess the in vivo effects of sirt6 overexpression on mice chondrocytes. We found sirt6 level was significantly decreased in the articular chondrocytes of OA patients compare to normal human. SA-β-gal staining revealed that overexpression of sirt6 suppressed replicative senescence of chondrocytes. Meanwhile, the expression of NF-κB dependent genes were significantly attenuated by sirt6 overxpression. Safranin-O staining and OARSI score of knee joint cartilage in OA mice revealed that Lenti-Sirt6 intraarticular injection could protect mice chondrocytes from degeneration. These data strongly suggest that overexpression of Sirt6 can prevent OA development by reducing both the inflammatory response and chondrocytes senescence. Therefore, the development of specific activators of Sirt6 may have therapeutic potential for the treatment of OA.

Diabetes and ageing-induced vascular inflammation

Diabetes and the ageing process independently increase the risk for cardiovascular disease (CVD). Since incidence of diabetes increases as people get older, the diabetic older adults represent the largest population of diabetic subjects. This group of patients would potentially be threatened by the development of CVD related to both ageing and diabetes. The relationship between CVD, ageing and diabetes is explained by the negative impact of these conditions on vascular function. Functional and clinical evidence supports the role of vascular inflammation induced by the ageing process and by diabetes in vascular impairment and CVD. Inflammatory mechanisms in both aged and diabetic vasculature include pro-inflammatory cytokines, vascular hyperactivation of nuclear factor-кB, increased expression of cyclooxygenase and inducible nitric oxide synthase, imbalanced expression of pro/anti-inflammatory microRNAs, and dysfunctional stress-response systems (sirtuins, Nrf2). In contrast, there are scarce data regarding the interaction of these mechanisms when ageing and diabetes co-exist and its impact on vascular function. Older diabetic animals and humans display higher vascular impairment and CVD risk than those either aged or diabetic, suggesting that chronic low-grade inflammation in ageing creates a vascular environment favouring the mechanisms of vascular damage driven by diabetes. Further research is needed to determine the specific inflammatory mechanisms responsible for exacerbated vascular impairment in older diabetic subjects in order to design effective therapeutic interventions to minimize the impact of vascular inflammation. This would help to prevent or delay CVD and the specific clinical manifestations (cognitive decline, frailty and disability) promoted by diabetes-induced vascular impairment in the elderly.

Changes in Regenerative Capacity through Lifespan

Most organisms experience changes in regenerative abilities through their lifespan. During aging, numerous tissues exhibit a progressive decline in homeostasis and regeneration that results in tissue degeneration, malfunction and pathology. The mechanisms responsible for this decay are both cell intrinsic, such as cellular senescence, as well as cell-extrinsic, such as changes in the regenerative environment. Understanding how these mechanisms impact on regenerative processes is essential to devise therapeutic approaches to improve tissue regeneration and extend healthspan. This review offers an overview of how regenerative abilities change through lifespan in various organisms, the factors that underlie such changes and the avenues for therapeutic intervention. It focuses on established models of mammalian regeneration as well as on models in which regenerative abilities do not decline with age, as these can deliver valuable insights for our understanding of the interplay between regeneration and aging.

Bioactive Compounds Isolated from Microalgae in Chronic Inflammation and Cancer

The risk of onset of cancer is influenced by poorly controlled chronic inflammatory processes. Inflammatory diseases related to cancer development include inflammatory bowel disease, which can lead to colon cancer, or actinic keratosis, associated with chronic exposure to ultraviolet light, which can progress to squamous cell carcinoma. Chronic inflammatory states expose these patients to a number of signals with tumorigenic effects, including nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPK) activation, pro-inflammatory cytokines and prostaglandins release and ROS production. In addition, the participation of inflammasomes, autophagy and sirtuins has been demonstrated in pathological processes such as inflammation and cancer. Chemoprevention consists in the use of drugs, vitamins, or nutritional supplements to reduce the risk of developing or having a recurrence of cancer. Numerous in vitro and animal studies have established the potential colon and skin cancer chemopreventive properties of substances from marine environment, including microalgae species and their products (carotenoids, fatty acids, glycolipids, polysaccharides and proteins). This review summarizes the main mechanisms of actions of these compounds in the chemoprevention of these cancers. These actions include suppression of cell proliferation, induction of apoptosis, stimulation of antimetastatic and antiangiogenic responses and increased antioxidant and anti-inflammatory activity.

Sirtuin-6 deficiency exacerbates diabetes-induced impairment of wound healing

Delayed wound healing is one of the major complications in diabetes and is characterized by chronic proinflammatory response, and abnormalities in angiogenesis and collagen deposition. Sirtuin family proteins regulate numerous pathophysiological processes, including those involved in promotion of longevity, DNA repair, glycolysis and inflammation. However, the role of sirtuin 6 (SIRT6), a NAD+-dependent nuclear deacetylase, in wound healing specifically under diabetic condition remains unclear. To analyse the role of SIRT6 in cutaneous wound healing, paired 6-mm stented wound was created in diabetic db/db mice and injected siRNA against SIRT6 in the wound margins (transfection agent alone and nonsense siRNA served as controls). Wound time to closure was assessed by digital planimetry, and wounds were harvested for histology, immunohistochemistry and Western blotting. SIRT6-siRNA-treated diabetic wound showed impaired healing, which was associated with reduced capillary density (CD31-staining vessels) when compared to control treatment. Interestingly, SIRT6 deficiency decreased vascular endothelial growth factor expression and proliferation markers in the wounds. Furthermore, SIRT6 ablation in diabetic wound promotes nuclear factor-κB (NF-κB) activation resulting in increased expression of proinflammatory markers (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, tumor necrosis factor-α and interleukin-1β) and increased oxidative stress. Collectively, our findings demonstrate that loss of SIRT6 in cutaneous wound aggravates proinflammatory response by increasing NF-κB activation, oxidative stress and decrease in angiogenesis in the diabetic mice. Based on these findings, we speculate that the activation of SIRT6 signalling might be a potential therapeutic approach for promoting wound healing in diabetics.

Depletion of SIRT6 causes cellular senescence, DNA damage, and telomere dysfunction in human chondrocytes

OBJECTIVE

SIRT6, a member of the sirtuin family of nicotinamide adenine dinucleotide (NAD(+))-dependent protein deacetylases, has been implicated as a key factor in aging-related diseases. However, the role of SIRT6 in chondrocytes has not been fully explored. The purpose of this study was to examine the role of SIRT6 in human chondrocytes by inhibiting SIRT6 in vitro.

DESIGN

First, the localization of SIRT6 and proliferation cell nuclear antigen (PCNA) in human cartilages was examined by immunohistochemistry. Next, SIRT6 was depleted by RNA interference (RNAi), and the effect of SIRT6 depletion on changes in gene expression, protein levels, proliferation, and senescence in human chondrocytes was assessed. Furthermore, to detect DNA damage and telomere dysfunction, γH2AX foci and telomere dysfunction-induced foci (TIFs) were examined using immunofluorescence microscopy. The protein levels of two mediators for DNA damage induced-senescence, p16 and p21, were examined by western blotting.

RESULTS

Immunohistochemical analysis showed SIRT6 was preferentially expressed in the superficial zone chondrocytes and PCNA-positive cluster-forming chondrocytes in the osteoarthritic cartilage tissue samples. Real-time PCR analysis showed that matrix metalloproteinase 1 (MMP-1) and MMP-13 mRNA were significantly increased by SIRT6 inhibition. Moreover, SIRT6 inhibition significantly reduced proliferation and increased senescence associated β-galactosidase (SA-β-Gal)-positive chondrocytes; it also led to increased p16 levels. Immunofluorescence microscopy showed that γH2AX foci and TIFs were increased by SIRT6 inhibition.

CONCLUSION

Depletion of SIRT6 in human chondrocytes caused increased DNA damage and telomere dysfunction, and subsequent premature senescence. These findings suggest that SIRT6 plays an important role in the regulation of senescence of human chondrocytes.

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.

Asian sand dust causes subacute peripheral immune modification with NF-κB activation

Asian sand dust (ASD), a type of particulate matter found in Asia, migrates to East Asia. The increased airborne spread of ASD has led to concerns regarding possible adverse health effects. Our group previously reported that ASD induces lung inflammation in mice, but it is still unclear whether ASD affects lymphoid organs. In this study, we investigated the effect of ASD on splenocytes in a mouse model of ASD exposure. ICR mice were intratracheally administered a single dose of normal saline (control) or ASD and were subsequently sacrificed 1 or 3 days later. TNF-α production in bronchoalveolar lavage fluids was higher at day 1, but not at day 3, after ASD administration. The enzyme-linked immunosorbent assay results showed that ASD administration increased mitogen-induced IL-2, TNF-α, and IL-6 production in splenocytes. Additionally, cell viability assay showed enhanced splenocyte proliferation at day 3, but not at day 1, after ASD administration. The electrophoretic mobility shift assay results demonstrated that nuclear factor κB (NF-κB) was activated in splenocytes on day 3, but not on day 1. In particular, NF-κB activation was detected in CD4(+) and CD11b(+) cells on day 3. These results suggest that ASD induces subacute inflammatory responses with NF-κB activation in the spleen, in contrast to acute inflammation in the lungs.

Sirtuins in vascular diseases: Emerging roles and therapeutic potential

Silent information regulator-2 (Sir-2) proteins, or sirtuins, are a highly conserved protein family of histone deacetylases that promote longevity by mediating many of the beneficial effects of calorie restriction which extends life span and reduces the incidence of cancer, cardiovascular disease (CVD), and diabetes. Here, we review the role of sirtuins (SIRT1-7) in vascular homeostasis and diseases by providing an update on the latest knowledge about their roles in endothelial damage and vascular repair mechanisms. Among all sirtuins, in the light of the numerous functions reported on SIRT1 in the vascular system, herein we discuss its roles not only in the control of endothelial cells (EC) functionality but also in other cell types beyond EC, including endothelial progenitor cells (EPC), smooth muscle cells (SMC), and immune cells. Furthermore, we also provide an update on the growing field of compounds under clinical evaluation for the modulation of SIRT1 which, at the state of the art, represents the most promising target for the development of novel drugs against CVD, especially when concomitant with type 2 diabetes.

Sirtuin-6 inhibits cardiac fibroblasts differentiation into myofibroblasts via inactivation of nuclear factor κB signaling

Differentiation of cardiac fibroblasts (CFs) into myofibroblasts represents a key event in cardiac fibrosis that contributes to pathologic cardiac remodeling. However, regulation of this phenotypic transformation remains elusive. Here, we show that sirtuin-6 (SIRT6), a member of the sirtuin family of nicotinamide adenine dinucleotide-dependent histone deacetylase, plays a role in the regulation of myofibroblast differentiation. SIRT6 expression was upregulated under pathologic conditions in angiotensin II (Ang II)-stimulated CFs and in myocardium of rat subjected to abdominal aortic constriction surgery. SIRT6 depletion by RNA interference (small interfering RNA [siRNA]) in CFs resulted in increased cell proliferation and extracellular matrix deposition. Further examination of SIRT6-depleted CFs demonstrated significantly higher expression of α-smooth muscle actin (α-SMA), the classical marker of myofibroblast differentiation, and increased formation of focal adhesions. Notably, SIRT6 depletion further exacerbated Ang II-induced myofibroblast differentiation. Overexpression of SIRT6 restored α-SMA expression in SIRT6-depleted or Ang II-treated CFs. Moreover, SIRT6 depletion induced the DNA binding activity and transcriptional activity of nuclear factor κB (NF-κB). Importantly, using an NF-κB p65 siRNA or pyrrolidine dithiocarbamate, a specific inhibitor of NF-κB activity, reversed the expression of phenotypic markers of myofibroblasts. Our findings unravel a novel role of SIRT6 as a key modulator in the phenotypic conversion of CFs to myofibroblasts.

Impact of caloric restriction on myocardial ischaemia/reperfusion injury and new therapeutic options to mimic its effects

Caloric restriction (CR) is the most reliable intervention to extend lifespan and prevent age-related disorders in various species from yeast to rodents. Short- and long-term CR confers cardio protection against ischaemia/reperfusion injury in young and even in aged rodents. A few human trials suggest that CR has the potential to mediate improvement of cardiac or vascular function and induce retardation of cardiac senescence also in humans. The underlying mechanisms are diverse and have not yet been clearly defined. Among the known mediators for the benefits of CR are NO, the AMP-activated PK, sirtuins and adiponectin. Mitochondria, which play a central role in such complex processes within the cell as apoptosis, ATP-production or oxidative stress, are centrally involved in many aspects of CR-induced protection against ischaemic injury. Here, we discuss the relevant literature regarding the protection against myocardial ischaemia/reperfusion injury conferred by CR. Furthermore, we will discuss drug targets to mimic CR and the possible role of calorie restriction in preserving cardiovascular function in humans.

Sirtuin function in aging heart and vessels

Age is the most important risk factor for metabolic alterations and cardiovascular accidents. Although class III histone deacetylases, alias Sirtuins, have been appealed as "the fountain of youth" their role in longevity control and prevention of aging-associated disease is still under debate. Indeed, several lines of evidence indicate that sirtuin activity is strictly linked to metabolism and dependent on NAD(+) synthesis both often altered as aging progresses. During aging the cardiovascular system is attacked by a variety of environmental stresses, including those determined by high blood glucose and lipid levels, or by the presence of oxidized lipoproteins which, among others, determine important oxidative stress signals. In such a milieu, heart and vessels develop a functional impairment leading to atherosclerosis, ischemia, heart insufficiency and failure. Sirtuins, which are believed to have a positive impact on cardiovascular physiology and physiopathology, are distributed in different subcellular compartments including the nucleus, the cytoplasm and the mitochondria, where they regulate expression and function of a large variety of target genes and proteins. Remarkably, experimental animal models indicate resveratrol, the first natural compound described to positively regulate the activity of sirtuins, as able to protect the endothelium and the heart exposed to a variety of stress agents. This review will focus on the regulation and function of mammalian sirtuins with special attention paid to their role as cardiovascular "defenders" giving indication of their targets of potential relevance for the development of future therapeutics. This article is part of a Special Issue entitled CV Aging.

Histone deacetylases and atherosclerosis

Atherosclerosis is the most common pathological process that leads to cardiovascular diseases, a disease of large- and medium-sized arteries that is characterized by a formation of atherosclerotic plaques consisting of necrotic cores, calcified regions, accumulated modified lipids, smooth muscle cells (SMCs), endothelial cells, leukocytes, and foam cells. Recently, the question about how to suppress the occurrence of atherosclerosis and alleviate the progress of cardiovascular disease becomes the hot topic. Accumulating evidence suggests that histone deacetylases(HDACs) play crucial roles in arteriosclerosis. This review summarizes the effect of HDACs and HDAC inhibitors(HDACi) on the progress of atherosclerosis.

Differential expression of sirtuin family members in the developing, adult, and aged rat brain

The sirtuins are NAD⁺-dependent protein deacetylases and/or ADP-ribosyltransferases that play roles in metabolic homeostasis, stress response and potentially aging. This enzyme family resides in different subcellular compartments, and acts on a number of different targets in the nucleus, cytoplasm and in the mitochondria. Despite their recognized ability to regulate metabolic processes, the roles played by specific sirtuins in the brain—the most energy demanding tissue in the body—remains less well investigated and understood. In the present study, we examined the regional mRNA and protein expression patterns of individual sirtuin family members in the developing, adult, and aged rat brain. Our results show that while each sirtuin is expressed in the brain at each of these different stages, they display unique spatial and temporal expression patterns within the brain. Further, for specific members of the family, the protein expression profile did not coincide with their respective mRNA expression profile. Moreover, using primary cultures enriched for neurons and astrocytes respectively, we found that specific sirtuin members display preferential neural lineage expression. Collectively, these results provide the first composite illustration that sirtuin family members display differential expression patterns in the brain, and provide evidence that specific sirtuins could potentially be targeted to achieve cell-type selective effects within the brain.

Role of plasminogen activator inhibitor-1 in senescence and aging

The average age of the US population continues to increase. Age is the most important determinant of disease and disability in humans, but the fundamental mechanisms of aging remain largely unknown. Many age-related diseases are associated with an impaired fibrinolytic system. Elevated plasminogen activator inhibitor-1 (PAI-1) levels are reported in age-associated clinical conditions including cardiovascular diseases, type 2 diabetes, obesity and inflammation. PAI-1 levels are also elevated in animal models of aging. While the association of PAI-1 with physiological aging is well documented, it is only recently that its critical role in the regulation of aging and senescence has become evident. PAI-1 is synthesized and secreted in senescent cells and contributes directly to the development of senescence by acting downstream of p53 and upstream of insulin-like growth factor binding protein-3. Pharmacologic inhibition or genetic deficiency of PAI-1 was shown to be protective against senescence and the aging-like phenotypes in kl/kl and N(ω)-nitro-l-arginine methyl ester-treated wild-type mice. Further investigation into PAI-1's role in senescence and aging will likely contribute to the prevention and treatment of aging-related pathologies.

SIRT1 inhibition affects angiogenic properties of human MSCs

Human mesenchymal stem cells (hMSCs) are attractive for clinical and experimental purposes due to their capability of self-renewal and of differentiating into several cell types. Autologous hMSCs transplantation has been proven to induce therapeutic angiogenesis in ischemic disorders. However, the molecular mechanisms underlying these effects remain unclear. A recent report has connected MSCs multipotency to sirtuin families, showing that SIRT1 can regulate MSCs function. Furthermore, SIRT1 is a critical modulator of endothelial angiogenic functions. Here, we described the generation of an immortalized human mesenchymal bone marrow-derived cell line and we investigated the angiogenic phenotype of our cellular model by inhibiting SIRT1 by both the genetic and pharmacological level. We first assessed the expression of SIRT1 in hMSCs under basal and hypoxic conditions at both RNA and protein level. Inhibition of SIRT1 by sirtinol, a cell-permeable inhibitor, or by specific sh-RNA resulted in an increase of premature-senescence phenotype, a reduction of proliferation rate with increased apoptosis. Furthermore, we observed a consistent reduction of tubule-like formation and migration and we found that SIRT1 inhibition reduced the hypoxia induced accumulation of HIF-1α protein and its transcriptional activity in hMSCs. Our findings identify SIRT1 as regulator of hypoxia-induced response in hMSCs and may contribute to the development of new therapeutic strategies to improve regenerative properties of mesenchymal stem cells in ischemic disorders through SIRT1 modulation.

Endothelial cell senescence and age-related vascular diseases

Advanced age is an independent risk factor for ageing-related complex diseases, such as coronary artery disease, stroke, and hypertension, which are common but life threatening and related to the ageing-associated vascular dysfunction. On the other hand, patients with progeria syndromes suffer from serious atherosclerosis, suggesting that the impaired vascular functions may be critical to organismal ageing, or vice versa. However, it remains largely unknown how vascular cells, particularly endothelial cell, become senescent and how the senescence impairs the vascular functions and contributes to the age-related vascular diseases over time. Here, we review the recent progress on the characteristics of vascular ageing and endothelial cell senescence in vitro and in vivo, evaluate how genetic and environmental factors as well as autophagy and stem cell influence endothelial cell senescence and how the senescence contributes to the age-related vascular phenotypes, such as atherosclerosis and increased vascular stiffness, and explore the possibility whether we can delay the age-related vascular diseases through the control of vascular ageing.

Oxidative stress induces endothelial cell senescence via downregulation of Sirt6

Accumulating evidence has shown that diabetes accelerates aging and endothelial cell senescence is involved in the pathogenesis of diabetic vascular complications, including diabetic retinopathy. Oxidative stress is recognized as a key factor in the induction of endothelial senescence and diabetic retinopathy. However, specific mechanisms involved in oxidative stress-induced endothelial senescence have not been elucidated. We hypothesized that Sirt6, which is a nuclear, chromatin-bound protein critically involved in many pathophysiologic processes such as aging and inflammation, may have a role in oxidative stress-induced vascular cell senescence. Measurement of Sirt6 expression in human endothelial cells revealed that H2O2 treatment significantly reduced Sirt6 protein. The loss of Sirt6 was associated with an induction of a senescence phenotype in endothelial cells, including decreased cell growth, proliferation and angiogenic ability, and increased expression of senescence-associated β-galactosidase activity. Additionally, H2O2 treatment reduced eNOS expression, enhanced p21 expression, and dephosphorylated (activated) retinoblastoma (Rb) protein. All of these alternations were attenuated by overexpression of Sirt6, while partial knockdown of Sirt6 expression by siRNA mimicked the effect of H2O2. In conclusion, these results suggest that Sirt6 is a critical regulator of endothelial senescence and oxidative stress-induced downregulation of Sirt6 is likely involved in the pathogenesis of diabetic retinopathy.

Interplay between sirtuins, MYC and hypoxia-inducible factor in cancer-associated metabolic reprogramming

In the early twentieth century, Otto Heinrich Warburg described an elevated rate of glycolysis occurring in cancer cells, even in the presence of atmospheric oxygen (the Warburg effect). Despite the inefficiency of ATP generation through glycolysis, the breakdown of glucose into lactate provides cancer cells with a number of advantages, including the ability to withstand fluctuations in oxygen levels, and the production of intermediates that serve as building blocks to support rapid proliferation. Recent evidence from many cancer types supports the notion that pervasive metabolic reprogramming in cancer and stromal cells is a crucial feature of neoplastic transformation. Two key transcription factors that play major roles in this metabolic reprogramming are hypoxia inducible factor-1 (HIF1) and MYC. Sirtuin-family deacetylases regulate diverse biological processes, including many aspects of tumor biology. Recently, the sirtuin SIRT6 has been shown to inhibit the transcriptional output of both HIF1 and MYC, and to function as a tumor suppressor. In this Review, we highlight the importance of HIF1 and MYC in regulating tumor metabolism and their regulation by sirtuins, with a main focus on SIRT6.

SIRT4 inhibits cigarette smoke extracts-induced mononuclear cell adhesion to human pulmonary microvascular endothelial cells via regulating NF-κB activity

Cigarette smoking is an important risk factor for chronic obstructive pulmonary disease (COPD), yet its pathogenic mechanisms are not yet fully understood. Endothelial dysfunction is known to be involved in the pathogenesis of COPD. A detailed understanding of the mechanism involved in its progression would have a substantial impact on the optimization and development of treatment strategies. Here, we report that the expression of SIRT4, a mitochondrial sirtuin, is markedly down-regulated in cigarette smoke extract (CSE)-treated human pulmonary microvascular endothelial cells (HPMECs). Overexpression of SIRT4 significantly inhibits CSE-induced mononuclear cell adhesion to HPMECs. Consistently, we found that overexpression of SIRT4 attenuates the induction of vascular cell adhesion molecule 1 (VCAM-1) and E-selectin. Importantly, SIRT4 was found to negatively regulate CSE-induced NF-κB activation via inhibiting the degradation of IκBα. Moreover, we also found that proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6, the downstream target genes of NF-κB, are also inhibited by overexpression of SIRT4. These results suggest that SIRT4 protects HPMECs exposed to CSE stress via a mechanism that may involve the NF-κB pathway. Strategies based on the enhancement of SIRT4 may prove to be beneficial in the treatment of cigarette smoking caused COPD.

KNDC1 knockdown protects human umbilical vein endothelial cells from senescence

KNDC1 (kinase noncatalytic C-lobe domain containing 1), a brain-specific Ras guanine nucleotide exchange factor, controls the negative regulation of neuronal dendrite growth. However, the effect of KNDC1 on cellular senescence remains to be elucidated. The present study investigated the impact of KNDC1 knockdown on human endothelial cell senescence and the mechanisms underlying this effect. Human umbilical vein endothelial cells (HUVECs) cultured in vitro were used as a model of biological aging. Senescence-associated β-galactosidase staining was used to detect cellular senescence and flow cytometry was employed to determine cell cycle progression. Quantitative polymerase chain reaction (qPCR) and western blot analysis were utilized to investigate mRNA transcription and protein expression. In the HUVECs, a senescence-like phenotypes developed with increasing passage number in vitro, which were associated with a progressive increase in the transcription and expression of KNDC1. KNDC1 knockdown promoted cell proliferation and partially reversed cellular senescence and cell cycle arrest in the G0/G1 phase in aging HUVECs. Investigations into the mechanism underlying this effect demonstrated that KNDC1 knockdown promoted HUVEC proliferation via the extracellular signal-regulated kinase signaling pathway and delayed HUVEC senescence by inhibiting the p53-p21-p16 transduction cascade. In addition, the promotion of the capillary tube network formation and the increased expression of endothelial nitric oxide synthase revealed that the activity and function of endothelial cells were enhanced. In conclusion, KNDC1 knockdown delayed endothelial cell senescence and promoted HUVEC activity and function. These results demonstrated that KNDC1 may be a novel therapeutic target for the development of agents to extend human life.

Changes in human sirtuin 6 gene promoter methylation during aging

Aging is a natural process during which changes at the cellular level increase death risk by developing susceptibility to a variety of diseases. Sirtuins have been shown to regulate lifespan in various organisms by deacetylating a number of important transcription factors. Of the 7 identified mammalian sirtuins (SIRT1-7), SIRT6 depletion is associated with severe symptoms of premature aging. In this study, we investigated the association between human longevity and SIRT6 promoter methylation. Genomic DNA from blood samples of 55 individuals (34 females and 21 males) was examined to detect methylation levels by quantitative polymerase chain reaction analysis following bisulfite treatment. While the results indicated 43.21% methylation in the 9-19 age group, this ratio was found to be increased up to 65.63% in the 20-79 age group and decreased to 52.15% in the 80-95 age group. Our results demonstrated that the SIRT6 gene is more active between 9-19 and 80-95 years compared to 20-79 years.

Regulation of Akt signaling by sirtuins: its implication in cardiac hypertrophy and aging

Cardiac hypertrophy is a multifactorial disease characterized by multiple molecular alterations. One of these alterations is change in the activity of Akt, which plays a central role in regulating a variety of cellular processes ranging from cell survival to aging. Akt activation is mainly achieved by its binding to phosphatidylinositol (3,4,5)-triphosphate. This results in a conformational change that exposes the kinase domain of Akt for phosphorylation and activation by its upstream kinase, 3-phosphoinositide-dependent protein kinase 1, in the cell membrane. Recent studies have shown that sirtuin isoforms, silent information regulator (SIRT) 1, SIRT3, and SIRT6, play an essential role in the regulation of Akt activation. Although SIRT1 deacetylates Akt to promote phosphatidylinositol (3,4,5)-triphosphate binding and activation, SIRT3 controls reactive oxygen species-mediated Akt activation, and SIRT6 transcriptionally represses Akt at the level of chromatin. In the first part of this review, we discuss the mechanisms by which sirtuins regulate Akt activation and how they influence other post-translational modifications of Akt. In the latter part of the review, we summarize the implications of sirtuin-dependent regulation of Akt signaling in the control of major cellular processes such as cellular growth, angiogenesis, apoptosis, autophagy, and aging, which are involved in the initiation and progression of several diseases.

Proteomics analysis of normal and senescent NG108-15 cells: GRP78 plays a negative role in cisplatin-induced senescence in the NG108-15 cell line

Accelerated senescence (ACS) leading to proliferative arrest is a physiological mechanism of the DNA damage response that occurs during tumor therapy. Our experiment was designed to detect unknown genes that may play important roles in cisplatin-induced senescence and to illustrate the related senescence mechanism. Using 2-dimension electrophoresis (2-DE), we identified 5 protein spots with different expression levels in the normal and senescent NG108-15 cells. According to MALDI-TOF MS analysis, the 5 proteins were determined to be peptidylprolyl isomerase A (PPIA), peroxiredoxin 1 (PRX1), glutathione S-transferase mu 1 (GSTM1), vimentin (VIM) and glucose-regulated protein 78 (GRP78). Then, we investigated how cisplatin-induced senescence was mediated by GRP78 in the NG108-15 cells. Knockdown of GRP78 significantly increased P53 expression in NG108-15 cells. Additionally, 2-deoxy-D-glucose (2DG)-induced GRP78 overexpression protected the NG108-15 cells from cisplatin-induced senescence, which was accompanied by the obvious suppression of P53 and p-CDC2 expression. Inhibition of Ca2+ release from endoplasmic reticulum (ER) stores was also found to be associated with the anti-senescence effect of 2DG-induced GRP78 overexpression. In conclusion, we found 5 proteins that were differentially expressed in normal NG108-15 cells and senescent NG108-15 cells. GRP78 plays an important role in cisplatin-induced senescence in NG108-15 cells, mainly through its regulation of P53 expression and ER calcium efflux.

Adrenergic signaling and oxidative stress: a role for sirtuins?

The adrenergic system plays a central role in stress signaling and stress is often associated with increased production of ROS. However, ROS overproduction generates oxidative stress, that occurs in response to several stressors. β-adrenergic signaling is markedly attenuated in conditions such as heart failure, with downregulation and desensitization of the receptors and their uncoupling from adenylyl cyclase. Transgenic activation of β2-adrenoceptor leads to elevation of NADPH oxidase activity, with greater ROS production and p38MAPK phosphorylation. Inhibition of NADPH oxidase or ROS significantly reduced the p38MAPK signaling cascade. Chronic β2-adrenoceptor activation is associated with greater cardiac dilatation and dysfunction, augmented pro-inflammatory and profibrotic signaling, while antioxidant treatment protected hearts against these abnormalities, indicating ROS production to be central to the detrimental signaling of β2-adrenoceptors. It has been demonstrated that sirtuins are involved in modulating the cellular stress response directly by deacetylation of some factors. Sirt1 increases cellular stress resistance, by an increased insulin sensitivity, a decreased circulating free fatty acids and insulin-like growth factor (IGF-1), an increased activity of AMPK, increased activity of PGC-1a, and increased mitochondrial number. Sirt1 acts by involving signaling molecules such P-I-3-kinase-Akt, MAPK and p38-MAPK-β. βAR stimulation antagonizes the protective effect of the AKT pathway through inhibiting induction of Hif-1α and Sirt1 genes, key elements in cell survival. More studies are needed to better clarify the involvement of sirtuins in the β-adrenergic response and, overall, to better define the mechanisms by which tools such as exercise training are able to counteract the oxidative stress, by both activation of sirtuins and inhibition of GRK2 in many cardiovascular conditions and can be used to prevent or treat diseases such as heart failure.

Adrenergic signaling and oxidative stress: a role for sirtuins?

The adrenergic system plays a central role in stress signaling and stress is often associated with increased production of ROS. However, ROS overproduction generates oxidative stress, that occurs in response to several stressors. β-adrenergic signaling is markedly attenuated in conditions such as heart failure, with downregulation and desensitization of the receptors and their uncoupling from adenylyl cyclase. Transgenic activation of β2-adrenoceptor leads to elevation of NADPH oxidase activity, with greater ROS production and p38MAPK phosphorylation. Inhibition of NADPH oxidase or ROS significantly reduced the p38MAPK signaling cascade. Chronic β2-adrenoceptor activation is associated with greater cardiac dilatation and dysfunction, augmented pro-inflammatory and profibrotic signaling, while antioxidant treatment protected hearts against these abnormalities, indicating ROS production to be central to the detrimental signaling of β2-adrenoceptors. It has been demonstrated that sirtuins are involved in modulating the cellular stress response directly by deacetylation of some factors. Sirt1 increases cellular stress resistance, by an increased insulin sensitivity, a decreased circulating free fatty acids and insulin-like growth factor (IGF-1), an increased activity of AMPK, increased activity of PGC-1a, and increased mitochondrial number. Sirt1 acts by involving signaling molecules such P-I-3-kinase-Akt, MAPK and p38-MAPK-β. βAR stimulation antagonizes the protective effect of the AKT pathway through inhibiting induction of Hif-1α and Sirt1 genes, key elements in cell survival. More studies are needed to better clarify the involvement of sirtuins in the β-adrenergic response and, overall, to better define the mechanisms by which tools such as exercise training are able to counteract the oxidative stress, by both activation of sirtuins and inhibition of GRK2 in many cardiovascular conditions and can be used to prevent or treat diseases such as heart failure.

Sirt6 regulates postnatal growth plate differentiation and proliferation via Ihh signaling

Sirtuin 6 (Sirt6) is a mammalian homologue of NAD⁺-dependent histone deacetylase Sir2. Although Sirt6−/− mice exhibit growth retardation, the role of Sirt6 in cartilage metabolism is unclear. The aim of this study was to investigate the Sirt6 signaling pathway in cartilage metabolism. Immunohistological evaluation of the tibial growth plate in Sirt6−/− mice exhibited impaired proliferation and differentiation of chondrocytes, reduced expression of Indian hedgehog (Ihh), and a senescent phenotype. When Sirt6 was knocked down in chondrocytes in vitro, expression of Ihh and its downstream genes were reduced. Impaired differentiation by Sirt6 silencing was completely rescued by administration of a Hh signal agonist. When sirtuins were activated, chondrocyte differentiation was enhanced together with activation of Ihh signal, and these effects were abrogated by Sirt6 silencing. ChIP assay revealed the affinity of ATF4 to the Ihh promoter was markedly decreased by Sirt6 knockdown. These data indicate Sirt6 directly controls proliferation and differentiation of chondrocytes.

Inhibition of SIRT6 in prostate cancer reduces cell viability and increases sensitivity to chemotherapeutics

SIRT6 is an important histone modifying protein that regulates DNA repair, telomere maintenance, energy metabolism, and target gene expression. Recently SIRT6 has been identified as a tumor suppressor and is down-regulated in certain cancer types, but not in other cancers. From deposited gene profiling studies we found that SIRT6 was overexpressed in prostate tumors, compared with normal or paratumor prostate tissues. Tissue micro-array studies confirmed the higher levels of SIRT6 in both prostate tumor tissues and prostate cancer cells than in their normal counterparts. Knockdown of SIRT6 in human prostate cancer cells led to sub-G1 phase arrest of cell cycle, increased apoptosis, elevated DNA damage level and decrease in BCL2 gene expression. Moreover, SIRT6-deficiency reduced cell viability and enhanced chemotherapeutics sensitivity. Taken together, this study provides the first evidence of SIRT6 overexpression in human prostate cancer, and SIRT6 regulation could be exploited for prostate cancer therapy.

The role of SIRT1 in ocular aging

The sirtuins are a highly conserved family of nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases that helps regulate the lifespan of diverse organisms. The human genome encodes seven different sirtuins (SIRT1-7), which share a common catalytic core domain but possess distinct N- and C-terminal extensions. Dysfunction of some sirtuins have been associated with age-related diseases, such as cancer, type II diabetes, obesity-associated metabolic diseases, neurodegeneration, and cardiac aging, as well as the response to environmental stress. SIRT1 is one of the targets of resveratrol, a polyphenolic SIRT1 activator that has been shown to increase the lifespan and to protect various organs against aging. A number of animal studies have been conducted to examine the role of sirtuins in ocular aging. Here we review current knowledge about SIRT1 and ocular aging. The available data indicate that SIRT1 is localized in the nucleus and cytoplasm of cells forming all normal ocular structures, including the cornea, lens, iris, ciliary body, and retina. Upregulation of SIRT1 has been shown to have an important protective effect against various ocular diseases, such as cataract, retinal degeneration, optic neuritis, and uveitis, in animal models. These results suggest that SIRT1 may provide protection against diseases related to oxidative stress-induced ocular damage, including cataract, age-related macular degeneration, and optic nerve degeneration in glaucoma patients.

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.