Repression of P66Shc expression by SIRT1 contributes to the prevention of hyperglycemia-induced endothelial dysfunction

Epigenetics in diabetic nephropathy, immunity and metabolism

When it comes to the epigenome, there is a fine line between clarity and confusion-walk that line and you will discover another fascinating level of transcription control. With the genetic code representing the cornerstone of rules for information that is encoded to proteins somewhere above the genome level there is a set of rules by which chemical information is also read. These epigenetic modifications show a different side of the genetic code that is diverse and regulated, hence modifying genetic transcription transiently, ranging from short- to long-term alterations. While this complexity brings exquisite control it also poses a formidable challenge to efforts to decode mechanisms underlying complex disease. Recent technological and computational advances have improved unbiased acquisition of epigenomic patterns to improve our understanding of the complex chromatin landscape. Key to resolving distinct chromatin signatures of diabetic complications is the identification of the true physiological targets of regulatory proteins, such as reader proteins that recognise, writer proteins that deposit and eraser proteins that remove specific chemical moieties. But how might a diverse group of proteins regulate the diabetic landscape from an epigenomic perspective? Drawing from an ever-expanding compendium of experimental and clinical studies, this review details the current state-of-play and provides a perspective of chromatin-dependent mechanisms implicated in diabetic complications, with a special focus on diabetic nephropathy. We hypothesise a codified signature of the diabetic epigenome and provide examples of prime candidates for chemical modification. As for the pharmacological control of epigenetic marks, we explore future strategies to expedite and refine the search for clinically relevant discoveries. We also consider the challenges associated with therapeutic strategies targeting epigenetic pathways.

Epigenetic Regulation of Vascular Aging and Age-Related Vascular Diseases

Vascular aging refers to the structural and functional defects that occur in the aorta during the aging process and is characterized by increased vascular cell senescence, vascular dyshomeostasis, and vascular remodeling. Vascular aging is a major risk factor for vascular diseases. However, the current understanding of the biological process of vascular aging and age-related diseases is insufficient. Epigenetic regulation can influence gene expression independently of the gene sequence and mainly includes DNA methylation, histone modifications, and RNA-based gene regulation. Epigenetic regulation plays important roles in many physiological and pathophysiological processes and may explain some gaps in our knowledge regarding the interaction between genes and diseases. In this review, we summarize recent advances in the understanding of the epigenetic regulation of vascular aging and age-related diseases in terms of vascular cell senescence, vascular dyshomeostasis, and vascular remodeling. Moreover, the possibility of targeting epigenetic regulation to delay vascular aging and treat age-related vascular diseases is also discussed.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

A maternal high-fat diet during pregnancy and lactation, in addition to a postnatal high-fat diet, leads to metabolic syndrome with spatial learning and memory deficits: beneficial effects of resveratrol

We tested the hypothesis that high-fat diet consumption during pregnancy, lactation, and/or post weaning, altered the expression of molecular mediators involved in hippocampal synaptic efficacy and impaired spatial learning and memory in adulthood. The beneficial effect of resveratrol was assessed. Dams were fed a rat chow diet or a high-fat diet before mating, during pregnancy, and throughout lactation. Offspring were weaned onto either a rat chow or a high-fat diet. Four experimental groups were generated, namely CC, HC, CH, and HH (maternal chow diet or high-fat diet; postnatal chow diet or high-fat diet). A fifth group fed with HH plus resveratrol (HHR) was generated. Morris water maze test was used to evaluate spatial learning and memory. Blood pressure and IPGTT was measured to assess insulin resistance. Dorsal hippocampal expression of certain biochemical molecules, including sirtuin 1, ERK, PPARγ, adiponectin, and BDNF were measured. Rats in HH group showed impaired spatial memory, which was partly restored by the administration of resveratrol. Rats in HH group also showed impaired glucose tolerance and increased blood pressure, all of which was rescued by resveratrol administration. Additionally, SIRT1, phospho-ERK1/2, and phospho-PPARγ, adiponectin and BDNF were all dysregulated in rats placed in HH group; administration of resveratrol restored the expression and regulation of these molecules. Overall, our results suggest that maternal high-fat diet during pregnancy and/or lactation sensitizes the offspring to the adverse effects of a subsequent high-fat diet on hippocampal function; however, administration of resveratrol is demonstrated to be beneficial in rescuing these effects.

RNA methyltransferase NSUN2 promotes stress-induced HUVEC senescence

The tRNA methyltransferase NSUN2 delays replicative senescence by regulating the translation of CDK1 and CDKN1B mRNAs. However, whether NSUN2 influences premature cellular senescence remains untested. Here we show that NSUN2 methylates SHC mRNA in vitro and in cells, thereby enhancing the translation of the three SHC proteins, p66SHC, p52SHC, and p46SHC. Our results further show that the elevation of SHC expression by NSUN2-mediated mRNA methylation increased the levels of ROS, activated p38MAPK, thereby accelerating oxidative stress- and high-glucose-induced senescence of human vascular endothelial cells (HUVEC). Our findings highlight the critical impact of NSUN2-mediated mRNA methylation in promoting premature senescence.

The protective role of Sirt1 in vascular tissue: its relationship to vascular aging and atherosclerosis

Cardiovascular disease (CVD) due to atherosclerosis is the main cause of death in both the elderly and patients with metabolic diseases, including diabetes. Aging processes contribute to the pathogenesis of atherosclerosis. Calorie restriction (CR) is recognized as a dietary intervention for promoting longevity and delaying age-related diseases, including atherosclerosis. Sirt1, an NAD⁺-dependent deacetylase, is considered an anti-aging molecule and is induced during CR. Sirt1 deacetylates target proteins and is linked to cellular metabolism, the redox state and survival pathways. Sirt1 expression/activation is decreased in vascular tissue undergoing senescence. Sirt1 deficiency in endothelial cells (ECs), vascular smooth muscle cells (VSMCs) and monocytes/macrophages contributes to increased oxidative stress, inflammation, foam cell formation, senescences impaired nitric oxide production and autophagy, thereby promoting vascular aging and atherosclerosis. Endothelial dysfunction, activation of monocytes/macrophages, and the functional and phenotypical plasticity of VSMCs are critically implicated in the pathogenesis of atherosclerosis through multiple mechanisms. Therefore, the activation of Sirt1 in vascular tissue, which includes ECs, monocytes/macrophages and VSMCs, may be a new therapeutic strategy against atherosclerosis and the increasing resistance to the metabolic disorder-related causal factors of CVD. In this review, we discuss the protective role of Sirt1 in the pathophysiology of vascular aging and atherosclerosis.

Cathepsin L deficiency results in reactive oxygen species (ROS) accumulation and vascular cells activation

Recent evidence suggests a link between cathepsin L (CTSL) and vascular diseases. However, its contribution to reactive oxygen species (ROS) homeostasis in the vasculature remains unknown. p66shc is a redox enzyme implicated in mitochondrial ROS generation and translation of oxidative signals. In this study, we explored the relationship between CTSL and oxidative damage in vasculature and whether the oxidative damage is mediated by p66shc.Carotid arteries from aged mice (24 months old) showed a reduction in CTSL expression compared with young wild-type mice (4 months old). Local knockdown of CTSL in carotid arteries of young mice by adenoviral vector encoding the short hairpin RNA targeting CTSL leading to premature vascular aging, as shown by mitochondrial disruption, increased β-galactosidase-positive cells, reduced telomerase activity, and up-regulation of p66shc. Knockdown of CTSL decreased the expression of mitochondrial oxidative phosphorylation (OXPHOS) complexes I, III, and IV, leading to increased mitochondrial ROS and hyperpolarization of the mitochondrial membrane in vitro. Furthermore, knockdown of CTSL also stimulated ROS production and senescence in vascular cells, accompanied by the up-regulation of p66shc.However, p66shc knockdown blunted the alteration in ROS production, and senescence in CTSL knockdown vascular cells. This study suggests that CTSL knockdown partially induces vascular cells damage via increased ROS production and up-regulation of p66shc.

Role of adaptor protein p66Shc in renal pathologies

p66Shc is one of the three adaptor proteins encoded by the Shc1 gene, which are expressed in many organs, including the kidney. Recent studies shed new light on several key questions concerning the signaling mechanisms mediated by p66Shc. The central goal of this review article is to summarize recent findings on p66Shc and the role it plays in kidney physiology and pathology. This article provides a review of the various mechanisms whereby p66Shc has been shown to function within the kidney through a wide range of actions. The mitochondrial and cytoplasmic signaling of p66Shc, as it relates to production of reactive oxygen species (ROS) and renal pathologies, is further discussed.

Activation of miR-34a-5p/Sirt1/p66shc pathway contributes to doxorubicin-induced cardiotoxicity

The molecular mechanisms underlying anthracyclines-induced cardiotoxicity have not been well elucidated. MiRNAs were revealed dysregulated in the myocardium and plasma of rats received Dox treatment. MicroRNA-34a-5p (miR-34a-5p) was verified increased in the myocardium and plasma of Dox-treated rats, but was reversed in rats received Dox plus DEX treatments. Human miR-34a-5p was also observed increased in the plasma of patients with diffuse large B-cell lymphoma after 9- and 16-week epirubicin therapy. Up-regulation of miR-34a-5p was observed in Dox-induced rat cardiomyocyte H9c2 cells. MiR-34a-5p could augment Bax expression, but inhibited Bcl-2 expression, along with the increases of the activated caspase-3 and mitochondrial potentials in H9C2 cells. MiR-34a-5p was verified to modulate Sirt1 expression post-transcriptionally. In parallel to Sirt1 siRNA, miR-34a-5p could enhance p66shc expression, accompanied by increases of Bax and the activated caspase-3 and a decrease of Bcl-2 in H9c2 cells. Moreover, enforced expression of Sirt1 alleviated Dox-induced apoptosis of H9c2 cells, with suppressing levels of p66shc, Bax, the activated caspase-3 and miR-34a-5p, and enhancing Bcl-2 expression. Therefore, miR-34a-5p enhances cardiomyocyte apoptosis by targeting Sirt1, activation of miR-34a-5p/Sirt1/p66shc pathway contributes to Dox-induced cardiotoxicity, and blockage of this pathway represents a potential cardioprotective effect against anthracyclines.

Impact of Glycemic Variability on Chromatin Remodeling, Oxidative Stress, and Endothelial Dysfunction in Patients With Type 2 Diabetes and With Target HbA1c Levels

Intensive glycemic control (IGC) targeting HbA_1c fails to show an unequivocal reduction of macrovascular complications in type 2 diabetes (T2D); however, the underlying mechanisms remain elusive. Epigenetic changes are emerging as important mediators of cardiovascular damage and may play a role in this setting. This study investigated whether epigenetic regulation of the adaptor protein p66^Shc, a key driver of mitochondrial oxidative stress, contributes to persistent vascular dysfunction in patients with T2D despite IGC. Thirty-nine patients with uncontrolled T2D (HbA_1c >7.5%) and 24 age- and sex-matched healthy control subjects were consecutively enrolled. IGC was implemented for 6 months in patients with T2D to achieve a target HbA_1c of ≤7.0%. Brachial artery flow-mediated dilation (FMD), urinary 8-isoprostaglandin F_2α (8-isoPGF_2α), and epigenetic regulation of p66^Shc were assessed at baseline and follow-up. Continuous glucose monitoring was performed to determine the mean amplitude of glycemic excursion (MAGE) and postprandial incremental area under the curve (AUCpp). At baseline, patients with T2D showed impaired FMD, increased urinary 8-isoPGF_2α, and p66^Shc upregulation in circulating monocytes compared with control subjects. FMD, 8-isoPGF_2α, and p66^Shc expression were not affected by IGC. DNA hypomethylation and histone 3 acetylation were found on the p66^Shc promoter of patients with T2D, and IGC did not change such adverse epigenetic remodeling. Persistent downregulation of methyltransferase DNMT3b and deacetylase SIRT1 may explain the observed p66^Shc-related epigenetic changes. MAGE and AUCpp but not HbA_1c were independently associated with the altered epigenetic profile on the p66^Shc promoter. Hence, glucose fluctuations contribute to chromatin remodeling and may explain persistent vascular dysfunction in patients with T2D with target HbA_1c levels.

Mitochondrial Sirtuins in cardiometabolic diseases

Mitochondria are heterogeneous and essentially contribute to cellular functions and tissue homeostasis. Mitochondrial dysfunction compromises overall cell functioning, tissue damage, and diseases. The advances in mitochondrion biology increase our understanding of mitochondrial dynamics, bioenergetics, and redox homeostasis, and subsequently, their functions in tissue homeostasis and diseases, including cardiometabolic diseases (CMDs). The functions of mitochondria mainly rely on the enzymes in their matrix. Sirtuins are a family of NAD+-dependent deacylases and ADP-ribosyltransferases. Three members of the Sirtuin family (SIRT3, SIRT4, and SIRT5) are located in the mitochondrion. These mitochondrial Sirtuins regulate energy and redox metabolism as well as mitochondrial dynamics in the mitochondrial matrix and are involved in cardiovascular homeostasis and CMDs. In this review, we discuss the advances in our understanding of mitochondrial Sirtuins in mitochondrion biology and CMDs, including cardiac remodeling, pulmonary artery hypertension, and vascular dysfunction. The potential therapeutic strategies by targetting mitochondrial Sirtuins to improve mitochondrial function in CMDs are also addressed.

Biogenesis of Pro-senescent Microparticles by Endothelial Colony Forming Cells from Premature Neonates is driven by SIRT1-Dependent Epigenetic Regulation of MKK6

Senescent cells may exert detrimental effect on microenvironment through the secretion of soluble factors and the release of extracellular vesicles, such as microparticles, key actors in ageing and cardiovascular diseases. We previously reported that sirtuin-1 (SIRT1) deficiency drives accelerated senescence and dysfunction of endothelial colony-forming cells (ECFC) in PT neonates. Because preterm birth (PT) increases the risk for cardiovascular diseases during neonatal period as well as at adulthood, we hypothesized that SIRT1 deficiency could control the biogenesis of microparticles as part of a senescence–associated secretory phenotype (SASP) of PT-ECFC and investigated the related molecular mechanisms. Compared to control ECFC, PT-ECFC displayed a SASP associated with increased release of endothelial microparticles (EMP), mediating a paracrine induction of senescence in naïve endothelial cells. SIRT1 level inversely correlated with EMP release and drives PT-ECFC vesiculation. Global transcriptomic analysis revealed changes in stress response pathways, specifically the MAPK pathway. We delineate a new epigenetic mechanism by which SIRT1 deficiency regulates MKK6/p38^MAPK/Hsp27 pathway to promote EMP biogenesis in senescent ECFC. These findings deepen our understanding of the role of ECFC senescence in the disruption of endothelial homeostasis and provide potential new targets towards the control of cardiovascular risk in individuals born preterm.

Molecular mechanisms underlying metabolic syndrome: the expanding role of the adipocyte

The metabolic syndrome (MetS) is defined as a cluster of 3 or more metabolic and cardiovascular risk factors and represents a serious problem for public health. Altered function of adipose tissue has a significant impact on whole-body metabolism and represents a key driver for the development of these metabolic derangements, collectively referred as to MetS. In particular, increased visceral and ectopic fat deposition play a major role in the development of insulin resistance and MetS. A large body of evidence demonstrates that aging and MetS share several metabolic alterations. Of importance, molecular pathways that regulate lifespan affect key processes of adipose tissue physiology, and transgenic mouse models with adipose-specific alterations in these pathways show derangements of adipose tissue and other metabolic features of MetS, which highlights a causal link between dysfunctional adipose tissue and deleterious effects on whole-body homeostasis. This review analyzes adipose tissue-specific dysfunctions, including metabolic alterations that are related to aging, that have a significant impact on the development of MetS.-Armani, A., Berry, A., Cirulli, F., Caprio, M. Molecular mechanisms underlying metabolic syndrome: the expanding role of the adipocyte.

Probucol ameliorates renal injury in diabetic nephropathy by inhibiting the expression of the redox enzyme p66Shc

AIMS

Probucol is an anti-hyperlipidemic agent and a potent antioxidant drug that can delay progression of diabetic nephropathy (DN) and reverses renal oxidative stress in diabetic animal models; however, the mechanisms underlying these effects remain unclear. p66Shc is a newly recognized mediator of mitochondrial ROS production in renal cells under high-glucose (HG) ambience. We previously showed that p66Shc can serve as a biomarker for renal oxidative injury in DN patients and that p66Shc up-regulation is correlated with renal damage in vivo and in vitro. Here, we determined whether probucol ameliorates renal injury in DN by inhibiting p66Shc expression.

RESULTS

We found that the expression of SIRT1, Ac-H3 and p66Shc in kidneys of DN patients was altered. Also, probucol reduced the levels of serum creatinine, urine protein and LDL-c and attenuated renal oxidative injury and fibrosis in STZ induced diabetic mice. In addition, probucol reversed p-AMPK, SIRT1, Ac-H3 and p66Shc expression. Correlation analyses showed that p66Shc expression was correlated with p-AMPK and Sirt1 expression and severity of renal injury. In vitro pretreatment of HK-2 cells with p-AMPK and SIRT1 siRNA negated the beneficial effects of probucol. Furthermore, we noted that probucol activates p-AMPK and Sirt1 and inhibits p66shc mRNA transcription by facilitating the binding of Sirt1 to the p66Shc promoter and modulation of Ac-H3 expression in HK-2 cells under HG ambience.

INNOVATION AND CONCLUSION

Our results suggest for the first time that probucol ameliorates renal damage in DN by epigenetically suppressing p66Shc expression via the AMPK-SIRT1-AcH3 pathway.

Resveratrol Pretreatment Attenuates Concanavalin A-induced Hepatitis through Reverse of Aberration in the Immune Response and Regenerative Capacity in Aged Mice

Loss of regenerative capacity plays a critical role in age-related autoimmune hepatitis. Evidence implicates SIRT1 and p66^shc in cell senescence, apoptosis, oxidative stress, and proliferation. This study investigated the effect of resveratrol on concanavalin A (Con A)-induced hepatitis in aged mice and the roles of SIRT1 and p66^shc. Aged mice were administrated resveratrol (30 mg/kg orally) seven times at an interval of 12 h before a single intravenous injection of Con A (20 mg/kg). Results showed that the cytokines, TNF-α, IL-6, IFN-γ, and MCP-1, as well as infiltration of macrophages, neutrophils, and T lymphocytes in liver were dramatically enhanced in the mice given only Con A. The aged mouse livers showed markedly raised oxidative stress and cell apoptosis. This oxidative stress further aggravated regenerative dysfunction as indicated by the decreased levels of Ki67, PCNA, Cyclin D1, and Cdk2. Conversely, these phenomena were attenuated by pretreatment with resveratrol. Moreover, resveratrol suppressed the elevation of p66^shc in the liver by reversing Con-A-mediated downregulation of SIRT1. The findings suggest that resveratrol protected against Con A-induced hepatitis in aged mice by attenuating an aberration of immune response and liver regeneration, partially via the mechanism of SIRT1-mediated repression of p66^shc expression.

Epigenetic Changes in Diabetes and Cardiovascular Risk

Cardiovascular complications remain the leading causes of morbidity and premature mortality in patients with diabetes mellitus. Studies in humans and preclinical models demonstrate lasting gene expression changes in the vasculopathies initiated by previous exposure to high glucose concentrations and the associated overproduction of reactive oxygen species. The molecular signatures of chromatin architectures that sensitize the genome to these and other cardiometabolic risk factors of the diabetic milieu are increasingly implicated in the biological memory underlying cardiovascular complications and now widely considered as promising therapeutic targets. Atherosclerosis is a complex heterocellular disease where the contributing cell types possess distinct epigenomes shaping diverse gene expression. Although the extent that pathological chromatin changes can be manipulated in human cardiovascular disease remains to be established, the clinical applicability of epigenetic interventions will be greatly advanced by a deeper understanding of the cell type-specific roles played by writers, erasers, and readers of chromatin modifications in the diabetic vasculature. This review details a current perspective of epigenetic mechanisms of macrovascular disease in diabetes mellitus and highlights recent key descriptions of chromatinized changes associated with persistent gene expression in endothelial, smooth muscle, and circulating immune cells relevant to atherosclerosis. Furthermore, we discuss the challenges associated with pharmacological targeting of epigenetic networks to correct abnormal or deregulated gene expression as a strategy to alleviate the clinical burden of diabetic cardiovascular disease.

An Overview on Current Issues and Challenges of Endothelial Progenitor Cell-Based Neovascularization in Patients with Diabetic Foot Ulcer

Diabetic foot ulcer's impaired wound healing, which leads to the development of chronic non-healing wounds and ultimately amputation, is a major problem worldwide. Although recently endothelial progenitor cell-derived cell therapy has been used as a therapeutic intervention to treat diabetic wounds, thereby promoting neovascularization, the results, however, are not satisfactory. In this article, we have discussed the several steps that are involved in the neovascularization process, which might be impaired during diabetes. In addition, we have also discussed the reported possible interventions to correct these impairments. Thus, we have summarized neovascularization as a process with a coordinated sequence of multiple steps and thus, there is the need of a combined therapeutic approach to achieve better treatment outcomes.

Sirtuins, a promising target in slowing down the ageing process

Ageing is a plastic process and can be successfully modulated by some biomedical approaches or pharmaceutics. In this manner it is possible to delay or even prevent some age-related pathologies. There are some defined interventions, which give promising results in animal models or even in human studies, resulting in lifespan elongation or healthspan improvement. One of the most promising targets for anti-ageing approaches are proteins belonging to the sirtuin family. Sirtuins were originally discovered as transcription repressors in yeast, however, nowadays they are known to occur in bacteria and eukaryotes (including mammals). In humans the family consists of seven members (SIRT1-7) that possess either mono-ADP ribosyltransferase or deacetylase activity. It is believed that sirtuins play key role during cell response to a variety of stresses, such as oxidative or genotoxic stress and are crucial for cell metabolism. Although some data put in question direct involvement of sirtuins in extending human lifespan, it was documented that proper lifestyle including physical activity and diet can influence healthspan via increasing the level of sirtuins. The search for an activator of sirtuins is one of the most extensive and robust topic of research. Some hopes are put on natural compounds, including curcumin. In this review we summarize the involvement and usefulness of sirtuins in anti-ageing interventions and discuss the potential role of curcumin in sirtuins regulation.

Sirtuin1-regulated lysine acetylation of p66Shc governs diabetes-induced vascular oxidative stress and endothelial dysfunction

The 66-kDa Src homology 2 domain-containing protein (p66Shc) is a master regulator of reactive oxygen species (ROS). It is expressed in many tissues where it contributes to organ dysfunction by promoting oxidative stress. In the vasculature, p66Shc-induced ROS engenders endothelial dysfunction. Here we show that p66Shc is a direct target of the Sirtuin1 lysine deacetylase (Sirt1), and Sirt1-regulated acetylation of p66Shc governs its capacity to induce ROS. Using diabetes as an oxidative stimulus, we demonstrate that p66Shc is acetylated under high glucose conditions and is deacetylated by Sirt1 on lysine 81. High glucose-stimulated lysine acetylation of p66Shc facilitates its phosphorylation on serine 36 and translocation to the mitochondria, where it promotes hydrogen peroxide production. Endothelium-specific transgenic and global knockin mice expressing p66Shc that is not acetylatable on lysine 81 are protected from diabetic oxidative stress and vascular endothelial dysfunction. These findings show that p66Shc is a target of Sirt1, uncover a unique Sirt1-regulated lysine acetylation-dependent mechanism that governs the oxidative function of p66Shc, and demonstrate the importance of p66Shc lysine acetylation in vascular oxidative stress and diabetic vascular pathophysiology.

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.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Ghrelin, MicroRNAs, and Critical Limb Ischemia: Hungering for a Novel Treatment Option

Critical limb ischemia (CLI) is the most severe manifestation of peripheral artery disease. It is characterized by chronic pain at rest, skin ulcerations, and gangrene tissue loss. CLI is a highly morbid condition, resulting in a severely diminished quality of life and a significant risk of mortality. The primary goal of therapy for CLI is to restore blood flow to the affected limb, which is only possible by surgery, but is inadvisable in up to 50% of patients. This subset of patients who are not candidates for revascularisation are referred to as "no-option" patients and are the focus of investigation for novel therapeutic strategies. Angiogenesis, arteriogenesis and vasculogenesis are the processes whereby new blood vessel networks form from the pre-existing vasculature and primordial cells, respectively. In therapeutic angiogenesis, exogenous stimulants are administered to promote angiogenesis and augment limb perfusion, offering a potential treatment option for "no option" patients. However, to date, very few clinical trials of therapeutic angiogenesis in patients with CLI have reported clinically significant results, and it remains a major challenge. Ghrelin, a 28-amino acid peptide, is emerging as a potential novel therapeutic for CLI. In pre-clinical models, exogenous ghrelin has been shown to induce therapeutic angiogenesis, promote muscle regeneration, and reduce oxidative stress via the modulation of microRNAs (miRs). miRs are endogenous, small, non-coding ribonucleic acids of ~20-22 nucleotides which regulate gene expression at the post-transcriptional level by either translational inhibition or by messenger ribonucleic acid cleavage. This review focuses on the mounting evidence for the use of ghrelin as a novel therapeutic for CLI, and highlights the miRs which orchestrate these physiological events.

P66Shc-Induced MicroRNA-34a Causes Diabetic Endothelial Dysfunction by Downregulating Sirtuin1

OBJECTIVE

Diabetes mellitus causes vascular endothelial dysfunction and alters vascular microRNA expression. We investigated whether endothelial microRNA-34a (miR-34a) leads to diabetic vascular dysfunction by targeting endothelial sirtuin1 (Sirt1) and asked whether the oxidative stress protein p66Shc governs miR-34a expression in the diabetic endothelium.

APPROACH AND RESULTS

MiR-34a is upregulated, and Sirt1 downregulated, in aortic endothelium of db/db and streptozotocin-induced diabetic mice. Systemic administration of miR-34a inhibitor, or endothelium-specific knockout of miR-34a, prevents downregulation of aortic Sirt1 and rescues impaired endothelium-dependent aortic vasorelaxation induced by diabetes mellitus. Moreover, overexpression of Sirt1 mitigates impaired endothelium-dependent vasorelaxation caused by miR-34a mimic ex vivo. Systemic infusion of miR-34a inhibitor or genetic ablation of endothelial miR-34a prevents downregulation of endothelial Sirt1 by high glucose. MiR-34a is upregulated, Sirt1 is downregulated, and oxidative stress (hydrogen peroxide) is induced in endothelial cells incubated with high glucose or the free fatty acid palmitate in vitro. Increase of hydrogen peroxide and induction of endothelial miR-34a by high glucose or palmitate in vitro is suppressed by knockdown of p66shc. In addition, overexpression of wild-type but not redox-deficient p66Shc upregulates miR-34a in endothelial cells. P66Shc-stimulated upregulation of endothelial miR-34a is suppressed by cell-permeable antioxidants. Finally, mice with global knockdown of p66Shc are protected from diabetes mellitus-induced upregulation of miR-34a and downregulation of Sirt1 in the endothelium.

CONCLUSIONS

These data show that hyperglycemia and elevated free fatty acids in the diabetic milieu recruit p66Shc to upregulate endothelial miR-34a via an oxidant-sensitive mechanism, which leads to endothelial dysfunction by targeting Sirt1.

Modulating putative endothelial progenitor cells for the treatment of endothelial dysfunction and cardiovascular complications in diabetes

Diabetes induces a decrease in the number and function of different pro-angiogenic cell types generically designated as putative endothelial progenitor cells (EPC), which encompasses cells from myeloid origin that act in a paracrine fashion to promote angiogenesis and putative "true" EPC that contribute to endothelial replacement. This not only compromises neovasculogenesis in ischemic tissues but also impairs, at an early stage, the reendotheliziation process at sites of injury, contributing to the development of endothelial dysfunction and cardiovascular complications. Hyperglycemia, insulin resistance and dyslipidemia promote putative EPC dysregulation by affecting the SDF-1/CXCR-4 and NO pathways and the p53/SIRT1/p66Shc axis that contribute to their mobilization, migration, homing and vasculogenic properties. To optimize the clinical management of patients with hypoglycemic agents, statins and renin-angiotensin system inhibitors, which display pleiotropic effects on putative EPC, is a first step to improve their number and angiogenic potential but specific strategies are needed. Among them, mobilizing therapies based on G-CSF, erythropoietin or CXCR-4 antagonism have been developed to increase putative EPC number to treat ischemic diseases with or without prior cell isolation and transplantation. Growth factors, genetic and pharmacological strategies are also evaluated to improve ex vivo cultured EPC function before transplantation. Moreover, pharmacological agents increasing in vivo the bioavailability of NO and other endothelial factors demonstrated beneficial effects on neovascularization in diabetic ischemic models but their effects on endothelial dysfunction remain poorly evaluated. More experiments are warranted to develop orally available drugs and specific agents targeting p66Shc to reverse putative EPC dysfunction in the expected goal of preventing endothelial dysfunction and diabetic cardiovascular complications.

Calorie restriction protects against experimental abdominal aortic aneurysms in mice

Abdominal aortic aneurysm (AAA), characterized by a localized dilation of the abdominal aorta, is a life-threatening vascular pathology. Because of the current lack of effective treatment for AAA rupture, prevention is of prime importance for AAA management. Calorie restriction (CR) is a nonpharmacological intervention that delays the aging process and provides various health benefits. However, whether CR prevents AAA formation remains untested. In this study, we subjected Apoe^-/- mice to 12 wk of CR and then examined the incidence of angiotensin II (AngII)-induced AAA formation. We found that CR markedly reduced the incidence of AAA formation and attenuated aortic elastin degradation in Apoe^-/- mice. The expression and activity of Sirtuin 1 (SIRT1), a key metabolism/energy sensor, were up-regulated in vascular smooth muscle cells (VSMCs) upon CR. Importantly, the specific ablation of SIRT1 in smooth muscle cells abolished the preventive effect of CR on AAA formation in Apoe^-/- mice. Mechanistically, VSMC-SIRT1-dependent deacetylation of histone H3 lysine 9 on the matrix metallopeptidase 2 (Mmp2) promoter was required for CR-mediated suppression of AngII-induced MMP2 expression. Together, our findings suggest that CR may be an effective intervention that protects against AAA formation.

Human paraoxonase gene cluster overexpression alleviates angiotensin II-induced cardiac hypertrophy in mice

Cardiac hypertrophy is the strongest predictor of the development of heart failure, and anti-hypertrophic treatment holds the key to improving the clinical syndrome and increasing the survival rates for heart failure. The paraoxonase (PON) gene cluster (PC) protects against atherosclerosis and coronary artery diseases. However, the role of PC in the heart is largely unknown. To evaluate the roles of PC in cardiac hypertrophy, transgenic mice carrying the intact human PON1, PON2, and PON3 genes and their flanking sequences were studied. We demonstrated that the PC transgene (PC-Tg) protected mice from cardiac hypertrophy induced by Ang II; these mice had reduced heart weight/body weight ratios, decreased left ventricular wall thicknesses and increased fractional shortening compared with wild-type (WT) control. The same protective tendency was also observed with an Apoe ^-/- background. Mechanically, PC-Tg normalized the disequilibrium of matrix metalloproteinases (MMPs)/tissue inhibitors of MMPs (TIMPs) in hypertrophic hearts, which might contribute to the protective role of PC-Tg in cardiac fibrosis and, thus, protect against cardiac remodeling. Taken together, our results identify a novel anti-hypertrophic role for the PON gene cluster, suggesting a possible strategy for the treatment of cardiac hypertrophy through elevating the levels of the PON gene family.

P66Shc-SIRT1 Regulation of Oxidative Stress Protects Against Cardio-cerebral Vascular Disease

Growing evidence shows that acute and chronic overproduction of reactive oxygen species (ROS) and increased oxidants under pathophysiologic circumstances are of vital importance in the development of cardio-cerebral vascular diseases (CCVDs). It has been revealed that the impact of ROS can be suppressed by sirtuin 1 (SIRT1), a member of the highly conserved nicotinamide adenine dinucleotide-dependent class III histone deacetylases through protecting endothelial cells from oxidative injury. Plenty of evidences indicate that p66Shc stimulates mitochondrial ROS generation through its oxidoreductase activity and plays a vital role in the pathophysiology of CCVDs. The link between SIRT and p66Shc, though not very clear yet, may be generally illustrated like this: SIRT1 negatively regulates the expression of p66Shc in transcriptional level. In this review, the authors aimed to discuss the link between the pathogenesis of CCVDs, the regulation of ROS, the interrelation between SIRT1 and p66Shc, and the protective effect of the proper regulation of p66Shc/SIRT1 on CCVDs. The imbalance between the elimination and production of ROS can lead to oxidative stress (OS). More and more evidence suggest that ROS pathological overproduction is closely connected to the genesis and growth of CCVDs. P66shc is a gene that controls ROS level, apoptosis induction, and lifespan. Lots of evidence also indicate a role for SIRT1 mediating OS responses through several ways including directly deacetylating some transcription factors that control anti-OS genes. SIRT1 downregulation can lead to a decreased deacetylation of p66shc gene promoter and can then result in p66shc transcription. SIRT1 binds to the promoter of p66Shc where it can deacetylate histone H3, which weakens the transcription and translation of p66shc.

Recombinant adenovirus of human p66Shc inhibits MCF-7 cell proliferation

The aim of this work was to construct a human recombinant p66Shc adenovirus and to investigate the inhibition of recombinant p66Shc adenovirus on MCF-7 cells. The recombinant adenovirus expression vector was constructed using the Adeno-X Adenoviral System 3. Inhibition of MCF-7 cell proliferation was determined by MTT. Intracellular ROS was measured by DCFH-DA fluorescent probes, and 8-OHdG was detected by ELISA. Cell apoptosis and the cell cycle were assayed by flow cytometry. Western blot were used to observe protein expression. p66Shc expression was upregulated in 4 cell lines after infection. The inhibitory effect of p66Shc recombinant adenovirus on MCF-7 cells was accompanied by enhanced ROS and 8-OHdG. However, no significant differences were observed in the cell apoptosis rate. The ratio of the cell cycle G2/M phase showed a significant increase. Follow-up experiments demonstrated that the expressions of p53, p-p53, cyclin B1 and CDK1 were upregulated with the overexpression of p66Shc. The Adeno-X Adenoviral System 3 can be used to efficiently construct recombinant adenovirus containing p66Shc gene, and the Adeno-X can inhibit the proliferation of MCF-7 cells by inducing cell cycle arrest at the G2/M phase. These results suggested that p66Shc may be a key target for clinical cancer therapy.

p66Shc: A novel biomarker of tubular oxidative injury in patients with diabetic nephropathy

Increased p66Shc expression has been associated with diabetic nephropathy (DN). However, whether p66Shc can serve as a potential biomarker for tubular oxidative injury in DN is unknown. We measured the expression of p66Shc in peripheral blood monocytes (PBMs) and renal biopsy tissues from DN patients and then analysed the relationship between p66Shc expression and the clinical characteristics of patients with DN. Patients were divided into 4 groups (class IIa, class IIb, class III and the control group). qPCR, Western blotting and immunohistochemistry were performed. The results showed that both p66Shc and p-p66Shc expression significantly increased in PBMs and kidney tissues of DN patients. Moreover, Spearman’s correlation and multiple regression analyses were carried out. A positive relationship between the p66Shc expression and oxidative stress was found. p66Shc and oxidative stress were significant predictors of the degree of tubular damage. In addition, p66Shc expression was positively correlated with the concentrations of β-NAG, UACR and 8-OHdG, low-density lipoprotein and blood glucose levels, and duration of diabetes in patients with DN from class IIa to class III. These data indicated that increased expression of p66Shc may serve as a therapeutic target and a novel biomarker of DN.

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.

Baicalein protects against the development of angiotensin II-induced abdominal aortic aneurysms by blocking JNK and p38 MAPK signaling

An abdominal aortic aneurysm (AAA) is a permanent, localized dilatation of the abdominal aorta. In western countries, the morbidity of AAA is approximately 8%. Currently, pharmacotherapies for AAA are limited. Here, we demonstrate that baicalein (BAI), the main component of the Chinese traditional drug "Huang Qin", attenuates the incidence and severity of AAA in Apoe (-/-) mice infused with angiotensin II (AngII). Mechanically, BAI treatment decreases AngII-induced reactive oxygen species (ROS) production in the aortic wall. Moreover, BAI inhibits inflammatory cell accumulation in the aortas of mice infused with AngII. It also inhibits AngII-induced activation of matrix metalloproteinase 2 (MMP-2) and MMP-9 to maintain elastin content in vivo. In addition, it blocks AngII cascade by downregulating angiotensin type 1 receptor (AT1R) and inhibiting mitogen-activated protein kinases (MAPKs). Taken together, our findings show that BAI is an effective agent for AAA prevention.

miR-34a-5p Inhibition Alleviates Intestinal Ischemia/Reperfusion-Induced Reactive Oxygen Species Accumulation and Apoptosis via Activation of SIRT1 Signaling

AIMS

Reactive oxygen species (ROS) generation and massive epithelial apoptosis are critical in the pathogenesis of intestinal ischemia/reperfusion (I/R) injury. We previously found that the Sirtuin 1 (SIRT1)-mediated antioxidant pathway was impaired in the intestine after I/R. Here, we investigate the potential role of SIRT1-targeting microRNAs (miRNAs) in regulating ROS accumulation and apoptosis in intestinal I/R, and the important role SIRT1 involved in.

RESULTS

C57BL/6 mice were subjected to intestinal I/R induced by occlusion of the superior mesenteric artery followed by reperfusion. Caco-2 cells were incubated under hypoxia/reoxygenation condition to mimic I/R in vivo. We find that SIRT1 is gradually repressed during the early reperfusion, and that this repression results in intestinal ROS accumulation and apoptosis. Using bioinformatics analysis and real-time PCR, we demonstrate that miR-34a-5p and miR-495-3p are significantly increased among the 41 putative miRNAs that can target SIRT1. Inhibition of miR-34a-5p, but not miR-495-3p, attenuates intestinal I/R injury, as demonstrated by repressing p66shc upregulation, manganese superoxide dismutase repression, and the caspase-3 activation in vitro and in vivo; it further alleviates systemic injury, as demonstrated by reducing inflammatory cytokine release, attenuating lung and liver lesions, and improving survival. Interestingly, SIRT1 plays an indispensable role in the protection afforded by miR-34a-5p inhibition.

INNOVATION

This study provides the first evidence of miRNAs in regulating oxidative stress and apoptosis in intestinal I/R.

CONCLUSION

miR-34a-5p knockdown attenuates intestinal I/R injury through promoting SIRT1-mediated suppression of epithelial ROS accumulation and apoptosis. This may represent a novel prophylactic approach to intestinal I/R injury. Antioxid. Redox Signal. 24, 961-973.

Cardiovascular Outcome Studies in Diabetes: How Do We Make Sense of These New Data?

Poorly controlled diabetes is characterized by premature cardiovascular mortality and morbidity. The mechanisms linking hyperglycemia with accelerated atherosclerotic disease have not been fully elucidated; however, are thought to be mediated through vascular inflammation, oxidative stress and endothelial dysfunction. The advent of incretin-based therapy, whether by increasing endogenous glucagon-like peptide (GLP)-1 and glucose-dependent inhibitory polypeptide by inhibition of their breakdown using di-peptidyl peptidase 4 inhibitors, or augmenting GLP-1 activity using either exendin-4-based drugs or synthetic GLP-1 analogs promised not just improvements in glycemic control, but improvements in endothelial function, lipid profiles and markers of vascular inflammation. As such, it was anticipated they would demonstrate cardiovascular benefit in those with diabetes, indeed early meta-analyses suggested cardiovascular events would be reduced. To date, however, this benefit has failed to materialize, indeed the cardiovascular outcome trials, whilst meeting their primary endpoint of cardiovascular safety, have failed to demonstrate any improvements in stroke or myocardial infarction. This review will explore the data and attempt to answer the question: what went wrong?

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.

Aging and Autophagy in the Heart

The aging population is increasing in developed countries. Because the incidence of cardiac disease increases dramatically with age, it is important to understand the molecular mechanisms through which the heart becomes either more or less susceptible to stress. Cardiac aging is characterized by the presence of hypertrophy, fibrosis, and accumulation of misfolded proteins and dysfunctional mitochondria. Macroautophagy (hereafter referred to as autophagy) is a lysosome-dependent bulk degradation mechanism that is essential for intracellular protein and organelle quality control. Autophagy and autophagic flux are generally decreased in aging hearts, and murine autophagy loss-of-function models develop exacerbated cardiac dysfunction that is accompanied by the accumulation of misfolded proteins and dysfunctional organelles. On the contrary, stimulation of autophagy generally improves cardiac function in mouse models of protein aggregation by removing accumulated misfolded proteins, dysfunctional mitochondria, and damaged DNA, thereby improving the overall cellular environment and alleviating aging-associated pathology in the heart. Increasing lines of evidence suggest that autophagy is required for many mechanisms that mediate lifespan extension, such as caloric restriction, in various organisms. These results raise the exciting possibility that autophagy may play an important role in combating the adverse effects of aging in the heart. In this review, we discuss the role of autophagy in the heart during aging, how autophagy alleviates age-dependent changes in the heart, and how the level of autophagy in the aging heart can be restored.

The combination of blueberry juice and probiotics reduces apoptosis of alcoholic fatty liver of mice by affecting SIRT1 pathway

Purpose

To explore the effects of the combination of blueberry juice and probiotics on the apoptosis of alcoholic fatty liver disease (AFLD).

Methods

Healthy C57BL/6J mice were used in the control group (CG). AFLD mice models were established with Lieber–DeCarli ethanol diet and evenly assigned to six groups with different treatments: MG (model), SI (SIRT1 [sirtuin type 1] small interfering RNA [siRNA]), BJ (blueberry juice), BJSI (blueberry juice and SIRT1 siRNA), BJP (blueberry juice and probiotics), and BJPSI (blueberry juice, probiotics, and SIRT1 siRNA). Hepatic tissue was observed using hematoxylin and eosin (HE) and Oil Red O (ORO) staining. Biochemical indexes of the blood serum were analyzed. The levels of SIRT1, caspase-3, forkhead box protein O1 (FOXO1), FasL (tumor necrosis factor ligand superfamily member 6), BAX, and Bcl-2 were measured by reverse transcription-polymerase chain reaction and Western blotting.

Results

HE and ORO staining showed that the hepatocytes were heavily destroyed with large lipid droplets in MG and SI groups, while the severity was reduced in the CG, BJ, and BJP groups (P<0.05). The levels of superoxide dismutase (SOD), reduced glutathione (GSH), and high-density lipoprotein-cholesterol (HDL-C) were increased in BJ and BJP groups when compared with the model group (P<0.05). In contrast, the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), total triglycerides (TGs), total cholesterol, low-density lipoprotein-cholesterol (LDL-C), and malondialdehyde (MDA) were lower in BJ and BJP groups than in the model group (P<0.05). The level of SIRT1 was increased, while the levels of FOXO1, phosphorylated FOXO1, acetylated FOXO1, FasL, caspase-3, BAX, and Bcl-2 were decreased in CG, BJ, and BJP groups (P<0.05). Meanwhile, SIRT1 silence resulted in increase of the levels of FOXO1, phosphorylated FOXO1, acetylated FOXO1, FasL, caspase-3, BAX, and Bcl-2.

Conclusion

The combination of blueberry juice and probiotics reduces apoptosis in AFLD by suppressing FOXO1, phosphorylated FOXO1, acetylated FOXO1, FasL, caspase-3, BAX, and Bcl-2 via the upregulation of SIRT1.

Gestational diabetes induces alterations of sirtuins in fetal endothelial cells

BACKGROUND

Gestational diabetes (GDM) has long-term consequences for the offspring. Sirtuins (SIRTs) are associated with vascular and metabolic functions. We studied the impact of GDM on SIRT activity and expression in fetal endothelial colony-forming cells (ECFCs) and human umbilical vein endothelial cells (HUVECs) from pregnancies complicated by GDM.

METHODS

ECFCs and HUVECs were isolated from cord and cord blood of 10 uncomplicated pregnancies (NPs) and 10 GDM pregnancies. Nicotinamidadenindinukleotid (NAD(+)) concentration, SIRT1 and SIRT3 activity, transcription levels of SIRT1, SIRT3, and SIRT4, and protein levels of SIRT1, SIRT3, and SIRT4 were determined in vitro with or without SIRT activators resveratrol (RSV) and paeonol.

RESULTS

Fetal ECFCs from GDM pregnancies showed a decreased NAD(+) concentration, reduced SIRT1 and SIRT3 activity, and lower transcription levels of SIRT1, SIRT3, and SIRT4. HUVECs from GDM pregnancies had decreased NAD(+) concentrations and transcription levels of SIRT1 and SIRT4. RSV markedly enhanced the expression and activity of SIRTs in ECFCs and HUVECs, while paeonol was active only in ECFCs.

CONCLUSION

A reduction of SIRT activity and expression in fetal endothelial cells provides potential mechanistic insights into the pathophysiology of long-term cardiovascular complications observed in the offspring of GDM pregnancies. SIRT activators can increase SIRT activity in ECFCs, which opens perspectives for new therapeutic targets.

Calorie Restriction Attenuates Monocrotaline-induced Pulmonary Arterial Hypertension in Rats

Calorie restriction (CR) is one of the most effective nonpharmacological interventions protecting against cardiovascular disease, such as hypertension in the systemic circulation. However, whether CR could attenuate pulmonary arterial hypertension (PAH) is largely unknown. The PAH model was developed by subjecting the rats to a single subcutaneous injection of monocrotaline. CR lowered mean pulmonary arterial pressure (mPAP) and reduced vascular remodeling and right ventricular hypertrophy in PAH rats. Meanwhile, CR attenuated endothelial dysfunction as evidenced by increased relaxation in response to acetylcholine. The beneficial effects of CR were associated with restored sirtuin-1 (SIRT1) expression and endothelial nitric oxide synthase (eNOS) phosphorylation and reduced eNOS acetylation in pulmonary arteries of PAH rats. To further clarify the role of SIRT1 in the protective effects of CR, adenoviral vectors for overexpression of SIRT1 were administered intratracheally at 1 day before monocrotaline injection. Overexpression of SIRT1 exhibited similar beneficial effects on mPAP and endothelial function, and increased eNOS phosphorylation and reduced eNOS acetylation in the absence of CR. Moreover, SIRT1 overexpression attenuated the increase in mPAP in hypoxia-induced PAH animals. Overall, the present data demonstrate that CR may serve as an effective treatment of PAH, and targeting the SIRT1/eNOS pathway may improve treatment of PAH.

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.

Diabetes-Induced Oxidative Stress in Endothelial Progenitor Cells May Be Sustained by a Positive Feedback Loop Involving High Mobility Group Box-1

Oxidative stress is considered to be a critical factor in diabetes-induced endothelial progenitor cell (EPC) dysfunction, although the underlying mechanisms are not fully understood. In this study, we investigated the role of high mobility group box-1 (HMGB-1) in diabetes-induced oxidative stress. HMGB-1 was upregulated in both serum and bone marrow-derived monocytes from diabetic mice compared with control mice. In vitro, advanced glycation end productions (AGEs) induced, expression of HMGB-1 in EPCs and in cell culture supernatants in a dose-dependent manner. However, inhibition of oxidative stress with N-acetylcysteine (NAC) partially inhibited the induction of HMGB-1 induced by AGEs. Furthermore, p66shc expression in EPCs induced by AGEs was abrogated by incubation with glycyrrhizin (Gly), while increased superoxide dismutase (SOD) activity in cell culture supernatants was observed in the Gly treated group. Thus, HMGB-1 may play an important role in diabetes-induced oxidative stress in EPCs via a positive feedback loop involving the AGE/reactive oxygen species/HMGB-1 pathway.

Protective effect of trans-δ-viniferin against high glucose-induced oxidative stress in human umbilical vein endothelial cells through the SIRT1 pathway

Oxidative stress plays a critical role in the pathogenesis of diabetic vascular complications. Trans-δ-viniferin (TVN), a polyphenolic compound, has recently attracted much attention as an antioxidant exhibiting a hypoglycemic potential. In the present study, we aimed at investigating the protective effect of TVN against high glucose-induced oxidative stress in human umbilical vein endothelial cells (HUVECs) and the potential mechanism involved. We found that TVN attenuated reactive oxygen species (ROS) production, increased catalase (CAT) activity and decreased malondialdehyde (MDA) levels to ameliorate cell survival induced by 35 mM glucose. Meanwhile, it inhibited high glucose-induced apoptosis by maintaining Ca(2+) and preserving mitochondrial membrane potential (MMP) levels. The immunoblot analysis indicated that TVN efficiently regulated the cleavage of caspase family, p53, Bax and Bcl-2, all mediated by SIRT1. Furthermore, the increased level of SIRT1 induced by TVN was inhibited by nicotinamide and siRNA-medicated SIRT1 silencing (si-SIRT1), thereby confirming the significant role of SIRT1 in these events. In conclusion, our results indicated that TVN efficiently reduced oxidative stress and maintained mitochondrial function related with activating SIRT1 in high glucose-treated HUVECs. It suggested that TVN is pharmacologically promising for treating diabetic cardiovascular complications.

The p66Shc protein controls redox signaling and oxidation-dependent DNA damage in human liver cells

The p66Shc protein mediates oxidative stress-related injury in multiple tissues. Steatohepatitis is characterized by enhanced oxidative stress-mediated cell damage. The role of p66Shc in redox signaling was investigated in human liver cells and alcoholic steatohepatitis. HepG2 cells with overexpression of wild-type or mutant p66Shc, with Ser36 replacement by Ala, were obtained through infection with recombinant adenoviruses. Reactive oxygen species and oxidation-dependent DNA damage were assessed by measuring dihydroethidium oxidation and 8-hydroxy-2'-deoxyguanosine accumulation into DNA, respectively. mRNA and protein levels of signaling intermediates were evaluated in HepG2 cells and liver biopsies from control and alcoholic steatohepatitis subjects. Exposure to H2O2 increased reactive oxygen species and phosphorylation of p66Shc on Ser36 in HepG2 cells. Overexpression of p66Shc promoted reactive oxygen species synthesis and oxidation-dependent DNA damage, which were further enhanced by H2O2. p66Shc activation also resulted in increased Erk-1/2, Akt, and FoxO3a phosphorylation. Blocking of Erk-1/2 activation inhibited p66Shc phosphorylation on Ser36. Increased p66Shc expression was associated with reduced mRNA levels of antioxidant molecules, such as NF-E2-related factor 2 and its target genes. In contrast, overexpression of the phosphorylation defective p66Shc Ala36 mutant inhibited p66Shc signaling, enhanced antioxidant genes, and suppressed reactive oxygen species and oxidation-dependent DNA damage. Increased p66Shc protein levels and Akt phosphorylation were observed in liver biopsies from alcoholic steatohepatitis compared with control subjects. In human alcoholic steatohepatitis, increased hepatocyte p66Shc protein levels may enhance susceptibility to DNA damage by oxidative stress by promoting reactive oxygen species synthesis and repressing antioxidant pathways.