SIRT1 in Endothelial Cells as a Novel Target for the Prevention of Early Vascular Aging

Endothelial Senescence in Neurological Diseases

Endothelial cells, which are highly dynamic cells essential to the vascular network, play an indispensable role in maintaining the normal function of the body. Several lines of evidence indicate that the phenotype associated with senescent endothelial cells causes or promotes some neurological disorders. In this review, we first discuss the phenotypic changes associated with endothelial cell senescence; subsequently, we provide an overview of the molecular mechanisms of endothelial cell senescence and its relationship with neurological disorders. For refractory neurological diseases such as stroke and atherosclerosis, we intend to provide some valid clues and new directions for clinical treatment options.

Early aging and premature vascular aging in chronic kidney disease

Aging is the progressive decline of body functions and a number of chronic conditions can lead to premature aging characterized by frailty, a diseased vasculature, osteoporosis, and muscle wasting. One of the major conditions associated with premature and accelerated aging is chronic kidney disease (CKD), which can also result in early vascular aging and the stiffening of the arteries. Premature vascular aging in CKD patients has been considered as a marker of prognosis of mortality and cardiovascular morbidity and therefore requires further attention. Oxidative stress, inflammation, advanced glycation end products, fructose, and an aberrant gut microbiota can contribute to the development of early aging in CKD patients. There are several key molecular pathways and molecules which play a role in aging and vascular aging including nuclear factor erythroid 2-related factor 2 (Nrf-2), AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1), and klotho. Potential therapeutic strategies can target these pathways. Future studies are needed to better understand the importance of premature aging and early vascular aging and to develop therapeutic alternatives for these conditions.

Inflammaging: mechanisms and role in the cardiac and vasculature

Aging triggers a wide range of cellular and molecular aberrations in the body, giving rise to inflammation and associated diseases. In particular, aging is associated with persistent low-grade inflammation even in absence of inflammatory stimuli, a phenomenon commonly referred to as 'inflammaging'. Accumulating evidence has revealed that inflammaging in vascular and cardiac tissues is associated with the emergence of pathological states such as atherosclerosis and hypertension. In this review we survey molecular and pathological mechanisms of inflammaging in vascular and cardiac aging to identify potential targets, natural therapeutic compounds, and other strategies to suppress inflammaging in the heart and vasculature, as well as in associated diseases such as atherosclerosis and hypertension.

A Biomolecular Toolbox for Precision Nanomotors

The application of nanomotors for cancer diagnosis and therapy is a new and exciting area of research, which when combined with precision nanomedicine, promises to solve many of the issues encountered by previous development of passive nanoparticles. The goal of this article is to introduce nanomotor and nanomedicine researchers to the deep pool of knowledge available regarding cancer cell biology and biochemistry, as well as provide a greater appreciation of the complexity of cell membrane compositions, extracellular surfaces, and their functional consequences. A short description of the nanomotor state-of-art for cancer therapy and diagnosis is first provided, as well as recommendations for future directions of the field. Then, a biomolecular targeting toolbox has been collated for researchers looking to apply their nanomaterial of choice to a biological setting, as well as providing a glimpse into currently available clinical therapies and technologies. This toolbox contains an overview of different classes of targeting molecules available for high affinity and specific targeting and cell surface targets to aid researchers in the selection of a clinical disease model and targeting methodology. It is hoped that this review will provide biological context, inspiration, and direction to future nanomotor and nanomedicine research.

Canagliflozin Delays Aging of HUVECs Induced by Palmitic Acid via the ROS/p38/JNK Pathway

Vascular aging is an important factor contributing to cardiovascular diseases, such as hypertension and atherosclerosis. Hyperlipidemia or fatty accumulation may play an important role in vascular aging and cardiovascular diseases. Canagliflozin (CAN), a sodium-glucose cotransporter inhibitor, can exert a cardiovascular protection effect that is likely independent of its hypoglycemic activities; however, the exact mechanisms remain undetermined. We hypothesized that CAN might have protective effects on blood vessels by regulating vascular aging induced by hyperlipidemia or fatty accumulation in blood vessel walls. In this study, which was undertaken on the basis of aging and inflammation, we investigated the protective effects and mechanisms of CAN in human umbilical vein endothelial cells induced by palmitic acid. We found that CAN could delay vascular aging, reduce the secretion of the senescence-associated secretory phenotype (SASP) and protect DNA from damage, as well as exerting an effect on the cell cycle of senescent cells. These actions likely occur through the attenuation of the excess reactive oxygen species (ROS) produced in vascular endothelial cells and/or down-regulation of the p38/JNK signaling pathway. In summary, our study revealed a new role for CAN as one of the sodium-dependent glucose transporter 2 inhibitors in delaying lipotoxicity-induced vascular aging by targeting the ROS/p38/JNK pathway, giving new medicinal value to CAN and providing novel therapeutic ideas for delaying vascular aging in patients with dyslipidemia.

SIRT1 pathway in Parkinson's disease: a faraway snapshot but so close

Silent information regulator (SIRT) has distinctive enzymatic activities and physiological functions to control cell-cycle progression, gene expression, and DNA stability by targeting histone and non-histone proteins. SIRT1 enhances synaptic formation and synaptic activity, and therefore, can reduce the progression of various degenerative brain diseases including Parkinson's disease (PD). SIRT1 activity is decreased by aging with a subsequent increased risk for the development of degenerative brain diseases. Inhibition of SIRT1 promotes inflammatory reactions since SIRT1 inhibits transcription of nuclear factor kappa B (NF-κB) which also inhibits SIRT1 activation via activation of microRNA and miR-34a which reduce NAD synthesis. SIRT1 is highly expressed in microglia as well as neurons, and has antioxidant and anti-inflammatory effects. Therefore, this review aimed to find the possible role of SIRT1 in PD neuropathology. SIRT1 has neuroprotective effects; therefore, downregulation of SIRT1 during aging promotes p53 expression and may increase the vulnerability of neuronal cell deaths. PD neuropathology is linked with the sequence of inflammatory changes and the release of pro-inflammatory cytokines due to the activation of inflammatory signaling pathways. In addition, oxidative stress, inflammatory disorders, mitochondrial dysfunction, and apoptosis contribute mutually to PD neuropathology. Thus, SIRT1 and SIRT1 activators play a crucial role in the mitigation of PD neuropathology through the amelioration of oxidative stress, inflammatory disorders, mitochondrial dysfunction, apoptosis, and inflammatory signaling pathways.

Resveratrol-like Compounds as SIRT1 Activators

The sirtuin 1 (SIRT1) activator resveratrol has emerged as a promising candidate for the prevention of vascular oxidative stress, which is a trigger for endothelial dysfunction. However, its clinical use is limited by low oral bioavailability. In this work, we have applied a previously developed computational protocol to identify the most promising derivatives from our in-house chemical library of resveratrol derivatives. The most promising compounds in terms of SIRT1 activation and oral bioavailability, predicted in silico, were evaluated for their ability to activate the isolated SIRT1 enzyme. Then, we assessed the antioxidant effects of the most effective derivative, compound 3d, in human umbilical vein endothelial cells (HUVECs) injured with H₂O₂ 100 µM. The SIRT1 activator 3d significantly preserved cell viability and prevented an intracellular reactive oxygen species increase in HUVECs exposed to the oxidative stimulus. Such effects were partially reduced in the presence of a sirtuin inhibitor, sirtinol, confirming the potential role of sirtuins in the activity of resveratrol and its derivatives. Although 3d appeared less effective than resveratrol in activating the isolated enzyme, the effects exhibited by both compounds in HUVECs were almost superimposable, suggesting a higher ability of 3d to cross cell membranes and activate the intracellular target SIRT1.

Endothelium-Derived Relaxing Factors and Endothelial Function: A Systematic Review

BACKGROUND

The endothelium plays a pivotal role in homeostatic mechanisms. It specifically modulates vascular tone by releasing vasodilatory mediators, which act on the vascular smooth muscle. Large amounts of work have been dedicated towards identifying mediators of vasodilation and vasoconstriction alongside the deleterious effects of reactive oxygen species on the endothelium. We conducted a systematic review to study the role of the factors released by the endothelium and the effects on the vessels alongside its role in atherosclerosis.

METHODS

A search was conducted with appropriate search terms. Specific attention was offered to the effects of emerging modulators of endothelial functions focusing the analysis on studies that investigated the role of reactive oxygen species (ROS), perivascular adipose tissue, shear stress, AMP-activated protein kinase, potassium channels, bone morphogenic protein 4, and P2Y2 receptor.

RESULTS

530 citations were reviewed, with 35 studies included in the final systematic review. The endpoints were evaluated in these studies which offered an extensive discussion on emerging modulators of endothelial functions. Specific factors such as reactive oxygen species had deleterious effects, especially in the obese and elderly. Another important finding included the shear stress-induced endothelial nitric oxide (NO), which may delay development of atherosclerosis. Perivascular Adipose Tissue (PVAT) also contributes to reparative measures against atherosclerosis, although this may turn pathological in obese subjects. Some of these factors may be targets for pharmaceutical agents in the near future.

CONCLUSION

The complex role and function of the endothelium is vital for regular homeostasis. Dysregulation may drive atherogenesis; thus, efforts should be placed at considering therapeutic options by targeting some of the factors noted.

Targeting SIRT1 Rescues Age- and Obesity-Induced Microvascular Dysfunction in Ex Vivo Human Vessels

BACKGROUND

Experimental evidence suggests a key role of SIRT1 (silent information regulator 1) in age- and metabolic-related vascular dysfunction. Whether these effects hold true in the human microvasculature is unknown. We aimed to investigate the SIRT1 role in very early stages of age- and obesity-related microvascular dysfunction in humans.

METHODS

Ninety-five subjects undergoing elective laparoscopic surgery were recruited and stratified based on their body mass index status (above or below 30 kg/m²) and age (above or below 40 years) in 4 groups: Young Nonobese, Young Obese, Old Nonobese, and Old Obese. We measured small resistance arteries' endothelial function by pressurized micromyography before and after incubation with a SIRT1 agonist (SRT1720) and a mitochondria reactive oxygen species (mtROS) scavenger (MitoTEMPO). We assessed vascular levels of mtROS and nitric oxide availability by confocal microscopy and vascular gene expression of SIRT1 and mitochondrial proteins by qPCR. Chromatin immunoprecipitation assay was employed to investigate SIRT1-dependent epigenetic regulation of mitochondrial proteins.

RESULTS

Compared with Young Nonobese, obese and older patients showed lower vascular expression of SIRT1 and antioxidant proteins (FOXO3 [forkhead box protein O3] and SOD2) and higher expression of pro-oxidant and aging mitochondria proteins p66^Shc and Arginase II. Old Obese, Young Obese and Old Nonobese groups endothelial dysfunction was rescued by SRT1720. The restoration was comparable to the one obtained with mitoTEMPO. These effects were explained by SIRT1-dependent chromatin changes leading to reduced p66^Shc expression and upregulation of proteins involved in mitochondria respiratory chain.

CONCLUSIONS

SIRT1 is a novel central modulator of the earliest microvascular damage induced by age and obesity. Through a complex epigenetic control mainly involving p66^Shc and Arginase II, it influences mtROS levels, NO availability, and the expression of proteins of the mitochondria respiratory chain. Therapeutic modulation of SIRT1 restores obesity- and age-related endothelial dysfunction. Early targeting of SIRT1 might represent a crucial strategy to prevent age- and obesity-related microvascular dysfunction.

Endothelial SIRT1 as a Target for the Prevention of Arterial Aging: Promises and Challenges

ABSTRACT

SIRT1, a member of the sirtuin family of longevity regulators, possesses potent activities preventing vascular aging. The expression and function of SIRT1 in endothelial cells are downregulated with age, in turn causing early vascular aging and predisposing various vascular abnormalities. Overexpression of SIRT1 in the vascular endothelium prevents aging-associated endothelial dysfunction and senescence, thus the development of hypertension and atherosclerosis. Numerous efforts have been directed to increase SIRT1 signaling as a potential strategy for different aging-associated diseases. However, the complex mechanisms underlying the regulation of SIRT1 have posed a significant challenge toward the design of specific and effective therapeutics. This review aimed to provide a summary on the regulation and function of SIRT1 in the vascular endothelium and to discuss the different approaches targeting this molecule for the prevention and treatment of age-related cardiovascular and cerebrovascular diseases.

Genistein alleviates H2O2-induced senescence of human umbilical vein endothelial cells via regulating the TXNIP/NLRP3 axis

CONTEXT

Genistein (Gen) has shown protective effects against ageing process.

OBJECTIVE

To explore the role of Gen on the senescence of H₂O₂-induced human umbilical vein endothelial cells (HUVECs) and investigate the possible mechanism.

MATERIALS AND METHODS

HUVECs were treated with different concentrations of H₂O₂ (50, 100, 200 and 400 μmol/L) for 1 h or Gen administration (20, 40, 80 and 160 μg/mL) for 24 h. Functional experiments (cell counting kit-8, β-galactosidase staining and flow cytometry) were used to detect the effect of Gen on H₂O₂-induced HUVECs. After HUVECs were transfected with TXNIP overexpression plasmids, the expression of p16, p21, thioredoxin-interacting protein (TXNIP), nucleotide-binding and oligomerization domain-like receptor 3 (NLRP3), cleaved caspase-3 and cleaved caspase-1 in HUVECs were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot.

RESULTS

H₂O₂ (200 and 400 μmol/L) inhibited the proliferation of HUVECs. At concentrations of >50 μmol/L, H₂O₂ induced the cell cycle progression arrests in G1 phase and promoted cell senescence of HUVECs. Gen had no obvious cytotoxicity to HUVECs below 160 µg/mL. H₂O₂-induced HUVEC senescence and the expression of TXNIP and NLRP3 in HUVECs were down-regulated by Gen (40 and 80 µg/mL). Expressions of TXNIP and NLRP3 in HUVECs were up-regulated by H₂O₂ but down-regulated by Gen. Overexpressed TXNIP partially reversed the suppressive effect of Gen on H₂O₂-induced senescence and apoptosis of HUVECs. Expressions of p16, p21, TXNIP, NLRP3, cleaved caspase-3 and cleaved caspase-1 in H₂O₂-treated HUVECs were inhibited by Gen, while the inhibition as such was partially reversed by overexpressed TXNIP.

DISCUSSION AND CONCLUSIONS

H₂O₂-induced HUVEC senescence was alleviated by Gen via suppressing the TXNIP/NLRP3 axis, which may offer a potential therapeutic approach for improving HUVEC senescence and provide a new direction for the treatment of cardiovascular disease.

Genistein suppresses ox-LDL-elicited oxidative stress and senescence in HUVECs through the SIRT1-p66shc-Foxo3a pathways

The anti-senescence function of genistein is related to inhibiting oxidative stress, however, the mechanism has not been clarified. The present study aimed to explore the effects of genistein on oxidized low-density lipoprotein (ox-LDL)-induced endothelial senescence and the role of the sirtuin-1 (SIRT1)-66-kDa Src homology 2 domain-containing protein (p66Shc)-forkhead box protein O3 (Foxo3a) pathways in the process. In this paper, human umbilical vein endothelial cells were pretreated with 1000 nM genistein for 30 min and then incubated with 50 mg/L ox-LDL for another 12 h; meanwhile, the functions of adenovirus-mediated overexpression of p66shc and small interfering RNA-mediated silencing of SIRT1 were investigated. Results showed that genistein pretreatment alleviated ox-LDL-induced mitochondrial reactive oxygen species, the levels of oxidatively modified DNA (8-OHdG) and pai-1, and the activity of SA-β-gal, which was associated with mitigating p66shc. Further studies indicated the inhibitory effect of genistein on p66shc was correlated with suppressing the acetylation and phosphorylation of p66shc, and ameliorating its mitochondrial translocation by activating SIRT1. Moreover, the inactivated p66shc could enhance the activity of Foxo3a via restraining the phosphorylation and triggering nucleus accumulation. The study demonstrates genistein could prevent ox-LDL-induced mitochondrial oxidative stress and senescence through the SIRT1-p66shc-Foxo3a pathways.

Effect of the traditional Chinese medicine Pinggan-Qianyang decoction on SIRT1-PTEN signaling in vascular aging in spontaneously hypertensive rats

Age-related functional decline is a physiological phenomenon that occurs in all organ systems. However, the acceleration and early occurrence of this process are observed in cardiovascular pathologies, including hypertension. This study aimed to investigate SIRT1-PTEN signaling in aortic tissue from spontaneously hypertensive rats (SHRs) and changes in SIRT1 and PTEN expression following treatment with Pinggan-Qianyang decoction (PGQYD) and explore the mechanism involved in the treatment of hypertensive vascular aging with traditional Chinese medicine. In this study, we used two rat models: spontaneously hypertensive rats (SHRs) at 14 and 64 weeks of age and WKY rats at 64 weeks of age. The degree of irritability and rotation tolerance time were evaluated to determine the effects of PGQYD on animal behavior. The morphology of the thoracic aorta was examined by hematoxylin-eosin (HE) and Masson staining and electron microscopy. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and superoxide dismutase (SOD) and anti-superoxide anion content were detected. Senescence-associated β-galactosidase (SA-β-Gal) staining was used to observe the thoracic aorta during vascular aging. RT-qPCR, immunofluorescence, and Western blot analysis were performed to detect changes in the mRNA and protein expression of p53, p21, SIRT1, and PTEN in rat aortic tissues. Behavioral tests and histological and morphological analyses showed the remarkable amelioration of vascular aging after PGQYD treatment compared with that in the older SHRs. Moreover, PGQYD significantly decreased vascular aging in SHRs, as indicated by reduced SA-β-Gal staining, NADPH oxidase activity, and p53 and p21 expression, and increased anti-superoxide anion and SOD content. Furthermore, PGQYD increased SIRT1 and PTEN expression, but the downregulated expression of SIRT1 induced by a SIRT1 inhibitor abolished the PGQYD-induced antiaging effects on gene expression and antioxidant activity and enhanced PTEN expression. PGQYD could ameliorate vascular aging effects in SHRs, which may have been mediated via the regulation of SIRT1-PTEN signaling in aortic tissue.

Nicotinamide N-methyltransferase in endothelium protects against oxidant stress-induced endothelial injury

Nicotinamide N-methyltransferase (NNMT, EC 2.1.1.1.) plays an important role in the growth of many different tumours and is also involved in various non-neoplastic disorders. However, the presence and role of NNMT in the endothelium has yet to be specifically explored. Here, we characterized the functional activity of NNMT in the endothelium and tested whether NNMT regulates endothelial cell viability. NNMT in endothelial cells (HAEC, HMEC-1 and EA.hy926) was inhibited using two approaches: pharmacological inhibition of the enzyme by NNMT inhibitors (5-amino-1-methylquinoline - 5MQ and 6-methoxynicotinamide - JBSF-88) or by shRNA-mediated silencing. Functional inhibition of NNMT was confirmed by LC/MS/MS-based analysis of impaired MNA production. The effects of NNMT inhibition on cellular viability were analyzed in both the absence and presence of menadione. Our results revealed that all studied endothelial lines express relatively high levels of functionally active NNMT compared with cancer cells (MDA-MB-231). Although the aldehyde oxidase 1 enzyme was also expressed in the endothelium, the further metabolites of N1-methylnicotinamide (N1-methyl-2-pyridone-5-carboxamide and N1-methyl-4-pyridone-3-carboxamide) generated by this enzyme were not detected, suggesting that endothelial NNMT-derived MNA was not subsequently metabolized in the endothelium by aldehyde oxidase 1. Menadione induced a concentration-dependent decrease in endothelial viability as evidenced by a decrease in cell number that was associated with the upregulation of NNMT and SIRT1 expression in the nucleus in viable cells. The suppression of the NNMT activity either by NNMT inhibitors or shRNA-based silencing significantly decreased the endothelial cell viability in response to menadione. Furthermore, NNMT inhibition resulted in nuclear SIRT1 expression downregulation and upregulation of the phosphorylated form of SIRT1 on Ser47. In conclusion, our results suggest that the endothelial nuclear NNMT/SIRT1 pathway exerts a cytoprotective role that safeguards endothelial cell viability under oxidant stress insult.

Endothelial Dysfunction in Atherosclerotic Cardiovascular Diseases and Beyond: From Mechanism to Pharmacotherapies

The endothelium, a cellular monolayer lining the blood vessel wall, plays a critical role in maintaining multiorgan health and homeostasis. Endothelial functions in health include dynamic maintenance of vascular tone, angiogenesis, hemostasis, and the provision of an antioxidant, anti-inflammatory, and antithrombotic interface. Dysfunction of the vascular endothelium presents with impaired endothelium-dependent vasodilation, heightened oxidative stress, chronic inflammation, leukocyte adhesion and hyperpermeability, and endothelial cell senescence. Recent studies have implicated altered endothelial cell metabolism and endothelial-to-mesenchymal transition as new features of endothelial dysfunction. Endothelial dysfunction is regarded as a hallmark of many diverse human panvascular diseases, including atherosclerosis, hypertension, and diabetes. Endothelial dysfunction has also been implicated in severe coronavirus disease 2019. Many clinically used pharmacotherapies, ranging from traditional lipid-lowering drugs, antihypertensive drugs, and antidiabetic drugs to proprotein convertase subtilisin/kexin type 9 inhibitors and interleukin 1β monoclonal antibodies, counter endothelial dysfunction as part of their clinical benefits. The regulation of endothelial dysfunction by noncoding RNAs has provided novel insights into these newly described regulators of endothelial dysfunction, thus yielding potential new therapeutic approaches. Altogether, a better understanding of the versatile (dys)functions of endothelial cells will not only deepen our comprehension of human diseases but also accelerate effective therapeutic drug discovery. In this review, we provide a timely overview of the multiple layers of endothelial function, describe the consequences and mechanisms of endothelial dysfunction, and identify pathways to effective targeted therapies. SIGNIFICANCE STATEMENT: The endothelium was initially considered to be a semipermeable biomechanical barrier and gatekeeper of vascular health. In recent decades, a deepened understanding of the biological functions of the endothelium has led to its recognition as a ubiquitous tissue regulating vascular tone, cell behavior, innate immunity, cell-cell interactions, and cell metabolism in the vessel wall. Endothelial dysfunction is the hallmark of cardiovascular, metabolic, and emerging infectious diseases. Pharmacotherapies targeting endothelial dysfunction have potential for treatment of cardiovascular and many other diseases.

Endothelium as a Source and Target of H2S to Improve Its Trophism and Function

The vascular endothelium consists of a single layer of squamous endothelial cells (ECs) lining the inner surface of blood vessels. Nowadays, it is no longer considered as a simple barrier between the blood and vessel wall, but a central hub to control blood flow homeostasis and fulfill tissue metabolic demands by furnishing oxygen and nutrients. The endothelium regulates the proper functioning of vessels and microcirculation, in terms of tone control, blood fluidity, and fine tuning of inflammatory and redox reactions within the vessel wall and in surrounding tissues. This multiplicity of effects is due to the ability of ECs to produce, process, and release key modulators. Among these, gasotransmitters such as nitric oxide (NO) and hydrogen sulfide (H₂S) are very active molecules constitutively produced by endotheliocytes for the maintenance and control of vascular physiological functions, while their impairment is responsible for endothelial dysfunction and cardiovascular disorders such as hypertension, atherosclerosis, and impaired wound healing and vascularization due to diabetes, infections, and ischemia. Upregulation of H₂S producing enzymes and administration of H₂S donors can be considered as innovative therapeutic approaches to improve EC biology and function, to revert endothelial dysfunction or to prevent cardiovascular disease progression. This review will focus on the beneficial autocrine/paracrine properties of H₂S on ECs and the state of the art on H₂S potentiating drugs and tools.

LncRNA Sirt1-AS upregulates Sirt1 to attenuate aging related deep venous thrombosis

Aging is associated with the increased incidence of deep venous thrombosis (DVT), resulting in significant morbidity and mortality in the elderly, but the underlying mechanism is elusive. Silent information regulator 1 (Sirt1) is linked to the senescence, inflammation, oxidative stress and platelet adhesion of endothelial cells. Here we showed that DVT was associated with the senescence of endothelium and lower expression of Sirt1. Furthermore, Sirt1 could inhibit endothelial senescence and reduce the occurrence of DVT. Interestingly, we found antisense long non-coding RNA (lncRNA Sirt1-AS) upregulated Sirt1, decreased the expression of senescence and DVT associated biomarkers in human vascular endothelial cells (HUVECs). In addition, lncRNA Sirt1-AS overexpression alleviated DVT through upregulating Sirt1 and thereby inducing Foxo3a degradation. In conclusion, our findings demonstrate that lncRNA Sirt1-AS may be a potential new biomarker for DVT.

Myocyte enhancer factor 2A delays vascular endothelial cell senescence by activating the PI3K/p-Akt/SIRT1 pathway

Myocyte enhancer factor 2A (MEF2A) dysfunction is closely related to the occurrence of senile diseases such as cardiocerebrovascular diseases, but the underlying molecular mechanism is unclear. Here, we studied the effects of MEF2A on the senescent phenotype of vascular endothelial cells (VEC) and downstream signaling pathway, and the association between plasma MEF2A levels and coronary artery disease (CAD). Results showed that MEF2A silencing promoted cell senescence and down-regulated PI3K/p-AKT/Sirtuin 1 (SIRT1) expression. MEF2A overexpression delayed cell senescence and up-regulated PI3K/p-AKT/SIRT1. Hydrogen peroxide (H₂O₂) treatment induced cellular senescence and down-regulated the expression of MEF2A and PI3K/p-AKT/SIRT1. MEF2A overexpression inhibited cellular senescence and the down-regulation of PI3K/p-AKT/SIRT1 induced by H₂O₂. Further study revealed that MEF2A directly up-regulated the expression of PIK3CA and PIK3CG through MEF2 binding sites in the promoter region. Pearson correlation and logistic regression analysis showed that the plasma level of MEF2A was negatively correlated with CAD, and with age in the controls. These results suggested that MEF2A can directly up-regulate PI3K gene expression, and one of the molecular mechanisms of delaying effect of MEF2A on VEC cell senescence was SIRT1-expression activation through the PI3K/p-Akt pathway. Moreover, the plasma MEF2A levels may be a potential biomarker for CAD risk prediction.

Hepatoprotective Effect of Citrus aurantium L. Against APAP-induced Liver Injury by Regulating Liver Lipid Metabolism and Apoptosis

Acetaminophen (APAP) refers to a medication used to manage pain and fever symptoms, but it always causes liver injury when overdosed. Zhishi, dried young fruit of Citrus aurantium L., is a famous Citrus herbal medicine in Asian countries which is rich in dietary phenolic substances. In this study, the mechanism of Zhishi protected against APAP-induced liver injury was studied more deeply by metabolomic strategy and pharmacological study. The metabolomics results demonstrated that Zhishi can prevent the APAP-induced liver injury model by regulating liver metabolic disorders in glycerophospholipid metabolism, fatty acid biosynthesis and glycerolipid metabolism. Moreover, it is confirmed that Zhishi blocked apoptosis of APAP-induced BRL-3A cell by simultaneously regulating p53 up-regulated apoptosis regulator (PUMA), AMPK-SIRT1 and JNK1 signaling pathways. Our findings indicated that Zhishi exhibited a hepaprotective effect against APAP-induced liver necrosis by inhibiting the PUMA and reversing disorder of liver lipid metabolism which could assist in improving the clinical outcomes of chemical-induced liver injury.

Activation of Transient Receptor Potential Channel Vanilloid 4 by DPP-4 (Dipeptidyl Peptidase-4) Inhibitor Vildagliptin Protects Against Diabetic Endothelial Dysfunction

Endothelial dysfunction is an early step to the progression of cardiovascular diseases in diabetes. Apart from their anti-diabetic action, DPP-4 (dipeptidyl peptidase-4) inhibitors also reduce cardiovascular events in diabetic patients. However, the underlying mechanism of the beneficial effect of DPP-4 inhibitor on endothelial function is still obscure. In this study, we intervened type 1 or 2 diabetic model mice with vildagliptin for 4 weeks and measured the vascular reactivity. We found that vildagliptin improved endothelium-dependent vasodilation in diabetic mice independent of GLP-1 (glucagonlike peptide-1), but this effect was blocked by a SIRT1 (Sirtuin 1) inhibitor, Ex527. Mechanistically, vildagliptin-activated Transient Receptor Potential Channel Vanilloid 4 (TRPV4) to promote extracellular calcium uptake in endothelial cells, which activated AMPK (AMP-activated protein kinase)/SIRT1 pathway to counteract hyperglycemia-induced endothelial reactive oxygen species generation and senescence. Vildagliptin directly binds to TRPV4 by forming a hydrogen bond, which is critical to vildagliptin-evoked endothelial calcium intake. Knockout or inhibition of TRPV4 erased the beneficial role of vildagliptin. In addition, activation of SIRT1 by SRT1720 improved endothelial function independent of TRPV4 and reduced TRPV4 transcription to maintain an appropriate calcium level. In summary, our findings prove that vildagliptin protects against hyperglycemia-induced endothelial dysfunction by activating TRPV4-meditaed Ca²⁺ uptake, which helps to re-understand the mechanism of DPP-4 inhibitors and expand the therapeutic scope.

B Vitamins and Fatty Acids: What Do They Share with Small Vessel Disease-Related Dementia?

Many studies have been written on vitamin supplementation, fatty acid, and dementia, but results are still under debate, and no definite conclusion has yet been drawn. Nevertheless, a significant amount of lab evidence confirms that vitamins of the B group are tightly related to gene control for endothelium protection, act as antioxidants, play a co-enzymatic role in the most critical biochemical reactions inside the brain, and cooperate with many other elements, such as choline, for the synthesis of polyunsaturated phosphatidylcholine, through S-adenosyl-methionine (SAM) methyl donation. B-vitamins have anti-inflammatory properties and act in protective roles against neurodegenerative mechanisms, for example, through modulation of the glutamate currents and a reduction of the calcium currents. In addition, they also have extraordinary antioxidant properties. However, laboratory data are far from clinical practice. Many studies have tried to apply these results in everyday clinical activity, but results have been discouraging and far from a possible resolution of the associated mysteries, like those represented by Alzheimer's disease (AD) or small vessel disease dementia. Above all, two significant problems emerge from the research: No consensus exists on general diagnostic criteria-MCI or AD? Which diagnostic criteria should be applied for small vessel disease-related dementia? In addition, no general schema exists for determining a possible correct time of implementation to have effective results. Here we present an up-to-date review of the literature on such topics, shedding some light on the possible interaction of vitamins and phosphatidylcholine, and their role in brain metabolism and catabolism. Further studies should take into account all of these questions, with well-designed and world-homogeneous trials.

Epigenetics: The master control of endothelial cell fate in cancer

The development of new blood vessels from pre-existing vasculature is called angiogenesis. The growth of tumors depends on a network of supplying vessels that provide them with oxygen and nutrients. Pro-angiogenic factors that are secreted by tumors will trigger the sprouting of nearby existing blood vessels towards themselves and therefore researchers have developed targeted therapy towards these pro-angiogenic proteins to inhibit angiogenesis. However, certain pro-angiogenic proteins tend to bypass the inhibition. Thus, instead of targeting these expressed proteins, research towards angiogenesis inhibition had been focused on a deeper scale, epigenetic modifications. Epigenetic regulatory mechanisms are a heritable change in a sequence of stable but reversible gene function modification yet do not affect the DNA primary sequence directly. Methylation of DNA, modification of histone and silencing of micro-RNA (miRNA)-associated gene are currently considered to initiate and sustain epigenetic changes. Recent findings on the subject matter have provided an insight into the mechanism of epigenetic modifications, thus this review aims to present an update on the latest studies.

Age-Related Impairment of Structure and Function of Iliac Artery Endothelium in Rats Is Improved by Elevated Fluid Shear Stress

Background

Aging plays an important role in endothelial dysfunction. Fluid shear stress (FSS) can activate endothelial cells (ECs). Herein, we tested the hypothesis that this endothelial impairment could be improved by elevated FSS (EFSS) in aged rats.

Material/Methods

EFSS was created through ligation of the unilateral common iliac artery in 20-−month-old rats, evaluated by measuring blood flow velocity with Doppler spectrum. The effect of FSS on aged ECs was examined by senescence-associated β-galactosidase (SA-β-Gal) staining, ultrastructural observation, and immunostaining and qPCR analysis of eNOS and SIRT1 expression on both the mRNA and protein levels.

Results

(1) FSS was significantly increased in the right common iliac artery (RCIA) in rats with the ligation of the left common iliac artery (LCIA). (2) SA-β-Gal staining was significantly attenuated by EFSS in the RCIA of aged rats. (3) Ultrastructural observation showed that ECs in the RCIA of normal aged rats became irregular and enlarged, with increasingly polypoid nuclei and fewer mitochondria, whereas ECs in the RCIA of aged rats with LCIA ligation became more prominent and contained more mitochondria. (4) eNOS and SIRT1 expression in the RCIA of aged rats with LCIA ligation was significantly upregulated compared with that in control group rats.

Conclusions

The present study for the first time shows that EFSS has the ability to improve age-related impairment of endothelial structure and functions.

MHY2233 Attenuates Replicative Cellular Senescence in Human Endothelial Progenitor Cells via SIRT1 Signaling

Cardiovascular diseases (CVDs) are a major cause of death worldwide. Due to the prevalence of many side effects and incomplete recovery from pharmacotherapies, stem cell therapy is being targeted for the treatment of CVDs. Among the different types of stem cells, endothelial progenitor cells (EPCs) have great potential. However, cellular replicative senescence decreases the proliferation, migration, and overall function of EPCs. Sirtuin 1 (SIRT1) has been mainly studied in the mammalian aging process. MHY2233 is a potent synthetic SIRT1 activator and a novel antiaging compound. We found that MHY2233 increased the expression of SIRT1, and its deacetylase activity thereby decreased expression of the cellular senescence biomarkers, p53, p16, and p21. In addition, MHY2233 decreased senescence-associated beta-galactosidase- (SA-β-gal-) positive cells and senescence-associated secretory phenotypes (SASPs), such as the secretion of interleukin- (IL-) 6, IL-8, IL-1α, and IL-1β. MHY2233 treatment protected senescent EPCs from oxidative stress by decreasing cellular reactive oxygen species (ROS) levels, thus enhancing cell survival and function. The angiogenesis, proliferation, and migration of senescent EPCs were enhanced by MHY2233 treatment. Thus, MHY2233 reduces replicative and oxidative stress-induced senescence in EPCs. Therefore, this novel antiaging compound MHY2233 might be considered a potent therapeutic agent for the treatment of age-associated CVDs.

Genistein protects against ox-LDL-induced senescence through enhancing SIRT1/LKB1/AMPK-mediated autophagy flux in HUVECs

The anti-senescence activity of genistein is associated with inducing autophagy; however, the underlying mechanisms are not fully understood. In this study, human umbilical vein endothelial cells (HUVECs) were pretreated with genistein (1000 nM) for 30 min and then exposed to ox-LDL (50 mg/L) for another 12 h. The study found that genistein inhibited the ox-LDL-induced senescence (reducing the levels of P16 and P21 protein, and the activity of SA-β-gal); meanwhile, the effect of genistein was bound up with enhancing autophagic flux (increasing LC3-II, and decreasing the level of P62, p-mTOR and p-P70S6K). Moreover, SIRT1/LKB1/AMPK pathway was involved in genistein accelerating autophagic flux and mitigating senescence in HUVECs. The present study illustrated that genistein was a promising therapeutic agent to delay aging process and extend longevity.

Endothelial SIRT1 prevents age-induced impairment of vasodilator responses by enhancing the expression and activity of soluble guanylyl cyclase in smooth muscle cells

Aims

Aged arteries are characterized by attenuated vasodilator and enhanced vasoconstrictor responses, which contribute to the development of diseases such as arterial hypertension, atherosclerosis, and heart failure. SIRT1 is a longevity regulator exerting protective functions against vascular ageing, although the underlying mechanisms remain largely unknown. This study was designed to elucidate the signalling pathways involved in endothelial SIRT1-mediated vasodilator responses in the arteries of young and old mice. In particular, the contributions of nitric oxide (NO), endothelial NO synthase (eNOS), cyclooxygenase (COX), and/or soluble guanylyl cyclase (sGC) were examined.

Methods and results

Wild type (WT) or eNOS knockout (eKO) mice were cross-bred with those overexpressing human SIRT1 selectively in the vascular endothelium (EC-SIRT1). Arteries were collected from the four groups of mice (WT, EC-SIRT1, eKO, and eKO-SIRT1) to measure isometric relaxations/contractions in response to various pharmacological agents. Reduction of NO bioavailability, hyper-activation of COX signalling, and down-regulation of sGC collectively contributed to the decreased vasodilator and increased vasoconstrictor responses in arteries of old WT mice. Overexpression of endothelial SIRT1 did not block the reduction in NO bioavailability but attenuated the hyper-activation of COX-2, thus protecting mice from age-induced vasoconstrictor responses in arteries of EC-SIRT1 mice. Deficiency of eNOS did not affect endothelial SIRT1-mediated anti-contractile activities in arteries of eKO-SIRT1 mice. Mechanistic studies revealed that overexpression of endothelial SIRT1 enhanced Notch signalling to up-regulate sGCβ1 in smooth muscle cells. Increased expression and activity of sGC prevented age-induced hyper-activation of COX-2 as well as the conversion of endothelium-dependent relaxations to contractions in arteries of EC-SIRT1 mice.

Conclusion

Age-induced down-regulation of sGC and up-regulation of COX-2 in arteries are at least partly attributable to the loss-of-endothelial SIRT1 function. Enhancing the endothelial expression and function of SIRT1 prevents early vascular ageing and maintains vasodilator responses, thus representing promising drug targets for cardiovascular diseases.

DPP-4 inhibitors promote proliferation and migration of rat brain microvascular endothelial cells under hypoxic/high-glucose conditions, potentially through the SIRT1/HIF-1/VEGF pathway

BACKGROUND

Vascular disease in diabetes, for example, stroke, presents a significant public health burden. Recently, the dipeptidyl peptidase 4 (DPP-4) inhibitor linagliptin has been found to counteract stroke among diabetic patients, showing great promise in drug repurposing and indication expansion. However, the molecular basis of this protection mechanism remains unknown.

METHODS

The expression and localization of DPP-4 in rat brain microvascular endothelial cells (rBMVECs) were assessed with immunofluorescent staining and Western blotting. The effects of DPP-4 inhibitors on cell proliferation and migration of rBMVECs were determined using MTT and transwell assays, separately. The influence of DPP-4 inhibition on the expression of molecular markers (eg, VEGF, eNOS, HIF-1α. SIRT1) was examined at both mRNA and protein levels with qRT-PCR and Western blotting, individually.

RESULTS

DPP-4 inhibitors (40 nmol/L linagliptin, 30 μmol/L berberine) offer protection from hypoxia/high glucose induced impairments in the proliferation and migration of rBMVECs. Treatment with DPP-4 inhibitors counteracted the attenuating effects of hypoxic/high-glucose conditions on the expression of VEGF, eNOS, HIF-1α, and SIRT1, which can be completely eliminated by the inhibition of SIRT1 with 1 mmol/L nicotinamide.

CONCLUSIONS

The protection of rBMVECs from hypoxia/high-glucose induced impairment by DPP-4 inhibitors may be mediated by the SIRT1/HIF-1α/VEGF pathway.

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

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

Endothelial SIRT1 prevents adverse arterial remodeling by facilitating HERC2-mediated degradation of acetylated LKB1

Aims-SIRT1 exerts potent activity against cellular senescence and vascular ageing. By decreasing LKB1 protein levels, it promotes the survival and regeneration of endothelial cells. The present study aims to investigate the molecular mechanisms underlying SIRT1-mediated LKB1 degradation for the prevention of vascular ageing.

Methods and Results-Co-immunoprecipitation assay demonstrated that SIRT1, via its amino-terminus, binds to the DOC domain of HERC2 [HECT and RLD domain containing E3 ubiquitin protein ligase 2], which then ubiquitinates LKB1 in the nuclear compartment of endothelial cells. Site-directed mutagenesis revealed that acetylation at lysine (K) 64 of LKB1 triggers the formation of SIRT1/HERC2/LKB1 protein complex and subsequent proteasomal degradation. In vitro cellular studies suggested that accumulation of acetylated LKB1 in the nucleus leads to endothelial activation, in turn stimulating the proliferation of vascular smooth muscle cells and the production of extracellular matrix proteins. Chromatin immunoprecipitation quantitative PCR confirmed that acetylated LKB1 interacts with and activates TGFβ1 promoter, which is inhibited by SIRT1. Knocking down either SIRT1 or HERC2 results in an increased association of LKB1 with the positive regulatory elements of TGFβ1 promoter. In mice without endothelial nitric oxide synthase, selective overexpression of human SIRT1 in endothelium prevents hypertension and age-related adverse arterial remodeling. Lentiviral-mediated knockdown of HERC2 abolishes the beneficial effects of endothelial SIRT1 on both arterial remodeling and arterial blood pressure control.

Conclusion-By downregulating acetylated LKB1 protein via HERC2, SIRT1 fine-tunes the crosstalk between endothelial and vascular smooth muscle cells to prevent adverse arterial remodeling and maintain vascular homeostasis.

miR-34a is a common link in both HIV- and antiretroviral therapy-induced vascular aging

Both HIV and antiretroviral therapy could induce vascular aging with unclear mechanisms. In this study, via microarray analysis, we identified, for the first time, that miR-34a expression was significantly increased in both HIV-infected, and antiretroviral agents-treated vessels and vascular endothelial cells (ECs) from these vessels. In cultured ECs, miR-34a expression was significantly increased by HIV-Tat protein and by the antiretroviral agents, lopinavir/ritonavir. Both HIV-Tat protein and antiretroviral agents could induce EC senescence, which was inhibited by miR-34a inhibition. In contrast, EC senescence was exacerbated by miR-34a overexpression. In addition, the vascular ECs isolated from miR-34a knockout mice were resistant to HIV and antiretroviral agents-mediated senescence. In vivo, miR-34a expression in mouse vascular walls and their ECs was increased by antiretroviral therapy and by HIV-1 Tat transgenic approach. miR-34a inhibition could effectively inhibit both HIV-Tat protein and antiretroviral therapy-induced vascular aging in mice. The increased miR-34a was induced via p53, whereas Sirt1 was a downstream target gene of miR-34a in both HIV-Tat protein and antiretroviral agents-treated ECs and vessels. The study has demonstrated that miR-34a is a common link in both HIV and antiretroviral therapy-mediated vascular aging.

MicroRNA Profiling Reveals Distinct Profiles for Tissue-Derived and Cultured Endothelial Cells

Endothelial plasticity enables the cells to switch their phenotype according to the surrounding vascular microenvironment. MicroRNAs (miRNAs) are small noncoding RNAs that control endothelial plasticity. The objective of this study was to investigate the differences in miRNA profiles of tissue-derived cells and cultured endothelial cells. To this end, miRNA expression was profiled from freshly isolated tissue-derived human vascular endothelial cells and endothelial cells cultured until cellular senescence using miRNA sequencing. In addition, the data was searched for putative novel endothelial miRNAs and miRNA isoforms. The data analysis revealed a striking change in endothelial miRNA profile as the cells adapted from tissue to cell culture environment and the overall miRNA expression decreased significantly in cultured compared to tissue-derived endothelial cells. In addition to changes in mechanosensitive miRNA expression, alterations in senescence-associated and endothelial-to-mesenchymal-transition-associated miRNAs were observed in aging cells. Collectively, the data illustrates the adaptability of endothelial cell miRNA expression that mirrors prevailing cellular environment.

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.

SIRT1/Atg5/autophagy are involved in the antiatherosclerosis effects of ursolic acid

The purpose of this study was to investigate the antiatherosclerosis effects of ursolic acid (UA) in high-fat diet-fed quails (Coturnix coturnix) and potential mechanism. Quails were treated with high-fat diet (14 % pork oil, 1 % cholesterol w/w) with or without UA (50, 150, or 300 mg/kg/day) for 10 weeks. Serum lipid profile was assessed at 0, 4.5, and 10 weeks. After 10 weeks, serum antioxidant status and morphology of aorta were assessed. Additionally, human umbilical vein endothelial cells (HUVECs) were exposed to 100 μg/ml oxidized low-density lipoprotein (ox-LDL) for 24 h, with or without pretreatment with UA (5, 10 or 20 μM) for 16 h, autophagy inhibitor 3-MA 5 mM for 2 h, or SIRT1 inhibitor EX-527 10 μM for 2 h. Cell viability and oxidative stress status were assessed and autophagy status was determined. Acetylation of lysine residue on Atg5 was assessed with immunoprecipitation. In results, high-fat diet negatively affected serum lipid profile and antioxidant status in quails and induced significant histological changes. Cotreatment with UA remarkably alleviated such changes. In HUVECs, ox-LDL treatment induced significant cytotoxicity along with oxidative stress, while UA cotreatment alleviated such changes significantly. UA treatment induced autophagy, enhanced SIRT1 expression, and decreased acetylation of lysine residue on Atg5. Cotreatment with 3-MA or EX-527 effectively abolished UA's protective effects. In summary, UA exerted antiatherosclerosis effects in quails and protected HUVECs from ox-LDL induced cytotoxicity, and the mechanism is associated with increased SIRT1 expression, decreased Atg5 acetylation on lysine residue, and increased autophagy.

At the interface of antioxidant signalling and cellular function: Key polyphenol effects

The hypothesis that dietary (poly)phenols promote well‐being by improving chronic disease‐risk biomarkers, such as endothelial dysfunction, chronic inflammation and plasma uric acid, is the subject of intense current research, involving human interventions studies, animal models and in vitro mechanistic work. The original claim that benefits were due to the direct antioxidant properties of (poly)phenols has been mostly superseded by detailed mechanistic studies on specific molecular targets. Nevertheless, many proposed mechanisms in vivo and in vitro are due to modulation of oxidative processes, often involving binding to specific proteins and effects on cell signalling. We review the molecular mechanisms for 3 actions of (poly)phenols on oxidative processes where there is evidence in vivo from human intervention or animal studies. (1) Effects of (poly) phenols on pathways of chronic inflammation leading to prevention of some of the damaging effects associated with the metabolic syndrome. (2) Interaction of (poly)phenols with endothelial cells and smooth muscle cells, leading to effects on blood pressure and endothelial dysfunction, and consequent reduction in cardiovascular disease risk. (3) The inhibition of xanthine oxidoreductase leading to modulation of intracellular superoxide and plasma uric acid, a risk factor for developing type 2 diabetes.