Age‐associated downregulation of vasohibin‐1 in vascular endothelial cells

Vasohibin‐1 (VASH1) is an angiogenesis‐inhibiting factor synthesized by endothelial cells (ECs) and it also functions to increase stress tolerance of ECs, which function is critical for the maintenance of vascular integrity. Here, we examined whether the expression of VASH1 would be affected by aging. We passaged human umbilical vein endothelial cells (HUVECs) and observed that VASH1 was downregulated in old HUVECs. This decrease in VASH1 expression with aging was confirmed in mice. To explore the mechanism of this downregulation, we compared the expression of microRNAs between old and young HUVECs by performing microarray analysis. Among the top 20 microRNAs that were expressed at a higher level in old HUVECs, the third highest microRNA, namely miR‐22‐3p, had its binding site on the 3′ UTR of VASH1 mRNA. Experiments with microRNA mimic and anti‐miR revealed that miR‐22‐3p was involved at least in part in the downregulation of VASH1 in ECs during replicative senescence. We then clarified the significance of this defective expression of VASH1 in the vasculature. When a cuff was placed around the femoral arteries of wild‐type mice and VASH1‐null mice, neointimal formation was augmented in the VASH1‐null mice accompanied by an increase in adventitial angiogenesis, macrophage accumulation in the adventitia, and medial/neointimal proliferating cells. These results indicate that in replicative senescence, the downregulation of VASH1 expression in ECs was caused, at least in part, by the alteration of microRNA expression. Such downregulation of VASH1 might be involved in the acceleration of age‐associated vascular diseases.     

H2O2 down-regulates SIRT7’s protective role of endothelial premature dysfunction via microRNA-335-5p

Endothelial senescence is believed to constitute the initial pathogenesis of the atherosclerotic cardiovascular disease (ASCVD). MicroRNA-335-5p (miR-335-5p) expression is significantly up-regulated in oxidative stress-induced endothelial cells (ECs). Sirtuin7 (SIRT7) is considered to prevent EC senescence, yet data on its response to ASCVD risk factors are limited. The present study analyzed the elevated levels of miR-335-5p and the decreased levels of SIRT7 in human umbilical vein endothelial cells (HUVECs), and found that high glucose, tumor necrosis factor-α (TNF-α), and H₂O₂ are the three contributing factors that induced cellular senescence. The current study also assessed premature endothelial senescence and decreased proliferation, adhesion, migration, and nitric oxide (NO) secretion in HUVECs with these risk factors together with SIRT7–siRNA transfection. It found that the miR-335-5p inhibitor attenuated the down-regulation of SIRT7 expression induced by oxidative stress in HUVECs, and SIRT7 overexpression exerts a rescue effect against miR-335-5p-induced endothelial dysfunction. Furthermore, the direct binding of miR-335-5p to SIRT7 was observed in human embryonic kidney cells 293T (HEK 293T). Therefore, it can be inferred that miR-335-5p down-regulates the expression of SIRT7 in human cells. Current findings may provide deeper insights into the underlying mechanisms of endothelial senescence and potential therapeutic targets of ASCVD as well as other age-related diseases.     

Is vasohibin-1 for more than angiogenesis inhibition?

Angiogenesis, a formation of neo-vessels from pre-existing ones, is regulated by the local balance between its stimulators and inhibitors. Vasohibin-1 (VASH1) was originally identified as an endothelium-derived vascular endothelial growth factor (VEGF)-inducible angiogenesis inhibitor that acts in a negative feedback manner. The expression of VASH1 has been shown in endothelial cells (ECs) in both physiological and pathological conditions associated with angiogenesis. However, recent reports indicate that VASH1 is expressed not only in ECs but also in other cell types including haematopoietic cells. The function of VASH1 may not be restricted to angiogenesis inhibition.     

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

The natural polyphenolic compound resveratrol (3,4,5-trihydroxy-trans-stilbene) has broad spectrum health beneficial activities including antioxidant, anti-inflammatory, anti-aging, anti-cancer, cardioprotective, and neuroprotective effects. Remarkably, resveratrol also induces apoptosis and cellular senescence in primary and cancer cells. Resveratrol’s anti-aging effects both in vitro and in vivo attributed to activation of a (NAD)-dependent histone deacetylase family member sirtuin-1 (SIRT1) protein. In mammals seven members (SIRT1-7) of sirtuin family have been identified. Among those, SIRT1 is the most extensively studied with perceptive effects on mammalian physiology and suppression of the diseases of aging. Yet no data has specified the role of sirtuins, under conditions where resveratrol treatment induces senescence. Current study was undertaken to investigate the effects of resveratrol in human primary dermal fibroblasts (BJ) and to clarify the role of sirtuin family members in particular SIRT1 and SIRT2 that are known to be involved in cellular stress responses and cell cycle, respectively. Here, we show that resveratrol decreases proliferation of BJ cells in a time and dose dependent manner. In addition the increase in senescence associated β-galactosidase (SA-β-gal) activity and methylated H3K9-me indicate the induction of premature senescence. A significant increase in phosphorylation of γ-H2AX, a surrogate of DNA double strand breaks, as well as in levels of p53, p21^CIP1 and p16^INK4A is also detected. Interestingly, at concentrations where resveratrol induced premature senescence we show a significant decrease in SIRT1 and SIRT2 levels by Western Blot and quantitative RT-PCR analysis. Conversely inhibition of SIRT1 and SIRT2 via siRNA or sirtinol treatment also induced senescence in BJ fibroblasts associated with increased SA-β-gal activity, γ-H2AX phosphorylation and p53, p21^CIP1 and p16^INK4A levels. Interestingly DNA damaging agent doxorubicin also induced senescence in BJ fibroblasts associated with decreased SIRT1/2 levels. In conclusion our data reveal that resveratrol induced premature senescence is associated with SIRT1 and SIRT2 down regulation in human dermal fibroblasts. Here we suggest that the concomitant decline in SIRT1/2 expression in response to resveratrol treatment may be a cause for induction of senescence, which is most likely mediated by a regulatory mechanism activated by DNA damage response.     

VEZF1–guanine quadruplex DNA interaction regulates alternative polyadenylation and detyrosinase activity of VASH1

Vascular endothelial zinc finger 1 (VEZF1) plays important roles in endothelial lineage definition and angiogenesis. Vasohibins 1 and 2 (VASH1 and VASH2) can form heterodimers with small vasohibin-binding protein (SVBP) and were recently shown to regulate angiogenesis by acting as tubulin detyrosinases. Here, we showed that VEZF1 binds directly with DNA guanine quadruplex (G quadruplex, G4) structures in vitro and in cells, which modulates the levels of the two isoforms of VASH1 mRNA. Disruption of this interaction, through genetic depletion of VEZF1 or treatment of cells with G4-stabilizing small molecules, led to increased production of the long over short isoform of VASH1 (i.e. VASH1A and VASH1B, respectively) mRNA and elevated tubulin detyrosinase activity in cells. Moreover, disruption of VEZF1-G4 interactions in human umbilical vein endothelial cells resulted in diminished angiogenesis. These results suggest that the interaction between VEZF1 and G4 structures assumes a crucial role in angiogenesis, which occurs through regulating the relative levels of the two isoforms of VASH1 mRNA and the detyrosinase activity of the VASH1-SVBP complex. Together, our work revealed VEZF1 as a G4-binding protein, identified a novel regulatory mechanism for tubulin detyrosinase, and illustrated that the VEZF1- and VASH1-mediated angiogenesis pathways are functionally connected.     

High Glucose Induced Alteration of SIRTs in Endothelial Cells Causes Rapid Aging in a p300 and FOXO Regulated Pathway

In diabetes, some of the cellular changes are similar to aging. We hypothesized that hyperglycemia accelerates aging-like changes in the endothelial cells (ECs) and tissues leading to structural and functional damage. We investigated glucose-induced aging in 3 types of ECs using senescence associated β-gal (SA β-gal) staining and cell morphology. Alterations of sirtuins (SIRTs) and their downstream mediator FOXO and oxidative stress were investigated. Relationship of such alteration with histone acetylase (HAT) p300 was examined. Similar examinations were performed in tissues of diabetic animals. ECs in high glucose (HG) showed evidence of early senescence as demonstrated by increased SA β-gal positivity and reduced replicative capacities. These alterations were pronounced in microvascular ECs. They developed an irregular and hypertrophic phenotype. Such changes were associated with decreased SIRT (1–7) mRNA expressions. We also found that p300 and SIRT1 regulate each other in such process, as silencing one led to increase of the others’ expression. Furthermore, HG caused reduction in FOXO1’s DNA binding ability and antioxidant target gene expressions. Chemically induced increased SIRT1 activity and p300 knockdown corrected these abnormalities slowing aging-like changes. Diabetic animals showed increased cellular senescence in renal glomerulus and retinal blood vessels along with reduced SIRT1 mRNA expressions in these tissues. Data from this study demonstrated that hyperglycemia accelerates aging-like process in the vascular ECs and such process is mediated via downregulation of SIRT1, causing reduction of mitochondrial antioxidant enzyme in a p300 and FOXO1 mediated pathway.     

CYP2E1-mediated oxidative stress regulates HO-1 and GST expression in maneb- and paraquat-treated rat polymorphonuclear leukocytes

Cytochrome P4502E1 (CYP2E1), glutathione-S-transferase A4-4 (GSTA4-4), and inducible nitric oxide synthase (iNOS) are implicated in maneb- and paraquat-induced toxicity leading to various pathological conditions. The study aimed to investigate the role of CYP2E1 in maneb- and paraquat-induced oxidative stress in rat polymorphonuclear leukocytes (PMNs) and its crosstalk with iNOS-mediated nitrosative stress and GSTA4-4-linked protective effect, if any and their consequent links with the nuclear factor erythoid 2-related factor 2 (Nrf2) activation and heme oxygenase-1 (HO-1) expression. Rats were treated with/without maneb and/or paraquat for 1, 2, and 3 weeks along with vehicle controls. Subsets of rats were also treated with diallyl sulfide (DAS) or aminoguanidine (AG) along with the respective controls. Maneb and paraquat augmented the reactive oxygen species (ROS), lipid peroxidation (LPO) and 4-hydroxy nonenal (4-HNE) contents, and superoxide dismutase (SOD) activity in the PMNs. However, maneb and paraquat attenuated the reduced glutathione (GSH) level and the expression/activity of total GST and GST-pi. Maneb and paraquat increased the expression/activity of CYP2E1, GSTA4-4, iNOS, Nrf2 and HO-1, and nitrite content. CYP2E1 inhibitor, DAS noticeably alleviated maneb- and paraquat-induced ROS, LPO, 4-HNE, SOD, Nrf2 and HO-1, GST, GSH, and GST-pi while iNOS, nitrite content and GSTA4-4 levels were unchanged. Conversely, AG, an iNOS inhibitor, attenuated maneb- and paraquat-directed changes in nitrite, LPO, iNOS but it did not alter ROS, GSH, SOD, GST, GST-pi, Nrf2, HO-1, CYP2E1, and GSTA4-4. The results demonstrate that CYP2E1 induces iNOS-independent free radical generation and subsequently modulates the Nrf2-dependent HO-1 and 4-HNE-mediated GST expression in maneb- and paraquat-treated PMNs.     

Sirtuin 1 ameliorates defenestration in hepatic sinusoidal endothelial cells during liver fibrosis via inhibiting stress‐induced premature senescence

ObjectivePremature senescence is related to progerin and involves in endothelial dysfunction and liver diseases. Activating sirtuin 1 (SIRT1) ameliorates liver fibrosis. However, the mechanisms of premature senescence in defenestration of hepatic sinusoidal endothelial cells (HSECs) and how SIRT1 affects HSECs fenestrae remain elusive.MethodsWe employed the CCl₄‐induced liver fibrogenesis rat models and cultured primary HSECs in vitro, administered with the SIRT1‐adenovirus vector, the activator of SIRT1 and knockdown NOX2. We measured the activity of senescence‐associated β‐galactosidase (SA‐β‐gal) in HSECs. Meanwhile, the protein expression of SIRT1, NOX2, progerin, Lamin A/C, Ac p53 K381 and total p53 was detected by Western blot, co‐immunoprecipitation and immunofluorescence.ResultsIn vivo, premature senescence was triggered by oxidative stress during CCl₄‐induced HSECs defenestration and liver fibrogenesis, whereas overexpressing SIRT1 with adenovirus vector lessened premature senescence to relieve CCl₄‐induced HSECs defenestration and liver fibrosis. In vitro, HSECs fenestrae disappeared, with emerging progerin‐associated premature senescence; these effects were aggravated by H₂O₂. Nevertheless, knockdown of NOX2, activation of SIRT1 with resveratrol and SIRT1‐adenovirus vector inhibited progerin‐associated premature senescence to maintain fenestrae through deacetylating p53. Furthermore, more Ac p53 K381 and progerin co‐localized with the abnormal accumulation of actin filament (F‐actin) in the nuclear envelope of H₂O₂‐treated HSECs; in contrast, these effects were rescued by overexpressing SIRT1.ConclusionSIRT1‐mediated deacetylation maintains HSECs fenestrae and attenuates liver fibrogenesis through inhibiting oxidative stress‐induced premature senescence.     

Fabrication of plumbagin on silver nanoframework for tunable redox modulation: Implications for therapeutic angiogenesis

The redox state of the endothelial cells plays a key role in the regulation of the angiogenic process. The modulation of the redox state of endothelial cells (ECs) could be a viable target to alter angiogenic response. In the present work, we synthesized a redox modulator by caging 5-hydroxy 2-methyl 1, 4-napthoquinone (Plumbagin) on silver nano framework (PCSN) for tunable reactive oxygen species (ROS) inductive property and tested its role in ECs during angiogenic response in physiological and stimulated conditions. In physiological conditions, the redox modulators induced the angiogenic response by establishing ECs cell–cell contact in tube formation model, chorio allontoic membrane, and aortic ring model. The molecular mechanism of angiogenic response was induced by vascular endothelial growth factor receptor 2 (VEGFR2)/p42-mitogen-activated protein kinase signaling pathway. Under stimulation, by mimicking tumor angiogenic conditions it induced cytotoxicity by generation of excessive ROS and inhibited the angiogenic response by the loss of spatiotemporal regulation of matrix metalloproteases, which prevents the tubular network formation in ECs and poly-ADP ribose modification of VEGF. The mechanism of opposing effects of PCSN was due to modulation of PKM2 enzyme activity, which increased the EC sensitivity to ROS and inhibited EC survival in stimulated condition. In normal conditions, the endogenous reactive states of NOX4 enzyme helped the EC survival. The results indicated that a threshold ROS level exists in ECs that promote angiogenesis and any significant enhancement in its level by redox modulator inhibits angiogenesis. The study provides the cues for the development of redox-based therapeutic molecules to cure the disease-associated aberrant angiogenesis.     

Superoxide dismutase 1 knock-down induces senescence in human fibroblasts

Reactive oxygen species (ROS) such as superoxide radicals are responsible for the pathogenesis of various human diseases. ROS are generated during normal metabolic process in all of the oxygen-utilizing organisms. The copper-zinc-containing SOD (SOD1) acts as a major defense against ROS by detoxifying the superoxide anion. In model organisms, SOD1 has been shown to play a role in the aging process. However, the exact role of the SOD1 protein in the human aging process remains to be resolved. We show that SOD1 RNA interference (RNAi) induces senescence in normal human fibroblasts. This premature senescence depends on p53 induction. In contrast, in human fibroblastic cells with inactivated p53, the SOD1 RNAi is without effect. Surprisingly, in cancer cells (HeLa), the SOD1 RNAi induces cell death rather then senescence. Together, these findings support the notion that in normal human cells the SOD1 protein may play a role in the regulation of cellular lifespan by p53 and may also regulate the death signals in cancer cells.     

Resveratrol attenuates apoptosis of pulmonary microvascular endothelial cells induced by high shear stress and proinflammatory factors

Endothelial injury usually underlies the initial pathologic step of cardiovascular diseases. Primary endothelial cell (EC) apoptosis and secondary hyperproliferation both contribute to the development of atherosclerosis and luminal occlusion. In order to investigate the effects of resveratrol (RSV) on EC apoptosis, we applied high shear stress (HSS) with proinflammatory factors [tumor necrosis factor alpha (TNF-α) plus cycloheximide] to human pulmonary microvascular ECs (PMVECs) through an artificial capillary system. Intracellular reactive oxygen species (ROS) was measured by spectrofluorometry using dihydrorhodamine 123 fluorescent probe. Apoptosis and proliferation was determined by flow cytometric analysis. Protein expression was examined by Western blot. HSS plus inflammation significantly raised the ROS and the apoptosis level of PMVECs, which could be diminished by RSV pretreatment. In a 7-days incubation assay, RSV effectively inhibited the initial increase in apoptosis and thereby prevented subsequent PMVEC hyperproliferation induced by HSS plus inflammation. Mercaptosuccinate, a glutathione peroxidase (GPx-1) inhibitor or nicotinamide, a silent information regulator 2/sirtuin 1 (SIRT1) inhibitor could attenuate the antiapoptotic action of RSV on PMVECs; and RSV treatment upregulated GPx-1 and SIRT1 expression in PMVECs. In conclusion, RSV, probably by activating SIRT1 signaling pathway, inhibits the oxidative-stress-dependent phenotypical shift of ECs induced by HSS and proinflammatory factors in vitro.     

Association of SIRT1 expression with shear stress induced endothelial progenitor cell differentiation

Shear stress imposed by blood flow is crucial for differentiation of endothelial progenitor cells (EPCs). Histone deacetylase SIRT1 has been shown to play a pivotal role in many physiological processes. However, association of SIRT1 expression with shear stress‐induced EPC differentiation remains to be elucidated. The present study was designed to determine the effect of SIRT1 on EPC differentiation induced by shear stress, and to seek the underlying mechanisms. Human umbilical cord blood‐derived EPCs were exposed to laminar shear stress of 15 dyn/cm² by parallel plate flow chamber system. Shear stress enhanced EPC differentiation toward endothelial cells (ECs) while inhibited to smooth muscle cells (SMCs). The expressions of phospho‐Akt, SIRT1 and histone H3 acetylation (Ac‐H3) in EPCs were detected after exposure to shear stress for 2, 6, 12, and 24 h, respectively. Shear stress significantly activated Akt phosphorylation, augmented SIRT1 expression and downregulated Ac‐H3. SIRT1 siRNA in EPCs diminished the expression of EC markers, but increased the expression of SMC markers, and resulted in upregulation of Ac‐H3. Whereas, resveratrol, an activator of SIRT1, had the opposite effects on both EPC differentiation and histone H3 acetylation. Wortmannin, an inhibitor of PI3‐kinase, suppressed endothelial differentiation of EPCs, decreased SIRT1, and upregulated Ac‐H3 expression. In addition, SIRT1 promoted tube formation of EPCs in matrix gels. These results provided a mechanobiological basis of shear stress‐induced EPC differentiation into ECs and suggest that PI3k/Akt‐SIRT1‐Ac‐H3 pathway is crucial in such a process. J. Cell. Biochem. 113: 3663–3671, 2012. © 2012 Wiley Periodicals, Inc.     

Advanced Maternal Age‐associated SIRT1 Deficiency Compromises Trophoblast Epithelial−Mesenchymal Transition through an Increase in Vimentin Acetylation

Advanced maternal age (AMA) pregnancies are rapidly increasing and are associated with aberrant trophoblast cell function, poor placentation, and unfavorable pregnancy outcomes, presumably due to premature placental senescence. SIRT1 is an NAD⁺‐dependent deacetylase with well‐known antiaging effects, but its connection with placental senescence is unreported. In this study, human term placentas and first‐trimester villi were collected from AMA and normal pregnancies, and a mouse AMA model was established by cross breeding young and aged male and female C57 mice. SIRT1 expression and activity in HTR8/SVneo cells were genetically or pharmacologically manipulated. Trophoblast‐specific Sirt1‐knockout (KO) mouse placentas were generated by mating Elf5‐Cre and Sirt1 ^fl/fl mice. Trophoblast cell mobility was assessed with transwell invasion and wound‐healing assays. SIRT1‐binding proteins in HTR8/SVneo cells and human placental tissue were identified by mass spectrometry. We identified SIRT1 as the only differentially expressed sirtuin between AMA and normal placentas. It is downregulated in AMA placentas early in the placental life cycle and is barely impacted by paternal age. SIRT1 loss upregulates P53 acetylation and P21 expression and impairs trophoblast invasion and migration. Sirt1‐KO mouse placentas exhibit senescence markers and morphological disruption, along with decreased fetal weight. In trophoblasts, SIRT1 interacts with vimentin, regulating its acetylation. In conclusion, SIRT1 promotes trophoblast epithelial−mesenchymal transition (EMT) to enhance invasiveness by modulating vimentin acetylation. AMA placentas are associated with premature senescence during placentation due to SIRT1 loss. Therefore, SIRT1 may be an antiaging therapeutic target for improving placental development and perinatal outcomes in AMA pregnancies.     

Ganglioside GM1 Contributes to the State of Insulin Resistance in Senescent Human Arterial Endothelial Cells

Vascular endothelial cells (ECs) play central roles in physiologically important functions of blood vessels and contribute to the maintenance of vascular integrity. Therefore, it is considered that the impairment of EC functions leads to the development of vascular diseases. However, the molecular mechanisms of the EC dysfunctions that accompany senescence and aging have not yet been clarified. The carbohydrate antigens carried by glycoconjugates (e.g. glycoproteins, glycosphingolipids, and proteoglycans) mainly present on the cell surface serve not only as marker molecules but also as functional molecules. In this study, we have investigated the abundance and functional roles of glycosphingolipids in human ECs during senescence and aging. Among glycosphingolipids, ganglioside GM1 was highly expressed in abundance on the surface of replicatively and prematurely senescent ECs and also of ECs derived from an elderly subject. Insulin signaling, which regulates important functions of ECs, is impaired in senescent and aged ECs. Actually, by down-regulating GM1 on senescent ECs and overloading exogenous GM1 onto non-senescent ECs, we showed that an increased abundance of GM1 functionally contributes to the impairment of insulin signaling in ECs. Taken together, these findings provide the first evidence that GM1 increases in abundance on the cell surface of ECs under the conditions of cellular senescence and aging and causes insulin resistance in ECs. GM1 may be an attractive target for the detection, prevention, and therapy of insulin resistance and related vascular diseases, particularly in older people.     

MicroRNA-217 Promotes Angiogenesis of Human Cytomegalovirus-Infected Endothelial Cells through Downregulation of SIRT1 and FOXO3A

Human cytomegalovirus(HCMV) infection has been shown to contribute to vascular disease through the induction of angiogenesis. However, the role of microRNA in angiogenesis induced by HCMV infection remains unclear. The present study was thus designed to explore the potential effect of miR-1217 on angiogenesis and to disclose the underlying mechanism in endothelial cells. We found that HCMV infection of endothelial cells(ECs) enhanced expression of miR-217 and reduced SIRT1 and FOXO3A protein level in 24 hours post infection(hpi). Transfection of miR-217 inhibitor not only depressed cellular migration and tube formation induced by HCMV infection, but also enhanced SIRT1 and FOXO3A protein expression. Additionally, luciferase assay confirmed that miR-217 directly targeted FOXO3A mRNA 3`UTR. Furthermore, pretreatment with resveratrol depressed motility and tube formation of HCMV-infected ECs, which could be reversed by SIRT1 siRNA. Similarly, delivery of FOXO3A overexpression lentivirus suppressed proliferative rate, migration and tube formation of HCMV-infected ECs, which reversed by transfection of FOXO3A siRNA. In summary, HCMV infection of endothelial cells induces angiogenesis by both of miR-217/SIRT1 and miR-217/FOXO3A axis.     

Regulation of WRN protein cellular localization and enzymatic activities by SIRT1-mediated deacetylation

Werner syndrome is an autosomal recessive disorder associated with premature aging and cancer predisposition caused by mutations of the WRN gene. WRN is a member of the RecQ DNA helicase family with functions in maintaining genome stability. Sir2, an NAD-dependent histone deacetylase, has been proven to extend life span in yeast and Caenorhabditis elegans. Mammalian Sir2 (SIRT1) has also been found to regulate premature cellular senescence induced by the tumor suppressors PML and p53. SIRT1 plays an important role in cell survival promoted by calorie restriction. Here we show that SIRT1 interacts with WRN both in vitro and in vivo; this interaction is enhanced after DNA damage. WRN can be acetylated by acetyltransferase CBP/p300, and SIRT1 can deacetylate WRN both in vitro and in vivo. WRN acetylation decreases its helicase and exonuclease activities, and SIRT1 can reverse this effect. WRN acetylation alters its nuclear distribution. Down-regulation of SIRT1 reduces WRN translocation from nucleoplasm to nucleoli after DNA damage. These results suggest that SIRT1 regulates WRN-mediated cellular responses to DNA damage through deacetylation of WRN.     

Reactive oxygen species as mediators of angiogenesis signaling. Role of NAD(P)H oxidase

Angiogenesis, a process of new blood vessel growth, contributes to various pathophysiologies such as cancer, diabetic retinopathy and atherosclerosis. Accumulating evidence suggests that cardiovascular diseases are associated with increased oxidative stress in blood vessels. Reactive oxygen species (ROS) such as superoxide and H₂O₂ cause blood vessels to thicken, produce inflammation in the vessel wall, and thus are regarded as “risk factors” for vascular disease, whereas ROS also act as signaling molecules in many aspects of growth factor-mediated physiological responses. Recent reports suggest that ROS play an important role in angiogenesis; however, its underlying molecular mechanisms remain unknown. Vascular endothelial growth factor (VEGF) induces angiogenesis by stimulating endothelial cell (EC) proliferation and migration primarily through the receptor tyrosine kinase VEGF receptor2 (Flk1/KDR). VEGF binding initiates tyrosine phosphorylation of KDR, which results in activation of downstream signaling enzymes including ERK1/2, Akt and eNOS, which contribute to angiogenic-related responses in EC. Importantly, the major source of ROS in EC is a NAD(P)H oxidase and EC express all the components of phagocytic NAD(P)H oxidase including gp91phox, p22phox, p47phox, p67phox and the small G protein Rac1. We have recently demonstrated that ROS derived from NAD(P)H oxidase are critically important for VEGF signaling in vitro and angiogenesis in vivo. Furthermore, a peptide hormone, angiotensin II, a major stimulus for vascular NAD(P)H oxidase, also plays an important role in angiogenesis. Because EC migration and proliferation are primary features of the process of myocardial angiogenesis, we would like to focus on the recent progress that has been made in the emerging area of NAD(P)H oxidase-derived ROS-dependent signaling in ECs, and discuss the possible roles in angiogenesis. Understanding these mechanisms may provide insight into the components of NAD(P)H oxidase as potential therapeutic targets for treatment of angiogenesis-dependent diseases such as cancer and atherosclerosis and for promoting myocardial angiogenesis in ischemic heart diseases. (Mol Cell Biochem 264: 85–97, 2004)