Impaired cross-activation of β3 integrin and VEGFR-2 on endothelial progenitor cells with aging decreases angiogenesis in response to hypoxia

Paracrine-mediated rejuvenation of aged mesenchymal stem cells is associated with downregulation of the autophagy-lysosomal pathway

Age-related differences in stem-cell potency contribute to variable outcomes in clinical stem cell trials. To help understand the effect of age on stem cell potency, bone marrow-derived mesenchymal stem cells (MSCs) were isolated from young (6 weeks) and old (18–24 months) mice. HUVEC tubule formation (TF) induced by the old and young MSCs and ELISA of conditioned media were compared to one another, and to old MSCs after 7 d in indirect co-culture with young MSCs. Old MSCs induced less TF than did young (1.56 ± 0.11 vs 2.38 ± 0.17, p = 0.0003) and released lower amounts of VEGF (p = 0.009) and IGF1 (p = 0.037). After 7 d in co-culture with young MSCs, TF by the old MSCs significantly improved (to 2.09 ± 0.18 from 1.56 ± 0.11; p = 0.013), and was no longer different compared to TF from young MSCs (2.09 ± 0.18 vs 2.38 ± 0.17; p = 0.27). RNA seq of old MSCs, young MSCs, and old MSCs following co-culture with young MSCs revealed that the age-related differences were broadly modified by co-culture, with the most significant changes associated with lysosomal pathways. These results indicate that the age-associated decreased paracrine-mediated effects of old MSCs are improved following indirect co-culture with young MSC. The observed effect is associated with broad transcriptional modification, suggesting potential targets to both assess and improve the therapeutic potency of stem cells from older patients.

The role of integrins in inflammation and angiogenesis

Integrins are heterodimeric transmembrane cell adhesion molecules made up of alpha (α) and beta (β) subunits arranged in numerous dimeric pairings. These complexes have varying affinities to extracellular ligands. Integrins regulate cellular growth, proliferation, migration, signaling, and cytokine activation and release and thereby play important roles in cell proliferation and migration, apoptosis, tissue repair, as well as in all processes critical to inflammation, infection, and angiogenesis. This review presents current evidence from human and animal studies on integrin structure and molecular signaling, with particular emphasis on signal transduction in infants. We have included evidence from our own laboratory studies and from an extensive literature search in databases PubMed, EMBASE, Scopus, and the electronic archives of abstracts presented at the annual meetings of the Pediatric Academic Societies. To avoid bias in identification of existing studies, key words were short-listed prior to the actual search both from anecdotal experience and from PubMed's Medical Subject Heading (MeSH) thesaurus. IMPACT: Integrins are a family of ubiquitous αβ heterodimeric receptors that interact with numerous ligands in physiology and disease. Integrins play a key role in cell proliferation, tissue repair, inflammation, infection, and angiogenesis. This review summarizes current evidence from human and animal studies on integrin structure and molecular signaling and promising role in diseases of inflammation, infection, and angiogenesis in infants. This review shows that integrin receptors and ligands are novel therapeutic targets of clinical interest and hold promise as novel therapeutic targets in the management of several neonatal diseases.

miR-25-3p promotes endothelial cell angiogenesis in aging mice via TULA-2/SYK/VEGFR-2 downregulation

In aging, the regulation of angiogenesis is a dynamic and complex process. We aimed to identify and characterize microRNAs that regulate angiogenesis during aging. We showed that, in response to vascular endothelial senescence, microRNA-25-3p (miR-25-3p) plays the role of an angiogenic microRNA by targeting TULA-2 (T-cell ubiquitin ligand-2)/SYK (spleen tyrosine kinase)/VEGFR-2 (vascular endothelial growth factor receptor 2) signaling in vitro and in vivo. Mechanistic studies demonstrated that miR-25-3p inhibits a TULA-2/SYK/VEGFR-2 signaling pathway in endothelial cells. In old endothelial cells (OECs), upregulation of miR-25-3p inhibited the expression of TULA-2, which caused downregulation of the interaction between TULA-2 and SYK and increased phosphorylation of SYK Y323. The increased SYK Y323 phosphorylation level upregulated the phosphorylation of VEGFR-2 Y1175, which plays a vital role in angiogenesis, while miR-25-3p downregulation in YECs showed opposite effects. Finally, a salvage study showed that miR-25-3p upregulation promoted capillary regeneration and hindlimb blood flow recovery in aging mice with hindlimb ischemia. These findings suggest that miR-25-3p acts as an agonist of TULA-2/SYK/VEGFR-2 and mediates the endothelial cell angiogenesis response, which shows that the miR-25-3p/TULA-2 pathway may be potential therapeutic targets for angiogenesis during aging.

Cathepsin K Deficiency Impaired Ischemia-Induced Neovascularization in Aged Mice

Background

Aging is a major risk factor for cardiovascular disease. Cysteine protease cathepsin K (CatK) has been implicated in the process of angiogenesis, but the exact roles of individual CatK in vessel formation during aging are poorly understood.

Methods and Results

To study the putative role of CatK in ischemia-induced angiogenesis, we applied a hindlimb ischemia model to aged wild-type (CatK^+/+) and CatK-deficient (CatK^−/−) mice. A serial laser Doppler blood-flow analysis revealed that the recovery of the ischemic/normal blood-flow ratio in the aged CatK^−/−mice was impaired throughout the follow-up period. On postoperative day 14, CatK deficiency had also impaired capillary formation. CatK deficiency reduced the levels of cleaved Notch1, phospho-Akt, and/or vascular endothelial growth factor (VEGF) proteins in the ischemic muscles and bone marrow-derived c-Kit⁺ cells. A flow cytometry analysis revealed that CatK deficiency reduced the numbers of endothelial progenitor cell (EPC)-like CD31⁺/c-Kit⁺ cells in the peripheral blood as well as the ischemic vasculature. In vitro experiments, CatK^−/− impaired bone-derived c-Kit⁺ cellular functions (migration, invasion, proliferation, and tubulogenesis) in aged mice. Our findings demonstrated that aging impaired the ischemia-induced angiogenesis associated with the reductions of the production and mobilization of CD31⁺/c-Kit⁺ cells in mice.

Conclusions

These findings established that the impairment of ischemia-induced neovascularization in aged CatK^−/− mice is due, at least in part, to the reduction of EPC mobilization and the homing of the cells into vasculature that is associated with the impairment of Notch1 signaling activation at advanced ages.

Cathepsin S-Mediated Negative Regulation of Wnt5a/SC35 Activation Contributes to Ischemia-Induced Neovascularization in Aged Mice

BACKGROUND

Given that cathepsin S (CatS) gained attention due to its enzymatic and non-enzymatic functions in signaling, the role of CatS in ischemia-induced angiogenesis of aged mice was explored.

METHODS AND RESULTS

To study the role of CatS in the decline in aging-related vascular regeneration capacity, a hindlimb ischemia model was applied to aged wild-type (CatS+/+) and CatS-deficient (CatS-/-) mice. CatS-/-mice exhibited impaired blood flow recovery and capillary formation and increased levels of p-insulin receptor substrate-1, Wnt5a, and SC35 proteins and decreased levels of phospho-endothelial nitric oxide synthase (p-eNOS), p-mTOR, p-Akt, p-ERK1/2, p-glycogen synthase kinase-3α/β, and galatin-3 proteins, as well as decreased macrophage infiltration and matrix metalloproteinase-2/-9 activities in the ischemic muscles. In vitro, CatS knockdown altered the levels of these targeted essential molecules for angiogenesis. Together, the results suggested that CatS-/-leads to defective endothelial cell functions and that CatS-/-is associated with decreased circulating endothelial progenitor cell (EPC)-like CD31+/c-Kit+cells. This notion was reinforced by the study finding that pharmacological CatS inhibition led to a declined angiogenic capacity accompanied by increased Wnt5a and SC35 levels and decreased eNOS/Akt-ERK1/2 signaling in response to ischemia.

CONCLUSIONS

These findings demonstrated that the impairment of ischemia-induced neovascularization in aged CatS-/-mice is due, at least in part, to the attenuation of endothelial cell/EPC functions and/or mobilization associated with Wnt5a/SC35 activation in advanced age.

Reduced NRF2 expression suppresses endothelial progenitor cell function and induces senescence during aging

Aging is associated with an increased risk of cardiovascular disease. Numerical and functional declines in endothelial progenitor cells (EPCs) limit their capacity for endothelial repair and promote the development of cardiovascular disease. We explored the effects of nuclear factor (erythroid-derived 2)-like 2 (NRF2) on EPC activity during aging. Both in vitro and in vivo, the biological functioning of EPCs decreased with aging. The expression of NRF2 and its target genes (Ho-1, Nqo-1 and Trx) also declined with aging, while Nod-like receptor protein 3 (NLRP3) expression increased. Aging was associated with oxidative stress, as evidenced by increased reactive oxygen species and malondialdehyde levels and reduced superoxide dismutase activity. Nrf2 silencing impaired the functioning of EPCs and induced oxidative stress in EPCs from young mice. On the other hand, NRF2 activation in EPCs from aged mice protected these cells against oxidative stress, ameliorated their biological dysfunction and downregulated the NLRP3 inflammasome. These findings suggest NRF2 can prevent the functional damage of EPCs and downregulate the NLRP3 inflammasome through NF-κB signaling.

Receptor tyrosine kinase inhibitor Sunitinib and integrin antagonist peptide HM-3 show similar lipid raft dependent biphasic regulation of tumor angiogenesis and metastasis

BACKGROUND

Anti-angiogenesis remains an attractive strategy for cancer therapy. Some anti-angiogenic reagents have bell-shape dose-response curves with higher than the effective doses yielding lower anti-angiogenic effects. In this study, two different types of anti-angiogenic reagents, a receptor tyrosine kinase inhibitor Sunitinib and an integrin antagonist peptide HM-3, were selected and their effects on tumor angiogenesis and metastasis were compared. The involved molecular mechanisms were investigated.

METHODS

The effect of high dose Sunitinib and HM-3 on tumor angiogenesis and metastasis was investigated with two animal models: metastasis of B16F10 cells in syngeneic mice and metastasis of human MDA-MB-231 cells in nude mice. Furthermore, mechanistic studies were performed with cell migration and invasion assays and with biochemical pull-down assays of intracellular RhoGTPases. Distribution of integrin αvβ3, α5β1, VEGFR2 and the complex of integrin αvβ3 and VEGFR2 inside or outside of lipid rafts was detected with lipid raft isolation and Western-blot analysis.

RESULTS

Both Sunitinib and HM-3 showed a bell-shape dose-response curve on tumor angiogenesis and metastasis in both animal models. The effects of Sunitinib and HM-3 on endothelial cell and tumor cell proliferation and migration were characterized. Activation of intracellular RhoGTPases and actin stress fiber formation in endothelial and cancer cells following Sunitinib and HM-3 treatment correlated with cell migration analysis. Mechanistic studies confirmed that HM-3 and Sunitinib regulated distribution of integrin αvβ3, α5β1, VEGFR2 and αvβ3-VEGFR2 complexes, both inside and outside of the lipid raft regions to regulate endothelial cell migration and intracellular RhoGTPase activities.

CONCLUSIONS

These data confirmed that a general non-linear dose-effect relationship for these anti-angiogenic drugs exists and their mechanisms are correlative. It also suggests that the effective dose of an anti-angiogenic drug may have to be strictly defined to achieve its optimal clinical effects.

Culture surfaces induce hypoxia-regulated genes in human mesenchymal stromal cells

Culturing human Mesenchymal stromal cells (hMSCs) in vitro in hypoxic conditions resulted in reduced senescence, enhanced pluripotency and altered proliferation rate. It has been known that in vitro hypoxia affects expression of cell surface proteins. However, the impact of culture surfaces on the hypoxia-regulated genes (HRG) have not yet been reported. This study utilized Next-Generation sequencing to analyse the changes in the gene expression levels of HRG for hMSCs cultured on different culture surfaces. The samples, which were cultured on four different synthesized surfaces (treatments) and tissue culture plate (control), resulted in a difference in growth rate. The sequencing results revealed that the transcription of a number of key genes involved in regulating hypoxic functions were significantly altered, including HIF2A, a marker for potency, differentiation, and various cellular functions. Significant alternations in the expression levels of previously reported oxygen-sensitive surface proteins were detected in this study, some of which closely correlate with the expression levels of HIF2A. Our analysis of the hMSCs transcriptome and HRG mapped out a list of genes encoding surface proteins which may directly regulate or be regulated by HIF2A. The findings from this study showed that culture surfaces have an impact on regulating the expression profile of HRG. Therefore, novel culture surfaces may be designed to selectively activate HIF2A and other HRG and pathways under in vitro normoxia. The understanding of the crosstalk between the regulating genes of hypoxia and culture surfaces may be utilized to strengthen desired hypoxic functions.

Metabolic Regulation of Angiogenesis in Diabetes and Aging

Impaired angiogenesis and endothelial dysfunction are hallmarks of diabetes and aging. Clinical efforts at promoting angiogenesis have largely focused on growth factor pathways, with mixed results. Recently, a new repertoire of endothelial intracellular molecules critical to endothelial metabolism has emerged as playing an important role in regulating angiogenesis. This review thus focuses on the emerging importance and therapeutic potential of these proteins and of endothelial bioenergetics in diabetes and aging.

The Chinese herbal formula Fuzheng Quxie Decoction attenuates cognitive impairment and protects cerebrovascular function in SAMP8 mice

PURPOSE

This study was designed to explore the underlying mechanism of action for a Fuzheng Quxie Decoction (FQD) in Alzheimer's disease (AD), to validate its neuroprotective effects, and to provide experimental support for its predicted mechanism of action.

METHODS

An integrative approach to network pharmacology was performed to predict the mechanism of action for treatment of AD with FQD. The predicted mechanism was validated in SAMP8 mice.

RESULTS

With predicted putative FQD targets and a collection of AD-related genes, 245 possible regulatory targets of FQD were identified for the treatment of AD. Pathway-enrichment analysis for the possible regulatory targets indicated that vascular endothelial growth factor (VEGF) and VEGF-receptor signaling were pivotal in the treatment of AD with FQD. In vivo experiments confirmed the neuroprotective effect and the predicted mechanism of action for treatment of AD with FQD.

CONCLUSION

This study contributes to an understanding of the neuroprotective effect of FQD and its potential mechanism of action for the treatment of AD.

Chronic Psychological Stress Accelerates Vascular Senescence and Impairs Ischemia-Induced Neovascularization: The Role of Dipeptidyl Peptidase-4/Glucagon-Like Peptide-1-Adiponectin Axis

BACKGROUND

Exposure to psychosocial stress is a risk factor for cardiovascular disease, including vascular aging and regeneration. Given that dipeptidyl peptidase-4 (DPP4) regulates several intracellular signaling pathways associated with the glucagon-like peptide-1 (GLP-1) metabolism, we investigated the role of DPP4/GLP-1 axis in vascular senescence and ischemia-induced neovascularization in mice under chronic stress, with a special focus on adiponectin -mediated peroxisome proliferator activated receptor-γ/its co-activator 1α (PGC-1α) activation.

METHODS AND RESULTS

Seven-week-old mice subjected to restraint stress for 4 weeks underwent ischemic surgery and were kept under immobilization stress conditions. Mice that underwent ischemic surgery alone served as controls. We demonstrated that stress impaired the recovery of the ischemic/normal blood-flow ratio throughout the follow-up period and capillary formation. On postoperative day 4, stressed mice showed the following: increased levels of plasma and ischemic muscle DPP4 and decreased levels of GLP-1 and adiponectin in plasma and phospho-AMP-activated protein kinase α (p-AMPKα), vascular endothelial growth factor, peroxisome proliferator activated receptor-γ, PGC-1α, and Sirt1 proteins and insulin receptor 1 and glucose transporter 4 genes in the ischemic tissues, vessels, and/or adipose tissues and numbers of circulating endothelial CD31+/c-Kit+ progenitor cells. Chronic stress accelerated aortic senescence and impaired aortic endothelial sprouting. DPP4 inhibition and GLP-1 receptor activation improved these changes; these benefits were abrogated by adiponectin blocking and genetic depletion.

CONCLUSIONS

These results indicate that the DPP4/GLP-1-adiponectin axis is a novel therapeutic target for the treatment of vascular aging and cardiovascular disease under chronic stress conditions.

Exercise restores muscle stem cell mobilization, regenerative capacity and muscle metabolic alterations via adiponectin/AdipoR1 activation in SAMP10 mice

BACKGROUND

Exercise train (ET) stimulates muscle response in pathological conditions, including aging. The molecular mechanisms by which exercise improves impaired adiponectin/adiponectin receptor 1 (AdipoR1)-related muscle actions associated with aging are poorly understood. Here we observed that in a senescence-accelerated mouse prone 10 (SAMP10) model, long-term ET modulated muscle-regenerative actions.

METHODS

25-week-old male SAMP10 mice were randomly assigned to the control and the ET (45 min/time, 3/week) groups for 4 months. Mice that were maintained in a sedentary condition served controls.

RESULTS

ET ameliorated aging-related muscle changes in microstructure, mitochondria, and performance. The amounts of proteins or mRNAs for p-AMPKα, p-Akt, p-ERK1/2, p-mTOR, Bcl-XL, p-FoxO3, peroxisome proliferators-activated receptor-γ coactivator, adiponectin receptor1 (adpoR1), and cytochrome c oxidase-IV, and the numbers of CD34⁺ /integrin-α₇⁺ muscle stem cells (MuSCs) and proliferating cells in the muscles and bone-marrow were enhanced by ET, whereas the levels of p-GSK-3α and gp91phox proteins and apoptotic cells were reduced by ET. The ET also resulted in increased levels of plasma adiponectin and the numbers of bone-marrow (BM)-derived circulating CD34⁺ /integrin-α₇⁺ MuSCs and their functions. Integrin-α₇⁺ MuSCs of exercised mice had improved changes of those beneficial molecules. These ET-mediated aged muscle benefits were diminished by adiponectin and AdipoR1 blocking as well as AMPK inhibition. Finally, recombinant mouse adiponectin enhanced AMPK and mTOR phosphorylations in BM-derived integrin-α₇⁺ cells.

CONCLUSIONS

These findings suggest that ET can improve aging-related impairments of BM-derived MuSC regenerative capacity and muscle metabolic alterations via an AMPK-dependent mechanism that is mediated by an adiponectin/AdipoR1 axis in SAMP10 mice.

Protective effect and mechanism of lycopene on endothelial progenitor cells (EPCs) from type 2 diabetes mellitus rats

Endothelial progenitor cells (EPCs), widely existing in bone marrow and peripheral blood, are involved in the repair of injured vascular endothelium and angiogenesis which are important to diabetic mellitus (DM) patients with vascular complications. The number and the function of EPCs are related to the advanced glycation end products (AGEs) generated in DM patients. Lycopene (Lyc) is an identified natural antioxidant that protects EPCs under the microenvironment of AGEs from damage. However, the underlying mechanism remains unclear. To investigate the effect of Lyc on EPCs, we isolated EPCs from DM rat bone marrow and determined cell proliferation, cell cycle,apoptosis and autophagy of EPCs. The present study showed that 10μg/mL Lyc improved cell proliferation and had low cytotoxicity in the presence of AGEs. In addition, Lyc rescued S phase of the cell cycle arrest, reduced apoptosis rate and decreased autophagic reaction including ROS and mitochondrial membrane potential (MMP) of EPCs. Moreover, Lyc combined use of autophagy inhibitors, 3-MA, had better protective effects. Taken together, our data suggests that Lyc promotes EPCs survival and protect EPCs from apoptosis and oxidative autophagy induced by AGEs, further remaining the number and function of EPCs. This study provides new insights into Lyc protective mechanism of AGEs-induced oxidative autophagy in EPCs from DM patients and offers a new therapy for DM vascular complications.

Enhanced VEGF signalling mediates cerebral neovascularisation via downregulation of guidance protein ROBO4 in a rat model of diabetes

AIMS/HYPOTHESIS

Diabetes promotes cerebral neovascularisation via increased vascular endothelial growth factor (VEGF) angiogenic signalling. Roundabout-4 (ROBO4) protein is an endogenous inhibitor of VEGF signalling that stabilises the vasculature. Yet, how diabetes affects ROBO4 function remains unknown. We hypothesised that increased VEGF signalling in diabetes decreases ROBO4 expression and function via binding of ROBO4 with VEGF-activated β3 integrin and that restoration of ROBO4 expression prevents/repairs cerebral neovascularisation in diabetes.

METHODS

ROBO4 protein expression in a rat model of type 2 diabetes (Goto-Kakizaki [GK] rats) was examined by western blotting and immunohistochemistry. ROBO4 was locally overexpressed in the brain and in primary brain microvascular endothelial cells (BMVECs). GK rats were treated with SKLB1002, a selective VEGF receptor-2 (VEGFR-2) antagonist. Cerebrovascular neovascularisation indices were determined using a FITC vascular space-filling model. Immunoprecipitation was used to determine ROBO4-β3 integrin interaction.

RESULTS

ROBO4 expression was significantly decreased in the cerebral vasculature as well as in BMVECs in diabetes (p < 0.05). Silencing Robo4 increased the angiogenic properties of control BMVECs (p < 0.05). In vivo and in vitro overexpression of ROBO4 inhibited VEGF-induced angiogenic signalling and increased vessel maturation. Inhibition of VEGF signalling using SKLB1002 increased ROBO4 expression (p < 0.05) and reduced neovascularisation indices (p < 0.05). Furthermore, SKLB1002 significantly decreased ROBO4-β3 integrin interaction in diabetes (p < 0.05).

CONCLUSIONS/INTERPRETATION

Our study identifies the restoration of ROBO4 and inhibition of VEGF signalling as treatment strategies for diabetes-induced cerebral neovascularisation.

The Role of Vascular Endothelial Growth Factor Receptor-1 Signaling in the Recovery from Ischemia

Vascular endothelial growth factor (VEGF) is one of the most potent angiogenesis stimulators. VEGF binds to VEGF receptor 1 (VEGFR1), inducing angiogenesis through the receptor's tyrosine kinase domain (TK), but the mechanism is not well understood. We investigated the role of VEGFR1 tyrosine kinase signaling in angiogenesis using the ischemic hind limb model. Relative to control mice, blood flow recovery was significantly impaired in mice treated with VEGFA-neutralizing antibody. VEGFR1 tyrosine kinase knockout mice (TK-/-) had delayed blood flow recovery from ischemia and impaired angiogenesis, and this phenotype was unaffected by treatment with a VEGFR2 inhibitor. Compared to wild type mice (WT), TK-/- mice had no change in the plasma level of VEGF, but the plasma levels of stromal-derived cell factor 1 (SDF-1) and stem cell factor, as well as the bone marrow (BM) level of pro-matrix metalloproteinase-9 (pro-MMP-9), were significantly reduced. The recruitment of cells expressing VEGFR1 and C-X-C chemokine receptor type 4 (CXCR4) into peripheral blood and ischemic muscles was also suppressed. Furthermore, WT transplanted with TK-/- BM significantly impaired blood flow recovery more than WT transplanted with WT BM. These results suggest that VEGFR1-TK signaling facilitates angiogenesis by recruiting CXCR4+VEGFR1+ cells from BM.

Glycation of vitronectin inhibits VEGF-induced angiogenesis by uncoupling VEGF receptor-2-αvβ3 integrin cross-talk

Glycation of vessel wall proteins is thought to have an important role in the pathogenesis of vascular complications in diabetes mellitus. However, no previous study has implicated glycated vitronectin (VN) in the control of vascular endothelial growth factor (VEGF) signaling. To explore whether the glycation of VN affects angiogenic signaling and to understand the molecular mechanisms involved, we synthesized glycated VN by incubating VN with methylglyoxal (MGO) in vitro and identified the formation of glycated VN by an LC–ESI–MS/MS-based method. We tested the hypothesis that glycation of VN downregulates VEGF receptor-2 (VEGFR-2) activation by uncoupling the interaction between VEGFR-2 and αvβ3. Unmodified and MGO-glycated VN were used as substrates for human umbilical vein endothelial cells (HUVECs). The effects of glycated VN on VEGF signaling in HUVECs were investigated. The glycation of VN inhibited VEGF-induced phosphorylation of VEGFR-2 and the intracellular signaling pathway downstream of VEGFR-2. Glycated VN inhibited the binding of VEGFR-2 to β3 integrin and inhibited the phosphorylation of β3 integrin. Furthermore, glycation of VN significantly decreased VEGF-induced migration of HUVECs in vitro and vessel outgrowth in an ex vivo angiogenesis model. Collectively, these data indicate that the glycation of VN inhibits VEGF-induced VEGFR-2 activation by uncoupling VEGFR-2–αvβ3 integrin cross-talk. The glycation of VN causes a reduction in the migration of endothelial cells and vessel outgrowth. This may provide a mechanism for the failure of collateral sprouting in diabetic microangiopathy.

Maternal anti-platelet β3 integrins impair angiogenesis and cause intracranial hemorrhage

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a life-threatening disease in which intracranial hemorrhage (ICH) is the major risk. Although thrombocytopenia, which is caused by maternal antibodies against β3 integrin and occasionally by maternal antibodies against other platelet antigens, such as glycoprotein GPIbα, has long been assumed to be the cause of bleeding, the mechanism of ICH has not been adequately explored. Utilizing murine models of FNAIT and a high-frequency ultrasound imaging system, we found that ICH only occurred in fetuses and neonates with anti-β3 integrin-mediated, but not anti-GPIbα-mediated, FNAIT, despite similar thrombocytopenia in both groups. Only anti-β3 integrin-mediated FNAIT reduced brain and retina vessel density, impaired angiogenic signaling, and increased endothelial cell apoptosis, all of which were abrogated by maternal administration of intravenous immunoglobulin (IVIG). ICH and impairment of retinal angiogenesis were further reproduced in neonates by injection of anti-β3 integrin, but not anti-GPIbα antisera. Utilizing cultured human endothelial cells, we found that cell proliferation, network formation, and AKT phosphorylation were inhibited only by murine anti-β3 integrin antisera and human anti-HPA-1a IgG purified from mothers with FNAIT children. Our data suggest that fetal hemostasis is distinct and that impairment of angiogenesis rather than thrombocytopenia likely causes FNAIT-associated ICH. Additionally, our results indicate that maternal IVIG therapy can effectively prevent this devastating disorder.

FM19G11 reverses endothelial dysfunction in rat and human arteries through stimulation of the PI3K/Akt/eNOS pathway, independently of mTOR/HIF-1α activation

BACKGROUND AND PURPOSE

FM19G11 up-regulates mammalian target of rapamycin (mTOR)/hypoxia inducible factor-1α (HIF-1α) and PI3K/Akt pathways, which are involved in endothelial function. We evaluated the effects of FM19G11 on defective endothelial vasodilatation in arteries from rats and humans and investigated the mechanisms involved.

EXPERIMENTAL APPROACH

Effects of chronic in vivo administration of FM19G11 on aortic endothelial vasodilatation were evaluated together with ex vivo treatment in aortic and mesenteric arteries from control and insulin-resistant rats (IRR). Its effects on vasodilator responses of penile arteries (HPRAs) and corpus cavernosum (HCC) from men with vasculogenic erectile dysfunction (ED) (model of human endothelial dysfunction) were also evaluated. Vascular expression of phosphorylated-endothelial NOS (p-eNOS), phosphorylated-Akt (p-Akt) and HIF-1α was determined by immunodetection and cGMP by elisa.

KEY RESULTS

Chronic administration of FM19G11 reversed the impaired endothelial vasodilatation in IRR. Ex vivo treatment with FM19G11 also significantly improved endothelium-dependent vasodilatation in aorta and mesenteric arteries from IRR. These effects were accompanied by the restoration of p-eNOS and cGMP levels in IRR aorta and were prevented by either NOS or PI3K inhibition. p-Akt and p-eNOS contents were increased by FM19G11 in aortic endothelium of IRR. FM19G11-induced restoration of endothelial vasodilatation was unaffected by mTOR/HIF-1α inhibitors. FM19G11 also restored endothelial vasodilatation in HPRA and HCC from ED patients.

CONCLUSIONS AND IMPLICATIONS

Stimulation of the PI3K/Akt/eNOS pathway by FM19G11 alleviates impaired NO-mediated endothelial vasodilatation in rat and human arteries independently of mTOR/HIF-1α activation. This pharmacological strategy could be beneficial for managing pathological conditions associated with endothelial dysfunction, such as ED.

Impaired integrin β3 delays endothelial cell regeneration and contributes to arteriovenous graft failure in mice

OBJECTIVE

Neointima formation is associated with stenosis and subsequent thrombosis in arteriovenous grafts (AVGs). A role of integrin β3 in the neointima formation of AVGs remains poorly understood.

APPROACH AND RESULTS

In integrin β3(-/-) mice, we found significantly accelerated occlusion of AVGs compared with the wild-type mice. This is caused by the development of neointima and lack of endothelial regeneration. The latter is a direct consequence of impaired functions of circulating angiogenic cells (CACs) and platelets in integrin β3(-/-) mice. Evidence suggests the involvement of platelet regulating CAC homing to and differentiation at graft sites via transforming growth factor-β1 and Notch signaling pathway. First, CACs deficient of integrin β3 impaired adhesion activity toward exposed subendothelium. Second, platelets from integrin β3(-/-) mice failed to sufficiently stimulate CACs to differentiate into mature endothelial cells. Finally, we found that transforming growth factor-β1 level was increased in platelets from integrin β3(-/-) mice and resulted in enhanced Notch1 activation in CACs in AVGs. These results demonstrate that integrin β3 is critical for endothelial cell homing and differentiation. The increased transforming growth factor-β1 and Notch1 signaling mediates integrin β3(-/-)-induced AVG occlusion. This accelerated occlusion of AVGs was reversed in integrin β3(-/-) mice transplanted with the bone marrow from wild-type mice.

CONCLUSIONS

Our results suggest that boosting integrin β3 function in the endothelial cells and platelets could prevent neointima and thrombosis in AVGs.

Impact of VEGFA -583C > T polymorphism on serum VEGF levels and the susceptibility to acute chest syndrome in pediatric patients with sickle cell disease

We investigated the association of VEGFA -583C > T on VEGF serum levels and acute chest syndrome (ACS) in 351 pediatric patients with sickle cell disease (SCD), of whom 90 had ACS, and 261 were ACS-free controls. Significant differences in -583C > T minor allele and genotype frequencies were seen between ACS cases and controls, evidenced by enrichment of -583T/T genotypes in patients with ACS, which were linked with reduction in VEGF serum levels. VEGFA -583C > T and reduced VEGF serum levels may influence ACS risk in patients with SCD, which will aid in identifying patients with SCD who are at high risk of ACS.

Endothelial cell senescence and age-related vascular diseases

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

Cathepsin K-mediated Notch1 activation contributes to neovascularization in response to hypoxia

Cysteine proteases play important roles in pathobiology. Here we reveal that cathepsin K (CatK) has a role in ischaemia-induced neovascularization. Femoral artery ligation-induced ischaemia in mice increases CatK expression and activity, and CatK-deficient mice show impaired functional recovery following hindlimb ischaemia. CatK deficiency reduces the levels of cleaved Notch1 (c-Notch1), Hes1 Hey1, Hey2, vascular endothelial growth factor, Flt-1 and phospho-Akt proteins of the ischaemic muscles. In endothelial cells, silencing of CatK mimicked, whereas CatK overexpression enhanced, the levels of c-Notch1 and the expression of Notch downstream signalling molecules, suggesting CatK contributes to Notch1 processing and activates downstream signalling. Moreover, CatK knockdown leads to defective endothelial cell invasion, proliferation and tube formation, and CatK deficiency is associated with decreased circulating endothelial progenitor cells-like CD31(+)/c-Kit(+) cells in mice following hindlimb ischaemia. Transplantation of bone marrow-derived mononuclear cells from CatK(+/+) mice restores the impairment of neovascularization in CatK(-/-) mice. We conclude that CatK may be a potential therapeutic target for ischaemic disease.

Vitronectin regulation of vascular endothelial growth factor-mediated angiogenesis

BACKGROUND

Vascular endothelial growth factor (VEGF) plays a key role in regulating angiogenesis, and this process is largely dependent on the newly formed extracellular matrix (ECM). The levels of vitronectin (VN) are increased in patients with various cardiovascular diseases. A role for VN in regulating VEGF-induced angiogenesis has not been previously reported. We tested the hypothesis that VN regulates VEGFR-2 activation via effects on αvβ3, thus contributing to angiogenesis.

METHODS

We used a 3-dimensional angiogenesis assay, and examined the effects of VN on VEGF-mediated angiogenesis in aortic endothelial cells (ECs) isolated from wild-type and VN-deficient mice.

RESULTS

The addition of multimeric VN significantly enhanced VEGF-induced increases in EC migration and capillary formation. In vitro, Vn(-/-) ECs migrated significantly slower than wild-type ECs. The addition of VN to Vn(-/-) ECs increased EC migration and augmented the promigratory effect of VEGF in a manner that involved VEGFR-2 and Src signaling. Analysis of the mechanisms involved revealed that multimeric VN, but not monomeric VN, binds VEGF and enhances VEGF-induced VEGFR-2/Src activation in ECs.

CONCLUSION

These results underscore the importance of VN in the regulation of angiogenesis induced by VEGF.

Epigenetic mechanisms underlying cardiac degeneration and regeneration

Epigenetic modifications which are defined by DNA methylation, histone modifications and microRNA mediated gene regulation, have been found to be associated with cardiac dysfunction and cardiac regeneration but the mechanisms are unclear. MicroRNA therapies have been proposed for cardiac regeneration and proliferation of stem cells into cardiomyocytes. Cardiovascular disorders are represented by abnormal methylation of CpG islands and drugs that inhibit DNA methyltransferases such as 5-methyl Aza cytidine are under trials. Histone modifications which include acetylation, methylation, phosphorylation, ADP ribosylation, sumoylation and biotinylation are represented within abnormal phenotypes of cardiac hypertrophy, cardiac development and contractility. MicroRNAs have been used efficiently to epigenetically reprogram fibroblasts into cardiomyocytes. MicroRNAs represent themselves as potential biomarkers for early detection of cardiac disorders which are difficult to diagnose and are captured at later stages. Because microRNAs regulate circadian genes, for example a nocturnin gene of circadian clockwork is regulated by miR122, they have a profound role in regulating biological clock and this may explain the high cardiovascular risk during the morning time. This review highlights the role of epigenetics which can be helpful in disease management strategies.

Oxidative stress and vascular inflammation in aging

Vascular aging, a determinant factor for cardiovascular disease and health status in the elderly, is now viewed as a modifiable risk factor. Impaired endothelial vasodilation is a early hallmark of arterial aging that precedes the clinical manifestations of vascular dysfunction, the first step to cardiovascular disease and influencing vascular outcomes in the elderly. Accordingly, the preservation of endothelial function is thought to be an essential determinant of healthy aging. With special attention on the effects of aging on the endothelial function, this review is focused on the two main mechanisms of aging-related endothelial dysfunction: oxidative stress and inflammation. Aging vasculature generates an excess of the reactive oxygen species (ROS), superoxide and hydrogen peroxide, that compromise the vasodilatory activity of nitric oxide (NO) and facilitate the formation of the deleterious radical, peroxynitrite. Main sources of ROS are mitochondrial respiratory chain and NADPH oxidases, although NOS uncoupling could also account for ROS generation. In addition, reduced antioxidant response mediated by erythroid-2-related factor-2 (Nrf2) and downregulation of mitochondrial manganese superoxide dismutase (SOD2) contributes to the establishment of chronic oxidative stress in aged vessels. This is accompanied by a chronic low-grade inflammatory phenotype that participates in defective endothelial vasodilation. The redox-sensitive transcription factor, nuclear factor-κB (NF-κB), is upregulated in vascular cells from old subjects and drives a proinflammatory shift that feedbacks oxidative stress. This chronic NF-κB activation is contributed by increased angiotensin-II signaling and downregulated sirtuins and precludes adequate cellular response to acute ROS generation. Interventions targeted to recover endogenous antioxidant capacity and cellular stress response rather than exogenous antioxidants could reverse oxidative stress-inflammation vicious cycle in vascular aging. Lifestyle attitudes such as caloric restriction and exercise training appear as effective ways to overcome defective antioxidant response and inflammation, favoring successful vascular aging and decreasing the risk for cardiovascular disease.