The Different Effects of VEGFA121 and VEGFA165 on Regulating Angiogenesis Depend on Phosphorylation Sites of VEGFR2

Dual Pigment Epithelium-derived Factor and Hepatocyte Growth Factor Overexpression: A New Therapy for Pulmonary Hypertension

Pulmonary hypertension (PH) is a disease characterized by advanced pulmonary vasculature remodeling that is thought to be curable only through lung transplantation. The application of angiogenic hepatocyte growth factor (HGF) is reported to be protective in PH through its anti-vascular remodeling effect, but excessive HGF-mediated immature neovascularization is not conducive to the restoration of pulmonary perfusion because of apparent vascular leakage. As a canonical antiangiogenic molecule, pigment epithelium-derived factor (PEDF) inhibits angiogenesis and reduces vascular permeability in a variety of diseases. However, the effect of PEDF on HGF-based PH treatment remains to be determined. In this study, monocrotaline-induced PH rats and endothelial cells isolated from rat and human PH lung tissues were used. We assessed PH progression, right cardiac function, and pulmonary perfusion in HGF- and/or PEDF-treated rats with PH. Additionally, the receptor and mechanism responsible for the role of PEDF in HGF-based PH therapy were investigated. In this study, we found that HGF and PEDF jointly prevent PH development and improve right cardiac function in rats with PH. Moreover, PEDF delivery increases the pulmonary perfusion in PH lungs and inhibits immature angiogenesis and vascular endothelial (VE)-cadherin junction disintegration induced by HGF without affecting the therapeutic inhibition of pulmonary vascular remodeling by HGF. Mechanistically, PEDF targets VE growth factor receptor 2 and suppresses its phosphorylation at Y951 and Y1175 but not Y1214. Finally, VE growth factor receptor 2/VE protein tyrosine phosphatase/VE-cadherin complex formation and Akt and Erk1/2 inactivation were observed in rat and human PH lung endothelial cells. Collectively, our data indicate that PEDF additively enhances the efficacy of HGF against PH, which may provide new insights into treatment strategies for clinical PH.

NGF Prevents Loss of TrkA/VEGFR2 Cells, and VEGF Isoform Dysregulation in the Retina of Adult Diabetic Rats

Among the factors involved in diabetic retinopathy (DR), nerve growth factor (NGF) and vascular endothelial growth factor A (VEGFA) have been shown to affect both neuronal survival and vascular function, suggesting that their crosstalk might influence DR outcomes. To address this question, the administration of eye drops containing NGF (ed-NGF) to adult Sprague Dawley rats receiving streptozotocin (STZ) intraperitoneal injection was used as an experimental paradigm to investigate NGF modulation of VEGFA and its receptor VEGFR2 expression. We show that ed-NGF treatment prevents the histological and vascular alterations in STZ retina, VEGFR2 expression decreased in GCL and INL, and preserved the co-expression of VEGFR2 and NGF-tropomyosin-related kinase A (TrkA) receptor in retinal ganglion cells (RGCs). The WB analysis confirmed the NGF effect on VEGFR2 expression and activation, and showed a recovery of VEGF isoform dysregulation by suppressing STZ-induced VEGFA₁₂₁ expression. Reduction in inflammatory and pro-apoptotic intracellular signals were also found in STZ+NGF retina. These findings suggest that ed-NGF administration might favor neuroretina protection, and in turn counteract the vascular impairment by regulating VEGFR2 and/or VEGFA isoform expression during the early stages of the disease. The possibility that an increase in the NGF availability might contribute to the switch from the proangiogenic/apoptotic to the neuroprotective action of VEGF is discussed.

Context dependent role of p53 during the interaction of hepatocellular carcinoma and endothelial cells

BACKGROUND

During the progression of hepatocellular carcinoma (HCC), several angiogenic factors are overexpressed in the hepatic microenvironment, which play a critical role in governing the phenotype of the endothelial cells. Mutation in the p53 gene (TP53) is a common event in HCC that may dysregulate the angiogenic signals. However, their functional messages remain largely unexplored at the onset of metastasis.

METHODS

Role of p53 was studied by siRNA mediated silencing of p53 in HepG2 cells (WTp53), collecting and analyzing their conditioned medium, followed by indirect co-culture with endothelial cells (HUVECs). Gene and protein expression in HCC cells and endothelial cells was studied by RT-qPCR and western blotting respectively. β-catenin protein expression and localization were analyzed by immunocytochemistry.

RESULTS

We have studied a cell-to-cell interaction model to investigate the crosstalk of endothelial and hepatoma cells by either knocking down p53 or by using p53 null low metastatic HCC cell line. In the absence of p53, the HCC cells influence the migration and vascular network formation of endothelial cells through paracrine signaling of VEGF. Secretory VEGF activated the VEGF receptor-2 along with the survival signaling in endothelial cells. However, the β-catenin signal is upregulated in endothelial cells only during interaction with metastatic set up irrespective of absence and presence of p53, indicating context-dependent participation of p53 during communication between hepatoma cells and endothelial cells.

CONCLUSION

This study highlights that the role of p53 on cellular responses during interaction of hepatocellular carcinoma and endothelial cells is distinct to cell types and context.

Zebrafish mutants in vegfab can affect endothelial cell proliferation without altering ERK phosphorylation and are phenocopied by loss of PI3K signaling

The formation of appropriately patterned blood vessel networks requires endothelial cell migration and proliferation. Signaling through the Vascular Endothelial Growth Factor A (VEGFA) pathway is instrumental in coordinating these processes. mRNA splicing generates short (diffusible) and long (extracellular matrix bound) Vegfa isoforms. The differences between these isoforms in controlling cellular functions are not understood. In zebrafish, vegfaa generates short and long isoforms, while vegfab only generates long isoforms. We found that mutations in vegfaa had an impact on endothelial cell (EC) migration and proliferation. Surprisingly, mutations in vegfab more strongly affected EC proliferation in distinct blood vessels, such as intersegmental blood vessels in the zebrafish trunk and central arteries in the head. Analysis of downstream signaling pathways revealed no change in MAPK (ERK) activation, while inhibiting PI3 kinase signaling phenocopied vegfab mutant phenotypes in affected blood vessels. Together, these results suggest that extracellular matrix bound Vegfa might act through PI3K signaling to control EC proliferation in a distinct set of blood vessels during angiogenesis.

Effects of Stem Cell Therapy on Diabetic Mellitus Erectile Dysfunction: A Systematic Review and Meta-analysis

BACKGROUND

Stem cell is considered a potential therapy for treating erectile dysfunction (ED), including diabetic mellitus erectile dysfunction (DMED), which was investigated in some preclinical studies. Several trials introduced stem cell into clinical practice, but divergences emerged.

AIM

To further investigate the therapeutic effects of stem cell on DMED in preclinical studies and investigate some possible factors that influence curative effects.

METHODS

The literature research was conducted in Web of Science and PubMed to retrieve studies utilizing stem cell to treat DMED. Revman 5.3 was used to perform subgroup analysis of intracavernosal pressure/mean artery pressure (ICP/MAP) and structural changes. Publication bias was assessed with Egger's test, funnel plot, and sensitivity analysis by Stata 15.0.

OUTCOMES

The ICP/MAP and structural changes before and after stem cell treatment.

RESULTS

Of 2,115 studies retrieved, 23 studies are eligible. Plus 10 studies from a meta-analysis published in 2016, 33 studies were enrolled. Pooled analysis showed that stem cell ameliorates damaged ICP/MAP (WMD 0.26; 95% CI 0.23-0.29; P < .001) and structural changes induced by diabetes. Subgroup analysis indicated that adipose-derived mesenchymal stem cell (ADSC) may have better efficacy than bone marrow-derived mesenchymal stem cell (BMSC) (χ2= 4.21, P = .04; ADSC WMD 0.28, 95% CI [0.24-0.32] vs BMSC WMD 0.22 95% CI [0.17-0.26]). Transplantation type, diabetes type, and cell number make no difference to curative effects. Gene modification and therapy combination proved promising in improving the therapeutic effects of stem cell.

CLINICAL TRANSLATION

The evidence reminded that ADSC may be prior to BMSC in clinical trials and autotransplantation is probably not compulsory in the clinical practice of stem cell.

STRENGTHS AND LIMITATIONS

The study number and sample size are large enough. However, high degree of heterogeneity remains after subgroup analysis.

CONCLUSION

This meta-analysis suggests the efficacy of stem cell therapy for DMED and the possible superiority of ADSC over BMSC in erection restoration and structure renovation.

Alternative Splicing: A Key Mediator of Diabetic Vasculopathy

Cardiovascular disease is the leading cause of death amongst diabetic individuals. Atherosclerosis is the prominent driver of diabetic vascular complications, which is triggered by the detrimental effects of hyperglycemia and oxidative stress on the vasculature. Research has extensively shown diabetes to result in the malfunction of the endothelium, the main component of blood vessels, causing severe vascular complications. The pathogenic mechanism in which diabetes induces vascular dysfunction, however, remains largely unclear. Alternative splicing of protein coding pre-mRNAs is an essential regulatory mechanism of gene expression and is accepted to be intertwined with cellular physiology. Recently, a role for alternative splicing has arisen within vascular health, with aberrant mis-splicing having a critical role in disease development, including in atherosclerosis. This review focuses on the current knowledge of alternative splicing and the roles of alternatively spliced isoforms within the vasculature, with a particular focus on disease states. Furthermore, we explore the recent elucidation of the alternatively spliced QKI gene within vascular cell physiology and the onset of diabetic vasculopathy. Potential therapeutic strategies to restore aberrant splicing are also discussed.

IsoDA: Isoform-Disease Association Prediction by Multiomics Data Fusion

A gene can be spliced into different isoforms by alternative splicing, which contributes to the functional diversity of protein species. Computational prediction of gene-disease associations (GDAs) has been studied for decades. However, the process of identifying the isoform-disease associations (IDAs) at a large scale is rarely explored, which can decipher the pathology at a more granular level. The main bottleneck is the lack of IDAs in current databases and the multilevel omics data fusion. To bridge this gap, we propose a computational approach called Isoform-Disease Association prediction by multiomics data fusion (IsoDA) to predict IDAs. Based on the relationship between a gene and its spliced isoforms, IsoDA first introduces a dispatch and aggregation term to dispatch gene-disease associations to individual isoforms, and reversely aggregate these dispatched associations to their hosting genes. At the same time, it fuses the genome, transcriptome, and proteome data by joint matrix factorization to improve the prediction of IDAs. Experimental results show that IsoDA significantly outperforms the related state-of-the-art methods at both the gene level and isoform level. A case study further shows that IsoDA credibly identifies three isoforms spliced from apolipoprotein E, which have individual associations with Alzheimer's disease, and two isoforms spliced from vascular endothelial growth factor A, which have different associations with coronary heart disease. The codes of IsoDA are available at http://mlda.swu.edu.cn/codes.php?name=IsoDA.

Intracavernosal Adeno-Associated Virus-Mediated S100A1 Gene Transfer Enhances Erectile Function in Diabetic Rats by Promoting Cavernous Angiogenesis via VEGF-A/VEGFR2 Signaling

INTRODUCTION

Novel therapeutic targets for diabetes-induced erectile dysfunction (DED) are urgently needed. Previous studies have proved that S100A1, a small Ca²⁺-binding protein, is a pluripotent regulator of cardiovascular pathophysiology. Its absence is associated with endothelial dysfunction, the central event linking cardiovascular changes in diabetes. However, the role of S100A1 in DED remains unknown.

AIM

To explore the effect and underlying mechanisms of S100A1 in restoring erectile function in type I diabetic rat model.

METHODS

Diabetes was induced by intraperitoneal injection of streptozotocin and then screened by apomorphine (APO) to confirm erectile dysfunction. Rats that met the criteria of penile erection were marked as APO-positive; otherwise, the result was APO-negative. In experiment 1, S100A1 gene expression alterations in the corpus cavernosum in moderate and established stages of DED were analyzed. In experiment 2, S100A1 and control GFP gene were delivered into the corpus cavernosum in APO-negative rats by adeno-associated virus (AAV) serotype 9. Erectile function was assessed at 4 weeks after gene therapy.

MAIN OUTCOME MEASURES

Erectile response, histologic and molecular alterations.

RESULTS

S100A1 protein was localized to the area surrounding the cavernosal sinusoids in the penis, and it was gradually downregulated synchronized with the progression of DED. Compared with an injection of AAV-GFP, a single injection of AAV-S100A1 significantly restored erectile function in diabetic rats. S100A1 overexpression significantly upregulated the expression of endogenous VEGF-A, promoted VEGFR2 internalization, and subsequently triggered the protein kinase B-endothelial nitric oxide synthase pathway in diabetic erectile tissues. Marked increases in nitric oxide and endothelial content were noted in AAV-S100A1-treated diabetic rats.

CLINICAL IMPLICATIONS

Local S100A1 overexpression may be an alternative therapy for DED and should be further investigated by future clinical studies.

STRENGTH & LIMITATIONS

This is the first study demonstrating the angiogenic role of S100A1 in DED, but does not preclude the contribution of the effects of S100A1 in other tissues such as the neuronal tissue on the functional effects observed in erectile responses.

CONCLUSION

The decreased expression of S100A1 during hyperglycemia might be important in the development of erectile dysfunction. S100A1 may play a potential role in restoring erectile function in rats with DED through modulating cavernous angiogenesis. Yu Z, Zhang Y, Tang Z, et al. Intracavernosal Adeno-Associated Virus-Mediated S100A1 Gene Transfer Enhances Erectile Function in Diabetic Rats by Promoting Cavernous Angiogenesis via VEGF-A/VEGFR2 Signaling. J Sex Med 2019;16:1344-1354.

Alternative Splicing in Angiogenesis

Alternative splicing of pre-mRNA allows the generation of multiple splice isoforms from a given gene, which can have distinct functions. In fact, splice isoforms can have opposing functions and there are many instances whereby a splice isoform acts as an inhibitor of canonical isoform function, thereby adding an additional layer of regulation to important processes. Angiogenesis is an important process that is governed by alternative splicing mechanisms. This review focuses on the alternative spliced isoforms of key genes that are involved in the angiogenesis process; VEGF-A, VEGFR1, VEGFR2, NRP-1, FGFRs, Vasohibin-1, Vasohibin-2, HIF-1α, Angiopoietin-1 and Angiopoietin-2.

Molecular Pharmacology of VEGF-A Isoforms: Binding and Signalling at VEGFR2

Vascular endothelial growth factor-A (VEGF-A) is a key mediator of angiogenesis, signalling via the class IV tyrosine kinase receptor family of VEGF Receptors (VEGFRs). Although VEGF-A ligands bind to both VEGFR1 and VEGFR2, they primarily signal via VEGFR2 leading to endothelial cell proliferation, survival, migration and vascular permeability. Distinct VEGF-A isoforms result from alternative splicing of the Vegfa gene at exon 8, resulting in VEGFxxxa or VEGFxxxb isoforms. Alternative splicing events at exons 5⁻7, in addition to recently identified posttranslational read-through events, produce VEGF-A isoforms that differ in their bioavailability and interaction with the co-receptor Neuropilin-1. This review explores the molecular pharmacology of VEGF-A isoforms at VEGFR2 in respect to ligand binding and downstream signalling. To understand how VEGF-A isoforms have distinct signalling despite similar affinities for VEGFR2, this review re-evaluates the typical classification of these isoforms relative to the prototypical, “pro-angiogenic” VEGF165a. We also examine the molecular mechanisms underpinning the regulation of VEGF-A isoform signalling and the importance of interactions with other membrane and extracellular matrix proteins. As approved therapeutics targeting the VEGF-A/VEGFR signalling axis largely lack long-term efficacy, understanding these isoform-specific mechanisms could aid future drug discovery efforts targeting VEGF receptor pharmacology.

Panax notoginseng Promotes Repair of Colonic Microvascular Injury in Sprague-Dawley Rats with Experimental Colitis

To investigate the therapeutic effects of PN on intestinal inflammation and microvascular injury and its mechanisms, dextran sodium sulfate- (DSS-) or iodoacetamide- (IA-) induced rat colitis models were used. After colitis model was established, PN was orally administered for 7 days at daily dosage of 1.0 g/kg. Obvious colonic inflammation and mucosal injuries and microvessels were observed in DSS- and IA-induced colitis groups. DAI scores, serum concentrations of VEGFA121, VEGFA165, VEGFA165/VEGFA121, IL-6, and TNF-α, and expression of Rap1GAP and TSP1 proteins in the colon were significantly higher while serum concentrations of IL-4 and IL-10 and MVD in colon were significantly lower in the colitis model groups than in the normal control group. PN promoted repair of colonic mucosal injury and microvessels, attenuated inflammation, and decreased DAI scores in rats with colitis. PN also decreased the serum concentrations of VEGFA121, VEGFA165, VEGFA165/VEGFA121, IL-6, and TNF-α and increased the serum concentrations of IL-4 and IL-10, with the expression of Rap1GAP and TSP1 proteins in colonic mucosa being downregulated. The constituents of PN were identified with HPLC-DAD. To sum up, PN could promote repair of injuries of colonic mucosa and microvessels via downregulating VEGFA isoforms and inhibiting Rap1GAP/TSP1 signaling pathway.

Effects of initiating time and dosage of Panax notoginseng on mucosal microvascular injury in experimental colitis

AIM

To investigate the effects of Panax notoginseng (PN) on microvascular injury in colitis, its mechanisms, initial administration time and dosage.

METHODS

Dextran sodium sulfate (DSS)- or iodoacetamide (IA)-induced rat colitis models were used to evaluate and investigate the effects of ethanol extract of PN on microvascular injuries and their related mechanisms. PN administration was initiated at 3 and 7 d after the model was established at doses of 0.5, 1.0 and 2.0 g/kg for 7 d. The severity of colitis was evaluated by disease activity index (DAI). The pathological lesions were observed under a microscope. Microvessel density (MVD) was evaluated by immunohistochemistry. Vascular permeability was evaluated using the Evans blue method. The serum concentrations of cytokines, including vascular endothelial growth factor (VEGF)A121, VEGFA165, interleukin (IL)-4, IL-6, IL-10 and tumor necrosis factor (TNF)-α, were detected by enzyme-linked immunosorbent assay. Myeloperoxidase (MPO) and superoxide dismutase (SOD) were measured to evaluate the level of oxidative stress. Expression of hypoxia-inducible factor (HIF)-1α protein was detected by western blotting.

RESULTS

Obvious colonic inflammation and injuries of mucosa and microvessels were observed in DSS- and IA-induced colitis groups. DAI scores, serum concentrations of VEGFA121, VEGFA165, VEGFA165/VEGFA121, IL-6 and TNF-α, and concentrations of MPO and HIF-1α in the colon were significantly higher while serum concentrations of IL-4 and IL-10 and MVD in colon were significantly lower in the colitis model groups than in the normal control group. PN promoted repair of injuries of colonic mucosa and microvessels, attenuated inflammation, and decreased DAI scores in rats with colitis. PN also decreased the serum concentrations of VEGFA121, VEGFA165, VEGFA165/VEGFA121, IL-6 and TNF-α, and concentrations of MPO and HIF-1α in the colon, and increased the serum concentrations of IL-4 and IL-10 as well as the concentration of SOD in the colon. The efficacy of PN was dosage dependent. In addition, DAI scores in the group administered PN on day 3 were significantly lower than in the group administered PN on day 7.

CONCLUSION

PN repairs vascular injury in experimental colitis via attenuating inflammation and oxidative stress in the colonic mucosa. Efficacy is related to initial administration time and dose.