Selective requirement for Src kinases during VEGF-induced angiogenesis and vascular permeability

Endothelial transcriptomic, epigenomic and proteomic data challenge the proposed role for TSAd in vascular permeability

The vascular endothelial growth factor VEGF drives excessive vascular permeability to cause tissue-damaging oedema in neovascular and inflammatory diseases across multiple organs. Several molecular pathways have been implicated in VEGF-induced hyperpermeability, including binding of the VEGF-activated tyrosine kinase receptor VEGFR2 by the T-cell specific adaptor (TSAd) to recruit a SRC family kinase to induce junction opening between vascular endothelial cells (ECs). Inconsistent with a universal role for TSAd in permeability signalling, immunostaining approaches previously reported TSAd only in dermal and kidney vasculature. To address this discrepancy, we have mined publicly available omics data for expression of TSAd and other permeability-relevant signal transducers in multiple organs affected by VEGF-induced vascular permeability. Unexpectedly, TSAd transcripts were largely absent from EC single cell RNAseq data, whereas transcripts for other permeability-relevant signal transducers were detected readily. TSAd transcripts were also lacking from half of the EC bulk RNAseq datasets examined, and in the remaining datasets appeared at low levels concordant with models of leaky transcription. Epigenomic EC data located the TSAd promoter to closed chromatin in ECs, and mass spectrometry-derived EC proteomes typically lacked TSAd. By suggesting that TSAd is not actively expressed in ECs, our findings imply that TSAd is likely not critical for linking VEGFR2 to downstream signal transducers for EC junction opening.

Shear stress-induced restoration of pulmonary microvascular endothelial barrier function following ischemia reperfusion injury requires VEGFR2 signaling

Normal shear stress produced by blood flow is sensed by the vascular endothelium and required for maintenance of the homeostatic functions of the endothelium in systemic conduit and resistance vessels. Many critical illnesses are characterized by periods of abnormally reduced or absent shear stress in the lung (e.g., hemorrhagic shock, embolism, ischemia reperfusion injury, and lung transplantation) and are complicated by pulmonary edema following reperfusion due to microvascular leak. The role of shear stress in regulating the pulmonary microvascular endothelial barrier in the intact vascular bed has not been previously examined. We tested the hypothesis that, in lungs injured by a period of ischemia and reperfusion (IRI), reduced shear stress contributes to increased pulmonary microvascular endothelial barrier permeability and edema formation. Furthermore, we examined the role of vascular endothelial-derived growth factor receptor 2 (VEGFR2) as a mechanosensor mediating the endothelial response to this altered shear stress. Following IRI, we perfused isolated ventilated mouse lungs with a low viscosity solution (LVS) or a higher, physiological viscosity solution (PVS) at constant flow to produce differing endothelial shear stresses in the intact microcirculation. Lungs perfused with LVS developed pulmonary edema due to increased endothelial permeability whereas those perfused with PVS were protected from edema formation by reduced endothelial permeability. This effect of PVS required normal VEGFR2 mechanoreceptor function. These data show for the first time that shear stress has an important role in restoring endothelial barrier function in the intact pulmonary microcirculation following injury and have important implications for the treatment of pulmonary edema in critically ill patients.NEW & NOTEWORTHY Critical illnesses are frequently complicated by noncardiogenic pulmonary edema. Many such illnesses include periods of reduced blood flow, often accompanied by hemodilution, which together reduce endothelial shear stress. We report that in ischemia-reperfusion injury reduced shear stress contributes to increased permeability of the in situ pulmonary microvascular endothelium and worsens alveolar edema. Restoring shear stress toward normal reduces endothelial permeability and edema formation, an effect that requires the normal mechanoreceptor function of VEGFR2.

Reactive Oxygen Species Responsive Supramolecular Prodrug Eyedrops for the Treatment of Choroidal Neovascularization

Choroidal neovascularization (CNV) represents a hallmark of neovascular fundus diseases, including age-related macular degeneration and diabetic retinopathy. Traditional eyedrops have encountered formidable challenges in treating CNV, primarily due to their extremely poor intraocular bioavailability and potential adverse off-target effects. Herein, an ocular-permeable supramolecular prodrug eyedrop (Di-DAS/P-PCD) has been developed for the on-demand delivery of antiangiogenic agents in the oxidative microenvironment of CNV. The eyedrop nanoformulation is composed of cell-penetrating peptide-modified PEGylated cyclodextrin (P-PCD) and reactive oxygen species (ROS)-sensitive antiangiogenic dasatinib prodrug Di-DAS. In a laser-induced CNV mouse model, daily instillation of Di-DAS/P-PCD has achieved remarkable penetration into the choroid and significantly suppressed CNV growth while exhibiting a good biocompatibility profile. Our results highlight the potential of the supramolecular prodrug eyedrops as a versatile approach for the targeted treatment of CNV and other neovascular eye disorders.

Csk controls leukocyte extravasation via local regulation of Src family kinases and cortactin signaling

C-terminal Src kinase (Csk) targets Src family kinases (SFKs) and thereby inactivates them. We have previously shown that Csk binds to phosphorylated tyrosine 685 of VE-cadherin, an adhesion molecule of major importance for the regulation of endothelial junctions. This tyrosine residue is an SFK target, and its mutation (VE-cadherin-Y685F) inhibits the induction of vascular permeability in various inflammation models. Nevertheless, surprisingly, it increases leukocyte extravasation. Here, we investigated whether endothelial Csk is involved in these effects. We found that the deficiency of Csk in endothelial cells augments SFK activation and the phosphorylation of VE-cadherin-Y685 but had no net effect on vascular leak formation. In contrast, the lack of endothelial Csk enhanced leukocyte adhesion and transmigration in vitro and in vivo. Furthermore, the silencing of Csk increased tyrosine phosphorylation of the SFK substrate cortactin. Importantly, the effects of Csk silencing on the increase in SFK activation, cortactin phosphorylation, and neutrophil diapedesis were all dependent on Y685 of VE-cadherin. Deletion of cortactin, in turn, erased the supporting effect of Csk silencing on leukocyte transmigration. We have previously shown that leukocyte transmigration is regulated by endothelial cortactin in an ICAM-1-dependent manner. In line with this, blocking of ICAM-1 erased the supporting effect of Csk silencing on leukocyte transmigration. Collectively, our results establish a negative feedback loop that depends on the phosphorylation of VE-cadherin-Y685, which recruits Csk, which in turn dampens the activation of SFK and cortactin and thereby the clustering of ICAM-1 and the extravasation of neutrophils.

In vitro throughput screening of anticancer drugs using patient-derived cell lines cultured on vascularized three-dimensional stromal tissues

The development of high-throughput anticancer drug screening methods using patient-derived cancer cell (PDC) lines that maintain their original characteristics in an in vitro three-dimensional (3D) culture system poses a significant challenge to achieving personalized cancer medicine. Because stromal tissue plays a critical role in the composition and maintenance of the cancer microenvironment, in vitro 3D-culture using reconstructed stromal tissues has attracted considerable attention. Here, a simple and unique in vitro 3D-culture method using heparin and collagen together with fibroblasts and endothelial cells to fabricate vascularized 3D-stromal tissues for in vitro culture of PDCs is reported. Whereas co-treatment with bevacizumab, a monoclonal antibody against vascular endothelial growth factor, and 5-fluorouracil significantly reduced the survival rate of 3D-cultured PDCs to 30%, separate addition of each drug did not induce comparable strong cytotoxicity, suggesting the possibility of evaluating the combined effect of anticancer drugs and angiogenesis inhibitors. Surprisingly, drug evaluation using eight PDC lines with the 3D-culture method resulted in a drug efficacy concordance rate of 75% with clinical outcomes. The model is expected to be applicable to in vitro throughput drug screening for the development of personalized cancer medicine. STATEMENT OF SIGNIFICANCE: To replicate the cancer microenvironment, we constructed a cancer-stromal tissue model in which cancer cells are placed above and inside stromal tissue with vascular network structures derived from vascular endothelial cells in fibroblast tissue using CAViTs method. Using this method, we were able to reproduce the invasion and metastasis processes of cancer cells observed in vivo. Using patient-derived cancer cells, we assessed the possibility of evaluating the combined effect with an angiogenesis inhibitor. Further, primary cancer cells also grew on the stromal tissues with the normal medium. These data suggest that the model may be useful for new in vitro drug screening and personalized cancer medicine.

c-Src-induced vascular malformations require localised matrix degradation at focal adhesions

Endothelial cells lining the blood vessel wall communicate intricately with the surrounding extracellular matrix, translating mechanical cues into biochemical signals. Moreover, vessels require the capability to enzymatically degrade the matrix surrounding them, to facilitate vascular expansion. c-Src plays a key role in blood vessel growth, with its loss in the endothelium reducing vessel sprouting and focal adhesion signalling. Here, we show that constitutive activation of c-Src in endothelial cells results in rapid vascular expansion, operating independently of growth factor stimulation or fluid shear stress forces. This is driven by an increase in focal adhesion signalling and size, with enhancement of localised secretion of matrix metalloproteinases responsible for extracellular matrix remodelling. Inhibition of matrix metalloproteinase activity results in a robust rescue of the vascular expansion elicited by heightened c-Src activity. This supports the premise that moderating focal adhesion-related events and matrix degradation can counteract abnormal vascular expansion, with implications for pathologies driven by unusual vascular morphologies.

Molecular Mechanisms Regulating Vascular Endothelial Permeability

Vascular endothelial cells form a monolayer in the vascular lumen and act as a selective barrier to control the permeability between blood and tissues. To maintain homeostasis, the endothelial barrier function must be strictly integrated. During acute inflammation, vascular permeability temporarily increases, allowing intravascular fluid, cells, and other components to permeate tissues. Moreover, it has been suggested that the dysregulation of endothelial cell permeability may cause several diseases, including edema, cancer, and atherosclerosis. Here, we reviewed the molecular mechanisms by which endothelial cells regulate the barrier function and physiological permeability.

Ephs in cancer progression: complexity and context-dependent nature in signaling, angiogenesis and immunity

Eph receptors constitute the largest family of receptor tyrosine kinases, comprising 14 distinct members classified into two subgroups: EphAs and EphBs.. Despite their essential functions in normal physiological processes, accumulating evidence suggests that the involvement of the Eph family in cancer is characterized by a dual and often contradictory nature. Research indicates that Eph/ephrin bidirectional signaling influences cell-cell communication, subsequently regulating cell migration, adhesion, differentiation and proliferation. The contradictory functionalities may arise from the diversity of Eph signaling pathways and the heterogeneity of different cancer microenvironment. In this review, we aim to discuss the dual role of the Eph receptors in tumor development, attempting to elucidate the paradoxical functionality through an exploration of Eph receptor signaling pathways, angiogenesis, immune responses, and more. Our objective is to provide a comprehensive understanding of the molecular mechanisms underlying tumor development. Additionally, we will explore the evolving landscape of utilizing Eph receptors as potential targets for tumor therapy and diagnostic tools.

The BulkECexplorer compiles endothelial bulk transcriptomes to predict functional versus leaky transcription

Transcriptomic data can be mined to understand the molecular activity of cell types. Yet, functional genes may remain undetected in RNA sequencing (RNA-seq) experiments for technical reasons, such as insufficient read depth or gene dropout. Conversely, RNA-seq experiments may detect lowly expressed mRNAs thought to be biologically irrelevant products of leaky transcription. To represent a cell type's functional transcriptome more accurately, we propose compiling many bulk RNA-seq datasets into a compendium and applying established classification models to predict whether detected transcripts are likely products of active or leaky transcription. Here, we present the BulkECexplorer (bulk RNA-seq endothelial cell explorer) compendium of 240 bulk RNA-seq datasets from five vascular endothelial cell subtypes. This resource reports transcript counts for genes of interest and predicts whether detected transcripts are likely the products of active or leaky gene expression. Beyond its usefulness for vascular biology research, this resource provides a blueprint for developing analogous tools for other cell types.

Hexane Fraction of Adenophora triphylla var. japonica Root Extract Inhibits Angiogenesis and Endothelial Cell-Induced Erlotinib Resistance in Lung Cancer Cells

The aim of this study was to investigate the anti-angiogenic effects of the hexane fraction of Adenophora triphylla var. japonica root extract (HAT) and its influence on the development of erlotinib resistance in human lung cancer cells. HAT significantly reduced the migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs). The phosphorylation levels of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream molecules were decreased via HAT, indicating its anti-angiogenic potential in endothelial cells (ECs). A docking analysis demonstrated that β-sitosterol and lupeol, representative components of HAT, exhibit a high affinity for binding to VEGFR2. In addition, conditioned media from HAT-pretreated H1299 human lung cancer cells attenuated cancer-cell-induced chemotaxis of HUVECs, which was attributed to the decreased expression of angiogenic and chemotactic factors in H1299 cells. Interestingly, co-culture of erlotinib-sensitive PC9 human lung cancer cells with HUVECs induced erlotinib resistance in PC9 cells. However, co-culture with HAT-pretreated HUVECs partially restored the sensitivity of PC9 cells to erlotinib. HAT inhibited the development of erlotinib resistance by attenuating hepatocyte growth factor (HGF) production by ECs. Taken together, our results demonstrate that HAT exerts its anticancer effects by regulating the crosstalk between ECs and lung cancer cells.

Umbilical cord mesenchymal stem cells from gestational diabetes show impaired ability to up-regulate paracellular permeability from sub-endothelial niche

In vitro studies have shown that Wharton's jelly mesenchymal stem cells (WJ-MSCs) can cross umbilical and uterine endothelial barriers and up-regulate endothelial junctional integrity from sub-endothelial niches. This pericytic behaviour may be lost in pregnancies complicated by gestational diabetes (GDM), where increased vascular permeability and junctional disruption are reported. The aim of the present study was to investigate whether WJ-MSCs isolated from GDM pregnancies displayed any changes in morphology, proliferation, VEGF-A secretion, and their ability to influence paracellular junctional composition and permeability. WJ-MSCs were isolated from human umbilical cords from normal pregnancies (nWJ-MSCs, n=13) and those complicated by GDM (gWJ-MSCs), either diet-controlled (d-GDM, n=13) or metformin-treated (m-GDM, n=9). We recorded that 4-fold more WJ-MSCs migrated from m-GDM, and 2.5-fold from d-GDM cord samples compared with the normal pregnancy. gWJ-MSCs showed a less predominance of spindle-shaped morphology and secreted 3.8-fold more VEGF-A compared with nWJ-MSCs. The number of cells expressing CD105 (Endoglin) was higher in gWJ-MSCs compared with nWJ-MSCs (17%) at P-2. The tracer leakage after 24 h across the HUVEC + gWJ-MSCs bilayer was 22.13% and 11.2% higher in the m-GDM and d-GDM, respectively, HUVEC + nWJ-MSCs. Transfection studies with siRNAs that target Endoglin were performed in n-WJ-MSCs; transfected cells were co-cultured with HUVEC followed by permeability studies and VE-cadherin analyses. Loss of Endoglin also led to increased VEGF-A secretion, increased permeability and affected endothelial stabilization. These results reinforce the pericytic role of nWJ-MSCs to promote vascular repair and the deficient ability of gWJ-MSCs to maintain endothelial barrier integrity.

Sophoridine Counteracts Obesity via Src-Mediated Inhibition of VEGFR Expression and PI3K/AKT Phosphorylation

Sophoridine (SRP) is a natural quinolizidine alkaloid found in many traditional Chinese herbs, though its effect on adipose tissue is unclear. We improved serum lipid levels by administering SRP by gavage in high-fat diet (HFD)-fed C57BL/6 mice. After 11 weeks, SRP supplementation significantly reduced body weight gain and improved glucose homeostasis, while reducing subcutaneous fat and liver weight. SRP also inhibited cell proliferation and differentiation of 3T3-L1 cells. Proteomics analysis revealed that SRP inhibits adipocyte differentiation by interacting with Src, thereby suppressing vascular endothelial growth factor receptor 2 (VEGFR2) expression and PI3K/AKT phosphorylation. This study provides an empirical basis for the treatment of obesity with small molecules.

Myocardial Oedema as a Consequence of Viral Infection and Persistence-A Narrative Review with Focus on COVID-19 and Post COVID Sequelae

Microvascular integrity is a critical factor in myocardial fluid homeostasis. The subtle equilibrium between capillary filtration and lymphatic fluid removal is disturbed during pathological processes leading to inflammation, but also in hypoxia or due to alterations in vascular perfusion and coagulability. The degradation of the glycocalyx as the main component of the endothelial filtration barrier as well as pericyte disintegration results in the accumulation of interstitial and intracellular water. Moreover, lymphatic dysfunction evokes an increase in metabolic waste products, cytokines and inflammatory cells in the interstitial space contributing to myocardial oedema formation. This leads to myocardial stiffness and impaired contractility, eventually resulting in cardiomyocyte apoptosis, myocardial remodelling and fibrosis. The following article reviews pathophysiological inflammatory processes leading to myocardial oedema including myocarditis, ischaemia-reperfusion injury and viral infections with a special focus on the pathomechanisms evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In addition, clinical implications including potential long-term effects due to viral persistence (long COVID), as well as treatment options, are discussed.

Therapeutic potential of elema-1,3,7(11),8-tetraen-8,12-lactam from Curcuma wenyujin on diabetic retinopathy via anti-inflammatory and anti-angiogenic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, the causes of diabetic retinopathy (DR) are blood stasis and heat. Curcuma wenyujin Y. H. Chen & C. Ling and its extracts have the effects of promoting blood circulation to remove blood stasis, clearing the heart, and cooling the blood, and have been used in the treatment of DR. Elema-1,3,7 (11),8-tetraen-8,12-lactam (Ele), an N-containing sesquiterpene isolated from this plant. However, the anti-inflammatory and anti-angiogenic effects of Ele and its therapeutic potential in DR are still unknown.

AIM OF THE STUDY

To evaluate the anti-inflammatory and anti-angiogenic effects of Ele and its therapeutic potential in DR.

MATERIALS AND METHODS

In vitro, anti-inflammatory and anti-angiogenic effects were assessed using TNF-α or VEGF-stimulated HUVECs. Protein expression was analyzed using Western blotting. ICAM-1 and TNF-α mRNA expressions were analyzed using real-time quantitative RT-PCR. The therapeutic potential in DR was assessed using both animal models of STZ-induced diabetes and oxygen-induced retinopathy. The retinal vascular permeability was measured using Evans blue, and the quantitation of retinal leukostasis using FITC-coupled Con A. The retinal neovascular tufts were analyzed using fluorescein angiography and counting pre-retinal vascular lumens.

RESULTS

Ele inhibited NF-κB pathway, and ICAM-1, TNF-α mRNA expression in TNF-α- stimulated HUVECs. It also inhibits the multistep process of angiogenesis by inhibiting the phosphorylation of VEGFR2 and its downstream signaling kinases Src, Erk1/2, Akt, and mTOR in VEGF-stimulated HUVECs. Intravitreal injection of Ele can significantly reduce retinal microvascular leakage, leukostasis, and expression of ICAM-1, TNF-α in diabetic rats and inhibits oxygen-induced retinal neovascularization and VEGFR2 phosphorylation in OIR mice.

CONCLUSIONS

Ele has anti-inflammatory and anti-angiogenic effects through inhibiting NF-κB and VEGFR2 signaling pathways, and it may be a potential drug candidate for DR.

DNase aggravates intestinal microvascular injury in IBD patients by releasing NET-related proteins

Neutrophils accumulate in the inflammatory mucosa of patients with inflammatory bowel disease (IBD), and excessive release of NETs (neutrophil extracellular traps may be one of the important factors that cause IBD progression. However, the specific mechanism underlying vascular injury caused by NETs remains unclear. Immunofluorescence, ELISA, and flow cytometry were used in this study to detect the expression of NETs and DNase in the tissue and peripheral blood samples of patients with IBD. DSS mouse model was used to detect colon injury and vascular permeability. We found that NETs and DNase levels increased in the colon of patients with IBD. We found an increase in the activity of NET-related MPO released by DNase. DNase released NET-related proteins and damaged vascular endothelial cells in vitro. In DSS mouse model, the synchronous increase of DNase and NETs in the colon leads to an increase in vascular injury markers (CD44, sTM). DNase aggravated colon injury and increased vascular permeability in vivo, which was inhibited by gentamicin sulfate (GS). GS does not reduce the expression of DNase, but rather reduces the release of NET-related proteins to protect vascular endothelium by inhibiting DNase activity. MPO and histones synergistically damaged the vascular endothelium, and vascular injury can be improved by their active inhibitors. We further found that H2 O2 is an important substrate for MPO induced vascular damage. In conclusion, in IBD, DNase, and NET levels increased synchronously in the lesion area and released NET-related proteins to damage the vascular endothelium. Therefore, targeting DNase may be beneficial for the treatment of IBD.

Role of c-Src in Carcinogenesis and Drug Resistance

The aberrant transformation of normal cells into cancer cells, known as carcinogenesis, is a complex process involving numerous genetic and molecular alterations in response to innate and environmental stimuli. The Src family kinases (SFK) are key components of signaling pathways implicated in carcinogenesis, with c-Src and its oncogenic counterpart v-Src often playing a significant role. The discovery of c-Src represents a compelling narrative highlighting groundbreaking discoveries and valuable insights into the molecular mechanisms underlying carcinogenesis. Upon oncogenic activation, c-Src activates multiple downstream signaling pathways, including the PI3K-AKT pathway, the Ras-MAPK pathway, the JAK-STAT3 pathway, and the FAK/Paxillin pathway, which are important for cell proliferation, survival, migration, invasion, metastasis, and drug resistance. In this review, we delve into the discovery of c-Src and v-Src, the structure of c-Src, and the molecular mechanisms that activate c-Src. We also focus on the various signaling pathways that c-Src employs to promote oncogenesis and resistance to chemotherapy drugs as well as molecularly targeted agents.

Tumor cells-derived exosomal noncoding RNAs in cancer angiogenesis: Molecular mechanisms and prospective

Exosomes, heterogeneous, membrane-bound nanoparticles that originated from eukaryotic cells, contribute to intracellular communication by transferring various biomolecules both on their surface and as internal cargo. One of the most significant current discussions on cancer progression is noncoding RNAs cargo of exosomes, which can regulate angiogenesis in tumor. A growing body of evidence shows that exosomes from tumor cells contain various microRNAs, long noncoding RNAs, and circular RNAs that can promote tumor progression by inducing angiogenesis. However, some noncoding RNAs may inhibit cancer angiogenesis. Targeting angiogenic noncoding RNA of exosomes may serve as a hopeful implement for cancer therapy. In this review, we discuss the latest knowledge of the roles of exosomal noncoding RNAs in tumor angiogenesis Understanding the biology of exosomal noncoding RNAs can help scientists plan exosomes-based innovations for the treatment of cancer angiogenesis and cancer biomarkers.

Nonfunctional TGF-β/ALK1/ENG signaling pathway supports neutrophil proangiogenic activity in hereditary hemorrhagic telangiectasia

The transforming growth factor β (TGF-β)/ALK1/ENG signaling pathway maintains quiescent state of endothelial cells, but at the same time, it regulates neutrophil functions. Importantly, mutations of this pathway lead to a rare autosomal disorder called hereditary hemorrhagic telangiectasia (HHT), characterized with abnormal blood vessel formation (angiogenesis). As neutrophils are potent regulators of angiogenesis, we investigated how disturbed TGF-β/ALK1/ENG signaling influences angiogenic properties of these cells in HHT. We could show for the first time that not only endothelial cells, but also neutrophils isolated from such patients are ENG/ALK1 deficient. This deficiency obviously stimulates proangiogenic switch of such neutrophils. Elevated proangiogenic activity of HHT neutrophils is mediated by the increased spontaneous degranulation of gelatinase granules, resulting in high release of matrix-degrading matrix metalloproteinase 9 (MMP9). In agreement, therapeutic disturbance of this process using Src tyrosine kinase inhibitors impaired proangiogenic capacity of such neutrophils. Similarly, inhibition of MMP9 activity resulted in significant impairment of neutrophil-mediated angiogenesis. All in all, deficiency in TGF-β/ALK1/ENG signaling in HHT neutrophils results in their proangiogenic activation and disease progression. Therapeutic strategies targeting neutrophil degranulation and MMP9 release and activity may serve as a potential therapeutic option for HHT.

Red Light-Triggered Anti-Angiogenic and Photodynamic Combination Therapy of Age-Related Macular Degeneration

Choroidal neovascularization (CNV) is the key pathological event of wet age-related macular degeneration (wAMD) leading to irreversible vision loss. Currently, anti-angiogenic therapy with anti-vascular endothelial growth factor (VEGF) agents has become the standard treatment for wAMD, while it is still subject to several limitations, including the safety concerns of monthly intravitreal administration and insufficient efficacy for neovascular occlusion. Combined therapy with photodynamic therapy (PDT) and anti-angiogenic agents has emerged as a novel treatment paradigm. Herein, a novel and less-invasive approach is reported to achieve anti-angiogenic and photodynamic combination therapy of wAMD by intravenous administration of a photoactivatable nanosystem (Di-DAS-VER NPs). The nanosystem is self-assembled by reactive oxygen species (ROS)-sensitive dasatinib (DAS) prodrug and photosensitizer verteporfin (VER). After red-light irradiation to the diseased eyes, intraocular release of anti-angiogenic DAS is observed, together with selective neo-vessels occlusion by VER-generated ROS. Notably, Di-DAS-VER NPs demonstrates promising therapeutic efficacy against CNV with minimized systemic toxicity. The study enables an efficient intravenous wAMD therapy by integrating a photoactivation process with combinational therapeutics into one simple nanosystem.

Biology and therapeutic targeting of vascular endothelial growth factor A

The formation of new blood vessels, called angiogenesis, is an essential pathophysiological process in which several families of regulators have been implicated. Among these, vascular endothelial growth factor A (VEGFA; also known as VEGF) and its two tyrosine kinase receptors, VEGFR1 and VEGFR2, represent a key signalling pathway mediating physiological angiogenesis and are also major therapeutic targets. VEGFA is a member of the gene family that includes VEGFB, VEGFC, VEGFD and placental growth factor (PLGF). Three decades after its initial isolation and cloning, VEGFA is arguably the most extensively investigated signalling system in angiogenesis. Although many mediators of angiogenesis have been identified, including members of the FGF family, angiopoietins, TGFβ and sphingosine 1-phosphate, all current FDA-approved anti-angiogenic drugs target the VEGF pathway. Anti-VEGF agents are widely used in oncology and, in combination with chemotherapy or immunotherapy, are now the standard of care in multiple malignancies. Anti-VEGF drugs have also revolutionized the treatment of neovascular eye disorders such as age-related macular degeneration and ischaemic retinal disorders. In this Review, we emphasize the molecular, structural and cellular basis of VEGFA action as well as recent findings illustrating unexpected interactions with other pathways and provocative reports on the role of VEGFA in regenerative medicine. We also discuss clinical and translational aspects of VEGFA. Given the crucial role that VEGFA plays in regulating angiogenesis in health and disease, this molecule is largely the focus of this Review.

Endothelial VEGFR2-PLCγ signaling regulates vascular permeability and antitumor immunity through eNOS/Src

Endothelial phospholipase Cγ (PLCγ) is essential for vascular development; however, its role in healthy, mature, or pathological vessels is unexplored. Here, we show that PLCγ was prominently expressed in vessels of several human cancer forms, notably in renal cell carcinoma (RCC). High PLCγ expression in clear cell RCC correlated with angiogenic activity and poor prognosis, while low expression correlated with immune cell activation. PLCγ was induced downstream of vascular endothelial growth factor receptor 2 (VEGFR2) phosphosite Y1173 (pY1173). Heterozygous Vegfr2Y1173F/+ mice or mice lacking endothelial PLCγ (Plcg1iECKO) exhibited a stabilized endothelial barrier and diminished vascular leakage. Barrier stabilization was accompanied by decreased expression of immunosuppressive cytokines, reduced infiltration of B cells, helper T cells and regulatory T cells, and improved response to chemo- and immunotherapy. Mechanistically, pY1173/PLCγ signaling induced Ca2+/protein kinase C-dependent activation of endothelial nitric oxide synthase (eNOS), required for tyrosine nitration and activation of Src. Src-induced phosphorylation of VE-cadherin at Y685 was accompanied by disintegration of endothelial junctions. This pY1173/PLCγ/eNOS/Src pathway was detected in both healthy and tumor vessels in Vegfr2Y1173F/+ mice, which displayed decreased activation of PLCγ and eNOS and suppressed vascular leakage. Thus, we believe that we have identified a clinically relevant endothelial PLCγ pathway downstream of VEGFR2 pY1173, which destabilizes the endothelial barrier and results in loss of antitumor immunity.

Stroke-induced damage on the blood-brain barrier

The blood-brain barrier (BBB) is a functional phenotype exhibited by the neurovascular unit (NVU). It is maintained and regulated by the interaction between cellular and non-cellular matrix components of the NVU. The BBB plays a vital role in maintaining the dynamic stability of the intracerebral microenvironment as a barrier layer at the critical interface between the blood and neural tissues. The large contact area (approximately 20 m2/1.3 kg brain) and short diffusion distance between neurons and capillaries allow endothelial cells to dominate the regulatory role. The NVU is a structural component of the BBB. Individual cells and components of the NVU work together to maintain BBB stability. One of the hallmarks of acute ischemic stroke is the disruption of the BBB, including impaired function of the tight junction and other molecules, as well as increased BBB permeability, leading to brain edema and a range of clinical symptoms. This review summarizes the cellular composition of the BBB and describes the protein composition of the barrier functional junction complex and the mechanisms regulating acute ischemic stroke-induced BBB disruption.

Edema and lymphatic clearance: molecular mechanisms and ongoing challenges

Resolution of edema remains a significant clinical challenge. Conditions such as traumatic shock, sepsis, or diabetes often involve microvascular hyperpermeability, which leads to tissue and organ dysfunction. Lymphatic insufficiency due to genetic causes, surgical removal of lymph nodes, or infections, leads to varying degrees of tissue swelling that impair mobility and immune defenses. Treatment options are limited to management of edema as there are no specific therapeutics that have demonstrated significant success for ameliorating microvascular leakage or impaired lymphatic function. This review examines current knowledge about the physiological, cellular, and molecular mechanisms that control microvascular permeability and lymphatic clearance, the respective processes for interstitial fluid formation and removal. Clinical conditions featuring edema, along with potential future directions are discussed.

Cellular and molecular mechanisms in vascular repair after traumatic brain injury: a narrative review

Traumatic brain injury (TBI) disrupts normal brain function and is associated with high morbidity and fatality rates. TBI is characterized as mild, moderate or severe depending on its severity. The damage may be transient and limited to the dura matter, with only subtle changes in cerebral parenchyma, or life-threatening with obvious focal contusions, hematomas and edema. Blood vessels are often injured in TBI. Even in mild TBI, dysfunctional cerebral vascular repair may result in prolonged symptoms and poor outcomes. Various distinct types of cells participate in vascular repair after TBI. A better understanding of the cellular response and function in vascular repair can facilitate the development of new therapeutic strategies. In this review, we analyzed the mechanism of cerebrovascular impairment and the repercussions following various forms of TBI. We then discussed the role of distinct cell types in the repair of meningeal and parenchyma vasculature following TBI, including endothelial cells, endothelial progenitor cells, pericytes, glial cells (astrocytes and microglia), neurons, myeloid cells (macrophages and monocytes) and meningeal lymphatic endothelial cells. Finally, possible treatment techniques targeting these unique cell types for vascular repair after TBI are discussed.

Nintedanib administration after the onset of acute exacerbation of interstitial lung disease in the real world

Nintedanib reduces the decline in forced vital capacity and extends the time to the first acute exacerbation of interstitial lung disease (AE-ILD). However, the effect of additional nintedanib administration after AE-ILD onset is unknown. This study aimed to investigate the efficacy and safety of nintedanib administration after AE-ILD development. We retrospectively collected the data of 33 patients who developed AE-ILD between April 2014 and January 2022. Eleven patients who received nintedanib after AE-ILD development and the remaining who did not were classified into the N and No-N groups, respectively. The survival time in the N group tended to be longer than that in the No-N group. The generalized Wilcoxson test revealed that the cumulative mortality at 90 days from AE-ILD onset was significantly lower in the N group. The time to subsequent AE-ILD development was significantly longer in the N group than that in the No-N group. The incidence of adverse gastrointestinal effects and liver dysfunction in the N group was 9-18%. Treatment without nintedanib after AE-ILD development and the ratio of arterial oxygen partial pressure to fractional inspired oxygen were significant independent prognostic factors in the multivariate analysis. Thus, nintedanib administration may be a treatment option for AE-ILD.

Monocyte-endothelial cell interactions in vascular and tissue remodeling

Monocytes are circulating leukocytes of innate immunity derived from the bone marrow that interact with endothelial cells under physiological or pathophysiological conditions to orchestrate inflammation, angiogenesis, or tissue remodeling. Monocytes are attracted by chemokines and specific receptors to precise areas in vessels or tissues and transdifferentiate into macrophages with tissue damage or infection. Adherent monocytes and infiltrated monocyte-derived macrophages locally release a myriad of cytokines, vasoactive agents, matrix metalloproteinases, and growth factors to induce vascular and tissue remodeling or for propagation of inflammatory responses. Infiltrated macrophages cooperate with tissue-resident macrophages during all the phases of tissue injury, repair, and regeneration. Substances released by infiltrated and resident macrophages serve not only to coordinate vessel and tissue growth but cellular interactions as well by attracting more circulating monocytes (e.g. MCP-1) and stimulating nearby endothelial cells (e.g. TNF-α) to expose monocyte adhesion molecules. Prolonged tissue accumulation and activation of infiltrated monocytes may result in alterations in extracellular matrix turnover, tissue functions, and vascular leakage. In this review, we highlight the link between interactions of infiltrating monocytes and endothelial cells to regulate vascular and tissue remodeling with a special focus on how these interactions contribute to pathophysiological conditions such as cardiovascular and chronic liver diseases.

Effects of isoflurane and xylazine on inducing cerebral ischemia by the model of middle cerebral artery occlusion in mice

Preclinical ischemic stroke studies extensively utilize the intraluminal suture method of middle cerebral artery occlusion (MCAo). General anesthesia administration is an essential step for MCAo, but anesthetic agents can lead to adverse effects causing death and making a considerable impact on inducing cerebral ischemia. The purpose of this study was to comparatively assess the effect of isoflurane and xylazine on transient cerebral ischemia in a mouse model of MCAo. Twenty animals were randomly divided into four groups: sham group (no MCAo), control group (MCAo under isoflurane, no agent till reperfusion), isoflurane group (MCAo under isoflurane continued till reperfusion), xylazine group (MCAo under isoflurane, and administration of xylazine till reperfusion). The survival rate, brain infarct volume, and neurologic deficits were studied to assess the effect of isoflurane and xylazine on the stroke model. Our results showed that the body weight showed statistically significant change before and 24 h after surgery in the control and Isoflurane groups, but no difference in the Xylazine group. Also, the survival rate, brain infarct volume, and neurologic deficits were slightly reduced in the isoflurane group at 24 h after reperfusion injury. However, the xylazine and control groups showed similar BIV and neurologic deficits. Interestingly, a high survival rate was observed in the xylazine group. Our results indicate that the modified method of inhalation anesthetics combined with xylazine can reduce the risk of mortality and develop a reproducible MCAo model with predictable brain ischemia. In addition, extended isoflurane anesthesia after MCAo is associated with the risk of mortality.

Research progress of VEGFR small molecule inhibitors in ocular neovascular diseases

Angiogenesis is the biological process in which existing blood vessels generate new ones and it is essential for body growth and development, wound healing, and granulation tissue formation. Vascular endothelial growth factor receptor (VEGFR) is a crucial cell membrane receptor that binds to VEGF to regulate angiogenesis and maintenance. Dysregulation of VEGFR signaling can lead to several diseases, such as cancer and ocular neovascular disease, making it a crucial research area for disease treatment. Currently, anti-VEGF drugs commonly used in ophthalmology are mainly four macromolecular drugs, Bevacizumab, Ranibizumab, Conbercept and Aflibercept. Although these drugs are relatively effective in treating ocular neovascular diseases, their macromolecular properties, strong hydrophilicity, and poor blood-eye barrier penetration limit their efficacy. However, VEGFR small molecule inhibitors possess high cell permeability and selectivity, allowing them to traverse and bind to VEGF-A specifically. Consequently, they have a shorter duration of action on the target, and they offer significant therapeutic benefits to patients in the short term. Consequently, there is a need to develop small molecule inhibitors of VEGFR to target ocular neovascularization diseases. This review summarizes the recent developments in potential VEGFR small molecule inhibitors for the targeted treatment of ocular neovascularization diseases, with the aim of providing insights for future studies on VEGFR small molecule inhibitors.

Adipsin alleviates cardiac microvascular injury in diabetic cardiomyopathy through Csk-dependent signaling mechanism

BACKGROUND

Microvascular complications are associated with an overtly increased risk of adverse outcomes in patients with diabetes including coronary microvascular injury which manifested as disruption of adherens junctions between cardiac microvascular endothelial cells (CMECs). However, particular mechanism leading to diabetic coronary microvascular hyperpermeability remains elusive.

METHODS

Experimental diabetes was induced in mice with adipose tissue-specific Adipsin overexpression (Adipsin^LSL/LSL-Cre) and their respective control (Adipsin^LSL/LSL). In addition, cultured CMECs were subjected to high glucose/palmitic acid (HG + PA) treatment to simulate diabetes for a mechanistic approach.

RESULTS

The results showed that Adipsin overexpression significantly reduced cardiac microvascular permeability, preserved coronary microvascular integrity, and increased coronary microvascular density. Adipsin overexpression also attenuated cardiac dysfunction in diabetic mice. E/A ratio, an indicator of cardiac diastolic function, was improved by Adipsin. Adipsin overexpression retarded left ventricular adverse remodeling, enhanced LVEF, and improved cardiac systolic function. Adipsin-enriched exosomes were taken up by CMECs, inhibited CMECs apoptosis, and increased CMECs proliferation under HG + PA treatment. Adipsin-enriched exosomes also accelerated wound healing, rescued cell migration defects, and promoted tube formation in response to HG + PA challenge. Furthermore, Adipsin-enriched exosomes maintained adherens junctions at endothelial cell borders and reversed endothelial hyperpermeability disrupted by HG + PA insult. Mechanistically, Adipsin blocked HG + PA-induced Src phosphorylation (Tyr416), VE-cadherin phosphorylation (Tyr685 and Tyr731), and VE-cadherin internalization, thus maintaining CMECs adherens junctions integrity. LC-MS/MS analysis and co-immunoprecipitation analysis (Co-IP) unveiled Csk as a direct downstream regulator of Adipsin. Csk knockdown increased Src phosphorylation (Tyr416) and VE-cadherin phosphorylation (Tyr685 and Tyr731), while abolishing Adipsin-induced inhibition of VE-cadherin internalization. Furthermore, Csk knockdown counteracted Adipsin-induced protective effects on endothelial hyperpermeability in vitro and endothelial barrier integrity of coronary microvessels in vivo.

CONCLUSIONS

Together, these findings favor the vital role of Adipsin in the regulation of CMECs adherens junctions integrity, revealing its promises as a treatment target against diabetic coronary microvascular dysfunction. Graphical abstract depicting the mechanisms of action behind Adipsin-induced regulation of diabetic coronary microvascular dysfunction.

Functional roles of SRC signaling in pancreatic cancer: Recent insights provide novel therapeutic opportunities

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignant disease with a 5-year survival rate of <10%. Aberrant activation or elevated expression of the tyrosine kinase c-SRC (SRC) is frequently observed in PDAC and is associated with a poor prognosis. Preclinical studies have revealed a multifaceted role for SRC activation in PDAC, including promoting chronic inflammation, tumor cell proliferation and survival, cancer cell stemness, desmoplasia, hypoxia, angiogenesis, invasion, metastasis, and drug resistance. Strategies to inhibit SRC signaling include suppressing its catalytic activity, inhibiting protein stability, or by interfering with signaling components of the SRC signaling pathway including suppressing protein interactions of SRC. In this review, we discuss the molecular and immunological mechanisms by which aberrant SRC activity promotes PDAC tumorigenesis. We also provide a comprehensive update of SRC inhibitors in the clinic, and discuss the clinical challenges associated with targeting SRC in pancreatic cancer.

Targeting VEGF-A/VEGFR2 Y949 Signaling-Mediated Vascular Permeability Alleviates Hypoxic Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is associated with increased expression of VEGF-A (vascular endothelial growth factor A) and its receptor, VEGFR2 (vascular endothelial growth factor 2), but whether and how activation of VEGF-A signal participates in the pathogenesis of PH is unclear.

METHODS

VEGF-A/VEGFR2 signal activation and VEGFR2 Y949-dependent vascular leak were investigated in lung samples from patients with PH and mice exposed to hypoxia. To study their mechanistic roles in hypoxic PH, we examined right ventricle systolic pressure, right ventricular hypertrophy, and pulmonary vasculopathy in mutant mice carrying knock-in of phenylalanine that replaced the tyrosine at residual 949 of VEGFR2 (Vefgr2^Y949F) and mice with conditional endothelial deletion of Vegfr2 after chronic hypoxia exposure.

RESULTS

We show that PH leads to excessive pulmonary vascular leak in both patients and hypoxic mice, and this is because of an overactivated VEGF-A/VEGFR2 Y949 signaling axis. In the context of hypoxic PH, activation of Yes1 and c-Src and subsequent VE-cadherin phosphorylation in endothelial cells are involved in VEGFR2 Y949-induced vascular permeability. Abolishing VEGFR2 Y949 signaling by Vefgr2^Y949F point mutation was sufficient to prevent pulmonary vascular permeability and inhibit macrophage infiltration and Rac1 activation in smooth muscle cells under hypoxia exposure, thereby leading to alleviated PH manifestations, including muscularization of distal pulmonary arterioles, elevated right ventricle systolic pressure, and right ventricular hypertrophy. It is important that we found that VEGFR2 Y949 signaling in myeloid cells including macrophages was trivial and dispensable for hypoxia-induced vascular abnormalities and PH. In contrast with selective blockage of VEGFR2 Y949 signaling, disruption of the entire VEGFR2 signaling by conditional endothelial deletion of Vegfr2 promotes the development of PH.

CONCLUSIONS

Our results support the notion that VEGF-A/VEGFR2 Y949-dependent vascular permeability is an important determinant in the pathogenesis of PH and might serve as an attractive therapeutic target pathway for this disease.

Tyrosine-protein kinase Yes controls endothelial junctional plasticity and barrier integrity by regulating VE-cadherin phosphorylation and endocytosis

Vascular endothelial (VE)-cadherin in endothelial adherens junctions is an essential component of the vascular barrier, critical for tissue homeostasis and implicated in diseases such as cancer and retinopathies. Inhibitors of Src cytoplasmic tyrosine kinase have been applied to suppress VE-cadherin tyrosine phosphorylation and prevent excessive leakage, edema and high interstitial pressure. Here we show that the Src-related Yes tyrosine kinase, rather than Src, is localized at endothelial cell (EC) junctions where it becomes activated in a flow-dependent manner. EC-specific Yes1 deletion suppresses VE-cadherin phosphorylation and arrests VE-cadherin at EC junctions. This is accompanied by loss of EC collective migration and exaggerated agonist-induced macromolecular leakage. Overexpression of Yes1 causes ectopic VE-cadherin phosphorylation, while vascular leakage is unaffected. In contrast, in EC-specific Src-deficiency, VE-cadherin internalization is maintained, and leakage is suppressed. In conclusion, Yes-mediated phosphorylation regulates constitutive VE-cadherin turnover, thereby maintaining endothelial junction plasticity and vascular integrity.

Mechanical regulation of the early stages of angiogenesis

Favouring or thwarting the development of a vascular network is essential in fields as diverse as oncology, cardiovascular disease or tissue engineering. As a result, understanding and controlling angiogenesis has become a major scientific challenge. Mechanical factors play a fundamental role in angiogenesis and can potentially be exploited for optimizing the architecture of the resulting vascular network. Largely focusing on in vitro systems but also supported by some in vivo evidence, the aim of this Highlight Review is dual. First, we describe the current knowledge with particular focus on the effects of fluid and solid mechanical stimuli on the early stages of the angiogenic process, most notably the destabilization of existing vessels and the initiation and elongation of new vessels. Second, we explore inherent difficulties in the field and propose future perspectives on the use of in vitro and physics-based modelling to overcome these difficulties.

Hypoxia‐induced ELF3 promotes tumor angiogenesis through IGF1/IGF1R

Epithelial ovarian cancer (EOC) is one of the most lethal gynecological cancers despite a relatively low incidence. Angiogenesis, one of the hallmarks of cancer, is essential for the pathogenesis of EOC, which is related to the induction of angiogenic factors. We found that ELF3 was highly expressed in EOCs under hypoxia and functioned as a transcription factor for IGF1. The ELF3‐mediated increase in the secretion of IGF1 and VEGF promoted endothelial cell proliferation, migration, and EOC angiogenesis. Although this situation was much exaggerated under hypoxia, ELF3 silencing under hypoxia significantly attenuated angiogenic activity in endothelial cells by reducing the expression and secretion of IGF1 and VEGF. ELF3 silencing attenuated angiogenesis and tumorigenesis in ex vivo and xenograft mouse models. Consequently, ELF3 plays an important role in the induction of angiogenesis and tumorigenesis in EOC as a transcription factor of IGF1. A detailed understanding of the biological mechanism of ELF3 may both improve current antiangiogenic therapies and have anticancer effects for EOC.

PRMT4-mediated arginine methylation promotes tyrosine phosphorylation of VEGFR-2 and regulates filopodia protrusions

Through tightly controlled multilayer mechanisms, vascular endothelial growth factor receptor-2 (VEGFR-2) activation and its downstream signal transduction govern vasculogenesis and pathological angiogenesis, such as tumor angiogenesis. Therefore, it is critical to understand the molecular mechanisms governing VEGFR-2 signal transduction. We report that protein arginine methyltransferase 4 (PRMT4) via its highly conserved EVH1 and PH domain-like N-terminal domain binds to VEGFR-2 and mediates methylation of the juxtamembrane arginine 817 (R817) on VEGFR-2. Methylation of R817 selectively increases phosphorylation of tyrosine 820 (Y820). Phosphorylation of Y820 facilitates the c-Src binding with VEGFR-2 via Src homology domain 2 (SH2). Interfering with the methylation of R817 or phosphorylation of Y820 inhibits VEGFR-2-induced filopodia protrusions, a process that is critical for the core angiogenic responses of VEGFR-2. Methylation of R817 is an important previously unrecognized mechanism of the angiogenic signaling of VEGFR-2, with implications for the development of novel-targeted VEGFR-2 inhibitors.

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Arginine 817 methylation regulates phosphorylation of Y820 on VEGFR-2

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Phosphorylation of Y820 recruits c-Src kinase to VEGFR-2, leading to its activation

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VEGFR-2/c-Src axis mediates filopodia protrusions in endothelial cells

Claudin5 protects the peripheral endothelial barrier in an organ and vessel type-specific manner

Dysfunctional and leaky blood vessels resulting from disruption of the endothelial cell (EC) barrier accompanies numerous diseases. The EC barrier is established through endothelial cell tight and adherens junctions. However, the expression pattern and precise contribution of different junctional proteins to the EC barrier is poorly understood. Here, we focus on organs with continuous endothelium to identify structural and functional in vivo characteristics of the EC barrier. Assembly of multiple single-cell RNAseq datasets into a single integrated database revealed the variability and commonalities of EC barrier patterning. Across tissues, Claudin5 exhibited diminishing expression along the arteriovenous axis, correlating with EC barrier integrity. Functional analysis identified tissue-specific differences in leakage properties and response to the leakage agonist histamine. Loss of Claudin5 enhanced histamine-induced leakage in an organotypic and vessel type-specific manner in an inducible, EC-specific, knock-out mouse. Mechanistically, Claudin5 loss left junction ultrastructure unaffected but altered its composition, with concomitant loss of zonula occludens-1 and upregulation of VE-Cadherin expression. These findings uncover the organ-specific organisation of the EC barrier and distinct importance of Claudin5 in different vascular beds, providing insights to modify EC barrier stability in a targeted, organ-specific manner.

YES1: a novel therapeutic target and biomarker in cancer

YES1 is a non-receptor tyrosine kinase that belongs to the SRC family of kinases (SFKs) and controls multiple cancer signaling pathways. YES1 is amplified and overexpressed in many tumor types, where it promotes cell proliferation, survival and invasiveness. Therefore, YES1 has been proposed as an emerging target in solid tumors. In addition, studies have shown that YES1 is a prognostic biomarker and a predictor of dasatinib activity. Several SFKs-targeting drugs have been developed and some of them have reached clinical trials. However, these drugs have encountered challenges to their utilization in the clinical practice in unselected patients due to toxicity and lack of efficacy. In the case of YES1, novel specific inhibitors have been developed and tested in preclinical models, with impressive antitumor effects. In this review, we summarize the structure and activation of YES1 and describe its role in cancer as a target and prognostic and companion biomarker. We also address the efficacy of SFKs inhibitors that are currently in clinical trials, highlighting the main hindrances for their clinical use. Current available information strongly suggests that inhibiting YES1 in tumors with high expression of this protein is a promising strategy against cancer.

Syndecan-2 selectively regulates VEGF-induced vascular permeability

Vascular endothelial growth factor (VEGF)- driven increase in vascular permeability is a key feature of many disease states associated with inflammation and ischemic injury, contributing significantly to morbidity and mortality in these settings. Despite its importance, no specific regulators that preferentially control VEGF-dependent increase in permeability versus its other biological activities, have been identified. Here we report that a proteoglycan Syndecan-2 (Sdc2) regulates the interaction between a transmembrane phosphatase DEP1 and VEGFR2 by controlling cell surface levels of DEP1. In the absence of Sdc2 or the presence of an antibody that blocks Sdc2-DEP1 interaction, increased plasma membrane DEP1 levels promote selective dephosphorylation of the VEGFR2 Y951 site that is involved in permeability control. Either an endothelial-specific Sdc2 deletion or a treatment with an anti-Sdc2 antibody result in a highly significant reduction in stroke size due to a decrease in intracerebral edema.

Ethoxy-erianin phosphate and afatinib synergistically inhibit liver tumor growth and angiogenesis via regulating VEGF and EGFR signaling pathways

The therapeutic efficacy of tyrosine kinase inhibitors (TKIs) on solid tumors is limited by drug resistance and side effects. Currently, the combination therapy comprises of TKIs and angiogenesis inhibitors have been corroborated as an effective approach in cancer therapy. Ethoxy-erianin phosphate (EBTP) is an anti-angiogenic compound with low toxicity obtained by structural modification of the natural product erianin. Here, we aimed to evaluate whether EBTP can cooperate with TKIs to inhibit the proliferation and angiogenesis of tumor cells and reduce toxic effects. First, CCK-8 results showed that EBTP can effectively inhibit the proliferation of liver cancer cell line HepG2. We combined EBTP with four TKIs (Bosutinib, Apatinib, Afatinib and Erlotinib) to treat HepG2 cells and CompuSyn software analysis suggested that EBTP/Afatinib(Afa)shows the best synergistic inhibitory effect. Meanwhile, EBTP/Afa can significantly suppress the proliferation, invasion, migration and angiogenesis of HepG2 and HUVECs. ELISA results revealed that EBTP/Afa inhibits the secretion of VEGF in HepG2. EBTP/Afa down-regulates the expression of VEGF, p-VEGFR1, p-VEGFR2 and p-EGFR in both HepG2 and HUVECs. Further, the supernatant of HepG2 cells treated with EBTP/Afa blocks the intracellular downstream signal transduction shared by VEGF and EGFR in HUVECs. Finally, EBTP/Afa significantly inhibits tumor growth and angiogenesis in vivo. To conclude, EBTP/Afa targets VEGF and EGFR signaling pathways in liver cancer cells and tumor vasculature, thereby inhibiting the proliferation, motion and angiogenesis of liver cancer cells. Overall, this study provides a new combined strategy for the clinical treatment of hepatocellular carcinoma.

Targeting tumor microenvironment and metastasis in children with solid tumors

PURPOSE OF REVIEW

The prognosis of pediatric patients with metastatic solid tumors remains poor, necessitating development of novel therapeutic strategies. The biology of the pediatric tumor microenvironment (TME) presents obstacles for the efficacy of current therapeutic approaches including immunotherapies. Targeting various aspects of the TME in pediatric patients with solid tumors represents a therapeutic opportunity that may improve outcomes. Here we will discuss recent advances in characterization of the TME, and clinical advances in targeting the immune, vascular, and stromal aspects of the TME.

RECENT FINDINGS

Although immunotherapies have shown limited success in the treatment of pediatric solid tumor patients thus far, optimization of these approaches to overcome the TME shows promise. In addition, there is increasing focus on the myeloid compartment as a therapeutic target. Vascular endothelial growth factor (VEGF) targeting has resulted in responses in some refractory pediatric solid tumors. There has been relatively little focus on stromal targeting; however, emerging preclinical data are improving our understanding of underlying biology, paving the way for future therapies.

SUMMARY

Although translation of TME-targeting therapies for pediatric solid tumors is in the early stages, we are optimistic that continued exploration of approaches aimed at rebalancing the TME will lead to improved outcomes for this population.

Evaluating VEGF-Induced Vascular Leakage Using the Miles Assay

Before the endothelial mitogenic activity of the Vascular Endothelial Growth Factor A (VEGF) was described, VEGF had already been identified for its ability to induce vascular leakage. VEGF-induced vascular leakage has been most frequently studied in vivo using the Miles assay, a simple yet invaluable technique that has allowed researchers to unravel the molecular mechanisms underpinning vascular leakage both for VEGF and other permeability inducing agents. In this protocol, a mouse is intravenously injected with Evans Blue dye before VEGF is administered locally via intradermal injection. VEGF promotes vascular leak of serum proteins in the dermis, enabling Evans Blue-labeled albumin extravasation from the circulation and subsequent accumulation in the skin. As the volume of dye extravasation is proportional to the degree of vascular leak, it can be quantified as a proxy measurement of VEGF-induced vascular leakage.

Assessing Molecular Regulation of Vascular Permeability Using a VEGF-Inducible Zebrafish Model

Vascular endothelial growth factor (VEGF) stimulates vascular permeability in a variety of human pathologies, such as cancer, ischemic stroke, cardiovascular disease, retinal conditions, and COVID-19-associated pulmonary edema, sepsis, acute lung injury, and acute respiratory distress syndrome. Comprehensive investigation of the molecular mechanisms of VEGF-induced vascular permeability has been hindered by the lack of in vivo models that easily facilitate genetic manipulation studies in real time. To address this need, we generated a heat-inducible VEGF transgenic zebrafish model of vascular permeability. Here, we describe how this zebrafish model can be used to monitor VEGF-induced vascular permeability through live in vivo imaging to identify genetic regulators that play key roles in vascular barrier integrity in physiological conditions and human disease processes.

2,3-Difunctionalized Benzo[b]thiophene Scaffolds Possessing Potent Antiangiogenic Properties

A new class of 2-anilino-3-cyanobenzo[b]thiophenes (2,3-ACBTs) was studied for its antiangiogenic activity for the first time. One of the 2,3-ACBTs inhibited tubulogenesis in a dose-dependent manner without any toxicity. The 2,3-ACBTs significantly reduced neovascularization in both ex vivo and in vivo angiogenic assays without affecting the proliferation of endothelial cells. Neovascularization was limited through reduced phosphorylation of Akt/Src and depolymerization of f-actin and β-tubulin filaments, resulting in reduced migration of cells. In addition, the 2,3-ACBT compound disrupted the preformed angiogenic tubules, and docking/competitive binding studies showed that it binds to VEGFR2. Compound 2,3-ACBT had good stability and intramuscular profile, translating in suppressing the tumor angiogenesis induced in a xenograft model. Overall, the present study suggests that 2,3-ACBT arrests angiogenesis by regulating the Akt/Src signaling pathway and deranging cytoskeletal filaments of endothelial cells.

Novel engineered, membrane-tethered VEGF-A variants promote formation of filopodia, proliferation, survival, and cord or tube formation by endothelial cells via persistent VEGFR2/ERK signaling and activation of CDC42/ROCK pathways

Therapeutic angiogenesis would be clinically valuable in situations such as peripheral vascular disease in diabetic patients and tissue reperfusion following ischemia or injury, but approaches using traditional isoforms of vascular endothelial growth factor-A (VEGF) have had little success. The isoform VEGF165 is both soluble and matrix-associated, but can cause pathologic vascular changes. Freely diffusible VEGF121 is not associated with pathologic angiogenesis, but its failure to remain in the vicinity of the targeted area presents therapeutic challenges. In this study, we evaluate the cellular effects of engineered VEGF variants that tether extracellular VEGF121 to the cell membrane with the goal of activating VEGF receptor 2 (VEGFR2) in a sustained, autologous fashion in endothelial cells. When expressed by primary human retinal endothelial cells (hRECs), the engineered, membrane-tethered variants eVEGF-38 and eVEGF-53 provide a lasting VEGF signal that induces cell proliferation and survival, increases endothelial permeability, promotes the formation of a cord/tube network, and stimulates the formation of elongated filopodia on the endothelial cells. The engineered VEGF variants activate VEGFR2, MAPK/ERK, and the Rho GTPase mediators CDC42 and ROCK, activities that are required for the formation of the elongated filopodia. The sustained, pro-angiogenic activities induced by eVEGF-38 and eVEGF-53 support the potential of engineered VEGF variants-overexpressing endothelial cells as a novel combination of gene and cell-based therapeutic strategy for stimulating endothelial cell-autologous therapeutic angiogenesis.

Cell Therapy of Stroke: Do the Intra-Arterially Transplanted Mesenchymal Stem Cells Cross the Blood-Brain Barrier?

Animal model studies and first clinical trials have demonstrated the safety and efficacy of the mesenchymal stem cells' (MSCs) transplantation in stroke. Intra-arterial (IA) administration looks especially promising, since it provides targeted cell delivery to the ischemic brain, is highly effective, and can be safe as long as the infusion is conducted appropriately. However, wider clinical application of the IA MSCs transplantation will only be possible after a better understanding of the mechanism of their therapeutic action is achieved. On the way to achieve this goal, the study of transplanted cells' fate and their interactions with the blood-brain barrier (BBB) structures could be one of the key factors. In this review, we analyze the available data concerning one of the most important aspects of the transplanted MSCs' action-the ability of cells to cross the blood-brain barrier (BBB) in vitro and in vivo after IA administration into animals with experimental stroke. The collected data show that some of the transplanted MSCs temporarily attach to the walls of the cerebral vessels and then return to the bloodstream or penetrate the BBB and either undergo homing in the perivascular space or penetrate deeper into the parenchyma. Transmigration across the BBB is not necessary for the induction of therapeutic effects, which can be incited through a paracrine mechanism even by cells located inside the blood vessels.

Genetic deletion of endothelial microRNA-15a/16-1 promotes cerebral angiogenesis and neurological recovery in ischemic stroke through Src signaling pathway

Cerebral angiogenesis is tightly controlled by specific microRNAs (miRs), including the miR-15a/16-1 cluster. Recently, we reported that endothelium-specific conditional knockout of the miR-15a/16-1 cluster (EC-miR-15a/16-1 cKO) promotes post-stroke angiogenesis and improves long-term neurological recovery by increasing protein levels of VEGFA, FGF2, and their respective receptors VEGFR2 and FGFR1. Herein, we further investigated the underlying signaling mechanism of these pro-angiogenic factors after ischemic stroke using a selective Src family inhibitor AZD0530. EC-miR-15a/16-1 cKO and age- and sex-matched wild-type littermate (WT) mice were subjected to 1 h middle cerebral artery occlusion (MCAO) and 28d reperfusion. AZD0530 was administered daily by oral gavage to both genotypes of mice 3-21d after MCAO. Compared to WT, AZD0530 administration exacerbated spatial cognitive impairments and brain atrophy in EC-miR-15a/16-1 cKO mice following MCAO. AZD0530 also attenuated long-term recovery of blood flow and inhibited the formation of new microvessels, including functional vessels with blood circulation, in the penumbra of stroked cKO mice. Moreover, AZD0530 blocked the Src signaling pathway by downregulating phospho-Src and its downstream mediators (p-Stat3, p-Akt, p-FAK, p-p44/42 MAPK, p-p38 MAPK) in post-ischemic brains. Collectively, our data demonstrated that endothelium-targeted deletion of the miR-15a/16-1 cluster promotes post-stroke angiogenesis and improves long-term neurological recovery via activating Src signaling pathway.

Evaluation of Signaling Pathways Profiling in Human Dermal Endothelial Cells Treated by Snake Venom Cysteine-Rich Secretory Proteins (svCRiSPs) from North American Snakes Using Reverse Phase Protein Array (RPPA)

Cysteine-Rich Secretory Proteins (CRiSPs) are typically found in many snake venoms; however, the role that these toxins play in the pathophysiology of snakebites is still unclear. Herein, we compared the effects of snake venom CRiSPs (svCRiSPs) from the most medically important species of North American snakes on endothelial cell permeability and vascular permeability. We used reverse phase protein array (RPPA) to identify key signaling molecules on human dermal lymphatic (HDLECs) and blood (HDBECs) endothelial cells treated with svCRiSPs. The results showed that Css-CRiSP isolated from Crotalus scutulatus scutulatus and App-CRiSP from Agkistrodon piscivorus piscivorus are the most potent causes of increase vascular and endothelial permeability in comparison with other svCRiSPs used in this study. We examined the protein expression levels and their activated phosphorylation states in HDLECs and HDBECs induced by App-CRiSP and Css-CRiSP using RPPA. Interestingly, both App-CRiSP and Css-CRiSP induced caveolin-1 expression in HDBECs. We also found that stimulating HDBECs with Css-CRiSP and App-CRiSP significantly induced the phosphorylation of mTOR and Src, respectively. In HDLECs, Css-CRiSP significantly downregulated the expression of N-Cadherin and phospholipase C-gamma, while App-CRiSP significantly enhanced Akt and JNK phosphorylation. These results suggest that the increased endothelial permeability in HDLECs and HDBECs by Css-CRiSP and App-CRiSP may occur through different pathways.

Effects of Dual Purinoceptor-dependent Approach on Release of Vascular Endothelial Growth Factor From Human Microvascular Endothelial Cell (HMEC-1) and Endothelial Cell Condition

In the recent years, the awareness of the role purinergic signaling plays as a therapeutic target has increased considerably. The purinoceptor allows the action of extracellular nucleotides (P2 receptors) and intermediary products of their metabolism, such as adenosine (P1 receptors), regulating pivotal processes occurring in the cardiovascular system. This study focuses on a dual purinoreceptor-dependent approach, based on the activation of adenosine P1 receptors with the simultaneous inhibition of P2Y12 receptors that can be used as novel platelet inhibitors in antithrombotic therapy. Endothelial cells are directly exposed to the drugs circulating in the bloodstream. That is why effects of our concept on human microvascular endothelial cells (HMEC-1) were examined in in vitro studies, such as enzyme-linked immunosorbent assay and scratch assays. In response to adenosine receptor agonists, levels of secreted vascular endothelial growth factor varied. Two of them, 5'-N-ethylcarboxamidoadenosine and MRE0094 remarkably increased vascular endothelial growth factor release. The elevated levels were reduced when used together with the P2Y12 receptor antagonist. Also, rates of wound closure in a scratch assay were significantly reduced in these cases. The results suggest that the proposed treatment does not impair endothelial cell condition. In addition, it is suggested as a collateral benefit, namely solving the problem of excessive activation of endothelial cells during antiplatelet therapy.

Intra-vessel heterogeneity establishes enhanced sites of macromolecular leakage downstream of laminin α5

Endothelial cells display heterogeneous properties based on location and function. How this heterogeneity influences endothelial barrier stability both between and within vessel subtypes is unexplored. In this study, we find that endothelial cells exhibit heterogeneous barrier properties on inter-organ and intra-vessel levels. Using intravital microscopy and sequential stimulation of the ear dermis with vascular endothelial growth factor-A (VEGFA) and/or histamine, we observe distinct, reappearing sites, common for both agonists, where leakage preferentially takes place. Through repetitive stimulation of the diaphragm and trachea, we find inter-organ conservation of such predetermined leakage sites. Qualitatively, predetermined sites display distinct leakage properties and enhanced barrier breakdown compared to less susceptible regions. Mechanistically, laminin α5 is reduced at predetermined sites, which is linked to reduced junctional vascular endothelial (VE)-cadherin and enhanced VEGFA-induced VE-cadherin phosphorylation. These data highlight functional intra-vessel heterogeneity that defines predetermined sites with distinct leakage properties and that may disproportionately impact pathological vascular leakage.

Circulating lncRNAs HIF1A-AS2 and LINLK-A: Role and Relation to Hypoxia-Inducible Factor-1α in Cerebral Stroke Patients

Long noncoding RNAs (lncRNAs) have been recently recognized as key players of gene expression in cerebral pathogenesis. Thus, their potential use in stroke diagnosis, prognosis, and therapy is actively pursued. Due to the complexity of the disease, identifying stroke-specific lncRNAs remains a challenge. This study investigated the expression of lncRNAs HIF1A-AS2 and LINK-A, and their target gene hypoxia-inducible factor-1 (HIF-1) in Egyptian stroke patients. It also aimed to determine the molecular mechanism implicated in the disease. A total of 75 stroke patients were divided into three clinical subgroups, besides 25 healthy controls of age-matched and sex-matched. Remarkable upregulation of lncRNA HIF1A-AS2 and HIF1-α along with a downregulation of lncRNA LINK-A was noticed in all stroke groups relative to controls. Serum levels of phosphatidylinositol 3-kinase (PI3K), phosphorylated-Akt (p-Akt), vascular endothelial growth factor (VEGF), and angiopoietin-1 (ANG1) as well as their receptors, malondialdehyde (MDA), and total antioxidant capacity (TAC) were significantly increased, whereas brain-derived neurotrophic factor (BDNF) levels were significantly decreased particularly in hemorrhagic stroke versus ischemic groups. Eventually, these findings support the role of lncRNAs HIF1A-AS2 and LINK-A as well as HIF1-α in activation of angiogenesis, neovascularization, and better prognosis of stroke, especially the hemorrhagic type.