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Angiogenesis, the formation of new blood vessels, is tightly regulated by gene transcriptional programs. Yin Ying 1 (YY1) is a ubiquitously distributed transcription factor with diverse and complex biological functions; however, little is known about the cell-type-specific role of YY1 in vascular development and angiogenesis. Here we report that endothelial cell (EC)-specific YY1 deletion in mice led to embryonic lethality as a result of abnormal angiogenesis and vascular defects. Tamoxifen-inducible EC-specific YY1 knockout (YY1iΔEC) mice exhibited a scarcity of retinal sprouting angiogenesis with fewer endothelial tip cells. YY1iΔEC mice also displayed severe impairment of retinal vessel maturation. In an ex vivo mouse aortic ring assay and a human EC culture system, YY1 depletion impaired endothelial sprouting and migration. Mechanistically, YY1 functions as a repressor protein of Notch signaling that controls EC tip-stalk fate determination. YY1 deficiency enhanced Notch-dependent gene expression and reduced tip cell formation. Specifically, YY1 bound to the N-terminal domain of RBPJ (recombination signal binding protein for Ig Kappa J region) and competed with the Notch coactivator MAML1 (mastermind-like protein 1) for binding to RBPJ, thereby impairing the NICD (intracellular domain of the Notch protein)/MAML1/RBPJ complex formation. Our study reveals an essential role of endothelial YY1 in controlling sprouting angiogenesis through directly interacting with RBPJ and forming a YY1-RBPJ nuclear repression complex. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor (VEGF) induces phosphorylation of VEGF receptor-2 (VEGFR-2) and activates the downstream signaling pathway resulting in endothelial cell migration, proliferation, and survival. Cigarette smoking is associated with abnormal vascular and endothelial function, leading to airspace enlargement. Herein, we investigated the mechanism of cigarette smoke (CS) -induced endothelial dysfunction by studying the VEGF-VEGFR-2 signaling in mouse lung and human endothelial cells. CS exposure caused oxidative stress, as shown by increased levels of 4-hydroxy-2-n0nenal-adducts in mouse lung and reactive oxygen species generation in human lung microvascular endothelial cells (HMVEC-Ls). Inhibition of VEGFR-2 by a specific kinase inhibitor (NVP-AAD777) enhanced the CS-induced oxidative stress, causing augmented inflammatory cell influx and proinflammatory mediators release in mouse lung. The levels of endothelial nitric oxide synthase (eNOS) and phosphorylated (p) -eNOS in the lungs of mice exposed to CS and/or treated with VEGFR-2 inhibitor were decreased. CS down-regulated VEGFR-2 expression, eNOS levels, and VEGF-induced VEGFR-2 phosphorylation in HMVEC-Ls, resulting in impaired VEGF-induced endothelial cell migration and angiogenesis. Overall, these data show that inhibition of VEGFR-2 augmented CS-induced oxidative stress and inflarmnatory responses leading to endothelial dysfunction. This explains the mechanism of endothelial dysfunction in smokers and has implications in understanding the pathogenesis of pulmonary and cardiovascular diseases.--Edirisinghe, I., Yang, S.-E., Yao, H., Rajendrasozhan, S., Caito, S., Adenuga, D., Wong, C., Rahman, A., Phipps, R. P., Jin, Z.-G., Rahman, I. VEGFR-2 inhibition augments cigarette smoke-induced oxidative stress and inflammatory responses leading to endothelial dysfunction. [ABSTRACT FROM AUTHOR]

Angiogenesis is a physiological process for the formation of new blood vessels from the pre-existing vessels and it has a vital role in the survival and growth of neoplasms. During tumor angiogenesis, the activation of the gene transcriptions in vascular endothelial cells (ECs) plays an essential role in the promotion of EC proliferation, migration, and vascular network development. However, the molecular mechanisms underlying transcriptional regulation of EC and tumor angiogenesis remains to be fully elucidated. Here we report that the transcription factor Yin Yang 1 (YY1) in ECs is critically involved in tumor angiogenesis. First, we utilized a tamoxifen-inducible EC-specific YY1 deficient mouse model and showed that YY1 deletion in ECs inhibited the tumor growth and tumor angiogenesis. Using the in vivo matrigel plug assay, we then found that EC-specific YY1 ablation inhibited growth factor-induced angiogenesis. Furthermore, vascular endothelial growth factor (VEGF)-induced EC migration was diminished in YY1-depleted human umbilical vein endothelial cells (HUVECs). Finally, a rescue experiment revealed that YY1-regulated BMP6 expression in ECs was involved in EC migration. Collectively, our results demonstrate that endothelial YY1 has a crucial role in tumor angiogenesis and suggest that targeting endothelial YY1 could be a potential therapeutic strategy for cancer treatment. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor (VEGF) is essential for many angiogenic processes. Histone deacetylases (HDACs) have emerged as key transcriptional regulators. Here we showed that VEGF induced Protein kinase D (PKD)-dependent HDAC5 phosphorylation and nuclear export in endothelial cells. VEGF rapidly, stimulated HDAC5 phosphorylation (p-HDAC5) at Ser259/498 residues in a time- and dose-dependent manner in bovine aortic endothelial cells and human umbilical vein endothelial cells. VEGF-induced p-HDAC5 was mediated via VEGF receptor 2, phospholipase Cγ (PLCγ), protein kinase C (PKC) and PKD pathway. Specifically, PLCγ and PKCs inhibitors diminished p-HDAC5. Inhibiting PKD by siRNA and adenovirus encoding kinase-negative mutant blocked p-HDACS. Furthermore, VEGF stimulated nuclear export of HDAC5 in a phosphorylation-dependent manner, which leads to myocyte enhance factors-2 (MEF2) transcriptional activation. Active PKD stimulated HDAC5 nuclear export and MEF2 activation. In contrast, inhibiting PKD prevented VEGF-mediated HDAC5 nuclear export and MEF2 activation. Moreover, adenovirus encoding HDAC5 S258/498A mutant abolished VEGF-mediated HDAC5 nuclear export and MEF2 activation. Our findings reveal a novel role of PKD and HDAC5 in VEGF regulation of gene transcription and suggest that PKD and HDAC5 may emerge as potential therapeutic targets for pathological angiogenesis. [ABSTRACT FROM AUTHOR]

MicroRNA miR-126 has been shown to be required for proper angiogenesis in several models. However, its expression, regulation and function in the mouse choroid remain unclear. Our previous data has shown that miR-126 expression is enriched in the endothelial cells (ECs) of the mouse choroid. Here we report that a 5.5 kb Egfl7/miR-126 promoter drives the expression of miR-126 in the choroid ECs during choroidal vascular development. The expression of miR-126 in the ECs is regulated by flow stress likely through Krüppel-like transcriptional factors. miR-126 −/− mice show mildly delayed choroidal vascular development, but adult knockout mice develop periphery choroidal vascular lesions. This study suggests that miR-126 is largely dispensable for mouse choroidal development but required for maintaining choroidal vasculature integrity. [ABSTRACT FROM AUTHOR]

Growth factors and their downstream receptor tyrosine kinases (RTKs) mediate a number of biological processes controlling cell function. Adaptor (docking) proteins, which consist exclusively of domains and motifs that mediate molecular interactions, link receptor activation to downstream effectors. Recent studies have revealed that Grb2-associated-binders (Gab) family members (including Gab1, Gab2, and Gab3), when phosphorylated on tyrosine residues, provide binding sites for multiple effector proteins, such as Src homology-2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2) and phosphatidylinositol 3-kinase (PI3K) regulatory subunit p85, thereby playing important roles in transducing RTKs-mediated signals into pathways with diversified biological functions. Here, we provide an up-to-date overview on the domain structure and biological functions of Gab1, the most intensively studied Gab family protein, in growth factor signaling and biological functions, with a special focus on angiogenesis. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor (VEGF) is essential for normal and pathological angiogenesis. However, the signaling pathways linked to gene regulation in VEG F-induced angiogenesis are not fully understood. Here we demonstrate a critical role of protein kinase D (PKD) and histone deacetylase 5 (HDAC5) in VEGF-induced gene expression and angiogenesis. We found that VEGF stimulated HDAC5 phosphorylation and nuclear export in endothelial cells through a VEGF receptor 2-phospholipase Cγ-protein kinase C-PKD-dependent pathway. We further showed that the PKD-HDAC5 pathway mediated myocyte enhancer factor-2 transcriptional activation and a specific subset of gene expression in response to VEGF, including NR4A1, an orphan nuclear receptor involved in angiogenesis. Specifically, inhibition of PKD by overexpression of the PKD kinase-negative mutant prevents VEGF-induced HDAC5 phosphorylation and nuclear export as well as NR4A1 induction. Moreover, a mutant of HDAC5 specifically deficient in PKD-dependent phosphorylation inhibited VEGF-mediated NR4A1 expression, endothelial cell migration, and in vitro angiogenesis. These findings suggest that the PKD-HDAC5 pathway plays an important role in VEGF regulation of gene transcription and angiogenesis. [ABSTRACT FROM AUTHOR]

Periodic ovarian angiogenesis is crucial for follicular maturation and corpus luteum formation. Several prominent studies have indicated that extracellular matrix (ECM) in ovary microenvironment plays a critical role in periodic ovarian angiogenesis. It has been shown that ECM collagen bind and activate D iscoidin D omain R eceptor 2 (DDR2). However, the role of DDR2 in angiogenesis has not been fully explored. Here we show that DDR2 plays an important role in the regulation of angiogenesis and corpus luteum formation in the ovary. Specifically, we found that DDR2 was highly expressed in mouse corpus luteum endothelial cells (ECs), and systemic DDR2 loss-of-function mutant mice induced infertility due to periodic ovarian angiogenesis defect and consequent impairment of corpus luteum formation. We further found that endothelial cell-specific DDR2 deletion in mice showed similar phenotypes. Tamoxifen-inducible endothelial DDR2 knockout (DDR2iΔEC) in mice promoted corpus luteum EC apoptosis and inhibited EC proliferation. Furthermore, DDR2iΔEC mice exhibited retarded retinal angiogenesis and abnormality of sprouting angiogenesis with a blunted-end, aneurysm-like structure with fewer and dysmorphic filopodia in EC tip cells compared with those of wild-type mice. Similar results are also observed ex vivo by aortic ring sprouting angiogenesis assay and in vitro by using cultured human umbilical cord vein endothelial cells. Mechanistically, we found that DDR2 regulated the JAK-Stat3 signaling pathway that controls explicitly endothelial cell fate. DDR2 deficiency remarkably attenuated JAK1 and Stat3 phosphorylation, resulting in impairment of cell survival and angiogenesis. On the contrary, Over-expression DDR2 by adenovirus increased JAK1 and Stat3 phosphorylation, which promote EC survive and angiogenesis. Collectively, we discovered that DDR2 plays a crucial role in angiogenesis by regulating JAK-Stat3 signaling pathway and maintains ovarian physiological function. [ABSTRACT FROM AUTHOR]