Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Eph receptor/ephrin system is a recently discovered regulator of vascular development during embryogenesis. Activation of EphA2, one of the Eph receptors, reportedly suppresses cell proliferation and adhesion in a wide range of cell types, including vascular endothelial cells. Vascular endothelial growth factor (VEGF) plays a primary role in both pathological angiogenesis and abnormal vascular leakage in diabetic retinopathy. In the study described herein, we demonstrated that EphA2 stimulation by ephrinA1 in cultured bovine retinal endothelial cells inhibits VEGF-induced VEGFR2 receptor phosphorylation and its downstream signaling cascades, including PKC (protein kinase C)-ERK (extracellular signal-regulated kinase) 1/2 and Akt. This inhibition resulted in the reduction of VEGF-induced angiogenic cell activity, including migration, tube formation, and cellular proliferation. These inhibitory effects were further confirmed in animal models. Intraocular injection of ephrinA1 suppressed ischemic retinal neovascularization in a dose-dependent manner in a mouse model. At a dose of 125 ng/eye, the inhibition was 36.0 +/- 14.9% (P < 0.001). EphrinA1 also inhibited VEGF-induced retinal vascular permeability in a rat model by 46.0 +/- 10.0% (P < 0.05). These findings suggest a novel therapeutic potential for EphA2/ephrinA1 in the treatment of neovascularization and vasopermeability abnormalities in diabetic retinopathy.
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PMID:EphrinA1 inhibits vascular endothelial growth factor-induced intracellular signaling and suppresses retinal neovascularization and blood-retinal barrier breakdown. 1640 34

Vascular endothelial growth factor (VEGF) is implicated in the development of proteinuria in diabetic nephropathy. High ambient glucose present in diabetes stimulates VEGF expression in several cell types, but the molecular mechanisms are incompletely understood. Here primary cultured rat mesangial cells served as a model to investigate the signal transduction pathways involved in high-glucose-induced VEGF expression. Exposure to high glucose (25 mM) significantly increased VEGF mRNA evaluated by real-time PCR by 3 h, VEGF cellular protein content assessed by immunoblotting or immunofluorescence within 24 h, and VEGF secretion by 24 h. High-glucose-induced VEGF expression was blocked by an antioxidant, Tempol, and antisense oligonucleotides directed against p22(phox), a NADPH oxidase subunit. Inhibition of protein kinase C (PKC)-beta(1) with the specific pharmacological inhibitor LY-333531 or inhibition of PKC-zeta with a cell permeable specific pseudosubstrate peptide also prevented enhanced VEGF expression in high glucose. Enhanced VEGF secretion in high glucose was prevented by Tempol, PKC-beta(1), or PKC-zeta inhibition. In normal glucose (5.6 mM), overexpression of p22(phox) or constitutively active PKC-zeta enhanced VEGF expression. Hypoxia inducible factor-1alpha protein was significantly increased in high glucose only by 24 h, suggesting a possible contribution to high-glucose-stimulated VEGF expression at later time points. Thus reactive oxygen species generated by NADPH oxidase, and both PKC-beta(1) and -zeta, play important roles in high-glucose-stimulated VEGF expression and secretion by mesangial cells.
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PMID:Reactive oxygen species, PKC-beta1, and PKC-zeta mediate high-glucose-induced vascular endothelial growth factor expression in mesangial cells. 1771 90

Recent developments may provide an opportunity to improve outcome in individuals who develop neovascular age-related macular degeneration (ARMD). Several therapies have been introduced that show promise for halting the progression of this disorder. However, data from controlled clinical trials to test the relative efficacy of different management strategies across the subtypes of disease remain limited. New treatment modalities that target the neovascularization process, including leakage from choroidal neovascularization (CNV), are currently being developed. Vascular endothelial growth factor (VEGF) has been implicated as a key mediator in the pathogenesis of ARMD-related CNV. Anti-VEGF strategies show promise as potential therapeutic agents for the treatment of CNV and are currently undergoing active clinical investigation. Such strategies include anti-VEGF antibodies, anti-VEGF aptamer, gene therapy and protein kinase C inhibition. This article reviews the mechanism of action and rationale for anti-VEGF drugs in ARMD.
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PMID:Introduction, mechanism of action and rationale for anti-vascular endothelial growth factor drugs in age-related macular degeneration. 1795 95

Vascular endothelial growth factor (VEGF)-induced new vessels formation is a key event in diabetic retinopathy, a severe progressive multistage pathology. Literature data indicate that protein kinase C (PKC) is involved in the control of VEGF expression, but, so far, no data are available on the molecular pathway underlying this process. Within this context, we suggest the existence of a new molecular cascade, operating in retinal bovine pericytes and involving PKCbetaII, the mRNA-stabilizing protein HuR, and VEGF. In particular we show that PKCbetaII activation is responsible, through the RNA-binding protein HuR, for the increase of VEGF protein content and its release in the medium. The specificity of the PKCbetaII involvement is confirmed by experiments performed with the LY379196 compound, a selective PKCbetaII inhibitor. Following acute high-glucose insult this pathway seems still functioning, suggesting that a brief exposure to glucose does not compromise this molecular cascade in pericytes. A better understanding on this new pathway could open novel opportunities for the development of innovative pharmacological therapies useful in pathologies where VEGF plays a key role such as in diabetic retinopathy.
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PMID:PKCbetaII/HuR/VEGF: A new molecular cascade in retinal pericytes for the regulation of VEGF gene expression. 1820 86

Vascular endothelial growth factor (VEGF) is a major positive angiogenic factor. Using a murine hindlimb ischemia model, we previously showed that fibroblast growth factor-2 (FGF-2) enhances the expression of endogenous VEGF which highly contribute to the therapeutic effect of FGF-2 gene transfer. Recently, placental growth factor (PlGF) has been shown to play an important role in angiogenesis. However, the molecular mechanism of endogenous PlGF during FGF-2-mediated angiogenesis has not been elucidated. Severe hindlimb ischemia stimulated PlGF expression that was more strongly enhanced by FGF-2 gene transfer, and a blockade of PlGF activity diminished the recovery of blood flow by FGF-2-mediated angiogenesis. The PlGF expression in cultured endothelial cells was significantly enhanced by VEGF stimulation, but not by FGF-2. The upregulation of endogenous PlGF expression was significantly decreased by the inhibition of endogenous VEGF activity in vivo. Subsequent signal inhibition experiments revealed that the PKC, MEK, and possibly NF-kappaB-related pathways were essential in stimulating PlGF expression with VEGF, while p70S6K is the regulator for VEGF expression. These results indicate that the FGF-2-mediated enhancement of PlGF expression was dependent on VEGF function, and the FGF-2/VEGF axis participates in FGF-2-mediated angiogenesis indirectly via PlGF as well as directly.
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PMID:VEGF function for upregulation of endogenous PlGF expression during FGF-2-mediated therapeutic angiogenesis. 1825 38

NADPH oxidases are major sources of superoxide in the vascular wall. This study investigates the role of protein kinase C (PKC) in regulating gene expression of NADPH oxidases. Treatment of human umbilical vein endothelial cells (HUVEC) and HUVEC-derived EA.hy 926 endothelial cells with phorbol 12-myristate 13-acetate (PMA) or phorbol 12,13-dibutyrate led to a PKC-dependent biphasic expression of the gp91phox homolog Nox4. A downregulation of Nox4 was observed at 6 h and an upregulation at 48 h after phorbol ester treatment. The early Nox4 downregulation was associated with a reduced superoxide production, whereas the late Nox4 upregulation was accompanied by a clear enhancement of superoxide. PMA activated the PKC isoforms alpha and epsilon in HUVEC and EA.hy 926 cells. Knockdown of PKCepsilon by siRNA prevented the early downregulation of Nox4, whereas knockdown of PKCalpha selectively abolished the late Nox4 upregulation. Vascular endothelial growth factor (VEGF), which activates PKCalpha but not PKCepsilon in HUVEC, increased Nox4 expression without the initial downregulation. VEGF-induced Nox4 upregulation was associated with an enhanced proliferation and angiogenesis of HUVEC. Both effects could be reduced by inhibition of NADPH oxidase. Thus, a selective inhibition/knockdown of PKCalpha may represent a novel therapeutic strategy for vascular disease.
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PMID:Differential roles of PKCalpha and PKCepsilon in controlling the gene expression of Nox4 in human endothelial cells. 1829 Nov 20

Vascular endothelial growth factor (VEGF) is essential for normal and pathological angiogenesis. However, the signaling pathways linked to gene regulation in VEGF-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 Cgamma-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.
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PMID:Protein kinase D-dependent phosphorylation and nuclear export of histone deacetylase 5 mediates vascular endothelial growth factor-induced gene expression and angiogenesis. 1833 34

Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis and progression of malignant brain tumors. Given the significance of tumor microenvironment in general, and the established role of paracrine VEGF signaling in glioblastoma (GBM) biology in particular, we explored the potential autocrine control of human astrocytoma behavior by VEGF. Using a range of cell and molecular biology approaches to study a panel of astrocytoma (grade III and IV/GBM)-derived cell lines and a series of clinical specimens from low- and high-grade astrocytomas, we show that co-expression of VEGF and VEGF receptors (VEGFRs) occurs commonly in astrocytoma cells. We found VEGF secretion and VEGF-induced biological effects (modulation of cell cycle progression and enhanced viability of glioblastoma cells) to function in an autocrine manner. Morevover, we demonstrated that the autocrine VEGF signaling is mediated via VEGFR2 (KDR), and involves co-activation of the c-Raf/MAPK, PI3K/Akt and PLC/PKC pathways. Blockade of VEGFR2 by the selective inhibitor (SU1498) abrogated the VEGF-mediated enhancement of astrocytoma cell growth and viability under unperturbed culture conditions. In addition, such interference with VEGF-VEGFR2 signaling potentiated the ionizing radiation-induced tumor cell death. In clinical specimens, both VEGFRs and VEGF were co-expressed in astroglial tumor cells, and higher VEGF expression correlated with tumor progression, thereby supporting the relevance of functional VEGF-VEGFR signaling in vivo. Overall, our results are consistent with a potential autocrine role of the VEGF-VEGFR2 (KDR) interplay as a factor contributing to malignant astrocytoma growth and radioresistance, thereby supporting the candidacy of this signaling cascade as a therapeutic target, possibly in combination with radiotherapy.
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PMID:Autocrine regulation of glioblastoma cell cycle progression, viability and radioresistance through the VEGF-VEGFR2 (KDR) interplay. 1871 73

Vascular endothelial growth factor receptor-1/fms-related tyrosine kinase 1 (VEGFR-1/FLT1) is expressed as a membrane-bound receptor tyrosine kinase and as an alternatively spliced soluble protein (sVEGFR-1) containing the 1-6 IgG-like domain of its ectodomain. sVEGFR-1 is known as a naturally occurring inhibitor of angiogenesis and as a surrogate marker for cancer progression; it is also linked to pregnancy-induced hypertension called preeclampsia and to avascularity of normal cornea. It remains an open question whether alternative mRNA splicing is the only mechanism by which sVEGFR-1 is generated. In this study, we show that in leukemic cancer cells, PlGF and VEGF-A both induce tyrosine phosphorylation of VEGFR-1 and render it susceptible to ectodomain shedding, resulting in the generation of sVEGFR-1 and an intracellular cytoplasmic fragment. Activation of protein kinase C and tumor necrosis factor-alpha-converting enzyme family metalloproteases are critically required for the occurrence of sVEGFR-1. Following the removal of the ectodomain, the remnant of VEGFR-1 remains attached to the membrane, and the activity of gamma-secretase/presenilin is required for its release from the cell membrane. We propose that sVEGFR-1 produced via ectodomain shedding plays a prominent role in the VEGF receptor system by antagonizing VEGF receptor signaling by acting as a dominant-negative form and/or forming a nonsignaling dimerizing complex with VEGF receptors.
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PMID:Identification of ligand-induced proteolytic cleavage and ectodomain shedding of VEGFR-1/FLT1 in leukemic cancer cells. 1927 74

Vascular endothelial growth factor (VEGF) is a potent angiogenic cytokine that also increases vascular permeability. Nitric oxide (NO) released from endothelial cells, after activation of endothelial NO synthase (eNOS), contributes to proangiogenic and permeability effects of VEGF. Angiopoietin-1 (Ang-1), via Tie2 receptors, shares many of the proangiogenic properties of VEGF on endothelial cells. However, in contrast to VEGF, Ang-1 protects blood vessels from increased plasma leakage, which contributes to their stabilization. Because eNOS-derived NO is central to increased permeability in response to VEGF, we investigated whether Ang-1 interferes with VEGF signaling to eNOS. We demonstrate that Ang-1 stimulation of endothelial cells inhibits VEGF-induced NO release and transendothelial permeability. In contrast to VEGF stimulation, Ang-1 causes a marked protein kinase C (PKC)-dependent increase in phosphorylation of eNOS on the inhibitory Thr(497). Furthermore, using pharmacologic inhibitors, overexpression studies, and small interfering RNA-mediated gene silencing, we demonstrate that atypical PKC zeta is responsible for phosphorylation of eNOS on Thr(497) in response to Ang-1. In addition, PKC zeta knockdown abrogates the capacity of Ang-1 to inhibit VEGF-induced NO release and endothelial permeability. Thus, inhibition of NO production by Ang-1, via phosphorylation of eNOS on Thr(497) by PKC zeta, is responsible, at least in part, for inhibition of VEGF-stimulated endothelial permeability by Ang-1.
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PMID:Phosphorylation of endothelial nitric oxide synthase by atypical PKC zeta contributes to angiopoietin-1-dependent inhibition of VEGF-induced endothelial permeability in vitro. 1956 38


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