Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.13 (protein kinase C)
49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

White adipose tissue from rats was examined for insulin- responsive vascular endothelial growth factor 165 (VEGF) secretion and mRNA expression. When separated into it constituent fat vs. stromal-vascular cells using collagenase digestion methods, only the adipocytes (or whole fat tissue) responded to physiological insulin concentrations by doubling VEGF release over 4 and 24 h in culture. Adipocyte VEGF mRNA expression increased similarly. Several adipose depots were tested. Although omental fat cells had the highest rates of VEGF release, the differences were not significant. Insulin-stimulated VEGF release was mediated in part via PI3K, but not PKC. Additional hormones/agents were tested, including steroids, leptin, an adenosine analog, and norepinephrine. Only the latter compound increased VEGF production, and this effect was mediated by adenylate cyclase. Adjusting the incubation glucose concentration between 0-20 mM did not alter adipocyte VEGF release. An experimental mimic of hypoxia, CoCl(2), also increased adipocyte VEGF, and this effect was additive with 100 nM insulin. These studies demonstrate that physiological insulin concentrations stimulate VEGF formation and expression in cultured rodent white adipocytes. Although the biological significance of this observation remains to be determined, if white adipocyte-derived VEGF has paracrine or systemic endocrine actions, these might hypothetically impact on adipose expansion or the vascular comorbidities of obesity.
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PMID:White adipocyte vascular endothelial growth factor: regulation by insulin. 1186 17

Acute intensive insulin therapy is an independent risk factor for diabetic retinopathy. Here we demonstrate that acute intensive insulin therapy markedly increases VEGF mRNA and protein levels in the retinae of diabetic rats. Retinal nuclear extracts from insulin-treated rats contain higher hypoxia-inducible factor-1alpha (HIF-1alpha) levels and demonstrate increased HIF-1alpha-dependent binding to hypoxia-responsive elements in the VEGF promoter. Blood-retinal barrier breakdown is markedly increased with acute intensive insulin therapy but can be reversed by treating animals with a fusion protein containing a soluble form of the VEGF receptor Flt; a control fusion protein has no such protective effect. The insulin-induced retinal HIF-1alpha and VEGF increases and the related blood-retinal barrier breakdown are suppressed by inhibitors of p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol (PI) 3-kinase, but not inhibitors of p42/p44 MAPK or protein kinase C. Taken together, these findings indicate that acute intensive insulin therapy produces a transient worsening of diabetic blood-retinal barrier breakdown via an HIF-1alpha-mediated increase in retinal VEGF expression. Insulin-induced VEGF expression requires p38 MAPK and PI 3-kinase, whereas hyperglycemia-induced VEGF expression is HIF-1alpha-independent and requires PKC and p42/p44 MAPK. To our knowledge, these data are the first to identify a specific mechanism for the transient worsening of diabetic retinopathy, specifically blood-retinal barrier breakdown, that follows the institution of intensive insulin therapy.
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PMID:Acute intensive insulin therapy exacerbates diabetic blood-retinal barrier breakdown via hypoxia-inducible factor-1alpha and VEGF. 1190 Nov 89

Accumulating evidence points to a causal role for advanced glycation end products (AGEs) in the development of diabetic vascular complications, including retinopathy. Possible pathogenic mechanisms linking AGEs to diabetic retinopathy include protein kinase C (PKC) activation, oxidative stress, and vascular endothelial growth factor (VEGF) expression. In the present study, we investigated the effect of AGEs on VEGF expression in bovine retinal endothelial cells (BRECs) and determined the role of PKC and oxidative stress in this effect. Incubation of BRECs with AGEs led to enhanced VEGF mRNA and protein expression. This treatment also induced PKC translocation in these cells. The AGE-induced increases in VEGF expression and PKC activation were inhibited by the pan-specific PKC inhibitor, calphostin C, and by the antioxidant drug and compounds, gliclazide, N-acetylcysteine, and vitamin E. In contrast, glyburide which does not exhibit antioxidant properties, did not affect the AGE-induced VEGF expression. Exposure of BRECs to AGEs resulted in a significant increase of nuclear protein binding to the NF-kappa B consensus sequence of the VEGF promoter region. Induction of DNA binding activity for NF-kappa B by AGEs was prevented by gliclazide. Treatment of BRECs with AGEs also increased the proliferation of these cells. This effect was abrogated by incubating the cells with an anti-VEGF antibody and was inhibited in the presence of gliclazide. Overall, these data demonstrate that AGEs increase VEGF expression in retinal endothelial cells through generation of oxidative stress and downstream activation of the PKC pathway. Targeting VEGF expression with specific pharmacological agents, such as antioxidants and PKC inhibitors, may prove efficacious for the treatment of diabetic retinopathy.
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PMID:Advanced glycation end products increase, through a protein kinase C-dependent pathway, vascular endothelial growth factor expression in retinal endothelial cells. Inhibitory effect of gliclazide. 1212 87

Objective. To investigate the relationship between Vascular endothelial growth factor (VEGF) gene expression and protein kinase C (PKC) activity. Method. 1) Rat's primary pulmonary artery endothelial cells (PAEC) were cultured under hypoxia condition (1% O2). Changes of PKC activity and VEGF mRNA in PAEC were detected at 0 (control), 1, 3, 6, and 12 h in the hypoxic condition of culture. 2) After addition of PKC inhibitor (staurosporine) in culture medium and culturing PAEC in hypoxic condition immediately, PKC activity and VEGF mRNA in PAEC were measured at the same time. VEGF protein in culture medium under the two conditions above were also detected. Result. PKC activity in PAEC were obviously elevated at 1 h during hypoxia as compared with the control (P<0.05); VEGF mRNA expression in PAEC and VEGF protein level in culture medium were increased significantly (P<0.01) at 3 h and 6 h during hypoxia respectively as compared with the control (P<0.01); After addition of PKC inhibitor in culture medium and culturing cells in hypoxia condition immediately, PKC activity in PAEC decreased significantly as compared with that at 0 h (P<0.01), and there were no significant changes of VEGF mRNA in PAEC and VEGF protein level in culture medium at any time (P>0.05). Conclusion. The results demonstrate that hypoxia stimulates pulmonary arterial vascular endothelial cells to secrete VEGF, and PKC may be one of the factors that up-regulate VEGF gene expression during hypoxia.
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PMID:Vascular endothelial growth factor gene expression regulated by protein kinase C pathway in endothelial cells during hypoxia. 1244 34

Vascular endothelial growth factor (VEGF) stimulates angiogenesis during development and in disease. In pheochromocytoma (PC12) cells, VEGF expression is regulated by A(2A) adenosine receptor (A(2A)AR) activation. The present work examines the underlying signaling pathway. The adenylyl cyclase-protein kinase A cascade has no role in the down-regulation of VEGF mRNA induced by the A(2A)AR agonist, 2-[4-[(2-carboxyethyl)phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine (CGS21680). Conversely, 6-h exposure of cells to either phorbol 12-myristate 13-acetate (PMA) or protein kinase C (PKC) inhibitors mimicked the CGS21680-induced down-regulation. PMA activated PKCalpha, PKCepsilon, and PKCzeta, and CGS21680 activated PKCepsilon and PKCzeta as assessed by cellular translocation. By 6 h, PMA but not CGS21680 decreased PKCalpha and PKCepsilon expression. Neither compound affected PKCzeta levels. Following prolonged PMA treatment to down-regulate susceptible PKC isoforms, CGS21680 but not PMA inhibited the cobalt chloride induction of VEGF mRNA. The proteasome inhibitor, MG-132, abolished PMA- but not CGS21680-induced down-regulation of VEGF mRNA. Phorbol 12,13-diacetate reduced VEGF mRNA levels while down-regulating PKCepsilon but not PKCalpha expression. In cells expressing a dominant negative PKCzeta construct, CGS21680 was unable to reduce VEGF mRNA. Together, the findings suggest that phorbol ester-induced down-regulation of VEGF mRNA occurs as a result of a reduction of PKCepsilon activity, whereas that mediated by the A(2A)AR occurs following deactivation of PKCzeta.
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PMID:Distinct protein kinase C isoforms mediate regulation of vascular endothelial growth factor expression by A2A adenosine receptor activation and phorbol esters in pheochromocytoma PC12 cells. 1259 Jan 38

Vascular endothelial growth factor (VEGF) is a major agent in choroidal and retinal neovascularization, events associated with age-related macular degeneration (AMD) and diabetic retinopathy. Retinal pigment epithelium (RPE), strategically located between retina and choroid, plays a critical role in retinal disorders. We have examined the effects of various growth factors on the expression and secretion of VEGF by human retinal pigment epithelial cell cultures (HRPE). RT-PCR analyses revealed the presence of three isoforms of mRNA corresponding to VEGF 121, 165, and 189 that were up regulated by TGF-beta1. TGF-beta1, beta2, and beta3 were the potent inducers of VEGF secretion by HRPE cells whereas bFGF, PDGF, TGF-alpha, and GM-CSF had no effects. TGF-beta receptor type II antibody significantly reversed induction of VEGF secretion by TGF-beta. In contrast activin, inhibin and BMP, members of TGF-beta super family, had no effects on VEGF expression in HRPE. VEGF mRNA levels and protein secretion induced by TGF-beta were significantly inhibited by SB203580 and U0126, inhibitors of MAP kinases, but not by staurosporine and PDTC, protein kinase C and NF-kappaB pathway inhibitors, respectively. TGF-beta also induced VEGF expression by fibroblasts derived from human choroid of eye. TGF-beta induction of VEGF secretion by RPE and choroid cells may play a significant role in choroidal neovascularization (CNV) in AMD. Since the secretion of VEGF by HRPE is regulated by MAP kinase pathways, MAP kinase inhibitors may have potential use as therapeutic agents for CNV in AMD.
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PMID:Transforming growth factor-beta induces expression of vascular endothelial growth factor in human retinal pigment epithelial cells: involvement of mitogen-activated protein kinases. 1456 75

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), the critical molecule in tumor angiogenesis, is regulated by different stimuli, such as hypoxia and oncogenes, and also by growth factors. Previously we have shown that in AsPC-1 pancreatic adenocarcinoma cells, insulin-like growth factor receptor (IGF-IR) regulates VPF/VEGF expression. Insulin receptor substrate-1 and -2 (IRS-1 and IRS-2), two major downstream molecules of IGF-1R, are known to be important in the genesis of diabetes. In this study, we have defined a new role of IRS in angiogenesis. Both of the IRS proteins modulate VPF/VEGF expression in pancreatic cancer cells by different mechanistic pathways. The Sp1-dependent VPF/VEGF transcription is regulated mainly by IRS-2. Protein kinase C-zeta (PKC-zeta) plays a central role in VPF/VEGF expression and acts as a switching element. Furthermore, we have also demonstrated that the phosphatidylinositol 3-kinase pathway, but not the Ras pathway, is a downstream event of IRS proteins for VPF/VEGF expression in AsPC-1 cells. Interestingly, like renal cancer cells, in AsPC-1 cells PKC-zeta leads to direct Sp1-dependent VPF/VEGF transcription; in addition, it also promotes a negative feedback loop to IRS-2 that decreases the association of IRS-2/IGF-1R and IRS-2/p85. Taken together, our results show that in AsPC-1 pancreatic carcinoma cells, Sp1-dependent VPF/VEGF transcription is controlled by IGF-1R signaling through IRS-2 proteins and modulated by a negative feedback loop of PKC-zeta to IRS-2. Our data also suggest that IRS proteins, which are known to play crucial roles in IGF-1R signaling, are also important mediators for tumor angiogenesis.
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PMID:Role of insulin receptor substrates and protein kinase C-zeta in vascular permeability factor/vascular endothelial growth factor expression in pancreatic cancer cells. 1460 96

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen that promotes angiogenesis, vasculogenesis, and increases vascular permeability. VEGF is expressed in renal tubular epithelial cells and urinary VEGF excretion is increased in various glomerular disorders. However, the mechanisms underlying expression of VEGF in renal tubular epithelial cells have not been fully elucidated. In the present study, we attempted to define a predominant regulator of VEGF expression using a cultured murine renal proximal tubular epithelial cell line (mProx24). VEGF protein concentration in the culture supernatant was measured by sandwich enzyme-linked immunosorbent assay. mProx24 constitutively produced VEGF at low level. Major isoforms expressed in this cell line were VEGF164 and VEGF120 determined by reverse transcription-polymerase chain reaction method. Among various stimuli including angiotensin II, transforming growth factor-beta1 (TGF-beta1), lipopolysaccharides, interleukin-1beta, interleukin-10 and interferon-gamma, only TGF-beta1 significantly increased the level of VEGF protein at 24 h in a dose-dependent manner. The steady-state mRNA level of VEGF was dose dependently increased by TGF-beta1 detected by Northern blotting. Treatment with neutralizing anti-TGF-beta1 antibody abolished TGF-beta1-induced VEGF expression by 70%. Inhibitors of protein kinase C (PKC), Ro-31-8220 and staurosporin, significantly suppressed TGF-beta1-induced VEGF protein expression. These results demonstrate the role of TGF-beta1 on the expression of VEGF in proximal tubular epithelial cells mediated potentially via PKC pathway. This regulatory mechanism may be associated with the progression of tubulointerstitial lesions in renal disorders.
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PMID:Transforming growth factor-beta 1 induces vascular endothelial growth factor expression in murine proximal tubular epithelial cells. 1461 Mar 27

The central role of VEGF (vascular endothelial growth factor A) in angiogenesis is dependent upon its ability to co-ordinately regulate multiple endothelial functions. The multifunctionality of VEGF at the cellular level results from its ability to initiate a diverse, complex and integrated network of signalling pathways via its major receptor, kinase-insert-domain-containing receptor (KDR). Activation of phospholipase C-gamma, protein kinase C, Ca(2+), ERK (extracellular-signal-regulated protein kinase), Akt, Src, focal adhesion kinase and calcineurin pathways has been implicated in mediating multiple VEGF functions, including survival, proliferation, migration, vascular permeability, tubulogenesis, NO and prostanoid synthesis, and gene expression. NO and prostanoids in turn play paracrine and autocrine roles in linking post-receptor signalling to biological functions. Integration between biologically important signalling cascades occurs at several points. Akt and ERK, for example, are key junction points linking together signal transduction involved in survival and NO generation, and proliferation and prostanoid biosynthesis. Together, the multiplicity, functional versatility and integration of VEGF signalling provide a useful framework for understanding the mechanisms underlying the endothelial biological response to this key factor.
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PMID:VEGF signalling: integration and multi-tasking in endothelial cell biology. 1464 Oct 20

Hydroxylation at an asparagine residue at the COOH-terminal activation domain of hypoxia-inducible factor (HIF)-1/2 alphas is essential for its inactivation under normoxic condition. To date, the mechanism by which HIF-alpha avoids the inhibitory effect of asparagine hydroxylase in renal cell carcinoma (RCC) in normoxia is undefined. We have shown herein that protein kinase C (PKC) zeta has an important role in HIF-alpha activation in RCC. By using dominant negative mutant and small interference RNA approaches, we have demonstrated that the association between HIF-alpha and p300 is modulated by PKCzeta. Moreover, a novel signaling pathway involving phosphatidylinositol 3'-kinase and PKCzeta has been shown to be responsible for the activation of HIF-alpha by inhibiting the mRNA expression of FIH-1 (factor inhibiting HIF-1) in RCC and thereby promoting the transcription of hypoxia-inducible genes such as vascular permeability factor/vascular endothelial growth factor.
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PMID:Protein kinase C zeta transactivates hypoxia-inducible factor alpha by promoting its association with p300 in renal cancer. 1474 56


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