Vascular Endothelial Growth Factor mRNA Stability Research Articles

Ursolic acid-downregulated long noncoding RNA ASMTL-AS1 inhibits renal cell carcinoma growth via binding to HuR and reducing vascular endothelial growth factor expression.

It has been reported ursolic acid (UA), one of the naturally abundant pentacyclic triterpenes, possesses a wide range of biological activities including anti-inflammatory, anti-atherosclerotic, and anticancer properties. Renal cell carcinoma (RCC) is a severe malignancy due to its asymptomatically spreading ability. Our study aimed to investigate the role and molecular mechanism of UA in RCC. RCC cell proliferation, migration, invasion, and angiogenesis were assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Transwell, and tube formation assays. Xenograft tumor models were established to confirm the role of UA and long noncoding RNA ASMTL antisense RNA 1 (ASMTL-AS1) in vivo. Expression levels of ASMTL-AS1 and vascular endothelial growth factor (VEGF) were measured using reverse transcriptase quantitative polymerase chain reaction and western blot analysis. The interaction probabilities of ASMTL-AS1 or VEGF with RNA-binding protein human antigen R (HuR) were verified by RNA immunoprecipitation experiment. The half-life period of messenger RNA (mRNA) was determined using actinomycin D. UA inhibited RCC cell growth in vivo and tumorigenesis in vitro. ASMTL-AS1 was highly expressed in RCC cell lines. Of note, UA downregulated ASMTL-AS1 expression, and overexpressed ASMTL-AS1 reversed the UA-induced suppression on RCC cell migration, invasion, and tube formation. Additionally, ASMTL-AS1 bound to HuR to maintain the stability of VEGF mRNA. Rescue experiments showed that the suppressed malignancy of RCC cells mediated by ASMTL-AS1 knockdown was counteracted by overexpression of VEGF. Moreover, silenced ASMTL-AS1 inhibited RCC tumor growth and metastasis in vivo. The obtained data suggest UA as a promising therapeutic agent to attenuate the development of RCC via regulation of the targeted molecules.

Human antigen R protein modulates vascular endothelial growth factor expression in human corneal epithelial cells under hypoxia

Corneal avascularity is critical for corneal transparency; therefore, a tailored process has been presumed to minimize corneal neovascularization (NV). In most cell types, the transcription of vascular endothelial growth factor (VEGF) is up-regulated, and the stability of VEGF mRNA is sustained by human antigen R (HuR) during hypoxia; however, whether such response applies to corneal epithelial cells is unclear. Human corneal epithelial cells (HCECs) and MCF-7cells that serves as the control were incubated under 0.5% oxygen, and the levels of VEGF and HuR were examined time-dependently. The alteration of HuR was also examined invivo using the closed-eye contact lens-induced corneal neovascularization rabbit model and immunohistochemistry. Additionally, the expression of HuR was modulated by transfection of plasmids encoding HuR or siRNA targeting HuR to validate the role of HuR in VEGF expression. We found that, unlike in control cells, the level of VEGF was not up-regulated, and the HuR expression was declined in HCECs following hypoxia. The HuR immunostaining intensities were decreased in corneal epithelial cells of rabbits wearing contact lenses. In addition, HuR overexpression restored the ability of HCECs to up-regulate VEGF under hypoxia; however, knockdown of HuR suppressed hypoxia-induced VEGF in control cells but did not further decrease VEGF in HCECs. These findings suggest that HCECs may modulate HuR to suppress hypoxia-mediated up-regulation of VEGF. Our study revealed a distinct regulation of VEGF via HuR in HCECs following hypoxia, which likely contributes to minimizing corneal NV and/or maintenance of corneal avascularity.

The PPARβ agonist L-165041 promotes VEGF mRNA stabilization in HPV18-harboring HeLa cells through a receptor-independent mechanism

Peroxisome Proliferator-Activated Receptor-β (PPARβ) is a ligand-inducible transcription factor activated by both natural (fatty acids and derivatives) and high affinity synthetic agonists. It is thought to play a role in angiogenesis development and Vascular Endothelial Growth Factor (VEGF) regulation but its contribution remains unclear. Until now, the PPARβ agonism effect on VEGF expression in cervical cancer cells was unknown. This led to our interest in assessing the effect of PPARβ activation on the regulation of different VEGF isoforms mRNA expression and the impact of E6 viral oncoprotein and its target p53 on this regulation in cervical cancer cells. Here, we showed that the PPARβ agonist L-165041 induces VEGF121, VEGF165 and VEGF189 expression in HPV (Human Papillomavirus) positive HeLa cells but not in HPV negative cells. The underlying mechanisms did involve neither E6 oncoprotein nor p53. We highlighted a novel mode of PPARβ ligand action including a post-transcriptional regulation of VEGF mRNA expression through the p38 MAPK signaling pathway and the activation of the mRNA-stabilizing factor HuR. But most importantly, we clearly demonstrated that L-165041 acts independently of PPARβ since its effect was not reversed by a chemical inhibition with a specific antagonist and the siRNA-mediated knockdown of the nuclear receptor. As VEGF is crucial for cancer development, the impact of PPARβ ligands on VEGF production is of high importance. Thus, the molecular mechanism of their action has to be elucidated and as a result, PPARβ agonists currently in clinical trials should be carefully monitored.

Hsp70 Is a Novel Posttranscriptional Regulator of Gene Expression That Binds and Stabilizes Selected mRNAs Containing AU-Rich Elements

The AU-rich elements (AREs) encoded within many mRNA 3' untranslated regions (3'UTRs) are targets for factors that control transcript longevity and translational efficiency. Hsp70, best known as a protein chaperone with well-defined peptide-refolding properties, is known to interact with ARE-like RNA substrates in vitro. Here, we show that cofactor-free preparations of Hsp70 form direct, high-affinity complexes with ARE substrates based on specific recognition of U-rich sequences by both the ATP- and peptide-binding domains. Suppressing Hsp70 in HeLa cells destabilized an ARE reporter mRNA, indicating a novel ARE-directed mRNA-stabilizing role for this protein. Hsp70 also bound and stabilized endogenous ARE-containing mRNAs encoding vascular endothelial growth factor (VEGF) and Cox-2, which involved a mechanism that was unaffected by an inhibitor of its protein chaperone function. Hsp70 recognition and stabilization of VEGF mRNA was mediated by an ARE-like sequence in the proximal 3'UTR. Finally, stabilization of VEGF mRNA coincided with the accumulation of Hsp70 protein in HL60 promyelocytic leukemia cells recovering from acute thermal stress. We propose that the binding and stabilization of selected ARE-containing mRNAs may contribute to the cytoprotective effects of Hsp70 following cellular stress but may also provide a novel mechanism linking constitutively elevated Hsp70 expression to the development of aggressive neoplastic phenotypes.

MDM2 Regulates Vascular Endothelial Growth Factor mRNA Stabilization in Hypoxia

Expression of vascular endothelial growth factor (VEGF) increases in cancer cells during hypoxia. Herein, we report that the MDM2 oncoprotein plays a role in hypoxia-mediated VEGF upregulation. In studying the characteristics of MDM2 and VEGF expression in neuroblastoma cells, we found that hypoxia induced significantly higher upregulation of both VEGF mRNA and protein in MDM2-positive cells than in the MDM2-negative cells, even in cells without wild-type (wt) p53. We found that hypoxia induced translocation of MDM2 from the nucleus to the cytoplasm, which was associated with increased VEGF expression. Enforcing overexpression of cytoplasmic MDM2 by transfection of the mutant MDM2/166A enhanced expression of VEGF mRNA and protein production, even without hypoxia. The results of mechanistic studies demonstrated that the C-terminal RING domain of the MDM2 protein bound to the AU-rich sequence within the 3' untranslated region (3'UTR) of VEGF mRNA; this binding increased VEGF mRNA stability and translation. In addition, knockdown of MDM2 by small interfering RNA (siRNA) in MDM2-overexpressing cancer cells resulted in inhibition of VEGF protein production, cancer cell survival, and angiogenesis. Our results suggest that MDM2 plays a p53-independent role in the regulation of VEGF, which may promote tumor growth and metastasis.

Thymosin β4 induces the expression of vascular endothelial growth factor (VEGF) in a hypoxia-inducible factor (HIF)-1α-dependent manner

Thymosin β4 has multi-functional roles in cell physiology, but little is known about its mechanism(s) of action. We previously reported that thymosin β4 stimulated angiogenesis through the induction of vascular endothelial growth factor (VEGF). To identify the mechanism of VEGF induction by thymosin β4, we have used a luciferase assay system with VEGF in the 5' promoter region. We also analyzed the effect of thymosin β4 on VEGF mRNA stability and on the expression and stability of hypoxia-inducible factor (HIF)-1α. We found that thymosin β4 induces VEGF expression by an increase in the stability of HIF-1α protein. Analysis of the expression patterns of thymosin β4 and HIF-1α in colon cancer tissue microarray showed that thymosin β4 and HIF-1α co-localized in these biopsies. These data show that thymosin β4 induces the expression of VEGF indirectly by increasing the protein stability of HIF-1α.

Altered VEGF mRNA Stability following Treatments with Immunosuppressive Agents: IMPLICATIONS FOR CANCER DEVELOPMENT

The high incidence of cancer and its aggressive progression is a common and major problem in patients receiving immunosuppressive therapy. The calcineurin inhibitors (CNIs) may have protumorigenic effects and can promote the overexpression of several molecules inducing tumor growth. We have recently demonstrated that CNIs can mediate the transcriptional activation of the angiogenic cytokine vascular endothelial growth factor (VEGF) and promote a rapid progression of human renal cancer. Here, we investigated whether the CNI cyclosporine (CsA) and the mTOR inhibitor rapamycin (RAPA) could alter the mRNA stability of VEGF in 786-0 and Caki-1 renal cancer cells. Following actinomycin D treatment, we observed that CsA increased, whereas RAPA decreased the VEGF mRNA stability as observed by real time PCR. It is established that the mRNA-binding protein HuR may play a critical role in VEGF mRNA stability. By using HuR-siRNA, we found that the knockdown of HuR significantly decreased the CNI-induced VEGF mRNA stability. By Western blot analysis, it has been observed that CNI treatment induced the translocation of HuR from the nucleus to the cytoplasm; CNIs also induced the association between HuR and PKC-delta and promoted the phosphorylation of HuR. Finally, we found that the inhibition of PKC-delta using a dominant negative plasmid significantly decreased the CsA-induced cytoplasmic translocation of HuR and VEGF mRNA stability. Together, targeting the pathways that promote CNI-induced transcription as well as the mRNA stability of VEGF might serve as novel therapeutics for the prevention and treatment of cancer in immunosuppressed patients.

Abstract LB-371: Altered vascular endothelial growth factor mRNA stability may lead to cancer development following immunosuppressive therapy

Abstract The development of cancer is an increasing and major problem in immunosuppressed patients, particularly after solid organ transplantation. In part, the increased cancer risk is associated with the use of immunosuppressive agents, especially calcineurin inhibitors (CNIs). The CNIs are used to prevent inflammatory diseases and allograft rejection. However, little is known about the mechanism(s) underlying their ability to promote the development and recurrence of cancer. We have recently demonstrated that CNI can mediate the transcriptional activation of the angiogenic cytokine vascular endothelial growth factor (VEGF) and promote a rapid progression of human renal cancer. In contrast, the mTOR inhibitor rapamycin (RAPA), which is thought to have anti-cancer effects, has been reported to decrease VEGF expression. Here, we investigated whether the CNI cyclosporine (CsA) and RAPA could alter the mRNA stability of VEGF in 786-0 and Caki-1 renal cancer cells. By using actinomycin-D, we observed that CsA increased, while RAPA decreased the VEGF mRNA stability as observed by real time PCR. It is established that the mRNA-binding protein HuR may play a critical role in VEGF mRNA stability. By using HuR-siRNA, we found that the knockdown of HuR significantly decreased the CNI-induced VEGF mRNA stability. By Western blot analysis, it has been observed that CNI treatment induced the translocation of HuR from the nucleus to the cytoplasm; CNI also induced the association between HuR and protein kinase C (PKC)-δ, and promoted the phosphorylation of HuR. Interestingly, there was no significant change in the cytoplasmic translocation of HuR following RAPA treatment. Finally, we found that the inhibition of PKC-δ using a dominant-negative plasmid significantly decreased the CsA-induced cytoplasmic translocation of HuR and the VEGF mRNA stability. Together, we suggest that targeting the pathways that promote the transcription as well as the mRNA stability (post-transcriptional modification) of VEGF in response to CNI might serve as novel therapeutics for the prevention and treatment of cancer in immunosuppressed patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-371.

Amyotrophic Lateral Sclerosis-linked Mutant SOD1 Sequesters Hu Antigen R (HuR) and TIA-1-related Protein (TIAR)

Down-regulation of vascular endothelial growth factor (VEGF) in the mouse leads to progressive and selective degeneration of motor neurons similar to amyotrophic lateral sclerosis (ALS). In mice expressing ALS-associated mutant superoxide dismutase 1 (SOD1), VEGF mRNA expression in the spinal cord declines significantly prior to the onset of clinical manifestations. In vitro models suggest that dysregulation of VEGF mRNA stability contributes to that decline. Here, we show that the major RNA stabilizer, Hu Antigen R (HuR), and TIA-1-related protein (TIAR) colocalize with mutant SOD1 in mouse spinal cord extracts and cultured glioma cells. The colocalization was markedly reduced or abolished by RNase treatment. Immunoanalysis of transfected cells indicated that colocalization occurred in insoluble aggregates and inclusions. RNA immunoprecipitation showed a significant loss of VEGF mRNA binding to HuR and TIAR in mutant SOD1 cells, and there was marked depletion of HuR from polysomes. Ectopic expression of HuR in mutant SOD1 cells more than doubled the mRNA half-life of VEGF and significantly increased expression to that of wild-type SOD1 control. Cellular effects produced by mutant SOD1, including impaired mitochondrial function and oxidative stress-induced apoptosis, were reversed by HuR in a gene dose-dependent pattern. In summary, our findings indicate that mutant SOD1 impairs post-transcriptional regulation by sequestering key regulatory RNA-binding proteins. The rescue effect of HuR suggests that this impairment, whether related to VEGF or other potential mRNA targets, contributes to cytotoxicity in ALS.

TGF Presence During IgE-dependent Sensitization Primes Mast Cells for Higher VEGF Production After Fc RI Activation

Binding of monomeric Immunoglobulin E (IgE) to the high affinity IgE receptor (FcεRI) on mast cells induces a sensitization process which increases cell survival, augments membrane receptor expression and diminishes activation threshold. Although IgE-dependent sensitization is fundamental for allergic reactions, little is known about the influence of locally produced mediators on the outcome of a posterior allergen challenge. Since Transforming Growth Factorβ (TGFβ) is an important immunomodulator present in most of the tissues where mast cells reside, we decided to analyze the consequences of TGFβ exposure during the sensitization step of mast cells on a posterior IgE-antigen stimulation. Bone Marrow-derived Mast Cells (BMMCs) were sensitized with IgE in the presence or absence of TGFβ. Then, antigen was added and the secretion of the angiogenic cytokine Vascular Endothelial Growth Factor (VEGF) was determined. BMMCs sensitized with IgE+TGFβ showed an increased antigen-induced VEGF secretion compared to those sensitized with IgE alone. Sensitization with IgE+TGFβ did not modify membrane FcεRI receptor expression neither altered antigen-induced degranulation of the cells. Although both IgE and IgE+TGFβ sensitized cells showed an increase in VEGF mRNA stabilization after antigen addition, VEGF mRNA half-life was longer in IgE+TGFβ sensitized cells. p38 MAPK inhibitor SB202196 blocked VEGF mRNA stabilization after antigen addition specially on IgE+TGFβ sensitized cells. These findings suggest that TGFβ presence during the sensitization phase of mast cells can induce modifications to the FcεRI signal transduction system, provoking increased VEGF mRNA stabilization and protein secretion after IgE-antigen stimulation through a p38 MAPK-dependent mechanism.

AMPK regulates basal skeletal muscle capillarization and VEGF expression, but is not necessary for the angiogenic response to exercise

5'-AMP-activated protein kinase (AMPK) is a metabolic fuel sensor that monitors cellular energy charge, while the vasculature is important for maintaining cellular energy homeostasis. Mice with muscle-specific inactive AMPK (AMPK DN) were used to investigate if AMPK regulates skeletal muscle capillarization and the angiogenic responses to exercise. Two hours of the AMP analogue AICAR (1.0 g kg(-1)) or systemic hypoxia (6% O(2)) increased vascular endothelial growth factor (VEGF) mRNA in wild-type (WT), but not in AMPK DN mice. In contrast, the increase in VEGF mRNA with acute exercise (1 h at 20 m min(-1), 10% gradient) was greater in AMPK DN compared to WT mice. Nuclear run-on assay demonstrated that exercise increased VEGF transcription, while hypoxia decreased VEGF transcription. There was no difference in VEGF transcription between WT and AMPK DN. There was a strong correlation between VEGF transcription and VEGF mRNA at rest and with exercise. Resting capillarization was lower in AMPK DN compared to WT. Wheel running (28 days) increased capillarization and this response was AMPK independent. Significant correlations between VEGF protein and muscle capillarization are consistent with VEGF being an important determinant of skeletal muscle capillarization. These data are to our knowledge the first to demonstrate in skeletal muscle in vivo that: (1) AMPK is necessary for hypoxia-induced VEGF mRNA stabilization, (2) acute exercise increases VEGF transcription, (3) inhibition of AMPK augments the VEGF mRNA response to acute exercise, and (4) AMPK regulates basal VEGF expression and capillarization, but is not necessary for exercise-induced angiogenesis.

Vascular endothelial growth factor expression by hyalocytes and its regulation by glucocorticoid

Aim:Tumour necrosis factor-α (TNF-α) is one of the major inflammatory cytokines involved in the pathogenesis of various vitreoretinal diseases. The authors investigated the effect of hypoxia, TNF-α and dexamethasone on...

Tristetraprolin Inhibits Ras-dependent Tumor Vascularization by Inducing Vascular Endothelial Growth Factor mRNA Degradation

Vascular endothelial growth factor (VEGF) is one of the most important regulators of physiological and pathological angiogenesis. Constitutive activation of the extracellular signal-regulated kinase (ERK) pathway and overexpression of VEGF are common denominators of tumors from different origins. We have established a new link between these two fundamental observations converging on VEGF mRNA stability. In this complex phenomenon, tristetraprolin (TTP), an adenylate and uridylate-rich element-associated protein that binds to VEGF mRNA 3'-untranslated region, plays a key role by inducing VEGF mRNA degradation, thus maintaining basal VEGF mRNA amounts in normal cells. ERKs activation results in the accumulation of TTP mRNA. However, ERKs reduce the VEGF mRNA-destabilizing effect of TTP, leading to an increase in VEGF expression that favors the angiogenic switch. Moreover, TTP decreases RasVal12-dependent VEGF expression and development of vascularized tumors in nude mice. As a consequence, TTP might represent a novel antiangiogenic and antitumor agent acting through its destabilizing activity on VEGF mRNA. Determination of TTP and ERKs status would provide useful information for the evaluation of the angiogenic potential in human tumors.

VEGF transcription and mRNA stability are altered by WT1 not DDS(R384W) expression in LNCaP cells

To identify physiologically relevant WT1 transcriptional target genes in prostate cancer cells, we have established stably transfected LNCaP cell lines expressing either WT1(A), its mutant counterpart DDS(R384W), or vector control. Microarray analyses of these cells revealed that vascular endothelial growth factor (VEGF) was differentially expressed in the engineered lines. Regulation of VEGF by WT1 likely contributes to kidney angiogenesis during development and WT1 mutants such as DDS(R384W) are associated with the Denys-Drash syndrome (DDS), characterized by renal abnormalities. Recent mechanistic studies have demonstrated that the WT1(A) isoform binds VEGF promoter sequences and transcriptionally regulates VEGF reporter constructs. However, regulation of VEGF is complex, involving both transcriptional and post-transcriptional processes. This study examined the ability of hormone and Actinomycin D treatment to alter VEGF mRNA levels in stably transfected WT-LNCaP, DDS-LNCaP, or V-LNCaP prostate cancer cells. The rationale of this study was based on a previous finding that enhancement of VEGF expression in DDS-LNCaP cells occurred only in the presence of the androgen analog, R1881. One possible explanation for these results was that DDS-WT1 stabilized VEGF mRNA so that it accumulated to higher levels. This hypothesis was tested by treating engineered LNCaP cells with Actinomycin D (Act D) and then measuring VEGF mRNA levels by quantitative real-time PCR. The combined effects of WT1 or DDS(R384W) and hormone were tested in these message stability assays and also in transcription assays of transiently transfected LNCaP cells. The results indicated that DDS-WT1 is unable to regulate VEGF transcription or stabilize VEGF mRNA in LNCaP prostate cancer cells. However our observations are also consistent with wild-type WT1(A) having both transcriptional and post-transcriptional effects on VEGF mRNA levels in the presence of hormone. These studies of VEGF regulation by WT1 and dysregulation by DDS(R384W) suggest an important role for WT1 in both normal and tumor-related angiogenesis.

Up‐regulation of vascular endothelial growth factor in synovial fibroblasts from human temporomandibular joint by hypoxia

Enhanced expression of vascular endothelial growth factor (VEGF) has been described in patients with internal derangement (ID). Herein, we examined the expression of VEGF in synovial fibroblasts from temporomandibular joint (TMJ) under hypoxia and investigated the regulation of hypoxia-inducible factor-1alpha (HIF-1alpha) involved in the expression of VEGF. Synovial fibroblasts were prepared from human TMJ. These cells were incubated under hypoxia or normoxia for the indicated time periods. VEGF levels in cultured supernatant were measured by an ELISA. VEGF mRNA isoforms and stability were assessed using RT-PCR and Northern blot analysis respectively. HIF-1alpha accumulation was evaluated by Western blotting and immunofluorescence. VEGF were significantly induced by hypoxia in synovial fibroblasts. In response to hypoxia, VEGF121 and VEGF165 mRNA were both remarkably increased, while there was no change in VEGF mRNA stability. The accumulation and nuclear translocation of HIF-1alpha occurred under hypoxia. Hypoxia may mainly induce the expression of VEGF121 and VEGF165 in synovial fibroblasts to promote inflamed angiogenesis of TMJ. HIF-1alpha, which is clearly activated in response to hypoxia, may control the expression of VEGF in synovial fibroblasts from TMJ.

VEGF gene expression is regulated post‐transcriptionally in macrophages

The macrophage is critical to the innate immune response and contributes to human diseases, including inflammatory arthritis and plaque formation in atherosclerosis. Vascular endothelial growth factor (VEGF) is an angiogenic cytokine that is produced by macrophages. To study the regulation of VEGF production in macrophages we show that stimulation of monocyte-macrophage-like RAW-264.7 cells by lipopolysaccharide (LPS) increases expression of VEGF mRNA and protein. Three alternative splicing VEGF mRNA isoforms are produced, and the stability of VEGF mRNA increases following cellular activation. To study post-transcriptional regulation of the VEGF gene the 3'-untranslated region (3' UTR) was introduced into the 3' UTR of the luciferase gene in a reporter construct. In both RAW-264.7 cells and thioglycollate-elicited macrophages, the 3' UTR sequence dramatically reduces reporter expression. Treatment with activators of macrophages, including LPS, lipoteichoic acid, and VEGF protein, stimulates expression of 3' UTR reporters. Finally, mapping studies of the 3' UTR of VEGF mRNA show that deletion of the heterogeneous nuclear ribonucleoprotein l binding site affects basal reporter expression in RAW-264.7 cells, but does not affect reporter activation with LPS. Together these results demonstrate that a post-transcriptional mechanism contributes to VEGF gene expression in activated macrophage cells.

Functional Polymorphisms in the Vascular Endothelial Growth Factor Gene Are Associated with Development of End-Stage Renal Disease in Males

This study elucidates the genetic role of vascular endothelial growth factor (VEGF) as a predisposing factor for progression of chronic kidney disease. Single-nucleotide polymorphisms were genotyped and haplotype structures were determined in the 3' untranslated region (UTR) of VEGF gene, and the distribution of each haplotype in male patients with ESRD (n=101) and healthy male control subjects (n=189) was examined. The 936C/T and 1451C/T polymorphisms in the 3' UTR were in nearly absolute linkage disequilibrium, and haplotype analysis demonstrated that they were the primary responsible single-nucleotide polymorphisms. The distribution of the 936CC-1451CC genotype was significantly more frequent among patients with ESRD than among the age-matched healthy control subjects. In addition to case-control association study, the 936CC-1451CC genotype was also associated with significantly higher plasma VEGF levels in healthy individuals, but a significant association was found only in males, not in females. We also examined the effect of the 936C-1451C haplotype on mRNA stability. Consistent with the results of plasma VEGF levels, mRNA carrying 936C-1451C haplotype showed higher stability. The 936CC-1451CC genotype in the 3' UTR showed not only susceptibility for ESRD but also higher plasma VEGF levels and mRNA stability, indicating the contribution of VEGF to chronic kidney disease progression, especially in males.

Triamcinolone Acetonide Destabilizes VEGF mRNA in Müller Cells under Continuous Cobalt Stimulation

To identify the molecular mechanism of steroid-induced downregulation of vascular endothelial growth factor (VEGF) synthesis in Müller cells. Confluent cultures of human Müller cells (MIO-M1) were treated with 100 microM CoCl(2), 1 microg/mL triamcinolone acetonide (TA), or both. VEGF secretion was measured with respect to time by ELISA. VEGF mRNA quantity and stability were analyzed by reverse transcriptase-polymerase chain reaction. The activity of hypoxia-inducible factor (HIF)-1 was measured by the relative binding of HIF-1 protein to the hypoxia response element (HRE), by gel shift and ELISA. The HIF-1alpha protein level was determined with Western blot. TA decreased VEGF secretion by at least 50% in the presence of continuous cobalt stimulus. VEGF mRNA decreased 50- to 100-fold 6 hours after treatment with TA and cobalt compared with cobalt alone. VEGF mRNA stability was decreased in cobalt-stimulated, TA-treated cells compared with cobalt alone in cells synchronized by exposure to actinomycin D. HIF-1alpha protein level was sustained for the entire 24-hour treatment period and partitioned into nuclear, not cytosolic, fractions. HIF-1 activity was decreased by 20% to 30% in the presence of TA and cobalt compared with cobalt alone. TA may decrease VEGF synthesis by nongenomic destabilization of VEGF mRNA in cobalt-stimulated Müller cells. There was little effect on the total HIF-1alpha protein level, HIF-1 partitioning, and HIF-1 activity.

Cell-specific but p53-independent Regulation of Vascular Endothelial Growth Factor Expression by Interferons in Human Glioblastoma Cells

Vascular endothelial growth factor (VEGF) is a key mediator of tumor angiogenesis. Interferons (IFNs) have been widely used in the treatment of malignant or recurrent gliomas with only marginal benefit. The association between IFNs and VEGF expression remains unclear and should be an intensively investigated subject. The present study therefore examined the effects of different types of IFNs on VEGF expression in human T98G, A172 and U251 glioblastoma cells by quantitative RT-PCR and ELISA. Both type I (alpha, beta) and type II (gamma) IFNs upregulated VEGF expression in a cell-specific but p53-independent manner. Actinomycin D experiments demonstrated that IFNs did not alter VEGF mRNA stability. In contrast, induction of VEGF mRNA by IFNs was blocked by the protein synthesis inhibitor cycloheximide. Interestingly, cycloheximide also blocked IFN-induced activation of the p44/p42 mitogen-activated protein kinase, which was partially required for induction of VEGF by IFNs. These findings suggest that VEGF might be an indirect target gene of IFNs, and might provide insights into therapeutic applications of IFNs against angiogenesis-dependent tumors.

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This study elucidates the genetic role of vascular endothelial growth factor (VEGF) as a predisposing factor for progression of chronic kidney disease. Single-nucleotide polymorphisms were genotyped and haplotype structures were determined in the 3′ untranslated region (UTR) of VEGF gene, and the distribution of each haplotype in male patients with ESRD (<i>n</i> = 101) and healthy male control subjects (<i>n</i> = 189) was examined. The 936C/T and 1451C/T polymorphisms in the 3′ UTR were in nearly absolute linkage disequilibrium, and haplotype analysis demonstrated that they were the primary responsible single-nucleotide polymorphisms. The distribution of the 936CC-1451CC genotype was significantly more frequent among patients with ESRD than among the age-matched healthy control subjects. In addition to case-control association study, the 936CC-1451CC genotype was also associated with significantly higher plasma VEGF levels in healthy individuals, but a significant association was found only in males, not in females. We also examined the effect of the 936C-1451C haplotype on mRNA stability. Consistent with the results of plasma VEGF levels, mRNA carrying 936C-1451C haplotype showed higher stability. The 936CC-1451CC genotype in the 3′ UTR showed not only susceptibility for ESRD but also higher plasma VEGF levels and mRNA stability, indicating the contribution of VEGF to chronic kidney disease progression, especially in males.