Platelet-derived Growth Factor A-chain Research Articles

Preparation of Dopamine Nanoparticles and Its Application in the Treatment of Neonatal Scleredema

The polydopamine (PDA) nanoparticles were prepared by the aqueous phase oxidation, and doxorubicin (DOX) was applied on surface of PDA under appropriate temperature and Pondus Hydrogenii (pH) conditions. The human umbilical vein-derived mesenchymal stem cells (hUV-MSCs) were sub-cultured, and then destroyed by lysing and freeze-thaw to obtain the stem cell membrane (SSM) fragments, which were squeezed using the polycarbonate porous membrane and then wrapped in the surfaces of the PDA nanoparticles by means of water bath ultrasound. In this way, the biomimetic nano medicine was synthesized. In the experiment, the DOX release amount of the nanomedicine under different conditions was analyzed. Under the precondition that the concentration of the drug was changed, and it was used to explore proliferation activity of human esophageal cancer cell (Eca-109). Mice with sclerosed skin caused by scleredema were selected as the test subjects to observe the inhibitory effect of the prepared drugs on its fibrosis. In addition, 90 cases of neonatal scleredema were selected and grouped to verify the improvement effect of nano-medicine injection on their symptoms. The results relaved that average particle size (APS) of synthesized drug was 77.6±8.5 nm, and the drug loading of DOX loaded on the surface of PDA was 18.4%. The transmission electron microscopy (TEM) displayed that surface of prepared drug was structured with cell membrane, and the release of DOX was correlated with the pH of the drug solution. Under the condition of a certain DOX concentration, the prepared nano-drug could kill the Eca-109 cells strongly (P < 0.05). In the sclerosing phase, the skin thickness and collagen index of the mice could be reduced by injecting different doses of the drug solutions (P < 0.05), while the content of transforming growth factor β (TGF-β)/platelet-derived growth factor A-chain (PDGFA) was decreased (P < 0.05). The severity score of newborn children was greatly reduced after drug injection treatment; and the temperature recovery time, sclerosis disappearance time, and hospitalization time were shortened to a great extent (P < 0.05).

Characterization of platelet-derived growth factor-A expression in mouse tissues using a lacZ knock-in approach.

Expression of the platelet-derived growth factor A-chain gene (Pdgfa) occurs widely in the developing mouse, where it is mainly localized to various epithelial and neuronal structures. Until now, in situ mRNA hybridization (ISH) has been the only reliable method to identify Pdgfa expression in tissue sections or whole mount preparations. Validated protocols for in situ detection of PDGF-A protein by immunohistochemistry is lacking. In particular, this has hampered understanding of Pdgfa expression pattern in adult tissues, where ISH is technically challenging. Here, we report a gene targeted mouse Pdgfa allele, Pdgfaex4 COIN, which is a combined conditional knockout and reporter allele. Cre-mediated inversion of the COIN cassette inactivates Pdgfa coding while simultaneously activating a beta-galactosidase (lacZ) reporter under endogenous Pdgfa transcription control. The generated Pdgfaex4 COIN-INV-lacZ allele can next be used to identify cells carrying a Pdgfa null allele, as well as to map endogenous Pdgfa expression. We evaluated the Pdgfaex4 COIN-INV-lacZ allele as a reporter for endogenous Pdgfa expression patterns in mouse embryos and adults. We conclude that the expression pattern of Pdgfaex4 COIN-INV-lacZ recapitulates known expression patterns of Pdgfa. We also report on novel embryonic and adult Pdgfa expression patterns in the mouse and discuss their implications for Pdgfa physiology.

Induction of progressive glomerulonephritis by podocyte-specific overexpression of platelet-derived growth factor-D

Platelet-derived growth factor-D (PDGF-D), normally expressed in podocytes, mediates mesangial cell proliferation in vivo. To study this further, we created transgenic mice with podocyte-specific overexpression of PDGF-D. Hemizygous mice were grossly indistinguishable from wild-type littermates through 11 months of age; however, hemizygous mice older than 4 weeks commonly exhibited increased cell proliferation within the glomerular tuft. Many hemizygous mice also developed widespread segmental glomerulosclerosis and focal extracapillary proliferation with fibrin/fibrinogen deposition, extensive tubulointerstitial damage, proteinuria, and renal insufficiency. Electron microscopy found focal foot process effacement. Renal mRNA expression of podocin and nephrin, as well as the number of glomerular WT-1-positive cells, were significantly reduced in hemizygous compared to wild-type mice, indicating loss and/or dedifferentation of podocytes. PDGF-A, -B, and both PDGF receptor chain mRNAs, fibronectin, type IV collagen, RANTES, MCP-1, and CCR-2 mRNAs were all increased in the renal cortex of PDGF-D transgenic mice. Only 8.5% of newborn mice were homozygous overexpressors exhibiting a mortality rate of 37% at 4 weeks. Thus, podocyte-specific overexpression of PDGF-D caused mesangioproliferative disease, glomerulosclerosis, and crescentic glomerulonephritis. Hence, podocyte-specific growth factor overexpression can induce paracrine mesangial cell proliferation upstream of the filtration flow.

Monocyte, macrophage and mast cell-derived PDGF control inflammation, tissue remodelling and autoimmunity in the pathophysiology of Graves’ ophthalmpathy

Methods Expression of PDGF family members was determined by RQ-PCR, Western Blot and immunohistochemistry in GO and control orbital tissue. The effect of PDGF-AA, PDGFAB and PDGF-BB was determined on OF proliferation, IL-6 production and hyaluronan production. Moreover, the effect of PDGF on TSHR expression by OF and their subsequent susceptibility for Graves’ Disease immunoglobulins (GD-IgG) was determined. Results PDGF-A and PDGF-B chains were increased in GO orbital tissue. Immunohistochemistry revealed that this was due to production by monocytes, macrophages and mast cells. PDGF induced proliferation, cytokine production and hyaluronan production by OF. Furthermore, PDGF increased TSHR expression on OF and enhanced their susceptibility to TSH and GD-IgG with regard to IL-6 and hyaluronan production. These effects of TSH and GD-IgG were inhibited by a cAMP inhibitor and by a TSHR blocking antibody, suggesting involvement of TSHR signaling. Remarkably, PDGF-BB has the most pronounced effect on OF, while PDGF-AA showed the least effect. Conclusion

Krüppel-like Factor 5 Shows Proliferation-specific Roles in Vascular Remodeling, Direct Stimulation of Cell Growth, and Inhibition of Apoptosis

Krüppel-like factor 5 (KLF5), originally isolated as a regulator of phenotypic modulation of vascular smooth muscle cells, induces pathological cell growth and is expressed in the neointima. Although induction of KLF5 up-regulates growth factors like platelet-derived growth factor-A chain, how KLF5 actually contributes to vascular remodeling, notably its direct effects on cell proliferation, had been poorly clarified. To investigate the effects of KLF5 on neointimal formation, we at first performed adenoviral overexpression of KLF5 to rats subjected to carotid balloon injury. Neointimal formation and proliferating cell nuclear antigen-positive rate were significantly increased at 14 days after injury in the KLF5-treated animals. At the cellular level, overexpression of KLF5 also resulted in markedly increased cell proliferation and cell cycle progression. As a molecular mechanism, we showed that KLF5 directly bound to the promoter and up-regulated gene expression of cyclin D1, as well as showing specific transactivation of cyclins and cyclin-dependent kinase inhibitors in cardiovascular cells. Conversely, knockdown of KLF5 by RNA interference specifically down-regulated cyclin D1 and impaired vascular smooth muscle cell proliferation. Furthermore, KLF5 attenuated cleavage of caspase-3 under conditions of apoptotic stimulation. Moreover, KLF5-administered animals exhibited a significant decrease in terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling-positive cells in the medial layer, suggesting inhibition of apoptosis in the early phase after denudation. These findings collectively suggest that KLF5 plays a central role in cardiovascular pathologies through direct and specific stimulation of cell growth as well as inhibition of apoptosis.

Expression of platelet-derived growth factors and their receptors in ovarian clear-cell carcinoma and its putative precursors

Recent studies have shown that platelet-derived growth factors and their receptors are frequently co-expressed in ovarian cancers. Herein, we investigated the role of the platelet-derived growth factor pathway in the development of ovarian clear-cell adenocarcinoma, a highly chemoresistant form of ovarian cancer. Immunohistochemical expression of platelet-derived growth factor receptor-α and receptor-β, platelet-derived growth factor A-chain and B-chain was examined in 31 cases of clear-cell adenocarcinoma and 56 coexisting putative precursor lesions: 17 non-atypical and 19 atypical endometrioses, and 10 non-atypical and 10 atypical clear-cell adenofibroma components. Twenty-one solitary endometrioses were also examined. Vascular endothelial cells were always positive for all the markers examined, and were used as positive controls. The frequencies of positivity for platelet-derived growth factor receptor-α and receptor-β, and platelet-derived growth factor A-chain increased in accordance with higher cytologic atypia in the putative precursors: 71, 47, and 59% in the 17 non-atypical endometrioses, 84, 73, and 84% in the 19 atypical endometrioses, 0% each in the 10 non-atypical clear-cell adenofibromas, 100, 90, and 90% in the 10 atypical clear-cell adenofibromas, and 97, 97, and 100% in the 31 clear-cell adenocarcinomas, respectively. Positivity for platelet-derived growth factor B-chain increased in accordance with increased atypia in clear-cell adenofibroma: 0% in non-atypical clear-cell adenofibromas, 30% in atypical clear-cell adenofibromas, and 60% in coexisting carcinomas. However, in contrast, positivity for platelet-derived growth factor B-chain decreased in accordance with increased atypia in endometriosis coexisting with clear-cell adenocarcinomas: 35% in non-atypical endometrioses, 11% in atypical endometrioses, and 5% in coexisting carcinomas. Platelet-derived growth factor receptor-α and receptor-β, and their ligands A-chain and B-chain were positive in 14, 29, 19, and 62% of the solitary endometrioses, respectively. These results indicate activation of the platelet-derived growth factor pathway in ovarian clear-cell adenocarcinomas and suggest biological differences between carcinomas that arise in association with clear-cell adenofibroma vs endometriosis.

Cardiovascular Remodeling and Metabolic Abnormalities in SHRSP.Z-Leprfa/IzmDmcr Rats as a New Model of Metabolic Syndrome

The purpose of this study was to evaluate whether the spontaneously hypertensive rat SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP fatty) is a useful animal model to clarify molecular mechanisms that underlie metabolic syndrome. We investigated histopathologic changes in the cardiovascular organs and metabolic characteristics of SHRSP fatty rats, which are congenic rats from a cross between SHRSP and Zucker fatty (ZF) rats. The aortic wall and cardiac, carotid, and renal arteries from SHRSP and SHRSP fatty rats were thicker than those of ZF rats. The renal cortex in SHRSP and SHRSP fatty rats showed severe glomerulosclerosis. Pancreatic islands in SHRSP fatty and ZF rats showed marked hyperplasia. Steady-state plasma glucose concentrations were higher in SHRSP fatty than in ZF rats. Non-fasting triglyceride levels in SHRSP fatty rats were higher than in ZF rats. DNA synthesis in cultured vascular smooth muscle cells (VSMCs) from SHRSP fatty and SHRSP rats was significantly higher than that in VSMCs from Wistar-Kyoto (WKY) or ZF rats. Levels of platelet-derived growth factor A-chain and transforming growth factor-beta1 mRNAs were higher in VSMCs from SHRSP fatty and SHRSP than from ZF rats. Microarray analysis identified five genes that were significantly upregulated and four genes that were significantly downregulated in visceral adipose tissue of SHRSP fatty rats compared with levels in control strains (SHRSP and ZF rats). These findings suggest that the combination of hypertension and obesity accelerates vascular remodeling, dyslipidemia, and insulin resistance in metabolic syndrome. The phenotype of SHRSP fatty is similar to that of human metabolic syndrome, and therefore, studies of these rats may help clarify the molecular mechanisms that underlie metabolic syndrome in humans.

Abstract 125: Proteome Analysis of a Regulatory Pathway of Pathologic Vascular Injury as Mediated by KLF5 and its Transcriptional Complexes

Background: Transcription factor Krüppel-like factor 5 (KLF5) is a key element linking external stress and cardiovascular remodeling by up-regulating platelet derived growth factor (PDGF)-A chain gene activity. However, the underlying mechanisms remain to be elucidated. The unambiguous and comprehensive identification of interacting proteins is crucial for understanding these mechanisms. In the present study, we identified interacting factors of KLF5 by proteomic analysis and characterized their regulation in the vascular pathogenic response. Methods&Results: Double-stranded oligonucleotide containing the binding sequence for KLF5 in the PDGF-A promoter was synthesized and attached to metal beads, to which cell nuclear extract was applied. SDS-PAGE visualized specific bands to the sequence, which were subjected to in-gel digestion and peptide mass fingerprinting by MALDI-TOF/MS spectrometry. Factors that are known to be important in the DNA damage/repair pathway were successively identified. We therefore examined the involvement of the complex in vascular pathologies. Double-strand break as determined by immunohistochemistry using γ-H2AX antibody, a marker of activation of the double-stranded DNA damage/repair response, was observed in pathogenically stimulated vascular endothelial cells (HUVEC) and neointimal tissues in rat carotid artery balloon injury model. Further, KLF5 was shown to mediate the response on γ-H2AX as shown by co-immunoprecipitation and confocal microscopy. Discussion: We show a hitherto unknown regulatory mechanism by DNA double-strand break/repair system involving KLF5 in the vascular pathogenic response. Our findings might provide a clue to understanding the initiation of pathological cell proliferation observed in atherosclerosis or restenosis after coronary intervention. This new pathway might also be a tempting target for therapeutic intervention aimed at modulating the activity of KLF5 upon PDGF-A chain and its associated pathologies in the cardiovascular system.

Podagra, Uric Acid, and Cardiovascular Disease

Hippocrates would not be surprised to read that persons with gout had higher mortality, and particularly cardiovascular-related mortality, than persons without gout.1 On the other hand, he might well have been bemused, nearly 2500 years after he described the syndrome, that this made news. Article p 894 He should not have been. All too often, rigorous examination debunks conventional wisdom. Reassuringly, in this case, Drs Choi and Curhan found evidence to support long-standing belief. These dedicated and productive students of the pathogenesis and natural history of gout have here reported empiric data from the 51 000 male nonphysician health professionals who participated in the Health Professions Follow-up Study. From initial examination in 1986 through nearly 600 000 person-years of follow-up, 5825 deaths occurred, of which 2132 were cardiovascular and 1576 were ascribed to coronary heart disease, rates that attest to the generally good health of the group. The ≈6% prevalence of gout, at baseline, in men in their mid-50s, who mirror the general US population in body mass index, reported history of hypertension, hypercholesterolemia, and diabetes mellitus, was higher than expected. Interim biennial questionnaires identified incident cases of gout. Participants with gout were both more likely to report coronary heart disease (CHD) at baseline and, regardless of CHD status, more likely than gout-free persons to have cardiovascular disease (CVD) risk factors. Results were presented after stratification by CHD status at baseline. As expected, the incidence of all-cause and CHD mortality was much greater in those with than in those without prevalent CHD. The adjusted increased relative risk of those with gout (compared with those without) for all-cause, CVD, and CHD mortality was ≈25%. The single exception was a near doubling of increased relative risk of CHD mortality among those free of CHD at baseline. Neither the inclusion of incident …

Immunohistochemical detection of insulin‐like growth factors, platelet‐derived growth factor, and their receptors in ameloblastic tumors

To evaluate the roles of growth factors in oncogenesis and cytodifferentiation of odontogenic tumors, expression of insulin-like growth factors (IGFs), platelet-derived growth factor (PDGF), and their receptors was analyzed in ameloblastic tumors as well as in tooth germs. Tissue specimens of 10 tooth germs, 47 ameloblastomas, and five malignant ameloblastic tumors were examined immunohistochemically with the use of antibodies against IGF-I, IGF-II, IGF-I receptor (IGF-IR), PDGF A-chain, PDGF B-chain, PDGF alpha-receptor, and PDGF beta-receptor. Immunohistochemical reactivity for IGFs, PDGF chains, and their receptors was detected predominantly in odontogenic epithelial cells near the basement membrane in tooth germs and in benign and malignant ameloblastic tumors. The expression levels of IGF-II and PDGF chains were significantly higher in ameloblastic tumors than in tooth germs. Malignant ameloblastic tumors showed higher reactivity for PDGF chains than benign ameloblastomas and higher reactivity for platelet-derived growth factor receptors than tooth germs. The expression levels of PDGF chains were significantly higher in follicular ameloblastomas than in plexiform ameloblastomas. Desmoplastic ameloblastomas showed higher expression of IGFs and IGF-IR when compared with other ameloblastoma subtypes. Expression of IGFs, PDGF, and their receptors in tooth germs and ameloblastic tumors suggests that these growth factor signals contribute to cell proliferation or survival in both normal and neoplastic odontogenic tissues. Expression of these molecules in odontogenic tissues possibly affects interactions with the bone microenvironment during tooth development and intraosseous progression of ameloblastic tumors. Altered expression of the ligands and receptors in ameloblastic tumors may be involved in oncogenesis, malignant potential, and tumor cell differentiation.

Stent-Based Delivery of Antisense Oligodeoxynucleotides Targeted to the PDGF A-Chain Decreases In-Stent Restenosis of the Coronary Artery

Although the use of drug-eluting stents (DESs) has been shown to limit neointima hyperplasia, currently available DESs may adversely affect reendothelialization, possibly precipitating cardiac events. We evaluated the effect of an antisense oligodeoxynucleotide (ODN) targeted to the platelet-derived growth factor (PDGF) A-chain on in-stent restenosis in pig coronary artery. A bare metal stent coated with phosphorothioate-linked antisense ODN or nonsense ODN, or a bare metal stent without ODN (control), was implanted in the mid segment of the left anterior descending artery (LAD). Twenty-eight days after implantation, angiography and intravascular ultrasound (IVUS) were performed, the LAD was removed, and stenosis was evaluated pathologically. Volumetric stenosis ratios were 64 +/- 11.9, 44 +/- 3.4, and 26 +/- 3.8% in coronary arteries implanted with control, nonsense ODN-coated, and antisense ODN-coated stents, respectively. In angioscopic findings, the lumen surface was smooth in the stented segments in all groups. Struts of antisense ODN-coated stents were observed embedded in the neointima, whereas embedding was not observed in nonsense ODN-coated stents or control stents, indicating a decrease in hyperplasia in response to antisense ODN treatment. Pathologic findings showed 77 +/- 5.8, 68 +/- 12.2, and 38 +/- 5.3% stenosis in coronary arteries implanted with control stents, nonsense ODN-coated stents, and antisense ODN-coated stents, respectively. A continuous lining of endothelial cells was observed along the lumen of coronary arteries implanted with antisense ODN-coated stents. Stent-based delivery of an antisense ODN targeted to the PDGF A-chain effectively inhibits neointima formation after stent implantation in pig coronary artery by suppressing VSMC hyperplasia and preserving endothelialization. Antisense-ODNs may provide a therapy for in-stent restenosis of the coronary artery.

Aggrecan expression is substantially and abnormally upregulated in Hutchinson–Gilford Progeria Syndrome dermal fibroblasts

Hutchinson–Gilford Progeria syndrome (HGPS) is a rare genetic disorder that displays features of segmental aging. It is manifested predominantly in connective tissue, with most prominent histological changes occurring in the skin, cartilage, bone and cardiovascular tissues. Detailed quantitative real time reverse-transcription polymerase chain reaction studies confirmed the previous observation that platelet-derived growth factor A-chain transcripts are consistently elevated 11 ± 2- to 13 ± 2-fold in two HGPS dermal fibroblast lines compared with age-matched controls. Furthermore, we identified two additional genes with substantially altered transcript levels. Nucleotide pyrophosphatase transcription was virtually shut down with decreased expression of 13 ± 3- to 59 ± 3-fold in HGPS, whereas aggrecan mRNA was elevated to 24 ± 5 times to 41 ± 4 times that of chronologically age-matched controls. Aggrecan, normally a component of cartilage and not always detectable in normal fibroblasts cultures, was secreted by HGPS fibroblast lines and was produced as a proteoglycan. This demonstrates that elevated aggrecan expression and its secretion are aberrant features of HGPS. We conclude that HGPS cells can display massively altered transcript levels leading to the secretion of inappropriate protein species.

Development of Gene Therapies for Cardiovascular and Renal Diseases by Nucleic Acid Medicines

Nucleic acid medicines such as antisense DNA, antisense peptide nucleic acid (PNA), ribozyme, and decoy are expected to be novel therapeutic strategy for sever diseases which are resistant to present therapy. We have developed antisense DNA, antisense PNA and ribozyme targeting platelet-derived growth factor (PDGF) A-chain and transforming growth factor-beta1 (TGF-beta1) for arterial proliferative diseases such as coronary artery stenosis after angioplasty or stent implantation, hypertensive vascular diseases and atherosclerosis, and progressive renal diseases. Antisense DNA to PDGF A-chain inhibited arterial growth in spontaneously hypertensive rats without lowering blood pressure and inhibited the neointima formation of pig coronary artery after stent implantation. Ribozymes to PDGF A-chain and TGF-beta1 specifically inhibited the target transcripts and prevented the neointima formation. Ribozymes to TGF-beta1 improved renal damages in hypertensive rats. These nucleic acid medicines targeting PDGF A-chain and TGF-beta1 will be feasible gene therapies for the arterial proliferative diseases and progressive renal diseases. Pyrrole-imidazole polyamides are novel gene silencing compound, which bind to minor grove of double strand DNA by base-specific manner to inhibit gene expression. We developed pyrrole-imidazole polyamide to TGF-beta1 and confirmed that the polyamide binds to the TGF-beta1 promoter. The polyamide inhibited TGF-beta1 promoter activity and decreased expression of TGF-beta1 in vitro and in vivo. The polyamide markedly improved the renal injury in hypertensive rats. The pyrrole-imidazole polyamide will be a novel gene silencing agent for cardiovascular and renal diseases.

Ethanol‐Induced Liver Injury: Potential Roles for Egr‐1

Chronic ethanol-induced liver injury follows a typical progression from its earliest stage of steatosis to more advanced injury, characterized by the development of inflammation, hepatocyte necrosis/apoptosis, fibrosis and finally cirrhosis. Kupffer cells, the resident macrophage in the liver, play a critical role in the progression of liver injury. Increased exposure of Kupffer cells to lipopolysaccharide (LPS) during chronic ethanol exposure leads to the production of a number of inflammatory mediators, including tumor necrosis factor alpha (TNF-alpha). Recent evidence indicates that in addition to increased exposure to LPS, Kupffer cells also develop an enhanced sensitivity to LPS after chronic ethanol feeding. We have recently identified early growth response-1 (Egr-1), an immediate-early gene transcription factor, as an important contributor to increased LPS-stimulated TNF-alpha secretion by Kupffer cells after chronic ethanol exposure. In other models of tissue injury, such as ischemia-reperfusion in the lung, Egr-1 acts as a coordinator of the complex response to stress. Here we review the literature regarding the role of EGR-1 in regulation of a number of genes implicated in each of the stages of chronic ethanol-induced liver injury. In addition to the critical role of Egr-1 in generating maximal LPS-stimulated TNF-alpha expression, Egr-1 also controls the expression of a number of inflammatory mediators, including intercellular adhesion molecule (ICAM)-1, monocyte chemotactic protein (MCP)-1 and macrophage inflammatory protein (MIP)-2, as well as genes contributing to fibrosis, such as transforming growth factor (TFG)-beta1, platelet-derived growth factor PDGF-A chain and fibroblast growth factor (FGF). Understanding the contribution of Egr-1 to the expression of genes involved in the development of chronic ethanol-induced liver injury may lead to the development of improved therapies designed to prevent and/or reverse alcohol-induced liver injury.

The Deacetylase HDAC1 Negatively Regulates the Cardiovascular Transcription Factor Krüppel-like Factor 5 through Direct Interaction

Transcription is regulated by a network of transcription factors and related cofactors that act in concert with the general transcription machinery. Elucidating their underlying interactions is important for understanding the mechanisms regulating transcription. Recently, we have shown that Krüppel-like factor KLF5, a member of the Sp/KLF family of zinc finger factors and a key regulator of cardiovascular remodeling, is regulated positively by the acetylase p300 and negatively by the oncogenic regulator SET through coupled interaction and regulation of acetylation. Here, we have shown that the deacetylase HDAC1 can negatively regulate KLF5 through direct interaction. KLF5 interacts with HDAC1 in the cell and in vitro. Gel shift DNA binding assay showed that their interaction inhibits the DNA binding activity of KLF5, suggesting a property of HDAC1 to directly affect the DNA binding affinity of a transcription factor. Reporter assay also revealed that HDAC1 suppresses KLF5-dependent promoter activation. Additionally, overexpression of HDAC1 suppressed KLF5-dependent activation of its endogenous downstream gene, platelet-derived growth factor-A chain gene, when activated by phorbol ester. Further, HDAC1 binds to the first zinc finger of KLF5, which is the same region where p300 interacts with KLF5 and, intriguingly, HDAC1 inhibits binding of p300 to KLF5. Direct competitive interaction between acetylase and deacetylase has been hitherto unknown. Collectively, the transcription factor KLF5 is negatively regulated by the deacetylase HDAC1 through direct effects on its activities (DNA binding activity, promoter activation) and further through inhibition of interaction with p300. These findings suggest a novel role and mechanism for regulation of transcription by deacetylase.

Purα activates PDGF-A gene transcription via interactions with a G-rich, single-stranded region of the promoter

Transcription of the PDGF-A chain gene is regulated by multiple promoter and silencer elements that are GC-rich and exhibit considerable single-stranded character. In this study, the 42 kDa single-stranded DNA and RNA binding protein, Purα, was investigated with respect to its ability to bind and interact functionally with single-stranded DNA elements in the PDGF-A gene. Recombinant GST-Purα bound with high affinity and sequence-specificity to the G-rich strands of two such transcriptional control elements, the 5′-S1 nuclease-hypersensitive silencer (5′SHS; −1418 to −1388) and the nuclease-hypersensitive element (NHE; −92 to −48). Ethylation interference footprinting localized binding of Purα to a region between nucleotides −91 and −77 within the NHE element, which contains binding sites for the double-stranded DNA-binding transcription factors Sp1, EGR-1 and WT1. Forced expression of Purα upregulated transcriptional activity of the PDGF-A promoter but not the 5′SHS silencer in HepG2 cells, demonstrating Purα has the potential to activate PDGF-A gene expression. Targeted disruption of the Purα gene reduced NHE activity and PDGF-A mRNA expression in mouse embryo fibroblasts, consistent with a physiological role for Purα in maintaining optimal transcription of the PDGF-A gene. These results indicate Purα enhances transcription of the PDGF-A gene through its interactions with single-stranded, G-rich strands in the promoter, perhaps by stabilizing non-B-form DNA conformations.

A 5′-distal enhanceosome in the PDGF-A gene is activated in choriocarcinoma cells via ligand-independent binding of vitamin D receptor and constitutive jun kinase signaling

Overexpression of platelet-derived growth factor A-chain (PDGF-A) is clearly linked to autocrine and paracrine stimulation of malignant growth in many human cancers. We have shown previously that PDGF-A overexpression in choriocarcinoma, hepatoma and lung carcinoma cell lines is driven by the activity of a 66 bp enhancer element (ACE66) located approximately 7 kb upstream of the PDGF-A transcription start site. In this study, the ACE66 element is shown to be activated in JEG-3 choriocarcinoma cells through synergistic interactions between consensus DNA motifs for binding of vitamin D receptor, AP1 and ELK1. Binding of the vitamin D/retinoid-X receptor (VDR/RXRalpha) heterodimer to the ACE66 element was reconstituted in vitro with recombinant VDR/RXRalpha and with JEG-3 nuclear extract, and was verified in living JEG-3 cells by chromatin immunoprecipitation analysis. Transcriptional activity of the ACE66 element, as well as occupancy of the element by VDR/RXRalpha, was shown to be independent of stimulation with the hormonal VDR ligand, 1,25-dihydroxyvitamin D3. The jun kinase pathway of mitogen-activated protein kinase (MAPK) signaling was shown to activate the ACE66 enhancer, most likely through activation of factors binding to the AP1 element. These results identify a novel mechanism of transcriptional enhancement involving ligand-independent activity of the VDR/RXR heterodimer and MAPK signaling pathways that appears to play an important role in the overexpression of PDGF in many different settings of human malignancy.

Adenovirus-Encoded Hammerhead Ribozyme to PDGF A-Chain mRNA Inhibits Neointima Formation after Arterial Injury

To develop a strategy for gene therapy of restenosis following coronary angioplasty, we examined the effects of a recombinant adenovirus vector encoding a hammerhead ribozyme specific for rat platelet-derived growth factor (PDGF) A-chain mRNA (Ad.Ribozyme) and a control recombinant adenovirus vector encoding the Escherichia coli LacZ gene (Ad.LacZ) on neointima formation in rat carotid artery after balloon injury. Ad.Ribozyme (10⁸ PFU/ml) markedly reduced the increased expression of PDGF A-chain mRNA and protein. Ad.Ribozyme significantly decreased the intima/media ratio (68%) of the injured artery, whereas Ad.LacZ had no effect on the intima/media ratio. Most carotid arteries developed thrombi by 14 days after balloon injury, whereas Ad.Ribozyme completely inhibited thrombus formation. Expression of thromboxane A₂ (TXA₂) receptor mRNA was significantly increased after balloon injury. Ad.Ribozyme significantly decreased the levels of TXA₂ receptor. Expression of prostaglandin I₂ (PGI₂) synthase mRNA was significantly decreased after balloon injury. Ad.Ribozyme significantly increased levels of PGI₂ synthase mRNA after balloon injury. The observation that adenovirus-encoded ribozyme to PDGF A-chain inhibits neointima formation may serve as a novel strategy to prevent restenosis after coronary angioplasty. Inhibition of growth factors by genetic approaches may yield new insights into the mechanisms underlying responses to vascular injury and lead to new therapeutic applications.

Regulation of Platelet-derived Growth Factor-A Chain by Krüppel-like Factor 5 : NEW PATHWAY OF COOPERATIVE ACTIVATION WITH NUCLEAR FACTOR-κB

The transcription factor Krüppel-like factor 5 (KLF5) and its genetically downstream target gene platelet-derived growth factor-A (PDGF-A) chain are key factors in regulation of cardiovascular remodeling in response to stress. We show that KLF5 mediates a novel distinct delayed persistent induction of PDGF-A chain in response to the model agonist, phorbol ester, through a cis-element previously shown to mediate phorbol ester induction on to PDGF-A chain through the early growth response factor (Egr-1). Interestingly, the nuclear factor-kappaB (NF-kappaB) p50 subunit further cooperatively activates PDGF-A chain through protein-protein interaction with KLF5 but not Egr-1. RNA interference analysis confirmed that KLF5 and p50 are important for induction of PDGF-A chain. Collectively, we identify a novel regulatory pathway in which PDGF-A chain gene expression, under the control of KLF5, is cooperatively activated by the NF-kappaB p50 subunit and a pathophysiological stimulus.

Effects of antisense peptide nucleic acid to platelet-derived growth factor A-chain on growth of vascular smooth muscle cells.

To investigate antisense peptide nucleic acid (PNA) as a gene therapy for the arterial proliferative diseases, the authors designed and examined the effects of an antisense PNA targeting platelet-derived growth factor (PDGF) A-chain on expression of PDGF A-chain and growth of vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats. A 15-mer antisense PNA complementary to the initiation codon of rat and human PDGF A-chain mRNA was synthesized and purified by high-performance liquid chromatography. Gel-shift assay and biomolecular interaction analysis (BIAcore) revealed that the antisense PNA bound weakly to the target RNA, whereas it bound strongly to the target DNA. Fluorescein-isothiocyanate-labeled antisense PNA to PDGF A-chain was taken up slowly and maintained in VSMCs for a prolonged period of time. Antisense PNA inhibited expression of PDGF A-chain mRNA and protein as well as DNA synthesis in VSMCs in a dose-independent manner. Inhibition of DNA synthesis by the antisense PNA was greater than that by the antisense DNA at a low concentration (0.5 micromol/L). These results suggest that antisense PNA to PDGF A-chain will be used as a gene therapy for vascular proliferative diseases such as hypertensive vascular diseases, restenosis of coronary arteries after angioplasty, and atherosclerosis.