Kawasaki disease on PDGF expression and VSMC proliferation

The effect of serum of patients with Kawasaki disease (KD) on expression of platelet-derived growth factor (PDGF) B chain protein in vascular endothelial cells (VEC) was studied by immunocytochemical method. Meanwhile, the effects of the endothelial cell conditioned media (ECM) on expression of PDGF receptor mRNA in vascular smooth muscle cells (VSMC) and on cell cycle of VSMC were investigated by the methods of nucleic acid hybridization and flow cytometry (FCM). The results showed that the serum of patients with KD induced the expression of PDGF-B chain protein significantly. ECM significantly promoted the expression of PDGF receptor mRNA and induced the proliferation of VSMC. These data suggest that the activation of PDGF-PDGF receptor may play a role in the pathogenesis of coronary complication of KD.

Gene transfer and kidney disease

There is little doubt that molecular biological intervention therapy has come of age and its potential is arousing tremendous excitement. A gene transfer technique, the HVJ-liposome method, is now applicable as a tool for the dissection of molecular aspects in the pathophysiology of renal diseases, and for gene therapy in experimental glomerulonephritis. Overexpressed transforming growth factor (TGF)-beta in the normal rat glomeruli, by gene transfer of TGF-beta cDNA, leads to glomerulosclerosis. However, inhibition of the TGF-beta action by antisense oligonucleotides can suppress the development of the experimental glomerulonephritis. We investigated whether in vivo gene transfer of chimeric proteins, composed of the extracellular domain of TGF-beta type II receptor fused with IgC-Fc, suppresses experimental glomerulonephritis. The expression of TGF-beta in glomeruli was suppressed and so was the extracellular matrix expansion. Taken together with clinical observation of up-regulation of TGF-beta in various glomerulopathies, the dys-regulation of the TGF-beta is important in the development of glomerulosclerosis, and manipulation of this overexpression may prove a novel therapeutic approach for slowing the progression of the disease.

Strain-responsive regions in the platelet-derived growth factor-A gene promoter

Proliferation of cultured neonatal vascular smooth muscle (VSM) cells is enhanced by exposure to cyclic mechanical strain, in part through autocrine action of secreted platelet-derived growth factor (PDGF). We examined transcription factors and DNA response elements that may participate in the induction of PDGF-A gene transcription by mechanical strain. PDGF-A mRNA increased gradually over 4 to 24 hours exposure to cyclic (1 Hz) strain. This was due, at least in part, to increased transcription since a full length (890 bp) PDGF-A promoter reporter construct was induced 3.5-fold in transfected VSM cells exposed to strain for 24 hours. A series of PDGF-A promoter truncation reporter constructs was used to identify potential regions of the promoter involved in regulation by strain. Strain-responsive regions were found between -262 bp and -92 bp and between -92 bp and -41 bp of the promoter. Since these regions are GC-rich and contain response elements for Egr-1 and Sp-1, we examined expression of these transcription factors in response to strain. mRNA for both factors increased over 0.5 to 4 hours of strain, while protein expression for both increased gradually over a 24 hours period. Gel shift assays with a probe specific for Egr-1 demonstrated at least 1 prominent new shifted band after 4 to 12 hours exposure to strain. An Sp-1 probe demonstrated constitutive shifted bands that did not change in response to strain. Thus, GC-rich regions in the proximal 92 bp of the PDGF-A promoter contain mechanical strain-responsive elements that bind Egr-1 and possibly Sp-1.

[Targeting the gene for platelet-derived growth factor A-chain (PDGF-A) and preparation of chimeric mice with a "knockout" genome]

A vector was selected for homologous recombination to generate mouse embryonic stem cell clones with disrupted platelet-derived growth factor A (PDGF-A) chain gene. A chimeric mouse with targeted PDGF-A gene has been created.

A cyclic peptide analogue of loop III of PDGF-BB causes apoptosis in human fibroblasts

A cyclic peptide analogue of platelet-derived growth factor-BB (PDGF-BB), P1 [77IVRKK81-C-73RKIE76], has recently been shown to inhibit specifically [125I]PDGF-BB/receptor binding, and PDGF-BB-induced DNA synthesis in cells expressing PDGF receptors. Here we demonstrate that P1 induces apoptosis in exponentially growing human fibroblasts as confirmed by characteristic changes in cell and nuclear morphology, by TUNEL staining and by flow cytometry. Following incubation with P1 (100 microM), the percentage of cells exhibiting DNA fragmentation increased from 24% after 8 h to 76% after 28 h as exponentially growing cells progressed through the cell cycle. We conclude from these findings taken together that apoptosis accounts for the major proportion of P1-induced cell death. Omission of the Cys residue from P1 or replacement by Ser did not alter the potency of the peptide confirming that peptide dimerisation is not important for its activity. PDGF-BB, EGF, FGF, thrombin and foetal bovine serum were not able to rescue cells from the effects of P1. P1 is a useful tool for investigation of the balance of cellular proliferation/apoptosis in wound healing, atherosclerosis and restenosis, and constitutes a basis from which to design compounds with greater potency.

Sequences of exon 6 and the adjacent intron boundaries of the rat platelet-derived growth factor A-chain gene: implications for alternative splicing

Platelet-derived growth factor (PDGF) is a potent stimulator of vascular smooth muscle cell growth. Two isoforms of PDGF A-chain mRNA that either include (long form) or exclude (short form) exon 6 are produced as a result of alternative splicing in mouse, rabbit, and human. The short form of PDGF A-chain is expressed in both resting and activated cells, while the long form is present predominantly in activated cells. Reverse transcription-polymerase chain reaction analysis with primers encompassing exon 6 revealed the presence of both long- and short-form PDGF A-chain transcripts in rat vascular smooth muscle cells. The nucleotide sequences of exon 6 and its intron boundaries were determined from rat vascular smooth muscle cell cDNA and rat leukocyte genomic DNA. Translation of the long form of PDGF A-chain mRNA was shown to terminate in the 70-base pair exon 6. Conserved sequences that may contribute to the regulation of alternative RNA splicing were identified in intron 5.

Expression in lung carcinomas of platelet-derived growth factor and its receptors

Platelet-derived growth factor (PDGF) is synthesized and secreted by mesenchymal cells. We used immunohistochemistry and in situ hybridization to determine whether immunoreactivity for PDGF and PDGF receptor (PDGF-R) might be a prognostic indicator in lung carcinoma. We compared these results with those of immunohistochemistry for anti-proliferating cell nuclear antigen (anti-PCNA). Indirect immunohistochemistry and in situ hybridization were performed for PDGF B-chain, PDGF-R beta and PCNA antibodies, and PDGF B mRNA on frozen, paraffin-embedded sections of 92 surgically resected lung carcinomas (39 squamous cell carcinomas, 47 adenocarcinomas, 2 large-cell carcinomas, 2 adenosquamous carcinomas, and 2 double carcinomas). Clinicopathologic data (sex, age, stage, survival period, histologic type, and degree of cell differentiation) were evaluated using a statistical analysis system. PDGF reactivity was positive in tumor cell cytoplasm in some cases of squamous cell carcinoma (64%) and adenocarcinoma (55%) and in all cases of large-cell carcinoma, adenosquamous carcinoma, and double carcinoma. PDGF-R reactivity was detected only in tumor stroma. Positive PDGF staining was associated with a poor prognosis in patients with lung carcinoma, independent of age, sex, stage, and degree of cell differentiation (risk ratio = 2.53, p = 0.03). PDGF B mRNA was detected in 100% of PDGF-positive squamous cell carcinomas and in 85% of adenocarcinomas. There was no correlation between PDGF expression and PCNA index in lung carcinomas. Together, these results suggest that immunohistochemistry for PDGF B-chain may predict the outcome for lung carcinoma patients.

Effect of phenotype on the transcription of the genes for platelet-derived growth factor (PDGF) isoforms in human smooth muscle cells, monocyte-derived macrophages, and endothelial cells in vitro

Proliferation of arterial smooth muscle cells (ASMCs) contributes considerably to enlargement of the arterial wall during atherosclerosis. The platelet-derived growth factor (PDGF) is a well-known mitogen and chemoattractant for ASMCs. Quantitative reverse transcription-polymerase chain reaction showed that cells appearing in atherosclerotic lesions, such as ASMCs, endothelial cells, and monocytes/macrophages, expressed mRNAs for both PDGF A and B chains in vitro, with the highest expression in endothelial cells. On proliferation, ASMCs and endothelial cells upregulated PDGF A mRNA. Differentiation of macrophages increased the amount of both mRNAs. Thus, the regulation of PDGF A- and B-chain expression depends on cell types and phenotypic states of the cells, which have also been found in vivo in human atherosclerotic lesions. PDGF A can be produced as short and long isoforms. The latter binds with high affinity to glycosaminoglycans. Irrespective of phenotype, only the minor part of total PDGF A mRNA consisted of the long variant in ASMCs, while endothelial cells produced 40% of total PDGF A as the long form. The differentiation of macrophages increased the production of the long PDGF A mRNA from 10% to 40%. Thus, increasing numbers of stimulated cells in the atherosclerotic lesion may increase the transcription of PDGF isoforms, and particularly of the long PDGF A isoform. Together with increasing amounts of ASMC-derived proteoglycans in developing lesions, this may contribute to accumulation of PDGF in the arterial wall matrix, resulting in prolonged stimulation of ASMCs.

The EWS-WT1 translocation product induces PDGFA in desmoplastic small round-cell tumour

Chromosomal translocations resulting in chimaeric transcription factors underlie specific malignancies, but few authentic target genes regulated by these fusion proteins have been identified. Desmoplastic small round-cell tumour (DSRT) is a multiphenotypic primitive tumour characterized by massive reactive fibrosis surrounding nests of tumour cells. The t(11;22)(p13;q12) chromosomal translocation that defines DSRT produces a chimaeric protein containing the potential transactivation domain of the Ewing-sarcoma protein (EWS) fused to zinc fingers 2-4 of the Wilms tumour suppressor and transcriptional repressor WT1 (refs 2,3). By analogy with other EWS fusion products, the EWS-WT1 chimaera may encode a transcriptional activator whose target genes overlap with those repressed by WT1 (ref. 4). To characterize its functional properties, we generated osteosarcoma cell lines with tightly regulated inducible expression of EWS-WT1. Expression of EWS-WT1 induced the expression of endogenous platelet-derived growth factor-A (PDGFA), a potent secreted mitogen and chemoattractant whose promoter contains the many potential WT1-binding sites. Native PDGFA was not regulated by wild-type WT1, indicating a difference in target gene specificity between this tumour suppressor and its oncogenic derivative. PDGFA was expressed within tumour cells in primary DSRT specimens, but it was absent in Wilms tumours expressing WT1 and Ewing sarcomas with an EWS-Fli translocation. We conclude that the oncogenic fusion of EWS to WT1 in DSRT results in the induction of PDGFA, a potent fibroblast growth factor that contributes to the characteristic reactive fibrosis associated with this unique tumour.

Effects of OPC-21268, a vasopressin V1-receptor antagonist, on expression of growth factors from glomeruli in spontaneously hypertensive rats

To assess the chronic in vivo effects of OPC-21268, a vasopressin-V1 receptor antagonist, on renal injury, we investigated the mRNA expressions of platelet-derived growth factor (PDGF) B-chain, transforming growth factor (TGF)-beta1 and proliferating cell nuclear antigen (PCNA) in the glomeruli of spontaneously hypertensive rats (SHR) treated with OPC-21268 for 3 weeks. SHR aged 10 weeks were given 2% NaCl in drinking water for 3 weeks. The OPC group was fed a 0.5% OPC-21268-containing diet for 3 weeks and the control group was given a normal diet. There were no significant changes in the time course of systolic blood pressure, heart rate, urine volume, or urinary sodium, protein and N-acetyl-beta-glucosaminidase (NAG) excretion between the two groups. Serum electrolytes, protein and creatinine levels also did not differ between the groups. The mRNA expressions of PDGF B-chain, TGF-beta1 and PCNA in the glomerulus were examined using reverse transcriptase-polymerase chain reaction (RT-PCR) methods. The mRNA expressions of PDGF B-chain and PCNA among these were significantly suppressed in the OPC group. No significant differences in renal histology including the organ weights were found between the two groups; however, the glomerular size tended to be enlarged in the OPC group. These findings suggest that chronic V1-receptor blockade directly inhibits the glomerular proliferative injury of salt-loaded SHR at the established hypertension stage.

The tax protein of human T-cell leukemia virus type 1 mediates the transactivation of the c-sis/platelet-derived growth factor-B promoter through interactions with the zinc finger transcription factors Sp1 and NGFI-A/Egr-1

Transcriptional up-regulation of the c-sis/platelet-derived growth factor-B (PDGF-B) proto-oncogene by the Tax protein of human T-cell leukemia virus type 1 has been implicated as one possible mechanism of cellular transformation by human T-cell leukemia virus type 1. In previous work, we identified an essential site in the c-sis/PDGF-B promoter, Tax-responsive element 1 (TRE1), necessary for transactivation by Tax. We also identified Sp1, Sp3, and NGFI-A/Egr-1 as the primary nuclear transcription factors binding to TRE1 which mediate Tax responsiveness. In the present work, we have investigated the mechanism(s) whereby Tax transactivates the c-sis/PDGF-B proto-oncogene. In vitro transcription assays showed that Tax was able to significantly increase the transcriptional activity of a template containing the -257 to +74 region of the c-sis/PDGF-B promoter. Electrophoretic mobility shift assay analysis showed that Tax increased the DNA binding activity of both Sp1 and NGFI-A/Egr-1 using a TRE1 probe. Analysis of Tax mutants showed that two mutants, IEXC29S and IEXL320G, were unable to significantly transactivate the c-sis/PDGF-B promoter. Finally, co-immunoprecipitation analysis revealed that Tax is able to stably bind to both Sp1 and NGFI-A/Egr-1. Interestingly, co-immunoprecipitation analysis also revealed that Tax mutant IEXC29S is unable to interact with NGFI-A/Egr-1, whereas Tax mutant IEXL320G is able to interact with NGFI-A/Egr-1.

Alveogenesis failure in PDGF-A-deficient mice is coupled to lack of distal spreading of alveolar smooth muscle cell progenitors during lung development

PDGF-A(−/−) mice lack lung alveolar smooth muscle cells (SMC), exhibit reduced deposition of elastin fibres in the lung parenchyma, and develop lung emphysema due to complete failure of alveogenesis. We have mapped the expression of PDGF-A, PDGF receptor-alpha, tropoelastin, smooth muscle alpha-actin and desmin in developing lungs from wild type and PDGF-A(−/−) mice of pre- and postnatal ages in order to get insight into the mechanisms of PDGF-A-induced alveolar SMC formation and elastin deposition. PDGF-A was expressed by developing lung epithelium. Clusters of PDGF-Ralpha-positive (PDGF-Ralpha+) mesenchymal cells occurred at the distal epithelial branches until embryonic day (E) 15.5. Between E16.5 and E17.5, PDGF-Ralpha+ cells multiplied and spread to acquire positions as solitary cells in the terminal sac walls, where they remained until the onset of alveogenesis. In PDGF-A(−/−) lungs PDGF-Ralpha+ cells failed to multiply and spread and instead remained in prospective bronchiolar walls. Three phases of tropoelastin expression were seen in the developing lung, each phase characterized by a distinct pattern of expression. The third phase, tropoelastin expression by developing alveolar SMC in conjunction with alveogenesis, was specifically and completely absent in PDGF-A(−/−) lungs. We propose that lung PDGF-Ralpha+ cells are progenitors of the tropoelastin-positive alveolar SMC. We also propose that postnatal alveogenesis failure in PDGF-A(−/−) mice is due to a prenatal block in the distal spreading of PDGF-Ralpha+ cells along the tubular lung epithelium during the canalicular stage of lung development.

Antisense oligodeoxynucleotide complementary to platelet-derived growth factor A-chain messenger RNA inhibits the arterial proliferation in spontaneously hypertensive rats without altering their blood pressures

OBJECTIVE

To evaluate the effects of the antisense oligodeoxynucleotide (ODN) to platelet-derived growth factor (PDGF) A-chain messenger RNA (mRNA) on the growth of cardiovascular organs in hypertension.

DESIGN

15-Mer antisense ODN complementary to the initiation codon region of rat PDGF-A chain mRNA and non-sense ODN of identical proportion but with a random order of bases relative to that of antisense ODN were synthesized with a DNA synthesizer.

METHODS

We examined the effects of the antisense ODN on the growth of vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats, and on the expression of PDGF A-chain mRNA by reverse transcription and polymerase chain reaction and PDGF A-chain protein by Western blot analysis in vitro. We evaluated the distribution of 32P-labeled antisense ODN and examined the effects of the antisense ODN on the growth of cardiovascular organs in vivo.

RESULTS

The antisense ODN reduced the basal DNA synthesis of VSMC from SHR significantly, but did not do so in cells from Wistar-Kyoto rats. Mutations in the antisense ODN sequence reduced the ODN-induced inhibition of DNA synthesis. Addition of serum or transforming growth factor-beta 1 increased the DNA synthesis in the SHR-derived VSMC that was inhibited by the antisense ODN. The antisense ODN inhibited the production of PDGF A-chain protein, but not of the PDGF A-chain mRNA. The injection of 32P-antisense ODN in vivo led to a greater accumulation of radioactivity in the aorta than in other organs. Infusion of antisense ODN for 28 days did not alter the systolic blood pressure appreciably in rats of either strain. However, in SHR, it reduced markedly the elevated DNA content, [3H]-thymidine uptake, and incorporation of [3H]-thymidine into aortic DNA, and suppressed the production of aortic PDGF A-chain protein. These results indicated that the PDGF A-chain is involved in the exaggerated growth of VSMC from SHR by which inhibition of the translation of PDGF A-chain mRNA to the protein with antisense ODN occurs in vitro, and that antisense ODN to PDGF A-chain suppresses the exaggerated arterial proliferation in SHR without altering the high blood pressure in vivo.

CONCLUSION

These results imply that inhibition of the final responsible growth factor PDGF A-chain by antisense ODN can suppress the arterial proliferation in hypertension without altering the blood pressure, suggesting that the arterial proliferation in hypertension is independent of the high blood pressure in part, and that antisense therapy could be feasible for treating hypertension.

Egr-1 is activated in endothelial cells exposed to fluid shear stress and interacts with a novel shear-stress-response element in the PDGF A-chain promoter

Exposure of vascular endothelial cells to fluid mechanical forces can modulate the expression of many genes involved in vascular physiology and pathophysiology. Here, we report that platelet-derived growth factor (PDGF) A-chain gene expression is induced at the level of transcription in cultured bovine aortic endothelial cells exposed to a physiologic level of steady laminar shear stress (10 dyn/cm2). 5' Deletion analysis of the human PDGF-A promoter revealed that a GC-rich region near the TATA box was required for shear-inducible reporter gene expression. This element conferred shear inducibility onto a heterologous promoter-reporter construct that was otherwise unresponsive to shear stress. The induction of PDGF-A expression by shear was preceded by rapid and transient induction in the expression of the immediate-early gene, egr-1, which binds to GC-rich sequences. Gel shift studies indicated that shear-induced Egr-1 bound to the proximal PDGF-A promoter in a specific and time-dependent manner, displacing Sp1 from their overlapping recognition elements. Overlapping consensus binding sites for Egr-1 and Sp1 also appear in the proximal promoters of several other endothelial genes, including transforming growth factor-beta 1 and tissue factor, whose expression is modulated by shear stress. These findings define the Egr-1 binding site in the proximal PDGF-A promoter as a shear-stress-responsive element and suggest that shear-stimulated Egr-1 gene expression may be a unifying theme in the induction of various other endothelial genes exposed to biomechanical forces.

The increased level of PDGF-A contributes to the increased proliferation induced by mechanical stimulation in osteoblastic cells

Mechanical stimulation can prompt healing of bone fractures. However, it is largely unknown how osteogenesis is promoted by mechanical stimulation. In this study, we found that mechanical strain-induced proliferation of osteoblastic cells (MC3T3-E1) accompanied increased levels of platelet-derived growth factor-A (PDGF-A) mRNA, determined by quantitative reverse transcription/polymerase chain reaction. In addition, neomycin and W-7, which blocked mechanical strain-induced proliferation of the osteoblast cells, also blocked mechanical stimulation-induced elevation of PDGF-A mRNA. Finally, an antibody against PDGF can inhibit physical stimulation-induced proliferation of MC3T3-E1 cells, suggesting that the increased MC3T3-E1 cells produced by mechanical stimulation at least partially depends on the increased activity of PDGF.

Role of long-form PDGF A-chain in the growth of vascular smooth muscle cells from spontaneously hypertensive rats

Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit exaggerated growth relative to cells from normotensive Wistar-Kyoto (WKY) rats. Platelet-derived growth factor (PDGF) A-chain has been implicated in the exaggerated growth of VSMC from SHR. Two isoforms of PDGF A-chain mRNA that either include (long form) or exclude (short form) exon 6 are produced as a result of alternative splicing. The expression of the long-form PDGF A-chain at the mRNA level and its role in the growth of VSMC from SHR have now been investigated with the use of an antisense oligodeoxynucleotide (ODN) complementary to exon 6 of the PDGF A-chain gene. Reverse transcription-polymerase chain reaction (RT-PCR) analysis with primers encompassing exon 6 of PDGF A-chain mRNA revealed bands corresponding to both long- and short-form PDGF A-chain transcripts in quiescent VSMC from both SHR and WKY rats, with the long-form mRNA more abundant in VSMC from SHR than in cells from WKY rats. Expression of the long-form of PDGF A-chain mRNA was enhanced with angiotensin II and transforming growth factor-beta1 in VSMC from SHR, but not in cells from WKY rats. The antisense ODN significantly inhibited DNA synthesis by VSMC from SHR, but not by cells from WKY rats, in the absence or presence of serum. In addition, the antisense ODN significantly inhibited serum induced proliferation of VSMC from SHR, but not those from WKY rats. The antisense ODN abolished expression of the long-form PDGF A-chain mRNA in VSMC, suggesting that its inhibitory effects on the growth of VSMC from SHR are mediated by depletion of the long-form transcripts. These results indicate that the long-form of PDGF A-chain contributes to the exaggerated growth of VSMC from SHR.

Gene expression and specific binding of platelet-derived growth factor and its effect on DNA synthesis in human decidual cells

To clarify the biological significance of platelet-derived growth factor (PDGF) in human decidual cell function, which is important for the maintenance of pregnancy, we investigated gene expression of the PDGF subunits, PDGF-A and PDGF-B, specific binding of the PDGF isoform, and the effect of PDGF dimers on DNA synthesis in human decidual cells. We detected in decidua from early pregnancy the expected DNA bands of PDGF-A and PDGF-B by reverse transcriptase-polymerase chain reaction (RT-PCR) as well as mRNAs of each PDGF subunit by Northern blot hybridization, demonstrating that both PDGF subunits exist in this tissue. Scatchard plot analysis showed that decidual cells had both PDGF-alpha and PDGF-beta receptors. PDGF-AA, -AB and -BB stimulated [3H]-thymidine incorporation in cultured decidual cells in a dose-dependent manner. These results indicate the importance of PDGF in human decidua.

Vascular endothelial growth factor is essential for initial but not continued in vivo growth of human breast carcinoma cells

In this study, we used a self-contained tetracycline-regulated retroviral vector system to elucidate the role of vascular endothelial growth factor (VEGF) in controlling s.c. growth of human T-47D breast carcinoma cells. VEGF expression was tightly regulated by this system, both in vitro and in nude mouse xenografts. A 2.4-fold increase in tumor volume was associated with VEGF overexpression. Tumor growth was almost completely inhibited when VEGF was suppressed from the time of T-47D cell inoculation, and a 6-fold reduction in tumor volume was observed when VEGF suppression was started in 175-mm3 tumors. However, no growth inhibition was observed when VEGF suppression was started in 820-mm3 tumors. In these tumors, basic fibroblast growth factor and transforming growth factor alpha RNA expression was detected after VEGF was switched off. These findings demonstrate that VEGF is critical for the initial s.c. growth of T-47D breast carcinoma cells, whereas other angiogenic factors can compensate for the loss of VEGF after the tumors have reached a certain size.

Abeta deposition is associated with neuropil changes, but not with overt neuronal loss in the human amyloid precursor protein V717F (PDAPP) transgenic mouse

The PDAPP transgenic mouse overexpresses human amyloid precursor protein V717F (PDAPP minigene) and develops age-related cerebral amyloid-beta protein (Abeta) deposits similar to senile plaques in Alzheimer's disease. We find age-related cortical and limbic Abeta deposition that begins at 8 months and progresses to cover 20-50% of the neuropil in cingulate cortex, entorhinal cortex, and hippocampus of 18-month-old heterozygotic animals. The regional patterns of transgene expression and amyloid deposition suggest that Abeta deposits occur at the terminals of overexpressing neurons. Amyloid deposition is associated with dystrophic neurites and extensive gliosis. However, stereological analysis shows that there is no overt neuronal loss in entorhinal cortex, CA1 hippocampal subfield, or cingulate cortex through 18 months of age. In addition, there is no apparent loss of mRNA encoding neuronal synaptic, cytoskeletal, or metabolic proteins. Thus, widespread Abeta deposition in 18-month-old heterozygotic mice produces neuritic alterations and gliosis without widespread neuronal death.

Angiotensin-converting enzyme inhibition abolishes medial smooth muscle PDGF-AB biosynthesis and attenuates cell proliferation in injured carotid arteries: relationships to neointima formation

BACKGROUND

ACE inhibitors can attenuate the development of intimal fibrocellular lesions after balloon catheter vessel injury, but the mechanisms responsible are unknown.

METHODS AND RESULTS

To evaluate how basic fibroblast growth factor (FGF-2) and the platelet-derived growth factor (PDGF) isoforms are affected by ACE inhibition in injured rat carotid arteries in relation to smooth muscle cell (SMC) proliferation, we examined the effects of oral perindopril on FGF-2 and PDGF isoform levels in carotid arteries 2 days after balloon catheter injury. [3H]Thymidine incorporation into medial and intimal SMCs was also assessed. Uninjured vessels contained two forms of FGF-2, with molecular weights of 18 and 22 kD, and PDGF-AA. Two days after injury, FGF-2 and PDGF-AA levels were markedly reduced, but high levels of PDGF-AB became apparent when the SMCs were proliferating. Perindopril completely abolished the biosynthesis of PDGF-AB but had little effect on residual FGF-2. This was accompanied by a 25% reduction in medial SMC proliferation. Neointimal cell proliferation 10 days after injury was unaffected by perindopril, although neointima size was reduced by 30%. Commencing perindopril treatment 4 days after the injury confirmed that early events associated with effects on medial SMCs were the major contributors to the attenuated neointimal lesions.

CONCLUSIONS

The ability of ACE inhibitors such as perindopril to attenuate neointima formation and growth in balloon catheter-injured rat carotid arteries is dependent on early events in the media, the inhibition of SMC PDGF-AB biosynthesis and attenuation of proliferation. Neointima formation in similarly injured vessels containing SMCs that are either unresponsive to PDGF-AB or exhibit an ACE-independent profile of growth factor biosynthesis responses may account for the ineffectiveness of ACE inhibition in some species.

Phenotypic characterization of cytokine expression in patients with IgA nephropathy

To identify the cytokines that play a relevant role in the pathogenesis of IgA nephropathy, we analyzed and compared the gene expression of proinflammatory cytokines, immuno-regulatory cytokines, and growth factors in peripheral blood mononuclear cells (PBMC). Expression of IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-6, IL-10, IL-12, IFN-gamma, TGF-beta, TNF-alpha, and PDGF was examined in 28 patients with IgA nephropathy (IgAN), 20 patients with non-IgA mesangial proliferative glomerulonephritis (mesPGN), and 19 healthy controls. Compared with healthy controls, a significant number of IgAN and mesPGN patients showed increased expression of IL-1 beta, IL-4, IL-10, IL-12, and IFN-gamma. The cytokine profile of renal tissue of 10 IgAN and 5 mesPGN biopsies was simultaneously analyzed and compared with that of PBMC. The proinflammatory IL-1 alpha and growth factor PDGF-B were expressed more in renal tissues than in PBMC. Furthermore, the renal profile of IL-alpha, IFN-gamma, and TNF-alpha expression was associated with the expression of IFN-gamma in PBMC. The serum level of IFN-gamma of IgAN correlated significantly (P = 0.0003) with that of IL-12, suggesting a potential role for cross-stimulation. More importantly, expression of IFN-gamma in PBMC and the elevated serum level correlated with the decline in glomerular filtration rate (P = 0.0012) and severity of renal histopathologic grade. To elucidate the role of leukocytes in renal cytokine expression, surface markers of T cells (CD3), monocytes (CD14), natural killer cells (CD16), and B cells (CD19) were also examined in renal tissues. The prominent renal expression of CD3, CD14, and CD16 implicates the leukocytes as the major source of proinflammatory cytokines in IgAN. Collectively, these findings indicate that IFN-gamma plays a prominent role in an interactive network of cytokines that contribute to the pathogenesis and progression of IgA nephropathy.

c-sis/platelet-derived growth factor-B promoter requirements for induction during the 12-O-tetradecanoylphorbol-13-acetate-mediated megakaryoblastic differentiation of K562 human erythroleukemia cells

Platelet-derived growth factor (PDGF), a powerful mitogen and chemoattractant, is composed of two subunits, A and B, which are synthesized by normal megakaryocytes. We have studied the transcriptional regulation of the c-sis/PDGF-B gene in human K562 erythroleukemia cells that have been induced to undergo megakaryoblastic differentiation by treatment with 12-O-tetradecanoylphorbol-13-acetate. Upon differentiation of these cells, c-sis/PDGF-B transcription is increased 50-100-fold. We show here that a minimal c-sis/PDGF-B promoter region, spanning nucleotides -64 to +6, retains full inducibility. Linker scanning mutagenesis within this minimal region identified four segments that were important for expression in differentiating K562 cells: a previously defined sis proximal element (SPE; -64 to -45), the TATA box, the 10 bp immediately downstream of the TATA box [TATA neighboring sequence (TNS); -24 to -15], and the mRNA start site region. Combined mutation of the SPE and TNS resulted in a greater impairment of induction than did mutation of either sequence alone. In contrast, combined mutation of the SPE and the start site or of the TNS and the start site did not lower induction beyond that displayed by the least inducible single mutants. The combination of the SPE and the TNS was sufficient to confer wild-type levels of inducibility to a heterologous promoter. Both the SPE and the TNS were sensitive to alterations in the helical spacing between these elements and the TATA box. Using the electrophoretic mobility shift assay, we demonstrated binding of Sp family members and of two additional unidentified nuclear factors to the TNS in both 12-O-tetradecanoylphorbol-13-acetate-treated and untreated cells. The TNS, therefore, appears to represent a target for a constitutively bound factor(s) that is required for cooperation with a differentiation-specific factor bound at the SPE to drive efficient c-sis/PDGF-B transcription in TPA-treated K562 cells.