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

Development of a novel gene silencer pyrrole-imidazole polyamide targeting human connective tissue growth factor

Pyrrole-imidazole (PI) polyamide can bind to specific sequences in the minor groove of double-helical DNA and inhibit transcription of the genes. We designed and synthesized a PI polyamide to target the human connective tissue growth factor (hCTGF) promoter region adjacent to the Smads binding site. Among coupling activators that yield PI polyamides, 1-[bis(dimethylamino)methylene]-5-chloro-1H-benzotriazolium 3-oxide hexafluorophosphate (HCTU) was most effective in total yields of PI polyamides. A gel shift assay showed that a PI polyamide designed specifically for hCTGF (PI polyamide to hCTGF) bound the appropriate double-stranded oligonucleotide. A fluorescein isothiocyanate (FITC)-conjugated PI polyamide to CTGF permeated cell membranes and accumulated in the nuclei of cultured human mesangial cells (HMCs) and remained there for 48 h. The PI polyamide to hCTGF significantly decreased phorbol 12-myristate acetate (PMA)- or transforming growth factor-β1 (TGF-β1)-stimulated luciferase activity of the hCTGF promoter in cultured HMCs. The PI polyamide to hCTGF significantly decreased PMA- or TGF-β1-stimulated expression of hCTGF mRNA in a dose-dependent manner. The PI polyamide to hCTGF significantly decreased PMA- or TGF-β1-stimulated levels of hCTGF protein in HMCs. These results indicate that the developed synthetic PI polyamide to hCTGF could be a novel gene silencer for fibrotic diseases.

Stent-based delivery of antisense oligodeoxynucleotides targeted to the PDGF A-chain decreases in-stent restenosis of the coronary artery

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Synthetic pyrrole-imidazole polyamide inhibits expression of the human transforming growth factor-beta1 gene

Pyrrole-imidazole (Py-Im) polyamides can bind to the predetermined base pairs in the minor groove of double-helical DNA with high affinity. These synthetic small molecules can interfere with transcription factor-DNA interaction and inhibit or activate the transcription of corresponding genes. In the present study, we designed and synthesized a Py-Im polyamide to target -545 to -539 base pairs of human transforming growth factor-beta1 (hTGF-beta1) promoter adjacent to the fat-specific element 2 (FSE2) to inhibit the expression of the gene. Gel mobility shift assay showed that the synthetic Py-Im polyamide binds to its corresponding double-strand oligonucleotides, whereas the mismatch polyamides did not bind. Fluorescein isothiocyanate-labeled Py-Im polyamide was detected in the nuclei of human vascular smooth muscle cells (VSMCs) after 2- to 48-h incubation. Py-Im polyamide significantly decreased the promoter activity of hTGF-beta1 determined by in vitro transcription experiments and luciferase assay. In cultured human VSMCs, Py-Im polyamide targeting hTGF-beta1 promoter significantly inhibited expressions of hTGF-beta1 mRNA and protein. These results indicate that the synthetic Py-Im polyamide designed to bind hTGF-beta1 promoter inhibited hTGF-beta1 gene and protein expression successfully. This novel agent will be used for the TGF-beta-related diseases as a gene therapy.

A role for platelet-derived growth factor beta-receptor in a newborn rat model of endothelin-mediated pulmonary vascular remodeling

Newborn rats exposed to 60% O2 for 14 days develop endothelin (ET)-1-dependent pulmonary hypertension with vascular remodeling, characterized by increased smooth muscle cell (SMC) proliferation and medial thickening of pulmonary resistance arteries. Using immunohistochemistry and Western blot analyses, we examined the effect of exposure to 60% O2 on expression in the lung of receptors for the platelet-derived growth factors (PDGF), which are implicated in the pathogenesis of arterial smooth muscle hyperplasia. We observed a marked O2-induced upregulation of PDGF-alpha and -beta receptors (PDGF-alphaR and -betaR) on arterial smooth muscle. This led us to examine pulmonary vascular PDGF receptor expression in 60% O2-exposed rats given SB-217242, a combined ET receptor antagonist, which we found prevented the O2-induced upregulation of PDGF-betaR, but not PDGF-alphaR, on arterial smooth muscle. PDGF-BB, a major PDGF-betaR ligand, was found to be a potent in vitro inducer of hyperplasia and DNA synthesis in cultured pulmonary artery SMC from infant rats. A critical role for PDGF-betaR ligands in arterial SMC proliferation was confirmed in vivo using a truncated soluble PDGF-betaR intervention, which attenuated SMC proliferation induced by exposure to 60% O2. Collectively, these data are consistent with a major role for PDGF-betaR-mediated SMC proliferation, acting downstream of increased ET-1 in a newborn rat model of 60% O2-induced pulmonary hypertension.

PDGF and cardiovascular disease

Platelet-derived growth factor (PDGF) was identified in a search for serum factors that stimulate smooth muscle cell (SMC) proliferation. During the development of lesions of atherosclerosis that can ultimately lead to vessel occlusion, SMC are stimulated by inflammatory factors to migrate from their normal location in the media. They accumulate within the forming lesion where they contribute to lesion expansion by proliferation and deposition of extracellular matrix. Different genetic manipulations in vascular cells combined with various inhibitory strategies have provided strong evidence for PDGF playing a prominent role in the migration of SMC into the neointima following acute injury and in atherosclerosis. Other activities of PDGF identified in vivo suggest additional functions for PDGF in the pathogenesis of cardiovascular disease.

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.

Troglitazone inhibits growth and improves insulin signaling by suppression of angiotensin II action in vascular smooth muscle cells from spontaneously hypertensive rats

Troglitazone, a thiazolizidinedione, has recently been reported to possess anti-arteriosclerotic properties. To evaluate mechanisms underlying the anti-arteriosclerotic effects of troglitazone, we examined the effect of troglitazone on growth, expression of growth factors, and insulin signaling in vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) which produce angiotensin II (Ang II) in a homogeneous culture. Troglitazone inhibited basal and serum-stimulated DNA synthesis and inhibited increases in the number of VSMC from SHR and normotensive Wistar-Kyoto (WKY) rats. Its inhibition was greater in VSMC from SHR. Troglitazone abolished DNA synthesis in response to Ang II in VSMC from both rat strains and markedly inhibited DNA synthesis in response to epidermal growth factor (EGF) and platelet-derived growth factor (PDGF)-AA in VSMC from SHR. Troglitazone did not alter the expression of transforming growth factor (TGF)-beta1, PDGF A-chain, or basic fibroblast growth factor (bFGF) mRNAs in VSMC from WKY rats, but it markedly decreased expression of these growth factor mRNAs in VSMC from SHR. Troglitazone markedly decreased basal and Ang II-stimulated expression of extracellular signal-regulated kinase proteins in VSMC from both rat strains. Troglitazone abolished Ang II-induced suppression of phosphatidilinositol 3-kinase (PI3-kinase) activity, insulin receptor substrate-1 (IRS-1) associated tyrosine phosphorylation, and IRS-1 associated p85 levels in VSMC from WKY rats. Basal PI3-kinase activity, tyrosine phosphorylation of IRS-1, and IRS-1 associated p85 levels were lower in VSMC from SHR than in cells from WKY rats. Troglitazone significantly increased PI3-kinase activity, IRS-1 associated tyrosine phosphorylation, and IRS-1 associated p85 levels in VSMC from SHR. These results indicate that troglitazone produce its anti-arteriosclerotic effects through suppression of the action of growth-promoting factors including Ang II, and that troglitazone inhibits Ang II-induced suppression of insulin signaling in VSMC from SHR, suggesting that tissue Ang II may lead to insulin resistance and to arteriosclerosis in hypertension. Troglitazone may be useful in the treatment of insulin resistance as well as of hypertensive vascular diseases.

Growth characteristics, angiotensin II generation, and microarray-determined gene expression in vascular smooth muscle cells from young spontaneously hypertensive rats

BACKGROUND

We have demonstrated that vascular smooth muscle cells (VSMCs) derived from spontaneously hypertensive rats (SHR) show exaggerated growth and produce angiotensin (Ang) II and growth factors. These may reflect intrinsic abnormalities in SHR that are not caused by excessive blood pressure, and are associated with genetic abnormalities.

OBJECTIVE

To evaluate whether these characteristics of VSMCs from SHR are associated with hypertension or genetic factors.

DESIGN AND METHODS

VSMCs were obtained by an explant method from aortas of 4-week-old male SHR/Izumo and Wistar-Kyoto (WKY)/Izumo rats. We evaluated growth characteristics by [3H]thymidine incorporation and cell number increases, immunofluorescence of alpha-smooth muscle (alpha-SM) actin, mRNA expressions of phenotype markers, Ang II-generating system components, and growth factors by reverse transcription and polymerase chain reaction analysis, and Ang II levels by radioimmunoassay in VSMCs. Expression of 850 genes in VSMCs was evaluated by microarray.

RESULTS

VSMCs from young SHR showed increased basal DNA synthesis and higher responses of DNA synthesis and cell numbers in response to calf serum. Ang II was significantly increased in conditioned medium and cell extracts from SHR-derived VSMCs than in those from WKY rat-derived VSMCs. mRNA expression of Ang II-generating proteinases, such as cathepsin D and angiotensin-converting enzyme, was greater in VSMCs from SHRs than in cells from WKY rats. Expression of transforming growth factor-beta1, platelet-derived growth factor A-chain and basic fibroblast growth factor mRNAs was greater in VSMCs from SHRs than in cells from WKY rats. Expression of mRNAs of phenotype markers, such as matrix gamma-carboxyglutamic acid (Gla) and osteopontin, was also greater in VSMCs from SHR than in cells from WYK rats. Microarray study showed that VSMCs derived from young SHR increasingly express genes for many enzymes, adhesion molecules and cytokines.

CONCLUSION

This study determined that VSMCs derived from young SHR show exaggerated growth, produce Ang II and increasingly express several enzymes, adhesion molecules and cytokines, which are independent of hypertension and possibly associated with genetic abnormalities.

Adenovirus-mediated transfer of ribozyme targeting platelet-derived growth factor A-chain mRNA inhibits growth of vascular smooth muscle cells from spontaneously hypertensive rats

Platelet-derived growth factor (PDGF) is a potent stimulator of growth of vascular smooth muscle cells (VSMCs). VSMCs from spontaneously hypertensive rats (SHRs) show exaggerated growth and increasingly express PDGF A-chain messenger RNA (mRNA). To examine adenovirus-mediated transfer of a ribozyme targeting the PDGF A-chain mRNA as a possible gene therapy for vascular proliferative diseases, a recombinant adenovirus vector encoding a ribozyme that targets rat PDGF A-chain mRNA (Ad. ribozyme) was designed and synthesized and its effect on the growth of VSMCs from SHRs was investigated. This vector dose-dependently inhibited DNA synthesis in VMSCs from SHRs, whereas an adenovirus vector encoding the Escherichia coli LacZ gene (Ad. LacZ) did not affect DNA synthesis. Ad. ribozyme significantly suppressed proliferation of VSMCs from SHRs in a dose-dependent manner. Ad. LacZ had no effect. Ad. ribozyme significantly inhibited expression of PDGF A-chain mRNA and PDGF-AA protein in VSMCs from SHRs. Ad. LacZ had no effect. These results demonstrated that adenovirus-mediated transfer of a ribozyme targeting the PDGF A-chain mRNA effectively and specifically inhibited the growth of VSMCs from SHRs with suppression of PDGF A-chain mRNA and PDGF-AA protein expression. Adenovirus-mediated transfer of ribozyme targeting PDGF A-chain mRNA may be a feasible gene therapy for vascular proliferative diseases.

Betaxolol inhibits extracellular signal-regulated kinase and P70S6 kinase activities and gene expressions of platelet-derived growth factor A-chain and transforming growth factor-beta1 in Dahl salt-sensitive hypertensive rats

We evaluated the protective effects of long-term treatment with betaxolol, a specific beta-antagonist, on platelet-derived growth factor (PDGF) A-chain and transforming growth factor (TGF)-beta1 gene expression in the left ventricle of Dahl salt-sensitive hypertensive rats fed a high-salt diet. In addition, we evaluated the relations between these effects and coronary microvascular remodeling, expression of extracellular signal-regulated kinases (ERK) belonging to one subfamily of mitogen-activated protein kinases, and expression of p70S6 kinase belonging to one subfamily of ribosomal S6 kinases. Betaxolol (0.9 mg/kg/day, subdepressor dose) was administered for 5 weeks, from 6 weeks of age to the left ventricular hypertrophy stage at 11 weeks of age. Increased PDGF A-chain and TGF-beta1 mRNA and protein expression were suppressed by betaxolol. Upregulated activities of ERK1/2 and p70S6 kinase phosphorylations were decreased by betaxolol. Betaxolol administration resulted in significant improvements in the wall-to-lumen ratio, perivascular fibrosis and myocardial fibrosis. Thus, we conclude that ERK1/2 and p70S6 kinase activities may play a key role in coronary microvascular remodeling of Dahl salt-sensitive hypertensive rats, and that beneficial effects of betaxolol on cardiovascular remodeling may be at least partially mediated by decreased PDGF A-chain and TGF-beta1 expression in the left ventricle.

Inhibitory effect of a novel angiotensin II type 1 receptor antagonist RNH-6270 on growth of vascular smooth muscle cells from spontaneously hypertensive rats: different anti-proliferative effect to angiotensin-converting enzyme inhibitor

The current study was undertaken to evaluate the anti-proliferative effect of a novel angiotensin II type 1 (AT1) receptor antagonist, RNH-6270, on exaggerated growth of vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR), in comparison with the effects of an angiotensin-converting enzyme (ACE) inhibitor. RNH-6270 and temocapril significantly inhibited basal DNA synthesis in VSMCs from SHRs in a dose-dependent manner, but not in cells from Wistar-Kyoto (WKY) rats. SHR-derived VSMC showed a hyperresponse of DNA synthesis to serum and angiotensin II compared with that of WKY rats-derived VSMC. RNH-6270 did not affect serum-stimulated DNA synthesis in VSMCs from both rat strains. RNH-6270 abolished angiotensin II-stimulated DNA synthesis in VSMC from both rat strains. RNH-6270 significantly inhibited proliferation of VSMC from both rat strains, but the ACE inhibitor temocapril did not exert such an effect. RNH-6270 decreased the specific binding of angiotensin II to VSMC in a competitive manner for angiotensin II receptors in both rat strains. RNH-6270 and temocapril significantly decreased the expression of growth factor mRNAs and proteins in VSMC from SHR, but not in cells from WKY rats. These results suggest that RNH-6270 is a potent AT1 receptor antagonist and has anti-proliferative effects on VSMCs from SHR, which was not seen with an ACE inhibitor. The growth inhibitory effect of RNH-6270 may be associated with the inhibition of growth factors via antagonism to AT1 receptors.

Novel mechanisms of the antiproliferative effects of amlodipine in vascular smooth muscle cells from spontaneously hypertensive rats

The calcium channel blocker amlodipine continues to be of interest due to its potential proven ability to hinder the progression of atherosclerosis and reduce the number of clinical ischemic events. Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) are useful in the study of atherosclerosis because they show exaggerated growth with production of angiotensin II (Ang II) by conversion to the synthetic phenotype. To clarify mechanisms of the antiproliferative effects of amlodipine, we evaluated effects of the expression of growth factors, the changes in phenotype, and the proliferation of VSMC from SHR. Amlodipine significantly inhibited basal DNA synthesis and proliferation of VSMC from SHR. Amlodipine also inhibited expression of platelet-derived growth factor (PDGF) A-chain, transforming growth factor beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF) mRNAs in VSMC from SHR. Decreases in levels of PDGF A-chain and bFGF mRNAs in VSMC from SHR were greater with amlodipine than with nifedipine. Amlodipine significantly inhibited expression of the synthetic phenotype markers osteopontin and matrix Gla mRNAs, indicating that it inhibited the exaggerated growth of VSMC from SHR and suppressed the change from the contractile phenotype to the synthetic phenotype. Thus, amlodipine may be a beneficial therapeutic agent for patients with hypertensive vascular diseases.

Hammerhead ribozyme targeting human platelet-derived growth factor A-chain mRNA inhibited the proliferation of human vascular smooth muscle cells

Platelet-derived growth factor (PDGF) A-chain contributes to the pathogenesis of cardiovascular proliferative diseases, such as hypertensive vascular disease, atherosclerosis, and re-stenosis of an artery after angioplasty. To develop a ribozyme against human PDGF A-chain mRNA as a gene therapy for human arterial proliferative diseases, we designed and synthesized a 38-base hammerhead ribozyme to cleave human PDGF A-chain mRNA at the GUC sequence at nucleotide 591. In the presence of MgCl(2), synthetic hammerhead ribozyme to human PDGF A-chain mRNA cleaved the synthetic target RNA to two RNA fragments at a predicted size. Doses of 0.01-1.0 microM hammerhead ribozyme to human PDGF A-chain mRNA significantly inhibited angiotensin II (Ang II) and transforming growth factor (TGF)-beta(1)-induced DNA synthesis in vascular smooth muscle cells (VSMC) from human in a dose-dependent manner. One micromolor of hammerhead ribozyme to human PDGF A-chain mRNA significantly inhibited Ang II-induced PDGF A-chain mRNA and PDGF-AA protein expressions in VSMC from humans. These results indicate that the designed hammerhead ribozyme to human PDGF A-chain mRNA effectively inhibited growth of human VSMC by cleaving the PDGF A-chain mRNA and inhibiting the PDGF-AA protein expression in human VSMC. This suggests that the designed hammerhead ribozyme to PDGF A-chain mRNA is a feasible gene therapy for treating arterial proliferative diseases.

Effects of the L- and N-type calcium channel blocker cilnidipine on growth of vascular smooth muscle cells from spontaneously hypertensive rats

Cultured vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) show exaggerated growth compared with cells from Wistar-Kyoto (WKY) rats. Calcium antagonists have recently been reported to have an in vivo antiproliferative effect on hypertensive cardiovascular organs. We investigated the effects of the calcium antagonist cilnidipine that blocks both L- and N-type calcium channels on the growth of VSMC from SHR. Cilnidipine (1 and 10 microM) significantly inhibited basal DNA synthesis in VSMC from both rat strains; the inhibition was significantly larger in VSMC from SHR than in cells from WKY rats, and was significantly greater than effects of nifedipine. Cilnidipine (1 microM) significantly inhibited serum-stimulated DNA synthesis in VSMC from both rat strains. The inhibition was more marked in VSMC from SHR than in cells from WKY rats. Angiotensin II, platelet-derived growth factor (PDGF)-AA, and phorbol-12-myristate-13-acetate dose-dependently increased DNA synthesis in VSMC from SHR but not in cells from WKY rats. Cilnidipine (1 microM) significantly suppressed this increase in DNA synthesis in VSMC from SHR. Expression of basic fibroblast growth factor (bFGF), transforming growth factor-beta1, and PDGF A-chain mRNAs was markedly greater in VSMC from SHR than in cells from WKY rats. Cilnidipine (1 microM) significantly inhibited the expression of TGF-beta1 mRNA in VSMC from SHR but not in cells from WKY rats. These findings suggest that cilnidipine exerts its antiproliferative effects through the inhibition of DNA synthesis induced by growth-promoting factors and by inhibiting the expression of TGF-beta1 mRNA in VSMC from SHR.

Inhibition of vascular smooth muscle cell proliferation by DNA-RNA chimeric hammerhead ribozyme targeting to rat platelet-derived growth factor A-chain mRNA

BACKGROUND

Spontaneously hypertensive rats (SHR)-derived vascular smooth muscle cells (VSMC) show exaggerated growth and increasingly express platelet-derived growth factor (PDGF) A-chain mRNA compared to VSMC from normotensive Wistar-Kyoto (WKY) rats.

OBJECTIVE

To investigate the effects of designed DNA-RNA chimeric hammerhead ribozyme to rat PDGF A-chain on exaggerated growth of VSMC from SHR.

DESIGN AND METHODS

We designed and synthesized a 38-base DNA-RNA chimeric hammerhead ribozyme with two phosphorothioate linkages at the 3' terminal to cleave rat PDGF A-chain mRNA at the GUC sequence at nucleotide 921. We confirmed the cleavage activity of designed ribozyme by in vitro cleavage reaction and by lipofectin-mediated transfection of ribozyme into VSMC.

RESULTS

Doses of 0.1 and 1 micromol/l DNA-RNA chimeric ribozyme dose-dependently inhibited basal DNA synthesis in VSMC from SHR. A dose of 1 micromol/l DNA-RNA chimeric ribozyme time-dependently inhibited basal DNA synthesis in VSMC from SHR. However, the same doses of all-RNA ribozyme had no effects on DNA synthesis in VSMC from SHR. Fluorescein isothiocyanate-labeled DNA-RNA chimeric ribozyme was recognized in cytosol at 30 min, and in nucleus at 60 min after lipofectin transfection. A dose of 1 micromol/l DNA-RNA chimeric ribozyme significantly inhibited expressions of both PDGF A-chain mRNA and PDGF-AA protein in VSMC from SHR, but not from WKY rats.

CONCLUSION

These results indicated that the designed DNA-RNA chimeric ribozyme to PDGF A-chain mRNA effectively and specifically inhibited the exaggerated growth of VSMC from SHR at low concentrations, which were mediated by the reduction of PDGF A-chain mRNA and PDGF-AA protein expressions.

Role of endogenous angiotensin II in the increased expression of growth factors in vascular smooth muscle cells from spontaneously hypertensive rats

In culture, vascular smooth muscle cells (VSMC) derived from spontaneously hypertensive rats (SHR) show exaggerated growth compared with cells from normotensive Wistar-Kyoto (WKY) rats. SHR-derived VSMC express higher levels of transforming growth factor (TGF)-beta1, platelet-derived growth factor (PDGF) A-chain, and basic fibroblast growth factor (bFGF) mRNAs than cells from WKY rats. We have recently observed production of angiotensin II (Ang II) in homogeneous cultures of VSMC from SHR. In the current study we investigated the contribution of endogenous Ang II to increased expression of the above-mentioned growth factors in VSMC from SHR. The levels of mRNAs encoding TGF-beta1, PDGF A-chain, and bFGF were determined by reverse transcription-polymerase chain reaction and were much higher in VSMC from SHR than in cells from WKY rats. The basal level of Ang II-like immunoreactivity (LI) in conditioned medium as determined by radioimmunoassay was significantly higher in VSMC from SHR than in cells from WKY rats. Isoproterenol is known to induce angiotensinogen gene significantly increased Ang II-LI in VSMC from both WKY rats and SHR. Isoproterenol also increased angiotensinogen, TGF-beta1, PDGF A-chain, and bFGF mRNAs in VSMC from SHR. An angiotensin-converting enzyme inhibitor delapril significantly decreased Ang II-LI in VSMC from WKY rats and SHR. Delapril considerably decreased the levels of TGF-beta1, PDGF A-chain, and bFGF mRNAs in VSMC from SHR. An Ang II type 1 receptor antagonist CV 11974 decreased the levels of TGF-beta1, PDGF A-chain, and bFGF mRNAs, and the levels of TGF-beta1, PDGF-AA, and bFGF proteins in VSMC from SHR. These findings suggest that increased generation of Ang II is associated with enhanced expression of TGF-beta1, PDGF A-chain, and bFGF, and the increases in the levels of these growth factors by endogenous Ang II may contribute to the exaggerated growth of VSMC from SHR.

Angiotensin II regulates the cell cycle of vascular smooth muscle cells from SHR

We have demonstrated that spontaneously hypertensive rats (SHR)-derived vascular smooth muscle cells (VSMC) show the exaggerated growth and produce angiotensin II (Ang II). In the current study, we investigated the role of endogenous Ang II in the regulation of the cell cycle in VSMC from SHR. Levels of Ang II in conditioned medium from SHR-derived VSMC cultured without serum were significantly higher than levels in conditioned medium from Wistar-Kyoto (WKY) rat-derived VSMC. Basal DNA synthesis was higher in quiescent VSMC from SHR than that in cells from WKY rats. An Ang II type 1 receptor antagonist, CV11974, significantly inhibited the elevation in DNA synthesis in quiescent VSMC from SHR but did not affect it in cells from WKY rats. Cellular DNA content analysis by flow cytometry revealed that the proportion of cells in S phase was higher, whereas the proportion of cells in G1+G0 phase was lower in VSMC from SHR than those in cells from WKY rats. CV11974 significantly decreased the proportion of cells in S phase and correspondingly increased the proportion of cells in G1+G0 phase in VSMC from SHR, but it did not affect the proportion in cells from WKY rats. Cyclin-dependent kinase 2 (CDK2) activity, which is known to induce the progression from G1 to S phase, was higher in VSMC from SHR than in cells from WKY rats. Expression of CDK2 inhibitor p27(kip1) mRNA was markedly higher in VSMC from SHR than in cells from WKY rats. CV11974 decreased expression of p27(kip1) mRNA in VSMC from SHR, whereas CV11974 increased it in cells from WKY rats. These findings indicate that enhanced production of endogenous Ang II regulates the cell cycle especially in the progression from G1 to S phase, and increases CDK2 activity, which is independent of p27(kip1) in VSMC from SHR.

Effect of methylene methylimino linkage of antisense oligonucleotide to the platelet-derived growth factor A-chain on growth of vascular smooth muscle cells from spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR)-derived vascular smooth muscle cells show exaggerated growth and increased expression of platelet-derived growth factor (PDGF) A-chain mRNA. We examined the effect of methylene methylimino linkage of antisense oligodeoxynucleotide, a novel modification of antisense oligodeoxynucleotide designed to increase nuclease resistance, to PDGF A-chain on the exaggerated growth of vascular smooth muscle cells from SHR. Methylene methylimino-linked oligodeoxynucleotide provided complete resistance against S1 nuclease. Methylene methylimino linkage of antisense oligodeoxynucleotide to PDGF A-chain resulted in a rapid inhibition of basal DNA synthesis of vascular smooth muscle cells from SHR. This inhibition was much greater than that produced by phosphorothioate linkage of antisense oligodeoxynucleotide to PDGF A-chain. The methylene methylimino linkage of antisense oligodeoxynucleotide to PDGF A-chain may prove useful in the treatment of arterial proliferative diseases including hypertension.

Low dose of eicosapentaenoic acid inhibits the exaggerated growth of vascular smooth muscle cells from spontaneously hypertensive rats through suppression of transforming growth factor-beta

OBJECTIVE

To evaluate effects of eicosapentaenoic acid (EPA), an n-3 polyunsaturated fatty acid, on the exaggerated growth of vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR).

DESIGN

Cultured VSMC were prepared by an explant method from thoracic aortas in 8-week-old male Wistar-Kyoto (WKY)/Izumo rats and SHR/Izumo. Effects of EPA on basal DNA synthesis, expression of growth factors and cyclin-dependent kinase 2 (cdk2) activity were examined in VSMC from WKY rats and SHR.

METHODS

The cell cycles were synchronized with serum deprivation, then DNA synthesis in VSMC was measured by [3H]-thymidine incorporation. Fatty acid composition of the phospholipid fraction in VSMC was measured by gas chromatography. Expression of platelet-derived growth factor (PDGF) A-chain, transforming growth factor (TGF)-beta1 and basic fibroblast growth factor (bFGF) mRNAs was evaluated by reverse-transcription and polymerase chain reaction analysis. Cdk2 activity was determined by autoradiography after polyacrylamide gel electrophoresis of VSMC extracts that had been immunoprecipitated with anti-cdk2 antibody and protein A sepharose, and then incubated with 32P-ATP and histone H1.

RESULTS

High concentrations (40 and 80 micromol/I) of EPA significantly inhibited basal DNA synthesis in VSMC from both rat strains. Low dose (20 micromol/l) of EPA significantly inhibited basal DNA synthesis in VSMC from SHR, whereas the same dose of EPA stimulated DNA synthesis in VSMC from WKY rats. In analysis of fatty acid composition, low dose of EPA was considerably incorporated in VSMC. Low dose of EPA significantly inhibited angiotensin II- and phorbol ester milisterol-stimulated DNA synthesis in VSMC from both rat strains, whereas EPA did not affect PDGF-AA-stimulated DNA synthesis in VSMC from either rat strain. Low dose of other polyunsaturated fatty acids such as docosahexaenoic acid, arachidonic acid and linoleic acid did not significantly affect basal DNA synthesis in VSMC from either strain. Low dose of EPA significantly inhibited expression of TGF-beta1 mRNA in VSMC from SHR, whereas EPA did not affect expression of PDGF A-chain and bFGF mRNAs in VSMC from SHR. Cdk2 activity in VSMC from SHR was higher than that from WKY rats. Low dose of EPA inhibited cdk2 activity in VSMC from SHR, whereas it stimulated the activity in VSMC from WKY rats.

CONCLUSION

Low dose of EPA exerted specific inhibition of the exaggerated growth of VSMC from SHR through the suppression of TGF-beta.

Contribution of synthetic phenotype on the enhanced angiotensin II-generating system in vascular smooth muscle cells from spontaneously hypertensive rats

OBJECTIVE

We have demonstrated that cultured vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR), but not from normotensive Wistar-Kyoto (WKY) rats, produce angiotensin II (Ang II) in a homogeneous culture with increased levels of angiotensinogen, cathepsin D and angiotensin converting enzyme (ACE) at early passages. In the current study, we investigated how changes in the cell phenotype affect the Ang II-generating system and the growth of VSMC from SHR.

DESIGN AND METHODS

We evaluated basal DNA synthesis by [3H]thymidine incorporation, immunofluorescence of alpha-smooth muscle (SM) actin, mRNA expression of phenotype markers such as SM22alpha appeared by contractile phenotype, Ang II-generating system components and growth factors by reverse transcription and polymerase chain reaction analysis, and Ang II levels by radioimmunoassay in quiescent VSMC from WKY/Izumo rats and SHR/Izumo at passages 4, 8 and 12.

RESULTS

Basal DNA synthesis in VSMC from WKY rats increased with increasing passage number, whereas in cells from SHR it was markedly higher at early passages and was not affected by the passages. At early passage numbers, immunofluorescence of alpha-SM actin was stronger in VSMC from WKY rats than in cells from SHR, but decreased after several passages. Expression of SM22alpha mRNA was higher in VSMC from WKY rats than in cells from SHR at early passages, and decreased after several passages in cells from both rat strains. Expression of matrix Gla mRNA was higher in VSMC from SHR than in cells from WKY rats at early passage, and increased after several passages in cells from both rat strains. Ang II was not detected at early passages but increased in VSMC from WKY rats with increasing passage, whereas it was detected in VSMC from SHR at early passages and did not change with the passages. Expression of angiotensinogen mRNA was higher in VSMC from SHR than in cells from WKY rats, and was not affected by the passages. Expressions of cathepsin D and ACE mRNA were higher in VSMC from SHR than in cells from WKY rats at early passage, and were increased by the passages in VSMC from WKY rats. Expressions of transforming growth factor-beta1, platelet-derived growth factor A-chain, and basic fibroblast growth factor mRNA were significantly higher in VSMC from SHR than in cells from WKY rats, and were increased by the passages.

CONCLUSION

These data indicate that early in culture VSMC from SHR have the synthetic phenotype, whereas VSMC from WKY rats have the contractile phenotype which then changes to the synthetic phenotype after increased passage numbers, with increased expression of cathepsin D and ACE, which produce Ang II, and increased expression of Ang II-related growth factors, which induce the exaggerated growth observed in VSMC from SHR.

PDGF-A expression correlates with blood pressure and remodeling in 1K1C hypertensive rat arteries

We previously demonstrated remodeling of large and small arteries in angiotensin II-treated rats, paralleled by an increased expression of platelet-derived growth factor (PDGF)-A chain mRNA in large arteries. Both remodeling and PDGF-A expression were associated with elevation of blood pressure rather than a direct effect of angiotensin II. To further delineate the role of PDGF-A and elevated blood pressure, we assessed the level of PDGF-A and -B mRNA and protein in the wall of large as well as small arteries in the one-kidney, one-clip (1K1C) hypertensive rat, a non-renin-dependent model of hypertension. Fourteen days after renal artery stenosis, the thoracic aorta and both femoral arteries were collected from 1K1C rats (n = 8) and uninephrectomized controls (n = 8) and immediately processed for morphological measurement, immunohistochemistry, RT-PCR, and Western blotting. Systolic blood pressure was significantly elevated in hypertensive rats (202 +/- 26 mmHg) compared with control rats (122 +/- 7.9 mmHg) and was accompanied by arterial hypertrophy in both aorta and femoral arteries. The mRNA for PDGF-A chain was increased threefold in the thoracic aorta (P < 0.05) of 1K1C rats, whereas the message for PDGF-B was not significantly changed in hypertensive versus control animals. A higher staining of the intima-media was observed by using an anti-PDGF-A chain polyclonal antibody on paraffin-embedded sections. Western blot results indicated an approximately 2-fold increase in PDGF-A protein in aortic and femoral wall of the 1K1C rats. The results showed that both the mRNA and protein for PDGF-A chain are increased and well correlated with the blood pressure and wall area, suggesting a direct effect of elevated pressure on PDGF synthesis, which, in turn, may affect the onset and progression of vascular hypertrophy.

Production of angiotensin II by homogeneous cultures of vascular smooth muscle cells from spontaneously hypertensive rats

Production of angiotensin II (Ang II) in spontaneously hypertensive rats (SHR)-derived vascular smooth muscle cells (VSMC) has now been investigated. A nonpeptide antagonist (CV-11974) of Ang II type 1 receptors inhibited basal DNA synthesis in VSMC from SHR, but it had no effect on cells from Wistar-Kyoto (WKY) rats. Ang II-like immunoreactivity, determined by radioimmunoassay after HPLC, was readily detected in conditioned medium and extracts of SHR-derived VSMC, whereas it was virtually undetectable in VSMC from WKY rats. Isoproterenol increased the amount of Ang II-like immunoreactivity in conditioned medium and extracts of SHR-derived VSMC, whereas the angiotensin-converting enzyme inhibitor delapril significantly reduced the amount of Ang II-like immunoreactivity in conditioned medium and extracts of these cells. Reverse transcription-polymerase chain reaction analysis revealed that the abundance of mRNAs encoding angiotensinogen, cathepsin D, and angiotensin-converting enzyme was greater in VSMC from SHR than in cells from WKY rats. The abundance of cathepsin D protein by Western blotting was greater in VSMC from SHR than in cells from WKY rats. Ang I-generating and acid protease activities were detected in VSMC from SHR, but not in cells from WKY rats. These results suggest that SHR-derived VSMC generate Ang II with increases in angiotensinogen, cathepsin D, and angiotensin-converting enzyme, which contribute to the basal growth. Production of Ang II by homogeneous cultures of VSMC is considered as a new mechanism of hypertensive vascular disease.

Bunazosin hydrochloride inhibits exaggerated growth of vascular smooth muscle cells from spontaneously hypertensive rats by suppressing the response to growth factors

Selective alpha1-adrenoreceptor blockers were recently reported to have an in vivo antiproliferative effect on hypertensive cardiovascular organs. Cultured vascular smooth-muscle cells (VSMCs) from spontaneously hypertensive rats (SHRs) show exaggerated growth compared with cells from Wistar-Kyoto (WKY) rats. We investigated the effects of an alpha1-adrenoreceptor blocker, bunazosin hydrochloride (HCl), on the growth of VSMCs from SHRs. In the absence of serum, bunazosin HCl significantly inhibited basal DNA synthesis by VSMCs from SHRs, but not by cells from WKY rats. In the presence of serum, bunazosin HCl significantly inhibited DNA synthesis by VSMCs from both rat strains. Angiotensin (Ang) II, platelet-derived growth factor (PDGF)-AA, and epidermal growth factor (EGF) dose-dependently increased DNA synthesis by VSMCs from SHRs, but not by VSMCs from WKY rats. Bunazosin HCl significantly suppressed the response of DNA synthesis to PDGF-AA and EGF, but not to Ang II, in VSMCs from SHRs. Expression of basic fibroblast growth factor (bFGF), transforming growth factor-beta1 (TGFbeta1), and PDGF messenger RNA (mRNA) was markedly greater in VSMCs from SHRs than in cells from WKY rats. Bunazosin HCl significantly inhibited the expression of bFGF and TGFbeta1 mRNA in VSMCs from SHRs, but not in cells from WKY rats. These findings suggest that the inhibition of growth factor hyperresponsiveness and inhibition of the expression of growth factors in VSMCs from SHRs are associated with the antiproliferative effect of bunazosin.

Molecular mechanisms of the exaggerated growth of vascular smooth muscle cells in hypertension

The molecular mechanisms of the exaggerated growth of vascular smooth muscle cells (VSMC) in hypertension are reviewed based on our previous experimental data. Spontaneously hypertensive rats (SHR)-derived VSMC increasingly express angiotensinogen, cathepsin D and angiotensin-converting enzyme (ACE) mRNAs, compared to cells from normotensive Wistar-Kyoto (WKY) rats, indicating the presence of an Ang II generating system in a homogeneous culture of VSMC from SHR. The produced Ang II then induces TGF-beta. SHR-derived VSMC show the distinct expression and abnormal regulation by Ang II of TGF-beta receptors when compared with cells from WKY rats, which express TGF-beta type II receptor predominantly to induce PDGF A-chain stimulation of VSMC growth. These findings imply that the increased growth of VSMC in hypertension is a primary event independent of high blood pressure, and is associated with endogenous Ang II-related growth factors.