Adenovirus-mediated transfer of a dominant-negative H-ras suppresses neointimal formation in balloon-injured arteries in vivo

Investigation of electrical stimulation on phenotypic vascular smooth muscle cells differentiation in tissue-engineered small-diameter vascular graft

In the development of vascular tissue engineering, particularly in the case of small diameter vessels, one of the key obstacles is the blockage of these veins once they enter the in vivo environment. One of the contributing factors to this problem is the aberrant proliferation and migration of vascular smooth muscle cells (VSMCs) from the media layer of the artery to the interior of the channel. Two distinct phenotypes have been identified for smooth muscle cells, namely synthetic and contractile. Since the synthetic phenotype plays an essential role in the unusual growth and migration, the aim of this study was to convert the synthetic phenotype into the contractile one, which is a solution to prevent the abnormal growth of VSMCs. To achieve this goal, these cells were subjected to electrical signals, using a 1000 μA sinusoidal stimulation at 10 Hz for four days, with 20 min duration per 24 h. The morphological transformations and changes in the expression of vimentin, nestin, and β-actin proteins were then studied using ICC and flow cytometry assays. Also, the expression of VSMC specific markers such as smooth muscle myosin heavy chain (SMMHC) and smooth muscle alpha-actin (α-SMA) were evaluated using RT-PCR test. In the final phase of this study, the sheep decellularized vessel was employed as a scaffold for seeding these cells. Based on the results, electrical stimulation resulted in some morphological alterations in VSMCs. Furthermore, the observed reductions in the expression levels of vimentin, nestin and β-actin proteins and increase in the expression of SMMHC and α-SMA markers showed that it is possible to convert the synthetic phenotype to the contractile one using the studied regime of electrical stimulation. Finally, it can be concluded that electrical stimulation can significantly affect the phenotype of VSMCs, as demonstrated in this study.

Gene Therapy for Cardiovascular Disease: Basic Research and Clinical Prospects

In recent years, the vital role of genetic factors in human diseases have been widely recognized by scholars with the deepening of life science research, accompanied by the rapid development of gene-editing technology. In early years, scientists used homologous recombination technology to establish gene knock-out and gene knock-in animal models, and then appeared the second-generation gene-editing technology zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) that relied on nucleic acid binding proteins and endonucleases and the third-generation gene-editing technology that functioned through protein-nucleic acids complexes-CRISPR/Cas9 system. This holds another promise for refractory diseases and genetic diseases. Cardiovascular disease (CVD) has always been the focus of clinical and basic research because of its high incidence and high disability rate, which seriously affects the long-term survival and quality of life of patients. Because some inherited cardiovascular diseases do not respond well to drug and surgical treatment, researchers are trying to use rapidly developing genetic techniques to develop initial attempts. However, significant obstacles to clinical application of gene therapy still exists, such as insufficient understanding of the nature of cardiovascular disease, limitations of genetic technology, or ethical concerns. This review mainly introduces the types and mechanisms of gene-editing techniques, ethical concerns of gene therapy, the application of gene therapy in atherosclerosis and inheritable cardiovascular diseases, in-stent restenosis, and delivering systems.

Vascular smooth muscle cell proliferation as a therapeutic target. Part 1: molecular targets and pathways

Cardiovascular diseases are a major cause of human death worldwide. Excessive proliferation of vascular smooth muscle cells contributes to the etiology of such diseases, including atherosclerosis, restenosis, and pulmonary hypertension. The control of vascular cell proliferation is complex and encompasses interactions of many regulatory molecules and signaling pathways. Herein, we recapitulated the importance of signaling cascades relevant for the regulation of vascular cell proliferation. Detailed understanding of the mechanism underlying this process is essential for the identification of new lead compounds (e.g., natural products) for vascular therapies.

Gene-specific DNA methylation profiles and LINE-1 hypomethylation are associated with myocardial infarction risk

Background

DNA methylation profiles are responsive to environmental stimuli and metabolic shifts. This makes DNA methylation a potential biomarker of environmental-related and lifestyle-driven diseases of adulthood. Therefore, we investigated if white blood cells’ (WBCs) DNA methylation profiles are associated with myocardial infarction (MI) occurrence.

Whole-genome DNA methylation was investigated by microarray analysis in 292 MI cases and 292 matched controls from the large prospective Italian European Prospective Investigation into Cancer and Nutrition (EPIC) cohort (EPICOR study). Significant signals (false discovery rate (FDR) adjusted P < 0.05) were replicated by mass spectrometry in 317 MI cases and 262 controls from the Dutch EPIC cohort (EPIC-NL). Long interspersed nuclear element-1 (LINE-1) methylation profiles were also evaluated in both groups.

Results

A differentially methylated region (DMR) within the zinc finger and BTB domain-containing protein 12 (ZBTB12) gene body and LINE-1 hypomethylation were identified in EPICOR MI cases and replicated in the EPIC-NL sample (ZBTB12-DMR meta-analysis: effect size ± se = −0.016 ± 0.003, 95 % CI = −0.021;−0.011, P = 7.54 × 10⁻¹⁰; LINE-1 methylation meta-analysis: effect size ± se = −0.161 ± 0.040, 95 % CI = −0.239;−0.082, P = 6.01 × 10⁻⁵).

Moreover, cases with shorter time to disease had more pronounced ZBTB12-DMR hypomethylation (meta-analysis, men: effect size ± se = −0.0059 ± 0.0017, P_TREND = 5.0 × 10⁻⁴; women: effect size ± se = −0.0053 ± 0.0019, P_TREND = 6.5 × 10⁻³) and LINE-1 hypomethylation (meta-analysis, men: effect size ± se = −0.0010 ± 0.0003, P_TREND = 1.6 × 10⁻³; women: effect size ± se = −0.0008 ± 0.0004, P_TREND = 0.026) than MI cases with longer time to disease.

In the EPIC-NL replication panel, DNA methylation profiles improved case-control discrimination and reclassification when compared with traditional MI risk factors only (net reclassification improvement (95 % CI) between 0.23 (0.02–0.43), P = 0.034, and 0.89 (0.64–1.14), P < 1 × 10⁻⁵).

Conclusions

Our data suggest that specific methylation profiles can be detected in WBCs, in a preclinical condition, several years before the occurrence of MI, providing an independent signature of cardiovascular risk. We showed that prediction accuracy can be improved when DNA methylation is taken into account together with traditional MI risk factors, although further confirmation on a larger sample is warranted. Our findings support the potential use of DNA methylation patterns in peripheral blood white cells as promising early biomarkers of MI.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0164-3) contains supplementary material, which is available to authorized users.

Deletion of Methionine Sulfoxide Reductase A Does Not Affect Atherothrombosis but Promotes Neointimal Hyperplasia and Extracellular Signal-Regulated Kinase 1/2 Signaling

OBJECTIVE

Emerging evidence suggests that methionine oxidation can directly affect protein function and may be linked to cardiovascular disease. The objective of this study was to define the role of the methionine sulfoxide reductase A (MsrA) in models of vascular disease and identify its signaling pathways.

APPROACH AND RESULTS

MsrA was readily identified in all layers of the vascular wall in human and murine arteries. Deletion of the MsrA gene did not affect atherosclerotic lesion area in apolipoprotein E-deficient mice and had no significant effect on susceptibility to experimental thrombosis after photochemical injury. In contrast, the neointimal area after vascular injury caused by complete ligation of the common carotid artery was significantly greater in MsrA-deficient than in control mice. In aortic vascular smooth muscle cells lacking MsrA, cell proliferation was significantly increased because of accelerated G1/S transition. In parallel, cyclin D1 protein and cdk4/cyclin D1 complex formation and activity were increased in MsrA-deficient vascular smooth muscle cell, leading to enhanced retinoblastoma protein phosphorylation and transcription of E2F. Finally, MsrA-deficient vascular smooth muscle cell exhibited greater activation of extracellular signal-regulated kinase 1/2 that was caused by increased activity of the Ras/Raf/mitogen-activated protein kinase signaling pathway.

CONCLUSIONS

Our findings implicate MsrA as a negative regulator of vascular smooth muscle cell proliferation and neointimal hyperplasia after vascular injury through control of the Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 signaling pathway.

Nanoparticle drug- and gene-eluting stents for the prevention and treatment of coronary restenosis

Percutaneous coronary intervention (PCI) has become the most common revascularization procedure for coronary artery disease. The use of stents has reduced the rate of restenosis by preventing elastic recoil and negative remodeling. However, in-stent restenosis remains one of the major drawbacks of this procedure. Drug-eluting stents (DESs) have proven to be effective in reducing the risk of late restenosis, but the use of currently marketed DESs presents safety concerns, including the non-specificity of therapeutics, incomplete endothelialization leading to late thrombosis, the need for long-term anti-platelet agents, and local hypersensitivity to polymer delivery matrices. In addition, the current DESs lack the capacity for adjustment of the drug dose and release kinetics appropriate to the disease status of the treated vessel. The development of efficacious therapeutic strategies to prevent and inhibit restenosis after PCI is critical for the treatment of coronary artery disease. The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and ability to facilitate prolonged drug release. Despite the potential benefits of nanoparticles as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of nanoparticle materials, as well as to their size and shape. This review describes the molecular mechanism of coronary restenosis, the use of DESs, and progress in nanoparticle drug- or gene-eluting stents for the prevention and treatment of coronary restenosis.

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

Small G proteins exist in eukaryotes from yeast to human and constitute the Ras superfamily comprising more than 100 members. This superfamily is structurally classified into five families: the Ras, Rho, Rab, Arf, and Ran families that control a wide variety of cell and biological functions through highly coordinated regulation processes. Increasing evidence has accumulated to identify small G proteins and their regulators as key players of the cardiovascular physiology that control a large panel of cardiac (heart rhythm, contraction, hypertrophy) and vascular functions (angiogenesis, vascular permeability, vasoconstriction). Indeed, basal Ras protein activity is required for homeostatic functions in physiological conditions, but sustained overactivation of Ras proteins or spatiotemporal dysregulation of Ras signaling pathways has pathological consequences in the cardiovascular system. The primary object of this review is to provide a comprehensive overview of the current progress in our understanding of the role of small G proteins and their regulators in cardiovascular physiology and pathologies.

Electrical stimulation inhibits neointimal hyperplasia after abdominal aorta balloon injury through the PTEN/p27Kip1 pathway

Electric fields (EFs) exert biological effects on promoting wound healing by facilitating cell division, cell proliferation, and cell directional migration toward the wound. In this study, we examined the inhibitory effect of direct-current (DC) EFs on the formation of neointimal hyperplasia and the possible mechanism in an abdominal aorta balloon injury rabbit model. Sixty rabbits were divided into normal, control, and experimental groups. After establishment of the abdominal aorta balloon injury model, electrodes were implanted into the bilateral psoas major muscle in control and experimental groups. Only the experimental group received electric stimulation (EFs applied at 3 or 4 V/cm for 30 min/day) for 1, 2, and 4 weeks, respectively. Neointimal hyperplasia of the abdominal aorta and proliferation of vascular smooth muscle cells (VSMCs) were measured. Expressions of collagen, p27(Kip1), and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) were detected. Results showed that the ratio of the tunica intima area to the tunica media area, the expression of type-I collagen in the neointimal, and the proliferating cell nuclear antigen index in experimental groups were significantly less than those in control groups 2 weeks post-operation (P< 0.01). Expressions of p27(Kip1) and PTEN were increased in experimental groups compared with control groups (P< 0.01). In conclusion, our results suggested that the application of DC EFs could inhibit neointimal hyperplasia and reduce collagen expression after abdominal aorta balloon injury. This was probably induced by upregulation of PTEN/p27(Kip1) expression, thereby inhibiting VSMC proliferation.

New Ras CAAX mimetics: design, synthesis, antiproliferative activity, and RAS prenylation inhibition

Mimetics of the C-terminal CAAX tetrapeptide of Ras protein were designed replacing cysteine (C) by 2-hydroxymethylbenzodioxane or 2-aminomethylbenzodioxane, respectively etherified and amidified with 2'-methyl or 2'-methoxy substituted 2-carboxy-4-hydroxybiphenyl and 2,4-dicarboxybiphenyl. These pluri-substituted biphenyl systems, used as internal spacer and AA dipeptide bioisoster, were linked to the methyl ester of l-methionine, glycine or l-leucine by an amide bond. The resultant twelve pairs of stereoisomers at the dioxane C-2 were tested for antiproliferative effect finding the maximum activity for derivatives with methyleneoxy linker between benzodioxane and 2'-methylbiphenyl. Of these compounds, the one with terminal methionine and S configuration proved a good Ras prenylation inhibitor in a cell-based assay.

Nf1+/- mice have increased neointima formation via hyperactivation of a Gleevec sensitive molecular pathway

Neurofibromatosis type I (NF1) is a genetic disorder caused by mutations in the NF1 tumor suppressor gene. Neurofibromin is encoded by NF1 and functions as a negative regulator of Ras activity. Somatic mutations in the residual normal NF1 allele within cancers of NF1 patients is consistent with NF1 functioning as a tumor-suppressor. However, the prevalent non-malignant manifestations of NF1, including learning and bone disorders emphasize the importance of dissecting the cellular and biochemical effects of NF1 haploinsufficiency in multiple cell lineages. One of the least studied complications of NF1 involves cardiovascular disorders, including arterial occlusions that result in cerebral and visceral infarcts. NF1 vasculopathy is characterized by vascular smooth muscle cell (VSMC) accumulation in the intima area of vessels resulting in lumen occlusion. We recently showed that Nf1 haploinsufficiency increases VSMC proliferation and migration via hyperactivation of the Ras-Erk pathway, which is a signaling axis directly linked to neointima formation in diverse animal models of vasculopathy. Given this observation, we tested whether heterozygosity of Nf1 would lead to vaso-occlusive disease in genetically engineered mice in vivo. Strikingly, Nf1+/- mice have increased neointima formation, excessive vessel wall cell proliferation and Erk activation after vascular injury in vivo. Further, this effect is directly dependent on a Gleevec sensitive molecular pathway. Therefore, these studies establish an Nf1 model of vasculopathy, which mirrors features of human NF1 vaso-occlusive disease, identifies a potential therapeutic target and provides a platform to further dissect the effect of Nf1 haploinsufficiency in cardiovascular disease.

Gene therapy of fibroproliferative vasculopathies: current ideas in molecular mechanisms and biomedical technology

Intimal hyperplasia occurs primarily as a part of the pathogenesis of coronary artery disease or secondary to therapeutic intervention in relieving vascular occlusion. Intimal hyperplasia involving vascular smooth muscle cells is found in atherosclerosis, post-balloon angioplasty restenosis, in-stent restenosis and vein graft disease, predominantly involving the use of saphenous vein conduits in coronary artery bypass grafting procedures. One potentially exciting area is that of gene therapy. Gene and protein expression patterns at the site of vasculoproliferative lesions have been widely studied and several target areas have been identified on the basis of whether the gene has an antiproliferative, proapoptotic, matrix degrading or endothelial protective action. Blood vessels are easily accessible for the delivery of the gene product, and experimental studies using animal models have used catheter-delivered gene products at the site of vascular injury. Currently, the application of antisense technology and adenoviral vector-mediated delivery has shown significant promise, albeit in in vitro or animal model settings. In this review, we discuss the current knowledge in the application of gene therapy in fibroproliferative vasculopathies. We examine some of the cellular mechanisms and intermediaries which could be potential candidates for gene targeting. We also present some of the advances in biomedical technology that might provide useful vehicles for pinpoint delivery of the gene product. Could the future of restenosis treatment be in gene therapy or is it misplaced enthusiasm?

STAT4 and the proliferation of artery smooth muscle cells in atherosclerosis

Artery smooth muscle cell proliferation is of key importance in the development of atherosclerosis and restenosis following PTCA. In order to understand gene regulation involved in these processes, vascular smooth muscle cells (VSMCs) from atherosclerosis-susceptible White Carneau (WC) and atherosclerosis-resistant Show Racer (SR) pigeons were used to identify transcription factors involved in the enhanced proliferation of WC VSMCs. With protein/DNA array, signal transducer and activator of transcription 4 (STAT4) was found to have over a 10-fold increase in expression in WC compared to SR VSMCs. The difference was confirmed with electrophoretic-mobility shift assay (EMSA) and Western blot. Cells cultured under low serum had 5-fold higher levels of STAT4 in WC compared to SR. By Western analysis, aortic tissue from newly hatched WC pigeons had 1.7-2.0 times greater STAT4 expression than in SR pigeons. A pathway whereby enhanced STAT4 may be associated with enhanced proliferation was identified following IL-12 stimulation of WC VSMCs where 3-fold increases in proliferation and 2-fold higher expression of STAT4 were measured. The findings suggest STAT4 may play a role in VSMC proliferation and describe a unique pigeon model system in which to study STAT4 as a gene target for atherosclerosis therapy.

Neurofibromin is a novel regulator of RAS-induced signals in primary vascular smooth muscle cells

Neurofibromatosis type I (NF1) is a genetic disorder caused by mutations in the NF1 tumor suppressor gene. Neurofibromin is encoded by NF1 and functions as a negative regulator of Ras activity. NF1 patients develop renal artery stenosis and arterial occlusions resulting in cerebral and visceral infarcts. Further, NF1 patients develop vascular neurofibromas where tumor vessels are invested in a dense pericyte sheath. Although it is well established that aberrations in Ras signaling lead to human malignancies, emerging data generated in genetically engineered mouse models now implicate perturbations in the Ras signaling axis in vascular smooth muscular cells (VSMCs) as central to the initiation and progression of neointimal hyperplasia and arterial stenosis. Despite these observations, the function of neurofibromin in regulating VSMC function and how Ras signals are terminated in VSMCs is virtually unknown. Utilizing VSMCs harvested from Nf1+/- mice and primary human neurofibromin-deficient VSMCs, we identify a discrete Ras effector pathway, which is tightly regulated by neurofibromin to limit VSMC proliferation and migration. Thus, these studies identify neurofibromin as a novel regulator of Ras activity in VSMCs and provide a framework for understanding cardiovascular disease in NF1 patients and a mechanism by which Ras signals are attenuated for maintaining VSMC homeostasis in blood vessel walls.

Isothiazole dioxide derivative 6n inhibits vascular smooth muscle cell proliferation and protein farnesylation

Isothiazole dioxides have been shown to inhibit Trypanosoma brucei protein farnesyltransferase (PFTase) in isolated enzyme, but elicited only a minor effect on mammalian PFTase. In the present study we have evaluated the effect of 3-diethylamino-4-(4-methoxyphenyl)-isothiazole 1,1-dioxides with different substituents at C5, on rat PFTase and protein geranylgeranyltransferase-I (PGGTase-I) with the final aims to improve the potency against mammalian PFTase and to identify new compounds with antiproliferative properties. For these purposes, in vitro and cell culture models have been utilized. The results showed that isothiazole dioxides with C4-C5 double bond and sulfaryl substituted at the C5 position but none of the dihydro-derivatives, were able to inhibit in vitro PFTase in a concentration dependent manner (IC50 ranging from 8.56 to 1015 microM). Among those, compound 6n (C5; methyl-S) displayed 500-fold higher inhibitory potency on PFTase than PGGTase-I. Compound 6n was shown to affect rat smooth muscle cell (SMC) proliferation at concentrations similar (IC50 = 61.4 microM) to those required to inhibit [3H]-farnesol incorporation into cellular proteins (-44.1% at 100 microM). Finally, compound 6n interferes with rat SMC proliferation by blocking the progression of G0/G1 phase without inducing apoptosis, as assessed by [3H]-thymidine incorporation assay and flow cytometry analysis. Taken together, we described a new PFTase inhibitor containing the isothiazole dioxide moiety that affects mammalian protein farnesylation and SMC proliferation by inhibiting G0/G1 phase of the cell cycle.

Ultrafine carbon black particles stimulate proliferation of human airway epithelium via EGF receptor-mediated signaling pathway

Exposure to ambient ultrafine particles induces airway inflammatory reactions and tissue remodeling. In this experiment, to determine whether ultrafine carbon black (ufCB) affects proliferation of airway epithelium and, if so, what the mechanism of action is, we studied human primary bronchial epithelial cell cultures. Incubation of cells in the serum-free medium with ufCB increased incorporations of [3H]thymidine and [3H]leucine into cells in a time- and dose-dependent manner. This effect was attenuated by Cu- and Zn-containing superoxide dismutase (Cu/Zn SOD) and apocynin, an inhibitor of NADPH oxidase, and completely inhibited by pretreatment with the epidermal growth factor receptor (EGF-R) tyrosine kinase inhibitors AG-1478 and BIBX-1382, and the mitogen-activated protein kinase kinase inhibitor PD-98059. Transfection of a dominant-negative mutant of H-Ras likewise abolished the effect ufCB. Stimulation with ufCB also induced processing of membrane-anchored proheparin-binding (HB)-EGF, release of soluble HB-EGF into the medium, association of phosphorylated EGF-R and Shc with glutathione- S-transferase-Grb2 fusion protein, and phosphorylation of extracellular signal-regulated kinase (ERK). Pretreatment with AG-1478, [Glu52] Diphtheria toxin, a specific inhibitor of HB-EGF, neutralizing HB-EGF antibody, Cu/Zn SOD, and apocynin each inhibited ufCB-induced ERK activation. These results suggest that ufCB causes oxidative stress-mediated proliferation of airway epithelium, involving processing of HB-EGF and the concomitant activation of EGF-R and ERK cascade.

Vascular smooth muscle cell migration: current research and clinical implications

Atherosclerosis and intimal hyperplasia are major causes of morbidity and mortality. These processes develop secondary to endothelial injury due to multiple stimuli, including smoking, diabetes mellitus, hypertension, and hyperlipidemia. Once this injury occurs, an essential element in the development of both these processes is vascular smooth muscle cell (VSMC) migration. Understanding the mechanisms involved in VSMC migration and ultimately the development of strategies by which this process can be inhibited, has been a major focus of research. The authors present a review of the extracellular proteins (growth factors, extracellular matrix components, and cell surface receptors) and intracellular signaling pathways involved in VSMC migration, as well as potential therapeutic approaches to inhibit this process.

New strategies to prevent restenosis

The Holy Grail of cardiovascular pharmacology has been the search for an effective therapy targeting restenosis after angioplasty and/or intra-arterial stenting. The failure of promising therapeutics in clinical trials underscores the complexity and redundancy of the signaling cascades regulating mitogenesis and fibrogenesis. Novel therapeutic modalities have potential to target dysfunctional signaling elements directly in vascular smooth muscle cells. Significant progress in the treatment against restenosis will require the exploitation and cross-fertilization of developments in the fields of pharmacology, bioengineering, genetics, and molecular biology. Collaboration among researchers in these fields will be essential.

Inhibition of STAT3 prevents neointima formation by inhibiting proliferation and promoting apoptosis of neointimal smooth muscle cells

In cultured vascular smooth muscle cells (SMCs), STAT3 mediates proliferation signal by directly activating transcription of early growth response genes. Recently, we have found that balloon injury transiently induces JAK2 and STAT3 expressions and activations with a peak at day 7 in rat carotid artery. However, the specific role of STAT3 in neointima formation remains unknown. Adenoviral vector encoding a dominant negative STAT3 (AxCAdnSTAT3) or beta-galactosidase (control) was overexpressed in a balloon-injured artery to inhibit endogenous STAT3 activation selectively. In controls, neointima became evident after day 4, and reached a maximum at day 14. The number of bromodeoxyuridine (BrdU)-positive proliferating or TUNEL-positive apoptotic neointimal SMCs peaked at day 7, decreasing to lower levels by day 14. AxCAdnSTAT3 not only abrogated STAT3 phosphorylation but also decreased BrdU labeling index by 60% and increased TUNEL index by 35% at day 7 versus controls, resulting in the 40% reduction in the intima/media area ratio at day 14. At day 7, in controls, vascular injury upregulated antiapoptotic mediator Mcl-i and Bcl-xL expression by 8-fold to 5-fold, respectively, versus sham, whereas proapoptotic Bax slightly increased by 1.5-fold versus sham. AxCAdnSTAT3 reversed the upregulated Mcl-1 and Bcl-xL levels by 70% and 37%,respectively, while having no affect on Bax expression. In conclusion, the STAT3-mediated pathway plays an important role in neointima formation through enhanced vascular SMC accumulation by promoting cell proliferation and survival.

Hepatocyte growth factor modulates motility and invasiveness of ovarian carcinomas via ras mediated pathway

Hepatocyte growth factor (HGF) is a multifunctional growth factor which has pleiotrophic biological effects on epitherial cells, such as proliferation, motogenesis, invasiveness and morphogenesis. Peritoneal dissemination is critical for the progression of ovarian cancer and our study revealed that HGF induces migration and invasion of ovarian cancer cells. We also demonstrated that HGF stimulates autophosphorylation of its receptor, followed by activation of the Ras-MAP (mitogen-activated peptide) kinase cascade. Moreover, infection of ovarian cancer cells with Ras dominant-negative adenovirus reduced the HGF-induced motogenic and invasive activities. Additionally, both MEK and PI3-kinase pathways downstream of Ras was involved in HGF-stimulated ovarian cancer cell invasiveness.

Adenoviral delivery of a constitutively active retinoblastoma mutant inhibits neointima formation in a human explant model for vein graft disease

Intimal hyperplasia resulting from vascular injury remains a major obstacle in the long-term success of coronary artery bypass grafts. Inhibition of smooth muscle cell (SMC) proliferation using adenoviral gene transfer of cell cycle inhibitors resulted in reduced neointima formation in various animal models. However, little is known about the effect on human SMCs and neointima formation. Here we report the effects of infection with an adenoviral vector encoding a constitutively active form of the retinoblastoma gene (Ad. delta Rb) on proliferation of human saphenous vein SMCs (HSVSMCs) and neointima formation in organ cultures of human saphenous vein. Proliferation of SMCs was inhibited dose-dependently after infection with Ad. delta Rb. A near-total inhibition was found at an Ad. delta Rb concentration of 10(8) pfu/ml. Organ cultures of human saphenous vein segments were used to evaluate the effect of Ad. delta Rb infection on neointima formation and vein graft disease. Segments cultured for 4 weeks develop a neointima that is morphologically highly similar to early initimal lesions found in pathological vein grafts in vivo. Infection of saphenous vein segments with 2 x 10(9) pfu/ml Ad. delta Rb resulted in a 59% reduction of neointimal area when compared to uninfected counterparts, whereas infection with control adenovirus, Ad.LacZ, had no significant effect. The results of this study show that Ad. delta Rb gene transfer might be an efficient approach to prevent neointima formation in human saphenous vein grafts.

Genes potentially involved in plaque rupture

PURPOSE OF REVIEW

Rupture of an atherosclerotic plaque is the predominant underlying event in the pathogenesis of acute coronary syndromes and stroke. While ruptured plaques are morphologically well described, the precise molecular mechanisms involved in plaque rupture are still incompletely understood. Over the last few years, techniques like microarray, suppression subtractive hybridization and differential display enabled us to study complex gene expression profiles that occur during the process of atherogenesis. In this review we focus on recent large-scale gene expression profiles performed on whole mount vascular specimens.

RECENT FINDINGS

The gene expression profiles on whole mount vascular tissue confirmed that at least three mechanisms are involved in plaque rupture: (1) a disturbed balance in extracellular matrix turnover, (2) disturbed regulation of cell turnover and (3) processes involved in lipid metabolism. Animal models exhibiting features of plaque rupture reflect the involvement of these three mechanisms. The most dramatic mouse phenotypes were observed after interventions in at least two of these mechanisms.

SUMMARY

The observation of plaque rupture in recent mice models is indicative of the multifactorial process of plaque rupture. This multifactorial character of plaque rupture suggests that interventions may be most effective when they influence more than one mechanisms at a time.

Inhibitors of the ras oncogene as therapeutic targets

Advances in our understanding of the molecular pathways and genetic mutations that control tumor cell proliferation and metastasis present an opportunity to develop novel, mechanism-based therapeutic strategies. Ras mutations are the most frequently activated oncogenes in human tumors, with over 30% expressing ras mutations. Molecular dissection of the signaling pathway and the mechanisms of ras anchorage, post-translational modification, and downstream effector signaling of ras now under intensive investigation will help us to design additional methods for ras-directed therapy in an effort to reach an optimal treatment for human tumors that will most likely comprise a combination of modalities targeted at the different underlying genetic defects. The successes and limitations of ras-targeted therapies must be viewed in light of the increasing understanding of the complexity of the ras-signaling pathway. Only now are we beginning to discover the many functions of this integrated pathway, such as the differences between the actions of various ras isoforms that may affect our choice of therapeutic approach. Many of these Ras therapeutic targets have shown success in preclinical studies, and some have shown efficacy in clinical trials with minimal toxicities. Compounds that block ras-transforming activity without affecting normal ras function seem more attractive for the future development of ras-targeted therapy. FTIs may partially fulfill such requirements. Based on their specific, novel, and mechanism-based action; minimal toxicity; and encouraging responses in clinical trials, the development of Ras therapeutic targets as single agents or in combination with conventional chemotherapy and radiotherapy should be pursued.

Gene therapy in cardiovascular disease. Current status

Cardiovascular disease is the leading cause of mortality and morbidity in developed countries. Most conventional therapy is often inefficacious and tends to treat the symptoms rather than the underlying causes of the disorder. Gene therapy offers a novel approach for prevention and treatment of cardiovascular diseases. Technical advances in viral vector systems and the development of fusigenic liposome vectors have been crucial to the development of effective gene therapy strategies directed at the vasculature and myocardium in animal models. Gene transfer techniques are being evaluated as potential treatment alternatives for both genetic (familial hypercholesterolemia) and acquired occlusive vascular diseases (atherosclerosis, restenosis, arterial thrombosis) as well as for cardiac disorders including heart failure, myocardial ischemia, graft coronary arteriosclerosis and hypertension. Continued technologic advances in vector systems and promising results in human and animal gene transfer studies make the use of gene therapy a promising strategy for the treatment of cardiovascular disorders.

Phosphatidylinositol 3-kinase activity is required for epidermal growth factor to suppress proteolysis

Suppression of protein breakdown occurs commonly in cell growth, but the pathways responsible for controlling proteolysis are poorly understood. Protein breakdown in NRK-52E renal epithelial cells treated with epidermal growth factor (EGF) and intracellular signaling inhibitors or dominant negative signaling molecules contained in an adenoviral vector were measured. The tyrosine kinase inhibitor, herbimycin A, eliminated the suppression of proteolysis induced by EGF. In contrast, the Src inhibitor, PP1, had no effect. Expression of dominant negative H-RasY57 blocked the ability of EGF to stimulate downstream targets of Ras and also reduced the ability of EGF to suppress proteolysis. Inhibiting MEK did not influence the ability of EGF to suppress proteolysis, but the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, LY249002, stimulated basal proteolysis and completely eliminated the proteolytic response to EGF. Use of an adenovirus that expresses a dominant negative p85 subunit of class 1 PI 3-kinase completely blocked the ability of EGF to suppress proteolysis, whereas use of an adenovirus expressing a K227E constitutively active p110 subunit reproduced the reduction in protein breakdown. It was concluded that EGF suppresses proteolysis by a mechanism that involves Ras and class 1 PI 3-kinase.

Gene therapy in vascular surgery comes of age

In the last decade, gene therapy for cardiovascular diseases has been becoming a reality. However, although numerous successful experimental studies have suggested possible strategies of gene therapy for cardiovascular disorders, the clinical outcome remains limited. Because cardiovascular diseases are the result of complex causes, there is no exact answer to the following question: Which is the best gene to treat vascular diseases? In addition, current limitations include less clinically relevant vectors regarding both gene-transfer efficiency and safety, and at present, most efforts are focused on identifying more effective therapeutic genes, as well as developing more effective vectors. Furthermore, greater pathophysiologic understanding of these diseases, including vein-graft remodeling and ischemic limbs, is required. Regarding the relevant vector, we recently developed a novel mononegavirus-based gene-transfer vector, namely recombinant Sendai virus, which has shown dramatically superior gene-transfer efficiency to other vectors, including adenovirus, in several organs (eg, the vessel wall and skeletal muscles). These efforts now offer new possibilities to get more fruits in the field of gene therapy for vascular surgery.

Requirement of Ras for the activation of mitogen-activated protein kinase by calcium influx, cAMP, and neurotrophin in hippocampal neurons

Mitogen-activated protein (MAP) kinase plays important roles in the establishment of long-term potentiation both in vitro and in living animals. MAP kinase is activated in response to a broad range of stimuli, including calcium influx through NMDA receptor and L-type calcium channel, cAMP, and neurotrophins. To investigate the role of Ras in the activation of MAP kinase and cAMP response element-binding protein (CREB) in hippocampal neurons, we inhibited Ras function by overexpressing a Ras GTPase-activating protein, Gap1(m), or dominant negative Ras by means of adenovirus vectors. Gap1(m) expression almost completely suppressed MAP kinase activation in response to NMDA, calcium ionophore, membrane depolarization, forskolin, and brain-derived neurotrophic factor (BDNF). Dominant negative Ras also showed similar effects. On the other hand, Rap1GAP did not significantly inhibit the forskolin-induced activation of MAP kinase. In contrast to MAP kinase activation, the inactivation of Ras activity did not inhibit significantly NMDA-induced CREB phosphorylation, whereas BDNF-induced CREB phosphorylation was inhibited almost completely. These results demonstrate that Ras transduces signals elicited by a broad range of stimuli to MAP kinase in hippocampal neurons and further suggest that CREB phosphorylation depends on multiple pathways.

Local gene delivery to the vessel wall

This review will provide an overview of delivery strategies that are being evaluated for vascular gene therapy. We will limit our discussion to those studies that have been demonstrated, utilizing in vivo model systems, to limit post-interventional restenosis. We also discuss the efficacy of the vectors and methods currently being used to transfer genetic material to the vessel wall. The efficiency of these techniques is a critical issue for the successful application of gene therapy.

In vivo suppression of restenosis in balloon-injured rat carotid artery by adenovirus-mediated gene transfer of the cell surface-directed plasmin inhibitor ATF.BPTI

Injury-induced neointimal development results from migration and proliferation of vascular smooth muscle cells (SMC). Cell migration requires controlled proteolytic degradation of extracellular matrix surrounding the cell. Plasmin is a major contributor to this process by degrading various matrix proteins directly, or indirectly by activating matrix metalloproteinases. This makes it an attractive target for inhibition by gene transfer. An adenoviral vector, Ad.ATF.BPTI, was constructed encoding a hybrid protein, which consists of the aminoterminal fragment (ATF) of urokinase-type plasminogen activator (u-PA) linked to bovine pancreas trypsin inhibitor (BPTI), a potent inhibitor of plasmin. This hybrid protein binds to the u-PA receptor, thereby inhibiting plasmin activity at the cell surface, and was found to be a potent inhibitor of cell migration in vitro. Local infection with Ad.ATF.BPTI of balloon-injured rat carotid artery resulted in detectable expression of ATF.BPTI mRNA and protein in the vessel wall. Morphometric analysis of arterial cross-sections revealed that delivery of Ad.ATF.BPTI to the carotid artery wall at the time of balloon injury inhibited neointima formation by 53% (P < 0.01) at 14 days and 19% (P = NS) at 28 days after injury when compared with control vector-infected arteries. Intima/media ratios were decreased by 60% (P < 0.01) and 35% (P < 0.05) at 14 and 28 days, respectively, when compared with control vector-infected arteries. Furthermore, a small but significant increase in medial area was found in the Ad.ATF.BPTI-treated arteries at 28 days (P < 0.05). These results show that local infection of the vessel wall with Ad.ATF.BPTI reduces neointima formation, presumably by inhibiting SMC migration, thereby offering a novel therapeutic approach to inhibiting neointima development.

Gene therapy in heart disease

Application of gene therapy to the field of cardiovascular disorders has been the subject of intensive work over the recent period. Gene therapy for cardiovascular disorders is now fast developing with most therapies being devoted to the consequences (ischemia) rather than the causes of atherosclerotic diseases. Recent human clinical trials have shown that injection of naked DNA encoding vascular endothelial growth factor promotes collateral vessel development in patients with critical limb ischemia or chronic myocardial ischemia. Promising studies in animals have also fueled enthusiasm for treatment of human restenosis by gene therapy, but clinical applications are warranted. Application of gene transfer to other cardiovascular diseases will require the coordinated development of a variety of new technologies, as well as a better definition of cellular and gene targets.

The future of gene therapy for stroke

New diagnostic and treatment strategies are being developed for stroke. Gene therapy has several potential advantages over classical pharmacologic therapy. Direct administration of DNA into the brain offers the advantage of producing high concentrations of therapeutic agents in a relatively localized environment. Gene transfer also provides longer duration of effect than traditional drug therapy. Recent studies indicate that gene transfer can produce functional proteins in brain parenchyma and cerebral blood vessels after stroke. In animal models, gene transfer may reduce effects of cerebral ischemia or subarachnoid hemorrhage. This review summarizes some current methods of gene transfer to the brain and recent progress that may lead to gene therapy for stroke.

Restenosis and gene therapy

Atherosclerosis is one of the main causes of mortality and morbidity in westernised countries. Treatment of symptomatic atherosclerosis by angioplasty involves major vascular responses such as neointima formation and constrictive vascular remodelling leading to restenosis. Stent placement prevents vasoconstriction but is associated with in-stent neointima formation. Therefore, stent placement requires adjunctive therapy. In this review we discuss the potential of local gene therapy for restenosis. More particularly, we focus on strategies to inhibit smooth muscle cell (SMC) proliferation and migration, prevent thrombosis, decrease oxidative stress in the arterial wall and enhance re-endothelialisation associated with adaptive remodelling. The potential of different vector systems and devices for local gene transfer in the arterial wall is discussed.

Effects of active and negative mutants of Ras on rat arterial neointima formation

BACKGROUND

Ras protein is a key signal transducer in the cause of cell proliferation. We studied the effects of active and negative mutants of the Ras gene on arterial neointimal formation in rats, with the aim of elucidating the molecular mechanisms regulating restenosis following percutaneous transluminal coronary angioplasty.

MATERIALS AND METHODS

AdRasV12 and AdRasN17, the recombinant adenoviruses containing a constitutively active mutant and a dominant negative mutant of Ras, respectively, were used to determine whether Ras is necessary and sufficient to modulate the smooth muscle cell proliferation and neointima formation. Following balloon injury, rat common carotid arteries were treated in their distal half with AdRasV12, AdRasN17, or AdLacZ, with the proximal half used as uninfected control.

RESULTS

In rat arteries subjected to balloon injury, either uninfected or treated with AdLacZ, there were pronounced SMC proliferation and neointima formation. These changes were markedly augmented by AdRasV12 and reduced by AdRasN17.

CONCLUSION

Ras is necessary and sufficient for SMC proliferation and neointima formation and may play a critical role in restenosis following balloon angioplasty.

Signal transduction of angiotensin II type 1 receptor through receptor tyrosine kinase

In cultured vascular smooth muscle cells, the angiotensin II (AngII) type-1 (AT(1)) receptor generates growth-promoting signals via the epidermal growth factor (EGF) receptor system. This 'transactivation' mechanism now appears to be utilized by a variety of G-protein-coupled receptors in many cells. The AngII-induced EGF receptor transactivation leads to activation of downstream signaling molecules including Ras, ERK, c-fos, Akt/protein kinase B, and p70 S6 kinase. We propose three possible mechanisms may be involved in the transactivation, (i) an upstream tyrosine kinase, (ii) reactive oxygen species, and (iii) a juxtacrine activation of the EGF receptor ligand. Whether the EGF receptor signal transduction induced by AngII plays an essential role in cardiovascular remodeling remains to be investigated.

Gene transfer of dominant negative Rho kinase suppresses neointimal formation after balloon injury in pigs

Restenosis after angioplasty still remains a major problem for which neointimal formation appears to play an important role. Recent studies in vitro suggested that Rho kinase, a target protein of Rho, is important in various cellular functions. We thus examined whether Rho kinase is involved in the restenotic changes after balloon injury. In vivo gene transfer was performed immediately after balloon injury in both sides of the porcine femoral arteries with adenoviral vector encoding either a dominant negative form of Rho kinase (AdDNRhoK) or beta-galactosidase (AdLacZ) as a control. One week after the transfer, immunohistochemistry confirmed the successful gene expression in the vessel wall, whereas 2 wk after the transfer, Western blotting showed the functional upregulation of Rho kinase at the AdLacZ site and its suppression at the AdDNRhoK site. Angiography showed the development of a stenotic lesion at the AdLacZ site where histological neointimal formation was noted, whereas those changes were significantly suppressed at the AdDNRhoK site. These results indicate that Rho kinase is involved in the pathogenesis of neointimal formation after balloon injury in vivo.

Suppression of malignant growth potentials of v-Src-transformed human gallbladder epithelial cells by adenovirus-mediated dominant negative H-Ras

Although Src transformation of NIH3T3 mouse fibroblasts has been shown to be dependent on Ras function, the signaling mechanism whereby Src induces malignant transformation of human epithelial cells still remains unclear. In the present study, we analyzed the functional role of Ras, which acts downstream of Src in intracellular signaling, in the acquisition of fully neoplastic potentials by v-Src-transformed human gallbladder epithelial cells (HAG/src3-1) by infecting these cells with replication-defective adenovirus vector expressing dominant negative H-Ras (AdCARasY57). High efficiency of gene transduction was demonstrated with the adenovirus vector containing beta-gal gene insert (AdCALacZ). On infection with AdCARasY57, the activity of mitogen-activated protein (MAP) kinase, a major downstream event triggered by Ras, was markedly inhibited over 7 days, indicating that the inhibition of Ras function by AdCARasY57 remains active during this period. AdCARasY57 did not inhibit the monolayer growth of HAG-1 cells transfected with activated H-ras, but inhibited the HAG/src3-1 cells by 30%, as compared with cells infected with AdCALacZ as a control. This growth inhibition by AdCARasY57 was strengthened nearly twofold on surfaces coated with an antiadhesive polymer (poly 2-hydroxyethylmethacrylate) that can quantitate anchorage-independent growth, and was much more pronounced up to 95% when assayed in soft agar. The HAG/src3-1 cells transfected with beta-gal gene produced tumors in nude mice within 4 weeks after implantation, whereas cells infected with AdCARasY57 failed to form tumors during this period. These findings show that Ras function is essential for v-Src-induced anchorage-independent growth in vitro as well as tumorigenesis in vivo, and that mitogenic activity driven by v-Src is not solely dependent on MAP kinase pathway. Because anchorage-independent growth correlates with tumor growth in vivo as well as metastatic potential, targeting Ras would be potentially useful for the treatment of human tumors with elevated Src tyrosine kinase activity.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

Local adenovirus-mediated transfer of C-type natriuretic peptide suppresses vascular remodeling in porcine coronary arteries in vivo

OBJECTIVE

This study was designed to examine whether or not adenovirus-mediated gene transfer of C-type natriuretic peptide (CNP) can prevent coronary restenotic changes after balloon injury in pigs in vivo.

BACKGROUND

Gene therapy to prevent restenosis after percutaneous transluminal coronary angioplasty (PTCA) might be useful but requires a method applicable for in vivo gene delivery into the coronary artery as well as the efficient vector encoding a potent antiproliferative substance. We tested whether the adenovirus-mediated gene transfer of CNP by use of an infiltrator angioplasty balloon catheter (IABC) might prevent the coronary restenotic changes after balloon injury.

METHODS

Balloon angioplasty was performed in the left anterior descending and the left circumflex coronary artery in pigs. Immediately after the balloon injury, adenovirus solution encoding either CNP (AdCACNP) or beta-galactosidase (AdCALacZ) gene was injected with IABC into the balloon-injured coronary segments. Expression of CNP was assessed by immunohistochemical staining and cyclic guanosine 3',5'-monophosphate (cGMP) measurement. Coronary restenotic changes were evaluated by both angiographic and histological examinations.

RESULTS

CNP was highly expressed in the media and the adventitia of the coronary artery at the AdCACNP-transfected but not at the AdCALacZ-transfected segment. In the AdCALacZ-transfected segment, vascular cGMP levels tended to be reduced as compared with the untreated segment, whereas in the AdCACNP-transfected segment, vascular cGMP levels were restored. Angiographic coronary stenosis was significantly less at the AdCACNP-transfected than at the AdCALacZ-transfected segment. Histological examination revealed that this was achieved primarily by the marked inhibition of the geometric remodeling of the coronary artery by the CNP gene transfer.

CONCLUSIONS

Adenovirus-mediated CNP gene transfer with the IABC system may be a useful gene therapy to prevent restenosis after PTCA in vivo.

Mechanical stretch stimulates growth of vascular smooth muscle cells via epidermal growth factor receptor

We have studied whether activation of epidermal growth factor receptor (EGFR) is involved in stretch-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation and protein synthesis in cultured rat vascular smooth muscle cells (VSMC). Cyclic stretch (1 Hz) induced a rapid (within 5 min) phosphorylation of ERK1/2, an effect that was time and strength dependent and inhibited by an EGFR kinase inhibitor (AG-1478) but not by a platelet-derived growth factor receptor kinase inhibitor (AG-1296). The stretch rapidly (within 2 min) induced tyrosine phosphorylation of several proteins, among which 180-kDa protein was shown to be EGFR as revealed by blockade with AG-1478 as well as immunoprecipitation with anti-EGFR antibody coupled with immunoblotting with anti-phosphotyrosine antibody. The stretch rapidly (within 2 min) induced association of tyrosine-phosphorylated EGFR with adaptor proteins (Shc/Grb2) as revealed by coprecipitation with glutathione-S-transferase-Grb2 fusion protein coupled with immunoblotting with anti-phosphotyrosine, anti-EGFR, and anti-Shc antibodies. Transfection of a dominant-negative mutant of H-Ras also inhibited stretch-induced ERK1/2 activation. Treatment with a stretch-activated ion channel blocker (Gd(3+)) and an intracellular Ca(2+) antagonist (TMB-8) inhibited stretch-induced phosphorylation of EGFR and ERK1/2. Treatment with AG-1478 and a mitogen-activated protein kinase kinase inhibitor (PD-98059), but not AG-1296, blocked [(3)H]leucine uptake stimulated by a high level of stretch. These data suggest that ERK1/2 activation by mechanical stretch requires Ca(2+)-sensitive EGFR activation mainly via stretch-activated ion channels, thereby leading to VSMC growth.

Hepatocyte growth factor modulates motility and invasiveness of ovarian carcinomas via Ras-mediated pathway

Hepatocyte growth factor (HGF) is a multifunctional growth factor which has pleiotrophic biological effects on epithelial cells such as proliferation, motogenesis, invasiveness and morphogenesis. Peritoneal dissemination is critical for the progression of ovarian cancer, and our study revealed that HGF induces migration and invasion of ovarian cancer cells. We also demonstrated that HGF stimulates autophosphorylation of its receptor, followed by activation of the Ras-MAP (mitogen-activated peptide) kinase cascade. Moreover, infection of ovarian cancer cells with Ras dominant-negative adenovirus reduced the HGF-induced motogenic and invasive activities. Additionally, both MEK and P13-kinase pathways downstream of Ras were involved in HGF-stimulated ovarian cancer cell invasiveness.

Effects of hydroxymethylglutaryl coenzyme A reductase inhibitor simvastatin on smooth muscle cell proliferation in vitro and neointimal formation in vivo after vascular injury

OBJECTIVES

We sought to evaluate the effects of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors on vascular smooth muscle cell (VSMC) proliferation in vitro and neointimal formation in vivo after vascular injury.

BACKGROUND

Neointimal hyperplasia after vascular injury is responsible for restenosis after arterial stenting, whereas arterial remodeling and neointimal formation are the causes of restenosis after percutaneous transluminal coronary angioplasty.

METHODS

We assessed the effect of simvastatin on in vitro VSMC proliferation. To study the effects of simvastatin in vivo, balloon injury and stent deployment were performed in the common carotid artery of rats. Neointimal area was measured two weeks later in the balloon injury model and three weeks after stent deployment.

RESULTS

Simvastatin markedly inhibits VSMC proliferation in vitro. In vivo, simvastatin reduced, in a dose-dependent manner, the neointimal area and the neointima-media ratio after balloon injury from 0.266 +/- 0.015 mm2 to 0.080 +/- 0.026 mm2 and from 1.271 +/- 0.074 to 0.436 +/- 0.158 (p < 0.001 vs. control rats) at the highest dose. Simvastatin also significantly reduced the neointimal formation and the neointima-media ratio after stenting from 0.508 +/- 0.035 mm2 to 0.362 +/- 0.047 mm2 (p < 0.05 vs. control rats) and from 2.000 +/- 0.136 to 1.374 +/- 0.180 (p < 0.05 vs. control rats). The vessel thrombosis rate after stent deployment was 30% in the control group and 11.1% in the treated group (p = NS). Moreover, the systemic administration of simvastatin did not affect hepatic and renal functions, blood pressure or heart rate.

CONCLUSIONS

Simvastatin potently inhibits VSMC proliferation in vitro and reduces neointimal formation in a rat model of vascular injury.

Intracellular signaling of angiotensin II-induced p70 S6 kinase phosphorylation at Ser(411) in vascular smooth muscle cells. Possible requirement of epidermal growth factor receptor, Ras, extracellular signal-regulated kinase, and Akt

Activation of p70 S6 kinase (p70(S6K)) by growth factors requires multiple signal inputs involving phosphoinositide 3-kinase (PI3K), its effector Akt, and an unidentified kinase that phosphorylates Ser/Thr residues (Ser(411), Ser(418), Ser(424), and Thr(421)) clustered at its autoinhibitory domain. However, the mechanism by which G protein-coupled receptors activate p70(S6K) remains largely uncertain. By using vascular smooth muscle cells in which we have demonstrated Ras/extracellular signal-regulated kinase (ERK) activation through Ca(2+)-dependent, epidermal growth factor (EGF) receptor transactivation by G(q)-coupled angiotensin II (Ang II) receptor, we present a unique cross-talk required for Ser(411) phosphorylation of p70(S6K) by Ang II. Both p70(S6K) Ser(411) and Akt Ser(473) phosphorylation by Ang II appear to involve EGF receptor transactivation and were inhibited by dominant-negative Ras, whereas the phosphorylation of p70(S6K) and ERK but not Akt was sensitive to the MEK inhibitor. By contrast, the phosphorylation of p70(S6K) and Akt but not ERK was sensitive to PI3K inhibitors. Similar inhibitory pattern on these phosphorylation sites by EGF but not insulin was observed. Taken together with the inhibition of Ang II-induced p70(S6K) activation by dominant-negative Ras and the MEK inhibitor, we conclude that Ang II-initiated activation of p70(S6K) requires both ERK cascade and PI3K/Akt cascade that bifurcate at the point of EGF receptor-dependent Ras activation.

Endothelin-mediated vascular growth requires p42/p44 mitogen-activated protein kinase and p70 S6 kinase cascades via transactivation of epidermal growth factor receptor

Endothelin-1 (ET-1), a potent endothelium-derived vasoconstrictor peptide, exerts a growth-promoting effect on vascular smooth muscle cells, implicating its pathogenic role in vascular remodeling. To gain insight into the cellular and molecular mechanism whereby ET-1 induces vascular growth, we studied whether transactivation of receptor tyrosine kinases, such as epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor, are required for activation of p42/p44 mitogen-activated protein (MAP) kinase and p70 S6 kinase (p70S6K), and subsequent growth-promotion by ET-1 in cultured rat vascular smooth muscle cells. Immunoblotting with antiphosphotyrosine antibody revealed that ET-1 rapidly (within 2 min) and transiently induced tyrosine phosphorylation of several proteins, among which 180-kDa protein was shown to be EGFR. ET-1 rapidly increased association of EGFR and Shc with glutathione-S-transferase-Grb2 fusion protein. The ET-1-induced activation of MAP kinase was reduced by an EGFR kinase inhibitor (AG1478) but not by a platelet-derived growth factor receptor kinase inhibitor (AG1296). AG1478 dose-dependently decreased ET-1-stimulated MAP kinase activity as well as [3H]leucine and [3H]thymidine uptake. The ET-1-induced tyrosine phosphorylation of EGFR, as well as MAP kinase activation, was inhibited by an ETA receptor antagonist and intracellular Ca2+ antagonists but not by an ETB receptor antagonist, pertussis toxin, or protein kinase C inhibitors. In addition, dominant negative mutant of H-Ras and a MAP kinase kinase (MEK-1) inhibitor (PD98059) completely blocked ET-1-induced MAP kinase activation as well as [3H]leucine and [3H]thymidine uptake. Both AG1478 and PD98059 inhibited ET-1-induced phosphorylation and activation of p70S6K. Furthermore, rapamycin, a selective inhibitor of mammalian target of rapamycin, completely blocked ET-1-stimulated [3H]leucine and [3H]thymidine uptake. These results suggest that ETA receptor-mediated vascular growth by ET-1 requires both MAP kinase and p70S6K cascades mediated partly via Ca2+-dependent EGFR transactivation.

Gene therapy for atherosclerosis and atherosclerosis-related diseases

Gene therapy for atherosclerosis-related disorders of lipoprotein metabolism is primarily directed to liver and aims at long-lasting correction of familial hypercholesterolemia, lipoprotein / hepatic lipase deficiency, and Apolipoprotein A, B, or E -related diseases. Treatment of complications of atherosclerosis (eg, restenosis, ischemia) requires local gene transfer to arterial wall or ischemic muscle with transient gene expression. Catheter-mediated approach or direct injections have been used in clinical trials for the treatment of restenosis and for the induction of angiogenesis in ischaemic limb and myocardium. Other possible applications of local gene transfer include antithrombotic treatment and stabilization of vulnerable plaques.

Separate roles for H-Ras and Rac in signaling by transforming growth factor (TGF)-beta. H-Ras is essential for activation of MAP kinase, partially required for transcriptional activation by TGF-beta, but not required for signaling of growth suppression by TGF-beta

The signaling components located downstream of the transforming growth factor (TGF)-beta receptor are poorly understood. We constructed adenoviral vectors expressing a dominant-negative form of either H-Ras (AdCARasY57) or Rac (AdCARacN17), and used them to examine the roles of H-Ras and Rac in TGF-beta signaling using arterial endothelial cells in primary culture, and several established cells including a mink lung epithelial cell line (Mv1Lu). The rapid activation of p42/44 MAP kinase (MAPK) by TGF-beta1 was eliminated completely, and transcriptional activation by TGF-beta1 of the plasminogen activator inhibitor-1 gene was reduced by 50% in both endothelial cells and Mv1Lu when they were infected with AdCARasY57. However, the antiproliferative effect of TGF-beta, as assessed by the induction of the mRNA for Cdk4/6-specific inhibitor p15INK4B and by DNA synthesis, was not affected in AdCARasY57-infected cells. A MAPK kinase (MEK)1/2 inhibitor, U0126 also abolished MAPK activation and partially inhibited transcriptional activation by TGF-beta, suggesting that MAPK may be partially involved in this pathway. MAPK activation, transcriptional activation and growth suppression by TGF-beta were all unaffected in cells infected with AdCARacN17, although the DNA synthesis elicited by serum mitogens was suppressed completely in the infected cells. Our data indicate that H-Ras is essential for mitogen-activated protein kinase activation, partly required for transcriptional activation by TGF-beta, but not critically involved in the signaling that exerts the antiproliferative effect of TGF-beta. The results also suggest that Rac may not serve as an essential molecule in signaling by TGF-beta in the cells tested.

Gene therapy as a therapeutic intervention for vascular disease

Gene therapy for the treatment of many medical problems, including vascular disease, has become the subject of increasing discussion in both the scientific literature and the national press over the past decade. This review will examine the history and current status of gene therapy for vascular proliferative disorders and advanced chronic peripheral and cardiac ischemia.