Mithramycin inhibits myointimal proliferation after balloon injury of the rat carotid artery in vivo

Wound Healing-related Functions of the p160 Steroid Receptor Coactivator Family

Multicellular organisms have evolved sophisticated mechanisms to recover and maintain original tissue functions following injury. Injury responses require a robust transcriptomic response associated with cellular reprogramming involving complex gene expression programs critical for effective tissue repair following injury. Steroid receptor coactivators (SRCs) are master transcriptional regulators of cell-cell signaling that is integral for embryogenesis, reproduction, normal physiological function, and tissue repair following injury. Effective therapeutic approaches for facilitating improved tissue regeneration and repair will likely involve temporal and combinatorial manipulation of cell-intrinsic and cell-extrinsic factors. Pleiotropic actions of SRCs that are critical for wound healing range from immune regulation and angiogenesis to maintenance of metabolic regulation in diverse organ systems. Recent evidence derived from studies of model organisms during different developmental stages indicates the importance of the interplay of immune cells and stromal cells to wound healing. With SRCs being the master regulators of cell-cell signaling integral to physiologic changes necessary for wound repair, it is becoming clear that therapeutic targeting of SRCs provides a unique opportunity for drug development in wound healing. This review will provide an overview of wound healing-related functions of SRCs with a special focus on cellular and molecular interactions important for limiting tissue damage after injury. Finally, we review recent findings showing stimulation of SRCs following cardiac injury with the SRC small molecule stimulator MCB-613 can promote cardiac protection and inhibit pathologic remodeling after myocardial infarction.

Long noncoding RNA XXYLT1-AS2 regulates proliferation and adhesion by targeting the RNA binding protein FUS in HUVEC

BACKGROUND AND AIMS

The endothelium is crucially involved in the pathogenesis of atherosclerosis according to accumulating evidence. Moreover, recent studies have showed that lncRNAs could serve as biomarkers of cardiovascular diseases, in particular atherosclerosis. However, the underlying mechanism of endothelial dysfunction involving lncRNAs in atherosclerosis remains unknown. This study investigated the mechanism of lncRNA XXYLT1-AS2 in endothelial dysfunction in atherosclerosis.

METHODS

The levels of lncRNA XXYLT1-AS2, FUS, VCAM-1, MCP-1, p-AKT, and p-P65 were measured in arteries and HUVEC cell lines via quantitative real-time PCR or Western blot. FISH assay demonstrated that XXYLT1-AS2 and FUS are localized in the nucleus. HUVECs were transfected with si-XXYLT1-AS2 or XXYLT1-AS2 to further assess cell proliferation, migration, and adhesion. Furthermore, bioinformatics analysis, RNA immunoprecipitation and immunofluorescence were performed to investigate the target genes of XXYLT1-AS2 and possible signal pathways.

RESULTS

Overexpression of XXYLT1-AS2 inhibited cell proliferation and migration, reduced the expression of adhesion molecules (VCAM-1) and chemoattractant proteins (MCP-1), and restrained monocyte adhesion to endothelial cells. Mechanistic investigations indicated that XXYLT1-AS2 directly interacts with the target gene FUS/cyclin D1 and modulates the proliferation and migration of endothelial cells (ECs). Moreover, XXYLT1-AS2 exerts a protective role against the inflammatory response in atherosclerosis by blocking NF-κB activity. Clinically, the involvement of XXYLT1-AS2/FUS was also observed in human arteries and the results were consistent with the in vitro analysis.

CONCLUSIONS

Our study identified a novel long non-coding RNA (XXYLT1-AS2) and suggests that it might act as an underlying therapeutic target in atherosclerosis-related diseases by regulating ECs functions.

Inhibitory Effects of Bezoar Bovis on Intimal Formation and Vascular Smooth Muscle Cell Proliferation in Rat

Intimal formation of animal carotid arteries induced by balloon endothelial denudation has been considered to be an "accelerated atherosclerosis" model and used in primary screening methods to evaluate natural drugs and chemical candidates. The aim of the present study was to examine whether intimal formation is prevented by Bezoar Bovis (dried cattle gallbladder stones: Niuhuang in Chinese and Go-o in Japanese), which has been used to prevent heart palpitation in patients with hypertension. The intimal-to-medial area ratio in rat carotid arteries 7 days after balloon endothelial denudation was significantly reduced by oral administration of Bezoar Bovis. Bezoar Bovis also suppressed vascular smooth muscle cells (VSMCs) proliferation, which is thought to play important roles in the intimal formation after endothelial damage and also atherosclerosis resulting from long-term inappropriate lifestyle. The present findings suggest that Bezoar Bovis may be useful for preventing atherosclerosis and for protection against restenosis after percutaneous coronary intervention, for which effective reduction method is not currently available.

c-myc and skp2 coordinate p27 degradation, vascular smooth muscle proliferation, and neointima formation induced by the parathyroid hormone-related protein

Parathyroid hormone-related protein (PTHrP) contains a classical bipartite nuclear localization signal. Nuclear PTHrP induces proliferation of arterial vascular smooth muscle cells (VSMC). In the arterial wall, PTHrP is markedly up-regulated in response to angioplasty and promotes arterial restenosis. PTHrP overexpression exacerbates arterial restenosis, and knockout of the PTHrP gene results in decreased VSMC proliferation in vivo. In arterial VSMC, expression of the cell cycle inhibitor, p27, rapidly decreases after angioplasty, and replacement of p27 markedly reduces neointima development. We have shown that PTHrP overexpression in VSMC leads to p27 down-regulation, mostly through increased proteosomal degradation. Here, we determined the molecular mechanisms through which PTHrP targets p27 for degradation. S-phase kinase-associated protein 2 (skp2) and c-myc, two critical regulators of p27 expression and stability, and neointima formation were up-regulated in PTHrP overexpression in VSMC. Normalization of skp2 or c-myc using small interfering RNA restores normal cell cycle and p27 expression in PTHrP overexpression in VSMC. These data indicate that skp2 and c-myc mediate p27 loss and proliferation induced by PTHrP. c-myc promoter activity was increased, and c-myc target genes involved in p27 stability were up-regulated in PTHrP overexpression in VSMC. In primary VSMC, PTHrP overexpression led to increased c-myc and decreased p27. Conversely, knockdown of PTHrP in primary VSMC from PTHrP(flox/flox) mice led to cell cycle arrest, p27 up-regulation, with c-myc and skp2 down-regulation. Collectively, these data describe for the first time the role of PTHrP in the regulation of skp2 and c-myc in VSMC. This novel PTHrP-c-myc-skp2 pathway is a potential target for therapeutic manipulation of the arterial response to injury.

The herbal extract HMC05 inhibits neointima formation in balloon-injured rat carotid arteries: possible therapeutic implications of HMC05

AIM OF THE STUDY

In a previous study, HMC05, a water extract from eight medicinal herbs was demonstrated to possess anti-inflammatory effects in murine macrophages and anti-atherosclerotic effects in apoE(-/-) mice. HSP27 expression was shown to be decreased in advanced atherosclerotic plaques of human carotid arteries. In the present study, the role of HMC05 in the prevention of restenosis and the possible mechanisms involved in the decrease of neointima formation were investigated using in vivo balloon injury rat model and in vitro biochemical assays.

MATERIALS AND METHODS

A rat carotid artery balloon injury restenosis model was used. Different doses of HMC05 were administered to the rats by tube feeding, starting from four days before surgery and continuing twice per week for two weeks after carotid injury. Injured carotid arteries isolated from rats were embedded in paraffin block and tissue sections were stained with H&E to assess neointima formation. Mechanism by HMC05 that are involved in smooth muscle cell proliferation and migration was assessed by western blot assay, immunohistochemistry and confocal analysis.

RESULTS

There was no significant difference in the medial area between the control and HMC05-treated groups. However, neointima formation was significantly inhibited in the HMC05-treated group, resulting in 47-fold lower intima to media ratios in rats treated with 25 mg/kg/day HMC05 as compared to the control. Surprisingly, monocytes infiltration in the neointima area was almost completely blocked by HMC05 administration. When rat vascular SMCs were treated with HMC05, the proliferation and migration of smooth muscle cells was dramatically inhibited in a dye uptake assay and in a scratch model in a culture dish, respectively. HMC05 dose-dependently inhibited PDGF-mediated MAPK and AKT activation. However, HMC05 did not affect PDGF-mediated HSP27 phosphorylation but it induced HSP27 overexpression and phosphorylation. In addition, medial SMCs in the arterial wall of rats treated with HMC05 showed a significant increase in HSP27 expression compared with that of the control rats.

CONCLUSIONS

HMC05, a strong anti-inflammatory reagent, might use HSP27 as an effector molecule in SMCs to reduce neointimal hyperplasia by inhibiting PDGF-mediated MAPK and AKT activation. HMC05 could be a useful drug candidate for the prevention of restenosis after balloon injury of the arteries.

Single and double emulsion manufacturing techniques of an amphiphilic drug in PLGA nanoparticles: formulations of mithramycin and bioactivity

Formulation of hydrophilic compounds in nanoparticles is problematic due to their escape to the external aqueous phase. The certain amphiphilic nature of mithramycin, utilized clinically in cancer, makes its incorporation into nanoparticles an interesting challenge, elucidating the formulation factors of amphiphilics in nanoparticles. We hypothesized that mithramycin nanoparticles could provide more effective therapy of restenosis due to its antiproliferating and potential monocyte inhibition properties. The nanoprecipitation technique (designed for lipophilic compounds) was found preferable, with better encapsulation efficiency, than the emulsification solvent diffusion (ESD) technique (79.3 +/- 3.1% and 40.8 +/- 1.1%, respectively). The double emulsion solvent diffusion (DESD) method, designed for hydrophilic compounds, yielded similar encapsulation efficiency (80%). Nanoparticles size was, 110 +/- 36, 130 +/- 30, and 160 +/- 31 nm, ESD, nanoprecipitation, and DESD techniques, respectively. Mithramycin solution and in nanoparticles significantly inhibited RAW264 macrophages and smooth muscle cells in a dose-dependent relationship, and reduced the number of circulating monocytes in rabbits. However, no inhibition of restenosis was obtained in the rat carotid model following i.v. administration of mithramycin nanoparticles. It can be concluded that PLGA-based polymeric nanoparticles of mithramycin can be formulated by techniques suitable for lipophilic/hydrophilic compounds. The ineffectiveness in the rat restenosis model is probably due to the short depletion period of circulating monocytes and lack of arterial targeting.

Coronary vein graft disease: pathogenesis and prevention

Not long after coronary artery bypass grafting surgery was described, several reports presented follow-up angiographic data on large cohorts of patients, demonstrating that approximately one-half of saphenous vein grafts fail within 10 to 15 years of surgery and that graft failure is associated with worse clinical outcomes. Three processes are responsible for vein graft failure. Thrombosis, intimal hyperplasia and accelerated atherosclerosis contribute to graft failure in the acute, subacute and late postoperative periods, respectively. Studies have shown that perioperative antiplatelet therapy can reduce early thrombosis and graft failure. As in native coronaries, intensive lipid lowering can attenuate the process of atherosclerosis in vein grafts. Intimal hyperplasia in the vein graft is thought to be an adaptation of the vein to higher pressures in the arterial circulation. This process is further promoted by the loss of inhibition from the endothelial layer, which is injured during surgery. A new 'no-touch' technique for harvesting grafts may be effective in preventing disruption to the endothelial layer, and subsequent intimal hyperplasia and graft loss. Off-pump surgery and endoscopic vein harvesting, which are known to reduce surgical morbidity, have been shown to be no worse than on-pump surgery and open vein harvesting, respectively, in terms of vein graft patency. Various gene therapies can prevent intimal hyperplasia in animal models, but human data obtained so far have been disappointing. Placing an external stent around a vein graft may reduce tangential wall stress and subsequent intimal hyperplasia.

Cellular mechanisms underlying the cardiovascular actions of oestrogens

Although pre-menopausal women enjoy relative cardiovascular protection, hormone (oestrogen±progestin)-replacement therapy has not shown cardiovascular benefits in post-menopausal women, suggesting that the effects of oestrogens on the cardiovascular system are much more complex than previously expected. Endothelial cells, smooth muscle cells, cardiac myocytes and fibroblasts, the cellular components of blood vessels and the heart, play important roles in cardiovascular health and disease. During the development and progression of cardiovascular disease, changes occur both in the structure and function of these cells, resulting in a wide range of abnormalities, which affect growth, death and physiological function. These cells contain functional oestrogen receptors and are targets for oestrogen action. This review focuses on recent studies on the effects of oestrogen on cardiovascular cell function. Oestrogens, particularly 17β-oestradiol, exert multiple effects on cardiovascular cells, and these effects may contribute to the gender-associated protection against cardiovascular diseases.

Novel GC-rich DNA-binding compound produced by a genetically engineered mutant of the mithramycin producer Streptomyces argillaceus exhibits improved transcriptional repressor activity: implications for cancer therapy

The aureolic acid antibiotic mithramycin (MTM) binds selectively to GC-rich DNA sequences and blocks preferentially binding of proteins, like Sp1 transcription factors, to GC-rich elements in gene promoters. Genetic approaches can be applied to alter the MTM biosynthetic pathway in the producing microorganism and obtain new products with improved pharmacological properties. Here, we report on a new analog, MTM SDK, obtained by targeted gene inactivation of the ketoreductase MtmW catalyzing the last step in MTM biosynthesis. SDK exhibited greater activity as transcriptional inhibitor compared to MTM. SDK was a potent inhibitor of Sp1-dependent reporter activity and interfered minimally with reporters of other transcription factors, indicating that it retained a high degree of selectivity toward GC-rich DNA-binding transcription factors. RT-PCR and microarray analysis showed that SDK repressed transcription of multiple genes implicated in critical aspects of cancer development and progression, including cell cycle, apoptosis, migration, invasion and angiogenesis, consistent with the pleiotropic role of Sp1 family transcription factors. SDK inhibited proliferation and was a potent inducer of apoptosis in ovarian cancer cells while it had minimal effects on viability of normal cells. The new MTM derivative SDK could be an effective agent for treatment of cancer and other diseases with abnormal expression or activity of GC-rich DNA-binding transcription factors.

Bofutsushosan, a traditional Chinese formulation, prevents intimal thickening and vascular smooth muscle cell proliferation induced by balloon endothelial denudation in rats

Bofutsushosan (BOF), a traditional Chinese formulation (Kampo formulation in Japanese), is widely used for patients with obesity and hyperlipidemia resulting from long-term inappropriate lifestyles. Since atherosclerosis, a lifestyle-related disease, is accompanied by an abnormal accumulation of vascular smooth muscle cells (VSMCs) in the intimal area of the artery, we investigated the preventive effect of BOF on intimal thickening. Oral administration of BOF extracts 3 d before and 7 d after balloon endothelial denudation dose dependently suppressed the intimal thickening and proliferation of VSMCs in the intimal area in rat carotid arteries. This model has a similar pathologic process to atherosclerosis and is considered to be an "accelerated atherosclerosis" model. BOF extract also dose dependently inhibited the migration of cultured VSMCs. BOF extract suppressed serum lipid levels, which are a major risk factor for atherosclerosis. These findings clarified the usefulness of BOF in cardiovascular risk-reduction therapy.

Inhibition of collagen gene expression in systemic sclerosis dermal fibroblasts by mithramycin

BACKGROUND

The anti-tumour antibiotic mithramycin is also a potent inhibitor of fibrosis after glaucoma surgery. This drug displays high affinity binding to GC-rich sequences in DNA, including those present in the promoter of the gene encoding the alpha1 chain of type I collagen (COL1A1).

OBJECTIVE

To evaluate the effects of mithramycin on COL1A1 expression in systemic sclerosis fibroblasts.

METHODS

Confluent cultures of dermal fibroblasts from patients with recent onset diffuse systemic sclerosis were treated with mithramycin in vitro. Cell viability and protein expression were examined by fluorescence and confocal imaging. Type I collagen production was analysed by confocal imaging and metabolic labelling. COL1A1 messenger RNA levels and stability were assessed by northern hybridisation, and COL1A1 transcription was examined by transient transfections.

RESULTS

Treatment of systemic sclerosis fibroblasts with mithramycin (10-100 nmol/l) did not cause significant cytotoxicity. Type I collagen biosynthesis decreased by 33-40% and 50-70% in cells cultured with mithramycin at 10 nmol/l and 100 nmol/l, respectively. Mithramycin at 50 nmol/l decreased COL1A1 mRNA levels by 40-60%. The effects of mithramycin on collagen gene expression were mediated by transcriptional and post-transcriptional mechanisms as shown by the reduction of COL1A1 promoter activity and by a decrease in the stability of these transcripts, respectively.

CONCLUSIONS

Mithramycin causes potent inhibition of collagen production and gene expression in systemic sclerosis dermal fibroblasts in vitro in the absence of cytotoxic effects. These results suggest that this drug may be an effective treatment for the fibrotic process which is the hallmark of systemic sclerosis.

Inhibition of vascular smooth muscle cell migration by serum from rats treated orally with Saiko-ka-Ryukotsu-Borei-To, a traditional Chinese formulation

Oral administration of Saiko-ka-Ryukotsu-Borei-To (SRB), a traditional Chinese formulation, has been found to prevent intimal thickening of the carotid artery after balloon endothelial denudation in cholesterol-fed rats. To clarify the mechanism of this effect, the present study investigated if SRB inhibits vascular smooth muscle cell (VSMC) migration, which plays an important role in the development of intimal thickening after endothelial injury. The serum (SRB serum) sampled from cholesterol-fed rats treated orally with SRB for 3 days before and 4 days after the injury dose-dependently inhibited the migration of cultured VSMCs. When added directly to cultured VSMCs, the SRB extract did not inhibit VSMC migration. It is remarkable that SRB serum, which may contain a much lower concentration of SRB ingredients compared with the SRB extract, inhibited cultured VSMC migration. The present testing system using serum obtained from animals treated orally with traditional Chinese formulations may be useful for clarifying the pharmacological efficacy of such drugs, including many non-absorbable components. Furthermore, it may be useful in the search for new active compounds in serum after oral administration of traditional Chinese formulations, the active metabolites of which have not been identified.

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.

Structure and function of "metalloantibiotics"

Although most antibiotics do not need metal ions for their biological activities, there are a number of antibiotics that require metal ions to function properly, such as bleomycin (BLM), streptonigrin (SN), and bacitracin. The coordinated metal ions in these antibiotics play an important role in maintaining proper structure and/or function of these antibiotics. Removal of the metal ions from these antibiotics can cause changes in structure and/or function of these antibiotics. Similar to the case of "metalloproteins," these antibiotics are dubbed "metalloantibiotics" which are the title subjects of this review. Metalloantibiotics can interact with several different kinds of biomolecules, including DNA, RNA, proteins, receptors, and lipids, rendering their unique and specific bioactivities. In addition to the microbial-originated metalloantibiotics, many metalloantibiotic derivatives and metal complexes of synthetic ligands also show antibacterial, antiviral, and anti-neoplastic activities which are also briefly discussed to provide a broad sense of the term "metalloantibiotics."

Saiko-ka-Ryukotsu-Borei-To inhibits intimal thickening in carotid artery after balloon endothelial denudation in cholesterol-fed rats

Oral administration of Saiko-ka-Ryukotsu-Borei-To (SRB), a traditional Chinese formulation, dose dependently inhibited intimal thickening in carotid artery injured by balloon endothelial denudation in cholesterol-fed rats. SRB also inhibited vascular smooth muscle cell (VSMC) proliferation, which is assessed by counting the VSMCs immunoreactive with antiproliferating cell nuclear antigen (PCNA) antibody in the intimal area. VSMC proliferation is considered to play a central role in the development of intimal thickening. SRB slightly, but not significantly, reduced serum total cholesterol and low-density lipoprotein cholesterol. These results indicate that the suppressive effect of SRB on intimal thickening may result from its inhibitory effect against VSMC proliferation, but does not depend on lowering of lipid levels. The balloon injury model used in this study has similar pathological processes to restenosis after percutaneous coronary intervention (PCI). Therefore the present results may provide a new therapeutic strategy using SRB to reduce restenosis after PCI in the treatment of patients with ischemic coronary artery disease. Furthermore, since it is considered that artery restenosis after balloon injury in PCI is "accelerated atherosclerosis, " SRB may have beneficial effects in atherosclerosis that develops over a long clinical course in hyperlipidemia, diabetes, etc.

Local delivery of mithramycin restores vascular reactivity and inhibits neointimal formation in injured arteries and vascular grafts

Arterial restenosis is responsible for the high failure rates of vascular reconstruction procedures. Local sustained drug delivery has shown promise in the prevention of restenosis. The drug release rate from mithramycin-loaded EVA matrices (0.1%) was evaluated, and their antirestenotic effect was studied in the rat carotid model and rabbit model of vascular grafts. The modulation of c-myc expression by mithramycin treatment was examined by immunohistochemistry in the rat carotid model. The proliferative response of injured rat arteries was studied by bromdeoxyuridine (BrdU) immunostaining. The impact of mithramycin treatment on vasomotor responses of the venous segments grafted into arterial circulation was studied ex vivo using vasoreactive compounds. Mithramycin was released exponentially from EVA matrices in PBS. Matrices co-formulated with PEG-4600 revealed enhanced release kinetics. The perivascular implantation of drug-loaded EVA-PEG matrices led to 50% reduction of neointimal formation, and reduced the c-myc expression and BrdU labeling in comparison to control implants. Decreased sensitivity of mithramycin-treated grafts to serotonin-induced vasoconstriction was observed. Local perivascular mithramycin treatment limits the functional alteration caused by the grafting of venous segments in high-pressure arterial environment, and potently inhibits stenosis secondary to grafting and angioplasty injury. The antirestenotic effect is associated with reduced c-myc expression and with subsequent decrease in SMC proliferation.

Restenosis: a challenge for pharmacology

The quest for an anti-restenotic drug continues to be a major challenge in the field of cardiovascular pharmacology because most therapies with proven efficacy in experimental neointima models have failed to limit restenosis. Some drug classes, including glycoprotein IIb/IIIa antagonists, nitric oxide donors and the antioxidant probucol, have recently demonstrated potential benefits in clinical trials. Progress in the development of local delivery systems for administration of drugs, antisense oligonucleotides or genes, in combination with an improved understanding of the pathogenesis of restenosis holds promise for ultimate pharmacotherapy of this condition.

Limitations of angiotensin-converting enzyme inhibitor in restenosis of a deep arterial injury model

Cilazapril (CLZ) has been reported to reduce intimal hyperplasia in a rat carotid model of restenosis. The purpose of this study was to determine whether CLZ inhibits restenosis after deep arterial injury in lathyritic rats. The lathyritic rat was used as a model of deep arterial injury; in this model the internal elastic lamina is easily broken by balloon injury because of the fragility of the connective tissue. Deep arterial injury is defined as rupture of the internal elastic lamina with damage to both the intima and the media. The rats were divided into 4 groups (n = 40): mild injury (intimal damage with intact internal elastic lamina), mild injury +CLZ, deep injury, and deep injury +CLZ. In the CLZ-treated groups, the drug was administered orally (10 mg/day) from 7 days before balloon injury until the time of sacrifice 21 days after balloon injury. The intimal hyperplasia was determined histologically using a computerized morphometry program. At sacrifice, blood pressure was lower in the CLZ-treated groups than in the untreated (control) rats (p < 0.05). In the mild injury model, CLZ decreased intimal hyperplasia markedly. In contrast, CLZ failed to reduce intimal hyperplasia in the rats with deep injury. CLZ markedly decreased neointimal hyperplasia in mild injury. In contrast, CLZ failed to reduce intimal area in deep injury. The type of arterial injury seems to determine the effectiveness of CLZ.

Restenosis: is there a pharmacologic fix in the pipeline?

One of the most frustrating aspects of restenosis is that it is the result of advances in medical care (there was no restenosis before the days of balloon angioplasty), yet it seems to be resistant to all that science has to offer. Still we believe there is reason to be optimistic. We are at last beginning to see some promise from clinical trials, and data being generated confirm some of the hypotheses previously generated from animal experiments. Thus the effects seen with the GP IIb/IIIa antibody 7E3 suggest that thrombosis may be as important in its long-term sequelae as it is for acute reocclusion. The jury is still out on whether antiproliferative approaches will be a therapeutic option, but local delivery paradigms using novel formulations delivered by catheter or impregnated in stents may allow the concept to be tested without the risk of systemic toxicity. Plans are also underway for gene therapy trials, although we may have to wait for better vector technology before taking these into the coronary bed. Perhaps we should move away from the "single pill" approach and accept that, like many infections, malignancies, or even heart failure, a multifaceted approach with combination therapy will provide the first glimmer of that brighter tomorrow.

Troglitazone inhibits vascular smooth muscle cell growth and intimal hyperplasia

Vascular smooth muscle cell (VSMC) proliferation and migration are responses to arterial injury that are highly important to the processes of restenosis and atherosclerosis. In the arterial balloon injury model in the rat, platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) are induced in the vessel wall and regulate these VSMC activities. Novel insulin sensitizing agents, thiazolidinediones, have been demonstrated to inhibit insulin and epidermal growth factor-induced growth of VSMCs. We hypothesized that these agents might also inhibit the effect of PDGF and bFGF on cultured VSMCs and intimal hyperplasia in vivo. Troglitazone (1 microM), a member of the thiazolidinedione class, produced a near complete inhibition of both bFGF-induced DNA synthesis as measured by bromodeoxyuridine incorporation (6.5+/-3.9 vs. 17.6+/-4.3% cells labeled, P < 0.05) and c-fos induction. This effect was associated with an inhibition (by 73+/-4%, P < 0.01) by troglitazone of the transactivation of the serum response element, which regulates c-fos expression. Inhibition of c-fos induction by troglitazone appeared to occur via a blockade of the MAP kinase pathway at a point downstream of MAP kinase activation by MAP kinase kinase. At this dose, troglitazone also inhibited PDGF-BB-directed migration of VSMC (by 70+/-6%, P < 0.01). These in vitro effects were operative in vivo. Quantitative image analysis revealed that troglitazone-treated rats had 62% (P < 0.001) less neointima/media area ratio 14 d after balloon injury of the aorta compared with injured rats that received no troglitazone. These results suggest troglitazone is a potent inhibitor of VSMC proliferation and migration and, thus, may be a useful agent to prevent restenosis and possibly atherosclerosis.