Prevention of restenosis with antioxidants: mechanisms and implications

Association between Oxidative Burden and Restenosis: A Case-Control Study

Background

In-stent restenosis (ISR) is an important clinical complication that occurs following stent implantation. The application of drug-eluting stents (DES) and even consumption of drugs such as antiplatelet agents and statins are not completely effective in reducing ISR risk. Since the number of these patients continues to rise, it is pivotal to detect patients who are at a higher risk of ISR. In addition, identification of biochemical markers of ISR could give the right perspective on choosing the proper strategy to treat these patients. Several pathophysiological pathways including oxidative stress (OS) are implicated in the progression of ISR. Hence, this study aimed to evaluate the association between oxidative/anti-oxidative markers and ISR.

Methods

This was a case-control study which comprised 21 ISR, 26 NISR (non-ISR), and 20 healthy subjects. The serum levels of OS markers including malondialdehyde (MDA), thiol groups (GSH), total antioxidant capacity (TAC), and the activity of serum antioxidant enzymes such as glutathione peroxidase (GPx) and superoxide dismutase (SOD) were assessed by colorimetric methods. The overall oxidative burden was assessed using a pro-oxidant-antioxidant balance (PAB) assay.

Results

MDA levels were considerably higher in the ISR group when compared to healthy subjects (P = 0.004). PAB also indicated significantly higher values in both ISR (P < 0.001) and NISR (P < 0.001) groups related to healthy subjects. No significant differences were observed between the studied groups regarding thiol levels, antioxidant enzyme activities, and TAC. Multinomial logistic regression analysis showed that elevated serum levels of MDA (OR: 1.028, 95% CI: 1.008-1.048; P = 0.006) and PAB (OR: 1.076, 95% CI: 1.017-1.139; P = 0.011) were significantly associated with higher ISR risk; however, increased values of TAC (OR: 0.990, 95% CI: 0.982-0.999; P = 0.030) were significantly associated with decreased ISR risk, while after adjustment for confounders, only SOD activity (OR: 0.0, 95% CI: 0.0-0.0; P < 0.001) and PAB value (OR: 1.866, 95% CI: 1.856-1.900; P < 0.001) showed association with ISR risk.

Conclusion

According to the present findings, some oxidative and antioxidative markers like PAB and SOD activity showed the potential in the prediction of ISR risk.

Protective effect of a hydrogen sulfide donor on balloon injury-induced restenosis via the Nrf2/HIF-1α signaling pathway

Restenosis is liable to occur following treatment with endovascular interventional therapy. Increasing evidence indicates that hydrogen sulfide (H₂S) exhibits numerous physiological properties, including antioxidative and cardioprotective disease properties. Thus, the present study aimed to investigate the anti-restenosis effects of H₂S and its protective mechanisms. A balloon dilatation restenosis model was used, in which model Sprague-Dawley rats were treated with sodium hydrosulfide (NaHS: A donor of H₂S, 30 µmol/kg) by intraperitoneal injection for 4 weeks. Histological observations of the carotid artery were performed, and H₂S production and the expression of Nuclear factor-E2-related factor 2 (Nrf2)/hypoxia-inducible factor (HIF)-1α signaling pathway proteins were measured. In addition, human umbilical vein endothelial cells (HUVECs) were treated with NaHS following the inhibition of Nrf2 or HIF-1α expression. The expression of Nrf2/HIF-1α signaling pathway proteins, tube formation and cell migration were evaluated thereafter. The results demonstrated that NaHS treatment significantly increased H₂S production in rats with restenosis, and that neointimal thickness decreased significantly in arteries with restenosis. Furthermore, an increase in H₂S production enhanced the nuclear accumulation of Nrf2 and expression of its downstream targets, heme oxygenase-1 and superoxide dismutase, as well as HIF-1α. Similar effects of NaHS on the expression of these proteins were observed in HUVECs. Additionally, these findings indicated that NaHS-induced HIF-1α expression was dependent on Nrf2 expression. NaHS treatment also markedly increased tube formation by upregulating vascular endothelial growth factor expression and cell migration, both of which were mediated by the Nrf2/HIF-1α signaling pathway, and suppressed the migration and proliferation of human vascular smooth muscle cells. Thus, NaHS-mediated H₂S production was observed to prevent neointimal hyperplasia, promote activation of the Nrf2/HIF-1α signal pathway, and enhance HUVEC tube formation and migration, thereby exerting protective effects on balloon injury-induced restenosis.

Linagliptin protects rat carotid artery from balloon injury and activates the NRF2 antioxidant pathway

Percutaneous coronary intervention (PCI) is main treatment for acute coronary syndrome (ACS). However, restenosis caused by PCI-induced injury influences the outcome of patients. Linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has been reported to ameliorate intimal hyperplasia post vascular injury. The underlying mechanisms by which linagliptin protects against balloon injury are unclear and require to be explored. Herein, Wistar rats with carotid artery balloon injury were given 1, 2 or 3 mg/kg/day linagliprin for 6 weeks. We found that linagliptin attenuated vascular injury-mediated neointima formation in rats without affecting body weight and blood glucose levels. ELISA results indicated that linagliptin significantly reduced overproduction of cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 post balloon injury. By detecting the level of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), we found that linagliptin prevented balloon injury-induced oxidative stress. Additionally, linagliptin decreased the level of Kelch ECH-associating protein 1 (KEAP1) compared with injury group. Results of Western blots and electrophoretic mobility shift assay (EMSA) demonstrated that linagliptin augmented nuclear accumulation of nuclear factor-E2-related factor 2 (NRF2) and its binding ability to target genes in rats with balloon injury. Moreover, heme oxygenase-1 (HO-1) and NAD (P) H quinine oxidoreductase 1 (NQO1), two downstream targets of NRF2, were further up-regulated after linagliptin treatment compared with injury group. In conclusion, our data suggest that linagliptin protects carotid artery from balloon injury-induced neointima formation and activates the NRF2 antioxidant pathway.

Design, Synthesis, and In Vitro Evaluation of a Novel Probucol Derivative: Protective Activity in Neuronal Cells Through GPx Upregulation

Recent studies have shown that probucol (PB), a hipocholesterolemic agent with antioxidant and anti-inflammatory properties, presents neuroprotective properties. On the other hand, adverse effects have limited PB's clinical application. Thus, the search for PB derivatives with no or less adverse effects has been a topic of research. In this study, we present a novel organoselenium PB derivative (RC513) and investigate its potential protective activity in an in vitro experimental model of oxidative toxicity induced by tert-butyl hydroperoxide (tBuOOH) in HT22 neuronal cells, as well as exploit potential protective mechanisms. tBuOOH exposure caused a significant decrease in the cell viability, which was preceded by (i) increased reactive species generation and (ii) decreased mitochondrial maximum oxygen consumption rate. RC513 pretreatment (48 h) significantly prevented the tBuOOH-induced decrease of cell viability, RS generation, and mitochondrial dysfunction. Of note, RC513 significantly increased glutathione peroxidase (GPx) activity and mRNA expression of GPx1, a key enzyme involved in peroxide detoxification. The use of mercaptosuccinic acid, an inhibitor of GPx, significantly decreased the protective activity of RC513 against tBuOOH-induced cytotoxicity in HT22 cells, highlighting the importance of GPx upregulation in the observed protection. In summary, the results showed a significant protective activity of a novel PB derivative against tBuOOH-induced oxidative stress and mitochondrial dysfunction, which was related to the upregulation of GPx. Our results point to RC513 as a promising neuroprotective molecule, even though studies concerning potential beneficial effects and safety aspects of RC513 under in vivo conditions are well warranted.

Protective effects of Arctium lappa L. root extracts (AREs) on high fat diet induced quail atherosclerosis

BACKGROUND

This study was designed to evaluate the protective effects of Arctium lappa L. root extracts (AREs) from different extraction methods (aqueous, ethanol, chloroform and flavone) on atherosclerosis.

METHODS

Quails (Coturnix coturnix) were subjected to high fat diet, with or without one of the four different AREs or positive control simvastatin. Blood samples were collected before treatment, after 4.5 weeks or ten weeks to assess lipid profile (Levels of total cholesterol (TC), Triacylglycerol (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL)). After ten weeks, the serum levels of nitric oxide (NO) as well as antioxidant and pro-oxidative status (Levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione peroxidase (GSH-Px)) were measured. Furthermore, aortas were collected after ten weeks treatment, aorta lipid contents (TC, TG and LDL) were assessed, and histology was used to confirm atherosclerotic changes.

RESULTS

The results indicated that high fat diet significantly deteriorated lipid profile and antioxidant status in quail serum, while all the extracts significantly reverted the changes similar to simvastatin. Aorta lipid profile assessment revealed similar results. Histology on aortas from quails treated for ten weeks confirmed atherosclerotic changes in high fat diet group, while the extracts significantly alleviated the atherosclerotic changes similar to simvastatin. Among the different extracts, flavones fraction exerted best protective effects.

CONCLUSIONS

Our data suggest that the protective effects of AREs were medicated via hypolipidemic and anti-oxidant effects. Underlying molecular mechanisms are under investigation.

Oligoproline-derived nanocarrier for dual stimuli-responsive gene delivery

Gene therapy is a promising method for the treatment of vascular disease; however, successful strategies depend on the development of safe and effective delivery technologies with specific targeting to a diseased point of vasculature. Reactive oxygen species (ROS) are overproduced by vascular smooth muscle cells (VSMCs) at critical stages of atherosclerosis progression. Therefore, ROS were exploited as a stimulus for vascular targeted gene delivery in this study. A combination of bio-conjugation methods and controlled reverse addition-fragmentation chain-trasfer (RAFT) polymerization was utilized to synthesize a new ROS-cleavable, pH-responsive mPEG₁₁₃-b-CP₅K-b-PDMAEMA₄₂-b-P(DMAEMA₂₂-co-BMA₄₀-co-PAA₂₄) (PPDDBP) polymer as a nanocarrier for plasmid DNA (pDNA) delivery. The ros degradability of PPDDBP polymers was confirmed by SIN-1-mediated cleavage of CP₅K peptide linkers through a shift in GPC chromatogram with an appearance of mPEG shoulder peak and an increase in zeta potential (ζ). The polyplex nanocarrier also demonstrated effective PDNA loading, serum stability, and hemocompatibility, indicating its excellent performance under physiological conditions. The polyplexes demonstrated ideal pH responsiveness for endosomal escape and effective ROS responsiveness for improved targeting in an in vitro model of pathogenic VSMCs in terms of both uptake and expression of reporter gene. These data suggest this novel nanocarrier polyplex system is a promising gene delivery tool for preventing or treating areas of high ROS, such as atherosclerotic lesions.

Vascular protectants for the treatment of atherosclerosis

AGI-1067, the monosuccinic acid ester of probucol, is a phenolic antioxidant member of a novel class of agents termed vascular protectants. It has strong antioxidant properties, equipotent to those of probucol, and anti-inflammatory properties. It inhibits gene expression of vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 and has been effective at preventing atherosclerosis in all tested animal models. It also improved luminal dimensions of reference segments in the percutaneous coronary intervention (PCI) vessels in the CART-1 clinical trial, which suggests a direct anti-atherosclerosis effect. Two important trials that test the antioxidant/anti-inflammatory hypothesis are ongoing with AGI-1067: the Canadian Atherosclerosis and Restenosis Trial, which assesses its value for the reduction of both atherosclerosis progression in non-PCI vessels and post-PCI restenosis, and the Aggressive Reduction of Inflammation Stops Events trial, which is evaluating the effects of AGI-1067 on hard cardiovascular outcomes.

Symptoms of disturbed sleep predict major adverse cardiac events after percutaneous coronary intervention

BACKGROUND

Disturbed sleep is associated with atherosclerosis in native coronary arteries and may be associated with adverse cardiac events after percutaneous coronary intervention (PCI). We sought to determine the association between symptoms of disturbed sleep and adverse cardiovascular events after PCI.

METHODS

Outpatients who were stable after successful PCI were assessed for symptoms of disturbed sleep with 10 true/false questions. Follow-up was performed at least 4 years after PCI. The primary outcome was a composite of death, myocardial infarction (MI), and repeated revascularization.

RESULTS

Three hundred eighty-eight patients (mean age, 66 ± 11 years) reported on average 3.1 ± 2.1 sleep disturbance symptoms. Follow-up was performed on average 4.4 years after the incident PCI. The primary outcome occurred in 25% of patients. An association was seen between the number of sleep disturbance symptoms and the occurrence of the primary end point. Patients with zero symptoms had a 4-year event rate of 12% compared with a 67% event rate for those with 9 symptoms. On multivariable analysis, sleep symptoms, diabetes mellitus, and the number of diseased coronary vessels were independently associated with the primary end point. Each additional sleep symptom was associated with a hazard ratio (HR) of 1.2 (P = 0.001). The results were driven primarily by the association between symptoms of disturbed sleep and the need for repeated revascularization (repeated PCI HR, 1.9; P = 0.003; coronary artery bypass grafting (CABG) HR, 1.5; P = 0.001).

CONCLUSIONS

Symptoms of disturbed sleep were associated with increased risk of long-term adverse cardiovascular outcomes after successful PCI.

Probucol increases striatal glutathione peroxidase activity and protects against 3-nitropropionic acid-induced pro-oxidative damage in rats

Huntington's disease (HD) is an autosomal dominantly inherited neurodegenerative disease characterized by symptoms attributable to the death of striatal and cortical neurons. The molecular mechanisms mediating neuronal death in HD involve oxidative stress and mitochondrial dysfunction. Administration of 3-nitropropionic acid (3-NP), an irreversible inhibitor of the mitochondrial enzyme succinate dehydrogenase, in rodents has been proposed as a useful experimental model of HD. This study evaluated the effects of probucol, a lipid-lowering agent with anti-inflammatory and antioxidant properties, on the biochemical parameters related to oxidative stress, as well as on the behavioral parameters related to motor function in an in vivo HD model based on 3-NP intoxication in rats. Animals were treated with 3.5 mg/kg of probucol in drinking water daily for 2 months and, subsequently, received 3-NP (25 mg/kg i.p.) once a day for 6 days. At the end of the treatments, 3-NP-treated animals showed a significant decrease in body weight, which corresponded with impairment on motor ability, inhibition of mitochondrial complex II activity and oxidative stress in the striatum. Probucol, which did not rescue complex II inhibition, protected against behavioral and striatal biochemical changes induced by 3-NP, attenuating 3-NP-induced motor impairments and striatal oxidative stress. Importantly, probucol was able to increase activity of glutathione peroxidase (GPx), an enzyme important in mediating the detoxification of peroxides in the central nervous system. The major finding of this study was that probucol protected against 3-NP-induced behavioral and striatal biochemical changes without affecting 3-NP-induced mitochondrial complex II inhibition, indicating that long-term probucol treatment resulted in an increased resistance against neurotoxic events (i.e., increased oxidative damage) secondary to mitochondrial dysfunction. These data appeared to be of great relevance when extrapolated to human neurodegenerative processes involving mitochondrial dysfunction and indicates that GPx is an important molecular target involved in the beneficial effects of probucol.

Oxidative stress and pathological changes after coronary artery interventions

Oxidative stress greatly influences the pathogenesis of various cardiovascular disorders. Coronary interventions, including balloon angioplasty and coronary stent implantation, are associated with increased vascular levels of reactive oxygen species in conjunction with altered endothelial cell and smooth muscle cell function. These alterations potentially lead to restenosis, thrombosis, or endothelial dysfunction in the treated artery. Therefore, the understanding of the pathophysiological role of reactive oxygen species (ROS) generated during or after coronary interventions, or both, is essential to improve the success rate of these procedures. Superoxide O2(·-) anions, whether derived from uncoupled endothelial nitric oxide synthase, nicotinamide adenine dinucleotide phosphate oxidase, xanthine oxidase, or mitochondria, are among the most harmful ROS. O2(·-) can scavenge nitric oxide, modify proteins and nucleotides, and induce proinflammatory signaling, which may lead to greater ROS production. Current innovations in stent technologies, including biodegradable stents, nitric oxide donor-coated stents, and a new generation of drug-eluting stents, therefore address persistent oxidative stress and reduced nitric oxide bioavailability after percutaneous coronary interventions. This review discusses the molecular mechanisms of ROS generation after coronary interventions, the related pathological events-including restenosis, endothelial dysfunction, and stent thrombosis-and possible therapeutic ways forward.

Do statins have a role in reduction/prevention of post-PCI restenosis?

The pathophysiology of post-PCI restenosis involves neointimal formation that consists of three phases: thrombosis (within 24 h), recruitment (3-8 days), and proliferation, which starts on day 8 of PCI. Various factors suggested to be predictors/risks for restenosis include C-reactive protein (CRP), inflammatory mediators (cytokines and adhesion molecules), oxygen radicals, advanced glycation end products (AGEs) and their receptors (RAGE), and soluble RAGE (sRAGE). The earlier noted factors produce thrombogenesis, vascular smooth muscle cell proliferation, and extracellular matrix formation. Statins have pleiotropic effects. Besides lowering serum cholesterol, they have various other biological effects including antiinflammatory, antithrombotic, CRP-lowering, antioxidant, antimitotic, and inhibition of smooth muscle cell proliferation. They inhibit matrix metalloproteinase and cyclooxygenase-2, lower AGEs, decrease expression of RAGE and increase levels of serum sRAGE. They also increase the synthesis of nitric oxide (NO) by increasing endothelial NO synthase expression and activity. Preprocedural statin therapy is known to reduce peri- and post-PCI myonecrosis and reduce the need for repeat revascularization. There is evidence that statin-eluting stents inhibit in-stent restenosis in animal models. It is concluded that because of the above attributes of statins, they are suitable candidates for reduction of post-PCI restenosis and post-PCI myonecrosis. The future directions for the use of statins in reduction of post-PCI restenosis and myonecrosis have been discussed.

Unexpected pro-injury effect of propofol on vascular smooth muscle cells with increased oxidative stress

OBJECTIVES

Propofol is a widely used intravenous anesthetic agent with antioxidant properties. However, the effect of propofol on reactive oxygen species-induced injury in vascular smooth muscle cells is still unknown. In this study, the authors determined the effect of propofol on hydrogen peroxide-induced injury in vascular smooth muscle cells and the potential molecular mechanisms involved.

DESIGN

Prospective cell and animal study.

SETTING

University research laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

For the in vitro study, rat vascular smooth muscle cells pretreated with vehicle or hydrogen peroxide (200 μM) were exposed to vehicle or increasing concentrations of propofol (10-50 μM). For the in vivo study, propofol (12 mg kg⁻¹/hr⁻¹, intravenous) or vehicle was administrated into rats after carotid artery angioplasty.

MEASUREMENTS AND MAIN RESULTS

The cell survival and cell death were measured by MTT and trypan blue exclusion. Cell apoptosis was evaluated by terminal deoxynucleotide transferase dUTP nick end labeling staining and cleaved caspase-3 expression. To further elucidate the molecular mechanisms in propofol-mediated cellular effect, the expression of programmed cell death 4 and microRNA-21 were measured. Unexpectedly, propofol exacerbated hydrogen peroxide-induced injury responses in vascular smooth muscle cells as demonstrated by a decrease in cell viability and an increase in trypan blue-stained cells, cell apoptosis, and cleaved caspase-3 expression. In addition, propofol inhibited hydrogen peroxide-induced up-regulation of microRNA-21 and increased its target gene programmed cell death 4. Propofol-mediated injury was attenuated by restoration of microRNA-21 expression. Finally, the pro-injury effect of propofol on vascular cells with increased reactive oxygen species was illustrated in vivo in rat carotid arteries after angioplasty.

CONCLUSIONS

The results revealed that propofol exacerbates cell injury in vascular smooth muscle cells with increased reactive oxygen species, at least in part, through microRNA-21 and its target gene, programmed cell death 4. Because increased reactive oxygen species is a common pathologic component in many vascular diseases, the novel findings in the current study suggest that propofol might have some application limitations.

Glucose downregulation of PKG-I protein mediates increased thrombospondin1-dependent TGF-{beta} activity in vascular smooth muscle cells

Diabetes is a major predictor of in-stent restenosis, which is associated with fibroproliferative remodeling of the vascular wall due to increased transforming growth factor-beta (TGF-beta) action. It is well established that thrombospondin1 (TSP1) is a major regulator of TGF-beta activation in renal and cardiac complications of diabetes. However, the role of the TSP1-TGF-beta pathway in macrovascular diabetic complications, including restenosis, has not been addressed. In mesangial cells, high glucose concentrations depress protein kinase G (PKG) activity, but not PKG-I protein, thereby downregulating transcriptional repression of TSP1. Previously, we showed that high glucose downregulates PKG-I protein expression by vascular smooth muscle cells (VSMCs) through altered NADPH oxidase signaling. In the present study, we investigated whether high glucose regulation of PKG protein and activity in VSMCs similarly regulates TSP1 expression and downstream TGF-beta activity. These studies showed that high glucose stimulates both TSP1 expression and TGF-beta bioactivity in primary murine aortic smooth muscle cells (VSMCs). TSP1 is responsible for the increased TGF-beta bioactivity under high glucose conditions, because treatment with anti-TSP1 antibody, small interfering RNA-TSP1, or an inhibitory peptide blocked glucose-mediated increases in TGF-beta activity and extracellular matrix protein (fibronectin) expression. Overexpression of constitutively active PKG, but not the PKG-I protein, inhibited glucose-induced TSP1 expression and TGF-beta bioactivity, suggesting that PKG protein expression is insufficient to regulate TSP1 expression. Together, these data establish that glucose-mediated downregulation of PKG levels stimulates TSP1 expression and enhances TGF-beta activity and matrix protein expression, which can contribute to vascular remodeling in diabetes.

Emerging drugs for coronary restenosis: the role of systemic oral agents the in stent era

Introduction of drug eluting stents (DES) during percutaneous coronary interventions significantly reduces the rate of angiographic restenosis, target lesion and vessel revascularization. In spite of these benefits, other clinical hard end points such as death or myocardial infarction were not reduced and, furthermore, new concerns associated with the presence of late and very late stent thrombosis have been raised. The requirement of long-term dual antiplatelet therapy is another limitation associated with DES. Conversely, in this decade, other options to DES have been simultaneously discussed in observational and randomized studies. Several registries and randomized trials using the systemic approach with anti-inflammatory, immunosuppressive or antiplatelet therapies have been identified and discussed in this manuscript. In spite of all randomized studies with oral therapies in the bare metal stent (BMS) era demonstrating positive reductions in coronary restenosis, this practice has not been introduced clinically. Furthermore, a recent randomized trial comparing oral sirolimus plus BMS versus DES demonstrated that the first approach was cost saving and of comparable efficacy to DES. Conclusive evidence of high incidence of late and very late stent thrombosis with DES, together with clinical limitations for its widespread use, has opened up a large opportunity to search for alternative therapies in coronary restenosis prevention.

PGC-1α attenuates neointimal formation via inhibition of vascular smooth muscle cell migration in the injured rat carotid artery

Oxidative stress contributes significantly to the migration of vascular smooth muscle cells (VSMCs), the major pathogenic process of vascular diseases, but the mechanism remains unclear. In the present study, we explored the role of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a major regulator of mitochondrial biogenesis and energy balance, in VSMC migration in vitro and in vivo. Overexpression of PGC-1α in cultured VSMCs led to a 74.5% reduction of migration activity and mitochondrial ROS generation by the increased expression of antioxidative proteins such as SOD-2 in the mitochondria. The knockdown of PGC-1α by specific small interfering (si)RNA markedly augmented VSMC migration activity and greatly reduced mitochondrial antioxidative protein expression. Furthermore, knockdown of SOD-2 expression by siRNA greatly reversed the inhibitory effect of PGC-1α overexpression on VSMC migration. In a rat carotid balloon injury model, adenovirus-mediated overexpression of PGC-1α greatly reduced neointimal formation (ratio of intima to media: 0.78 ± 0.09 vs. 1.45 ± 0.18 in the adenovirus + green fluorescent protein gene- transfected group). Moreover, the expression of SOD-2 was significantly increased in vivo in local vessels after injury in the PGC-1α-overexpressing group. These data strongly suggest that PGC-1α inhibits VSMC migration and neointimal formation after vascular injury in rats, mainly by upregulating the expression of the mitochondrial antioxidant enzyme SOD-2.

Stent‐based tempamine delivery on neointimal formation in a porcine coronary model

BACKGROUND

Tempamine is one of new class of antioxidant agents, the nitroxides, which have shown a wide range of biological effects like suppressing free radical driven reactions to maintain cell functions. The objectives of this study were to evaluate the effect of a biodegradable polymer coated stent loaded with tempamine on in-stent neointimal formation.

METHODS

Stainless steel stents were dip coated in biodegradable elastomeric poly (ester-amide) (co-PEA) or in polymer solution mixed with 50% (wt%) and 100% (wt%) tempamine. One group 100% (wt%) tempamine loaded stents were further dip coated in co-PEA polymer to form a top layer. Stainless steel bare, polymer-only, and different doses tempanine coated stents were implanted into porcine coronary arteries with a stent to artery ratio 1.2:1. Histomorphometric analysis was performed at 5 days and 6 weeks respectively.

RESULTS

Histomorphometric analysis showed that the bare, polymer-only and tempamine-coated stents elicited a similar tissue response at 5 days. At 6 weeks, the peri-strut inflammation and neointimal hyperplasia of polymer-only stents were comparable to the bare stents. Compared to the bare stents, 50% tempanine coated stents had a trend to decrease the arterial injury (0.62 +/- 0.41 versus 0.34 +/- 0.18, P = 0.075) and neointimal hyperplasia (1.80 +/- 0.77 versus 1.27 +/- 0.39 mm2, P = 0.085). However, 100% tempanine coated showed significantly increased inflammatory response and neointimal formation.

CONCLUSION

These co-PEA polymer coatings showed a biocompatible performance. Loaded with 50% tempamine had a trend to decrease neointimal hyperplasia. The 100% tempamine for stent-based delivery may have potential cytotoxic effects to arterial wall. Using a co-PEA polymer topcoat could effectively abolish these side effects.

Involvement of MicroRNAs in hydrogen peroxide-mediated gene regulation and cellular injury response in vascular smooth muscle cells

MicroRNAs (miRNAs) comprise a novel class of endogenous, small, noncoding RNAs that negatively regulate approximately 30% of genes in a cell via degradation or translational inhibition of their target mRNAs. However, the effects of reactive oxygen species (ROS) on miRNA expression and the roles of miRNAs in ROS-mediated gene regulation and biological functions of vascular cells are unclear. Using microarray analysis, we demonstrated that miRNAs are aberrantly expressed in vascular smooth muscle cells (VSMCs) after treatment with hydrogen peroxide (H(2)O(2)). H(2)O(2)-mediated up-regulation of microRNA-21 (miR-21) was further confirmed by quantitative real-time PCR. To determine the potential roles of miRNAs in H(2)O(2)-mediated gene regulation and cellular effects, miR-21 expression was down-regulated by miR-21 inhibitor and up-regulated by pre-miR-21. H(2)O(2)-induced VSMC apoptosis and death were increased by miR-21 inhibitor and decreased by pre-miR-21. Programmed cell death 4(PDCD4) was a direct target of miR-21 that was involved in miR-21-mediated effects on VSMCs. Pre-miR-21-mediated protective effect on VSMC apoptosis and death was blocked via adenovirus-mediated overexpression of PDCD4 without the miR-21 binding site. Moreover, activator protein 1 was a downstream signaling molecule of PDCD4 in miR-21-modulated VSMCs. The results suggest that miRNAs in VSMCs are sensitive to H(2)O(2) stimulation. miRN-21 participates in H(2)O(2)-mediated gene regulation and cellular injury response through PDCD4 and the activator protein 1 pathway. miRNAs might play a role in vascular diseases related to ROS.

A model of cerebrovascular injury in rats

Although the pathophysiology of post-angioplasty restenosis has been extensively studied in extracranial arteries using transluminal vascular injury model in rodents, it is still not well known in the intracranial arteries, which have quite different structures from extracranial arteries. Here, we examined whether 1-min placement of modified intraluminal suture could induce an injury in the internal carotid artery (ICA) in rats and observed temporal profile of histological change after the injury. HE staining showed that the injured intracranial ICA was dilated, while the media was markedly thinned at 1 day after injury. The internal elastic lamina was not observed, and the media contained few cells. At 1 week after injury, a thin layer of neointimal hyperplasia was observed on the luminal side of the internal elastic lamina. Neointimal hyperplasia developed until at least 4 weeks after injury. Morphometric analysis demonstrated that the healing process of the injury was related to arterial remodeling. Immunohistochemical staining for alpha-smooth muscle actin and electron microscopic analysis showed that the neointima was composed of smooth muscle cells. Re-endothelialization was observed from 1 to 4 weeks after injury by immunohistochemical staining for von Willebrand's factor and electron microscopic analysis. Vascular endothelial growth factor was expressed in neointima on days 7 and 14. Interestingly, superoxide anion was not increased in injured arteries on day 3, when the infiltration of macrophages was intensive, but increased on day 7, when infiltrating macrophages almost disappeared. These findings might shed new light on pathophysiology of post-angioplasty restenosis in intracranial arteries.

Novel Gene Silencer Pyrrole-Imidazole Polyamide Targeting Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Attenuates Restenosis of the Artery After Injury

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a membrane protein that can support the binding, internalization, and proteolytic degradation of oxidized low-density lipoprotein. The LOX-1 expression increases in the neointima after balloon injury. To develop an efficient compound to inhibit LOX-1, we designed and synthesized a novel gene silencer pyrrole-imidazole (PI) polyamide targeting the rat LOX-1 gene promoter (PI polyamide to LOX-1) to the activator protein-1 binding site. We examined the effects of PI polyamide to LOX-1 on the LOX-1 promoter activity, the expression of LOX-1 mRNA and protein, and neointimal hyperplasia of the rat carotid artery after balloon injury. PI polyamide to LOX-1 significantly inhibited the rat LOX-1 promoter activity and decreased the expression of LOX-1 mRNA and protein. After balloon injury of the arteries, PI polyamide to LOX-1 was incubated for 10 minutes. Fluorescein isothiocyanate–labeled PI polyamide was distributed to almost all of the nuclei in the injured artery. PI polyamide to LOX-1 (100 μg) significantly inhibited the neointimal thickening by 58%. PI polyamide preserved the re-endothelialization in the injured artery. PI polyamide significantly inhibited the expression of LOX-1, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, and matrix metalloproteinase-9 mRNAs in the injured artery. The synthetic PI polyamide to LOX-1 decreased the expression of LOX-1 and inhibited neointimal hyperplasia after arterial injury. This novel gene silencer PI polyamide to LOX-1 is, therefore, considered to be a feasible agent for the treatment of in-stent restenosis.

Development of a novel endothelial cell-seeded endovascular stent for intracranial aneurysm therapy

The metallic stent has been widely used in endovascular treatment of intracranial aneurysms and arterial stenosis. Endothelialization at the neck of the aneurysm or stenotic lesion after stent deployment plays a pivotal role in preventing aneurysm recurrence, as well as local thrombus formation and restenosis. To deliver autologous endothelial cells and to promote the endothelialization on the luminal wall of the parent artery, we established an endothelial cell-seeded intracranial stent device. Endothelial cells were isolated from canine jugular vein and identified by FACS assay and immunohistochemistry. We demonstrated that the seeded endothelial cells formed a confluent endothelial layer on the stent's surface. After being brushed with 100 dyne/cm(2) of shear stress, we found that this endothelial layer remained intact for at least 48 h on the heparinized polymer coated stent, rather than the poly-lactic-acid coated stent (p < 0.05). The results suggest that an autologous endothelial cell-seeded stent may be a feasible and optimal tool for endothelial delivery during stenting and may overcome some limitations of the traditional bare stent in the treatment of intracranial aneurysms and arterial stenosis.

Antioxidants: the good, the bad and the ugly

Inflammation has a fundamental role in mediating all stages of atherosclerotic disease. The key role of oxidation in linking lipids and inflammation to atherosclerosis is compelling and is supported by experimental evidence. However, the relevance of the antioxidant hypothesis for the treatment of patients with atherosclerosis has not been definitively proven. Results of randomized trials with 'antioxidant' vitamins have been disappointing, and there are potentially important problems associated with their use, including their potential pro-oxidant effects. Probucol has reduced postpercutaneous coronary intervention (PCI)-restenosis and progression of carotid atherosclerosis in clinical trials. The antioxidant vascular protectant AGI-1067 has also been effective at preventing atherosclerosis in all tested animal models. The nonintervened reference coronary segments of the PCI vessel demonstrated improvements with AGI-1067 in the Canadian Antioxidant Restenosis Trial-1 (CART-1), evidence supportive of a clinical effect on slowing atherosclerosis progression. Two trials test the antioxidant/anti-inflammatory hypothesis with AGI-1067; CART-2 assesses its value for the reduction of both atherosclerosis progression and post-PCI restenosis, and Aggressive Reduction of Inflammation Stops Events (ARISE), which is evaluating its effects on hard cardiovascular outcomes.

Pharmacologic approaches to restenosis prevention

Despite significant advances in technology and technique, coronary restenosis remains the primary limitation of percutaneous transluminal coronary angioplasty (PTCA). Among patients undergoing PTCA, between 20% and 50% of patients who do not receive a stent and 10%-30% of those who do receive a stent develop restenosis within 6 months of the procedure. Drug-eluting stents, which release high local concentrations of antiproliferative or immunosuppressive agents directly into the vessel wall at the site of the lesion, have dramatically reduced the incidence of restenosis in patients undergoing PTCA. However, even with drug-eluting stents, a significant percentage of higher-risk patients develop in-stent restenosis. These data suggest that a role remains for effective, well-tolerated systemic pharmacologic therapies to further reduce the rate of restenosis. To date, the majority of systemic agents tested for restenosis prevention have failed to show significant benefit. Only 2 agents, probucol and cilostazol, have consistently demonstrated efficacy in preventing restenosis. In addition, the investigational agent AGI-1067 has demonstrated promising efficacy in early clinical trials. Together with drug-eluting stents, these therapies may for the first time reduce the rate of restenosis to near zero, even in high-risk patients, such as individuals with diabetes mellitus.

Nox1 mediates basic fibroblast growth factor-induced migration of vascular smooth muscle cells

OBJECTIVE

Basic fibroblast growth factor (bFGF) stimulates vascular smooth muscle cell (SMC) migration. We determined whether bFGF increases SMC reactive oxygen-species (ROS) and studied the role of ROS for SMC migration.

METHODS AND RESULTS

bFGF rapidly increased rat SMC ROS formation and migration through pathways sensitive to inhibition of NADPH oxidases, PI3-kinase, protein kinase C, and Rac-1. SiRNA directed against the NADPH oxidase Nox4 impaired basal but not bFGF-induced ROS formation and did not affect migration. In contrast, siRNA against Nox1 blocked the agonist-induced ROS generation as well as the bFGF-induced migration. Agonist-induced migration was also attenuated in SMC derived from Nox1 y/- mice and transduction of Nox1 restored normal migration. Likewise, SMC outgrowth in response to bFGF was attenuated in aortic segments from Nox1 y/- mice as compared with Nox1 y/+ mice. bFGF activated JNK but not Src in a Nox1-dependent manner. Consequently, phosphorylation of the adaptor protein paxillin, which is central for migration and secretion of matrix-metalloproteinases, were dependent on Nox1 as well as JNK but not Src.

CONCLUSIONS

These data demonstrate that bFGF activates the Nox1-containing NADPH oxidase and that bFGF through a pathway involving ROS and JNK stimulates SMC migration.

Probucol up-regulates paraoxonase 1 expression in hepatocytes of hypercholesterolemic rabbits

Paraoxonase 1 (PON1), an HDL-associated enzyme, has anti-oxidative property. Probucol, a hydrophobic antioxidant drug, inhibits progression of atherosclerosis and post-angioplasty restenosis. However, the mechanism by which probucol affects atherosclerosis is not completely understood. Sixteen rabbits fed with high cholesterol diet for 8 weeks were randomly divided into two groups: (1) starch group (n = 8): maintained high cholesterol diet plus starch (500 mg/kg/d) for 6 weeks; (2) probucol group (n = 8): the same cholesterol diet plus probucol (500 mg/kg/d) for 6 weeks. Control group (n = 8) was fed with normal diet for 14 weeks. The classic in-situ two-step perfusion of the liver with collagenase IV was used to isolate the parenchymal hepatocytes. The total activity of superoxide dismutase (SOD) and malondialdehyde (MDA) and PON1 concentrations in serum were measured after 0, 8, and 14 weeks of feeding. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the mRNA expression of PON1. Compared with control group, rabbits fed with high cholesterol diet showed higher levels of serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), all of which were significantly reduced by probucol. Probucol significantly decreased the MDA concentration but was ineffective on SOD activity. High cholesterol diet decreased serum PON1 concentration and down-regulated PON1 mRNA expression in hepatocytes. Probucol significantly increased serum PON1 level and up-regulated the mRNA expression of PON1 as compared with starch group (0.65 +/- 0.06 versus 0.46 +/- 0.05, P = 0.001). The PON1 concentration is negatively associated with MDA concentration (r = -0.86, P = 0.003) but not with the level of HDL-C. In conclusion, probucol decreased MDA concentration, and increased PON1 serum level as well as mRNA expression in hepatocytes, which may help us to understand its antioxidant and anti-atherogenic effects.

Inhibition of injury-induced arterial remodelling and carotid atherosclerosis by recombinant human antibodies against aldehyde-modified apoB-100

OBJECTIVE

The immune system plays an important regulatory role in the development of atherosclerotic plaques and neointima formation following various types of angioplasty. In the present study we investigated the effect of antibodies against aldehyde-modified apolipoprotein B-100 (apoB-100), a component of oxidized LDL, on atherosclerosis and response to arterial injury in mice.

METHODS

The ability of a high affinity human recombinant antibody (2D03), specific for malondialdehyde-modified apoB-100, to influence formation of atherosclerosis as well as remodelling and neointima formation after a collar-induced injury of the carotid artery was studied in LDL receptor(-/-) mice over-expressing human apoB-100.

RESULTS

The antibody recognized epitopes present in mouse plasma and reduced the plasma level of oxidized LDL by 34%. Antibody treatment inhibited injury-induced restrictive vascular remodelling but did not influence the size of the neointima. Atherosclerosis in the uninjured contra lateral carotid artery was determined by computerized image analysis and the mean plaque area in animals given control IgG1 was 7608+/-10,336 micro m(2). In contrast, essentially no plaques were present in animals treated with the 2D03 antibody (397+/-235 micro m(2), P<0.01 versus control IgG1).

CONCLUSIONS

Treatment with antibodies against aldehyde-modified apoB-100 dramatically reduces atherosclerosis and inhibits restrictive vascular remodelling in mice expressing human apoB-100.

Inhibitory effects of epigallocatechin-3-O-gallate on serum-stimulated rat aortic smooth muscle cells via nuclear factor-kappaB down-modulation

The abnormal growth of vascular smooth muscle cells (VSMCs) plays an important role in vascular diseases, including atherosclerosis and restenosis after angioplasty. Although (-)-epigallocatechin-3-O-gallate (EGCG) has antiproliferative effects on various cells, relatively a little is known about precise mechanisms of the inhibitory effects of EGCG on SMCs. In this study, the inhibitory effects of EGCG on attachment, proliferation, migration, and cell cycle of rat aortic SMCs (RASMCs) with serum stimulation were investigated. Also, the involvement of nuclear factor-kappaB (NF-kappaB) during these inhibitions by EGCG was examined. EGCG treatment resulted in significant (p<0.05) inhibition in attachment and proliferation of RASMCs induced by serum. While non-treated RASMCs migrated into denuded area in response to serum and showed essentially complete closure after 36 h, EGCG-treated cells covered only 31% of the area even after 48 h of incubation. Furthermore, EGCG treatment resulted in an appreciable cell cycle arrest at both G0/G1- and G2/M-phases. The immunoblot analysis revealed that the constitutive expression of NF-kappaB/p65 nuclear protein in RASMCs was lowered by EGCG in both the cytosol and the nucleus in a dose-dependent manner. These results suggest that the EGCG-caused inhibitory effects on RASMCs may be mediated through NF-kappaB down-modulation.

Effect of cis-resveratrol on genes involved in nuclear factor kappa B signaling

This study investigated for the first time the effects of the cis isomer of RESV (c-RESV), a polyphenol present in red wine, on an array of genes whose expression is controlled by nuclear factor kappa B (NF-kappaB) and whose transcriptional activation is critical in a number of pathologies (including some cardiovascular diseases). In inflammatory peritoneal macrophages stimulated with lipopolysaccharide (LPS) and gamma interferon (IFN-gamma), c-RESV significantly blocked the expression of genes related to the REL/NF-kappaB/IkappaB family, adhesion molecules and acute-phase proteins; however, the greatest modulatory effect was obtained on the expression of genes related to the pro-inflammatory cytokines. c-RESV down-regulated the nuclear factor of kappa light chain gene enhancer in B-cells 1 (NFkappaBL1) gene product p105 and up-regulated the nuclear factor of kappa light chain gene enhancer in B-cells inhibitor alpha (IkappaBalpha) gene. c-RESV also significantly inhibited intercellular adhesion molecule-1 (ICAM-1) gene expression and the transmembrane receptors RIP (receptor TNFRSF) and TLR3 (toll-like receptor 7). At 100 muM, c-RESV significantly inhibited transcription of Scya2 (chemokine MCP-1), the chemokine RANTES (regulated on activation, normal T cell expressed and secreted), pro-inflammatory cytokines that attract monocyte-granulocyte cells such as M-CSF (colony-stimulating factor 1), GM-CSF (colony-stimulating factor 2) and G-CSF (colony-stimulating factor 3), the cytokine tumor growth factor beta (TGF-beta) and the extracellular ligand IL-1alpha. In contrast, c-RESV stimulated transcription of the pro-inflammatory cytokines IL-6 and tumor necrosis factor alpha (TNF-alpha), the extracellular ligand IL-1beta, and the IFN regulatory factor (IRF)-1. In conclusion, c-RESV has a significant modulatory effect on the NF-kappaB signaling pathway and, consequently, an important antioxidant role that may partially explain the cardioprotective effects attributed to long-term moderate red wine consumption.

Inhibition of choroidal angiogenesis by calcium dobesilate in normal Wistar and diabetic GK rats

Calcium dobesilate reduces vascular endothelial growth factor (VEGF) over-expression in diabetic rat retina, but its effect on intraocular angiogenesis is unknown. Therefore, we tested calcium dobesilate for its in vitro and ex vivo effects on choroidal explant angiogenesis in spontaneously diabetic Goto-Kakizaki (GK) rats. Choroidal explants were cultured in gels of collagen. Budded microvessels numbers and VEGF formation were taken as markers of angiogenesis. Ex vivo studies were performed in GK rats orally given 100 mg/kg/day calcium dobesilate for 10 days. In vitro, calcium dobesilate dose- and time-dependently inhibited both microvessel formation and VEGF production, at concentrations >or=25 mug/ml (i.e. >or=60 microM), with complete inhibition at 100 microg/ml. Oral treatment of diabetic GK rats with calcium dobesilate induced a significant reduction of choroidal angiogenesis ex vivo (38.8% after 3 days of culture). In conclusion, calcium dobesilate inhibited choroidal explant angiogenesis both in vitro and ex vivo. This effect may be due, at least in part, to inhibition of VEGF production. Antiangiogenesis by calcium dobesilate can be involved in its therapeutic benefit in diabetic retinopathy.

Antioxidants and atherosclerosis: Emerging drug therapies

Inflammation has a fundamental role in mediating all stages of atherosclerotic disease. The key role of oxidation in linking lipids and inflammation to atherosclerosis is compelling and supported by experimental evidence. However, the relevance of the antioxidant hypothesis for the treatment of patients with atherosclerosis has not been definitively proven. Probucol has reduced post-percutaneous coronary intervention (PCI) restenosis and progression of carotid atherosclerosis in clinical trials. The antioxidant/vascular protectant AGI-1067 has also been effective at preventing atherosclerosis in all tested animal models. The nonintervened reference coronary segments of the PCI vessel demonstrated improvements with AGI-1067 in the Canadian Antioxidant Restenosis Trial-1 (CART-1), evidence supportive of a clinical effect on slowing atherosclerosis progression. Results of randomized trials with the "antioxidant" vitamins have been disappointing, but there are potentially important problems associated with their use, including their potential pro-oxidant effects. Two important trials that test the antioxidant/anti-inflammatory hypothesis are ongoing with AGI-1067: CART-2, which assesses its value for the reduction of both atherosclerosis progression in non-PCI vessels and post-PCI restenosis; and Aggressive Reduction of Inflammation Stops Events (ARISE), which is evaluating the effects of AGI-1067 on hard cardiovascular outcomes.

Elucidating the Inhibitory Mechanisms of Magnolol on Rat Smooth Muscle Cell Proliferation

The pathological mechanism of percutaneous transluminal coronary angioplasty-induced restenosis has been attributed to outgrowth of vascular smooth muscle cells. Pretreatment with antioxidants has been shown to reduce restenosis. Magnolol, an active compound of Magnolia officinalis, has exhibited approximately 1,000 times more potent antioxidant effects than alpha-tocopherol. In this study, we demonstrate, using cytometric analysis, an approximate 61% reduction of smooth muscle cells progressing to the S-phase by 0.05 mg/ml of magnolol. A BrdU incorporation assay also showed a significant reduction (73%) of DNA synthesis using 0.05 mg/ml of magnolol. The protein level of the proliferating cell nuclear antigen was suppressed by approximately 48% using 0.05 mg/ml of magnolol. This was in agreement with the promoter activity of nuclear factor-kappa B, which was also attenuated by 0.05 mg/ml of magnolol. Since receptor interacting protein and caspase-3 protein expression levels were both increased by magnolol in a dose-dependent manner, the apoptotic pathway may mediate the inhibition of cell growth. Our finding that malondialdehyde formation was significantly inhibited by 0.05 mg/ml of magnolol further supported the antioxidant effect of magnolol. These studies suggest that magnolol might be a potential pharmacological reagent in preventing balloon injury-induced restenosis.

Preclinical restenosis models and drug-eluting stents: still important, still much to learn

Percutaneous coronary intervention continues to revolutionize the treatment of coronary atherosclerosis. Restenosis remains a significant problem but may at last be yielding to technologic advances. The examination of neointimal hyperplasia in injured animal artery models has helped in our understanding of angioplasty and stenting mechanisms, and as drug-eluting stent (DES) technologies have arrived, they too have been advanced through the study of animal models. These models are useful for predicting adverse clinical outcomes in patients with DESs because suboptimal animal model studies typically lead to problematic human trials. Similarly, stent thrombosis in animal models suggests stent thrombogenicity in human patients. Equivocal animal model results at six or nine months occasionally have been mirrored by excellent clinical outcomes in patients. The causes of such disparities are unclear but may result from differing methods, including less injury severity than originally described in the models. Ongoing research into animal models will reconcile apparent differences with clinical trials and advance our understanding of how to apply animal models to clinical stenting in the era of DESs.

Novel antioxidant peptides from fermented mushroom Ganoderma lucidum

Oxidative stress has been linked with the pathogenesis of many human diseases including cancer, aging, and atherosclerosis. The present study investigates the antioxidant activities of peptides isolated from the medicinal mushroom, Ganoderma lucidum. G. lucidum has been shown to possess potent antioxidant activity with little or no side effects. Polysaccharide, polysaccharide-peptide complex, and phenolic components of G. lucidum have been proposed to be responsible for this antioxidant effect. However, research has shown that the G. lucidum peptide (GLP) is the major antioxidant component of G. lucidum. The objective of this study was to evaluate the antioxidant activity of this peptide using different oxidation systems. GLP showed potent antioxidant activities in both lightproof soybean oil and lard systems, assessed by lipid peroxidant value. Compared to butylated hydroxytoluene, GLP showed a higher antioxidant activity in the soybean oil system. Soybean lipoxygenase activity was blocked by GLP in a dose-dependent manner with an IC50 value of 27.1 microg/mL. GLP showed scavenging activity toward hydroxyl radicals produced in a deoxyribose system with an IC50 value of 25 microg/mL, and GLP effectively quenched superoxide radical anion produced by pyrogallol autoxidation in a dose-dependent manner. Malondialdehyde level has been used as the oxidation index in many biological systems. GLP showed substantial antioxidant activity in the rat liver tissue homogenates and mitochondrial membrane peroxidation systems. The auto-hemolysis of rat red blood cells was also blocked by GLP in a dose-dependent manner. On the basis of these results, it is concluded that GLP is the major constituent responsible for the antioxidant activity of G. lucidum. GLP could play an important role in the inhibition of lipid peroxidation in biological systems through its antioxidant, metal chelating, and free radical scavenging activities.

Pharmacologic prevention of both restenosis and atherosclerosis progression: AGI-1067, probucol, statins, folic acid and other therapies

PURPOSE OF REVIEW

In this article, the authors intend to provide an update on clinical trials of pharmacologic prevention of restenosis after percutaneous coronary interventions, placed in the perspective of the use of orally administered therapy for the prevention of atherosclerosis progression and clinical events.

RECENT FINDINGS

AGI-1067, the mono-succinic acid ester of probucol, is a phenolic antioxidant member of a novel class of agents termed v-protectants. It has strong antioxidant properties equipotent to those of probucol and antiinflammatory properties. It inhibits gene expression of VCAM-1 and MCP-1 and has been effective at preventing atherosclerosis in all tested animal models including the non-human primate. In the Canadian Antioxidant Restenosis Trial (CART) 1, AGI-1067 and probucol improved lumen dimensions at the site of percutaneous coronary intervention. AGI-1067 also improved luminal dimensions of non-intervened coronary reference segments in the Canadian Antioxidant Restenosis Trial, which suggests a direct antiatherosclerosis effect. Probucol reduced post-percutaneous coronary intervention restenosis and progression of carotid atherosclerosis in other clinical trials. Although statins reduce atherosclerotic events, they do not appear to have a significant effect on restenosis. The failure of folate therapy to protect against restenosis in the Folate After Coronary Intervention Trial (FACIT) occurred despite significant reductions in homocysteine levels.

SUMMARY

Prevention of both post-percutaneous coronary intervention restenosis and atherosclerosis progression with a pharmacologic agent such as AGI-1067 may be an attractive treatment paradigm. Two important trials that test the antioxidant/antiinflammatory hypothesis are ongoing with AGI-1067: the Canadian Atherosclerosis and Restenosis Trial 2, which assesses its value for the reduction of both atherosclerosis progression and post-percutaneous coronary interventions restenosis, and the Aggressive Reduction of Inflammation Stops Events (ARISE) trial which is evaluating its effects on cardiovascular events.