Aggressive lipid lowering in postcoronary angioplasty patients with elevated cholesterol (the Lovastatin Restenosis Trial)

A promising carbon-11-labeled sphingosine-1-phosphate receptor 1-specific PET tracer for imaging vascular injury

BACKGROUND

Sphingosine-1-phosphate receptor 1 (S1PR1) is highly expressed in vascular smooth muscle cells from intimal lesions. PET imaging using S1PR1 as a biomarker would increase our understanding of its role in vascular pathologies including in-stent restenosis.

METHODS

The S1PR1 compound TZ3321 was synthesized for in vitro characterization and labeled with Carbon-11 for in vivo studies. The biodistribution of [11C]TZ3321 was evaluated in normal mice; microPET and immunohistochemistry (IHC) studies were performed using a murine femoral artery wire-injury model of restenosis.

RESULTS

The high potency of TZ3321 for S1PR1 (IC 50 = 2.13 ± 1.63 nM), and high selectivity (>1000 nM) for S1PR1 over S1PR2 and S1PR3 were confirmed. Biodistribution data revealed prolonged retention of [11C]TZ3321 in S1PR1-enriched tissues. MicroPET imaging of [11C]TZ3321 showed higher uptake in the wire-injured arteries of ApoE-/- mice than in injured arteries of wild-type mice (SUV 0.40 ± 0.06 vs 0.28 ± 0.04, n = 6, P < .001); FDG-PET showed no difference (SUV 0.98 ± 0.04 vs 0.94 ± 0.01, n = 6, P > .05). Post-PET autoradiography showed >4-fold higher [11C]TZ3321 retention in the injured artery of ApoE-/- mice than in wild-type mice. Subsequent IHC staining confirmed higher expression of S1PR1 in the neointima of the injured artery of ApoE-/- mice than in wild-type mice.

CONCLUSIONS

This preliminary study supports the potential use of PET for quantification of the S1PR1 expression as a biomarker of neointimal hyperplasia.

Short-term rapamycin for inhibition of neointima formation after balloon-mediated aortic injury in rats: is there a window of opportunity for systemic prophylaxis of restenosis?

PURPOSE

To evaluate the efficacy of limited short-term systemic administration of rapamycin to prevent neointimal intimal hyperplasia (NIH) in a double-injury rat model of restenosis.

METHODS

Aortic lesions were induced by perivascular placement of silicone cuffs around the aorta of 36 Lewis rats. After 3 weeks, the cuffs were removed, and the vessels were subjected to secondary balloon injury. Rapamycin (sirolimus) was intravenously administered for 5 days in dosages of 0.5 or 2 mg/kg/d beginning at various time points relative to the balloon injury: (1) days -2 to +2, (2) days 1 to 5, or (3) days 7 to 11. For each treatment period, 6 rats received the 5-day course of the lower or higher dose of rapamycin. Eight rats served as controls undergoing 2-stage injury without rapamycin treatment. Morphometry and immunohistochemistry were performed at 21 days after angioplasty.

RESULTS

NIH and intimal alpha-actin expression were inhibited by both dosages when treatment started 2 days before or 1 day after angioplasty. Results were statistically significant for the lower dose when started 1 day after angioplasty (p < 0.01) and for the higher dose when initiated 2 days before the intervention (p < 0.05). Treatment commencing at 7 days did not reduce NIH in either dosage group.

CONCLUSIONS

In a double-injury rat model, NIH can be inhibited by short-term systemic rapamycin, but suppression of early cell migration and proliferation is pivotal. A limited peri-interventional antiproliferative therapy may be of value as an adjunct to control restenosis after balloon angioplasty and/or stenting.

Neointimal formation after endovascular arterial injury is markedly attenuated in db/db mice

OBJECTIVE

A diabetic mouse model of accelerated neointimal formation would be a useful tool to understand the increased incidence of restenosis in patients with diabetes.

METHODS AND RESULTS

Femoral artery endoluminal wire injury was performed in diabetic insulin 2 Akita (ins2Akita) and leptin receptor db/db (leprdb/db) mutant mice. Neointima size in ins2Akita mouse arteries was unchanged compared with nondiabetic wild-type littermates. Although Ki67 labeling demonstrated similar rates of replication in the neointima of leprdb/db mouse arteries, neointimal formation in leprdb/db mice was surprisingly reduced by approximately 90% compared with nondiabetic lepr+/+ mice. Four hours after arterial injury, medial smooth muscle cell death was diminished in leprdb/db arteries, suggesting that the initial response to arterial injury was altered in leprdb/db mice.

CONCLUSIONS

These studies highlight a differential response to arterial injury in leprdb/db mice and suggest a potential role for leptin in the regulation of neointimal formation in response to arterial injury.

Oral everolimus inhibits in-stent neointimal growth

BACKGROUND

Rapamycin (sirolimus)-eluting stents are associated with reduced restenosis rates in animal studies and initial human trials. The present study evaluated whether orally administered everolimus (a macrolide of the same family as sirolimus) inhibits in-stent neointimal growth in rabbit iliac arteries.

METHODS AND RESULTS

New Zealand white rabbits were randomized to everolimus 1.5 mg/kg per day starting 3 days before stenting and reduced to 1 mg/kg per day from days 14 to 28 (group 1), everolimus 1.5 mg/kg given 1 day before stenting followed by 0.75 mg/kg per day for 28 days (group 2), or matching placebo for each group. Drugs were administered by oral gavage. Stents were deployed in both iliac arteries, and arteries were harvested 28 days after stenting. Group 1 everolimus-treated rabbits experienced weight loss and anorexia, which resolved after the everolimus dose was lowered on day 14. Group 2 animals were healthy for the duration of everolimus dosing. Both everolimus treatment groups significantly reduced in-stent neointimal growth (46% reduction and 42% reduction in intimal thickness in groups 1 and 2, respectively). In group 2 everolimus-treated animals, the neointima was healed or healing, characterized by stent struts covered by a thin neointima, overlying endothelial cells, and only small foci of fibrin. Scanning electron microscopy showed >80% stent surface endothelialization in group 2 everolimus-treated rabbits.

CONCLUSIONS

Oral everolimus suppresses in-stent neointimal growth in the rabbit iliac artery. At a dose of 1.5 mg/kg given 1 day before stenting followed by 0.75 mg/kg per day for 28 days, everolimus was well tolerated and was associated with significant neointimal healing.

Greater pathogen burden but not elevated C-reactive protein increases the risk of clinical restenosis after percutaneous coronary intervention

BACKGROUND

Restenosis after percutaneous coronary intervention (PCI) constitutes a serious complication in the treatment of cardiovascular disease, but known risk factors do not fully account for the observed restenosis risk. Preliminary studies of infection or inflammation in restenosis report varied results. We tested whether C-reactive protein (CRP) or pathogen burden (seropositivity to 0, 1, 2, or 3 pathogens, of Chlamydia pneumoniae [Cpn], cytomegalovirus [CMV], or Helicobacter pylori [Hpy]) predict clinical restenosis after percutaneous coronary intervention (PCI).

METHODS

Blood samples were collected from 415 patients undergoing PCI, and levels of plasma CRP and antibodies to Cpn, CMV, and Hpy were measured. The patient's medical history, demographics, and procedural data were recorded. Patient end points were determined for as long as 6 months as a means of evaluating the incidence of clinical restenosis and major adverse cardiac events.

RESULTS

The average patient age was 62 years, and 80% of patients were male. Fifty-eight patients (14%) experienced clinical restenosis, whereas 17 patients (4%) died or had an acute myocardial infarction. After adjusting for 19 possible predictors, we found the pathogen burden (P-trend =.04, adjusted odds ratio [OR] 1.5 per number of pathogens) and minimum luminal diameter (P =.003, OR 1.8 per mm decrease) to be significant predictors of clinical restenosis. Male sex was a nonsignificant predictor of restenosis (P =.06, OR 2.2), but CRP was not significant after adjustment (P-trend =.10, OR 0.73 per tertile).

CONCLUSION

Pathogen burden was associated with clinical coronary restenosis, an association that deserves further exploration and evaluation. CRP, a marker of inflammation, was not associated with an increased risk of restenosis.

Lowering of dietary advanced glycation endproducts (AGE) reduces neointimal formation after arterial injury in genetically hypercholesterolemic mice

Restenosis remains a major cause of morbidity and mortality after coronary angioplasty. Injury-induced inflammation, thrombosis, smooth muscle cell (SMC) proliferation, and neointimal formation contribute to restenosis. These events are linked to circulating glucose-derived advanced gycation endproducts (AGE), known to promote cell proliferation, lipid glycoxidation and oxidant stress. This study evaluates the association between dietary AGE content and neointimal formation after arterial injury in genetically hypercholesterolemic mice. Male, 12-week-old, apolipoprotein E-deficient (apoE(-/-)) mice were randomly assigned to receive either a high AGE diet (HAD; AGE=15000 U/mg), or a similar diet with ten-fold lower AGE (LAD; AGE=1500 U/mg). These mice underwent femoral artery injury 1 week later, and were maintained on their diets for an additional 4 weeks. At 4 weeks after injury, significant decrease in neointimal formation was noted in LAD-fed mice. Neointimal area, intima/media ratio, and stenotic luminal area (LA) were less pronounced in the LAD group than the HAD group (P<0.05). These quantitative differences were associated with a marked reduction ( approximately 56%) of macrophages in the neointimal lesions, as well as an obvious reduction of SMC content of LAD-fed mice. The reduction of neointimal formation in the LAD mice correlated with a approximately 40% decrease in circulating AGE levels (P<0.0005). Immunohistochemistry also showed a reduced ( approximately 1.5-fold) deposition of AGE in the endothelia, SMC, and macrophages in neointimal lesions of LAD-fed mice. These results represent the first evidence in vivo for a causal relationship between dietary AGE and the vessel wall response to acute injury, suggesting a significant potential for dietary AGE restriction in the prevention of restenosis after angioplasty.

Sulindac inhibits neointimal formation after arterial injury in wild-type and apolipoprotein E-deficient mice

Neointimal hyperplasia is a critical component of restenosis, a major complication of angioplasty and related therapeutic procedures. We studied the effects of hyperlipidemia and the nonsteroidal anti-inflammatory drugs, aspirin (acetyl-salicylic acid; ASA), and sulindac, on neointimal formation in a mouse femoral arterial injury model. At 2 months of age, normolipidemic, wild-type (WT), and hyperlipidemic, apolipoprotein E-deficient (apoE-/-) mice were divided into three treatment groups: Western-type diet (WD), WD + ASA (200 mg/kg food), and WD + sulindac (300 mg/kg food). After 1 week, mice underwent arterial injury and treatments were maintained for 4 weeks. Histomorphometry of the injured arteries showed striking effects of plasma cholesterol levels and drug treatment on neointimal hyperplasia. In the WD or WD + ASA groups, apoE-/- mice had twice the neointimal area than WT mice ( approximately 30,000 vs. 13,000 microm(2) per section; P < 0.0001). Compared with ASA or WD alone, sulindac treatment resulted in approximately 70% (P = 0.0001) and 50% (P = 0.01) reductions in the neointimal area in apoE-/- and WT mice, respectively. ASA, at a dose sufficient to inhibit platelet aggregation, did not affect neointimal formation in mice of either genotype. Evidence of macrophages was noted in the lesions of apoE-/- mice in the WD and WD + ASA groups, but remarkably, none was detectable with sulindac treatment, despite hyperlipidemia, suggesting early steps in the response to injury were abrogated. These results demonstrate sulindac reduces neointimal formation in both normolipidemic and hyperlipidemic settings and raise the possibility that similar benefits may be obtained in patients undergoing angioplasty and related procedures.

Interventional Cardiology: Advances in Percutaneous Techniques for the Treatment of Cardiac Disease

The field of interventional cardiology began in the late 1970s and consisted primarily of balloon catheter angio plasty until the early 1990s. Although understanding of the process of coronary angioplasty has evolved signifi cantly, restenosis still remains the Achilles' heel of the interventional cardiologist. This article reviews the cur rent issues involved in interventional cardiology for coronary disease from patient selection, anticoagulant therapy, restenosis, current interventional devices (stent mania), and future devices (intracoronary radiation). Noncoronary interventional procedures, vaivuloplasty, and atrial septal defect closure are also reviewed to provide an overview of cardiac interventional proce dures for the anesthesiologist.