Increasing levels of dietary homocystine with carotid endarterectomy produced proportionate increases in plasma homocysteine and intimal hyperplasia

PURPOSE: The role that homocysteine may play in post-carotid endarterectomy (CEA) restenosis due to intimal hyperplasia is not well understood. This study was designed to investigate the effects of different levels of dietary homocystine on: (1) plasma homocysteine; (2) post-CEA intimal hyperplasia; and (3) levels of the methyl donor S-adenosylmethionine (SAM) and its counterpart S-adenosylhomocysteine (SAH) in the homocysteine pathway. METHODS: Male rats were fed specialized diets for 2 weeks pre- and post-CEA. Groups included control (0 homocystine added, n=9), 1.5 (1.5 g/kg homocystine added, n=10), 3.0 (3.0 g/kg homocystine added, n=9), and 4.5 (4.5 g/kg homocystine added, n=11). The rats underwent a surgical carotid endarterectomy. Endpoints included; plasma homocysteine, intimal hyperplasia, replicative index using with alpha-SM actin and BrdU, hepatic SAM levels, SAH levels, and the hepatic activities of methylenetetrahydrofolate reductase (MTHFR) and cystathionine beta-synthase (CBS). RESULTS: Increasing dietary homocystine produced a proportionate increase in plasma homocysteine and an increase in intimal hyperplasia. Regression analysis of plasma homocysteine levels and intimal hyperplasia showed a significant correlation (r=0.71,P=0.003). Plasma homocysteine levels above 15 microM were associated with significant increases in intimal hyperplasia above 6.5% (P=0.04). Elevation of plasma homocysteine levels to moderate levels (5-25 microM) resulted in significant post-CEA intimal hyperplasia. Cellular analysis of the area of intimal hyperplasia in all diet groups showed comparable amounts of cells positive for alpha-SM actin. However, with increasing levels of dietary homocystine and plasma homocysteine there was an increase in replicative index (P<0.001) as determined by BrdU staining. Increasing dietary homocystine increased plasma homocysteine and was followed by increases in the replicative index thus producing increased intimal hyperplasia and lumenal stenosis. In hepatic measurements the 1.5 and 3.0 g/kg homocystine diets caused: increased liver activity of MTHFR (P=0.03) and decreased hepatic levels of SAM, SAH and SAM/SAH ratios compared to controls. Homocystine treatment did not cause significant alterations in CBS levels (P=0.992). These studies also showed no correlation of the MTHFR and CBS enzymes with plasma homocysteine levels or intimal hyperplasia. However, hepatic levels of SAM showed significant negative correlations with plasma homocysteine (r=-0.58; P=0.006) and with BrdU percentages of cellular proliferation (r=-0.69; P=0.06). CONCLUSION: The degree of post-CEA intimal hyperplasia in a rat model is directly related to the plasma level of homocysteine. The hyperplastic effects of homocysteine may be mediated in part by a physiological insufficiency of methyl donors as shown by decreases in SAM. Thus, increasing levels of plasma homocysteine enhanced and accelerated the smooth muscle cell response after CEA which led to increased intimal hyperplasia and lumenal stenosis.     

CCR2 deficiency decreases intimal hyperplasia after arterial injury

Monocyte chemoattractant protein (MCP)-1 is upregulated in atherosclerotic plaques and in the media and intima of injured arteries. CC chemokine receptor 2 (CCR2) is the only known functional receptor for MCP-1. Mice deficient in MCP-1 or CCR2 have marked reductions in atherosclerosis. This study examines the effect of CCR2 deficiency in a murine model of femoral arterial injury. Four weeks after injury, arteries from CCR2(-/-) mice showed a 61.4% reduction (P<0.01) in intimal area and a 62% reduction (P<0.05) in intima/media ratio when compared with CCR2(+/+) littermates. The response of CCR2(+/-) mice was not significantly different from that of CCR2(+/+) mice. Five days after injury, the medial proliferation index, determined by bromodeoxyuridine incorporation, was decreased by 59.8% in CCR2(-/-) mice when compared with CCR2(+/+) littermates (P<0.05). Although leukocytes rapidly adhered to the injured arterial surface, there was no significant macrophage infiltration in the arterial wall of either CCR2(-/-) or CCR2(+/+) mice 5 and 28 days after injury. These results demonstrate that CCR2 plays an important role in mediating smooth muscle cell proliferation and intimal hyperplasia in a non-hyperlipidemic model of acute arterial injury. CCR2 may thus be an important target for inhibiting the response to acute arterial injury.     

Relation of a common methylenetetrahydrofolate reductase mutation and plasma homocysteine with intimal hyperplasia after coronary stenting

BACKGROUND: Hyperhomocysteinemia has been identified as an independent risk factor for coronary artery disease. Recent studies have shown that a common mutation (nucleotide 677 C-->T) in the methylenetetrahydrofolate reductase (MTHFR) gene may contribute to mild hyperhomocysteinemia and, therefore, to the incidence of coronary artery disease. No information exists, however, regarding the association between the mutation of the MTHFR gene or plasma homocysteine levels and morphological analysis of coronary atherosclerosis using intravascular ultrasound. METHODS AND RESULTS: To examine the potential influence of MTHFR genotype and homocysteine on coronaryarteries morphologically, we screened 62 patients with 65 lesions that were treated with 93 Palmaz-Schatz stents. The plasma homocysteine levels in the patients with the TT genotype were not significantly higher than those in the patients with non-TT (CC+CT) genotypes (13.1 +/- 5.5 versus 11.5 +/- 3.1 mmol/L, P=0.16). Angiographic analysis showed that the percent diameter stenosis in the patients with the TT genotype was significantly greater than that in those with non-TT genotypes (43.7 +/- 17.8% versus 29.0 +/- 22.0%, P=0.015). Intravascular ultrasound analysis showed that the TT genotype was significantly associated with greater intimal hyperplasia area (5.70 +/- 1.94 versus 3.72 +/- 1.38 mm2, P=0.001). In multiple stepwise regression analysis, the number of the T alleles was the only independent predictor of intimal hyperplasia after intervention (r2=0.21, P=0.004). CONCLUSIONS: The homozygous mutant genotype of the MTHFR gene may increase the risk of in-stent restenosis more than does the normal homozygous or heterozygous genotype.     

Changes in plasma lipid and apoprotein levels in patients with ischemic heart disease after hemosorption]

All the patients who had undergone a course of non-specific hemosorption (HS) for clinical indications showed lower plasma lipid levels and largely lower triglyceride concentrations. The patients with hypercholesterolemia alone simultaneously displayed decreased levels of cholesterol, high density lipoproteins, and apoprotein A-I. Apoprotein B levels reduced in patients having normal lipid values and in those with isolated hypercholesterolemia. The changes in the levels of lipids and apoproteins were different for 2 weeks after hemosorption in relation to the baseline lipid spectrum. The patients with coronary heart disease with hyperlipidemias had positive trends in lipid spectral changes: the parameters of atherogenic classes of lipids tended to decrease, whereas those of antiatherogenic lipid classes tended to show a slight increase. There was a negative direction in the dynamics of the studied parameters in renal patients, in those who had normal baseline lipid values, and in those with isolated hypo-alpha-cholesterolemia, i. e. higher plasma cholesterol and triglyceride, low density lipoprotein cholesterol and apoprotein B levels.     

Plasma apoprotein and lipoprotein lipid levels in vegetarians.

Low-fat, low-cholesterol, high-P:S-ratio diets greatly affect plasma lipid levels. There is no information as to whether such diets affect only lipoprotein levels or also levels of apoproteins and lipoprotein compositions. It is important to have information on the latter to understand diet-induced changes in the metabolism of lipoproteins. Since vegetarians regularly eat an extremely low-cholesterol, low-fat, and-high-P:S ratio diet, they represent an ideal group to study. Fifty-eight vegetarians who eat no animal products and live on a farm commune were examined. Venous bloods were drawn after 12–14 hr fasts and analyzed for lipoprotein-lipids by Lipid Research Clinic procedures and for apoA-I and apoB by radioimmunoassay. Their normal dietary intake was evaluated with 24-hr food diaries. They averaged 2200 kcal/day with 17% protein, 32% fat, and 51% carbohydrate. Negligible amounts of cholesterol (<10 mg/day) was consumed and the P:S ratio was 1.9. Average lipoprotein-cholesterol levels were depressed to about 60% of age- and sex-specific normal levels compared to a group of normolipemic free-living non-vegetarians of a like age and sex distribution. ApoA-I and apoB values were also decreased, but while LDL-cholesterol:apoB ratios did not change, HDL-cholesterol: apoA-I ratios appeared higher in the vegetarians. HDL-cholesterol:LDL-cholesterol ratios of vegetarians were also elevated. The data suggest that the vegetarian diet depressed VLDL and LDL levels without producing major changes in their compositions, whereas both the levels and compositions of HDL were altered. The changes in LDL levels, in HDL-cholesterol:LDL-cholesterol ratios, and in HDL-cholesterol:apoA-I ratios would each place vegetarians in a lower risk category for the development of clinically manifest atherosclerosis.     

Relation of intimal hyperplasia thickness to stent size in paclitaxel-coated stents

To determine the relation of intimal hyperplasia thickness to stent size in nonpolymeric paclitaxel-coated stents, intravascular ultrasound was performed after stent implantation and at 6 months. Similar to bare metal stents, this study demonstrated that intimal hyperplasia thickness is independent of stent size. There was no deleterious effect of the increased concentration associated with using the same stent design in a smaller artery, and these results suggested that stent strut density may be a more important concept than drug concentration.     

Effect of metoprolol on plasma lipids and arterial intimal lipid deposition in spontaneously hypertensive rats

The purpose of the present study was to characterize possible effects of dietary-induced plasma lipid elevations on the development of arterial lesions in spontaneously hypertensive rats (SHR) and to reveal any influence of treatment with metoprolol on these parameters. Metoprolol treatment caused an 8% decrease in heart rate and a 13% decrease in blood pressure and led to a rise in plasma triglycerides, 24%, 17% and 34% after 1, 3 and 6 months of metoprolol treatment, respectively. However, no effect on plasma triglycerides was observed after 9 months of metoprolol treatment while a reduced cholesterolemic response was observed. Intimal proliferations containing accumulations of lipids were observed in small intramural branches of coronary arteries (greater than 100 microns) in 11 of 31 control rats fed the atherogenic diet for 9 months. In contrast, similar changes were observed in only 1 of 34 metoprolol-treated rats fed an otherwise identical diet. The corresponding figures for the frequency of lipid containing intimal plaques in aorta were 6/19 in controls and 2/24 in the metoprolol-treated group.     

卡托普利对动脉损伤后内膜增生时纤溶系统的影响

目的　通过兔颈总动脉球囊损伤模型 ,观察卡托普利 (开搏通 ,captopril)对动脉球囊损伤后内膜增生时纤溶系统的影响。方法　以兔右颈总动脉内膜剥脱为实验模型 ,36只兔随机分为假手术组 (对照组 )、单纯损伤组、损伤 +药物治疗组 (简称药物治疗组 ) ,每组各 12只。药物治疗组术前1d至术后 30d给予captopril2mg·kg 1 ·d 1 ,余二组不给药 ,用ELISA法检测各组术前、术后 1、3、7、14、30d的血浆组织纤溶酶原激活剂 (t PA)、纤溶酶原激活剂抑制物 1(PAI 1)的水平 ,并于术后 30d行病理形态学观察各组血管内膜厚度及管腔狭窄度。结果　动脉球囊损伤后 ,药物治疗组PAI 1水平、内膜的厚度及管腔狭窄度均明显低于单纯损伤组。结论　血管球囊损伤术后纤溶系统作用的减弱影响动脉壁损伤再修复过程 ,captopril可使纤溶系统保持平衡 ,预防血管成形术后再狭窄。     

Preintervention arterial remodeling as a predictor of intimal hyperplasia after intracoronary stenting: a serial intravascular ultrasound study.

BACKGROUND: The impact of vascular remodeling pattern on intimal hyperplasia (IH) after coronary stenting is unknown. HYPOTHESIS: The preintervention remodeling pattern of the lesion might be associated with IH after the coronary stenting procedure. METHODS: Serial (pre-, post-stent implantation, and follow-up) intravascular ultrasound (IVUS) images were obtained in 58 patients with single-stent implantation (GFX stents in 41 and NIR in 17). The matching IVUS image slices at the preintervention lesion site were selected for serial comparisons. The remodeling index (RI) was defined as lesion/proximal reference external elastic membrane cross-sectional area (CSA) at preintervention lesion site. Adequate remodeling was defined as a RI > 0.95 and inadequate remodeling as a RI < or = 0.95. Vessel stretching, percent vessel stretching, and percent IH CSA, as well as pre- and postintervention IVUS variables were evaluated according to the remodeling pattern. RESULTS: The percent IH CSA was 31% in adequate remodeling (n = 29, mean RI = 1.05) and 41% in inadequate remodeling (n = 29, mean RI = 0.88) (p = 0.049). Percent vessel stretching was 15% in adequate remodeling and 22% in inadequate remodeling (p = 0.007). The RI inversely correlated with percent vessel stretching (r = -0.435, p = 0.001). CONCLUSIONS: Compared with preintervention adequate remodeling, inadequate remodeling was associated with increased percent IH CSA, which might be related with more vessel stretching.     

不同支架置入术后猪冠状动脉内膜增生与血管损伤程度的关系

目的:制作猪冠状动脉支架置入术模型,对行不同类型支架留置术后内膜的增生与血管损伤情况进行研究。方法:把Co il支架及T ubu lar支架分别置入9头猪共36支冠脉血管内,使用血管内超声(IVU S),免疫组织学等方法观察以下项目,(1)第28 d时的内膜肥厚面积;(2)支架对血管壁的损伤程度。结果:(1)用IVU S评价支架置入第28 d时的支架面积,血管内腔面积:T ubu lar支架的明显高于Co il支架的,[分别为(7.74±0.42)mm2∶(6.75±0.56)mm2,P<0.001);(5.27±0.53)mm2∶(4.02±0.76)mm2,P<0.001];(2)用免疫组织学的方法分析支架对血管壁的损伤程度:T ubu lar支架小于Co il支架的[(1.69±0.32)mm2∶(2.00±0.40)mm2,P<0.05];(3)两组支架的损伤程度与内膜肥厚的长度呈良好的正相关(r2分别为0.8198,0.8749)。结论:支架术后再狭窄与血管损伤及冠状动脉内膜增生的厚度有关,减少血管损伤是预防再狭窄的关键之一。     

Restenosis after coronary angioplasty. Potential biologic determinants and role of intimal hyperplasia

Restenosis after successful PTCA remains a major problem limiting the efficacy of the procedure. The pathophysiologic mechanism of restenosis has been enigmatic so far, but accumulated evidence strongly suggests that intimal hyperplasia is the major mechanism. Based on current understanding of the process of intimal hyperplasia, one unifying concept may be that there are at least two major local biologic determinants influencing this process, lesion characteristics and regional flow dynamics. Lesion characteristics include the plaque structure and the quantity of smooth muscle. These may provide the anatomic substrate that determines the extent of injury and the degree of smooth muscle cell proliferation. The amount of smooth muscle cells in the stenotic lesion activated by injury to undergo proliferation may determine the eventual bulk of the restenotic lesion. In addition, low wall shear stress could promote intimal hyperplasia and cause structural change of vessels to decrease the lumen, whereas high wall shear stress exerts the opposite effects. Intimal hyperplasia after balloon injury is a complex process involving platelets, growth factors, endothelial cells, smooth muscle cells, mechanical injury, wall shear stress, and probably other unknown factors. Platelets not only contribute growth factors such as PDGF but also cause organized thrombus. Different growth factors may be involved in initiating smooth muscle cell proliferation and may come from many different sources, including smooth muscle cells, endothelial cells, and macrophages. Intact confluent endothelial cells may produce heparin sulfates and inhibit intimal proliferation; however, regenerating endothelial cells may have the opposite effect. Thus, the proliferative potential of smooth muscle cells, endothelial recovery, extent of injury, wall shear stress, and other unknown factors may all influence this process. Based on these concepts concerning the biology of restenosis, some research directions concerning potential forms of therapy are proposed.     

Relation of time course of plasma nitroglycerin levels to echocardiographic, arterial pressure and heart rate changes after sublingual administration of nitroglycerin

Despite the widespread use of nitroglycerin, a relation between plasma nitroglycerin concentrations and the associated cardiovascular effects has not been well established. It was hypothesized that nitroglycerin levels may help predict the hemodynamic responses. With use of a recently developed nitroglycerin assay technique, the relation between the time course of plasma nitroglycerin levels and echocardiographic changes after sublingual administration of 0.6 mg of the drug was evaluated in 12 normal volunteers. Mean plasma nitroglycerin levels were maximal at 2 (1.1 +/- 0.3 ng/ml) and 5 (1.4 +/- 0.6 ng/ml) minutes, when the changes in mean heart rate (+17 +/- 7 and +12 +/- 3 min-1) and decreases in echocardiographic left ventricular diastolic (-4.2 +/- 0.8 mm at 5 minutes) and systolic (-3.1 +/- 0.6 mm at 5 minutes) dimensions were also maximal. Parallel changes were noted in left atrial dimension, ventricular velocity of circumferential fiber shortening and systolic blood pressure, but not in diastolic blood pressure. These findings demonstrate the existence of a close relation between plasma nitroglycerin levels and variables that reflect the known responses to this drug.     

Efficacy and safety of oral sirolimus to inhibit in-stent intimal hyperplasia.

Sirolimus systemic administration has shown marked inhibition of neointimal hyperplasia (NIH) after balloon angioplasty in porcine models. In this pilot study, we tested the hypothesis that oral sirolimus is safe and effective to inhibit in-stent NIH and therefore to prevent and treat in-stent restenosis (ISR). Twelve patients (18 lesions) with high risk for ISR, including 8 ISR lesions, were admitted. One day before the procedure, patients were given a 15 mg loading dose of oral sirolimus, followed by 5 mg daily for 28 days, with weekly whole blood level measurements. The daily dose was adjusted to keep the concentration at 10-15 ng/ml. Sirolimus was well tolerated by all patients but one, who died at the end of the third week of treatment. The 4- and 8-month follow-up revealed an angiographic late loss of 0.40 +/- 0.24 and 0.67 +/- 0.45 mm (P < 0.01), respectively. At the same time points, the intravascular ultrasound in in-stent relative volumetric obstruction was 14.4% +/- 9.1% and 23.2% +/- 10.1% (P < 0.01), respectively. At 24-month clinical follow-up, adverse events were one (8.3%) death, two (11.1%) target lesion, and four (22.2%) target vessel revascularizations. In conclusion, in this small group of high-risk ISR patients, oral sirolimus inhibited NIH and therefore may be an effective strategy for the prevention and treatment of ISR.     

Serum monocyte chemoattractant protein-1 levels in rat models of intimal hyperplasia

Recently we reported that there is a direct correlation between monocytes/macrophages (Mo/Mø) infiltration and the development of intimal hyperplasia (IH) in rat interposition vein graft. Monocyte chemoattractant protein-1 (MCP-1) is the most potent chemoattractant and activating chemokine for Mo/Mø. We evaluated rat serum MCP-1 levels as the indicator of inflammatory response, before and after operation. In twenty five male Lewis rats (484±7 g) we interposed epigastric vein graft into the right common femoral artery. Rat serum MCP-1 levels were measured before skin incision and before and after bypass (0 hour, two weeks and four weeks), using enzyme linked-immuno-sorbent assay method. Rat serum MCP-1 levels were significantly increased at 0 hour (154 pg/ml,p<0.05), two weeks (187 pg/ml,p<0.01) and four weeks (169 ng/ml,p<0.01), compared to before skin incision (87 pg/ml). These results suggest that the prolongation of inflammatory response may cause the development of IH in rat interposition vein grafts.     

Arterial remodeling influences the development of intimal hyperplasia after stent implantation

OBJECTIVES: We examined whether preinterventional arterial remodeling influenced the interventional results after stenting. BACKGROUND: Arterial remodeling is seen in atherosclerotic lesions, and it may play an important role in the early stage of atherosclerosis. METHODS: We examined 113 lesions that underwent elective stenting using tubular slotted stents under intravascular ultrasound guidance. The lesions were divided into three groups--adequate, intermediate and inadequate remodeling group--according to preinterventional arterial remodeling. The patients were subjected to coronary angiography and intravascular ultrasound evaluation on average 6.4 months after stenting. RESULTS: At baseline and immediately after stenting, there were no differences in quantitative angiographic analysis among remodeling groups. However, the plaque cross-sectional area (CSA) in the minimal lumen CSA at preintervention and intimal hyperplasia CSA at follow-up were significantly larger in the adequate remodeling group than in the inadequate remodeling group. The restenosis rate of stenting for the lesions with inadequate arterial remodeling was very low (9.4%). A significant positive correlation was found between preinterventional plaque CSA and intimal hyperplasia CSA at follow-up (r = 0.47, p < 0.0001). Moreover, remodeling index significantly correlated with relative intimal hyperplasia CSA (r = 0.28, p < 0.01). CONCLUSIONS: Preinterventional arterial remodeling influenced the development of intimal hyperplasia after stenting.     

Thrombogenicity and intimal hyperplasia after conventional and thermal balloon dilation in normal rabbit iliac arteries.

Acute occlusion and restenosis are the major complications of percutaneous transluminal coronary balloon angioplasty. Application of heat during balloon dilation was postulated to reduce these complications. We evaluated thrombogenicity and intimal hyperplasia of normal rabbit iliac arteries after conventional (37 degrees C) and thermal balloon dilation. Thermal dilation was performed with a radio-frequency-heated balloon, provided with three thermocouples attached to the inside of the balloon skin. In a previous in vitro study, thrombogenicity of human subendothelium was increased at 55 degrees C and greatly decreased at temperatures over 70 degrees C. Thermal balloon dilation was therefore performed at 55 and 90 degrees C in vivo. Rabbits survived 2 h for evaluation of platelet adhesion or either 3 or 8 weeks for intimal hyperplasia. Angiograms revealed no occlusions or thrombi after any procedure. Platelet adhesion was quantified on 20 scanning electron microscopic pictures per balloon dilation site and was expressed as the percentage of the luminal surface covered by platelets. Platelet adhesion was similar in all groups, although large thrombi were present in the 90 degrees C group. Intimal hyperplasia was measured morphometrically at regular intervals over the balloon site. After 3 weeks, the average intimal hyperplasia was significantly reduced in the 90 degrees C balloon dilation group, which was mainly due to the absence of intimal hyperplasia in the midpart of these segments. After 8 weeks, intimal hyperplasia was equal in all groups. Thus, in the applied model, platelet coverage was equal after conventional balloon angioplasty and after 55 and 90 degrees C balloon angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)