Effects of dipyridamole in experimental atherosclerosis. Action on PGI2, platelet aggregation and atherosclerotic plaque formation.

Experimental atherosclerosis in rabbits induced by feeding a standard atherogenic diet for 4 months resulted in an increased sensitivity of platelets to the proaggregatory action of collagen and ADP. Treatment with dipyridamole (3 x 10 mg/day i.m.) for 4 weeks normalized platelet loss in atherosclerotic rabbits and abolished the increased sensitivity to proaggregatory collagen, but not to ADP. Dipyridamole treatment lowered basal as well as PGI2-induced cAMP levels below values seen in platelets from normal rabbits, but the stimulation by PGI2 relative to basal cAMP levels was not affected or even increased by dipyridamole treatment. Dipyridamole did not affect the increased sensitivity of platelets from atherosclerotic rabbits to the antiaggregatory action of PGI2, indicating that dipyridamole decreased absolute cAMP levels, probably due to reduction of the adenine nucleotide pool in platelets without affecting the adenylate cyclase function. Dipyridamole enhanced atherosclerotic plaque formation in arterial walls. Basal as well as PGI2-stimulated cAMP content was lower in homogenates from atherosclerotic than from normal aortic tissue. Dipyridamole-treated animals showed a further decrease in basal as well as PGI2-stimulated cAMP content of the aortic tissue, suggesting that this decrease in cAMP content may be linked to the enhanced proliferative activity seen in artherosclerotic plaque formation.     

Animal models of spontaneous plaque rupture: The holy grail of experimental atherosclerosis research

Throughout the history of atherosclerosis research we have sought animal models of the disease process that exhibit high frequencies of the features that make human plaque a clinical risk: plaque rupture, mural thrombosis, and intra-plaque hemorrhage. This type of model is needed to determine the mechanisms by which plaques rupture and to design and test therapeutic interventions for stabilizing plaques. Studies of domestic and exotic animals have shown that most species will spontaneously develop fatty streaks and in some cases atheromatous lesions with sufficient time, but that rupture and thrombosis is exceedingly rare. Even with addition of fat and cholesterol to the diet, lesion development is accelerated but does not increase the frequency with which plaques rupture in most animal models. However, recently we have observed high frequencies of intra-plaque hemorrhage in the innominate/brachiocephalic arteries of older, chow-fed, hyperlipidemic, apolipoprotein E-deficient mice, and high frequencies of plaque rupture with mural thrombus in younger apolipoprotein E-deficient mice fed a high-fat diet. This suggests that plaque rupture and secondary thrombosis are frequent and reproducible occurrences at specific sites in apolipoprotein E-deficient mice, and that the timing and pathobiology of the ruptures are influenced by lipid status in this murine model.     

Pathobiology of atherosclerosis and plaque complications

To understand the process of atherosclerosis, the homeostatic and protective functions of the endothelium must be considered. The endothelium serves as the interface between blood flow and the vascular tissues. It normally regulates vascular tone and structure through the release of vasoactive substances and maintenance of a nonthrombogenic surface. Endothelial dysfunction, which results from biochemical and hemodynamic stresses associated with cardiovascular risk factors, causes an imbalance in the expression of vasodilating and vasoconstricting substances, as well as excess production of chemoattractant molecules and growth factors. Endothelial dysfunction in the presence of elevated cholesterol levels fosters the development of fatty streaks, which represent the early stage of atherosclerotic plaque. The unstable progression of atherosclerosis can be interrupted and even reversed in both animals and humans, although the exact clinical correlates of progression and regression are not fully understood.     

The mechanism of transluminal angioplasty: evidence for formation of aneurysms in experimental atherosclerosis

Quantitative histologic examination (morphometric analysis) of pressure-perfused rabbit atherosclerotic arteries was used to determine whether compression of atheromatous material occurs with transluminal angioplasty. Experimental atherosclerosis was developed in both iliac arteries, with transluminal angioplasty performed on the left iliac while the right iliac served as a nondilated control. Angiography showed equal degrees of luminal narrowing before angioplasty (p = NS). Angioplasty reduced the left iliac narrowing in all animals studied. Morphometric analysis of histologic sections of the left and right iliac arteries disclosed significant differences in luminal and total vessel areas (p less than .05), whereas arterial wall (intima and media) areas were similar (p = NS). Dilated areas often demonstrated marked intimal splitting with dissection into the media. At higher magnification, loss of nuclear staining and dense layers of extracellular matrix consistent with stretching were frequently seen. It is concluded that the major mechanism of successful transluminal angioplasty is stretching of the vessel, resulting in localized aneurysm formation. Intimal splitting implies inelasticity of the neointima. No evidence of compression and remodeling of atheromatous material was disclosed in this study.     

基质金属蛋白酶-9对大鼠动脉粥样硬化斑块内血管生成及斑块稳定性的影响

目的:研究基质金属蛋白酶-9（MMP-9）与动脉粥样硬化(AS)斑块内血管生成的关系及强力霉素干预的效果。方法: 将36只雄性Wistar大鼠随机分为对照组（A组,普通饮食喂养）、AS组（B组）和强力霉素干预组（C组）,B组和C组均给予高脂饮食＋维生素D3腹腔注射,C组同时给予强力霉素腹腔注射。采用酶法并以全自动生化分析仪测量血脂,双抗体夹心ABC-ELISA法检测血清MMP-9的水平。取主动脉切片行HE染色,观察斑块形态,计数易损斑块的数目。对内皮细胞标记物CD34行免疫组织化学染色法以检测斑块内新生血管密度。结果: B组和C组各项血脂的水平无明显差异,但均明显高于A组（P<0.05）。B组和C组血清MMP-9的水平明显高于A组（P<0.05）,B组又高于C组（P<0.05）。与B组比较,C组易损斑块数、CD34+面积/扫描面积(R)比均降低(P<0.01)。结论: 强力霉素能增强斑块稳定性,这种作用可能是通过降低MMP-9的水平进而减少了斑块内血管生成。     

一种大鼠动脉粥样硬化斑块模型的建立

目的试建立一种大鼠动脉粥样硬化斑块模型。方法给予大鼠一次维生素D33×105U/kg体重肌肉注射、球囊损伤主动脉内皮和饲以含2％胆固醇、0.5％胆酸钠、0.2％丙硫氧嘧啶、3％猪油和维生素D31.25×106U/kg的高脂饲料90 d。结果90 d后大鼠血脂明显增高,胸主动脉形成明显的动脉粥样硬化斑块,斑块内有大量的泡沫细胞、脂质、巨噬细胞及钙化,中膜平滑肌明显萎缩;而仅饲以高脂饲料的大鼠胸主动脉结构未见改变。结论血管钙超载、内皮损伤和高脂可使大鼠主动脉形成较典型的动脉粥样硬化斑块。     

Increased subclinical atherosclerosis in patients with chronic plaque psoriasis

Background: Psoriasis is an immune-mediated inflammatory skin condition of unknown aetiology which usually requires life-long treatment. It is regarded a systemic inflammatory disease with a possible increased risk of cardiovascular disease. The aim of this study was to assess carotid intima-media thickness (IMT), plaque prevalence and carotid stenosis as surrogate measures for cardiovascular disease in psoriasis patients and healthy controls. Methods: Sixty-two patients with psoriasis and thirty-one healthy controls were included in the study. All were examined by Colour duplex ultrasound of the carotid arteries to compare carotid IMT values, carotid plaques and carotid stenosis in the two groups. Adjustments were made for traditional cardiovascular risk factors. Results: Patients with psoriasis had increased carotid IMT values compared to the controls: mean ± SD 0.71 ± 0.17 mm vs. 0.59 ± 0.08 mm; p = 0.001. When adjusted for known atherosclerotic risk factors this difference remained significant (p = 0.04). Carotid plaques were also more common (p = 0.03) in patients with psoriasis 13 (21%) compared to controls 1 (3%). There was no difference with regard to the number of carotid stenoses in patients and controls. Conclusion: The results of this study support previous evidence which suggests that psoriasis is associated with an increased risk for atherosclerosis and subsequent cardiovascular disease.     

Characteristics of carotid atherosclerosis in patients with plaque erosion

Journal of Thrombosis and Thrombolysis - Plaque erosion (PE) is a major underlying mechanism of acute coronary syndrome (ACS). Patients with PE may have less systemic atherosclerosis. We aimed to...     

Long-term use of oral nicorandil stabilizes coronary plaque in patients with stable angina pectoris

ObjectiveThe Impact of Nicorandil in Angina (IONA) trial demonstrated that the use of nicorandil, an anti-anginal drug, reduced future cardiovascular events in patients with stable angina. We hypothesized that nicorandil has beneficial effects on coronary arterial plaque characteristics and atherosclerogenesis.Methods and ResultsPreintervention intravascular ultrasound-virtual histology was performed prospectively in 65 consecutive patients with stable angina pectoris. There were no differences in coronary risk factors between the nicorandil (n = 16) and non-nicorandil (n = 49) groups. However, the nicorandil group demonstrated a larger %fibrous tissue (68 ± 10 vs. 62 ± 11%, P = 0.049) and a smaller %necrotic core tissue (11 ± 7 vs. 16 ± 10%, P = 0.049) compared with the non-nicorandil group. Multiple regression analysis showed that %necrotic core tissue (P = 0.045) was negatively and %fibrous tissue (P = 0.026) was positively associated with the use of nicorandil independent of statin use. We also analyzed the effect of nicorandil on atherosclerotic lesion formation in a mouse model of atherosclerosis. Lipid profiles were unaffected, but the area of atherosclerotic lesion and plaque necrosis were significantly reduced following 8-week nicorandil treatment in ApoE-deficient mice fed an atherogenic diet. Nicorandil significantly reduced the expression levels of endoplasmic reticulum stress markers, C/EBP homologous protein (CHOP) and glucose regulated protein/BiP (GRP78) in atherosclerotic lesions. Nicorandil significantly attenuated tunicamycin-induced CHOP upregulation in cultured THP-1 macrophages.ConclusionsNicorandil exerts its anti-atherogenic effect by mechanisms different from those of statins. Long-term nicorandil treatment is a potentially suitable second-line prevention therapy for patients with coronary artery disease.