Angiogenesis and the atherosclerotic carotid plaque: an association between symptomatology and plaque morphology

Differences in the detection of cyclo-oxygenase 1 and 2 proteins in symptomatic and asymptomatic carotid plaques

BACKGROUND

The expression of cyclo-oxygenase (COX) 1 and 2 has been demonstrated in atherosclerotic arteries. In the present study this was correlated with symptoms arising from a carotid plaque.

METHODS

Carotid plaques from 12 asymptomatic patients were compared with 11 plaques from patients who had had neurological symptoms within the preceding 30 days. Sections were stained with haematoxylin and eosin, elastin van Gieson and goat antihuman antibodies to COX-1 and COX-2. Plaque morphology was correlated with neurological symptoms. The area with positive COX-1 and COX-2 staining was measured by computerized planimetry in entire cross-sections and in specific areas of the plaque.

RESULTS

There was a significant association between cap thinning and plaque rupture with symptoms (P = 0.003). The percentage area of positive staining in entire cross-sections for both COX-1 and COX-2 was significantly greater in symptomatic plaques (P = 0.001 and 0.0004 respectively). Staining in symptomatic plaques was significantly greater in the cap (COX-1: P = 0.001; COX-2: P = 0.0001) and shoulder (COX-1: P = 0.008; COX-2: P = 0.007) regions of the plaque. COX-1 expression in the sclerotic area was not increased (P = 0.15) although COX-2 staining was significantly greater (P = 0.04).

CONCLUSION

Both COX-1 and COX-2 detection was increased in symptomatic plaques. COX may contribute to plaque rupture and the onset of symptoms.

Association between plaque instability, angiogenesis and symptomatic carotid occlusive disease

BACKGROUND

Angiogenesis is a recognized feature of the atherosclerotic process and has been described in the context of unstable coronary atherosclerotic lesions. The aim of this study was to assess the association between angiogenesis in atherosclerotic carotid plaques and microscopic features of plaque instability, in particular intraplaque haemorrhage.

METHODS

Consecutive patients undergoing carotid endarterectomy were included. Endarterectomy specimens were divided into their constituent atherosclerotic lesions. Histological sections were prepared and stained with haematoxylin and eosin, and immunohistochemically with an endothelial cell marker (CD34). The quantity of intraplaque haemorrhage was measured in transverse histological sections using computerized image analysis. Microvessel counts were performed in CD34-stained sections and were verified through computerized image analysis.

RESULTS

Some 239 atherosclerotic lesions from 73 patients were available for analysis; 73 were early lesions, 74 were raised fibroatheromas and 92 were unstable atherosclerotic plaques. One hundred and fifty lesions were not haemorrhagic; 89 exhibited intraplaque haemorrhage, of which 28 involved less than 50 per cent of the plaque sectional area. There were higher microvessel counts in plaques containing over 50 per cent haemorrhage (P < 0.0001), unstable atherosclerotic lesions (P < 0.0001) and atherosclerotic lesions obtained from symptomatic patients (P < 0.001).

CONCLUSION

There are strong associations between plaque vascularity, quantity of intraplaque haemorrhage and presence of symptomatic carotid occlusive disease.

Angiogenesis and G-protein-coupled receptors: signals that bridge the gap

Angiogenesis is a mechanism that has repercussions in a number of physiological and pathological situations. Vascular endothelial growth factor and basic fibroblast growth factor have understandably received enormous research coverage for being the major mediators of new blood vessel growth, often overshadowing other agonist that also have strong angiogenic potential. We wish to put the spotlight on GPCR agonists that undoubtedly have their word to say on the subject of angiogenesis. In this short review, we will discuss our findings along with the work from other groups on the mechanisms by which GPCR agonists, like thrombin and angiotensin II, control a number of angiogenic signals. A complete understanding of these mechanisms could, by the design of new therapeutic strategies, have a strong impact in clinical oncology.

Therapeutic angiogenesis for ischemic heart disease

The de-novo formation of vessels (angiogenesis) and the remodelling of preexisting collateral vessels (arteriogenesis) are processes that occur naturally in ischemic heart disease. Promoting these processes by administration of various substances or other physical stimuli (therapeutic angiogenesis) may provide a future strategy for the treatment of ischemic vascular diseases. Mechanisms of angiogenesis and arteriogenesis, as well as trials of therapeutic angiogenesis in animal models and humans are reviewed.

The role of protein kinase C in the development of the complications of diabetes

Diabetes mellitus produces a state of chronic hyperglycemia which in turn leads to the development of severe complications including retinopathy, nephropathy, neuropathy, and atherosclerosis. Many different mechanisms have been put forward to attempt to explain how glucose elevations can damage these various organ systems. Protein kinase C activation is one of the sequelae of hyperglycemia and is thought to play a role in the development of diabetic complications. There are multiple mechanisms for its activation in the diabetic state and multiple downstream effects attributable to that activation. The role of protein kinase C activation in the development of the above-mentioned complications of diabetes is discussed in this chapter. In addition, the potential use of isoform-specific inhibitors of protein kinase C for the treatment of diabetic complications is proposed.

Localization of tissue transglutaminase in human carotid and coronary artery atherosclerosis: implications for plaque stability and progression

Although atherosclerosis progresses in an indolent state for decades, the rupture of plaques creates acute ischemic syndromes that may culminate in myocardial infarction and stroke. Mechanical forces and matrix metalloproteinase activity initiate plaque rupture, whereas tissue inhibitors of metalloproteinases have an important (albeit indirect) role in plaque stabilization. In this paper, an enzyme that could directly stabilize the plaque is described. Tissue transglutaminase (TG) catalyzes the formation of epsilon(gamma-glutamyl)lysine isopeptide bonds that are resistant to enzymatic, mechanical, and chemical degradation. We performed immunohistochemistry for TG in atherosclerotic human coronary and carotid arteries. TG was most prominent along the luminal endothelium and in the medium of the vessels with a distribution mirroring that of smooth muscle cells. Variable, often prominent, immunoreactivity for TG was also seen in the intima, especially in regions with significant neovascularization. Additionally, TG was detected in fibrous caps and near the "shoulder regions" of some plaques. A monoclonal antibody to the transglutaminase product epsilon(gamma-glutamyl)lysine isopeptide demonstrated co-localization with TG antigen. Transglutaminase activity was found in 6 of 14 coronary artery atherectomy samples. Cross-linking of TG substrates such as fibrinogen, fibronectin, vitronectin, collagen type I, and protease inhibitors stabilized the plaque. Furthermore, the activation of transforming growth factor-beta-1 by TG might be an additional mechanism for the promotion of plaque stabilization and progression by increasing the synthesis of extracellular matrix components.