Comparative Study of Protein Expression Levels of Five Plaque Biomarkers and Relation with Carotid Plaque Type Classification in Patients after Carotid Endarterectomy
Contributor:Volume: 2018 No:1 2018
DOD: https://www.hindawi.com/journals/ijvm/2018/4305781/
Abtsract
Atherosclerosis is an inflammatory process resulting in local plaque deposition in the vessel wall of arteries with symptoms to various areas of vascular tree. Identification of patients with progressive advanced atherosclerotic disease is mainly based on the known characteristics of the vulnerable or recently ruptured plaque. Molecular and cellular features associated with the vulnerable plaque are considered potential diagnostic markers for plaque rupture and thrombosis. Here, protein expression levels of the metalloproteases MMP-1, MMP-9, osteopontin (OPN), and cytokines TNFα and IL-6 in tissue extracts of carotid plaques in patients after endarterectomy were estimated by Western immunoblotting, after SDS-PAGE analysis and evaluated based on the ultrasonographic plaque morphology. The gender and age effect was also examined. MMP-1, MMP-9, and IL-6 were expressed in higher levels compared to OPN and TNFa as well as in symptomatic (with type II and III carotid plaque classification) than asymptomatic (type IV) patients with differences considered statistically significant (P values <0.05). A significant positive correlation between MMP-1 and IL-6 (with Pearson correlation coefficient 0.748) is also notable. The data give further insight into the possible role of specific biomarker and enhance the need for further studies in order to clarify the proper one(s) for detection of the vulnerable plaque and help identify patients at risk for cardiovascular events.
Content
1. Introduction
Atherosclerosis is a chronic, inflammatory disease of the medium and large arteries, such as the aorta and carotid arteries. It is a major contributor to the development of cardiovascular diseases and the leading cause of death worldwide. Although atherosclerotic plaque development is a local process in the vessel wall that can give rise to symptoms in one specific area, it is also a systemic disease with simultaneous plaque formation in different areas of the vasculature [1–3]. Moreover, studies have shown that atherosclerotic carotid arteries pose a substantial risk of ipsilateral cerebrovascular events, with reported annual ischemic stroke rates ranging from 0.35% to 1.3% in asymptomatic patients with moderate stenosis [4, 5] and from 0.5% up to 5% for severe asymptomatic carotid artery stenosis [5, 6].
Atherosclerotic plaques are characterized by intimal thickening from the progressive accumulation of lipids [1, 2] together with other cellular and molecular components such as smooth muscle cells, monocytes, T cells, B lymphocytes, erythrocytes, and platelets. These cells are able to produce and secrete mediator molecules such as cytokines, chemokines, growth-factors, enzymes, and disintegrins, which activate endothelial cells, proliferation of smooth muscle cells, and lesion progression, and contribute to the weakening of a vulnerable plaque by matrix degradation of its fibrous cap. Many of these involved molecules can be measured systemically, and it has been shown that elevated concentrations in the circulation are associated with future cardiovascular events.
In other reports, for example, serum markers such as high-sensitive C-reactive protein, interleukin-6 [7–9], and IL-18 [10] are correlated with the development, progression, and rupture of atherosclerotic plaque [2, 11]. It is also suggested that inflammatory markers are transcribed locally in atherosclerotic plaques [12–15].
Other markers that have been previously associated with cardiovascular events and are now associated with carotid atherosclerotic plaques are matrix metalloproteinases (MMPs) [16], tissue inhibitor of metalloproteases (TIMP) [17], soluble intercellular adhesion molecule 1 [18], and osteopontin [14, 19]. MMPs are a family of zinc-containing enzymes and are secreted as inactive precursors; they are prevalent in the arterial wall throughout the arterial system and play a central role in degradation of the vascular extracellular matrix resulting in destabilization of the atherosclerotic plaque [16]. The destabilization event contributes to plaque rupture and consequently in acute ischaemic events. Increased carotid MMP-9 plaque levels are associated with an unstable plaque phenotype and are higher in lipid-rich inflammatory plaques. Osteopontin, an acidic phosphoprotein, has recently been demonstrated to inhibit mineral deposition as well as osteoclastogenesis and is constitutively expressed by a wide range of cell types in the vasculature. Carotid plaque contains valuable information for follow-up after vascular surgery. It has been shown that local plaque characteristics are associated with restenosis at the site of carotid endarterectomy after 1 year and endarterectomy of lipid-rich, inflammatory plaques, associated with reduced risk of restenosis compared to stable, fibrous plaques, independent from clinical characteristics [20].
It has been also reported that carotid plaque composition contains predictive information for future cardiovascular events elsewhere in the vascular system, independent from established risk factors and medication. Moreover, patients undergoing carotid endarterectomy, with a local plaque containing intra plaque hemorrhage or marked intra plaque micro vessel formation, demonstrated an increased risk of secondary cardiovascular events with high hazard ratios [21, 22]. Thus, determination of these molecules may give important prognostic information and may in turn be useful in improving risk stratification. However, for most of these biomarkers the clinical utility and their specificity have not yet been established.
This study looks at evaluating carotid plaques in symptomatic and asymptomatic patients after endarterectomy in order to potentially detect vulnerable plaques, based on the differences in protein expression levels of five biomarkers.