Urokinase-type Plasminogen Activator Receptor (uPAR) And Arterial Sclerosis Correlation Between Atherosclerosis

Background Fibrinolytic system exerts pleiotropic functions over the course of many physiologic and pathological processes, including cell migration, tissue remodeling and inflammation response. The urokinase-type-plasminogen-activator receptor (uPAR) is a key molecular of this system and can bind both extracellular moleculars and cell membrane moleculars, such as urokinase type plasminogen activator (uPA), vitronectin (VN), and integrins and so on. As a glycosylphosphatidylinositol-linked receptor, uPAR not only plays a key role in cell suface-associated proteolysis, but also involved in several processes not related to plasminogen activation including cellular adhesion, proliferation and chemotaxis, all of which are fundamental processes in atherogenesis. More and more studies had implicated that uPAR plays an important role in the development of atherogenesis, but the exact mechanism still remains to be elucidated.Objectives Using the animal model of atherogenesis, we determined the levels of uPAR of monocytes or macrophages both in peripheral vessels and in atherosclerotic plaques with different degrees of atherosclerotic lesions. The purpose is to evaluate the relationship between atherogenesis and the expression of uPAR.Methods39Male apolipoprotein E-knockout mice were randomised into6groups from the age of8weeks, including3control groups (Group1,11and III,6mice in each group) and3experimental groups (Group IV, V and VI,7mice in each group). The animals of experimental groups were fed a high-fat, cholesterol-enriched diet, while the control groups were fed a normal diet. Animals were euthanized at3-week intervals between10and16weeks of feeding, with1experimental group and1control group were euthanized each time. During dissection, the body weight of each animal were recorded, the peripheral blood and cardiovascular pathological samples were collected. The proportion of peripheral monocytes expressing uPAR was surveyed by flow cytometer. For cardiovascular pathological samples, HE staining was used to search and count the number of atherosclerotic plaques with different degrees of atherosclerotic lesions. Immunohistochemistry and immunofluorescence were employed to detect the expression of uPAR protein as well as its association with macrophages and SMC in different type of plaque.Results First, this study built the animal model of atherogenesis successfully. The animals of experimental groups were all found different type of atherosclerotic plaques, while none of the animals in control groups was found any atherosclerotic plaques. Second, as the weeks went on, body weight of the animals in experimental groups increased rapidly. There was significant difference between these groups (p<0.05). At the same time, the degrees of atherosclerotic lesions were progressing weekly. More early lesions could be seen in animals with10weeks of high-fat diet, while more severe lesions could be found in animals with16weeks of high-fat diet. Third, Surface expression of uPAR on peripheral monocytes was significantly higher in animals with high-fat diet, compared with that in animals with normal diet (p<0.03). Even more, among the animals with high-fat diet, the expression of uPAR on peripheral monocytes increased as the fed weeks went on. There was significant difference between there experimental groups (p<0.01). Fourth, the level of uPAR in different type of plaques were detected and the results are showed as follows:calcified plaques(CP)> fibrous plaques(FP)> early lesions(EL)> normal areas(NA)(p<0.05); the core of CP or FP> the cap of CP or FP.Conclusions Our study confirmed that male apolipoprotein E-knockout mice fed with a high-fat, cholesterol-enriched diet can build the animal model of atherogenesis successfully. With the development of atherosclerotic plaques, the expression of uPAR on mouse peripheral monocytes increased gradually. With the degree of atherosclerotic plaques developing, the level of uPAR in atherosclerotic plaques increased gradually. All these data confirm that the overexpression of uPAR both in peripheral monocytes and in advanced atherosclerotic lesions contributes to atherosclerotic plaques’ development. This study provided new knowledge of monocyte/macrophage’s atherogenic role by uPAR, and further investigation was required to elucidate its mechanism and the possibility of clinical application.