Analysis of secretory group II phospholipase A2 expression in human aortic tissue in dependence on the degree of atherosclerosis

Secretory non-pancreatic (group II) phospholipase A2 (sPLA2) releases precursors of important mediators of inflammation from phospholipids. Based on the inflammatory character of atherosclerosis we previously described the identification of sPLA2 in human atherosclerotic plaques. In vitro studies on lipoproteins have shown that sPLA2 is able to favour the formation of foam-like cells representing a typical feature of early atherosclerotic lesions. In the present study the expression of sPLA2 in relation to the degree of atherosclerosis was investigated. Aortic tissue samples of 25 autopsy cases ranging in age from 1 to 77 years were taken from 2 cm above the heart and 3 cm below the renal arteries. The material was classified regarding the degree of atherosclerotic changes based on staining with haemalaun and eosine as well as on staining according to Goldner. Furthermore, immunohistochemical procedures detecting sPLA2, macrophages and smooth muscle cells were performed. The study has shown that in the abdominal aorta the enzyme was present in all advanced atherosclerotic lesions, but only in some preatheromas and precursors of atherosclerosis. However, this correlation did not occur in the thoracic aorta, where sPLA2-positive results showed a similar frequency in all degrees of atherosclerotic lesion. The enzyme was found in all three layers of the vessel wall without significant differences. Round cells, scarcely smooth muscle cells and endothelial cells were identified as sPLA2-positive. However, these data do not allow a conclusion as to which type of cell is responsible for the secretion of sPLA2. In summary, the correlation between the expression of this enzyme and the degree of atherosclerosis underlines the possible importance of sPLA2 in atherogenesis.