Ultrastructural Localization of Secretory Type II Phospholipase A2 in Atherosclerotic and Nonatherosclerotic Regions of Human Arteries

• Published in: Arteriosclerosis, thrombosis, and vascular biology Vol. 18; no. 4; pp. 519 - 525
• Main Authors: Romano, Mirtha, Romano, Egidio, Bjorkerud, Soren, Hurt-Camejo, Eva
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01-04-1998; Hagerstown, MD Lippincott
• Subjects: Antibodies, Monoclonal; Arteries - enzymology; Arteries - ultrastructure; Arteriosclerosis - enzymology; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Collagen - analysis; Extracellular Matrix - enzymology; Humans; Medical sciences; Microscopy, Immunoelectron; Phospholipases A - analysis; Phospholipases A2; Human; Enzyme; Pathogenesis; Cardiovascular disease; Esterases; Inflammation; Electron microscopy; Phospholipase A; Carboxylic ester hydrolases; Vascular disease; Pathology; Autopsy; Atherosclerosis; Hydrolases
• ISSN: 1079-5642; 1524-4636
• DOI: 10.1161/01.ATV.18.4.519

We recently reported on the immunolocalization of type II secretory nonpancreatic phospholipase A2 (snpPLA2) in human atherosclerotic lesions. In the present study, we present data on the distribution and ultrastructural localization of snpPLA2 in adjacent nonatherosclerotic and atherosclerotic regions of human arteries. Electron microscopy (EM) of immunogold labeling techniques with a monoclonal antibody was used to analyze arterial tissue. The human specimens analyzed were obtained from autopsy and surgery cases. The results with EM showed a stronger snpPLA2 immunoreactivity in regions of arteries with atherosclerotic lesions than in regions without lesions from the same individual. snpPLA2 immunoreactivity was stronger in the arterial intima of atherosclerotic than of nonatherosclerotic tissue. EM-immunogold examination revealed that the majority of snpPLA2 was localized along the extracellular matrix, associated with collagen fibers and other extracellular matrix structures. Intracellular snpPLA2 was observed in electron-dense vesicles in intimal cells. snpPLA2 was also found in contact with large, extracellular lipid droplets. These results support the hypothesis that extracellular snpPLA2 is localized at sites where it may hydrolyze phospholipids from lipoproteins and lipid aggregates retained in the extracellular matrix of the arterial wall. This may be a mechanism for in situ release of proinflammatory lipids, free fatty acids, and lysophosphatidylcholine in regions of apolipoprotein B accumulation, which are abundant in atherosclerotic lesions. (Arterioscler Thromb Vasc Biol. 1998;18:519-525.)