Interaction of Platelets, Macrophages and Lipoproteins in Relation to Atherogenes

Abstract

Both macrophages and platelets have been considered as key cells in the cellular pathology of atherosclerosis for many years. Their suggested role however has been progressively modified as experimental data has emerged. Recent studies for example, have demonstrated the presence of receptors to modified LDL in macrophages (1,2) and have renewed early interest (3,4) in the reticuloendothelial system in the formation of foam cells in early atherogenesis. Recent interest in platelets has centred on the involvement on prostacyclin and thromboxane on platelet aggregation and on the effect of platelet growth factors in the proliferation of arterial wall cells (5,6). There are a number of studies however which suggest that platelets might also promote cellular lipid accumulation and foam cell formation in the early lesion. Platelet thrombi injected in vivo stimulate the formation of macrophage foam cells (7,8). Where endothelial injury occurs (either by indwelling catheters or by repeated ballooning) platelet deposition is followed by the development of lipid containing cell lesions (9,10) with composition and metabolic characteristics of early atherogenesis (11). In the present study the interaction of platelets on various aspects of lipid uptake and metabolism in rabbit peritoneal macrophages is studied in vitro and some preliminary data on possible mechanisms for platelet involvement in foam cell formation suggested.