Acute inflammatory reactions caused by histamine via monocytes/macrophages chronically participate in the initiation and progression of atherosclerosis

Abstract

Previously we demonstrated that histidine decarboxylase (HDC), which produces histamine from l-histidine, was detected in monocytes/macrophages located in human atherosclerotic lesions. As monocytic migration is a key event of atherogenesis, we investigated whether histamine induces monocytic expression of monocyte chemoattractant protein (MCP)-1 and its receptors CCR2-A and -B, and also endothelial expression of ICAM-1 and VCAM-1. Furthermore, we studied the effect of interleukin (IL)-4, which inhibits the HDC expression, on the expression of MCP-1 and CCR2. Histamine stimulated monocytes, but not macrophages, to express MCP-1 and CCR2-A and -B. The expression of MCP-1 was inhibited by histamine H2 blocker. In contrast, IL-4 enhanced CCR2 expression but not MCP-1. Histamine stimulated endothelial cells to express ICAM-1 and VCAM-1. These results indicate that histamine and IL-4, which are both synthesized in the arterial intima, chronically participates in the pathogenesis of atherosclerosis via the enhanced expression of monocytic MCP-1, CCR2 and endothelial adhesion molecules.