Expression of macrophage-derived chemokine (CCL22) in atherosclerosis and regulation by histamine via the H2 receptor.

Macrophage-derived chemokine (CCL22) is a member of the CC-family of chemokines and is synthesized by monocyte-derived macrophages and dendritic cells (DCs). In this study, we investigate the relationship between monocytes/macrophages and histamine in atherosclerosis and discover that histamine levels regulate various immunologically important molecules and influences atherosclerotic progression. Immunohistochemical analysis of human atherosclerotic lesions revealed that macrophages and DCs express CCL22. The human acute monocytic leukemia cell line (THP-1) adhered to culture plates and morphologically changed to macrophage-like cells when treated with tetradecanoylphorbol-13-acetate (TPA). Macrophage-like cells derived from THP-1 cells and cultivated peripheral blood mononuclear cells (PBMCs) show similar expression of CCL22. Gene expression of CCL22 was also detected in THP-1 cells treated with histamine and the expression of the protein produced by the CCL22 gene is similar in PBMCs and THP-1 cells. In addition, the histamine H2 receptor mediated these reactions. Our results suggest that CCL22 expression in monocytes is regulated by histamine, and that CCL22 is involved centrally in the development of human atherosclerotic lesions. In conclusion, CCL22 is a marker that is a characteristic of the monocytes/ macrophages migrating into atherosclerotic lesions and histamine plays a role in regulating its expression.