Strong induction of members of the chitinase family of proteins in atherosclerosis: chitotriosidase and human cartilage gp-39 expressed in lesion macrophages

Abstract

Atherosclerosis is initiated by the infiltration of monocytes into the subendothelial space of the vessel wall and subsequent lipid accumulation of the activated macrophages. The molecular mechanisms involved in the anomalous behavior of macrophages in atherogenesis have only partially been disclosed. Chitotriosidase and human cartilage gp-39 (HC gp-39) are members of the chitinase family of proteins and are expressed in lipid-laden macrophages accumulated in various organs during Gaucher disease. In addition, as shown in this study, chitotriosidase and HC gp-39 can be induced with distinct kinetics in cultured macrophages. We investigated the expression of these chitinase-like genes in the human atherosclerotic vessel wall by in situ hybridizations on atherosclerotic specimens derived from femoral artery (4 specimens), aorta (4 specimens), iliac artery (3 specimens), carotid artery (4 specimens), and coronary artery (1 specimen), as well as 5 specimens derived from apparently normal vascular tissue. We show for the first time that chitotriosidase and HC gp-39 expression was strongly upregulated in distinct subsets of macrophages in the atherosclerotic plaque. The expression patterns of chitotriosidase and HC gp-39 were compared and shown to be different from the patterns observed for the extracellular matrix protein osteopontin and the macrophage marker tartrate-resistant acid phosphatase. Our data emphasize the remarkable phenotypic variation among macrophages present in the atherosclerotic lesion. Furthermore, chitotriosidase enzyme activity was shown to be elevated up to 55-fold in extracts of atherosclerotic tissue. Although a function for chitotriosidase and HC gp-39 has not been identified, we hypothesize a role in cell migration and tissue remodeling during atherogenesis.