Monocyte-derived macrophage migration and foam cell trapping are the main events in the progression of atherosclerosis.Tropomodulin1 (Tmod1), a capping protein at the pointed-end of actin filaments, is critical to actin dynamics.To investigate the role of Tmod1 in these two events, we examined the expression of Tmod1 in the cells by quantitative real time PCR.Data showed that Tmod1 level was low in mouse peritoneal macrophages as compared with primary peripheral blood mononulear cells.Similar result was obtained in PMA-stimulated human THP-1 monocytes.But interestingly, Tmod1 was up-regulated in ox-LDL treated mouse macrophages.Tmod1 expression was also found increased in high fat serum or TNF-α treated macrophages but no change in cholesterol treated macrophages.The data suggests a biphasic expression pattern of Tmod1 in monocyte-derived macrophages and foam cells.Low Tmod1 level in macrophages may be necessary for their migration, while the increased Tmod1 level in foam cells may contribute to their trapping.