The basis by which macrophage-to-endothelial cell crosstalk by 27HC participates in atherosclerosis development was further delineated with the finding that increases in endothelial cell ICAM-1 and VCAM-1 expression above those found in the absence of macrophage cyp27a1 and endothelial ERα were only promoted by macrophage cyp27a1 in mice expressing the receptor in endothelium (Fig. 2n, o). This evidence concerns the gene CYP27A1 and atherosclerosis.