Methods: We first checked the viability of murine macrophage cells, RAW264.7, cultured with LDL or HDL, and examined whether these cells change to foam cells stained with Oil red O. Digital images were obtained using a CCD camera connected to the optical microscope. The flow test in the micro-channel chip was performed to clarify whether adhesion molecule is involved in the plaque formation of RAW264.7 cells. Expression of adhesion molecule was examined by immunofluorescent staining with a flurochrome-conjugated secondary antibody to determine whether culture with LDL or HDL affects the expression of adhesion molecules on RAW264.7 cells.
Results: Culture with LDL or HDL did not affect the cell viability of RAW264.7. The percentage of stained area increased for the RAW264.7 cells cultured with LDL, not HDL. The flow test revealed that culture with LDL increased the plaque formation of RAW264.7 cells, however culture with HDL did not. ICAM-1 expression on the surface of RAW264.7 cells was increased by culture with LDL, not with HDL. An increase in ICAM-1 expression in time-dependent manner was also confirmed by immnofluorescent staining.
Conclusion: These findings indicate that LDL, not HDL, induces the macrophages to foam cells and that ICAM-1 plays an important role in plaque formation of murine macrophages cultured with LDL, not with HDL.