The Expression and Functions of Toll-Like Receptors in Atherosclerosis

Figure 1

Toll-like receptor expression in atherosclerotic lesions is cell-type specific. Endothelial cell activation leads to increased expression of adhesion molecules, promoting the infiltration of monocytes into the subendothelial space. Recruited monocytes differentiate into macrophages, ingest lipid and become foam cells that are retained within the lesion, promoting plaque growth. Smooth muscle cells proliferate and migrate into the intima where they form a fibrous plaque over the necrotic core of the lesion. In addition, myleloid dendritic cells, plasmacytoid dendritic cells and lymphocytes are observed in lesions. Both immune and resident vascular cells in atherosclerotic arteries express a variety of toll-like receptors or increase their expression during disease development. Each cell type expresses a specific combination which might dictate its ability to respond to exogenous or endogenous ligands and the consequences of such stimulation. Ligation of toll-like receptors on cells within atherosclerotic plaques can lead to numerous downstream effects including; promoting monocyte recruitment, activation of plaque cells, induction of foam cell formation and activation of adaptive immune responses, which can all affect lesion development.