Wnt5a Signaling in Atherosclerosis, its Effect on OxLDL Uptake and Foam Cell Differentiation

Abstract

Atherosclerosis is a chronic inflammatory disease involving plaque buildup in the arteries and can lead to heart attack and stroke. A key step in the pathogenesis of atherosclerosis is oxLDL uptake by macrophages. Our lab has shown that oxLDL up regulated transcription of Wnt5a in macrophages. Wnt5a and Frizzled 5 (Fz5), a Wnt5a receptor, are highly expressed in foam cells in atherosclerosis. Our hypothesis is that Wnt5a stimulates oxLDL uptake and that macrophages show differential expression of Wnt5a receptors.In vitro studies: THP‐1 cell line was cultured and differentiated into macrophages. Cells were treated with oxLDL, nLDL, and rWnt5a in combinations to determine their effects on oxLDL uptake. Expression of receptors involved in oxLDL uptake such as CD68, CD36, and scavenger receptor (SR) were analyzed using immunofluorescence, western blot and PCR. To study Wnt5a signaling ROR2, Fz5, and Wnt5a were evaluated in THP‐1 cells as well as in human atherosclerotic tissue samplesIn THP‐1 cells oxLDL and Wnt5a increased CD68, CD36, SR and Fz5 at both protein and RNA level. IHC results show that Wnt5a is expressed by macrophages, foam cells, smooth muscle cells (SMC), and endothelial cells. But Fz5 is expressed only by some macrophages, and almost negative in SMC. We also found that ROR2 followed a similar expression pattern to Fz5 in macrophages while SMC near the lipid core were positive for ROR2 but negative for Fz5.In conclusion, our results suggest that oxLDL, through Wnt5a signaling, plays a role in foam cell formation and oxLDL uptake. In addition, expression of Wnt5a receptors is variable between cell types in atherosclerosis.