Scavenger Receptor Collectin Placenta 1 (CL-P1) Predominantly Mediates Zymosan Phagocytosis by Human Vascular Endothelial Cells

Collectin placenta 1 (CL-P1), a recently discovered scavenger receptor, mediates the uptake of oxidized low density lipoprotein and microbes. In this study, we investigated CL-P1-mediated binding and ingestion of yeast-derived zymosan bioparticles using Chinese hamster ovary (CHO) cells stably expressing human CL-P1 (CHO/CL-P1) and human vascular endothelial cells constitutively expressed CL-P1. The uptake of zymosan by CHO/CL-P1 was dependent upon the level of CL-P1 expressed on the membrane and was inhibited by cytochalasin D and wortmannin. The binding of zymosan was also inhibited by ligands of other scavenger receptors such as poly(I) and dextran sulfate. Real time reverse transcription-PCR analyses showed that other scavenger receptors, namely LOX-1, Stabilin-2, or macrophage receptor with collagenous structure (MARCO), were not expressed in human umbilical vein endothelial cells isolated from different individuals. Nonopsonic zymosan ingestion was inhibited in three primary cultured vascular endothelial cells, including different human umbilical vein endothelial cells from nine individuals treated with CL-P1 small interfering RNAs, although small interfering RNAs of other scavenger receptors had no effect on zymosan uptake in these cells. Furthermore, we confirmed that CL-P1 is expressed in human and murine vascular endothelial layers. Our results demonstrated that CL-P1 predominantly mediated phagocytosis for fungi in vascular endothelia.