Oxidized LDL Receptor LOX-1 Binds to C-Reactive Protein and Mediates Its Vascular Effects

Abstract

Background: C-reactive protein (CRP) exerts biological activity on vascular endothelial cells. This activity may promote atherothrombosis, but the effects of this activity are still controversial. Lectin-like oxidized LDL receptor-1 (LOX-1), the oxidized LDL receptor on endothelial cells, is involved in endothelial dysfunction induced by oxidized LDL. methods: We used laser confocal microscopy to examine and fluorescence cell image analysis to quantify the binding of fluorescently labeled CRP to cells expressing LOX-1. We then examined the binding of unlabeled CRP to recombinant human LOX-1 in a cell-free system. Small interfering RNAs (siRNAs) against LOX-1 were applied to cultured bovine endothelial cells to analyze the role of LOX-1 in native cells. To observe its in vivo effects, we injected CRP intradermally in stroke-prone spontaneously hypertensive (SHR-SP) rats and analyzed vascular permeability. results: CRP bound to LOX-1–expressing cells in parallel with the induction of LOX-1 expression. CRP dose-dependently bound to the cell line and recombinant LOX-1, with significant binding detected at 0.3 mg/L CRP concentration. The Kd value of the binding was calculated to be 1.6 × 10–7 mol/L. siRNA against LOX-1 significantly inhibited the binding of fluorescently labeled CRP to the endothelial cells, whereas control RNA did not. In vivo, intradermal injection of CRP-induced vascular exudation of Evans blue dye in SHR-SP rats, in which expression of LOX-1 is greatly enhanced. Anti–LOX-1 antibody significantly suppressed vascular permeability. Conclusions: CRP and oxidized LDL-receptor LOX-1 directly interact with each other. Two risk factors for ischemic heart diseases, CRP and oxidized LDL, share a common molecule, LOX-1, as their receptor.

C-Reactive Protein Induces Release of Both Endothelial Microparticles and Circulating Endothelial Cells In Vitro and In Vivo: Further Evidence of Endothelial Dysfunction

“…We labeled another set of cells with antibodies to Annexin V, CD51, CD61, and CD42. After labeling, samples were analyzed by flow cytometry (29 ). For the EMP measurements, the flow cytometer was kept running for 30 min until the background events were Ͻ1%.…”

C-Reactive Protein Uptake by Macrophage Cell Line via Class-A Scavenger Receptor

“…In addition, we recently demonstrated that CRP increases vascular permeability through a direct binding to lectin-like oxidized LDL receptor (LOX-1), which is expressed in endothelial cells (10 ). Members of the scavenger receptor family, such as class A scavenger receptor (SR-A), CD36, LOX-1, and scavenger receptor B-I (SR-BI), recognize common ligands such as modified LDL, bacteria, and advanced glycation end products, and they are thought to affect the progression of atherosclerosis (11,12 ).…”

Monomeric C-Reactive Protein Decreases Acetylated LDL Uptake in Human Endothelial Cells

“…Li et al (10 ) found that CRP may trigger the effects of oxLDL on endothelial cells by upregulating LOX-1. More recently, Fujita et al (11 ) reported that CRP binds to LOX-1-expressing bovine endothelial cells parallel with induction of LOX-1 expression. These observations prompted us to investigate the involvement of CD16, CD32, and LOX-1 in mediating nCRP/mCRP regulation of acetylated LDL (acLDL) uptake.…”