Electronegative low-density lipoprotein increases C-reactive protein expression in vascular endothelial cells through the LOX-1 receptor.
OBJECTIVE
Increased plasma C-reactive protein (CRP) levels are associated with the occurrence and severity of acute coronary syndrome. We investigated whether CRP can be generated in vascular endothelial cells (ECs) after exposure to the most electronegative subfraction of low-density lipoprotein (LDL), L5, which is atherogenic to ECs. Because L5 and CRP are both ligands for the lectin-like oxidized LDL receptor-1 (LOX-1), we also examined the role of LOX-1.


RESULTS
Plasma LDL samples isolated from asymptomatic hypercholesterolemic (LDL cholesterol [LDL-C] levels, 154.6±20 mg/dL; n = 7) patients and normocholesterolemic (LDL-C levels, 86.1±21 mg/dL; P<0.001; n = 7) control individuals were chromatographically resolved into 5 subfractions, L1-L5. The L5 percentage (L5%) and the plasma L5 concentration ([L5]  =  L5% × LDL-C) in the patient and control groups were 8.1±2% vs. 2.3±1% (P<0.001) and 12.6±4 mg/dL vs. 1.9±1 mg/dL (P<0.001), respectively. In hypercholesterolemic patients treated with atorvastatin for 6 months (10 mg/day), [L5] decreased from 12.6±4 mg/dL to 4.5±1.1 mg/dL (P = 0.011; n = 5), whereas both [L5] and L5% returned to baseline levels in 2 noncompliant patients 3 months after discontinuation. In cultured human aortic ECs (HAECs), L5 upregulated CRP expression in a dose- and time-dependent manner up to 2.5-fold (P<0.01), whereas the least electronegative subfraction, L1, had no effect. DiI-labeled L1, internalized through the LDL receptor, became visible inside HAECs within 30 seconds. In contrast, DiI-labeled L5, internalized through LOX-1, became apparent after 5 minutes. L5-induced CRP expression manifested at 30 minutes and was attenuated by neutralizing LOX-1. After 30 minutes, L5 but not L1 induced reactive oxygen species (ROS) production. Both L5-induced ROS and CRP production were attenuated by ROS inhibitor N-acetyl cysteine.


CONCLUSIONS
Our results suggest that CRP, L5, and LOX-1 form a cyclic mechanism in atherogenesis and that reducing plasma L5 levels with atorvastatin disrupts the vascular toxicity of L5.
Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
Chih-Sheng
CS
Chu
Yu-Chen
YC
Wang
Long-Sheng
LS
Lu
Brian
B
Walton
H Ramazan
HR
Yilmaz
Roger Y
RY
Huang
Tatsuya
T
Sawamura
Richard A F
RA
Dixon
Wen-Ter
WT
Lai
Chu-Huang
CH
Chen
Jonathan
J
Lu
D000328:Adult; D000924:Anticholesteremic Agents / Q000627:therapeutic use; D000069059:Atorvastatin; D002097:C-Reactive Protein / Q000032:analysis / Q000378:metabolism*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism*; D005260:Female; D006538:Heptanoic Acids / Q000627:therapeutic use; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000188:drug therapy / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000097:blood / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011758:Pyrroles / Q000627:therapeutic use; D017382:Reactive Oxygen Species / Q000378:metabolism; D051127:Scavenger Receptors, Class E / Q000378:metabolism*
D000924:Anticholesteremic Agents; D006538:Heptanoic Acids; D008077:Lipoproteins, LDL; C495137:OLR1 protein, human; D011758:Pyrroles; D017382:Reactive Oxygen Species; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein; D002097:C-Reactive Protein; D000069059:Atorvastatin