HDL-Mediated Lipid Influx to Endothelial Cells Contributes to Regulating Intercellular Adhesion Molecule (ICAM)-1 Expression and eNOS Phosphorylation

• Published in: International journal of molecular sciences Vol. 19; no. 11; p. 3394
• Main Authors: Muñoz-Vega, Mónica, Massó, Felipe, Páez, Araceli, Vargas-Alarcón, Gilberto, Coral-Vázquez, Ramón, Mas-Oliva, Jaime, Carreón-Torres, Elizabeth, Pérez-Méndez, Óscar
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 30-10-2018; MDPI
• Subjects: Apolipoproteins; Atherosclerosis; Cell adhesion; Cholesterol; Confocal microscopy; Coronary artery disease; Endothelial cells; endothelial function; Endothelium; Experiments; Flow cytometry; Fluorescence; HDL cholesterol; HDL sphingomyelin; Heart diseases; High density lipoprotein; High density lipoprotein receptors; HMEC-1; inflammation; Intercellular adhesion molecule 1; Internalization; Kinetics; Lipids; Lipoproteins; Low density lipoprotein; Microvasculature; Nitric oxide; Nitric-oxide synthase; Phosphorylation; Physiology; Proteins; reverse cholesterol transport; Scavenger receptors; Sphingomyelin; SR-BI; Tumor necrosis factor-TNF; Vascular cell adhesion molecule 1; atherosclerosis; endothelial function; SR-BI; reverse cholesterol transport; inflammation; HDL sphingomyelin; HMEC-1; vascular cell adhesion molecule-1; HDL cholesterol
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms19113394

Reverse cholesterol transport (RCT) is considered as the most important antiatherogenic role of high-density lipoproteins (HDL), but interventions based on RCT have failed to reduce the risk of coronary heart disease. In contrast to RCT, important evidence suggests that HDL deliver lipids to peripheral cells. Therefore, in this paper, we investigated whether HDL could improve endothelial function by delivering lipids to the cells. Internalization kinetics using cholesterol and apolipoprotein (apo) AI fluorescent double-labeled reconstituted HDL (rHDL), and human dermal microvascular endothelial cells-1 (HMEC-1) showed a fast cholesterol influx (10 min) and a slower HDL protein internalization as determined by confocal microscopy and flow cytometry. Sphingomyelin kinetics overlapped that of apo AI, indicating that only cholesterol became dissociated from rHDL during internalization. rHDL apo AI internalization was scavenger receptor class B type I (SR-BI)-dependent, whereas HDL cholesterol influx was independent of SR-BI and was not completely inhibited by the presence of low-density lipoproteins (LDL). HDL sphingomyelin was fundamental for intercellular adhesion molecule-1 (ICAM-1) downregulation in HMEC-1. However, vascular cell adhesion protein-1 (VCAM-1) was not inhibited by rHDL, suggesting that components such as apolipoproteins other than apo AI participate in HDL's regulation of this adhesion molecule. rHDL also induced endothelial nitric oxide synthase eNOS S1177 phosphorylation in HMEC-1 but only when the particle contained sphingomyelin. In conclusion, the internalization of HDL implies the dissociation of lipoprotein components and a SR-BI-independent fast delivery of cholesterol to endothelial cells. HDL internalization had functional implications that were mainly dependent on sphingomyelin. These results suggest a new role of HDL as lipid vectors to the cells, which could be congruent with the antiatherogenic properties of these lipoproteins.