LOX-1 augments oxLDL uptake by lysoPC-stimulated murine macrophages but is not required for oxLDL clearance from plasma

J Lipid Res. 2009 Aug;50(8):1676-84. doi: 10.1194/jlr.M900167-JLR200. Epub 2009 Apr 9.

Abstract

Oxidized LDL (oxLDL) promotes lipid accumulation as well as growth and survival signaling in macrophages. OxLDL uptake is mainly due to scavenger receptors SR-AI/II and CD36. However, other scavenger receptors such as lectin-like oxLDL receptor-1 (LOX-1) may also play a role. We used mice with targeted inactivation of the LOX-1 gene to define the role of this receptor in the uptake of oxLDL and in activation of survival pathways. There was no difference in uptake or degradation of 125I-oxLDL in unstimulated macrophages from wild-type and LOX-1 knockout mice and no difference in the rate of clearance of oxLDL from plasma in vivo. However, when expression of LOX-1 was induced with lysophosphatidylcholine, oxLDL uptake and degradation increased 2-fold in wild-type macrophages but did not change in LOX-1 knockout macrophages. Macrophages lacking LOX-1 showed the same stimulation of PKB phosphorylation and enhancement of survival by oxLDL as wild-type cells. These data show that LOX-1 does not alter the uptake of oxLDL in unstimulated macrophages and is not essential for the pro-survival effect of oxLDL in these cells. However, LOX-1 expression is highly inducible by lysophosphatidylcholine and pro-inflammatory cytokines, and if that occurred in macrophages within atheromas, LOX-1 could substantially increase oxLDL uptake by lesion macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Biological Transport
  • Cell Survival
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Female
  • Gene Expression Regulation
  • Lipoproteins, LDL / blood
  • Lipoproteins, LDL / metabolism*
  • Lysophosphatidylcholines / pharmacology*
  • Macrophages / metabolism*
  • Macrophages, Peritoneal / cytology
  • Macrophages, Peritoneal / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Oxidation-Reduction
  • Phenotype
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Scavenger Receptors, Class E / deficiency
  • Scavenger Receptors, Class E / genetics
  • Scavenger Receptors, Class E / metabolism*

Substances

  • Lipoproteins, LDL
  • Lysophosphatidylcholines
  • Olr1 protein, mouse
  • RNA, Messenger
  • Scavenger Receptors, Class E
  • oxidized low density lipoprotein
  • stearoyl alpha-lysolecithin
  • Proto-Oncogene Proteins c-akt