Oxidized low-density lipoprotein induces apoptosis in endothelial progenitor cells by inactivating the phosphoinositide 3-kinase/Akt pathway

J Vasc Res. 2010;47(6):519-30. doi: 10.1159/000313879. Epub 2010 Apr 30.

Abstract

We tested the hypothesis that oxidized low-density lipoprotein (oxLDL)-induced inactivation of Akt within endothelial progenitor cells (EPCs) is mediated at the level of phosphoinositide 3-kinase (PI3K), specifically by nitrosylation of the p85 subunit of PI3K, and that this action is critical in provoking oxLDL-induced EPC apoptosis. Hypercholesterolemic ApoE null mice had a significant reduction of the phosphorylated Akt (p-Akt)/Akt ratio in EPCs, as well as a greater percentage of apoptosis in these cells than EPCs isolated from wild-type (WT) C57Bl/6 mice. EPCs were isolated from WT spleen and exposed to oxLDL in vitro. oxLDL increased O₂⁻ and H₂O₂ in these cells and induced a dose- and time-dependent reduction in the p-Akt/Akt ratio and increase in EPC apoptosis. These effects were significantly reduced by the antioxidants superoxide dismutase, L-NAME, epicatechin and FeTPPs. oxLDL also induced nitrosylation of the p85 subunit of PI3K and subsequent dissociation of the p85 and p110 subunits, an effect significantly reduced by all the antioxidant agents tested. EPC transfection with a constitutively active Akt isoform (Ad-myrAkt) significantly reduced oxLDL-induced apoptosis of WT EPCs. The present findings indicate that oxLDL disrupts the PI3K/Akt signaling pathway at the level of p85 in EPCs. This dysfunction can be reversed by ex vivo antioxidant therapy.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antioxidants / pharmacology
  • Apolipoproteins E / deficiency
  • Apolipoproteins E / genetics
  • Apoptosis* / drug effects
  • Cells, Cultured
  • Disease Models, Animal
  • Endothelial Cells / drug effects
  • Endothelial Cells / enzymology*
  • Endothelial Cells / pathology
  • Enzyme Activation
  • Hydrogen Peroxide / metabolism
  • Hypercholesterolemia / enzymology*
  • Hypercholesterolemia / genetics
  • Hypercholesterolemia / pathology
  • Lipoproteins, LDL / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mutation
  • Oxidative Stress
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Signal Transduction* / drug effects
  • Stem Cells / drug effects
  • Stem Cells / enzymology*
  • Stem Cells / pathology
  • Superoxides / metabolism
  • Time Factors
  • Transfection

Substances

  • Antioxidants
  • Apolipoproteins E
  • Lipoproteins, LDL
  • oxidized low density lipoprotein
  • Superoxides
  • Hydrogen Peroxide
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-akt