Prior exposure to oxidized low-density lipoprotein limits apoptosis in subsequent generations of endothelial cells by altering promoter methylation

Am J Physiol Heart Circ Physiol. 2011 Aug;301(2):H506-13. doi: 10.1152/ajpheart.00252.2011. Epub 2011 May 20.

Abstract

Oxidized LDL (ox-LDL) plays a critical role in atherogenesis, including apoptosis. As hypercholesterolemia causes epigenetic changes resulting in long-term phenotypic consequences, we hypothesized that repeated and continuous exposure to ox-LDL may alter the pattern of apoptosis in human umbilical vein endothelial cells (HUVECs). We also analyzed global and promoter-specific methylation of apoptosis-related genes. As expected, ox-LDL evoked a dose-dependent increase in apoptosis in the first passage HUVECs that was completely abrogated by lectin-like ox-LDL receptor (LOX-1)-neutralizing antibody. Ox-LDL-induced apoptosis was associated with upregulation of proapoptotic LOX-1, ANXA5, BAX, and CASP3 and inhibition of antiapoptotic BCL2 and cIAP-1 genes accompanied with reciprocal changes in the methylation of promoter regions of these genes. Subsequent passages of cells displayed attenuated apoptotic response to repeat ox-LDL challenge with blunted gene expression and exaggerated methylation of LOX-1, BAX, ANXA5, and CASP3 genes (all P < 0.05 vs. first exposure to ox-LDL). Treatment of cells with LOX-1 antibody before initial ox-LDL treatment prevented both gene-specific promoter methylation and expression changes and reduction of apoptotic response to repeat ox-LDL challenge. Based on these data, we conclude that exposure of HUVECs to ox-LDL induces epigenetic changes leading to resistance to apoptosis in subsequent generations and that this effect may be related to the LOX-1-mediated increase in DNA methylation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Analysis of Variance
  • Antibodies, Neutralizing
  • Apoptosis / genetics*
  • Apoptosis Regulatory Proteins / genetics*
  • Atherosclerosis / genetics
  • Atherosclerosis / metabolism*
  • Atherosclerosis / pathology
  • Cell Proliferation*
  • Cells, Cultured
  • DNA Methylation*
  • Endothelial Cells / metabolism*
  • Endothelial Cells / pathology
  • Gene Expression Regulation
  • Humans
  • Lipoproteins, LDL / metabolism*
  • Phenotype
  • Promoter Regions, Genetic*
  • Scavenger Receptors, Class E / immunology
  • Scavenger Receptors, Class E / metabolism

Substances

  • Antibodies, Neutralizing
  • Apoptosis Regulatory Proteins
  • Lipoproteins, LDL
  • OLR1 protein, human
  • Scavenger Receptors, Class E
  • oxidized low density lipoprotein