Lectin-like oxidized low-density lipoprotein receptor-1-mediated autophagy in human granulosa cells as an alternative of programmed cell death

Endocrinology. 2006 Aug;147(8):3851-60. doi: 10.1210/en.2006-0088. Epub 2006 May 11.

Abstract

The LOX-1 receptor, identified on endothelial cells, mediates the uptake of oxidized low-density lipoprotein (oxLDL). The oxLDL-dependent LOX-1 activation causes endothelial cell apoptosis. We here investigated the presence of LOX-1 in granulosa cells from patients under in vitro fertilization therapy. We were interested in the oxLDL-dependent LOX-1 receptor biology, in particular in the induction of apoptosis. In the human ovary, LOX-1 was localized in regressing antral follicles. In granulosa cell cultures, oxLDL-induced mRNA expression of LOX-1 in a time- and dose-dependent manner. The LOX-1 inhibitors (anti-LOX-1 antibody and kappa-carrageenan) abrogated the up-regulation of LOX-1. The oxLDL (100 microg/ml) treatment caused the autophagy form of programmed cell death: 1) reorganization of the actin cytoskeleton at the 6-h time point; 2) uptake of YO-PRO, a marker for the early step of programmed cell death, before propidium iodide staining to signify necrosis; 3) absence of apoptotic bodies and cleaved caspase-3; 4) abundant vacuole formation at the ultrastructural level; and 5) decrease of the autophagosome marker protein MAP LC3-I at the 6-h time point indicative of autophagosome formation. We conclude that follicular atresia is not under the exclusive control of apoptosis. The LOX-1-dependent autophagy represents an alternate form of programmed cell death. Obese women with high blood levels of oxLDL may display an increased rate of autophagic granulosa cell death.

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Autophagy / drug effects
  • Autophagy / physiology*
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • Female
  • Follicular Atresia / metabolism
  • Granulosa Cells / cytology*
  • Granulosa Cells / metabolism*
  • Humans
  • Immunohistochemistry
  • Infertility, Female / metabolism
  • Infertility, Female / pathology
  • Lipoproteins, LDL / metabolism*
  • Obesity / metabolism
  • Obesity / pathology
  • Reverse Transcriptase Polymerase Chain Reaction
  • Scavenger Receptors, Class E / genetics
  • Scavenger Receptors, Class E / metabolism*
  • Staurosporine / pharmacology
  • Up-Regulation / physiology

Substances

  • Enzyme Inhibitors
  • Lipoproteins, LDL
  • OLR1 protein, human
  • Scavenger Receptors, Class E
  • oxidized low density lipoprotein
  • Staurosporine