HO-1-mediated macroautophagy: a mechanism for unregulated iron deposition in aging and degenerating neural tissues

J Neurochem. 2009 May;109(3):776-91. doi: 10.1111/j.1471-4159.2009.06007.x. Epub 2009 Feb 24.

Abstract

Oxidative stress, deposition of non-transferrin iron, and mitochondrial insufficiency occur in the brains of patients with Alzheimer disease (AD) and Parkinson disease (PD). We previously demonstrated that heme oxygenase-1 (HO-1) is up-regulated in AD and PD brain and promotes the accumulation of non-transferrin iron in astroglial mitochondria. Herein, dynamic secondary ion mass spectrometry (SIMS) and other techniques were employed to ascertain (i) the impact of HO-1 over-expression on astroglial mitochondrial morphology in vitro, (ii) the topography of aberrant iron sequestration in astrocytes over-expressing HO-1, and (iii) the role of iron regulatory proteins (IRP) in HO-1-mediated iron deposition. Astroglial hHO-1 over-expression induced cytoplasmic vacuolation, mitochondrial membrane damage, and macroautophagy. HO-1 promoted trapping of redox-active iron and sulfur within many cytopathological profiles without impacting ferroportin, transferrin receptor, ferritin, and IRP2 protein levels or IRP1 activity. Thus, HO-1 activity promotes mitochondrial macroautophagy and sequestration of redox-active iron in astroglia independently of classical iron mobilization pathways. Glial HO-1 may be a rational therapeutic target in AD, PD, and other human CNS conditions characterized by the unregulated deposition of brain iron.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Astrocytes / metabolism*
  • Astrocytes / ultrastructure
  • Autophagy / drug effects
  • Autophagy / physiology*
  • Cells, Cultured
  • Cerebral Cortex / cytology
  • Electrophoretic Mobility Shift Assay / methods
  • Ferric Compounds / metabolism
  • Heme Oxygenase-1 / antagonists & inhibitors
  • Heme Oxygenase-1 / genetics
  • Heme Oxygenase-1 / metabolism*
  • Humans
  • Iron / metabolism*
  • Mesoporphyrins / pharmacology
  • Microscopy, Electron, Transmission / methods
  • Mitochondria / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Spectrometry, Mass, Secondary Ion / methods
  • Subcellular Fractions / drug effects
  • Subcellular Fractions / metabolism
  • Time Factors
  • Transfection / methods

Substances

  • Ferric Compounds
  • Mesoporphyrins
  • mesoporphyrin IX
  • Iron
  • HMOX1 protein, human
  • Heme Oxygenase-1