The manganese superoxide dismutase Ala16Val dimorphism modulates iron accumulation in human hepatoma cells

Free Radic Biol Med. 2008 Nov 1;45(9):1308-17. doi: 10.1016/j.freeradbiomed.2008.08.011. Epub 2008 Aug 15.

Abstract

The Ala/16Val dimorphism incorporates alanine (Ala) or valine (Val) in the mitochondrial targeting sequence of manganese superoxide dismutase (MnSOD), modifying MnSOD mitochondrial import and activity. In alcoholic cirrhotic patients, the Ala-MnSOD allele is associated with hepatic iron accumulation and an increased risk of hepatocellular carcinoma. The Ala-MnSOD variant could modulate the expression of proteins involved in iron storage (cytosolic ferritin), uptake (transferrin receptors, TfR-1 and-2), extrusion (hepcidin), and intracellular distribution (frataxin) to trigger hepatic iron accumulation. We therefore assessed the Ala/Val-MnSOD genotype and the hepatic iron score in 162 alcoholic cirrhotic patients. In our cohort, this hepatic iron score increased with the number of Ala-MnSOD alleles. We also transfected Huh7 cells with Ala-MnSOD-or Val-MnSOD-encoding plasmids and assessed cellular iron, MnSOD activity, and diverse mRNAs and proteins. In Huh7 cells, MnSOD activity was higher after Ala-MnSOD transfection than after Val-MnSOD transfection. Additionally, iron supplementation decreased transfected MnSOD proteins and activities. Ala-MnSOD transfection increased the mRNAs and proteins of ferritin, hepcidin, and TfR2, decreased the expression of frataxin, and caused cellular iron accumulation. In contrast, Val-MnSOD transfection had limited effects. In conclusion, the Ala-MnSOD variant favors hepatic iron accumulation by modulating the expression of proteins involved in iron homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / chemistry*
  • Alcoholism / pathology
  • Alleles
  • Carcinoma, Hepatocellular / metabolism*
  • Cell Line
  • Frataxin
  • Genotype
  • Homeostasis
  • Humans
  • Iron / chemistry
  • Iron / metabolism*
  • Iron-Binding Proteins / metabolism
  • Liver Neoplasms / metabolism*
  • Models, Biological
  • Plasmids / metabolism
  • Superoxide Dismutase / metabolism*
  • Valine / chemistry*

Substances

  • Iron-Binding Proteins
  • Iron
  • Superoxide Dismutase
  • Valine
  • Alanine