Indoleamine 2,3-dioxygenase participates in the interferon-gamma-induced cell death process in cultured bovine luteal cells

Biol Reprod. 2006 Mar;74(3):552-9. doi: 10.1095/biolreprod.105.042333. Epub 2005 Nov 30.

Abstract

Interferon-gamma (IFNG) induces apoptotic cell death in bovine luteal cells, but the pathway(s) involved in this process are not well defined. Evidence supporting the involvement of an IFNG-inducible enzymatic pathway that degrades tryptophan in IFNG-induced death of bovine luteal cells is presented in this study. The IFNG-inducible enzyme indoleamine 2,3-dioxygenase (INDO) catalyzes the first step in a metabolic pathway that degrades tryptophan. In the first experiment, RT-PCR revealed the presence of INDO mRNA in luteal cells treated with IFNG, but not in untreated cells. To determine whether INDO participates in IFNG-induced death of bovine luteal cells, an experiment was performed to test the effect of 1-methyl-D-tryptophan (1-MT), an inhibitor of INDO, on IFNG-induced DNA fragmentation in luteal cells. Single-cell gel electrophoresis and microscopic image analysis revealed that 1-MT inhibited DNA fragmentation induced by IFNG. To determine whether supplementation of cell cultures with additional tryptophan could also protect luteal cells from IFNG-induced DNA fragmentation, luteal cells were cultured in the presence of IFNG, and L-tryptophan was added to cultures to achieve final concentrations that were 5-, 10-, or 25-fold higher than the concentration of L-tryptophan found in nonsupplemented culture medium. Supplementation of IFNG-treated luteal cell cultures with elevated concentrations of tryptophan also prevented IFNG-induced DNA fragmentation. We conclude that INDO participates in IFNG-induced death of bovine luteal cells, through a mechanism that involves degradation of tryptophan, thereby reducing tryptophan concentrations to a point insufficient to meet luteal cells needs.

Publication types

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

MeSH terms

  • Animals
  • Cattle
  • Cell Death / drug effects
  • Cell Death / physiology*
  • Cells, Cultured
  • DNA Fragmentation / drug effects
  • Female
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Enzymologic / physiology
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / genetics
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / metabolism*
  • Interferon-gamma / pharmacology*
  • Luteal Cells / cytology*
  • Luteal Cells / enzymology*
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tryptophan / pharmacology

Substances

  • Indoleamine-Pyrrole 2,3,-Dioxygenase
  • RNA, Messenger
  • Interferon-gamma
  • Tryptophan