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Homocysteine modifies extracellular ATP availability in macrophages

Rafael Fernandes Zanin1, Letícia Scussel Bergamin, Elizandra Braganhol

  • 1Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul-UFRGS, Porto Alegre, RS, Brazil; Faculdade de Farmácia, Programa de Pós-Graduação em Biologia Celular e Molecular e Instituto de Toxicologia e Farmacologia, Pontifícia Universidade Católica do Rio Grande do Sul-PUCRS, Porto Alegre, RS, Brazil.

Toxicology in Vitro : an International Journal Published in Association with BIBRA
|September 24, 2013
PubMed

Insights

High homocysteine (Hcy) levels accelerate ATP breakdown in macrophages, leading to adenosine uptake. This process may contribute to inflammation in hyperhomocysteinemia (HHcy) and related vascular diseases.

Area of Science:

  • Biochemistry
  • Immunology
  • Vascular Biology

Background:

  • Hyperhomocysteinemia (HHcy) is linked to cardiovascular diseases and thrombosis.
  • Inflammation, potentially macrophage-mediated, is implicated in HHcy pathogenesis.

Purpose of the Study:

  • To investigate the effects of homocysteine (Hcy) on ATP hydrolysis and its products in murine macrophages.
  • To elucidate the mechanisms behind Hcy's influence on nucleotide metabolism in immune cells.

Main Methods:

  • Murine macrophages were exposed to varying concentrations of Hcy.
  • ATP, ADP, AMP hydrolysis, and inosine levels were measured.
  • NTPDase and ecto-5'-nucleotidase (ecto-5'-NT/CD73) activity and expression were assessed.
  • Reactive oxygen species formation was evaluated.

Main Results:

  • Micromolar Hcy concentrations significantly increased ATP, ADP, and AMP hydrolysis.
  • Extracellular inosine levels decreased in Hcy-treated macrophages.
  • Hcy effects were independent of increased NTPDase/ecto-5'-NT/CD73 expression and reactive oxygen species.
  • Hcy directly modulates nucleotide-degrading enzyme activities.

Conclusions:

  • Hcy promotes rapid extracellular breakdown of ATP, ADP, and AMP to adenosine (ADO).
  • Reduced inosine suggests adenosine uptake, potentially limiting its anti-inflammatory signaling.
  • This mechanism may contribute to the inflammatory complications associated with HHcy.

Keywords:
ADOCADEcto-5′-nucleotidaseFBSHHcyHcyHomocysteineMacrophagesNTPDaseadenosinecoronary artery diseaseectonucleoside triphosphate diphosphohydrolasesfetal bovine serumhomocysteinehyperhomocysteinemia

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