title: Oxidative stress decreases extracellular homocysteine concentration in human hepatoma (HepG2) cell cultures.
abstract: BACKGROUND
  Mild hyperhomocysteinemia is associated with premature vascular disease. The mechanism behind the vascular injuries is, however, still unknown. Homocysteine may be catabolized in the trans-sulfuration pathway to cysteine. Cystathionine beta-synthase, which catalyses the first step in the trans-sulfuration pathway is redox-sensitive. We have therefore investigated total extracellular homocysteine turnover in the presence of oxidative stress in human cell lines.
  
  
  METHODS
  The turnover of total extracellular homocysteine in HeLa and hepatoma cell cultures has been investigated in the presence of hydrogen peroxide. Furthermore, the effect of hydrogen peroxide on the removal of high amounts of exogenously added homocysteine was also studied.
  
  
  RESULTS
  Total extracellular homocysteine concentration in hepatoma cell cultures decreased in the presence of hydrogen peroxide, whereas the extracellular homocysteine concentration in HeLa cell cultures was not influenced. There was no significant change of intracellular homocysteine in any type of cell cultures. Furthermore, the presence of hydrogen peroxide did not increase the removal of exogenously added homocysteine.
  
  
  CONCLUSIONS
  The presence of hydrogen peroxide probably increases the activity of the trans-sulfuration pathway in hepatoma cell cultures, which increases the intracellular use of homocysteine and lowers its extracellular release. Consequently this mechanism might tend to lower total plasma homocysteine concentration in oxidative stress.
authors.affiliation: Department of Crop Science, Swedish University of Agricultural Sciences, Alnarp, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Hultberg
authors.forename: Björn
authors.initials: B
authors.lastname: Hultberg
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D018929:Cell Culture Techniques; D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D045604:Extracellular Fluid / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006710:Homocysteine / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress / Q000502:physiology*; D013455:Sulfur / Q000378:metabolism; D013997:Time Factors
chemical_list: D006710:Homocysteine; D013455:Sulfur; D006861:Hydrogen Peroxide