title: Vitamin B-6 restriction reduces the production of hydrogen sulfide and its biomarkers by the transsulfuration pathway in cultured human hepatoma cells.
abstract: BACKGROUND
  Pyridoxal 5'-phosphate (PLP) functions as a coenzyme in many cellular processes including one-carbon metabolism and the interconversion and catabolism of amino acids. PLP-dependent enzymes, cystathionine β-synthase and cystathionine γ-lyase, function in transsulfuration but also have been implicated in the production of the endogenous gaseous signaling molecule hydrogen sulfide (H2S) concurrent with the formation of the biomarkers lanthionine and homolanthionine.
  
  
  OBJECTIVE
  Our objective was to determine if H2S production and concurrent biomarker production is affected by vitamin B-6 restriction in a cell culture model.
  
  
  METHODS
  We used cultured human hepatoma cells and evaluated static intracellular profiles of amino acids and in vivo kinetics of H2S biomarker formation. Cells were cultured for 6 wk in media containing concentrations of pyridoxal that represented severe vitamin B-6 deficiency (15 nmol/L pyridoxal), marginal deficiency (56 nmol/L pyridoxal), adequacy (210 nmol/L pyridoxal), and standard medium formulation providing a supraphysiologic pyridoxal concentration (1800 nmol/L pyridoxal).
  
  
  RESULTS
  Intracellular concentrations of lanthionine and homolanthionine in cells cultured at 15 nmol/L pyridoxal were 50% lower (P < 0.002) and 47% lower (P < 0.0255), respectively, than observed in cells cultured at 1800 nmol/L pyridoxal. Extracellular homocysteine and cysteine were 58% and 46% higher, respectively, in severely deficient cells than in adequate cells (P < 0.002). Fractional synthesis rates of lanthionine (P < 0.01) and homolanthionine (P < 0.006) were lower at 15 and 56 nmol/L pyridoxal than at both higher pyridoxal concentrations. The rate of homocysteine remethylation and the fractional rate of homocysteine production from methionine were not affected by vitamin B-6 restriction. In vitro studies of cell lysates using direct measurement of H2S also had a reduced extent of H2S production in the 2 lower vitamin B-6 conditions.
  
  
  CONCLUSIONS
  In view of the physiologic roles of H2S, these results suggest a mechanism that may be involved in the association between human vitamin B-6 inadequacy and its effects on human health.
authors.affiliation: Department of Food Science and Human Nutrition, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.
authors.forename: Barbara N
authors.initials: BN
authors.lastname: DeRatt
authors.affiliation: Department of Food Science and Human Nutrition, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Ralat
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI; and.
authors.forename: Omer
authors.initials: O
authors.lastname: Kabil
authors.affiliation: Department of Biostatistics, University of Florida, Gainesville, FL.
authors.forename: Yueh-Yun
authors.initials: YY
authors.lastname: Chi
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI; and.
authors.forename: Ruma
authors.initials: R
authors.lastname: Banerjee
authors.affiliation: Department of Food Science and Human Nutrition, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL jfgy@ufl.edu.
authors.forename: Jesse F
authors.initials: JF
authors.lastname: Gregory
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000096:biosynthesis; D015415:Biomarkers / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D003545:Cysteine / Q000096:biosynthesis; D056945:Hep G2 Cells; D006710:Homocysteine / Q000096:biosynthesis; D006801:Humans; D006862:Hydrogen Sulfide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016014:Linear Models; D008113:Liver Neoplasms / Q000378:metabolism; D011732:Pyridoxal Phosphate / Q000378:metabolism; D013440:Sulfides; D025101:Vitamin B 6 / Q000494:pharmacology*; D026681:Vitamin B 6 Deficiency / Q000503:physiopathology*
chemical_list: D015415:Biomarkers; D013440:Sulfides; D006710:Homocysteine; D011732:Pyridoxal Phosphate; D025101:Vitamin B 6; C001520:lanthionine; D003545:Cysteine; D000409:Alanine; D006862:Hydrogen Sulfide