title: Genotoxicity of 4-hydroxy-2-nonenal in human colon tumor cells is associated with cellular levels of glutathione and the modulation of glutathione S-transferase A4 expression by butyrate.
abstract: The cellular production of 4-hydroxy-2-nonenal (HNE), a product of endogenous lipid peroxidation, constitutes a genotoxic risk factor for carcinogenesis. Our previous studies have shown that human HT29 colon cells developed resistance toward HNE injury after treatment with butyrate, a diet-associated gut fermentation product. This resistance was attributed to the induction of certain glutathione S-transferases (hGSTP1-1, hGSTM2-2, and hGSTA1-1) and also for the tripeptide glutathione (GSH) synthesizing enzymes. In the present study, we have investigated in HT29 cells whether hGSTA4-4, which has a high substrate specificity for HNE, was also inducible by butyrate and, thus, could contribute to the previously observed chemoresistance. In addition, we investigated if cellular depletion of GSH by L-buthionine-S,R-sulfoximine (BSO) enhances chemosensitivity to HNE injury in HT29 cells. Incubation of HT29 cells with butyrate (2-4 mM) significantly elicited a 1.8 to 3-fold upregulation of steady state hGSTA4 mRNA over 8-24 h after treatment. Moreover, 4 mM butyrate tended to increase hGSTA4-4 protein concentrations. Incubation with 100 microM BSO decreased cellular GSH levels by 77% without significant changes in cell viability. Associated with this was a 2-fold higher level of HNE-induced DNA damage as measured by the comet assay. Collectively, the results of this study and our previous work indicate that the genotoxicity of HNE is highly dependent on cellular GSH status and those GSTs that contribute toward HNE conjugation, including hGSTA4-4. Since HNE contributes to colon carcinogenesis, the favorable modulation of the GSH/GST system by butyrate may contribute to chemoprevention and reduction of the risks.
authors.affiliation: Department of Nutritional Toxicology, Institute for Nutritional Sciences, Friedrich Schiller University, Dornburger Strasse 25, D-07743 Jena, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Knoll
authors.forename: Carola
authors.initials: C
authors.lastname: Ruhe
authors.forename: Selvaraju
authors.initials: S
authors.lastname: Veeriah
authors.forename: Julia
authors.initials: J
authors.lastname: Sauer
authors.forename: Michael
authors.initials: M
authors.lastname: Glei
authors.forename: Evan P
authors.initials: EP
authors.lastname: Gallagher
authors.forename: Beatrice L
authors.initials: BL
authors.lastname: Pool-Zobel
mesh_terms: D000447:Aldehydes / Q000633:toxicity*; D001483:Base Sequence; D020148:Butyric Acid / Q000633:toxicity*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology*; D020552:Comet Assay; D017931:DNA Primers; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D009152:Mutagenicity Tests; D016133:Polymerase Chain Reaction; D013379:Substrate Specificity
chemical_list: D000447:Aldehydes; D017931:DNA Primers; D020148:Butyric Acid; D005982:Glutathione Transferase; D005978:Glutathione; C027576:4-hydroxy-2-nonenal