title: TNFalpha enhances the DNA single-strand breakage induced by the short-chain lipid hydroperoxide analogue tert-butylhydroperoxide via ceramide-dependent inhibition of complex III followed by enforced superoxide and hydrogen peroxide formation.
abstract: Treatment of U937 cells with nontoxic concentrations of TNFalpha increased the DNA strand scission induced by a short-chain lipid hydroperoxide analogue, tert-butylhydroperoxide. The following lines of evidence suggest that the enhancing effects of TNFalpha are mediated by inhibition of complex III and by the ensuing formation of superoxides and hydrogen peroxide: (a) the effects of TNFalpha were mimicked by the complex III inhibitor antimycin A; (b) the effects of TNFalpha, or antimycin A, were abolished by the complex I inhibitor rotenone, or by myxothiazol, an agent which inhibits the electron flow from the reduced coenzyme Q to cytochrome c(1) and therefore prevents ubisemiquinone formation; (c) the effects of TNFalpha, or antimycin A, were not observed in respiration-deficient cells; and (d) the effects of TNFalpha, or antimycin A, were sensitive to catalase. The TNFalpha-dependent inhibition of complex III appears to be mediated by ceramide. Three lines of evidence support this inference: (a) a synthetic cell-permeable ceramide analogue reproduced all the effects of TNFalpha, (b) TNFalpha promoted the formation of ceramide via a mechanism sensitive to inhibition of sphingomyelinases by tricyclodecan-9-yl-xanthogenate and imipramine, and (c) the TNFalpha-mediated enhancement of the tert-butylhydroperoxide-induced DNA-damaging response was prevented under conditions in which ceramide formation was inhibited.
authors.affiliation: Istituto di Farmacologia e Farmacognosia, Università degli Studi di Urbino, Urbino, 61029, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Guidarelli
authors.forename: E
authors.initials: E
authors.lastname: Clementi
authors.forename: C
authors.initials: C
authors.lastname: De Nadai
authors.forename: R
authors.initials: R
authors.lastname: Bersacchi
authors.forename: O
authors.initials: O
authors.lastname: Cantoni
mesh_terms: D000968:Antimycin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism*; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000187:drug effects*; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*; D020298:U937 Cells; D020122:tert-Butylhydroperoxide / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D002518:Ceramides; D004277:DNA, Single-Stranded; D004791:Enzyme Inhibitors; C064769:N-acetylsphingosine; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D000968:Antimycin A; D020122:tert-Butylhydroperoxide; D006861:Hydrogen Peroxide; D014450:Electron Transport Complex III; D013110:Sphingosine; D002118:Calcium