title: Cytotoxic interactions of methylene blue with trypanosomatid-specific disulfide reductases and their dithiol products.
abstract: Methylene blue (MB) is known to have trypanocidal activity. We tested the interactions of MB with a number of trypanosomatid-specific molecules of the antioxidant metabolism. At pH 7, trypanothione and other (di)thiols were oxidized to disulfides by the phenothiazine drug. MB inhibited Trypanosoma cruzi trypanothione reductase (TR) (K(i)=1.9 microM), and served as a significant subversive substrate of this enzyme (K(M)=30 microM, k(cat)=4.9s(-1)). With lipoamide dehydrogenase, the second thiol-generating flavoenzyme of T. cruzi, the catalytic efficiency for MB reduction was found to be almost 10(6)M(-1)s(-1). When the system MB-enzyme-molecular oxygen acts as a NAD(P)H-driven redox cycler, a reactive oxygen species, H(2)O(2) or superoxide, is produced in each cycle. Since MB is an affordable, available, and accessible drug it might be tested--alone or in drug combinations--against trypanosomatid-caused diseases of animal and man.
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, INF 504, D-69120 Heidelberg, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Buchholz
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Comini
authors.forename: Dirk
authors.initials: D
authors.lastname: Wissenbach
authors.forename: R Heiner
authors.initials: RH
authors.lastname: Schirmer
authors.forename: R Luise
authors.initials: RL
authors.lastname: Krauth-Siegel
authors.forename: Stephan
authors.initials: S
authors.lastname: Gromer
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002384:Catalysis; D008058:Dihydrolipoamide Dehydrogenase / Q000037:antagonists & inhibitors; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism; D008751:Methylene Blue / Q000493:pharmacokinetics*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D013095:Spermidine / Q000031:analogs & derivatives / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014344:Trypanocidal Agents / Q000493:pharmacokinetics*; D014345:Trypanosoma / Q000201:enzymology*
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D014344:Trypanocidal Agents; C012333:glutathionylspermidine; C044809:trypanothione; D009247:NADH, NADPH Oxidoreductases; C049608:trypanothione reductase; D008058:Dihydrolipoamide Dehydrogenase; D005978:Glutathione; D008751:Methylene Blue; D013095:Spermidine