title: Inhibition of bacterial thioredoxin reductase: an antibiotic mechanism targeting bacteria lacking glutathione.
abstract: Increasing antibiotic resistance makes the identification of new antibacterial principles an urgent task. The thioredoxin system including thioredoxin reductase (TrxR), thioredoxin (Trx), and NADPH plays critical roles in cellular DNA synthesis and defense against oxidative stress. Notably, TrxR is very different in structure and mechanism in mammals and bacteria. Ebselen [2-phenyl-1,2 benzisoselenazol-3(2H)-one], a well-known antioxidant and a substrate for mammalian TrxR and Trx, is rapidly bacteriocidal for methicillin-resistant Staphylococcus aureus by an unknown mechanism. We have discovered that ebselen is a competitive inhibitor of Escherichia coli TrxR with a Ki of 0.52 ± 0.13 μM, through reaction with the active site dithiol of the enzyme. Bacteria lacking glutathione (GSH) and glutaredoxin, in which TrxR and Trx are essential for DNA synthesis, were particularly sensitive to ebselen. In growth-inhibited E. coli strains, Trx1 and Trx2 were oxidized, demonstrating that electron transfer via thioredoxin was blocked. Ebselen and its sulfur analog ebsulfur were bactericidal for GSH-negative pathogens. Ebsulfur inhibited a clinically isolated Helicobacter pylori strain with a minimum inhibitory concentration value as low as 0.39 μg/ml. These results demonstrate that bacterial Trx and TrxR are viable antibacterial drug targets using benzisoselenazol and benzisothiazol derivates.
authors.affiliation: Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Alexios
authors.initials: A
authors.lastname: Vlamis-Gardikas
authors.forename: Karuppasamy
authors.initials: K
authors.lastname: Kandasamy
authors.forename: Rong
authors.initials: R
authors.lastname: Zhao
authors.forename: Tomas N
authors.initials: TN
authors.lastname: Gustafsson
authors.forename: Lars
authors.initials: L
authors.lastname: Engstrand
authors.forename: Sven
authors.initials: S
authors.lastname: Hoffner
authors.forename: Lars
authors.initials: L
authors.lastname: Engman
authors.forename: Arne
authors.initials: A
authors.lastname: Holmgren
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D002478:Cells, Cultured; D004926:Escherichia coli; D005978:Glutathione / Q000172:deficiency / Q000378:metabolism*; D054833:Isoindoles; D009249:NADP / Q000378:metabolism; D016566:Organoselenium Compounds / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013880:Thioredoxin-Disulfide Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D001393:Azoles; D054833:Isoindoles; D016566:Organoselenium Compounds; C042986:ebselen; D013879:Thioredoxins; D009249:NADP; D013880:Thioredoxin-Disulfide Reductase; D005978:Glutathione