Bacterial thioredoxin reductase inhibitors and methods for use thereof

Abstract

The mechanism of action of Ebselen differentiates between bacterial and mammalian thioredoxin reductase (TrxR). It displays fast oxidation of mammalian Trx and via the NADPH-TrxR catalyzed turnover of ebselen selenol with hydrogen peroxide, and therefore are mammalian antioxidants. Ebselen, and its diselenide, are strong competitive inhibitors of E. coli TrxR with K_i of 0.14 μM and 0.46 μM, respectively. E. coli mutants lacking glutathione reductase or glutathione were much more sensitive to inhibition by ebselen. Since either glutaredoxin or thioredoxin systems are electron donors to ribonucleotide reductase, ebselen targets primarily glutathione and glutaredoxin-negative bacteria, a class which includes major pathogens. Ebselen, and similar compounds are therefore useful as antibacterial agents, even for multiresistant strains. Two major pathogenic bacteria, which previously had not been known to be sensitive to ebselen, Mycobacterium tuberculosis (tuberculosis) and Helicobacter pylori (stomach ulcer and cancer), were shown to be excellent targets. Helicobacter pylori was also sensitive to ebsulfur.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the field of biologically active selenium and sulfur compounds, and more particularly to ebselen (or ebsulfur), its diselenide analog, and more generally to benzisoselenazole-3(2H)-one and derivatives thereof, salts thereof, pharmaceutical formulations thereof, and methods of use thereof.BACKGROUND OF THE INVENTION[0002]The thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH are together called the thioredoxin system, which serves as a hydrogen donor for ribonucleotide reductase and has a general powerful disulfide reductase activity (4, 5, 11, 13). The thioredoxin system is present in cells and in all forms of life (4, 5, 11, 13). Thioredoxin reductase (TrxR) is a dimeric FAD containing enzyme that catalyzes the reduction of its main protein substrate oxidized thioredoxin, to reduced thioredoxin at the expense of NADPH. The enzyme mechanism involves the transfer of reducing equivalents of NADPH to a redox active si...

AI Technical Summary

Benefits of technology

[0019]Different classes of benzisoselenazol-3(2H)-one compounds such as N-aryl (EbSe 7-10), N-unsubstituted (EbSe 6), N-alkyl (EbSe 2-4), N-2-pyridyl (EbSe 11 & 12) and N-4-pyridyl (EbSe 13) substituted benzisoselenazol-3(2H)-ones as well as bis-benzisoselenazol-3(2H)-ones (EbSe 14-16) were synthesized. Their inhibition effect on E. coli thioredoxin reductase (TrxR) was studied by thioredoxin dependent DTNB disulfide reduction assay in vitro. Detailed kinetic studies show that bisbenzisoselenazol-3(2H)-ones compounds (EbSe 14-16) inhibit TrxR at nanomolar concentrations while compounds EbSe 7-10, 12-13, 2-4 and parent ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one (EbSe 6) inhibit at micromolar concentrations. Other compounds did not inhibit E. coli TrxR. Tryptophan fluorescence measurements were carried out to follow the reaction of these compounds with reduced thioredoxin. Like ebselen, these compounds also rapidly oxidized reduced thioredoxin.

Problems solved by technology

The presently used drugs have limitations and resistant bacterial infections is an increasing problem as evident by development of vancomycin and methicillin resistant bacteria.

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