Evaluation of the antimicrobial activity of ebselen: Role of the yeast plasma membrane H⁺‐ATPase

Abstract

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is a selenium-containing antioxidant demonstrating anti-inflammatory and cytoprotective properties in mammalian cells and cytotoxicity in lower organisms. The mechanism underlying the antimicrobial activity of ebselen remains unclear. It has recently been proposed that, in lower organisms like yeast, the plasma membrane H+-ATPase (Pma1p) could serve as a potential target for this synthetic organoselenium compound. Using yeast and bacteria, the present study found ebselen to inhibit microbial growth in a concentration- and time-dependent manner, and yeast and Gram-positive bacteria to be more sensitive to this action (IC50 approximately 2-5 microM) than Gram-negative bacteria (IC50 < 80 microM). Washout experiments and scanning electron microscopic analysis revealed ebselen to possess fungicidal activity. In addition, ebselen was found to inhibit medium acidification by PMA1-proficient haploid yeast in a concentration-dependent manner. Additional studies comparing PMA1 (+/-) and PMA1 (+/+) diploid yeast cells revealed the mutant to be more sensitive to treatment with ebselen than the wild type. Ebselen also inhibited the ATPase activity of Pma1p from S. cerevisiae in a concentration-dependent manner. The interaction of ebselen with the sulfhydryl-containing compounds L-cysteine and reduced glutathione resulted in the complete and partial prevention, respectively, of the inhibition of Pma1p ATPase activity by ebselen. Taken together, these results suggest that the fungicidal action of ebselen is due, at least in part, to interference with both the proton-translocating function and the ATPase activity of the plasma membrane H+-ATPase.

Ebselen is a potent non-competitive inhibitor of extracellular nucleoside diphosphokinase

“…It has been previously reported that ebselen exhibits both glutathione peroxidase activity and antioxidant activity and that ebselen inhibits several redox-sensitive enzymes such as constitutive endothelial nitric oxide synthase, lipoxygenases, nicotinamide adenine dinucleotide phosphate oxidase, and other activities (Table 2 and [29,[38][39][40][41][42][43]). Furthermore, organoselenium compounds in the form of seleninic acids can couple with thiols on catalytically important cysteine residues (e.g., of phosphotyrosine phosphatase), resulting in enzyme inhibition [44].…”

Screening a Commercial Library of Pharmacologically Active Small Molecules against Staphylococcus aureus Biofilms

“…This discrepancy in IC 50 s is likely due to the difference in the strains tested, as different strains may carry different levels of the drug target, which, in this case, is the quorumsensing membrane receptor AgrC. Ebselen, as reported by Chan et al (22), can inhibit S. aureus with an IC 50 of approximately 4.3 M, which compares well with the results of our experiments, which found an IC 50 of 1.3 M. To the best of our knowledge, there are no reports on the antimicrobial activity of verteporfin against either planktonic cultures or preformed biofilms of S. aureus. In our experiments, verteporfin had significant antimicrobial activity with an IC 50 of 1.6 M. Using another photoactive compound unrelated to verteporfin (methylene blue), Tubby et al (23) demonstrated that the photodynamic inactivation of bacteria remains a viable antimicrobial strategy, especially for localized infections.…”

Trans-sulfuration Pathway Seleno-amino Acids Are Mediators of Selenomethionine Toxicity in Saccharomyces cerevisiae*

“…In mammals, they include important regulatory proteins such as the NF-B transcription factor (53), signal transduction kinases such as c-Jun N-terminal kinase (54) and protein kinase C (55), and Na ϩ /K ϩ -ATPases (56). In yeast, ebselen, a synthetic organoselenium compound converted into a selenol in vivo, was shown to inhibit the activity of the plasma membrane H ϩ -ATPase (Pma1p), involved in the regulation of intracellular pH and essential for growth (57). Ebselen was also shown to react with multiple cysteine residues of various other yeast proteins (58).…”