Repurposing FDA-approved sulphonamide carbonic anhydrase inhibitors for treatment of Neisseria gonorrhoeae

Abstract

Neisseria gonorrhoeae is a high-priority pathogen of concern due to the growing prevalence of resistance development against approved antibiotics. Herein, we report the anti-gonococcal activity of ethoxzolamide, the FDA-approved human carbonic anhydrase inhibitor. Ethoxzolamide displayed an MIC 50, against a panel of N. gonorrhoeae isolates, of 0.125 µg/mL, 16-fold more potent than acetazolamide, although both molecules exhibited almost similar potency against the gonococcal carbonic anhydrase enzyme (NgCA) in vitro . Acetazolamide displayed an inhibition constant ( K i ) versus NgCA of 74 nM, while Ethoxzolamide ’ s K i was estimated to 94 nM. Therefore, the increased anti-gonococcal potency of ethoxzolamide was attributed to its increased permeability in N. gonorrhoeae as compared to that of acetazolamide. Both drugs demonstrated bacteriostatic activity against N. gonorrhoeae , exhibited post-antibiotic effects up to 10 hours, and resistance was not observed against both. Taken together, these results indicate that acetazolamide and ethoxzolamide warrant further investigation for translation into effective anti- N. gonorrhoeae agents.

Inhibition studies of bacterial α-carbonic anhydrases with phenols

“…Bacterial CAs were investigated in the last decade for their inhibition with the several types of classical CAIs, among which the sulphonamides and their isosteres, the metal complexing anions and more recently also the coumarins 18–22 . However, no detaled inhibition data with many other classes of inhibitors, including phenols, are available so far in the literature for many of these enzymes, among which NgCAα and VchCAα belong 22 , 24 . The first of this enzyme was recently validated 21 as a potential drug target for developing antibiotics able to reverse or at least to alleviate the extensive drug resistance phenomenon that has emerged for this N. gonorrhoeae 25 .…”

“…Inhibitor and enzyme solutions were preincubated together for 15 min prior to the assay, in order to allow for the formation of the E-I complex. The inhibition constants were obtained by non-linear least-squares methods using Prism 3 and the Cheng-Prusoff equation, as reported previously 21 , 22 , and represent the mean from at least three different determinations. The NgCAα concentration in the assay system was 7.1 nM whereas the VchCAα was 10.3 nM.…”

“…The NgCAα concentration in the assay system was 7.1 nM whereas the VchCAα was 10.3 nM. The used enzymes were recombinant proteins obtained in-house, as described earlier 22 , 24 .…”

“…Such data prompted us to investigate the interactions of a series of simple phenols and some of their derivatives with bacterial CAs which have recently been proposed 20 , 21 as novel drug targets for fighting the emergence of drug resistant bacteria, which no longer respond to clinically used antibiotics 22 . We included in the study NgCAα from Neisseria gonorrhoeae and VchCAα from Vibrio cholerae .…”

The gram-negative bacterium Escherichia coli as a model for testing the effect of carbonic anhydrase inhibition on bacterial growth

“…Ethoxzolamide (EZA), an authorised diuretic and CAI, was shown to kill Helicobacter pylori in vitro , suggesting it could be turned into an anti- H. pylori medication 38 . Finally, acetazolamide inhibited the growth of the Gram-negative bacterium Neisseria gonorrhoeae both in vitro as well as in in vivo mouse models of gonococcal genital tract infection 39 .…”