Giardial Triosephosphate Isomerase as Possible Target of the Cytotoxic Effect of Omeprazole in Giardia lamblia

Abstract

Giardiasis is highly prevalent in the developing world, and treatment failures with the standard drugs are common. This work deals with the proposal of omeprazole as a novel antigiardial drug, focusing on a giardial glycolytic enzyme used to follow the cytotoxic effect at the molecular level. We used recombinant technology and enzyme inactivation to demonstrate the capacity of omeprazole to inactivate giardial triosephosphate isomerase, with no adverse effects on its human counterpart. To establish the specific target in the enzyme, we used single mutants of every cysteine residue in triosephosphate isomerase. The effect on cellular triosephosphate isomerase was evaluated by following the remnant enzyme activity on trophozoites treated with omeprazole. The interaction of omeprazole with giardial proteins was analyzed by fluorescence spectroscopy. The susceptibility to omeprazole of drug-susceptible and drug-resistant strains of Giardia lamblia was evaluated to demonstrate its potential as a novel antigiardial drug. Our results demonstrate that omeprazole inhibits giardial triosephosphate isomerase in a species-specific manner through interaction with cysteine at position 222. Omeprazole enters the cytoplasmic compartment of the trophozoites and inhibits cellular triosephosphate isomerase activity in a dose-dependent manner. Such inhibition takes place concomitantly with the cytotoxic effect caused by omeprazole on trophozoites. G. lamblia triosephosphate isomerase (GlTIM) is a cytoplasmic protein which can help analyses of how omeprazole works against the proteins of this parasite and in the effort to understand its mechanism of cytotoxicity. Our results demonstrate the mechanism of giardial triosephosphate isomerase inhibition by omeprazole and show that this drug is effective in vitro against drug-resistant and drug-susceptible strains of G. lamblia.

Proteomic and functional analyses reveal pleiotropic action of the anti-tumoral compound NBDHEX in Giardia duodenalis

“…Therefore, an implementation of the available anti-giardial arsenal with more potent, safe and well tolerated drugs are desirable. Novel classes of compounds, some already approved for unrelated human diseases treatment, are effective against Giardia (Tejman-Yarden et al., 2013, Hahn et al., 2013, Kulakova et al., 2014) and potential drug targets have been also identified (Reyes-Vivas et al., 2014, Debnath et al., 2014, Galkin et al., 2014). …”

Characterisation of the in vitro activity of a Nitazoxanide-N-methyl-1H-benzimidazole hybrid molecule against albendazole and nitazoxanide susceptible and resistant strains of Giardia intestinalis and its in vivo giardicidal activity

“…(14) In relation to NTZ, clinical cure was demonstrated in only 50% of nitroimidazole refractory cases treated with NTZ (7) and more recently, a case of treatment failure with NTZ was reported; and NTZ resistance was confirmed in the clinical isolate (N1-INP). (13) Therefore, development of new giardicidal drugs remains urgent, in particular given the disadvantages of the available drugs mentioned above.…”

“…isolates from patients with chronic (IMSS-1090-1) or acute (UNAM-0688-2) giardiasis, (17) an experimentally induced ABZ resistant strain (BRIS/91/HEPU/1411) (18) and a NTZ resistant clinical isolate (N1-INP). (13) All the parasite strains were genotyped as assemblage AI.…”

“…(10) However, parasite resistance to NTZ and ABZ has been experimentally induced (11,12) and it has been reported in clinical isolates. (13,14) Therefore, efforts have been focused on the development of new giardicidal molecules. In this regard, Navarrete-Vazquez et al (15) synthesised a benzologue of NTZ against G. intestinalis (IC 50 = 0.297 µM).…”

Giardiasis and Cryptosporidiosis - Recent Literature with a Focus on Nitazoxanide

“…In addition, there are a number of other approaches that have been used which both eradicate the organism and provide symptomatic relief to the infected patient. In particular, gastric acid-suppression agents, proton pump inhibitors, like omeprazole have been successfully employed in Giardia treatment [97,98]. Specifically, omeprazole enters the cytoplasmic compartment of the trophozoites and inhibits cellular triosephosphate isomerase activity in a dose-dependent manner.…”