Hsp90 Inhibitors as New Leads To Target Parasitic Diarrheal Diseases

Abstract

Entamoeba histolytica and Giardia lamblia are anaerobic protozoan parasites that cause amebiasis and giardiasis, two of the most common diarrheal diseases worldwide. Current therapy relies on metronidazole, but resistance has been reported and the drug has significant adverse effects. Therefore, it is critical to search for effective, better-tolerated antiamebic and antigiardial drugs. We synthesized several examples of a recently reported class of Hsp90 inhibitors and evaluated these compounds as potential leads for antiparasitic chemotherapy. Several of these inhibitors showed strong in vitro activity against both E. histolytica and G. lamblia trophozoites. The inhibitors were rescreened to discriminate between amebicidal and giardicidal activity and general cytotoxicity toward a mammalian cell line. No mammalian cytotoxicity was found at >100 M for 48 h for any of the inhibitors. To understand the mechanism of action, a competitive binding assay was performed using the fluorescent ATP analogue bis-ANS (4,4=-dianilino-1,1=-binaphthyl-5,5=-disulfonic acid dipotassium salt) and recombinant E. histolytica Hsp90 preincubated in both the presence and absence of Hsp90 inhibitors. There was significant reduction in fluorescence compared to the level in the control, suggesting that E. histolytica Hsp90 is a selective target. The in vivo efficacy and safety of one Hsp90 inhibitor in a mouse model of amebic colitis and giardiasis was demonstrated by significant inhibition of parasite growth at a single oral dose of 5 mg/kg of body weight/day for 7 days and 10 mg/kg/day for 3 days. Considering the results for in vitro activity and in vivo efficacy, Hsp90 inhibitors represent a promising therapeutic option for amebiasis and giardiasis.

Identification of anisomycin, prodigiosin and obatoclax as compounds with broad-spectrum anti-parasitic activity

“…Giardia lamblia. The compounds were screened against G. lamblia trophozoites following an ATP-bioluminescence based assay for cell growth and survival [77]. For primary screen, parasites were seeded into a 96-well plate at 5,000 trophozoites per well with a final concentration of test compound of 50μM in 100μl media.…”

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). …”

The Critical Role of the Cytoskeleton in the Pathogenesis of Giardia

“…Metronidazole or albendazole alone is generally sufficient for clearance; however, reemergence of infection can occur, possibly due to overuse of this antibiotic [52]. To combat resistance, new therapeutics are being explored that expand 5-nitroimidazole activity [53] or target Hsp90 [54]. Drugs such as Aurofin (an anti-rheumatic) [55] and fumagillin have been found to be effective against Giardia [56].…”