Reprofiled drug targets ancient protozoans: drug discovery for parasitic diarrheal diseases

Abstract

Recently, we developed a novel automated, high throughput screening (HTS) methodology for the anaerobic intestinal parasite Entamoeba histolytica. We validated this HTS platform by screening a chemical library containing US Food and Drug Administration (FDA)-approved drugs and bioactive compounds. We identified an FDA-approved drug, auranofin, as most active against E. histolytica both in vitro and in vivo. Our cell culture and animal studies indicated that thioredoxin reductase, an enzyme involved in reactive oxygen species detoxification, was the target for auranofin in E. histolytica. Here, we discuss the rationale for drug development for three parasites which are major causes of diarrhea worldwide, E. histolytica, Giardia lamblia and Cryptosporidium parvum and extend our current finding of antiparasitic activity of auranofin to Entamoeba cysts, G. lamblia and C. parvum. These studies support the use of HTS assays and reprofiling FDA-approved drugs for new therapy for neglected tropical diseases.

Keywords: Cryptosporidium parvum; Entamoeba; Giardia; auranofin; diarrheal diseases; drug discovery; high throughput screen; orphan drug; protozoan parasites; thioredoxin reductase.

Figure 1. High throughput compound screening protocol for E. histolytica and G. lamblia trophozoites in 96-well microtiter plate.

Figure 2. In vitro efficacy of different concentrations of aurnofin on the growth of C. parvum, as determined by real-time PCR. Bars represent standard errors of the means derived from three replicates.

Figure 3. Clustered display of data from a portion of E. histolytica microarray, indicating downregulated (A) and upregulated transcripts (B) due to auranofin treatment. Microarray hybridizations (A and B) were performed using RNA from DMSO-treated E. histolytica and 1 µM auranofin-treated E. histolytica. Data from related genes in two separate hybridizations (Eh34 and Eh35) were analyzed by use of Acuity software.