Evaluation of Human Liver Microtissues for Drug Screening on Schistosoma mansoni Schistosomula

Abstract

Schistosomiasis is a major neglected tropical disease with more than 200 million infections annually. Despite only one drug, praziquantel, being available, the drug pipeline against schistosomiasis is empty, and drug screening tools have limitations. We evaluated the potential of human liver microtissues (hLiMTs) in antischistosomal drug discovery. Because hLiMTs express all human P450 enzymes, they are an excellent tool to evaluate compounds' bioinactivation, bioactivation, and toxicity. To validate the metabolic conversion capacity of hLiMTs, we first quantified (R)- and (S)-praziquantel and the main metabolite trans-OH-praziquantel following incubation with 0.032-50 μM (0.01-15.62 μg/mL) praziquantel for up to 72 h by a validated LC-MS/MS method. We cocultured hLiMTs with newly transformed schistosomula (NTS) and evaluated the antischistosomal activity and cytotoxicity of three prodrugs terfenadine, tamoxifen citrate, and flutamide. HLiMTs converted 300-350 ng (R)-praziquantel within 24 h into trans-OH-praziquantel. We observed changes in the IC₅₀ values for terfenadine, flutamide, and tamoxifen citrate in comparison to the standard NTS assay in vitro. Cytotoxicity was observed at high concentrations of flutamide and tamoxifen citrate. An in vitro platform containing hLiMTs could serve as an advanced drug screening tool for Schistosoma mansoni, providing information on reduced or increased activity and toxicity.

Keywords: Schistosoma mansoni; drug screening; praziquantel; primary human liver microtissue.

Figure 1

Structures of drugs tested in this study: (a) praziquantel, (b) tamoxifen, (c) flutamide, and (d) terfenadine.

Figure 2

(R)-Praziquantel, (S)-praziquantel, and trans-OH-praziquantel quantified by LC-MS/MS following exposure of hLiMTs to praziquantel for a period of 3 days for (a) 2 μM praziquantel, (b) 10 μM praziquantel, (c) 25 μM praziquantel, and (d) 50 μM praziquantel. Error bars represent the standard deviation of three independent experiments. (e) ATP content of hLiMTs after 24, 48, and 72 h of incubation with praziquantel (without NTS); as reference, untreated separate parallel controls were used. The standard deviation is indicated as error bars from triplicate experiments.

Figure 3

Viability of the liver microtissue is shown by ATP quantification after 72 h coincubation with hLiMTs and NTS for (a) tamoxifen citrate, (b) flutamide, and (c) terfenadine. The error bars indicate the standard deviation of triplicate experiments.