Amoebicidal Action of Licorice-Derived Compounds: Mechanisms and Effects Against Acanthamoeba castellanii

BackgroundAcanthamoeba is a widely distributed unicellular eukaryotic organism, causing Acanthamoeba keratitis, granulomatous amoebic encephalitis and chronic infectious ulcers. At present, there are no effective drugs available for treating Acanthamoeba infections, highlighting the urgent need for the development of novel anti-Acanthamoeba therapies. PurposeThis study aims to investigate the inhibitory effect of licorice on A. castellanii trophozoites growth and elucidate its molecular mechanisms. MethodsThe effect of licorice on trophozoite viability was assessed employing the CellTiter-Glo assay, while the viability of cells was evaluated via CCK-8 assay. Apoptotic cells were identified through Hoechst 33,342/PI double staining and caspase-3 detection. ROS level was measured via flow cytometry utilising DCFH-DA. Mitochondrial dysfunction was analysed with JC-1 and mtSOX Deep Red staining. RNA sequencing and RT-qPCR analysis were conducted to investigate the potential anti-Acanthamoeba mechanism. ResultsOur results showed that isoliquiritigenin (ISL) and glabridin (GLA) effectively inhibited A. castellaniitrophozoite growth in vitro dose-and time-dependently. ISL and GLA induced several apoptosis features, including Hoechst/PI-positive staining and increased caspase-3 expression. ISL and GLA increased intracellular ROS production, decreased SOD expression and mitochondrial membrane potential and enhanced mitochondrial ROS generation. ISL and GLA effectively prevent host cells from A. castellanii trophozoites invasion. RNA sequencing indicated that ISL may modulate the NAD+ metabolic process, while GLA may influence the sterol metabolic process. ISL reduced the NAD+/NADH ratio, while GLA lowered the levels of 7-dehydrocholesterol in A. castellanii trophozoites. ConclusionThese findings suggest that ISL and GLA may serve as the active components of licorice for treating A. castellanii trophozoites. Our findings suggest that ISL suppresses trophozoites by regulating NAD+ metabolism, while GLA inhibits trophozoites through the regulation of sterol metabolism. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/638758v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1e3ec1borg.highwire.dtl.DTLVardef@a212d2org.highwire.dtl.DTLVardef@81b710org.highwire.dtl.DTLVardef@19b003_HPS_FORMAT_FIGEXP M_FIG C_FIG