Inhibition of choline kinase as an antiamoebic approach in Entamoeba histolytica infection

Entamoeba histolytica is the parasite responsible for amoebiasis, which can result in amoebic colitis or amoebic liver abscess. Metronidazole has been the conventional treatment for intestinal amoebiasis, but concerns regarding resistance have emerged due to the identification of resistance pathways in E. histolytica. This study investigates a novel anti-amoebic approach targeting the CDP-choline pathway. Inhibition studies were conducted using potential choline kinase (CK) inhibitors to inhibit the EhCK enzyme, and RNA interference was employed to knock down the EhCK gene. K_m and V_max of purified EhCK and hCKa2 proteins were determined by pyruvate kinase-lactate dehydrogenase (PK-LDH) coupled assay. The IC₅₀ values for EhCK and hCKa2 were determined with several commercial CK inhibitors. Selected inhibitors were incubated with E. histolytica trophozoites for 48 hours to determine the EC50 for each inhibitor. Silencing of gene encoding EhCK was carried out using duplex siRNA and the gene expression level was measured by real-time qPCR. Based on the IC₅₀ values, three of the inhibitors, namely CK37, flavopiridol and H-89 were more potent against EhCK than hCKa2. Trophozoites growth inhibition showed that only HDTAB, H-89 and control drug metronidazole could penetrate and induce cell death after 48-hour incubation. siRNA concentration of 10 µg/mL was used for the transfection of positive control GAPDH, EhCK, and non-targeting GFP siRNAs. RNAi experiment concluded with positive control GAPDH downregulated by 99% while the level of EhCK mRNA was downregulated by 47%. In this study, potential inhibitors of EhCK and siRNA have been identified, paving the way for further refinement and testing to enhance their potency against EhCK while sparing hCK. The utilization of these specific inhibitors and siRNA targeting EhCK represents a novel approach to impede the growth of E. histolytica by disrupting its phospholipid synthesis pathway.