Classical autophagy-modulating compounds impair viability and alter autophagy gene expression in schistosomula and adult Schistosoma mansoni

Introduction Schistosomiasis is a neglected disease caused by blood flukes affecting millions worldwide and leading to substantial morbidity and economic losses. Despite its global impact, treatment still relies almost exclusively on praziquantel (PZQ); however, the possible emergence of Schistosoma strains with reduced sensitivity to PZQ, alongside PZQ limited efficacy against pre-patent infections, highlights the need for new multi-stage therapeutic approaches. In this context, classical autophagy-modulating compounds may represent valuable tools for elucidating Schistosoma mansoni biology. Methods The effect of rapamycin, a classical autophagy inducer, was evaluated in S. mansoni schistosomula through total ATP quantification and PI/FDA assays. In adult worms, besides ATP quantification, additional phenotypic evaluations included worm pairing, adhesion to culture plates, motility, and egg production. Expression levels of selected autophagy genes were measured by RT-qPCR in both developmental stages. In addition, compounds commonly used to inhibit autophagy in other organisms (bafilomycin A1, chloroquine, spautin-1, and wortmannin) were tested in schistosomula using ATP quantification, and their effects on autophagy genes were evaluated by RT-qPCR in schistosomula and adult worms. Results Rapamycin reduced schistosomula and adult worm viability, presenting with an IC 50 of 14.9 μM and 4.6 μM, respectively, and modulated the expression of several autophagy genes in both parasite stages. Notably, a putative TOR orthologue ( Smp_122910.1 ) was downregulated in male and female worms exposed to a sublethal dose of rapamycin. Although schistosomula ATP levels were not altered by the four inhibitors tested, chloroquine modulated autophagy gene expression. Discussion These findings reveal the antischistosomal potential of rapamycin and identify autophagy genes altered across developmental stages, including Lysosome-associated membrane glycoprotein ( Smp_073400.1 ) and Phospholipase B-like ( Smp_301430.1 ). Stage-specific modulation of the putative TOR orthologue suggests a drug-responsive gene candidate for further functional assays, positioning the tested compounds as promising pharmacological tools for investigating schistosomes biology.