ABSTRACT
BACKGROUND: Schistosomiasis is a tropical parasitic disease treated exclusively with praziquantel (PZQ). However, PZQ has low efficacy against schistosomula and juveniles. In addition, the emergence of PZQ resistance has prompted the search for new drugs. METHODS: This study investigated the effects of pumpkin (Cucurbita pepo)-seed oil (PSO) on Schistosoma mansoni adults, juveniles, and newly formed schistosomula in vitro by exposing the parasites to increasing concentrations of PSO (20, 40, 60, 80, and 100 µl/mL) with variable incubation periods (24, 48, and 72 hours). Dose-response effects of PSO on mortality rate, worm activity, and tegumental changes were studied. Also, effect on DNA were assessed with microsatellite analysis. RESULTS: All tested stages of S. mansoni were susceptible to PSO, which was more effective than PZQ on juvenile worms and schistosomula. Juveniles and schistosomula S. mansoni were more sensitive to the antischistosomal activity of PSO than adult worms. PSO showed evident changes in the integuments of adults, juveniles, and schistosomula. These changes were more evident with increased concentrations. At the genomic level, PSO induced clear qualitative and quantitative changes in the microsatellite loci R95529 and SMD57 of S. mansoni adults and schistosomula. This microsatellite instability is being reported through the current study for S. mansoni in response to PSO for the first time. CONCLUSION: This study suggested that PSO possesses effective antischistosomal activity against various stages of S. mansoni. Further investigations are needed to figure out the mechanism of action of PSO on this parasite.
ABSTRACT
BACKGROUND Praziquantel has been cited as the only drug for treating schistosomiasis. However, concerns over drug resistance have encouraged the search for novel drug leads. The antimalarial drug primaquine possesses interesting anti-schistosmal properties. OBJECTIVES This study is the first to document the potential role of primaquine as a schistosomicide and the ultrastructural changes induced by primaquine on juvenile or adult male worms of Schistosoma mansoni. METHODS Ultrastructural alterations in the tegumental surface of 21-day-old juvenile and adult male worms of S. mansoni were demonstrated following primaquine treatment at different concentrations (2, 5, 10, 15, and 20 µg/mL) and incubation periods (1, 3, 6, 24, and 48 h) in vitro, using both scanning and transmission electron microscopy. FINDINGS At low concentrations (2, 5, and 10 µg/mL) both juvenile and adult male worms were alive after 24 h of incubation, whereas contraction, paralysis, and death of all worms were observed after 24 h of drug exposure at 20 µg/mL. The tegument of juvenile and adult male worms treated with primaquine exhibited erosion, peeling, and sloughing. Furthermore, extensive damage of both tegumental and subtegumental layers included embedded spines, and shrinkage of muscles with vacuoles. The in vitro results confirmed that primaquine has dose-dependent effects with 20 µg/mL as the most effective concentration in a short incubation period. MAIN CONCLUSIONS The schistosomicidal activity of primaquine indicates that this drug possesses moderate in vitro activity against juvenile and adult male worms, since it caused high mortality and tegumental alterations. This study confirmed that the antimalarial drug primaquine possesses anti-schistosomal activity. Further investigation is needed to elucidate its mechanism of action.
