In vitro effect of sodium arsenite on Echinococcus granulosus protoscoleces

• We incubated E. granulosus protoscoleces in vitro with NaAsO2 at different concentrations.
• NaAsO2 demonstrated dose- and time-dependent suppression against E. granulosus protoscoleces.
• NaAsO2 could induce ultrastructural damages of E. granulosus protoscoleces.
• Our results clearly demonstrated that NaAsO2 could enhance caspase-3 activity of E. granulosus protoscoleces.

Cystic echinococcosis (CE) caused by the metacestodes of Echinococcus granulosus is an important cosmopolitan zoonosis. Surgery is the main treatment option for CE. Meanwhile, chemotherapy is used as an significant adjunct to surgery. However, the benzimidazole carbamate group and the existing scolicidal agents may not be as effective as hoped. In this study, we aimed to explore the in vitro effect of sodium arsenite (NaAsO2) on Echinococcus granulosus protoscoleces, the causative agents of CE. Protoscoleces of E. granulosus were incubated in vitro with 4, 8, 12, 16, and 20 μM NaAsO2. Viability and changes in morphology were investigated by 0.1% eosin staining. The ultrastructural alterations were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Additionally, caspase-3 activity was measured by colorimetric assay. Obvious protoscolicidal effect was seen with NaAsO2 at concentrations of 16 μM and 20 μM. Protoscolex mortality was 83.24% (16 μM) and 100% (20 μM) after 6 days post-incubation. SEM showed that the primary site of drug damage was the tegument of the protoscoleces. TEM analysis demonstrated that the internal tissues were severely affected and revealed an increase in the number of lipid droplets and vacuoles after treatment with 16 μM NaAsO2. Meanwhile, the caspase-3 activity significantly increased in protoscoleces after 24 h of NaAsO2 incubation compared to the untreated controls. Our study demonstrated the clear in vitro scolicidal effect of NaAsO2 against E. granulosus protoscoleces. However, the in vivo efficacy, specific mechanism, and any possible side effects of NaAsO2 remain to be investigated.

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