Effects of trigonelline inhibition of the Nrf2 transcription factor M vitro on Echmococcus granulosus

The aim of this study was to investigate the impact of trigonelline （TRG） on Echinococcus granulo- sus, and to explore the inhibition impact of nuclear factor erythroid-2-related factor 2 （Nrf2） signal- ing pathway on E. granulosus protoscoleces. Echinococcus granulosus protoscoleces were incubated with various concentrations of TRG, and then Nrf2 protein expression and its localiza- tion in protoscoleces were detected by western blot analysis and immunofluorescence assay, respectively. Reactive oxygen species （ROS） level in protoscoleces was measured using ROS detection kit. Caspase-3 activity was measured using a caspase-3 activity assay kit, and NAD（P）H quinone oxidoreductase （NQO）-I and heme oxygenase （HO）-I activities in protoscoleces were measured by ELISA. The effect of TRG on protoscoleces viability was investigated using 0.1% eosin staining, and ultrastructural alterations in protoscoleces were examined by scanning elec- tron microscopy （SEM）. Immunolocalization experiment clearly showed that Nrf2 protein was pre- dominantly present in cells of protoscoleces. TRG treatment reduced NQO-1 and HO-1 activities in protoscoleces, but could increase ROS level at early time. Protoscoleces could not survive when treated with 250 I~M TRG for 12 days. SEM results showed that TRG-treated protoscoleces pre- sented damage in the protoscoleces region, including hook deformation, lesions, and digitiform protuberance. Nrf2 protein expression was significantly decreased and caspase-3 activity was clearly increased in protoscoleces treated with TRG for 24 and 48 h, respectively, when compared with that in controls （P 〈 0.05）. Our results demonstrated that TRG had scolicidal activity against E. granulosus protoscoleces. Nrf2 protein was mainly expressed in the cells and TRG could effi- ciently inhibit the Nrf2 signaling pathway in E. granulosus.