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Schistosomes infect around 280 million people worldwide.The worms survive in the veins of the final host,where thioredoxin glutathione reductase (TGR) activity helps the parasites to survive in the aerobic environment.In the present study,we synthesized two small interfering RNAs (siRNA S 1 and S2) targeting the Schistosomajaponicum (Sj) TGR gene,and used these to silence the TGR gene.The effects of the siRNAs were evaluated in vitro and in mice infected with schistosomes.The effects of the siRNAson the thioredoxin reductase (TrxR) activity of SjTGR were also evaluated.The effects oftransfection with the siRNAs via the soaking method in vitro were confirmed by flow cytometry.S2 siRNA at a final concentration of 200 nM partially inhibited the exPression of SjTGR at both the transcript and protein levels in vitro.In vivo,S2 siRNA reduced the incidence of worms in schistosomE-infected mice and down:regulated SjTGR transcript levels.TrxR:activity was lower in worms in the S2 siRNA:treated group compared with the control groups.Further analysis revealed that purified recombinant SjTGR could remove oxygen free radicals but not H2O2 directly,which may help to explain the effects of RNA interference.The results of this preliminary study indicate that SjTGR may play an important role in the clearance of oxygen free radicals and protection of S.j aponicum parasites against oxidative damage.