ABSTRACT
Objective To investigate the effects of gene silencing of Fas-associated death domain (FADD) with synthetic small interfering RNA (siRNA) on apomorphine-induced contralateral rotation,and the expression of Fas and caspase-8 in rat models of parkinsonism. Methods Sprague-Dawley rats were randomly divided into 5 groups:control group,Parkinson' s disease (PD) group,FADD siRNA group,FADD siRNA positive control group and FADD siRNA negative control group. Synthetic FADD siRNA sequences,siRNA positive sequences or siRNA negative sequences were infused into right substantianigra of midbrain using RNA interference and stereotactic techniques before parkinsonian rat model establishment.Apomorphine-induced contralateral rotations of the rats were observed after the injection.The protein and mRNA expression levels of FADD,Fas and caspase-8 were measured by Western blot and RT-PCR.Results In the control group,no rotation was observed after injecting apomorphine; however,in the rest groups,the number of rats respectively was 12 (12/14),3 (3/13),4 (4/15) and 11 ( 11/14 ) in apomorphine-induced contralateral rotation,which had significant statistical differences ( x2 ＝ 18.56,P =0.000).In parkinsonian substantia nigra,marked increases in the protein and mRNA levels of FADD,Fas and caspase-8 were observed,compared with control group.Furthermore,compared with PD group,FADD protein and mRNA levels were strongly suppressed by administration of FADD siRNA in FADD siRNA group. FADD siRNA administration also resulted in great attenuation of 6-hydroxydopamine-induced increases in expression and activation of caspase-8.However,no decrease in expression of Fas was observed in FADD siRNA group and FADD siRNA positive control group,compared with PD group.Conclusion Our results suggest that death receptor signaling pathway plays a critical role in the pathogenesis of PD.FADD siRNA is effective against this pathway and it may,at least in part,provide a potential neuroprotective effect.