Effect Of Platycodon Grandiflorum Polysaccharides On PRV Induced Autophagy In PK-15 Cells

Pseudorabies caused by Pseudorabies Virus(PRV)often leads to the failure of sow production and the death of piglets,which seriously endangers the development of pig industry in China.Autophagy is a highly conserved clearance mechanism in mammalian evolution,which plays an important role in virus infection.Many studies have shown that a variety of viruses have evolved survival mechanisms that inhibit autophagy or use autophagy to complete self-replication.Autophagy,as a target of antiviral drug development,has attracted more and more attention.Polysaccharide is a kind of natural polymer and an important component of plants.It is reported that plant polysaccharides have a variety of biological activities,including immune regulation,Hypolipidemia,anti-tumor,antiviral and so on.As a traditional Chinese medicine,Platycodon grandiflorum has the functions of anti-inflammatory,heatclearing,expectorant and lung promoting.Platycodon grandiflorum polysaccharide is an important active component of Platycodon grandiflorum.In this paper,the anti-virus effect of total polysaccharides from Platycodon grandiflorum(PGPS_t)on pseudorabies virus in vitro was studied,and the antiviral mechanism was further discussed.This research mainly includes the following aspects:First of all,we used PK-15 cells to establish infection model.CCK-8 method was used to detect the cell activity damage of PRV at 4h,8h and 12h,and the protective effect of Platycodon grandiflorum polysaccharides(PGPS_t)on PK-15 cells damaged by PRV.After treatment with total polysaccharides of Platycodon grandiflorum,the viability of infected cells increased significantly.PGPS_t(200μg/ml)can effectively inhibit the transcription level of virus genome.ELISA and Western blot were used to detect the effect of PGPS_ton viral protein synthesis.The results showed that PGPS_tcould effectively reduce the synthesis of viral protein.Autophagy test showed that PRV could induce PK-15 cells to form autophagosome,resulting in the accumulation of autophagosome.The autophagosome production of cells treated with Platycodon grandiflorum polysaccharides was significantly reduced.Finally,by detecting the activation of Akt/mTOR signaling pathway which is closely related to the formation of autophagosomes,we found that Platycodon grandiflorum Polysaccharides can inhibit virus induced autophagy by activating Akt/mTOR signaling pathway.Inhibition of mTOR signaling pathway and activation of autophagy reduced the antiviral effect of Platycodon grandiflorum polysaccharides.In conclusion,we found that the PGPS_thad the effect of anti-pseudorabies virus in vitro,and this antiviral effect was achieved by inhibiting virus induced autophagy.Platycodon grandiflorum polysaccharides can activate Akt/mTOR signaling pathway and inhibit virus induced autophagy,and then affect virus replication.