Selenizing astragalus polysaccharide attenuates PCV2 replication promotion caused by oxidative stress through autophagy inhibition via PI3K/AKT activation.

Our previous studies have shown that oxidative stress could promote the porcine circovirus type 2 (PCV2) replication, and astragalus polysaccharide (APS)/selenium could suppress PCV2 replication. However, whether selenizing astragalus polysaccharide (sAPS) provides protection against oxidative stress-induced PCV2 replication promotion and the mechanism involved remain unclear. The present study aimed to explore the mechanism of the PCV2 replication promotion induced by oxidative stress and a novel pharmacotherapeutic approach involving the regulation of autophagy of sAPS. Our results showed that H2O2 promoted PCV2 replication via enhancing autophagy by using 3-methyladenine (3-MA) and autophagy-related gene 5 (ATG5) knockdown. Sodium selenite, APS, the mixture of sodium selenite and APS, and sAPS significantly inhibited H2O2-induced PCV2 replication promotion, respectively. Among these, sAPS exerted maximal inhibitory effect. sAPS could also significantly inhibit autophagy activated by H2O2 and increase the Akt and mTOR phosphorylation. Moreover, LY294002, the specific phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) inhibitor, significantly alleviated the effects of sAPS on autophagy and PCV2 replication. Taken together, we conclude that H2O2 promotes PCV2 replication by inducing autophagy and sAPS attenuates the PCV2 replication promotion through autophagy inhibition via PI3K/AKT activation.