AFB1 exposure promotes SIV replication and lung damage via RIG-I- and p38-mediated RETREG1/FAM134B-dependent endoplasmic reticulum autophagy

Aflatoxin B1 (AFB1) contamination is common worldwide and highly harmful to humans and animals. Our previous studies suggested that AFB1 exposure promotes the replication of H1N1 swine influenza virus (SIV). However, its mechanism is not clear. Here, TCID₅₀, qRT-PCR, and WB assays were used to detect SIV replication, after which proteomic detection was used to screen key proteins and pathways. Thirty piglets were subsequently randomly divided into 6 groups. The low-pathogenicity SIV was inoculated to establish a piglet model of SIV infection. Different doses of AFB1 were administered daily to SIV-infected piglets for 14 d. The in vitro results revealed that 0.02-0.04 μg/mL AFB1 markedly promoted SIV replication. Proteomic analysis revealed that reticulophagy regulator 1 (RETREG1/FAM134B) and p38 signaling were markedly upregulated, whereas RIG-I signaling was significantly downregulated. The above results were confirmed by qRT-PCR and WB assays. Transmission electron microscopy was used to further prove that AFB1 promoted endoplasmic reticulum autophagy (ER-phagy) in SIV-infected PAMs. RIG-I activator and p38 inhibitor reversed the upregulation of RETREG1 and AFB1-promoted SIV replication, and RETREG1 inhibitor reversed the AFB1-promoted SIV replication. In vivo experiments confirmed that AFB1 upregulated RETREG1 and p38, downregulated RIG-I, and promoted SIV replication and lung damage. Taken together, our results reveal that AFB1 promotes SIV replication and lung damage via RIG-I- and p38-mediated RETREG1/FAM134B-dependent ER-phagy and suggest the therapeutic potential of RETREG1-, RIG-I-, and p38-related drugs for influenza. Our findings also provide insights into why the occurrence of other infectious diseases is increasing.