Duck Tembusu virus induces incomplete autophagy via the ERK/mTOR and AMPK/mTOR signalling pathways to promote viral replication in neuronal cells

Fowl adenovirus serotype-4 induces autophagy via the AMPK-mTOR signaling pathway during viral invasion of host cells

Fowl adenovirus serotype 4 (FAdV-4) is the primary pathogen responsible for avian hepatitis-hydropericardium syndrome (HHS), which poses a significant threat to the poultry industry. Currently, the routes of FAdV-4 invasion into host cells and the related miRNA expression profiles have been elucidated, but the alterations in intracellular host factors and related signaling pathways during the FAdV-4 invasion phase remains poorly understood. Here, we identified changes in host factors through transcriptome sequencing, revealing 1,135 differentially expressed genes (DEGs) during FAdV-4 invasion, of which 647 were up-regulated and 488 were down-regulated. Analysis of the transcriptome data indicated that signaling pathways such as Wnt signaling pathway, AMPK signaling pathway, and autophagy were closely related to FAdV-4 invasion. Furthermore, we demonstrated that FAdV-4 induced autophagy via the AMPK-mTOR signaling pathway during the viral invasion phase and identified the Penton protein as a key component in inducing this process. Additionally, the activation of autophagy significantly facilitated FAdV-4 invasion, whereas autophagy inhibition markedly impaired viral invasion. Collectively, these findings will advance our knowledge of the pathogenesis of FAdV-4 infection.

Duck Tembusu virus induced mitophagy in vacuolate spermatogenic cells is mediated by PINK1-Parkin pathway

As a significant emerging and re-emerging pathogen in China, the widely spread of Duck Tembusu virus (DTMUV) caused enormous economic losses to poultry industry. On account of DTMUV diseases' main symptoms on haemorrhagic oophoritis, intensive attentions were focused on female reproductive organ. Nevertheless, the DTMUV infection of sperm and testis manifested that testis was an important vector for vertical transmission of DTMUV. In the present study, histopathology, immunofluorescence and transmission electron microscopy (TEM) analysis of DTMUV-infected duck testis revealed that DTMUV infection induced seminiferous epithelium injury via spermatogenic cells vacuolization. After DTMUV infection, the expression of autophagy-related genes and proteins in testis were significantly up-regulated. Further TEM analysis discovered that different stages of autophagic and mitophagy structures were visible in cytoplasm of spermatogenic cells after DTMUV infection. And more notably, the testicular protein expression of PINK1 and Parkin were significantly increased after DTMUV infection. In summary, our study discovered that, after DTMUV infection, PINK1-Parkin pathway mediated mitophagy were activated and then induced spermatogenic cells vacuolization.

Chlorogenic acid alleviates cadmium-induced neuronal injury in chicken cerebral cortex by inhibiting incomplete autophagy mediated by AMPK-ULK1 pathway

Cadmium (Cd) is an environmental pollutant that has neurotoxic properties, which poses serious threats to human health and the development of poultry farming. Chlorogenic acid (CGA) is a dietary polyphenol exhibit various biological activities such as antioxidant, anti-inflammatory, and autophagy regulation. In addition, CGA can penetrate the blood-brain barrier and exert neuroprotective effects. This study explored the mechanism of CGA in alleviating Cd-induced cerebral cortical neuron injury in chickens. The results showed that in vivo, CGA reduced the Cd level and alleviated Cd-induced histopathological and ultrastructural damages in the chicken cerebral cortex. Further research has found that CGA alleviated Cd-induced incomplete autophagy and activation of the AMPK-ULK1 pathway. In vitro, AMPK inhibitors (Compound C) could alleviate Cd-induced incomplete autophagy in chicken cerebral cortical neurons. In addition, CGA alleviated the decreased viability, incomplete autophagy, and activation of the AMPK-ULK1 pathway induced by Cd in chicken cerebral cortical neurons. In summary, CGA can alleviate Cd-induced cerebral cortical neuron injury in chickens, which is related to CGA alleviating Cd-induced incomplete autophagy by inhibiting the AMPK-ULK1 pathway.

Host miRNA and mRNA profiles during in DEF and duck after DHAV-1 infection

DHAV-1 is a highly infectious pathogen that can cause acute hepatitis in ducklings. MicroRNA (miRNA) plays an essential regulatory role in virus response. We characterized and compared miRNA and mRNA expression profiles in duck embryonic fibroblasts (DEF) and the liver of ducklings infected with DHAV-1. DHAV-1 infected DEF was divided into infection group (D group) and blank group (M group), and DHAV-1 infected duckling group was divided into infection group (H group) and blank group (N group). D vs. M have 130 differentially expressed (DE) miRNA (DEM) and 2204 differentially expressed (DE) mRNA (DEG), H vs. N have 72 DEM and 1976 DEG. By the intersection of D vs. M and H vs. N comparisons, 15 upregulated DEM, 5 downregulated DEM, 340 upregulated DEG and 50 downregulated DEG were found with both in vivo and in vitro DHAV-1 infection. In particular, we identified the same DE miRNA target genes and functional annotations of DE mRNA. We enriched with multiple gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, which may have important roles in viral virulence, host immunity, and metabolism. We selected miR-155, which is co-upregulated, and found that miR-155 targets SOCS1 to inhibit DHVA-1 replication.

CDK5-mediated rearrangement of vimentin during Duck Tembusu virus infection inhibits viral replication

Duck Tembusu virus (DTMUV) is a newly emerging pathogen that causes massive economic losses to the poultry industry in China and neighbouring countries. Vimentin, an intermediate filament protein, has been demonstrated to be involved in viral replication during infection. However, the specific role of vimentin in DTMUV replication has not been determined. In this study, we found that overexpression of vimentin in BHK-21 cells can inhibit DTMUV replication. Moreover, DTMUV replication was enhanced after vimentin expression was reduced in BHK-21 cells via small interfering RNA (siRNA). Further research indicated that DTMUV infection had no effect on the transcription or expression of vimentin. However, we found that DTMUV infection induced vimentin rearrangement, and the rearrangement of vimentin was subsequently confirmed to negatively modulate viral replication through the use of a vimentin network disrupting agent. Vimentin rearrangement is closely associated with its phosphorylation. Our experiments revealed that the phosphorylation of vimentin at Ser56 was promoted in the early stage of DTMUV infection. In addition, by inhibiting the phosphorylation of vimentin at Ser56 with a CDK5 inhibitor, vimentin rearrangement was suppressed, and DTMUV replication was significantly enhanced. These results indicated that DTMUV infection induced vimentin phosphorylation and rearrangement through CDK5, resulting in the inhibition of DTMUV replication. In summary, our study reveals a role for vimentin as a negative factor in the process of DTMUV replication, which helps to elucidate the function of cellular proteins in regulating DTMUV replication.

Non-cytopathic bovine viral diarrhea virus (BVDV) inhibits innate immune responses via induction of mitophagy

Bovine viral diarrhea virus (BVDV) belongs to the genus Pestivirus within the family Flaviviridae. Mitophagy plays important roles in virus-host interactions. Here, we provide evidence that non-cytopathic (NCP) BVDV shifts the balance of mitochondrial dynamics toward fission and induces mitophagy to inhibit innate immune responses. Mechanistically, NCP BVDV triggers the translocation of dynamin-related protein (Drp1) to mitochondria and stimulates its phosphorylation at Ser616, leading to mitochondrial fission. In parallel, NCP BVDV-induced complete mitophagy via Parkin-dependent pathway contributes to eliminating damaged mitochondria to inhibit MAVS- and mtDNA-cGAS-mediated innate immunity responses, mtROS-mediated inflammatory responses and apoptosis initiation. Importantly, we demonstrate that the LIR motif of ERNS is essential for mitophagy induction. In conclusion, this study is the first to show that NCP BVDV-induced mitophagy plays a central role in promoting cell survival and inhibiting innate immune responses in vitro.