ATG12 is involved in the antiviral immune response in large yellow croaker (Larimichthys crocea)

Proteomics and phosphoproteomics analysis identifies liver immune protein markers in large yellow croakers (Larimichthys crocea) fed a soybean oil-based diet

Dietary fish oil (FO) replacement has led to an inflammatory response in fish species. This study aimed to identify immune-related proteins in the liver tissue of fish fed a FO-based or soybean oil (SO)-based diet. By conducting proteomics and phosphoproteomics analyses, a total of 1601 differentially expressed proteins (DEPs) and 460 differentially abundant phosphorylated proteins (DAPs) were identified, respectively. Enrichment analysis revealed immune-related proteins involved in bacterial infection, pathogen identification, cytokine production, and cell chemotaxis. The mitogen-activated protein kinase (MAPK) pathway exhibited significant alterations in both protein and phosphorylation levels, with several hub DEPs and DAPs associated with MAPK pathway and leukocyte transendothelial migration being notable. In vitro experiments indicated that linolenic acid (LNA), derived from SO, inhibited the expression of NF-E2-related factor 2 (Nrf2), but increased the expression of signaling proteins linked to nuclear factor κB (NF-κB) and MAPK pathways. Transwell assays indicated that treatment of liver cells with LNA promoted macrophage migration. Collectively, the results showed that the SO-based diet upregulated the expression of NF-κB signaling-related proteins and activated the MAPK pathway, promoting immune cell migration. These findings provide novel insights for developing effective solutions to alleviate health problems caused by dietary high levels of SO inclusion.

Evidence of the Autophagic Process during the Fish Immune Response of Skeletal Muscle Cells against Piscirickettsia salmonis

Autophagy is a fundamental cellular process implicated in the health of the cell, acting as a cytoplasmatic quality control machinery by self-eating unfunctional organelles and protein aggregates. In mammals, autophagy can participate in the clearance of intracellular pathogens from the cell, and the activity of the toll-like receptors mediates its activation. However, in fish, the modulation of autophagy by these receptors in the muscle is unknown. This study describes and characterizes autophagic modulation during the immune response of fish muscle cells after a challenge with intracellular pathogen Piscirickettsia salmonis. For this, primary cultures of muscle cells were challenged with P. salmonis, and the expressions of immune markers il-1β, tnfα, il-8, hepcidin, tlr3, tlr9, mhc-I and mhc-II were analyzed through RT-qPCR. The expressions of several genes involved in autophagy (becn1, atg9, atg5, atg12, lc3, gabarap and atg4) were also evaluated with RT-qPCR to understand the autophagic modulation during an immune response. In addition, LC3-II protein content was measured via Western blot. The challenge of trout muscle cells with P. salmonis triggered a concomitant immune response to the activation of the autophagic process, suggesting a close relationship between these two processes.