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As an important endogenous cytokine in mammals, interferon-γ (IFNγ) primes and significantly enhances the recognition and response of TLRs to pathogen-associated molecular patterns (PAMPs) in leukocytes. Subsequently, a series of phenomena in the TLR signalling pathway are activated, including increased expression of TLR mRNA, activation of the downstream signalling pathway mediated by myeloid differentiation primary response protein 88 (MyD88)-tumour necrosis factor receptor-associated factor 6 (TRAF6), and nuclear translocation of the nuclear transcription factor NF-κB. There is only one IFNγ isoform in mammals, while many fishes possess two IFNγ genes, IFNγ1 (also called IFNγ-rel) and IFNγ2. The aim of this work was to explore how these two IFNγ isoforms regulate the TLR signalling pathway in green-spotted pufferfish (Tetraodon nigroviridis). Real-time quantitative PCR (RT-qPCR) was performed to detect the expression of TLR1, TLR2, TLR3, TLR5, TLR7, TLR8, TLR9, MyD88, and TFAF6 in T. nigroviridis after stimulation with recombinant IFNγ1 (rIFNγ1) or rIFNγ2. Western blot analysis showed that the expression of MyD88, TFAF6, and NF-κB gradually increased between 0.5 and 8 h after stimulation with rTnIFNγ1. However, following treatment with IFNγ2, the expression of NF-κB at the protein level initially increased rapidly, only to decline swiftly thereafter. Meanwhile, the expression of MyD88 and TFAF6 exhibited a fluctuating pattern of rapid initial decline, subsequent rapid increase, and subsequent rapid decline. Electrophoretic mobility shift assay (EMSA) analysis showed that there was a significant and rapid shift of NF-κB within 5 min soon after rIFNγ2 stimulation, while rIFNγ1 had no significant effect. In summary, we revealed that IFNγ1 and IFNγ2 modulate the innate immune response via TLRs in T. nigroviridis and their regulatory mechanisms are different and multileveled. IFNγ1 and IFNγ2 could be used as immunomodulators to fine-tune the immune response of T. nigroviridis in different ways. [ABSTRACT FROM AUTHOR]

Neuropeptides play crucial roles in regulating various physiological processes in vertebrates. In this study, we identified a novel neuropeptide-encoding gene, nwk , in the genomes of some vertebrate species. The nwk cDNA was subsequently cloned from the brain of zebrafish. The Nwk precursor comprises 88 amino acids, with a putative mature peptide (Nwk-22) of 22 amino acids. Sequence analysis revealed that Nwk-22 is relatively conserved across vertebrate species. Nwk is predominantly expressed in the brain, with positive mRNA cells identified in the TPp and preoptic area. Intraperitoneal injection of Nwk-22 suppressed food intake and downregulated the mRNA expression of the orexigenic factor agouti-related peptide (agrp) in zebrafish. Additionally, a CRISPR/Cas9 approach was used to generate nwk mutant zebrafish. The nwk −/− zebrafish exhibited increased food consumption compared to wild-type controls. Furthermore , Nwk-22a injection in nwk −/− fish also suppressed agrp expression while stimulating the expression of the anorexigenic gene pomca , further supporting the anorexigenic role of Nwk. Taken together, these findings suggest that Nwk functions as an anorexigenic factor, reducing food intake by downregulating orexigenic genes like agrp and upregulating anorexigenic genes like pomc in zebrafish. • Nwk cDNA was firstly cloned in zebrafish. • Nwk-22 peptide injection could suppress the food intake in zebrafish. • Knockout study revealed that Nwk acts as an anorexigenic factor in zebrafish. [ABSTRACT FROM AUTHOR]