TIR Domain-Containing Adaptor-Inducing Interferon-β (TRIF) Participates in Antiviral Immune Responses and Hepatic Lipogenesis of Large Yellow Croaker (Larimichthys Crocea)

Monophosphoryl lipid A as a co-adjuvant in methicillin-resistant Staphylococcus aureus vaccine development: improvement of immune responses in a mouse model of infection

To increase the effectiveness of methicillin-resistant Staphylococcus aureus vaccines (MRSA), a new generation of immune system stimulating adjuvants is necessary, along with other adjuvants. In some vaccines, monophosphoryl lipid A (MPLA) as a toll-like receptor 4 agonist is currently used as an adjuvant or co-adjuvant. MPLA could increase the immune response and vaccine immunogenicity. The current investigation assessed the immunogenicity and anti-MRSA efficacy of recombinant autolysin formulated in MPLA and Alum as co-adjuvant/adjuvant. r-Autolysin was expressed and purified by Ni-NTA affinity chromatography and characterized by SDS-PAGE. Then, the vaccine candidate formulation in MPLAs and Alum was prepared. To investigate the immunogenic responses, total IgG, isotype (IgG1 and IgG2a) levels, and cytokines (IL-4, IL-12, TNF-α, and IFN-γ) profiles were evaluated by ELISA. Also, the bacterial burden in internal organs, opsonophagocytosis, survival rate, and pathobiology changes was compared among the groups. Results demonstrated that mice immunized with the r-Autolysin + Alum + MPLA Synthetic and r-Autolysin + Alum + MPLA Biologic led to increased levels of opsonic antibodies, IgG1, IgG2a isotype as well as increased levels of cytokines profiles, as compared with other experimental groups. More importantly, mice immunized with MPLA and r-Autolysin exhibited a decrease in mortality and bacterial burden, as compared with the control group. The highest level of survival was seen in the r-Autolysin + Alum + MPLA Synthetic group. We concluded that both MPLA forms, synthetic and biological, are reliable candidates for immune response improvement against MRSA infection.

Transcription factor EB (TFEB) participates in antiviral immune responses independent of mTORC1 in macrophage of large yellow croaker (Larimichthys crocea)

Transcription factor EB (TFEB) plays an integral role in the production of proinflammatory cytokines and chemokines in response to pathogen stimulation in mammals. However, the role of TFEB in antiviral immune responses and the potential regulatory mechanisms in fish remain poorly understood. Here, we cloned and characterized Larimichthys crocea TFEB (LcTFEB) with 524 amino acids and a typical basic helix-loop-helix-leucine zipper domain. LcTFEB could translocate into the nucleus upon starvation and had a comparatively high expression in immune tissues. Similar to the expression of antiviral immune genes, the transcriptional expression and activity of LcTFEB showed a trend of increasing and then decreasing with the prolongation of stimulation. Inhibition of LcTFEB using siRNA dramatically increased the polyinosinic-polycytidylic acid (poly (I:C))-induced interferon response and pro-inflammatory cytokines mRNA expression levels, whereas pharmacological activation and overexpression of LcTFEB exhibited the reverse effects. Mechanically, LcTFEB might promote the expression of IFNh as negative feedback to limit the virus-induced inflammatory responses. Notably, although inhibition of mTORC1 exacerbated poly (I:C)-triggered inflammatory responses, the effects of LcTFEB were independent of mTORC1. Overall, this study revealed an unidentified critical role of LcTFEB in the regulation of antiviral immune responses and promoted the understanding of TFEB in the antiviral immunity of fish macrophages.

Non-coding RNAs targeting NF-κB pathways in aquatic animals: A review

Nuclear factor-kappa B (NF-κB) pathways have a close relationship with many diseases, especially in terms of the regulation of inflammation and the immune response. Non-coding RNAs (ncRNAs) are a heterogeneous subset of endogenous RNAs that directly affect cellular function in the absence of proteins or peptide products; these include microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), etc. Studies on the roles of ncRNAs in targeting the NF-κB pathways in aquatic animals are scarce. A few research studies have confirmed detailed regulatory mechanisms among ncRNAs and the NF-κB pathways in aquatic animals. This comprehensive review is presented concerning ncRNAs targeting the NF-κB pathway in aquatic animals and provides new insights into NF-κB pathways regulatory mechanisms of aquatic animals. The review discusses new possibilities for developing non-coding-RNA-based antiviral applications in fisheries.

Farnesoid X receptor regulates PI3K/AKT/mTOR signaling pathway, lipid metabolism, and immune response in hybrid grouper

Some diseases related to lipid metabolism increase yearly in cultured fish, and the farnesoid X receptor (FXR) is a nuclear protein that plays a key role in inflammatory responses and lipid metabolism. However, the roles of FXR in hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) remain poorly understood. The main objective of this study was to explore the roles of hepatic FXR in triggering the immune response and the potential functions of FXR in regulating the lipid metabolism. In the present study, the full-length sequence of fxr from hybrid grouper was cloned and characterized for the first time. Upon the Vibrio parahaemolyticus stimulation, the transcriptional level of fxr was rapidly elevated in the head kidney tissue in the early stage of infection. In vivo and vitro, activation of FXR by obeticholic acid (OA) significantly increased the concentrations and mRNA levels of hepatic inflammatory cytokines. These effects were inversed when FXR was inhibited by guggulsterone (GU). Moreover, the activation of FXR to suppress the PI₃K/AKT/mTOR signaling pathway improves hepatic lipid metabolism and reduces hepatic lipid accumulation in vivo and vitro. In addition, the inhibition of FXR activated the PI₃K/AKT/mTOR pathway, decreased the lipolysis and increased the lipogenesis, and subsequently increased the lipid accumulation in fish. These results revealed the positive roles of FXR in triggering immune responses and improving lipid metabolism and accumulation in hybrid grouper.

Docosahexaenoic Acid Ameliorates the Toll-Like Receptor 22-Triggered Inflammation in Fish by Disrupting Lipid Raft Formation

BACKGROUND

Although dietary DHA alleviates Toll-like receptor (TLR)-associated chronic inflammation in fish, the underlying mechanism is not well understood.

OBJECTIVES

This study aimed to explore the role of Tlr22 in the innate immunity of large yellow croaker and investigate the anti-inflammatory effects of DHA on Tlr22-triggered inflammation.

METHODS

Head kidney-derived macrophages of croaker and HEK293T cells were or were not pretreated with 100 μM DHA for 10 h prior to polyinosinic-polycytidylic acid (poly I:C) stimulation. We executed qRT-PCR, immunoblotting, and lipidomic analysis to examine the impact of DHA on Tlr22-triggered inflammation and membrane lipid composition. In vivo, croakers (12.03 ± 0.05 g) were fed diets containing 0.2% [control (Ctrl)], 0.8%, and 1.6% DHA for 8 wk before injection with poly I:C. Inflammatory genes expression and rafts-related lipids and protein expression were measured in the head kidney. Data were analyzed by ANOVA or Student t test.

RESULTS

The activation of Tlr22 by poly I:C induced inflammation, and DHA diminished Tlr22-targeted inflammatory gene expression by 56-73% (P ≤ 0.05). DHA reduced membrane sphingomyelin (SM) and SFA-containing phosphatidylcholine (SFA-PC) contents, as well as lipid raft marker caveolin 1 amounts. Furthermore, lipid raft disruption suppressed Tlr22-induced Nf-κb and interferon h activation and p65 nuclear translocation. In vivo, expression of Tlr22 target inflammatory genes was 32-64% lower in the 1.6% DHA group than in the Ctrl group upon poly I:C injection (P ≤ 0.05). Also, the 1.6% DHA group showed a reduction in membrane SM and SFA-PC contents, accompanied by a decrease in caveolin 1 amounts, compared with the Ctrl group.

CONCLUSIONS

The activation of Tlr22 signaling depends on lipid rafts, and DHA ameliorates the Tlr22-triggered inflammation in both head kidney and head kidney-derived macrophages of croaker partially by altering membrane SMs and SFA-PCs that are required for lipid raft organization.

Recent advances in conventional and unconventional vesicular secretion pathways in the tumor microenvironment

All cells in the changing tumor microenvironment (TME) need a class of checkpoints to regulate the balance among exocytosis, endocytosis, recycling and degradation. The vesicular trafficking and secretion pathways regulated by the small Rab GTPases and their effectors convey cell growth and migration signals and function as meditators of intercellular communication and molecular transfer. Recent advances suggest that Rab proteins govern conventional and unconventional vesicular secretion pathways by trafficking widely diverse cargoes and substrates in remodeling TME. The mechanisms underlying the regulation of conventional and unconventional vesicular secretion pathways, their action modes and impacts on the cancer and stromal cells have been the focus of much attention for the past two decades. In this review, we discuss the current understanding of vesicular secretion pathways in TME. We begin with an overview of the structure, regulation, substrate recognition and subcellular localization of vesicular secretion pathways. We then systematically discuss how the three fundamental vesicular secretion processes respond to extracellular cues in TME. These processes are the conventional protein secretion via the endoplasmic reticulum-Golgi apparatus route and two types of unconventional protein secretion via extracellular vesicles and secretory autophagy. The latest advances and future directions in vesicular secretion-involved interplays between tumor cells, stromal cell and host immunity are also described.

Development and Validation of a Prognostic Classifier Based on Lipid Metabolism-Related Genes for Breast Cancer

Background

The changes of lipid metabolism have been implicated in the development of many tumors, but its role in breast invasive carcinoma (BRCA) remains to be fully established. Here, we attempted to ascertain the prognostic value of lipid metabolism-related genes in BRCA.

Methods

We obtained RNA expression data and clinical information for BRCA and normal samples from public databases and downloaded a lipid metabolism-related gene set. Ingenuity Pathway Analysis (IPA) was applied to identify the potential pathways and functions of Differentially Expressed Genes (DEGs) related to lipid metabolism. Subsequently, univariate and multivariate Cox regression analyses were utilized to construct the prognostic gene signature. Functional enrichment analysis of prognostic genes was achieved by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Kaplan-Meier analysis, Receiver Operating Characteristic (ROC) curves, clinical follow-up results were employed to assess the prognostic potency. Potential compounds targeting prognostic genes were screened by Connectivity Map (CMap) database and a prognostic gene-drug interaction network was constructed using Comparative Toxicogenomics Database (CTD). Furthermore, we separately validated the selected marker genes in BRCA samples and human breast cancer cell lines (MCF-7, MDA-MB-231).

Results

IPA and functional enrichment analysis demonstrated that the 162 lipid metabolism-related DEGs we obtained were involved in many lipid metabolism and BRCA pathological signatures. The prognostic classifier we constructed comprising SDC1 and SORBS1 can serve as an independent prognostic marker for BRCA. CMap filtered 37 potential compounds against prognostic genes, of which 16 compounds could target both two prognostic genes were identified by CTD. The functions of the two prognostic genes in breast cancer cells were verified by cell function experiments.

Conclusion

Within this study, we identified a novel prognostic classifier based on two lipid metabolism-related genes: SDC1 and SORBS1. This result highlighted a new perspective on the metabolic exploration of BRCA.

Acetyl-CoA derived from hepatic mitochondrial fatty acid β-oxidation aggravates inflammation by enhancing p65 acetylation

Acetylation coordinates many biological processes to ensure cells respond appropriately to nutrients. However, how acetylation regulates lipid surplus-induced inflammation remains poorly understood. Here, we found that a high-fat diet (HFD) enhanced mitochondrial fatty acid β-oxidation, which enhanced acetyl-CoA levels in the liver of the large yellow croaker. The HFD activated ACLY to govern the "citrate transport" to transfer acetyl-CoA from the mitochondria to the nucleus. Elevated acetyl-CoA activated CBP to increase p65 acetylation and then aggravated inflammation. SIRT1 was deactivated with a decline in NAD+/NADH, which further aggravated inflammation. Therefore, acetylation-dependent regulation of transcription factor activity is an adaptation to proinflammatory stimuli under nutrient stress, which was also confirmed in AML12 hepatocytes. In vitro octanoate stimulation further verified that acetyl-CoA derived from fatty acid β-oxidation mediated acetylation homeostasis in the nucleus. The broad therapeutic prospects of intermediate metabolites and acetyltransferases/deacetylases might provide critical insights for the treatment of metabolic diseases in vertebrates.

Molecular identification of peptidoglycan recognition protein 5 and its functional characterization in innate immunity of large yellow croaker, Larimichthys crocea

Fish peptidoglycan recognition proteins (PGRPs) play important roles in microbial recognition, and bacterial elimination. In the present study, a short-type PGRP from large yellow croaker, LcPGRP5 was cloned and its functions were characterized. LcPGRP5 gene encodes a protein containing conserved PGRP domain, but no signal peptide. Phylogenetic analysis shows that LcPGRP5 is clustered with other short PGRPs identified in other teleosts. LcPGRP5 is constitutively expressed in all tissues examined, with the highest expression being detected in the head kidney. Recombinant LcPGRP5 protein features amidase activity and bactericidal activity. Notably, LcPGRP5 could enhance the phagocytosis of the bacteria by large yellow croaker macrophage, with higher phagocytic capacity being observed in Staphylococcus aureus compared to Escherichia coli. Moreover, overexpression of LcPGRP5 suppresses pro-inflammatory effects elicited by bacterial exposure in the macrophage cell line. Overall, the present results clearly indicate the important roles of LcPGRP5 played in the innate immune responses against bacterial infection.

Cyprinus carpio TRIF Participates in the Innate Immune Response by Inducing NF-κB and IFN Activation and Promoting Apoptosis

TRIF, an important adaptor downstream of Toll-like receptor signaling, plays a critical role in the innate immune response. In this study, the full-length coding sequence of TRIF from common carp (Cyprinus carpio L.) was cloned and characterized. Bioinformatics analysis showed that common carp TRIF exhibited a conserved TIR domain and had the closest relationship with grass carp TRIF. Expression analysis revealed that TRIF was constitutively expressed in the examined tissues of common carp, with the highest expression in the spleen and the lowest expression in the head kidney, and could be upregulated under Aeromonas hydrophila and poly(I:C) stimulation in vivo and under poly(I:C), LPS, PGN, flagellin, and Pam3CSK4 stimulation in vitro. Laser confocal microscopy showed that common carp TRIF colocalized with the Golgi apparatus. A luciferase reporter assay showed that carp TRIF elicited the activity of ifn-1 and nf-κb through the C-terminal domain. Additionally, crystal violet staining and qPCR assays revealed that carp TRIF inhibited the replication of SVCV in epithelioma papulosum cyprini (EPC) cells. Then, the signaling downstream of carp TRIF was investigated. Coimmunoprecipitation and Western blotting analysis demonstrated that carp TRIF interacted with TBK1 and augmented the expression of TRAF6 and phosphorylation of TBK1. Overexpression of carp TRIF significantly enhanced the expression of interferon-stimulated genes and inflammatory cytokines. Furthermore, flow cytometric (FCM) analysis suggested that carp TRIF induced apoptosis through the activation of caspase-8. In summary, our study indicated that TRIF plays an essential role in the innate immune responses of common carp against bacterial and viral infection.

TRIF-mediated antiviral signaling is differentially regulated by TRAF2 and TRAF6 in black carp

TRIF is an antiviral adaptor downstream of Toll-like receptors, the roles of teleost TRIF and their regulation remain largely unknown. In this study, a TRIF homologue (bcTRIF) of black carp (Mylopharyngodon piceus) has been cloned, and the transcription of bcTRIF in vivo and ex vivo increased in response to different stimuli. Overexpressed bcTRIF induced the transcription of interferon promoter in the EPC cells and enhanced protection of cells against infection of spring viremia of carp virus (SVCV). The previous study has identified that black carp TRAF2 (bcTRAF2) and TRAF6 (bcTRAF6) functioned positively in RIG-I/MAVS signaling. When co-expressed with bcTRAF2, bcTRIF-induced the transcription of interferon promoter in EPC cells was decreased, and the antiviral activity of bcTRIF was dampened accordingly. On the contrary, co-expressed bcTRAF6 enhanced both bcTRIF-mediated interferon promoter transcription and antiviral activity. The subsequent co-immunoprecipitation identified the interaction between bcTRAF2/6 and bcTRIF. Thus, bcTRIF-mediated antiviral signaling is up-regulated by bcTRAF6 and down-regulated by bcTRAF2.

Regulation of Free Fatty Acid Receptor 4 on Inflammatory Gene Induced by LPS in Large Yellow Croaker (Larimichthys crocea)

Free fatty acid receptor 4 (FFAR4) plays a key role in regulating the inflammatory response in mammals. The present study aimed to investigate the function of large yellow croaker FFAR4 on inflammation. In the present study, ffar4 was widely expressed in 10 tissues of large yellow croaker including gill, head kidney and spleen. Further studies showed that treatment of head kidney macrophages with agonists (TUG891 or GSK137647A) or overexpression of ffar4 reduced the mRNA expression of pro-inflammatory genes induced by LPS, and increased the expression of pparγ. Treatment of macrophages with antagonist AH7614 increased the mRNA expression of pro-inflammatory genes induced by LPS, and decreased the mRNA expression of pparγ. In order to verify the immunomodulatory effect of PPARγ, PPARγ was overexpressed in macrophages which significantly reduced the mRNA expression of pro-inflammatory genes il6, il1β, il8, tnfα and cox2. Moreover, results of dual-luciferase assays showed that PPARγ downregulated the transcriptional activity of il6 and il1β promoters. In conclusion, FFAR4 showed anti-inflammatory effects on LPS-induced inflammation in large yellow croaker.

Lipotoxicity reduces DDX58/Rig-1 expression and activity leading to impaired autophagy and cell death

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease globally. NAFLD is a consequence of fat accumulation in the liver leading to lipotoxicity. Increasing evidence has demonstrated the critical role of autophagy in NAFLD. This study uncovers the unexpected role of immune surveillance protein DDX58/Rig-1 (DExD/H box helicase 58) in activating macroautophagy/autophagy and protecting from lipotoxicity associated with NAFLD. Here we show for the first time that DDX58 protein is significantly reduced in nonalcoholic steatohepatitis (NASH) mouse model, an aggressive form of NAFLD characterized by inflammation and fibrosis of the liver. In addition to decreased expression of DDX58, we found that DDX58 activity can be attenuated by treatments with palmitic acid (PA), a saturated fatty acid. To investigate whether PA inhibition of DDX58 is harmful to the cell, we characterized DDX58 function in hepatocytes when exposed to high doses of PA in the presence and/or absence of DDX58. We show that siRNA knockdown of DDX58 promotes apoptosis. Importantly, we show that stable overexpression of DDX58 is protective against toxic levels of PA and stimulates autophagy. This study begins to demonstrate the regulation of the autophagy receptor protein SQSTM1/p62 through DDX58. DDX58 expression directly influences SQSTM1 mRNA and protein levels. This work proposes a model in which activating DDX58 increases an autophagic response and this aids in clearing toxic lipid inclusion bodies, which leads to inflammation and apoptosis. Activating a DDX58-induced autophagy response may be a strategy for treating NAFLD.Abbreviations:5'pppdsRNA: 5' triphosphate double-stranded RNA; CDAHFD: choline-deficient, L-amino acid defined high-fat diet; CEBPB: CCAAT/enhancer binding protein (C/EBP), beta; CQ: chloroquine; DDX58/retinoic acid inducible gene 1/Rig-1: DExD/H box helicase 58; h: hours; IFIH1/MDA5: interferon induced with helicase C domain 1; IFNB/IFN-β: interferon beta 1, fibroblast; KO: knockout; MAVS: mitochondrial antiviral signaling protein; NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis; NFKB/NF-κB: nuclear factor of kappa light polypeptide gene enhancer in B cells; PA: palmitic acid; poly:IC: polyinosinic:polycytidylic acid; PRR: pattern recognition receptors; PSR: picrosirus red; RAP: rapamycin; RLR: RIG-I-like receptor; SQSTM1/p62: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK-binding kinase 1.

Effect of replacement of dietary fish oil with four vegetable oils on prostaglandin E2 synthetic pathway and expression of inflammatory genes in marine fish Larimichthys crocea

As a lipid mediator with important immune function, prostaglandin E₂ (PGE₂) has been widely studied in mammals, whereas its synthetic pathway and immune function in fish have yet to be fully studied. To investigate the regulation of PGE₂ synthetic pathway and inflammatory genes expression by dietary different oils and the underlying relationship, a 10-week feeding experiment and an immune challenge were carried out in marine fish Larimichthys crocea. Replacement of dietary fish oil (FO) with four vegetable oils (VO), including soybean oil, linseed oil, palm oil, and olive oil, all reduced PGE₂ levels, and the decrease of arachidonic acid (ARA, substrate for PGE₂) could account for this decline. Meanwhile, the expression of PGE₂ synthesis related genes was basically upregulated, which seemed to be a feedback regulation, but it cannot compensate the deficiency of ARA. In addition, mRNA expression of inflammatory genes, including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)α and interferon (IFN)γ was all upregulated in four VO groups compared with FO group, which was the opposite of PGE₂ levels. To verify the inflammatory regulation of PGE₂, an immune challenge was conducted, and PGE₂ alleviated LPS-induced expression of inflammatory genes, including IL-6, TNFα and IFNγ, and the similar downregulation of toll-like receptor (TLR) genes expression revealed that TLR signaling pathway participated in the anti-inflammatory regulation of PGE₂. In conclusion, replacement of dietary FO with four VO (lack of ARA) reduced the levels of PGE₂ that could alleviate LPS-induced inflammatory genes expression via TLR signaling pathway, which could be one of the reasons that VO induced inflammation in marine fish.

Polyunsaturated Fatty Acids Influence LPS-Induced Inflammation of Fish Macrophages Through Differential Modulation of Pathogen Recognition and p38 MAPK/NF-κB Signaling

Polyunsaturated fatty acids (PUFAs) not only serve as essential nutrients but also function as modulators of the immune response in marine fish. However, their immunomodulatory mechanism is poorly understood given that the underlying regulation of the innate immune response in fish has not been fully elucidated. Hence, study of the innate immunity of fish could help elucidate the mechanism by which PUFAs affect the fish immune response. Here, we used combined transcriptome analysis and in vitro experimentation to study the mechanism of LPS-induced inflammation. Transcriptome profiling indicated that LPS elicited strong pro-inflammatory responses featuring high expression levels of pathogen recognition receptors (PRRs) and cytokines along with the activation of NF-κB and MAPK signaling pathways. The transcription factor p65 alone could increase the transcription of IL1β by binding to the promoter of IL1β, and this promoting effect disappeared after mutation or deletion of its binding sites. We then examined the effects of PUFAs on the levels of gene expression and the abundance of proteins of critical kinases associated with LPS-induced inflammation. We found that LA exerts pro-inflammatory response while ALA, EPA, and DHA induced anti-inflammatory effects by modulating the expression of PRRs, phosphorylation of IKK and p38, and the nuclear translocation of p65. Overall, this study advances our understanding of the regulatory mechanisms by which PUFAs regulate LPS-induced inflammation in a non-model fish species.

Characterization of antiviral immune response induced by poly(I:C) in macrophages of farmed large yellow croaker (Larimichthys crocea)

Fish tend to rely more on their innate immunity to executing defense against viral infection by inducing antiviral gene production. However, the expression pattern and underlying mechanism of fish antiviral responses have yet to be fully defined. In the present study, an in vitro viral infection model was established by exposing head kidney-derived macrophages of large yellow croaker to virus analog, poly(I:C). Transcriptome analysis indicated that poly(I:C) appeared to induce potent antiviral activity featuring dominant interferon a3 (IFNa3) expression through activation of toll-like receptors (TLRs)/TIR-domain-containing adapter-inducing interferon-β (TRIF) and retinoic acid-inducible gene I-like receptors (RLRs)/mitochondrial antiviral signaling protein (MAVS) pathways. Inhibition of nuclear factor κB (NF-κB) and stimulator of interferon genes (STING)/interferon regulatory factor 3 (IRF3) pathways diminished the expression of IFNa3. Mechanistically, transcription factors including p65 and IRF3 could promote expression of IRF3, and activated IRF3 alone further increased the transcriptional activity of IFNa3. We also characterized the promoter of IFNa3 with direct IRF3 binding site which was sufficient to render the transcription of IFNa3. This effect was attenuated after deletion or mutation of the IRF3 binding sites. Taken together, our findings illustrate the distinct transcriptional profiling of fish macrophages triggered by poly(I:C). Also, this work provides new insights into the molecular mechanism underpinning coordinated activation of pathogen recognition and signaling transduction in the antiviral responses of non-model fish species.

Regulation of adiponectin on lipid metabolism in large yellow croaker (Larimichthys crocea)

Adiponectin (APN), an adipose tissue-derived hormone, plays a key role in regulating energy metabolism in mammals. However, its physiological roles in teleosts remain poorly understood. In the present study, the apn gene was cloned from large yellow croaker, which was mainly expressed in the adipose, muscle and liver. Further studies showed that adaptor protein phosphotyrosine interaction PH domain and leucine zipper 1 (APPL1) was localized in the cytoplasm near the cell membrane and was directly bounded to adiponectin receptors (AdipoRs). Meanwhile, APN played a crucial role in lipid metabolism of primary muscle cells by promoting the synthesis, oxidation and transport of fatty acids, and the promoting effects were blocked by knockdown of appl1 and AdipoRs. Furthermore, the activation/inhibition of peroxisome proliferators activated receptor γ (PPARγ) enhanced/suppressed the APN-mediated lipid metabolism. Overall, results showed that APN mediated lipid metabolism through AdipoRs-APPL1 activated PPARγ and further regulated the synthesis, oxidation and transport of FA. This study will facilitate the investigation of APN functions in lipid metabolism and energy homeostasis and reveal the evolution of lipids utilization and energy homeostasis in vertebrates.