IRF3 enhances NF-κB activation by targeting IκBα for degradation in teleost fish

PSMD13 inhibits NF-κB pathway by targeting TAK1 for K63-linked ubiquitination in miiuy croaker (Miichthys miiuy)

ransforming growth factor-β activated kinase (TAK) 1 is an adaptor molecular in the TLR-mediated NF-κB pathway which has been implicated in the regulation of a wide range of physiological and pathological processes. Proteasome 26S subunit, non-ATPases (PSMD) 13 is essential for the structural maintenance and function of the 26S proteasome. However, the mechanism of PSMD13 in innate immune regulation is not clear. In this study, the expression of PSMD13 mRNA was significantly increased under Vibrio harveyi stimulation, and PSMD13 inhibited the NF-κB pathway by targeting TAK1. Mechanically, PSMD13 significantly inhibited the K63-linked ubiquitination of TAK1, thereby inhibiting the expression of TAK1. Moreover, this discovery enriches the research of the PSMD family regulating the innate immune response and provides a new idea for the study of the mammalian innate immune regulation mechanism.

Effect of CRISPR/Cas9-mediated knockout of either IRF-3 or IRF-5 gene in Epithelioma papulosum cyprini cells on type I interferon response and NF-κB activity

Transcription factors related to the activation of type I interferons (IFNs) and nuclear factor-kappa B (NF-κB) are known to be critical in innate immune responses. Interferon regulatory factors (IRFs) are a family of transcription factors. IRF-3 is known to act as the primary regulator in type I IFN signaling in response to viral infections, and the upregulation of IRF5 by virus infection has been reported in various fish species. One of the ways to know the functional role of certain genes is the production of target gene(s) knockout cells or organisms. In the present study, we produced either IRF3 or IRF5 gene knockout Epithelioma papulosum cyprini (EPC) cells using a CRISPR/Cas9 system, and investigated the effect of IRF3 gene and IRF5 gene knockout on polyinosinic:polycytidylic acid (ploly (I:C))-mediated and viral hemorrhagic septicemia virus (VHSV) infection-mediated type I IFN response and NF-κB activation. Both IRF3 knockout and IRF5 knockout EPC cells showed severely decreased type I IFN responses measured by ISRE activity and the expression of Mx1 and ISG15 genes when stimulated with poly (I:C), while the decreased level of type I IFN responses was not high as by poly (I:C) stimulation when infected with VHSV. Different from type I IFN response, NF-κB activities in IRF3 and IRF5 knockout cells were not highly different between poly (I:C) stimulated cells and VHSV-infected cells. Further studies are needed to elucidate pathways responsible for the type I IFN responses and NF-κB activation by VHSV infection.

New Insights into the Crosstalk among the Interferon and Inflammatory Signaling Pathways in Response to Viral Infections: Defense or Homeostasis

Innate immunity plays critical roles in eliminating viral infections, healing an injury, and restoring tissue homeostasis. The signaling pathways of innate immunity, including interferons (IFNs), nuclear factor kappa B (NF-κB), and inflammasome responses, are activated upon viral infections. Crosstalk and interplay among signaling pathways are involved in the complex regulation of antiviral activity and homeostasis. To date, accumulating evidence has demonstrated that NF-κB or inflammasome signaling exhibits regulatory effects on IFN signaling. In addition, several adaptors participate in the crosstalk between IFNs and the inflammatory response. Furthermore, the key adaptors in innate immune signaling pathways or the downstream cytokines can modulate the activation of other signaling pathways, leading to excessive inflammatory responses or insufficient antiviral effects, which further results in tissue injury. This review focuses on the crosstalk between IFN and inflammatory signaling to regulate defense and homeostasis. A deeper understanding of the functional aspects of the crosstalk of innate immunity facilitates the development of targeted treatments for imbalanced homeostasis.

Effects of Lysophosphatidylcholine on Intestinal Health of Turbot Fed High-Lipid Diets

An 8-week feeding trial was conducted, where turbot were fed four experimental diets, containing different LPC levels (0%, 0.1%, 0.25%, and 0.5%, named LPC0, LPC0.1, LPC0.25, and LPC0.5, respectively). The intestinal morphology results showed that there were no widened lamina propria and mixed inflammatory cells in the LPC-supplemented groups. Dietary LPC remarkably decreased the expression of TLRs (TLR3, TLR8, TLR9, and TLR22), MyD88, and signaling molecules (NF-κB, JNK, and AP-1). Similarly, diets with LPC supplementation markedly depressed the gene expression of NF-κB and JNK signaling pathway downstream genes (TNF-α, IL-1β, Bax, Caspase9, and Caspase-3). Furthermore, dietary LPC modified the intestinal microbial profiles, increasing the relative abundance of short-chain fatty acids-producers, lactic acid bacteria, and digestive enzyme-producing bacteria. Predictive functions of intestinal microbiota showed that turbot fed LPC diets had a relatively higher abundance of functions, such as lipid metabolism and immune system, but a lower abundance of functions, such as metabolic diseases and immune system diseases. The activities of intestinal acid phosphatase and alkaline phosphatase were also increased by dietary LPC. In conclusion, LPC supplementation could regulate the intestinal mucosal barrier via the TLR signaling pathway and alter the intestinal microbiota profile of turbot fed high-lipid diets.

Rho-GDP-dissociation inhibitor-γ negatively regulates NF-κB signaling by promoting the degradation of TAK1 in miiuy croaker (Miichthys miiuy)

Transforming growth factor-beta activated kinase 1 (TAK1) is an adaptor molecular in TLR-mediated NF-κB signaling pathway and plays indispensable roles in innate immunity. As the most typical innate immune pathway, the strict regulation of NF-κB signaling pathway is particularly important. Rho-GDP-dissociation inhibitor-γ (Rho-GDIγ) is a member of the Rho protein family that regulates many important physiological processes. In this study, we demonstrated the mechanism of suppressing TAK1 expression in the teleost and found that Rho-GDIγ negatively regulated the NF-κB signaling pathway mediated by TAK1. We determined that TAK1 could directly interact with Rho-GDIγ. It is interesting that Rho-GDIγ promotes TAK1 degradation through the ubiquitin proteasome pathway. This study brings a new experimental basis to the teleost fish innate immune signaling pathway. Moreover, this discovery may provide new insights into innate immune regulation mechanism in mammals.

TELOMERASE MEDIATEDS PYROPTOSIS BY NF-κB Chicken telomerase reverse transcriptase mediates LMH cell pyroptosis by regulating the nuclear factor-kappa B signaling pathway

The activation of human telomerase reverse transcriptase is regulated by the nuclear factor kappa B (NF-κB) signaling pathway to various degrees to promote the occurrence and development of tumors. However, the regulatory roles of chicken telomerase reverse transcriptase (chTERT) and the NF-κB signaling pathway in chickens are still elusive, particularly in respect to the regulation of cell pyroptosis. In this study, we found that chTERT upregulated the expression of p65 and p50, downregulated the expression of IκBα, promoted the phosphorylation of p65, p50, and IκBα, and significantly increased the transcript levels of the inflammatory cytokines IFNγ, TNFα, and IL-6 in LMH cells. The activity of NF-κB was significantly decreased after siRNA-mediated chTERT silencing. The expression of chTERT and telomerase activity were also significantly decreased when the NF-κB signaling pathway was blocked by p65 siRNA, MG132 or BAY 11-7082. In cells treated with LPS, the activity of NF-κB signaling pathway and the expression of chTERT were significantly upregulated. All of the results suggested that chTERT and the NF-κB pathway could regulate each other, reciprocally. Moreover, the expression of Caspase-1, NLRP3, GSDMA, IL-18, and IL-1β and caused membrane perforation, suggesting the development of pyroptosis by chTERT in LMH cells. And the expression of caspase-11 did not significantly increased in chTERT overexpression group. Genetic silence of NF-κB p65 or chTERT gene by siRNA suppressed the expression of these proinflammatory cytokines, indicating that chTERT mediates pyroptosis by regulating the NF-κB signaling pathway in LMH cells.

IRF11 enhances the inhibitory effect of IκBα on NF-κB activation in miiuy croaker

NF-κB is a typical transcription factor that regulates expression of various genes involved in inflammatory and immune responses. Therefore, it is essential that NF-κB signaling tightly regulated to maintain immune balance. Compared with those of mammals, the regulatory mechanisms of NF-κB signaling is rarely reported in teleost fish. IκBα is a prominent negative feedback regulator in the NF-κB signaling system. In this study, we determined that IRF11 enhances the inhibitory effect of IκBα on NF-κB activation in teleost fish. Overexpression of IRF11 can inhibit IκBα degradation, whereas its knockdown has the opposite effect of IκBα. Our study further indicates that IκBα was regulated via ubiquitin-proteasome degradation pathway, IRF11 inhibits IκBα in ubiquitin-proteasome degradation. This study provides a novel evidence on the regulation of innate immune signaling pathways in teleost fish and thus provides new insights into the regulatory mechanisms in mammals.

Insights Into the Albinism Mechanism for Two Distinct Color Morphs of Northern Snakehead, Channa argus Through Histological and Transcriptome Analyses

The great northern snakehead (Channa argus) is one of the most important economic and conservational fish in China. In this study, the melanocytes in the skin of two distinct color morphs C. argus were investigated and compared through employment of the microscopic analysis, hematoxylin and eosin (H&E) and Masson Fontana staining. Our results demonstrated the uneven distribution of melanocytes with extremely low density and most of them were in the state of aging or death. Meanwhile, there was no obvious pigment layer and melanocytes distribution pattern found in the albino-type (AT), while the melanocytes were evenly distributed with abundance in the bicolor-type (BT). The transcriptome analysis through Illumina HiSeq sequencing showed that a total of 34.93 Gb Clean Data was obtained, and Q30 base percentage reached 92.66%. The BT and AT northern snakeheads transcriptome data included a total of 56,039,701 and 60,410,063 clean reads (n = 3), respectively. In gene expression analyses, the sample correlation coefficients (r) were ranged between 0.92 and 1.00; the contribution of PC1 and PC2 were 50.25 and 13.73% by using PCA cluster analysis, the total number of DEGs were 1024 (559 up-regulated and 465 down-regulated), and the number of annotated DEGs was 767 (COG 172, KEGG 262, GO 288, SwissProt 548, Pfam 579 and NR 765). Additionally, 46,363 ± 873 and 44,947 ± 392 single nucleotide polymorphisms (SNPs) were compiled via genetic structure analysis, respectively. Ten key pigment-related genes were screened using qRT-PCR. And all of them revealed extremely higher expression levels in the skin of BT than those of AT. This is the first study to analyze the mechanism of albino characteristics of Channa via histology and transcriptomics, and also provide the oretical and practical support for the protection and development of germplasm resources for C. argus.