Two faces of PPARα/NFκB signaling pathway in inflammatory responses to adipocytes lipolysis in grass carp Ctenopharyngodon idella

Histology and transcriptomic analysis reveal the inflammation and affected pathways under 2-methylisoborneol (2-MIB) exposure on grass carp

2-Methylisoborneol (2-MIB) is a common and widely distributed off-flavor compound in water. However, the toxic mechanisms of 2-MIB on aquatic organisms remain largely unexplored. In this study, grass carp larvae were exposed to different concentrations (0, 5, and 20 μg L-1) of 2-MIB for 96 h. The accumulation of 2-MIB in the dorsal muscle was measured. Histological analysis, ultrastructure observations, and transcriptomic sequencing were conducted on the liver tissues. The results showed that 2-MIB accumulated significantly in the fish muscle, with the accumulation increasing as the exposure concentration increased through gas chromatography-mass spectrometry (GC-MS) detection. Histological and ultrastructure observations indicated that 2-MIB caused concentration-dependent inflammatory infiltration and mitochondrial damage in the liver. Transcriptomic analysis revealed lipid metabolism disorders induced by exposure to 2-MIB in grass carp. Additionally, 5 μg L-1 2-MIB affected the neurodevelopment and cardiovascular system of grass carp larvae through extracellular matrix (ECM)-receptor interaction and focal adhesion pathway. Furthermore, several pathways related to the digestive system were significantly enriched, implying that 2-MIB may impact pancreatic secretion function, protein digestion and absorption processes. These findings provide new insights into the potential toxicological mechanisms of 2-MIB.

Exogenous APN protects normal tissues from radiation-induced oxidative damage and fibrosis in mice and prostate cancer patients with higher levels of APN have less radiation-induced toxicities

Radiation causes damage to normal tissues that leads to increased oxidative stress, inflammation, and fibrosis, highlighting the need for the selective radioprotection of healthy tissues without hindering radiotherapy effectiveness in cancer. This study shows that adiponectin, an adipokine secreted by adipocytes, protects normal tissues from radiation damage invitro and invivo. Specifically, adiponectin (APN) reduces chronic oxidative stress and fibrosis in irradiated mice. Importantly, APN also conferred no protection from radiation to prostate cancer cells. Adipose tissue is the primary source of circulating endogenous adiponectin. However, this study shows that adipose tissue is sensitive to radiation exposure exhibiting morphological changes and persistent oxidative damage. In addition, radiation results in a significant and chronic reduction in blood APN levels from adipose tissue in mice and human prostate cancer patients exposed to pelvic irradiation. APN levels negatively correlated with bowel toxicity and overall toxicities associated with radiotherapy in prostate cancer patients. Thus, protecting, or modulating APN signaling may improve outcomes for prostate cancer patients undergoing radiotherapy.

Alcoholic fatty liver disease inhibited the co-expression of Fmo5 and PPARα to activate the NF-κB signaling pathway, thereby reducing liver injury via inducing gut microbiota disturbance

Background

Alcohol-induced intestinal dysbiosis disrupts and inflammatory responses are essential in the development of alcoholic fatty liver disease (AFLD). Here, we investigated the effects of Fmo5 on changes in enteric microbiome composition in a model of AFLD and dissected the pathogenic role of Fmo5 in AFLD-induced liver pathology.

Methods

The expression profile data of GSE8006 and GSE40334 datasets were downloaded from the GEO database. The WGCNA approach allowed us to investigate the AFLD-correlated module. DEGs were used to perform KEGG pathway enrichment analyses. Four PPI networks were constructed using the STRING database and visualized using Cytoscape software. The Cytohubba plug-in was used to identify the hub genes. Western blot and immunohistochemistry assays were used to detect protein expression. ELISA assay was used to detect the levels of serum inflammatory cytokines. Lipid droplets in the cytoplasm were observed using Oil Red O staining. Apoptosis was detected using a TUNEL assay and flow cytometry analysis. ROS levels were detected using flow cytometry analysis. Nuclear translocation of NF-κB p65 was observed using immunofluorescence staining. Co-immunoprecipitation was used to detect the co-expression of PPARα and Fmo5 in L02 cells. 16S rDNA sequencing defined the bacterial communities in mice with AFLD.

Results

Fmo5 is a key DEG and is closely associated with the gut microbiota and PPAR signaling pathway. Gut microbiome function in AFLD was significantly related to the PPAR signaling pathway. AFLD induced shifts in various bacterial phyla in the cecum, including a reduction in Bacteroidetes and increased Firmicutes. Fmo5 and PPARα co-expression in cell and animal models with AFLD, which decreased significantly. Silencing of Fmo5 and PPARα aggravated the functions of AFLD inducing apoptosis and inflammatory response, promoting liver injury, and activating the NF-κB signaling pathway in vivo and in vitro. The NF-κB inhibitor abolished the functions of silencing of Fmo5 and PPARα promoting AFLD-induced apoptosis, inflammatory response, and liver injury.

Conclusion

Our data indicated that the co-expression of Fmo5 and PPARα was involved in AFLD-related gut microbiota composition and alleviated AFLD-induced liver injury, apoptosis, and inflammatory response by inhibiting the nuclear translocation of NF-κB p65 to inhibit the NF-κB signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01782-w.

Identification and innate immunity mechanism of protective immunogens from extracellular proteins of Edwardsiella tarda

One of the most important emerging pathogens in the aquaculture industry is Edwardsiella tarda, and it causes extensive losses in farmed fish globally. The identification of protective immunogens against E. tarda is increasingly valued. We previously investigated 20 recombinant proteins of 38 E. tarda extracellular secretory proteins and identified 10 as protective immunogens in a zebrafish model. Here, we clone 10 of the remaining 18 genes, and the resulting recombinant proteins are used for evaluation of immune protection. ETAE_2147 (FliK), ETAE_0654 (PpdD), and ETAE_3259 (DamX) are identified as protective immunogens. Furthermore, their protection mechanism is explored by the detection of innate immunity genes encoding IL-1b, IL-6, IL-8, C3b, and NF-κB. The three protective immunogens stimulate zebrafish to produce higher and more lasting expression of the five immunity genes than non-protective immunogens during the first 48 h of infection. In addition, these protective immunogens are prone to be regulated by host products, which is helpful for cross-talk between host and pathogen, and thus they become vaccine candidates. These results highlight the way to understand the working mechanisms of protective immunogens.

PPARα activation enhances the ability of nile tilapia (Oreochromis niloticus) to resist Aeromonas hydrophila infection

Peroxisome proliferator-activated receptor α (PPARα) plays critical physiological roles in energy metabolism, antioxidation and immunity of mammals, however, these functions have not been fully understood in fish. In the present study, Nile tilapia (Oreochromis niloticus) were fed with fenofibrate, an agonist of PPARα, for six weeks, and subsequently challenged with Aeromonas hydrophila. The results showed that PPARα was efficiently activated by fenofibrate through increasing mRNA and protein expressions and protein dephosphorylation. PPARα activation increased significantly mitochondrial fatty acid β-oxidation efficiency, the copy number of mitochondrial DNA and expression of monoamine oxidase (MAO), a marker gene of mitochondria. Meanwhile, PPARα activation also increased significantly the expression of NADH dehydrogenase [ubiquinone] 1α subcomplex subunit 9 (NDUFA9, complex I) and mitochondrial cytochrome c oxidase 1 (MTCO1, complex IV). The fenofibrate-fed fish had higher survival rate when exposed to A. hydrophila. Moreover, the fenofibrate-fed fish also had higher activities of immune and antioxidative enzymes, and gene expressions of anti-inflammatory cytokines, while had lower expressions of pro-inflammatory cytokine genes. Taken together, PPARα activation improved the ability of Nile tilapia to resist A. hydrophila, mainly through enhancing mitochondrial fatty acids β-oxidation, immune and antioxidant capacities, as well as inhibiting inflammation. This is the first study showing the regulatory effects of PPARα activation on immune functions through increasing mitochondria-mediated energy supply in fish.