Transcriptome analysis reveals immune regulation in the spleen of koi carp (Cyprinus carpio Koi) during Aeromonas hydrophila infection

The role of cortisol in the acute immune regulation of channel catfish (Ictalurus punctatus) spleen stimulated by Aeromonas hydrophila

Channel catfish (Ictalurus punctatus), a significant aquaculture species, occupies a prominent position in the aquaculture industry due to its rapid growth, excellent adaptability, and economic value; however, the hemorrhagic disease caused by Aeromonas hydrophila has had a substantial impact on its cultivation. Researches have indicated that cortisol, the main stress hormone, is essential for regulating immune responses. Therefore, in this study, the immune regulatory effects of cortisol on the spleen tissue under Aeromonas hydrophila stimulation were analyzed. Through transcriptomic (RNA-seq) analysis, we identified 167 differentially expressed genes (DEGs) regulated by cortisol. The KEGG enrichment analysis indicated that the DEGs were predominantly associated with various biological pathways, including antigen processing and presentation, bladder cancer, autophagy in animals, lipid metabolism, and atherosclerosis. Protein-protein interaction network analysis further indicated that these DEGs participate in key signaling pathways, including HIF, JAK-STAT, and NF-KB. Our findings demonstrate that cortisol exerts an immunoregulatory effect by modulating these key signaling pathways in the spleen tissue infected with Aeromonas hydrophila, which is of significant importance for understanding the mechanism of cortisol in fish immune responses.

Molecular Response and Metabolic Reprogramming of the Spleen Coping with Cold Stress in the Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The Chinese soft-shelled turtle (Pelodiscus sinensis), as a type of warm-water reptile, could be induced to massive death by sharp temperature decline. Hence, the mechanism of spleen tissue responding to cold stress in the P. sinensis was investigated. The present results showed that the superoxide dismutase (SOD) activity declined from 4 to 16 days post-cold-stress (dps), while the catalase (CAT) and glutathione peroxidase (GSH-Px) activities increased, from 4 to 8 dps in the 14 °C (T14) and 7 °C (T7) stress groups. The spleen transcriptome in the T7 group and the control group (CG) at 4 dps obtained 2625 differentially expressed genes (DEGs), including 1462 upregulated and 1663 downregulated genes. The DEGs were enriched mainly in the pathways "intestinal immune network for IgA production" (Pigr, Il15ra, Tnfrsf17, Aicda, and Cd28), "toll-like receptor signaling pathway" (Mapk10, Tlr2, Tlr5, Tlr7, and Tlr8), and "cytokine-cytokine receptor interaction" (Cx3cl1, Cx3cr1, Cxcl14, Cxcr3, and Cxcr4). The metabolomic data showed that esculentic acid, tyrosol, diosgenin, heptadecanoic acid, and 7-ketodeoxycholic acid were obviously increased, while baccatin III, taurohyocholate, parthenolide, enterolactone, and tricin were decreased, in the CG vs. T7 comparison. Integrated analysis of the two omics revealed that "glycine, serine and threonine metabolism", "FoxO signaling pathway", and "neuroactive ligand-receptor interaction" were the main pathways responding to the cold stress. Overall, this work found that low temperature remarkably influenced the antioxidant enzyme activities, gene expression pattern, and metabolite profile in the spleen, indicating that immunity might be weakened by cold stress in P. sinensis.

Elevated Levels of Interleukin-18 are Associated with Lymph Node Metastasis in Papillary Thyroid Carcinoma

Interleukin-18 (IL-18) is a proinflammatory cytokine that primarily stimulates the Th1 immune response. IL-18 exhibits anticancer activity and has been evaluated in clinical trials as a potential cancer treatment. However, evidence suggests that it may also facilitate the development and progression of some cancers. So far, the impact of IL-18 on papillary thyroid cancer (PTC) has not been investigated. In this study, we found that the expression of IL-18 was significantly increased in PTC compared to normal thyroid tissue. Elevated IL-18 expression was closely associated with lymphovascular invasion and lymph node metastases. Furthermore, compared to PTC patients with no nodal metastasis, serum IL-18 levels were slightly increased in patients with 1-4 nodal metastases and significantly elevated in patients with 5 or more nodal metastases. The pro-metastatic effect of IL-18 may be attributed to the simultaneous increase in the expression of S100A10, a known factor that is linked to nodal metastasis in PTC. In addition, the activation of several pathways, such as the intestinal immune network for lgA production and Staphylococcus aureus infection, may be involved in the metastasis process. Taken together, IL-18 may trigger pro-metastatic activity in PTC. Therefore, suppressing the function of IL-18 rather than enhancing it appears to be a reasonable strategy for treating aggressive PTC.

Transcriptome analysis of host anti-Aeromonas hydrophila infection revealed the pathogenicity of A. hydrophila to American eels (Anguilla rostrata)

Aeromonas hydrophila is a commonly pathogenic bacterium in cultivated eels, but its pathogenicity to American eel (Anguilla rostrata) and the molecular mechanism of host anti-A. hydrophila infection remains uncertain. In this study, LD50 of A. hydrophila to American eels was determined and bacterial load in the liver and kidney of eels was assessed post 2.56 doses of LD50 of A. hydrophila infection. The results showed that the LD50 of A. hydrophila to American eels was determined to be 3.9 × 105 cfu/g body weight (7.8 × 106 cfu/fish), and the bacterial load peaked at 36 h post the infection (hpi) in the liver. Then, the histopathology was highlighted by congestion in splenic blood vessels, atrophied glomeruli, and necrotic hepatocytes. Additionally, the results of qRT-PCR revealed that 18 host immune-related genes showed significantly up or downregulated post-infection compare to that of pre-infection. Finally, results of the RNA-seq revealed 10 hub DEGs and 7 encoded proteins play essential role to the anti-A. hydrophila infection in American eels. Pathogenicity of A. hydrophila to American eels and RNA-seq of host anti-A. hydrophila infection were firstly reported in this study, shedding new light on our understanding of the A. hydrophila pathogenesis and the host immune response to the A. hydrophila infection strategies in gene transcript.

Transcriptome Analysis of Host Anti-Vibrio harveyi Infection Revealed the Pathogenicity of V. harveyi to American Eel (Anguilla rostrata)

Vibrio harveyi, a recently discovered pathogenic bacterium isolated from American eels (Anguilla rostrata), poses uncertainties regarding its pathogenesis in American eel and the molecular mechanisms underlying host defense against V. harveyi infection. This study aimed to determine the LD50 of V. harveyi in American eel and assess the bacterial load in the liver, spleen, and kidney post-infection with the LD50 dose. The results showed that the LD50 of V. harveyi via intraperitoneal injection in American eels over a 14d period was determined to be 1.24 × 103 cfu/g body weight (6.2 × 104 cfu/fish). The peak bacterial load occurred at 36 h post-infection (hpi) in all three organs examined. Histopathology analysis revealed hepatic vein congestion and thrombi, tubular vacuolar degeneration, and splenic bleeding. Moreover, quantitative reverse transcription polymerase chain reaction (qRT-PCR) results indicated significant up or downregulation of 18 host immune- or anti-infection-related genes post 12 to 60 hpi following the infection. Additionally, RNA sequencing (RNA-seq) unveiled 7 hub differentially expressed genes (DEGs) and 11 encoded proteins play crucial roles in the anti-V. harveyi response in American eels. This study firstly represents the comprehensive report on the pathogenicity of V. harveyi to American eels and RNA-seq of host's response to V. harveyi infection. These findings provide valuable insights into V. harveyi pathogenesis and the strategies employed by the host's immune system at the transcriptomic level to combat V. harveyi infection.