Project description:Hypoxia has become one of the most critical factors limiting the development of aquaculture. Crucian carp (Carassius auratus) is widely consumed fish in China, with excellent tolerance to hypoxic environment. However, the molecular mechanisms underlying hypoxia adaptation and tolerance in crucian carp remain unclear. In this study, we detected the changes of biochemical parameters after hypoxia stress (3 h (H3h), H12h, and H24h) and reoxygenation (reoxygenation for 3 h after hypoxia 24 h (R3h)), mRNA and miRNA expression profiles under H12h compared to the control, and key hypoxia-related genes expression patterns in the liver of crucian carp through biochemical methods, RNA-seq, and qRT-PCR. Compared with the control, increased T-SOD, CAT, GSH-Px, T-AOC, ALT, and AST activities and MDA, TCHO, and TG contents, and decreased TP and ATP contents were observed after hypoxia stress, and LDH activity increased only in the H12h and H24h groups. Based on RNA-seq, 2479 differentially expressed (DE) mRNAs and 60 DE miRNAs were identified, and numerous DE mRNAs involved in HIF signaling pathway (hif-1α, epo, vegfa, and ho), anaerobic metabolism (hk1/hk2, pfk, gapdh, pk, and ldh) and immune response (nlrc3, nlrp12, cxcr1, cxcr4, ccr9, and cxcl12) were significantly upregulated after hypoxia exposure. Integrated analysis found that ho, igfbp1, hsp70, and hk2 were predicted to be regulated by novel_867, dre-miR-125c-3p/novel_173, dre-miR-181b-5p, and dre-miR-338-5p/dre-miR-128-3p, respectively, and targets of DE miRNAs were significantly enriched in MAPK signaling pathway, FoxO signaling pathway, glycolysis/gluconeogenesis, insulin signaling pathway, NOD−like receptor signaling pathway, and cytokine-cytokine receptor interaction. Expression analysis showed that the mRNA levels of vegfa, epo, ho, hsp70, hsp90aa.1, igfbp1, ldh, hk1, pfk, pk, and gapdh exhibited a remarkable increase, whereas sdh and mdh were downregulated in the H3h, H12h, and H24h groups compared with the control. These results contribute to our understanding of the molecular mechanisms of hypoxia tolerance in crucian carp, which are of great significance for genetics and breeding of other fishes tolerant to hypoxia.

Project description:More and more evidence prove that deltamethrin (Del) exposure induced the adverse effect and damaged immune function to the aquatic animals in the parasite killing process with increasing insecticide application. However, little is currently known of the negative effect on mucosal immunity, especially in gills tissue. In this study, the LC50 of deltamethrin on gibel carp at 96h was determined to be 6.194 μg/L, and then juvenile gibel carp (Carassius auratus gibelio) (8.8 ± 1.0 g) were exposed to four Del exposure groups (0.61, 1.22, 2.44, and 4.88 μg/L) for 12h and 24h. To evaluate the innate immune-related enzymes in gills tissue, we measured the lysozyme (LYZ) and myeloperoxidase (MPO) contents and found that with increased concentration of Del exposure, the LYZ content was found to increase in the 1.22 μg/L Del group initially significantly and then gradually significantly decrease in the 4.88 μg/L Del group. And the activity of MPO was significantly lifted in a dose-dependent manner. The histological analysis showed that Del exposure serious desquamation and necrosis in the surface of epithelial cells are often found, accompanied by interlamellar cellular mass degenerative. In addition, the mucous cells were significantly decreased in the high Del concentration group (2.44 μg/L and 4.88 μg/L Del group) by AB-PAS staining. Importantly, totally 2857 DEGs (including 1624 up-regulated and 1233 down-regulated genes) were identified in the gill between the control group and 4.88μg/L Del exposure group using comparative transcriptional analysis. Among these, some genes involved in innate immune molecules, complement activation, apoptosis-related molecules, cytokine, and adaptive immune molecules, were also down-regulated. Importantly, we found several signal pathways related to immune response were downregulated, such as immune system process and tumor necrosis factor receptor (superfamily) binding pathways based on the GO and KEGG enrichment analysis. Consistently, we detect the expression of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, and IL-8), anti-inflammatory cytokines (TGF-β), LYZ, IgM, and Hsp70 in the gills tissue at 12h and 24h after Del exposure, which were consistent with our sequencing results. Collectively, these results demonstrated that the gills mucosa injury and immunotoxicity was induced by Del exposure and provided novel insight for explaining to some extent why Del-exposure fish and are more susceptible to concurrent or secondary viral or bacterial infections.

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Changes in brain transcriptome and metabolome of juvenile crucian carp after chronic deltamethrin exposure

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