Integrated Application of Multiomics Strategies Provides Insights Into the Environmental Hypoxia Response in Pelteobagrus vachelli Muscle.

Increasing pressures on aquatic ecosystems because of pollutants, nutrient enrichment, and global warming have severely depleted oxygen concentrations. This sudden and significant lack of oxygen has resulted in persistent increases in fish mortality rates. Revealing the molecular mechanism of fish hypoxia adaptation will help researchers to find markers for hypoxia induced by environmental stress. Here, we used a multiomics approach to identify several hypoxia-associated miRNAs, mRNAs, proteins, and metabolites involved in diverse biological pathways in the muscles of Pelteobagrus vachelli. Our findings revealed significant hypoxia-associated changes in muscles over 4 h of hypoxia exposure and discrete tissue-specific patterns. We have previously reported that P. vachelli livers exhibit increased anaerobic glycolysis, heme synthesis, erythropoiesis, and inhibit apoptosis when exposed to hypoxia for 4 h. However, the opposite was observed in muscles. According to our comprehensive analysis, fishes show an acute response to hypoxia, including activation of catabolic pathways to generate more energy, reduction of biosynthesis to decrease energy consumption, and shifting from aerobic to anaerobic metabolic contributions. Also, we found that hypoxia induced muscle dysfunction by impairing mitochondrial function, activating inflammasomes, and apoptosis. The hypoxia-induced mitochondrial dysfunction enhanced oxidative stress, apoptosis, and further triggered interleukin-1ß production via inflammasome activation. In turn, interleukin-1ß further impaired mitochondrial function or apoptosis by suppressing downstream mitochondrial biosynthesis-related proteins, thus resulting in a vicious cycle of inflammasome activation and mitochondrial dysfunction. Our findings contribute meaningful insights into the molecular mechanisms of hypoxia, and the methods and study design can be utilized across different fish species.

Environmental salinity influences the branchial expression of TCR pathway related genes based on transcriptome of a catadromous fish.

Environmental salinity not only affects the physiological processes such as osmoregulation and hormonal control, but also changes the immune system in fishes. Studies are limited in fish on the roles of the T cell receptor (TCR)-related genes in relation to changes in environmental salinity. A large group of salinity-challenged transcripts was obtained in gills of marbled eel (Anguilla marmorata). Moreover, bioinformatic ways were used to identify the enriched TCR pathway related genes which were significantly different expressed in fresh water (FW), brackish water (BW) and seawater (SW). Meanwhile, the RT-qPCR results were validated and consistent with the RNA-seq results. TCR a, TCR b, CD45, CD28, PI3K, LCK and LAT were up-regulated when the salinity increases in BW and SW, which connected with the related signaling pathways (Ras-MAPK and PKC pathway). CD4 and Zap70 were down-regulated when the salinity increases in BW and SW, which connected with the PLC pathway. The research offers a novel viewpoint to explore the immune pathways including the TCR pathway in fish based on transcriptome.