Hypoxia and reoxygenation induce changes in oxidative stress, histological structure, and transcriptome in the liver of mandarin fish (Siniperca chuatsi).

The mandarin fish (Siniperca chuatsi, MD) is a highly valued freshwater economic fish species in China, but it exhibits a notably low tolerance to a hypoxic environment. However, the underlying regulatory mechanisms in response to environmental hypoxia and reoxygenation stress remain poorly understood. Therefore, we examined liver biochemical parameters and transcriptomes of MD under normoxic, hypoxic, and reoxygenation conditions, aiming to illuminate the dynamic changes in molecular regulatory mechanisms and oxidative stress responses. This study revealed that the enzymatic antioxidant systems acted in a coordinated manner to alleviate oxidative stress injury caused by hypoxia. In RNA-seq analysis, we identified differentially expressed genes (DEGs) and conducted enrichment analysis. Among the Gene Ontology (GO) functional categories, several critical hypoxia-related genes (nfkbia, vegfa, aplnr) in biological processes were observed. Furthermore, based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses, the finding revealed that many DEGs were involved in the HIF-1 signaling pathway (gln, epo, vegfa, pfka, ldh), AMPK signaling pathway (pfka, eef2k, gys), p53 signaling pathway (ccne, gtse1), PI3K-Akt signaling pathway (ddit4, egf, gh, ghr, vwf, gys), and NOD-like receptor signaling pathway (atg8, sharpin, ifnar1), among others. This study offers crucial insights into elucidating the molecular regulatory mechanisms underlying hypoxia stress, and holds the potential to facilitate the development of effective strategies for coping with environmental hypoxia and reoxygenation stress in MD. This is valuable for fish genetic improvement.