The transcriptomic responses of blunt snout bream (Megalobrama amblycephala) to acute hypoxia stress alone, and in combination with bortezomib

Abstract

BackgroundBlunt snout bream (Megalobrama amblycephala) is sensitive to hypoxia. A new blunt snout bream strain, “Pujiang No.2”, was developed to overcome this shortcoming. As a proteasome inhibitor, bortezomib (PS-341) has been shown to affect the adaptation of cells to a hypoxic environment. In the present study, bortezomib was used to explore the hypoxia adaptation mechanism of “Pujiang No.2”. We examined how acute hypoxia alone (hypoxia-treated, HN: 1.0 mg·L− 1), and in combination with bortezomib (hypoxia-bortezomib-treated, HB: Use 1 mg bortezomib for 1 kg fish), impacted the hepatic ultrastructure and transcriptome expression compared to control fish (normoxia-treated, NN).ResultsHypoxia tolerance was significantly decreased in the bortezomib-treated group (LOEcrit, loss of equilibrium, 1.11 mg·L− 1 and 1.32 mg·L− 1) compared to the control group (LOEcrit, 0.73 mg·L− 1 and 0.85 mg·L− 1). The HB group had more severe liver injury than the HN group. Specifically, the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the HB group (52.16 U/gprot, 32 U/gprot) were significantly (p < 0.01) higher than those in the HN group (32.85 U/gprot, 21. 68 U/gprot). In addition, more severe liver damage such as vacuoles, nuclear atrophy, and nuclear lysis were observed in the HB group. RNA-seq was performed on livers from the HN, HB and NN groups. KEGG pathway analysis disclosed that many DEGs (differently expressed genes) were enriched in the HIF-1, FOXO, MAPK, PI3K-Akt and AMPK signaling pathway and their downstream.ConclusionWe explored the adaptation mechanism of “Pujiang No.2” to hypoxia stress by using bortezomib, and combined with transcriptome analysis, accurately captured the genes related to hypoxia tolerance advantage.