Physiological changes and transcriptional modulation of HIF-αs in Siberian sturgeon in response to hypoxia

To clarify the effects of acute hypoxia on physiological response and mRNA expression of Hypoxia-inducible factors (HIFs) in Siberian sturgeon, a chondrostean fish, severe hypoxia treatment was implemented by transfer of sturgeons from normoxia (DO = 7 mg/mL) to hypoxia (DO = 2 mg/mL). We found that the levels of serum cortisol, GLU, SOD, LDH, CK and CREA increased significantly at the early time-points post hypoxia exposure. Whereas the activity of immune related enzyme - AKP showed a sudden drop, followed by a recovery. Further, we identified and characterized three hif-alpha s cDNA sequences, namely Abhif-1 alpha, Abhif-2 alpha, and Abhif-3 alpha. The mRNA abundance of three hif-alpha s was all rich in brain, heart and liver. During acute hypoxia exposure, Abhif-1 alpha and Abhif-3 alpha mRNA expression levels increased significantly in the heart, gill and brain at early time-points, and gradually declined later on. Abhif-2 alpha only showed a slight increase in the gill upon hypoxia stress. In conclusion, we observed that, acute hypoxia affected the muscle function and immune related enzyme activity of Acipenser baeri; in response to hypoxia stress, sturgeons enhanced antioxidant capacity, anaerobic metabolism and up regulated the transcriptional expression of Abhif-1 alpha and Abhif-3 alpha. Our results might be helpful for further understanding of the potential effect of hypoxia on chondrostean fish and their molecular anti-hypoxia mechanisms.

Automated summary

Acute hypoxia had significant effects on the physiological responses and mRNA expression of Hypoxia-inducible factors (HIFs) in Siberian sturgeon. The study revealed changes in serum biochemical parameters, immune related enzyme activity, and the expression levels of hif-alpha genes in response to hypoxia stress. Sturgeons exhibited enhanced antioxidant capacity and upregulation of Abhif-1 alpha and Abhif-3 alpha transcription in heart, gill, and brain under acute hypoxia exposure.