The role of HIF-1α in the energy metabolism and immune responses of hypoxic Scylla paramamosain

The HIF-1 alpha subunit (HIF-1α) is a master regulator of oxygen sensitivity. This study investigated the role of HIF-1α in the energy metabolism and immune responses of hypoxic Scylla paramamosain. After hypoxia treatment for 12 h, the expression levels of HIF-1α in the hemocytes, gills and hepatopancreas were significantly upregulated. After hypoxia and dsHIF-1α treatment for 12 h, the expression level of HIF-1α in hemocytes was successfully inhibited by specific double-strand RNAs for HIF-1α (dsHIF-1α). After inhibition of HIF-1α expression, the expression levels of prophenol oxidase, ATP synthase subunit beta, and Astakine were significantly upregulated, and those of C-type-lectin and lactate dehydrogenase (LDH) were significantly downregulated; the activities of catalase, pyruvate kinase and LDH as well as the contents of pyruvic acid and lactic acid and the levels of apoptosis and phagocytosis in hypoxic S. paramamosain were all significantly decreased. After challenge by Vibrio alginolyticus, the survival rate was significantly lower in hypoxia and dsHIF-1α treated S. paramamosain. Since cell proliferation is an energy-dependent process, the impaired glycolysis after inhibition of HIF-1α expression might be the main reason for the significant decrease of V. alginolyticus burden in hypoxic S. paramamosain. These results indicated that activated HIF-1α enhanced the resistance of S. paramamosain to V. alginolyticus under hypoxic conditions, and the enhanced resistance may be related to the changes in important immune- and metabolism-related gene expression, CAT and PO activities, total hemocyte count, apoptosis, phagocytosis, and anaerobic glycolysis.