Molecular characterization of mudskipper (Boleophthalmus pectinirostris) hypoxia-inducible factor-1α (HIF-1α) and analysis of its function in monocytes/macrophages.

Hypoxia-inducible factor-1α (HIF-1α) plays a critical role in immune and inflammatory responses and is important in controlling a variety of processes in monocytes and macrophages. However, very little information is available about the functions of HIF-1α in fish monocytes/macrophages (MO/MФ). In this study, the cDNA sequence of the mudskipper (Boleophthalmus pectinirostris) HIF-1α gene (BpHIF-1α) was determined. Sequence comparison and phylogenetic tree analysis showed that BpHIF-1α is clustered in the fish HIF-1α tree. Constitutive expression of BpHIF-1α mRNA was detected by real-time quantitative PCR in all tested tissues, and the expression was found to be dramatically increased in the skin, liver, spleen, and kidney after Edwardsiella tarda infection. In addition, hypoxia and infection induced the expression of the BpHIF-1α transcript and protein in MO/MФ, respectively. Hypoxia caused an increase in phagocytic and bactericidal capacity of mudskipper MO/MФ in a BpHIF-1α-dependent manner. BpHIF-1α induced an anti-inflammatory status in MO/MФ upon E. tarda infection and hypoxia. Therefore, BpHIF-1α may play a predominant role in the modulation of mudskipper MO/MФ function in the innate immune system.