PHD1/IKKβ/NF-κB signaling pathway regulates macrophage polarization and is involved in hypoxia-tolerant large yellow croaker (Larimichthys crocea) against Aeromonas hydrophila infection.

Abstract

The hypoxia-tolerant group (T group) large yellow croaker (Larimichthys crocea) exhibits high survival rates when infected with Aeromonas hydrophila. To elucidate the underlying mechanism, this study explored the potential new role of proline hydroxylase domain-containing protein 1 (PHD1) in immunity, and examined the differences in PHD1/IKKβ/NF-κB signaling pathway between the T group and normal group following A. hydrophila challenge. Our results found that LcPhd1 responds to LPS stimulation in head kidney macrophages of L. crocea and affects the phosphorylation of IKKβ and NF-κB nuclear translocation in the classical immune signaling pathway. Co-IP and site-directed mutagenesis further demonstrated that this effect may occur through the modulation of the proline residue in the LXXLAP sequence of LcIKKβ. Additionally, PHD1 inhibited macrophage polarization into the M1 type, including reducing the production of bactericidal substances, such as inflammatory factors, ROS, as well as diminishing the macrophage functions, such as migration, invasion, and phagocytosis. Following A. hydrophila infection, the PHD1 expression in the head kidney of T gorup L. crocea decreased, while IKKβ phosphorylation and p65 nuclear translocation increased. In conclusion, these results indicated that PHD1 may regulate macrophage polarization through the IKKβ/NF-κB signal cascade and contribute to the resistance of T gorup L. crocea to A. hydrophila infection.