Hypoxia-inducible factor-1α involves in regulating anti-lipopolysaccharide factors expression via NF-κB under hypoxia stress in Chinese mitten crab (Eriocheir sinensis)

Abstract

Oxygen is essential for the survival of organisms. Hypoxia profoundly affects the immune response in aquatic crustaceans, nevertheless, the precise mechanisms of immunological regulation under hypoxic conditions remain unclear. Hypoxia-inducible factor 1-alpha (HIF-1α), a key regulator of oxygen homeostasis, also plays a vital role in the immunological responses of mammals. Nonetheless, it remains uncertain whether HIF-1α regulates the immune response of crustaceans under hypoxia stress. This study investigated the expression patterns of EsHIF-1α and anti-lipopolysaccharide factors (ALFs) in response to Aeromonas hydrophila stimulation under hypoxia stress in Eriocheir sinensis. The mRNA expression levels of EsHIF-1α in haemocytes were significantly increased after hypoxia treatment, while were markedly reduced following A. hydrophila stimulation under hypoxic condition. Similarly, the EsALFs mRNA expression levels were also significantly decreased post A. hydrophila injection under hypoxic condition. Subsequently, the effect of EsHIF-1α on EsALFs mRNA expression was detected. The mRNA transcripts of EsALFs significantly diminished in HIF-1α inhibitor (KC7F2) injected crabs, however, a significant increase was observed in HIF-1α activator (IOX4) injected crabs. Furthermore, the mRNA expression and phosphorylation levels of NF-κB exhibited a similar trend following the inhibition or activation of EsHIF-1α, indicating that EsHIF-1α has a positive effect on the expression and activity of NF-κB. In addition, the bacterial clearance of haemolymph in the HIF-1α activated group was significantly higher, whereas in the HIF-1α inhibited group it was significantly lower, compared to the control group. Our findings collectively suggested that EsHIF-1α regulated ALFs expression through NF-κB activation in E. sinensis in response to A. hydrophila stimulation under hypoxic conditions. This research improves the understanding of the immunological regulation mechanisms in crustaceans under hypoxia stress.