The immune function of heme oxygenase-1 (HO-1) from Nile tilapia (Oreochromis niloticus) in response to bacterial infection.

Heme oxygenase-1 (HO-1), an inducible rate-limiting metabolic enzyme, exerts critical immunomodulatory functions by potential anti-oxidant, anti-inflammatory, and anti-apoptotic activities. Although accumulative studies have focused on the immune functions of HO-1 in mammals, the roles in fish are poorly understood, and the reports on involvement in the defensive and immune response are very limited. In this study, On-HO-1 gene from Oreochromis niloticus was successfully cloned and identified, which contained an open reading frame (ORF) of 816 bp and coded for a protein of 271 amino acids. The On–HO–1 protein phylogenetically shared a high homology with HO-1 in other teleost fish (76.10%–98.89 %) and a lowly homology with HO-1 in mammals (38.98%–41.55 %). The expression levels of On-HO-1 were highest in the liver of healthy tilapias and sharply induced by Streptococcus agalactiae or Aeromonas hydrophila. Besides, On–HO–1 overexpression significantly increased non-specific immunological parameters in serum during bacterial infection, including LZM, SOD, CAT, ACP, and AKP. It also exerted anti-inflammatory and anti-apoptotic effects in response to the immune response of the infection with S. agalactiae or A. hydrophila by upregulating anti-inflammatory factors (IL-10 , TGF-β), autophagy factors (ATG6 , ATG8) and immune-related pathway factors (P65 , P38), and down-regulating pro-inflammatory factors (IL-1β , IL-6 , TNF-α), apoptotic factors (Caspase3 , Caspase9), pyroptosis factor (Caspase1), and inflammasome (NLRP3). These results suggested that On–HO–1 involved in immunomodulatory functions and host defense in Nile tilapia. • Heme oxygenase-1 (OnHO-1) was cloned from Oreochromis niloticus. • OnHO-1 was induced during Streptococcus agalactiae and Aeromonas hydrophila infection. • OnHO-1 overexpression could improve anti-oxidant activity, and enhance non-specific immunity. [ABSTRACT FROM AUTHOR]