Molecular characterization and immune functions of lipasin in Nile tilapia (Oreochromis niloticus): Involvement in the regulation of tumor necrosis factor-α secretion.

Lipasin, the product of the angiopoietin-like 8 (angptl8) gene, is known as a critical regulator of plasma lipid metabolism. However, its immune function in vertebrates is currently poorly understood. By 5'/3′-rapid amplification of cDNA ends (RACE), we established the structural identity of Nile tilapia (Oreochromis niloticus) angptl8. The transcripts of tilapia angptl8 were widely expressed in various tissues, with the highest levels in the liver. Following lipopolysaccharide in vivo challenges, time-dependent angptl8 gene expression was observed in the head kidney and liver. On the basis of the sequence obtained, we produced recombinant lipasin that inhibited lipoprotein lipase activity. Treatment of head kidney leukocytes with lipasin stimulated tumor necrosis factor-α (TNF-α) secretion and gene expression. In addition, lipasin-induced TNF-α secretion could be prevented by inhibiting the nuclear factor-kappa B (NF-κB) signaling pathway. Furthermore, lipasin enhanced the phosphorylation and degradation of IκBα and promoted translocation of the p65 subunit of NF-κB to the nucleus. Collectively, the current findings suggested that lipasin was involved in the immune response of Nile tilapia and stimulated TNF-α secretion by activating the NF-κB pathway in tilapia head kidney leukocytes. • Cloning of tilapia angptl8 and examination of its tissue expression patterns. • The LPS challenge induced the temporal expression of angptl8. • Synthesis of recombinant lipasin and validation of its biological activity. • Lipasin elevated TNF-α secretion and gene expression in head kidney leukocytes. • Lipasin stimulated TNF-α secretion by activating the NF-κB pathway. [ABSTRACT FROM AUTHOR]