Characterization of grass carp (Ctenopharyngodon idella) beta-defensin 1: implications for its role in inflammation control.

Considering that fish grows in a complex aquatic environment, there is an increasing interest in fish β-defensins, which is an important group of antimicrobial peptides (AMPs). In this study, grass carp (Ctenopharyngodon idella) β-defensin 1 (gcdefb1) was isolated using homology cloning technology. Tissue distribution assay showed that gcdefb1 transcripts were expressed with the highest levels in brain and liver, followed by some mucous tissues. To examine gcDefb1 bioactivities, the recombinant gcDefb1 proteins fused with thioredoxin tag protein (Trx) (Trx-Defb1) were induced for production in Escherichia coli Rosetta-gami2(DE3)pLysS under optimal expression conditions. The antibacterial activity of Trx-Defb1 against Aeromonas hydrophila was assessed and its minimum inhibitory concentration (MIC) was 36 μM. Interestingly, Trx-Defb1 significantly inhibited LPS-induced Tnf-α (gcTnf-α) secretion and nitric oxide production in grass carp head kidney monocytes/macrophages (HKM), although Trx-Defb1 alone had no effect. Our studies provide the first evidence of fish β-defensin 1 engaging in both antimicrobial and inflammation suppression process.