Elucidation of the potential mechanism of punicalagin for conferring disease resistance in Yesso scallops against Vibrio anguillarum infection

Abstract Although punicalagin (PNG) has been demonstrated to exhibit a variety of bioactivities, its disease resistance role in bivalve shellfish remains poorly understood. This study was designed to investigate the effect of PNG on immunoprotective activity in Yesso scallops (Patinopecten yessoensis) infected with Vibrio anguillarum. Surprisingly, PNG exhibited both prophylaxis and curative potential against this pathogen, as indicated by the significant increase in scallop survival rates. Additional in vitro and in vivo experiments were conducted to assess the possible mechanism by which PNG protected against pathogen infection. The results showed that PNG could cause significant damage to the membrane, suggesting that it displayed potent antimicrobial activity against V. anguillarum. At subinhibitory concentrations (SICs), PNG significantly reduced the bacterial swimming ability and inhibited the expression of some essential genes involved in virulence. Bacterial challenge experiments showed that PNG could facilitate the clearance of bacteria from the scallops. Interestingly, hemolymph immune-related enzyme activities significantly increased after PNG treatment. In addition, pre-treatment with PNG suppressed the expression of bacterially-induced immune response genes, indicating that PNG could be applied as an antibacterial drug and immunostimulant to protect pathogen-infected scallops in aquaculture.