Cinnamaldehyde exerts prophylactic and therapeutic effects against Vibrio anguillarum infection in Yesso scallop (Patinopecten yessoensis) by its direct antimicrobial activity and positive effect on the innate immunity

Abstract

This study investigated the antimicrobial mechanism and immunoprotection of cinnamaldehyde (CNA) against Yesso scallop (Patinopecten yessoensis) pathogen Vibrio anguillarum (V. anguillarum). The results showed that V. anguillarum cells treated with CNA displayed an increased uptake of 1-N-phenylnaphthylamine and propidium iodide, as well as distinct morphological changes, which was indicative of its potent antibacterial activity against V. anguillarum via a membrane-active mechanism to kill the bacteria. Biosafety analysis showed that CNA exhibited no adverse effects on the hemocytes under the test concentrations. Most importantly, pre-treating, co-treating, and post-treating the scallop with CNA significantly increased the survival rate of the scallop after the injection of V. anguillarum. In vivo functional analysis further demonstrated that CNA could promote the clearance of bacteria in hemolymph. Further examination revealed that CNA had a significantly positive effect on the hemolymph immune parameters, contributing to the scallop's immune defense against pathogenic infections. In addition, CNA modulated the expressions of immune-associated genes like PGRP, Toll, NFκB, Defensin, Lysozyme, GPx, and Cu/Zn SOD as analyzed by a Real-Time PCR approach. Furthermore, it is interesting to note that pre-treatment with CNA mitigated a series of V. anguillarum-induced genes known to be responsible for antibacterial and anti-oxidant reactions. These results suggested that CNA exhibited potential for development as a new antibacterial strategy to combat scallop bacterial infections in aquaculture.