Inhibitory Effect of Polydatin Against Aeromonas hydrophila Infections by Reducing Aerolysin Production

Abstract

The fast-growing demand for aquatic products has led to the rapid development of aquaculture. However, diseases caused by bacterial pathogens result in severe economic losses all over the world. Although the introduction of antibiotics to aquaculture decreased the mortality of infectious diseases, the emergence of antibiotic resistance caused treatment failure. Therefore, drugs with novel strategies are needed for combatting infections caused by resistant bacterial strains. In the present study, aerolysin was identified as a target for developing drugs from natural compounds against Aeromonas hydrophila (A. hydrophila) infections. We found that polydatin without an inhibitory effect against A. hydrophila growth could decrease the hemolysis mediated by aerolysin. In both western blot and qPCR assays, the addition of polydatin decreased the production of aerolysin by downregulating the aerolysin encoding gene. Moreover, cell viability and animal studies found that polydatin could reduce the pathogenesis of A. hydrophila both in vitro and in vivo. Taken together, these findings provided a novel approach and candidate for treating resistant A. hydrophila infections in aquaculture.

Keywords: Aeromonas hydrophila; aerolysin; anti-virulence; hemolytic activity; polydatin.

Figure 1

Inhibitory effect of polydatin against aerolysin mediated hemolysis. (A) The chemical structure of polydatin. (B) Influence of different concentrations of polydatin on bacterial growth. (C) Reduction of the hemolytic activity of bacterial supernatants co-cultured with indicated concentrations of polydatin. (D) Impact of polydatin on aerolysin production in bacterial supernatants determined by western blot. Data shown in (C) are the mean ± SD of three independent assays, * represented p < 0.05, while ** was p < 0.01.

Figure 2

Effects of polydatin on the expression levels of the aerA gene. Data are represented as the mean ± SD of three independent assays, * indicates p < 0.05, ** indicates p < 0.01.

Figure 3

Polydatin protected A549 cells against aerolysin mediated cell injury. (A–C) were cell viability determined by live/dead staining, (A) live cells without any treatment, (B) cells co-cultured with bacterial supernatant without polydatin treatment, (C) cells co-cultured with bacterial supernatant treated with 8 μg/ml polydatin. (D) Cell injury determined by lactate dehydrogenase (LDH) release assay. Data in (D) are the mean ± SD of three independent assays, ** indicates p < 0.01.

Figure 4

The survival percentage of channel catfish challenged with Aeromonas hydrophila (A. hydrophila) and treated with or without polydatin. The survival rates of each group were analyzed by log-rank test, and the statistical significance (p = 0.0,003) was observed.