Autophagy promotes innate defense against Aeromonas hydrophila in grass carp (Ctenopharyngodon idella) monocytes/macrophages

Abstract

Aeromonas hydrophila (A. hydrophila) is a gram-negative opportunistic pathogen widely distributed in the aquatic environment, which can infect humans, birds, amphibians, reptiles, and fishes. However, the interaction between A. hydrophila and host cells has not been well characterized. In the present study, we investigated the role of autophagy in grass carp (Ctenopharyngodon idella) monocytes/macrophages following infection with A. hydrophila. Our results found that A. hydrophila challenge significantly induced autophagy, as shown by the increase of microtubule-associated protein 1 light chain 3 Ⅱ (LC3 Ⅱ) proteins and LC3 puncta in the cells. Moreover, by using confocal microscopy, the A. hydrophila-elicited autophagy was further confirmed by the colocalization of the A. hydrophila with LC3-positive autophagosome in the cells. In return, the effect of the activated autophagy on the survival of A. hydrophila was examined in the same cell model, showing that rapamycin-induced autophagy was effective in restricting the survival of A. hydrophila. In contrast, autophagy blocked by 3-methyladenine (3-MA) enhanced the amount of A. hydrophila in the cells. All these findings for the first time revealed the role of autophagy in the process of A. hydrophila invading fish immune cells.