The present study was performed to determine the effects of Aeromonas hydrophila
infection on intestinal -histopathology, innate immune response and changes in
antioxidant capacity of blunt snout bream (Megalobrama amblycephala). A series of histopathological changes, innate immune
enzyme activities,
antioxidant enzyme activities, and the corresponding
mRNA relative genes expressions in intestines were measured at 0, 1, 2, and 3 weeks post-treatment of Aeromonas hydrophila (1✕107 CFU mL-1)
infection. The results showed that Aeromonas hydrophila induced changes in intestinal morphology, including the decreased muscularis thickness, the proliferated goblet cells, and the atrophied intestine villi height. Moreover, the innate immune
enzymes activities in serum such as
acid phosphatase,
alkaline phosphatase,
lysozyme activities and
immunoglobulin M were significantly reduced after
infection at 1week, 2week and 3week. The contents of
complement 3 and
complement 4 were significantly decreased after
infection as well. In addition, the
antioxidant enzymes activities, including
superoxide dismutase,
catalase and
glutathione peroxidase in the experimental groups were significantly decreased compared with the control group, whereas the content of
malondialdehyde was significantly increased after
infection at 1week, 2week and 3week. Furthermore, the
mRNA relative expressions of the inflammatory
cytokines such as
tumor necrosis factor-α, interleukins-1β,
interferon-γ, and interleukins-6 were significantly increased after
infection with Aeromonas hydrophila. The TJ-related gene expressions in the intestine of zonula occluden-1,
occludin, occludin-1, occludin-2 were significantly reduced throughout the
infection period. The
mRNA relative expressions of signal transducers and activators of transcription 4 and janus kinase-3 in the intestine were significantly ascended compared with the non-infected group. Overall, the results elucidated that the intestine tissue injury and innate immune response reduction, as well as
antioxidant capacity attenuation were occurred against Aeromonas hydrophila
infection of the blunt snout bream.