Xanthine oxidase activity affects pro-oxidative and pro-inflammatory profiles in spleen of silver catfish experimentally infected with Aeromonas caviae

Several pieces of evidence have linked the involvement of xanthine oxidase (XO), a source of uric acid and reactive oxygen species (ROS), to pro-oxidative and pro-inflammatory effects observed during bacterial fish diseases. Thus, the aim of this study was to evaluate whether upregulation of splenic XO activity contributes to disease pathogenesis of Aeromonas caviae infection, as well as whether it may be considered a pathway involved in ROS and nitric oxide (NO) production. XO activity increased in the spleen of infected animals, as did the splenic levels of uric acid, ROS and metabolites of nitric oxide (NOx), compared to the uninfected control group. Based on this evidence, upregulation of splenic XO activity induces pro-oxidant and pro-inflammatory profiles in the spleen of fish infected by A. caviae due to excessive formation of uric acid. Moreover, excessive uric acid induces the release of pro-inflammatory mediators, such as ROS and NOx, which contribute to disease pathophysiology. In summary, upregulation of XO activity may be considered a pathway involved in ROS and NOx production.