Involvement of xanthine oxidase activity with oxidative and inflammatory renal damage in silver catfish experimentally infected with Streptococcus agalactiae: Interplay with reactive oxygen species and nitric oxide.

Xanthine oxidase (XO) is a final enzyme of purine metabolism linked with initiation and progression of infectious diseases, since is considered an important source of reactive oxygen species (ROS) and nitric oxide (NO), developing a pro-oxidant and pro-inflammatory profile in some infectious diseases. Thus, the aim of this study was to evaluate the involvement of XO activity in the renal oxidative and inflammatory damage, as well as the interplay with ROS and metabolites of nitric oxide (NOx) levels in silver catfish experimentally infected with Streptococcus agalactiae. Xanthine oxidase activity, and uric acid, ROS and NOx levels increased in renal tissue of infected animals compared to uninfected animals. Moreover, the histopathological analyses revealed the presence of necrosis, generalized edema and nuclear degeneration of renal tubules. Based on these evidences, the upregulation on renal XO activity exerts a pro-oxidant and pro-inflammatory profile in kidney of fish infected with S. agalactiae. The excessive uric acid levels induced the release of oxidative and inflammatory mediators, such as ROS and NOx, that directly contribute to renal oxidative and inflammatory damage. In summary, the upregulation on XO activity may be considered a pathway involved in the renal injury during S. agalactiae infection.