Purinergic system displays an anti-inflammatory profile in serum of silver catfish experimentally infected with Streptococcus agalactiae: An attempt to ameliorate the inflammatory response.

The purinergic system is recognized to modulate extracellular adenosine triphosphate (ATP) and related nucleotides through the activities of triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase, and adenosine deaminase (ADA), thereby playing an essential role in the immunoregulation of inflammatory and immune responses. Thus, the aim of this study was to evaluate whether the purinergic system can improve the inflammatory response in fish experimentally infected with Streptococcus agalactiae through the modulation of seric NTPDase, 5'-nucleotidase and ADA activities. Seric NTPDase (ATP as substrate) and 5'-nucleotidase activities increased in silver catfish experimentally infected with S. agalactiae compared with the uninfected control group, while seric ADA activity decreased. Based on this evidence, our findings suggest that regulation of adenine nucleotide hydrolysis occurs in an attempt to restrict the inflammatory process and improve the immune system by hydrolyzing excess extracellular ATP. On the other hand, downregulation of seric ADA activity may be an attempt to augment extracellular adenosine (a molecule with anti-inflammatory effects) levels. In summary, the purinergic system is capable of modulating the immune and inflammatory responses during fish streptococcosis.