Cholinergic and adenosinergic systems exert a pro-inflammatory profile in peripheric and splenic lymphocytes of Rhamdia quelen experimentally infected by Aeromonas caviae

Abstract It has been recognized that the cholinergic and adenosinergic systems, through the enzymes acetylcholinesterase (AChE) and adenosine deaminase (ADA), exert an important role in the immune and inflammatory responses during bacterial fish diseases. The immune response against Aeromonas caviae remains poorly understood, and the involvement of these systems, through the anti-inflammatory molecules acetylcholine (ACh) and adenosine (Ado), has not been studied. Thus, the aim of this study was to evaluate the involvement of cholinergic and adenosinergic systems on the inflammatory and immune responses in peripheric and splenic lymphocytes of fish experimentally infected with A . caviae . AChE and ADA activities in peripheric and splenic lymphocytes increased in infected animals on day 4 post-infection compared to uninfected animals, while the ACh and Ado levels decreased. Moreover, spleen histopathology revealed an increase in the number of melano-macrophage centers, as well as lipid inclusions and cellular debris in the ellipsoids. This evidence indicates that infection by A . caviae alters the cholinergic and adenosinergic systems, suggesting the involvement of AChE and ADA activities in the impairment of the immune system, since infection leads to a reduction in ACh and Ado levels, respectively. In summary, the upregulation of AChE and ADA activities in peripheric and splenic lymphocytes exerts a pro-inflammatory profile, contributing to systemic and tissue inflammatory damage, and consequently to disease pathogenesis.