Participation of ecto-5?-nucleotidase in the inflammatory response in an adult zebrafish (Danio rerio) model

The ecto-5 '-nucleotidase is an important source of adenosine in the extracellular medium. Adenosine modulation appears early in evolution and performs several biological functions, including a role as an anti-inflammatory molecule. Here, we evaluate the activity and mRNA expression of ecto-5 '-nucleotidase in response to lipopolysaccharide (LPS) using zebrafish as a model. Adult zebrafish were injected with LPS (10 mu g/g). White blood cell differential counts, inflammatory markers, and ecto-5 '-nucleotidase activity and expression in the encephalon, kidney, heart, and intestine were evaluated at 2, 12, and 24 h post-injection (hpi). At 2 hpi of LPS, an increase in neutrophils and monocytes in peripheral blood was observed, which was accompanied by increased tnf-alpha expression in the heart, kidney, and encephalon, and increased cox-2 expression in the intestine and kidney. At 12 hpi, monocytes remained elevated in the peripheral blood, while tnf-alpha expression was also increased in the intestine. At 24 hpi, the white blood cell differential count no longer differed from that of the control, whereas tnf-alpha expression remained elevated in the encephalon but reduced in the kidney compared with the controls. AMP hydrolysis in LPS-treated animals was increased in the heart at 24 hpi [72 %; p = 0.029] without affecting ecto-5 '-nucleotidase gene expression. These data indicate that, in most tissues studied, inflammation does not affect ecto-5 '-nucleotidase activity, whereas in the heart, a delayed increase in ecto-5 '-nucleotidase activity could be related to tissue repair.