Adenosine arrests apoptosis in lymphocytes but not in phagocytes from primary leucocyte cultures of the teleost fish, Sparus aurata L.

Adenosine (A) and its derivatives have important biological functions, including the inhibition of immune responses and apoptosis induction. The aim of this work was to investigate whether A and N6-cyclohexyladenosine (CHA) regulate apoptosis in leukocyte cultures from the teleost, gilthead seabream (Sparus aurata L.) by flow cytometry using a double fluorescence staining method. Head kidney leukocytes (HKLs) were cultured for 0, 24 or 48 h. The kinetics of FDA+/PI− (viable), FDA−/PI− (apoptotic) and FDA−/PI+ (necrotic) leukocyte subpopulations were followed during the culture process. Apoptosis was induced by addition of resveratrol or staurosporine to the culture media and the study was validated by transmission electron microscopy. A and CHA did not induce but decreased apoptosis of seabream HKLs, in particular HK lymphocytes (L), after 24 h in culture. Results raise the question whether apoptosis is differently modulated by purine nucleosides in fish L and phagocytes and also in fish compared to mammalian cells.