Nitric oxide release by hemocytes of the mussel Mytilus galloprovincialis Lmk was provoked by interleukin-2 but not by lipopolysaccharide

As other marine and land mollusks, mussels have special cells in charge of the immune function called hemocytes. The activation of these cells leads to a series of events that end up in phagocytosis and in secretion of digestive enzymes that eliminate the pathogen. The production of nitric oxide is among the early activation processes. Contrary to what happens in cells of vertebrates and of other species of mollusks, in hemocytes of Mytilus galloprovincialis, LPS did not induce secretion of NO to the medium. However, human IL-2 provoked an important increase in NO production. The maximal synthesis of NO was detected after the hemocytes were incubated with the cytokine for 24 h. In both stimulated and non-stimulated cells, Western blotting showed the presence of a protein of 130 kDa, recognized by anti-mouse iNOS. Therefore, the higher production of NO can only be explained as a direct action of some effector upon the nitric oxide synthetase. NO production decreased by the action of H-89, a powerful inhibitor of the cAMP-dependent protein kinase (PKA). This suggests the involvement of PKA in the pathway of NO synthesis. (C) 2003 Elsevier Ltd. All rights reserved.