In vitro production of superoxide and nitric oxide (as nitrite and nitrate) by Mytilus galloprovincialis haemocytes upon incubation with PMA or laminarin or during yeast phagocytosis

The phagocytic process is one of the most important elements of the self-de fence system in mammals as well as in molluscs. In mammalian phagocytes, su peroxide participates in the innate defence system by combining with nitric oxide to generate peroxynitrite, a strong oxidant that possesses highly cy totoxic properties against bacteria. To evidence a role of nitric oxide in the self-defence system of the marine bivalve Mytilus galloprovincialis similar to the role observed in the mamm alian defence system, we measured the generation of superoxide and nitrite/ nitrate (the stable end products of nitric oxide) upon in vitro stimulation of M. galloprovincialis haemocytes with PMA, laminarin, LPS and by phagocy tosis of Saccharomyces cerevisiae (yeast cells). We show that stimulation w ith PMA, laminarin and yeast cell phagocytosis promotes superoxide and nitr ite/nitrate generation from M. galloprovincialis haemocytes, Inhibitors of NADPH oxidase and inhibitors of NO synthase decreased the nitrite/nitrate l evels generated by M. galloprovincialis haemocytes showing that both NADPH oxidase and NO synthase pathways are involved in the self-defence system of M. galloprovincialis.