title: Nitric oxide production by hemocytes of the ascidian Styela plicata.
abstract: Ascidian hemolymph contains various types of blood cells (hemocytes), which are believed to be involved in defense mechanisms. We have studied nitric-oxide (NO) synthase activity in hemocytes of the ascidian Styela plicata after exposure to lipopolysaccharide (LPS). To investigate which cell types are involved in NO production, we first identified, by electron microscopy, the types of hemocytes previously described, mainly by light microscopy, by others. Five types of blood cells could be recognized in the hemolymph: granulocytes, hemoblasts, lymphocyte-like cells, morula cells, and pigment cells. The lymphocyte-like cells produced the most NO. In agreement with studies of other invertebrates, nitrite generation did not change after LPS stimulation in assays in vitro, under either different concentrations of LPS or different time periods. Therefore, we performed an in vivo assay by injecting a known quantity of Escherichia coli into the tunic of the ascidians in order to investigate possible differences in NO levels. No increase of NO occurred accompanying the inflammatory reaction suggesting that another molecule in the pathway was involved. We found that nuclear factor kappaB (NFkappaB) was activated. Since NFkappaB is involved in the production of many substances related to immune responses, additional molecules might also be generated in response to E. coli infection. These observations may improve our understanding of the reaction of animals to eutrophic conditions.
authors.affiliation: Laboratório de Tecido Conjuntivo, Hospital Universitário Clementino Fraga Filho e Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Cintia Monteiro
authors.initials: CM
authors.lastname: de Barros
authors.forename: Danielle Ronald
authors.initials: DR
authors.lastname: de Carvalho
authors.forename: Leonardo R
authors.initials: LR
authors.lastname: Andrade
authors.forename: Mauro Sérgio G
authors.initials: MS
authors.lastname: Pavão
authors.forename: Silvana
authors.initials: S
authors.lastname: Allodi
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D006434:Hemocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D014561:Urochordata / Q000166:cytology / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D016328:NF-kappa B; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II