title: NADPH-oxidase activity: the probable source of reactive oxygen intermediate generation in hemocytes of the gastropod Lymnaea stagnalis.
abstract: Macrophage-like defense cells (hemocytes) of the pond snail Lymnaea stagnalis generate reactive oxygen intermediates (ROIs) upon contact with non-self, following kinetics similar to those of ROI production by mammalian leukocytes during respiratory burst. In this study, several inhibitors of NADPH-oxidase, the key enzyme of the respiratory burst in mammalian phagocytes, were tested for their effect on oxidative activities [as demonstrated by nitroblue tetrazolium (NBT) reduction and luminol-dependent chemiluminescence (LDCL)] of phagocytosing snail hemocytes. In the presence of diphenylene iodonium, zymosan-stimulated hemocytes of L. stagnalis failed to reduce NBT and showed a markedly reduced LDCL response. Also, compounds that prevent assembly of functional NADPH-oxidase complexes in activated mammalian cells were effective; preincubation of hemocytes with 1,4-naphthoquinone inhibited the LDCL response and NBT reduction upon phagocytic stimulation. Furthermore, coincubation but not preincubation with five different catechol-like phenols inhibited oxidative activities of zymosan-stimulated hemocytes. These results imply similarities in composition and regulation of the ROI-generating mechanisms of both mammalian and snail defense cells. It is postulated that in L. stagnalis hemocytes, (1) NADPH-oxidase activity is responsible for ROI production, (2) an active NADPH-oxidase enzyme complex has to be assembled from putative cytosolic and membrane-associated components, and (3) continuous replacement of active NADPH-oxidase enzyme complexes is necessary to sustain respiratory burst-like oxidative activities during interactions with non-self.
authors.affiliation: Department of Medical Microbiology and Parasitology, Faculty of Medicine, Vrije Universiteit Amsterdam, The Netherlands.
authors.forename: C M
authors.initials: CM
authors.lastname: Adema
authors.forename: E C
authors.initials: EC
authors.lastname: van Deutekom-Mulder
authors.forename: W P
authors.initials: WP
authors.lastname: van der Knaap
authors.forename: T
authors.initials: T
authors.lastname: Sminia
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D002396:Catechols / Q000494:pharmacology; D006434:Hemocytes / Q000166:cytology / Q000378:metabolism*; D008163:Luminescent Measurements; D008165:Luminol; D008195:Lymnaea / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019255:NADPH Oxidases; D009285:Naphthoquinones / Q000494:pharmacology; D009580:Nitroblue Tetrazolium; D009861:Onium Compounds / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016897:Respiratory Burst / Q000502:physiology; D015054:Zymosan / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D002396:Catechols; D009285:Naphthoquinones; D009861:Onium Compounds; D017382:Reactive Oxygen Species; D009580:Nitroblue Tetrazolium; D008165:Luminol; C007517:diphenyleneiodonium; D015054:Zymosan; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C034221:catechol