Induction of cytosolic NADPH-diaphorase/nitric oxide synthase in reactive microglia/macrophages after quinolinic acid lesions in the rat striatum: an electron and light microscopical study.
Induction of nitric oxide synthase and increased production of nitric oxide in microglia may play a crucial role in neuronal damage and neurodegenerative disorders. In the present study we have used light and electron microscopical NADPH-diaphorase histochemistry as the visualization procedure for nitric oxide synthase to investigate the time-course and subcellular patterns of NADPH-diaphorase expression in microglia/macrophages of quinolinic acid-lesioned rat striatum. For light microscopy, NADPH-diaphorase histochemistry sections were stained with nitroblue tetrazolium, while for ultrastructural analysis the tetrazolium salt 2-(2'-benzothiazolyl)-5-styryl-3(4'-phthalhydrazidyl) tetrazolium chloride (BSPT) was applied. Light microscopical inspection revealed a progressively increasing number of positive cells with increasing intensity of NADPH-diaphorase staining in microglia/macrophages from day 1 after quinolinic acid injection onward. Electron microscopical examination revealed a membrane bound NADPH-diaphorase in quiescent microglia as well as in activated microglia/macrophages through all stages of the lesion studied. Predominantly membranes of the nuclear envelope and the endoplasmic reticulum were labeled with BSPT-formazan, while in advanced stages selective membrane portions of mitochondria, Golgi apparatus and plasmalemma were also stained. From day 5 onward after lesion induction, a very distinctive type of NADPH-diaphorase was observed, forming accumulations of electron-dense grains that were distributed differentially throughout cytoplasmic areas and phagocytic vacuoles. Dynamics of expression, unique cytosolic localization and occurrence exclusively in activated microglia/macrophages suggest that this particular NADPH-diaphorase activity probably reflects the inducible isoform of nitric oxide synthase, whereas the membrane-bound precipitate may represent the neuronal and/or the endothelial isoform of the enzyme.
Calka
J
J
Otto von Guericke University of Magdeburg, Germany.
Wolf
G
G
Schmidt
W
W
D000818:Animals; D003342:Corpus Striatum / Q000166:cytology / Q000201:enzymology* / Q000473:pathology; D003600:Cytosol / Q000201:enzymology*; D008264:Macrophages / Q000201:enzymology*; D008297:Male; D017628:Microglia / Q000201:enzymology*; D008853:Microscopy; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D017378:Quinolinic Acid / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase; D017378:Quinolinic Acid