title: Extracellular superoxide dismutase in cultured astrocytes: decrease in cell-surface activity and increase in medium activity by lipopolysaccharide-stimulation.
abstract: Under pathological conditions such as ischemia/reperfusion, a large amount of superoxide anion (O(2) (-)) is produced and released in brain. Among three isozymes of superoxide dismutase (SOD), extracellular (EC)-SOD, known to be excreted outside cells and bound to extracellular matrix, should play a role to detoxify O(2) (-) in extracellular space; however, a little is known about EC-SOD in brain. In order to evaluate the SOD activity in extracellular space of CNS as direct as possible, we attempted to measure the cell-surface SOD activity on primary cultured rat brain cells by the inhibition of color development of a water-soluble tetrazolium due to O(2) (-) generation by xanthine oxidase/hypoxanthine added into extracellular medium of intact cells. The cell-surface SOD activity on cultured neuron and microglia was below the detection limit; however, that on cultured astrocyte was high enough to measure. By means of RT-PCR, all mRNA of three isozymes of SOD could be detected in the three types of the cells examined; however, the semi-quantitative analysis revealed that the level of EC-SOD mRNA in astrocytes was significantly higher than that in neurons and microglia. When astrocytes were stimulated with lipopolysaccharide (LPS) for 12-24 h, the cell-surface SOD activity decreased to a half, whereas the activity recovered after 36-48 h. The decrease in the activity was dependent on the LPS concentration. On the other hand, the SOD activity in the medium increased by the LPS-stimulation in a dose dependent manner; suggesting that the SOD protein localized on cell-surface, probably EC-SOD, was released into the medium. These results suggest that EC-SOD of astrocyte play a role for detoxification of extracellular O(2) (-) and the regulation of EC-SOD in astrocytes may contribute to the defensive mechanism against oxidative stress in brain.
authors: Laboratory of Integrative Physiology in Veterinary Science, Osaka Prefecture University, Rinku-ourai Kita 1-58, Izumisano, Osaka 598-8531, Japan.
authors: Ichiro
authors: I
authors: Iitsuka
authors: Akiko
authors: A
authors: Motoyoshi-Yamashiro
authors: Mitsuaki
authors: M
authors: Moriyama
authors: Yukiko
authors: Y
authors: Kannan-Hayashi
authors: Yuka
authors: Y
authors: Fujimoto
authors: Katsura
authors: K
authors: Takano
authors: Koji
authors: K
authors: Murakami
authors: Yukio
authors: Y
authors: Yoneda
authors: Yoichi
authors: Y
authors: Nakamura
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001483:Base Sequence; D002478:Cells, Cultured; D003470:Culture Media; D017931:DNA Primers; D005110:Extracellular Space / Q000201:enzymology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: D003470:Culture Media; D017931:DNA Primers; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D013482:Superoxide Dismutase