Extracellular superoxide dismutase in cultured astrocytes: decrease in cell-surface activity and increase in medium activity by lipopolysaccharide-stimulation

Neurochem Res. 2012 Oct;37(10):2108-16. doi: 10.1007/s11064-012-0832-z. Epub 2012 Jun 28.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Base Sequence
  • Cells, Cultured
  • Culture Media
  • DNA Primers
  • Extracellular Space / enzymology
  • Lipopolysaccharides / pharmacology*
  • Polymerase Chain Reaction
  • RNA, Messenger / genetics
  • Rats
  • Rats, Wistar
  • Superoxide Dismutase / genetics
  • Superoxide Dismutase / metabolism*


  • Culture Media
  • DNA Primers
  • Lipopolysaccharides
  • RNA, Messenger
  • Superoxide Dismutase