A serum factor enhances production of nitric oxide and tumor necrosis factor-alpha from cultured microglia.
The pathological activation of microglia has been implicated in ischemic neuronal damage and some neurodegenerative diseases; however, the mechanism of microglial activation is not well understood. Previously, we showed that a serum factor, albumin, increased O(2)(-) production by cultured microglia (Si et al., 1997, Glia 21: 413-418). In the present study, we found that serum also enhanced lipopolysaccharide (LPS)-induced production of nitric oxide and tumor necrosis factor-alpha, which are other important neurotoxins released by activated microglia. In the presence of 0.1% normal rat serum, the half-effective concentration for LPS decreased from 300 to 1 ng/ml. The factor seemed to be a relatively high-molecular-weight protein because the factor was retained after a molecular sieve (50 kDa) membrane separation. The factor was labile to trypsinization and heat treatment at 72 degrees C for 5 min but was stable at 56 degrees C for 60 min. Several purified serum proteins including albumin could not mimic the enhancing effect of serum. Acute-phase serum showed a potent enhancing effect at a 10 times lower concentration than the normal serum. By gel filtration chromatography, the enhancing effect observed was a single peak at about 60 kDa. These results suggest that some serum protein infiltrates into brain parenchyma after blood-brain barrier disruption and such protein may result in neuronal damage by activating microglia to release neurotoxins in some central nervous system diseases.
Si
Q
Q
Department of Physiology, Ehime University School of Medicine, Shigenobu, 791-0295, Japan.
Nakamura
Y
Y
Kataoka
K
K
D000818:Animals; D001798:Blood Proteins / Q000737:chemistry / Q000494:pharmacology*; D001812:Blood-Brain Barrier; D001921:Brain / Q000166:cytology; D002478:Cells, Cultured; D002850:Chromatography, Gel; D008070:Lipopolysaccharides; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008970:Molecular Weight; D009410:Nerve Degeneration / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D051381:Rats; D014357:Trypsin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D001798:Blood Proteins; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D014357:Trypsin