Cytokine-stimulated astrocytes damage human neurons via a nitric oxide mechanism.
Astrocytes have been reported to play a neuropathogenic role within the brain, although little is known about the mechanism underlying astrocyte-mediated neuronal injury. We investigated the hypothesis that cytokine-stimulated astrocytes adversely affect neuronal cell survival via generation of the free radical nitric oxide (NO). Primary human astrocytes produced substantial amounts of NO in response to interleukin (IL)-1 alpha or IL-1 beta, which was blocked by the NO synthase inhibitor NG-mono-methyl-L-arginine (NMMA). IL-1 beta-induced NO production was markedly potentiated by interferon (IFN)-gamma. IL-1 receptor agonist protein (IRAP) totally blocked NO generation by cytokine-stimulated astrocytes. Using reverse transcription-polymerase chain reaction and sequencing analyses of the astrocyte NO synthase gene, we found a single band encoding for a 615 bp product that was identical to the corresponding sequence reported for human hepatocytes. Treatment of human fetal brain cell cultures with IL-1 beta plus IFN-gamma resulted in marked neuronal loss, as assessed by microscopic analysis and measurement of lactate dehydrogenase release. This cytokine-induced neuronal damage was blocked by simultaneous treatment of the brain cell cultures with NMMA or IRAP, suggesting a critical role of IL-1. These findings indicate that cytokine-stimulated astrocytes are neurotoxic via a NO-mediated mechanism and point to potential new therapies for neurodegenerative disorders that involve cytokines and reactive astrocytes.
Chao
C C
CC
Neuroimmunobiology and Host Defense Laboratory, Minneapolis Medical Research Foundation, the Department of Medicine, Hennepin County Medical Center, Minnesota 55404, USA.
Hu
S
S
Sheng
W S
WS
Bu
D
D
Bukrinsky
M I
MI
Peterson
P K
PK
D001253:Astrocytes / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004790:Enzyme Induction; D005333:Fetus; D006801:Humans; D008969:Molecular Sequence Data; D009474:Neurons / Q000473:pathology*; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins
D016207:Cytokines; D012333:RNA, Messenger; D011994:Recombinant Proteins; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase