The Journal of Neuroscience, August 1, 1999, 19(15):6468-6474
Gp-41-Mediated Astrocyte Inducible Nitric Oxide Synthase mRNA
Expression: Involvement of Interleukin-1
Production by Microglia
Shuxian
Hu,
Humaira
Ali,
Wen S.
Sheng,
Laura C.
Ehrlich,
Phillip K.
Peterson, and
Chun C.
Chao
Institute for Brain and Immune Disorders, Minneapolis Medical
Research Foundation and the University of Minnesota Medical School,
Minneapolis, Minnesota 55404
Mechanisms underlying human immunodeficiency virus-1 encephalopathy
are not completely known; however, recent studies suggest that the
viral protein gp41 may be neurotoxic via activation of inducible nitric
oxide synthase (iNOS) in glial cells. In the present study, we
investigated the NO-generating activity of primary human fetal
astrocytes in response to gp41 and the relationship to microglial cell
production of interleukin-1 (IL-1). Gp41 failed to trigger iNOS mRNA
expression in highly enriched (>99%) astrocyte or microglial cell
cultures. However, gp41-treated microglia released a factor(s) that
triggered iNOS mRNA expression and NO production in astrocytes. Because
IL-1 receptor antagonist protein blocked gp41-induced NO production, a
pivotal role was suggested for microglial cell IL-1 production in
astrocyte iNOS expression. Also, gp41 induced IL-1
mRNA expression
and IL-1 production in microglial cell but not astrocyte cultures.
Using specific inhibitors, we found that gp41-induced IL-1
production in microglia was mediated via a signaling pathway involving
protein-tyrosine kinase. These data support the hypothesis that gp41
induces astrocyte NO production indirectly by triggering upregulation
of microglial cell IL-1 expression.
Key words:
astrocytes; cytokines; human immunodeficiency virus-1; interleukin-1; microglia; nitric oxide; nitric oxide synthase; protein-tyrosine kinase
Copyright © 1999 Society for Neuroscience 0270-6474/99/19156468-07$05.00/0