Ja. Hewett et al., Inducible nitric oxide synthase expression in cultures enriched for matureoligodendrocytes is due to microglia, J NEUROSC R, 56(2), 1999, pp. 189-198
Expression of inducible nitric oxide (NO) synthase (NOS-2) occurs during in
flammation in the central nervous system (CNS) and has been linked to demye
lination accompanying certain CNS inflammatory diseases. Although astrocyte
s and microglia are thought to be the major sources of NOS-2 expression in
the CNS in vivo, recent evidence suggested that the myelin-producing oligod
endrocytes (OLs) themselves can express NOS-2 in culture. Given the potenti
ally important pathological implications of this finding, the purpose of th
is study was to examine further the expression of NOS-2 by OLs in vitro. Af
ter exposure to lipopolysaccharide (LPS) and interferon-gamma (IFN gamma),
primary cultures enriched for mature OLs released NO in a time-dependent ma
nner, although the amount varied considerably between different culture pre
parations, Increased NO production was accompanied by expression of NOS-2 m
RNA and protein, as determined by reverse transcriptase-polymerase chain re
action (RT-PCR) and Western blot analysis, respectively. Immunoflourescence
analysis revealed that the cell-type expressing NOS-2 in these cultures wa
s galactocerebroside (Gal C)-negative but CD11b-positive. Further, NO produ
ction could be attenuated in cultures treated with the microglial/macrophag
e toxin, leucine methyl ester, prior to LPS/IFN gamma stimulation. Thus, mi
croglia were the source of NOS-2 catalytic activity in these cultures, The
present results indicate that LPS and IFN gamma are not effective stimuli f
or induction of NOS-2 in OLs in primary cell culture. J, Neurosci, Res. 56:
189-198, 1999, (C) 1999 Wiley-Liss, Inc.