ASTROCYTES AND MICROGLIA EXPRESS INDUCIBLE NITRIC-OXIDE SYNTHASE IN MICE WITH EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS

Nitric oxide (NO), produced by inducible NO synthase (iNOS), may play a role in inflammatory demyelinating diseases of the central nervous s ystem (CNS). We show upregulation of iNOS mRNA in CNS of SJL/J mice wi th experimental allergic encephalomyelitis (EAE). Using antibodies aga inst mouse iNOS, GFAP (a marker for astrocytes) and Mac-1/CD11b (a mar ker for macrophages/microglia), both astrocytes and macrophages/microg lia were identified as iNOS-expressing cells in situ in EAE lesions. G FAP + astrocytes not associated with inflammatory infiltrates were als o found to express iNOS. Because microglia rather than astrocytes are implicated in demyelinating pathology, we propose that microglial NO m ay be cytopathic whereas astrocyte-derived NO may be protective in EAE .