INDUCTION OF NITRIC-OXIDE SYNTHASE IN DEMYELINATING REGIONS OF MULTIPLE-SCLEROSIS BRAINS

The amount of messenger RNA encoding human inducible nitric oxide synt hase and the presence and distribution of NADPH diaphorase were determ ined in tissue sections from multiple sclerosis (MS) and control brain s. Levels of human nitric oxide synthase messenger RNA were markedly e levated in MS brains when compared to normal control brains. NADPH dia phorase activity, a histochemical stain reflecting nitric oxide syntha se catalytic activity, was detected in reactive astrocytes in active d emyelinating MS lesions and at the edge of chronic active demyelinatin g lesions. Control brains did not contain NADPH diaphorase-positive as trocytes. These results implicate the free radical nitric oxide in the pathogenesis of demyelinating MS lesions.