Inducible nitric oxide synthase immunoreactivity in the Alzheimer disease hippocampus: Association with Hirano bodies, neurofibrillary tangles, and senile plaques

Inducible nitric oxide synthase (iNOS) is involved in the generation of nit ric oxide, a molecule with multiple biological activities. Although iNOS ex pression may be part of antimicrobial armamentarium, inappropriate expressi on of iNOS can potentially lead to damage to the host. In this report, we d etermined the expression of iNOS by immunocytochemistry in the hippocampus of the Alzheimer brains (AD) as well as in young and old normal brains. The results showed localization of iNOS immunoreactivity to Hirano bodies of t he AD hippocampus. In addition, small granular iNOS immunoreactive profiles were detected associated with senile plaques and extracellular neurofibril lary tangles. In the hippocampus of control brains, morphologically similar profiles were immunoreactive fcr iNOS, but in far fewer numbers than in AD hippocampus. The results suggest that iNOS is expressed in a subset of pyr amidal neurons in the AD hippocampus, and that iNOS may be involved in the pathogenesis of neuronal degeneration in AD.