ADVANCED GLYCATION ENDPRODUCTS IN NEUROFILAMENT CONGLOMERATION OF MOTONEURONS IN FAMILIAL AND SPORADIC AMYOTROPHIC-LATERAL-SCLEROSIS

Background: Massive neurofilament conglomeration in motor neurons has been described to occur in the early stages of both familial and spora dic amyotrophic lateral sclerosis (ALS). Previously, neurofilament con glomerates were immunolabeled for both superoxide dismutase (SOD1) and nitrotyrosine, suggesting the potential for oxidative nitration damag e to neurofilament protein by peroxynitrite. Long-lived neurofilaments may also undergo modification by advanced glycation endproducts (AGEs ) with concomitant generation of free radicals, including superoxide. This radical species may then react with nitric oxide to form the pote nt oxidant, peroxynitrite, which in turn can nitrate neurofilament pro tein. Such a glycated and nitrated neurofilament protein may become re sistant to proteolytic systems, forming high-molecular-weight protein complexes and cytotoxic, neuronal inclusions. Materials and Methods: P araffin sections containing both neurofilament conglomerates and neuro nal inclusions were obtained from patients with sporadic (n = 5) and f amilial (n = 2) ALS and were probed with specific antibodies directed against the AGEs cypentodine/piperidine-enolone, arginine-lysine imida zole, pentosidine, and pyrraline. Results: Neurofilament conglomerates , but not neuronal inclusions, were intensely immunolabeled with each of the anti-AGE antibodies tested. The immunoreactivity was selective for neurofilament conglomerates and suggested dial AGEs may form inter - or intramolecular cross-links in neurofilament proteins. Conclusions : These data support the hypothesis that AGE formation affects neurofi lament proteins in vivo and is associated with the concomitant inducti on of SOD1 and protein nitration in neurofilament conglomerates. AGE f ormation in neurofilament protein map not only cause covalent cross-li nking but also generate superoxide and block nitric oxide-mediated res ponses, thereby perpetuating neuronal toxicity in patients with ALS.