Increased expression of neuronal nitric oxide synthase spliced variants in reactive astrocytes of amyotrophic lateral sclerosis human spinal cord

The expression of three different neuronal nitric oxide synthase (nNOS) spliced variants, named nNOS alpha, nNOS beta, and nNOS gamma, was investigated in the spinal cord of control and both familiar and sporadic amyotrophic lateral sclerosis (FALS and SALS) patients. Western blot analysis showed a consistent increase in nNOS expression in six SALS patients compared with controls when antibodies recognizing both nNOS alpha and nNOS beta, or nNOS alpha, nNOS beta, and nNOS gamma were used, whereas no change was observed when a selective anti- nNOS alpha antibody was used. Immunoreactivity signal for nNOS alpha-beta-gamma and nNOS alpha-beta was equally present in ventral horn neurons of control and ALS spinal cord but was dramatically increased in reactive astrocytes of the ventral horn and white matter in both FALS and SALS. nNOS alpha signal was equally expressed in motor neurons of normal and ALS spinal cord but was not evident in astrocytes. This finding indicates that nNOS beta and nNOS gamma spliced variants are upregulated in reactive astrocytes in ALS. This may contribute to the peroxynitrite-mediated oxidative damage involved in the pathogenesis of both FALS and SALS.