3-nitrotyrosine and Adrenoleukodystrophy

X-linked adreno-leukodystrophy is a progressive, systemic peroxisomal disorder that affects primarily nervous system myelin and axons as well as the adrenal cortex. Several divergent clinical phenotypes can occur in the same family; thus, there is no correlation between the clinical phenotype and the mutation in the ABCD1 gene in this disease. The most urgent and unresolved clinical issue is the fulminant inflammatory (immune) demyelination of the central nervous system in which a variety of cellular participants, cytokines, and chemokines are noted. A knockout mouse model exhibits mitochondrial deficits and axonal degeneration, but not inflammatory demyelination. To determine whether oxidative stress and damage might play a pathogenic role, we assessed standard biochemical and immunohistochemical markers of such activity both in our knockout mouse model and patients. We find that oxidative stress, as judged by increased immunoreactivity for the mitochondrial manganese-superoxide dismutase, is present in the knockout mouse liver, adrenal cortex, and renal cortex, tissues that normally express high levels of ABCD1 but no evidence of oxidative damage. The brain does not exhibit either oxidative stress or damage. On the other hand, both the human adrenal cortex and brain show evidence of oxidative stress (e.g. hemoxygenase-1 and manganese-superoxide dismutase) and oxidative damage, particularly from lipid peroxidation (4-hydroxynonenal and malondialdehyde). The presence of nitrotyrosylated proteins is strong circumstantial evidence for the participation of the highly toxic peroxynitrite molecule, whereas the demonstration of interferon gamma and interleukin-12 is indicative of a TH1 response in the inflammatory demyelinative lesions of the cerebral phenotype. These differences between the adreno-leukodystrophy mouse and human patients are intriguing and may provide a clue to the phenotypic divergence in this disease.

Topics: Adrenal Cortex; Adrenoleukodystrophy; Animals; Biochemistry; Biomarkers; Brain; Chemokine CCL22; Chemokines, CC; Humans; Immunohistochemistry; Interferon-gamma; Interleukin-12; Kidney Cortex; Liver; Mice; Mice, Knockout; Mitochondria; Oxidative Stress; Superoxide Dismutase; Tyrosine

X-Adrenoleukodystrophy (X-ALD) is an inherited peroxisomal disorder of deficient catabolism of very long-chain (VLC) fatty acids with resulting neuroinflammatory demyelinating disease. Our recent documentation of nitric oxide (NO)-mediated increase in VLC fatty acid levels in glial cells and demonstration of greater increase of VLC fatty acids levels in the inflammatory region (plaque) of X-ALD brain as compared to the normal-looking region away from the plaque prompted us to investigate the possible involvement of NO in the pathophysiology of X-ALD. Herein we provide evidence of the expression of inducible nitric oxide synthase (iNOS) in the CNS of X-ALD patients. In situ hybridization demonstrated that iNOS mRNA was present in brain tissues from X-ALD patients but not in normal controls. Double-labeling immunofluorescence studies using cell-specific markers confirmed that iNOS-expressing cells in the CNS of X-ALD were astrocytes and microglia/macrophages. Finally, antibodies against nitrotyrosine strongly immunoreacted with tissues from the center of the plaque region of X-ALD brains suggesting the presence of the NO reaction product nitrotyrosine in the CNS of X-ALD. Taken together, these results demonstrate that iNOS is expressed in the brains of patients with X-ALD and may contribute to the pathogenesis of the disease.

Topics: Adrenoleukodystrophy; Brain; Fluorescent Antibody Technique; Humans; Immunohistochemistry; In Situ Hybridization; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; RNA, Messenger; Tyrosine