Oxidative Damage to Axonal Cytoskeletal Proteins

Abstract Proteins of the axonal cytoskeleton, particularly neurofilament and microtubule-associated protein τ, should be particularly sensitive to the effects of oxidative modification due to their high content of lysine, an amino acid that is particularly susceptible to direct oxidization as well as adduction by carbonyls produced from lipid and sugar oxidation. To understand the susceptibility of the cytoskeleton to oxidative modification and whether such modification is related to the physiological function of the cytoskeleton, we undertook a cytological analysis of motor neurons isolated from mouse spinal cord. These neurons contain an abundant axonal cytoskeleton that can be readily analyzed distinct from the cell body. Immunocytochemistry, using antibodies against protein-adducts of the highly reactive lipid peroxidation product, hydroxynonenal (HNE), representing Michael addition or pyrrole formation, revealed that HNE-immunoreactive adducts are found in all axons. This in situ distribution of HNE-adducts is consistent with immunoblots prepared from axons which show selective HNE modification of neurofilament heavy subunit (NFH) but not of other cytoskeletal proteins.