2-nonenal--(trans)-isomer and Disease-Models--Animal

Oxidative damage and amyloid-β (Aβ) protein misfolding are prominent features of Alzheimer's disease (AD). In vitro studies indicated a direct linkage between these two features, where lipid oxidation products augmented Aβ misfolding. We tested this linkage further, mimicking specific conditions present in amyloid plaques. In vitro lipid oxidation and lipid modification of Aβ were thus performed with elevated levels of copper or physiological levels of calcium. These in vitro experiments were then confirmed by in vivo immunohistochemical and chemical tagging of oxidative damage in brains from the PSAPP mouse model of AD. Our in vitro findings indicate that: 1) high levels of copper prevent lipid oxidation; 2) physiological concentrations of calcium reduce 4 hydroxy-2-nonenal (HNE) modification of Aβ; and 3) anti-Aβ and HNE antibody epitopes are differentially masked. In vivo we demonstrated increased lipid oxidation around plaques but 4) a lack of immunological colocalization of HNE-adducts with Aβ. Thus, the lack of colocalization of Aβ and HNE-adduct immunostaining is most likely due to a combination of metals inhibiting HNE modification of Aβ, quenching lipid oxidation and a masking of HNE-Aβ histopathology. However, other forms of oxidative damage colocalize with Aβ in plaques, as demonstrated using a chemical method for identifying oxidative damage. Additionally, these findings suggest that HNE modification of Aβ may affect therapeutic antibodies targeting the amino terminal of Aβ and that metals effect on lipid oxidation and lipid modification of Aβ could raise concerns on emerging anti-AD treatments with metal chelators.

Topics: Aldehydes; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Calcium; Copper Sulfate; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Humans; Lipid Bilayers; Lipid Metabolism; Lipid Peroxidation; Male; Mice; Mice, Transgenic; Mutation; Oxidation-Reduction; Peptide Fragments; Plaque, Amyloid; Presenilin-1; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The benefits of estrogen replacement as a preventative treatment for Alzheimer's disease (AD) are subject to debate. Because the effects of estrogen depletion and replacement on accumulation of the neurotoxic beta-amyloid (A beta) peptide in transgenic animal models of AD have been variable, we examined A beta levels and oxidative stress in a nontransgenic animal model. Sheep have traditionally been used as a model for human reproduction; however because they share 100% sequence homology with the human form of A beta, they may also have potential as a nontransgenic model for A beta biology. The effect of ovariectomy and estrogen replacement administered for 6 months via slow-release implant was examined in the brain of 4.5-yr-old sheep. A beta levels were measured by ELISA, and protein levels of the amyloid precursor protein (APP), APP C-terminal fragments (C100), and presenilin-1 were examined semiquantitatively by Western blot as markers of APP processing. Markers of oxidative stress were examined semiquantitatively by Western blot [4-hydroxy-2(E)-nonenal] and oxyblot (protein carbonyls). We found no effects of estrogen depletion and supplementation in terms of AD-related biochemical markers, including A beta levels, APP processing, and oxidative stress levels. Evidence of a trend toward increased P450 side-chain cleavage enzyme levels in the hippocampus of ovariectomized and estrogen supplemented sheep suggests that neurosteroidogenesis may compensate for gonadal estrogen depletion; however, these findings cannot explain the lack of effect of estrogen supplementation on APP processing. It is possible that supraphysiological doses of estrogen are necessary to yield antiamyloidogenic and antioxidative benefits in ovariectomized sheep.

Topics: Aldehydes; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Brain; Cholesterol Side-Chain Cleavage Enzyme; Disease Models, Animal; Estradiol; Estrogen Replacement Therapy; Female; Frontal Lobe; Hippocampus; Ovariectomy; Oxidative Stress; Presenilin-1; Protein Carbonylation; Sheep