Showing papers by "Michael T. Lin published in 2009"

Reduction of oxidative stress, amyloid deposition, and memory deficit by manganese superoxide dismutase overexpression in a transgenic mouse model of Alzheimer’s disease

Abstract: In Alzheimer's disease (AD), oxidative stress is present early and contributes to disease pathogenesis. We previously reported that in Tg19959 transgenic AD mice, partial deficiency of the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) exacerbated amyloid pathology. We therefore asked whether MnSOD overexpression would prove beneficial against AD pathogenesis, by studying the offspring of Tg19959 mice crossed with MnSOD-overexpressing mice. At 4 mo of age, there was a 2- to 3-fold increase in MnSOD protein levels in Tg19959-MnSOD mice compared to Tg19959 littermates. Tg19959-MnSOD mice also had a 50% increase in catalase protein levels, a 50% decrease in levels of oxidized protein, and a 33% reduction in cortical plaque burden compared to Tg19959 littermates. Spatial memory was impaired and synaptophysin levels were decreased in Tg19959 mice compared to wild-type littermates, but memory and synaptophysin levels were restored to wild-type levels in Tg19959-MnSOD littermates. These benefits occurred without changes in sodium dodecyl sulfate-soluble or formic acid-soluble Abeta pools or Abeta oligomers in Tg19959-MnSOD mice compared to Tg19959 littermates. These data demonstrate that facilitation of the mitochondrial antioxidant response improves resistance to Abeta, slows plaque formation or increases plaque degradation, and markedly attenuates the phenotype in a transgenic AD mouse model.

Synaptic activity reduces intraneuronal Aβ, promotes APP transport to synapses and protects against Aβ-related synaptic alterations

Abstract: A central question in Alzheimer's disease research is what role synaptic activity plays in the disease process. Synaptic activity has been shown to induce beta-amyloid peptide release into the extracellular space, and extracellular beta-amyloid has been shown to be toxic to synapses. We now provide evidence that the well established synaptotoxicity of extracellular beta-amyloid requires gamma-secretase processing of amyloid precursor protein. Recent evidence supports an important role for intraneuronal beta-amyloid in the pathogenesis of Alzheimer's disease. We show that synaptic activity reduces intraneuronal beta-amyloid and protects against beta-amyloid-related synaptic alterations. We demonstrate that synaptic activity promotes the transport of the amyloid precursor protein to synapses using live cell imaging, and that the protease neprilysin is involved in reduction of intraneuronal beta-amyloid with synaptic activity.

Triterpenoid CDDO–methylamide improves memory and decreases amyloid plaques in a transgenic mouse model of Alzheimer’s disease

Abstract: Oxidative stress is one of the earliest events in the pathogenesis of Alzheimer's disease (AD) and can markedly exacerbate amyloid pathology. Modulation of antioxidant and anti-inflammatory pathways represents an important approach for AD therapy. Synthetic triterpenoids have been found to facilitate antioxidant response and reduce inflammation in several models. We investigated the effect of the triterpenoid, 2-Cyano-3,12-Dioxooleana-1,9-Dien-28-Oic acid-MethylAmide (CDDO-MA) in Tg19959 mice, which carry the human amyloid precursor protein with two mutations. These mice develop memory impairments and amyloid plaques as early as 2-3 months of age. CDDO-MA was provided with chow (800 mg/kg) from 1 to 4 months of age. CDDO-MA significantly improved spatial memory retention and reduced plaque burden, Aβ42 levels, microgliosis, and oxidative stress in Tg19959 mice.