Alzheimer's disease (AD) is neuropathologically characterized by depositions of extracellular amyloid and intracellular neurofibrillary tangles, associated with loss of neurons in the brain. Amyloid b-peptide (Ab) is the major component of senile plaques and is considered to have a causal role in the development and progress of AD. Several lines of evidence suggest that enhanced oxidative stress and inflammation play important roles in the pathogenesis or progression of AD. The present study aimed to investigate the protective effects of ethyl-4-hydroxy-3-methoxycinnamic acid (FAEE), a phenolic compound which shows antioxidant and anti-inflammatory activity, on Ab(1-42)-induced oxidative stress and neurotoxicity. We hypothesized that the structure of FAEE would facilitate radical scavenging and may induce protective proteins. Ab(1-42) decreases cell viability, which was correlated with increased free radical formation, protein oxidation (protein carbonyl, 3-nitrotyrosine), lipid peroxidation (4-hydroxy-2-trans-nonenal) and inducible nitric oxide synthase. Pre-treatment of primary hippocampal cultures with FAEE significantly attenuated Ab(1-42)-induced cytotoxicity, intracellular reactive oxygen species accumulation, protein oxidation, lipid peroxidation and induction of inducible nitric oxide synthase. Treatment of neurons with Ab(1-42) increases levels of heme oxygenase-1 and heat shock protein 72. Consistent with a cellular stress response to the Ab(1-42)-induced oxidative stress, FAEE treatment increases the levels of heme oxygenase-1 and heat shock protein 72, which may be regulated by oxidative stresses in a coordinated manner and play a pivotal role in the cytoprotection of neuronal cells against Ab(1-42)-induced toxicity. These results suggest that FAEE exerts protective effects against Ab(1-42) toxicity by modulating oxidative stress directly and by inducing protective genes. These findings suggest that FAEE could potentially be of importance for the treatment of AD and other oxidative stress-related diseases. Keywords: amyloid b-peptide, ferulic acid ethyl ester, heat shock protein, heme oxygenase-1, inducible nitric oxide synthase, oxidative stress. Alzheimer's disease (AD) is neuropathologically characterized by depositions of extracellular amyloid and intracellular neurofibrillary tangles, associated with loss of neurons in the brain (Cotman 1998;Masliah 1998;Yankner 2000). Amyloid b-peptide (Ab) is the major component of senile plaques and is considered to have a causal role in the development and progress of AD (Butterfield 2002;Mattson and Mattson 2002). This hydrophobic polypeptide, consisting of 39-43 amino acid residues, is proteolytically produced by b-and c-secretases from a single transmembrane polypeptide collectively referred to as amyloid precursor protein (Sinha and Received August 31, 2004; revised manuscript received September 30, 2004; accepted September 30, 2004. Address correspondence and reprint requests to Prof. D. Allan Butterfield, Department of Chemistry, Center of...

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Tricyclodecan-9-yl-xanthogenate (D609) is an inhibitor of phosphatidylcholine-specific phospholipase C, and this agent also has been reported to protect rodents against oxidative damage induced by ionizing radiation. Previously, we showed that D609 mimics glutathione (GSH) functions and that a disulfide is formed upon oxidation of D609 and the resulting dixanthate is a substrate for GSH reductase, regenerating D609. Considerable attention has been focused on increasing the intracellular GSH levels in many diseases, including Alzheimer's disease (AD). Amyloid beta-peptide [Abeta(1-42)], elevated in AD brain, is associated with oxidative stress and toxicity. The present study aimed to investigate the protective effects of D609 on Abeta(1-42)-induced oxidative cell toxicity in cultured neurons. Decreased cell survival in neuronal cultures treated with Abeta(1-42) correlated with increased free radical production measured by dichlorofluorescein fluorescence and an increase in protein oxidation (protein carbonyl, 3-nitrotyrosine) and lipid peroxidation (4-hydroxy-2-nonenal) formation. Pretreatment of primary hippocampal cultures with D609 significantly attenuated Abeta(1-42)-induced cytotoxicity, intracellular ROS accumulation, protein oxidation, lipid peroxidation and apoptosis. Methylated D609, with the thiol functionality no longer able to form the disulfide upon oxidation, did not protect neuronal cells against Abeta(1-42)-induced oxidative stress. Our results suggest that D609 exerts protective effects against Abeta(1-42) toxicity by modulating oxidative stress. These results may be of importance for the treatment of AD and other oxidative stress-related diseases.

Alzheimer's disease is a neurodegenerative disorder associated with aging and cognitive decline. Amyloid beta peptide (1-42) [Aβ(1-42)] is a primary constituent of senile plaques-a hallmark of Alzheimer's disease-and has been implicated in the pathogenesis of the disease. Previous studies have shown that methionine residue 35 of Aβ(1-42) may play a critical role in Aβ(1-42)-mediated oxidative stress and neurotoxicity. Several additional mechanisms of neurotoxicity have been proposed, including the role of Cu(II) binding and reduction to produce hydrogen peroxide and the role of peptide aggregation. It has been reported that rodent Aβ is less likely to form larger β-sheet structures, and consequently, large aggregates. As a consequence of the lack of deposition of the peptide in rodent brain, rodent Aβ has been proposed to be non-toxic. Additionally, the sequence of the rodent variety of Aβ(1-42) contains three amino acid substitutions compared to the human sequence. These substitutions include the shift of arginine 5, trysosine 10, and histidine 13 to glycine, phenylalanine, and arginine, respectively. This shift in sequence within the Cu(II) binding region of the peptide results in a decrease in the ability of the rodent Aβ peptide to reduce Cu(II) to Cu(I) compared to the human Aβ peptide. As a result of the effect of the amino acid variations on the ability of the rodent peptide to reduce Cu(II) to Cu(I) compared to the human peptide, the rodent Aβ has been proposed to lack oxidative stress properties. In this study, the oxidative stress and neurotoxic properties of rodent Aβ(1-42) [Aβ(1-42)Rat] were evaluated and compared to those of human Aβ(1-42). Both human Aβ(1-42) and Aβ(1-42)Rat were found to have a significant effect on neuronal DNA fragmentation, loss of neuritic networks, and cell viability. Aβ(1-42) Rat was found to cause a significant increase in both protein oxidation and lipid peroxidation, similar to Aβ(1-42), both of which were inhibited by the lipid-soluble, chain breaking antioxidant vitamin E, suggesting that reactive oxygen species play a role in the Aβ-mediated toxicity. Taken together, these results suggest that Cu(II) reduction may not play a critical role in Aβ(1-42)Rat-induced oxidative stress, and that the oxidative stress exhibited by this peptide may be a consequence of the presence of methionine 35, similar to the findings associated with the native human Aβ(1-42) peptide.