Alzheimer disease (AD) is an age-dependent neurodegenerative disease characterized by the formation of β–amyloid (Aβ)-containing senile plaque. The disease could be induced by the administration of Aβ peptide, which was also known to upregulate inducible nitric oxide synthase (iNOS) and stimulate neuronal apoptosis. The present study is aimed to elucidate the cellular effect of resveratrol, a natural phytoestrogen with neuroprotective activities, on Aβ-induced hippocampal neuron loss and memory impairment. On adult Sprague-Dawley rats, we found the injection of Aβ could result in a significant impairment in spatial memory, a marked increase in the cellular level of iNOS and lipid peroxidation, and an apparent decrease in the expression of heme oxygenase-1 (HO-1). By combining the treatment with Aβ, resveratrol was able to confer a significant improvement in spatial memory, and protect animals from Aβ-induced neurotoxicity. These neurological protection effects of resveratrol were associated with a reduction in the cellular levels of iNOS and lipid peroxidation and an increase in the production of HO-1. Moreover, the similar neurological and cellular response were also observed when Aβ treatment was combined with the administration of a NOS inhibitor, N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME). These findings strongly implicate that iNOS is involved in the Aβ-induced lipid peroxidation and HO-1 downregulation, and resveratrol protects animals from Aβ-induced neurotoxicity by suppressing iNOS production.

The first representative of a group of mammalian, low molecular weight phosphotyrosyl protein phosphatases was cloned, sequenced and expressed in Escherichia coli. Using a 61-mer oligonucleotide probe based on the amino acid sequence of the purified enzyme, several overlapping cDNA clones were isolated from a bovine heart cDNA library. A full-length clone was obtained consisting of a 27-bp 5' noncoding region, an open reading frame encoding the expected 157 amino acid protein, and an extensive 3' nontranslated sequence. The identification of the clone as full length was consistent with results obtained in mRNA blotting experiments using poly(A)+ mRNA from bovine heart. The coding sequence was placed downstream of a bacteriophage T7 promoter, and protein was expressed in E. coli. The expressed enzyme was soluble, and catalytically active and was readily isolated and purified. The recombinant protein had the expected Mr of 18,000 (estimated by SDS-PAGE), and it showed cross-reactivity with antisera that had been raised against both the bovine heart and the human placenta enzymes. The amino acid sequence of the N-terminal region of the expressed protein showed that methionine had been removed, resulting in a sequence identical to that of the enzyme isolated from the bovine tissue, with the exception that the N-terminal alanine of the protein from tissue is acetylated. A kinetically competent phosphoenzyme intermediate was trapped from a phosphatase-catalyzed reaction. Using 31P NMR, the covalent intermediate was identified as a cysteinyl phosphate. By analogy with the nomenclature used for serine esterases, these enzymes may be called cysteine phosphatases.

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Recent results show that brain glucocorticoids are involved in the dysregulation of fear memory extinction in post-traumatic stress disorder patients. The present study was aimed to elucidate the possible mechanism of glucocorticoids on the conditioned fear extinction. To achieve these goals, male SD rats, fear-potentiated startle paradigm, and Western blot were used. We found that (1) systemic administration of the synthetic glucocorticoid agonist dexamethasone (DEX) facilitated extinction of conditioned fear in a dose-dependent manner (0.05, 0.1, 0.5, or 1.0 mg/kg, i.p.); (2) systemic administration of the glutamate NMDA receptor antagonist (7)-HA966 (6.0 mg/kg, i.p.) and intra-amygdala infusion of the NMDA receptor antagonists MK801 (0.5 ng/side, bilaterally) or D,L-2-amino-5-phosphonovaleric acid (AP5, 2.0 ng/side, bilaterally) blocked the DEX facilitation effect; (3) the corticosteroid synthesis inhibitor metyrapone (25 mg/kg. s.c.) blocked extinction and this was prevented by co-administration of NMDA receptor agonist D-cycloserine (DCS, 5.0 mg/kg, i.p.); (4) co-administration of DEX and DCS in subthreshold doses provided a synergistic facilitation effect on extinction (0.2 and 5 mg/kg, respectively). Control experiments indicated that co-administration of DEX and DCS did not alter the expression of conditioned fear and the effect was not due to lasting damage to the amygdala. These results suggest that glutamate NMDA receptors within the amygdala participate in the modulatory effect of glucocorticoids on extinction.

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