Browsing by Author "Muñoz, FJ"

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    Neurotoxicity of acetylcholinesterase amyloid β-peptide aggregates is dependent on the type of Aβ peptide and the AChE concentration present in the complexes
    (1999) Muñoz, FJ; Inestrosa, NC
    Alzheimer's disease (AD) is a neurodegenerative disorder whose hallmark is the presence of senile plaques and neurofibrillary tangles, Senile plaques are mainly composed of amyloid beta-peptide (A beta) fibrils and several proteins including acetylcholinesterase (AChE), AChE has been previously shown to stimulate the aggregation of A beta(1-40) into amyloid fibrils, In the present work, the neurotoxicity of different amyloid aggregates formed in the absence or presence of AChE was evaluated in rat pheochromocytoma PC12 cells. Stable AChE-A beta complexes were found to be more toxic than those formed without the enzyme, for A beta(1-40) and A beta(1-42), but not for amyloid fibrils formed with A beta(Val18-->Ala), a synthetic variant of the A beta(1-40) peptide. Of all the AChE-A beta complexes tested the one containing the A beta(1-40) peptide was the most toxic, When increasing concentrations of AChE were used to aggregate the A beta(1-40) peptide, the neurotoxicity of the complexes increased as a function of the amount of enzyme bound to each complex. Our results shea that AChE-A beta(1-40) aggregates are more toxic than those of AChE-A beta(1-42) and that the neurotoxicity depends on the amount of AChE bound to the complexes, suggesting that AChE may play a key role in the neurodegeneration observed in Alzheimer brain. (C) 1999 Federation of European Biochemical Societies.
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    PC12 and neuro 2a cells have different susceptibilities to acetylcholinesterase-amyloid complexes, amyloid25-35 fragment, glutamate, and hydrogen peroxide
    (1999) Calderón, FH; Bonnefont, A; Muñoz, FJ; Fernández, V; Videla, LA; Inestrosa, NC
    This work addresses the differential effects of several oxidative insults on two neuronal cell lines, PC12 and Neuro 2a cells, extensively used as neuronal models in vitro, We measured cellular damage using the cytotoxic assays for MTT reduction and LDH release and found that acetylcholinesterase (AChE)-amyloid-beta-peptide (AP) complexes, A beta(25-35) fragment, glutamate and H2O2 were over 200-fold more toxic to PC12 than to Neuro 2a cells, 17 alpha and 17 beta estradiol were able to protect both cell types from damage caused by H2O2 or glutamate, By contrast, other insults not related to oxidative stress, such as those caused by the nonionic detergent Triton X-100 and serum deprivation, induced a similar level of damage in both PC12 and Neuro 2a cells, Considering that the AP peptide, H2O2 and glutamate are cellular insults that cause an increase In reactive oxygen species (ROS), the intracellular levels of the antioxidant compound, glutathione were verified, Neuro 2a cells were found to have 4- to 5-fold more glutathione than PC12 cells, Our results suggest that Neuro 2a cells are less susceptible to exposure to AChE-A beta complexes, A beta(25-35) fragment, glutamate and H2O2 than PC12 cells, due to higher intracellular levels of antioxidant defense factors. (C) 1999 Wiley-Liss, Inc.
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    Peripheral binding site is involved in the neurotrophic activity of acetylcholinesterase
    (1999) Muñoz, FJ; Aldunate, R; Inestrosa, NC
    ACETYLCHOLINESTERASE (AChE) catalyses the hydrolysis of the neurotransmitter acetylcholine and it has been implicated in several non-cholinergic actions, including neurite outgrowth and amyloid formation. We have studied the trophic function of brain AChE on neuronal cell metabolism and proliferation as well as the enzyme domain involved in such effects. Low AChE concentrations (0.1-2.5 nM) stimulated neurite outgrowth and induced cell proliferation as measured by MTT reduction and [H-3]thymidine incorporation. The action of AChE was not affected by edrophonium and tacrine both active site inhibitors, but it was abolished by propidium and gallamine, two peripheral anionic binding site (PAS) ligands. We conclude that the PAS domain of AChE is involved in the neurotrophic activity of the enzyme. (C) 1999 Lippincott Williams & Wilkins.
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    Stable complexes involving acetylcholinesterase and amyloid-β peptide change the biochemical properties of the enzyme and increase the neurotoxicity of Alzheimer's fibrils
    (1998) Alvarez, A; Alarcón, R; Opazo, C; Campos, EO; Muñoz, FJ; Calderón, FH; Dajas, F; Gentry, MK; Doctor, BP; De Mello, FG; Inestrosa, NC
    Brain acetylcholinesterase (AChE) forms stable complexes with amyloid-beta peptide (A beta) during its assembly into filaments, in agreement with its colocalization with the A beta deposits of Alzheimer's brain. The association of the enzyme with nascent A beta aggregates occurs as early as after 30 min of incubation. Analysis of the catalytic activity of the AChE incorporated into these complexes shows an anomalous behavior reminiscent of the AChE associated with senile plaques, which includes a resistance to low pH, high substrate concentrations, and lower sensitivity to AChE inhibitors. Furthermore, the toxicity of the AChE-amyloid complexes is higher than that of the A beta aggregates alone. Thus, in addition to its possible role as a heterogeneous nucleator during amyloid formation, AChE, by forming such stable complexes, may increase the neurotoxicity of A beta fibrils and thus may determine the selective neuronal loss observed in Alzheimer's brain.
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    Vitamin E but not 17β-estradiol protects against vascular toxicity induced by β-amyloid wild type and the Dutch amyloid variant
    (2002) Muñoz, FJ; Opazo, C; Gil-Gómez, G; Tapia, G; Fernández, V; Valverde, MA; Inestrosa, NC
    Amyloid beta-peptide (Abeta) fibril deposition on cerebral vessels produces cerebral amyloid angiopathy that appears in the majority of Alzheimer's disease patients. An early onset of a cerebral amyloid angiopathy variant called hereditary cerebral hemorrhage with amyloidosis of the Dutch type is caused by a point mutation in Abeta yielding Abeta(Glu22-->Gln). The present study addresses the effect of amyloid fibrils from both wild-type and mutated Abeta on vascular cells, as well as the putative protective role of antioxidants on amyloid angiopathy. For this purpose, we studied the cytotoxicity induced by Abeta(1-40 Glu22-->Gln) and Abeta(1-40 wild-type) fibrils on human venule endothelial cells and rat aorta smooth muscle cells. We observed that Abeta(Glu22-->Gln) fibrils are more toxic for vascular cells than the wild-type fibrils. We also evaluated the cytotoxicity of Abeta fibrils bound with acetylcholinesterase (AChE), a common component of amyloid deposits. Abeta(1-40 wild-type)-AChE fibrillar complexes, similar to neuronal cells, resulted in an increased toxicity on vascular cells. Previous reports showing that antioxidants are able to reduce the toxicity of Abeta fibrils on neuronal cells prompted us to test the effect of vitamin E, vitamin C, and 17beta-estradiol on vascular damage induced by Abeta(wild-type) and Abeta(Glu22-->Gln). Our data indicate that vitamin E attenuated significantly the Abeta-mediated cytotoxicity on vascular cells, although 17beta-estradiol and vitamin C failed to inhibit the cytotoxicity induced by Abeta fibrils.