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1.
J Intern Med ; 259(3): 323-31, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16476110

RESUMO

STUDY OBJECTIVES: Asthma and gastro-oesophageal reflux (GER) are both characterized by airway inflammation. DESIGN: The purposes of this work were (i) to study airway inflammation in patients troubled by gastro-oesophageal reflux (GER) and GER associated with asthma, (ii) to ascertain whether GER can aggravate asthma by exacerbating the pre-existing airway inflammation and oxidative stress and (iii) to establish the validity of analysing breath condensate and induced sputum when studying the airways of subjects affected by GER. PATIENT S AND METHODS: We enrolled 14 patients affected by mild asthma associated with GER (40 +/-12 years), nine with mild but persistent asthma (39 +/- 13 years), eight with GER (35 +/- 11 years) and 17 healthy subjects (37 +/- 9 years). Sputum cell counts and concentrations of interleukin-4 (IL-4), IL-6 and 8-isoprostane were measured in breath condensate and supernatant. MEASUREMENTS AND RESULTS: GER-related asthma is characterized by an eosinophilic inflammation, as determined by elevated concentrations of IL-4 in breath condensate and sputum supernatant, and by sputum cell analysis. GER alone presents a neutrophilic pattern of inflammation when determined by elevated concentrations of IL-6 in sputum cell analysis. A concomitant increase has been found in 8-isoprostane in GER associated (or not associated) with asthma. CONCLUSIONS: We conclude that GER is characterized by a neutrophilic airway inflammation and by increased oxidative stress. GER does not however aggravate pre-existing airway inflammation in asthma patients. Determinations of inflammatory and oxidant markers in the breath condensate of subjects with GER reflect these measured in the induced sputum.


Assuntos
Asma/etiologia , Refluxo Gastroesofágico/complicações , Adulto , Asma/metabolismo , Asma/fisiopatologia , Biomarcadores/análise , Testes Respiratórios , Estudos Transversais , Dinoprosta/análogos & derivados , Dinoprosta/análise , Feminino , Volume Expiratório Forçado , Refluxo Gastroesofágico/metabolismo , Refluxo Gastroesofágico/fisiopatologia , Humanos , Concentração de Íons de Hidrogênio , Mediadores da Inflamação/análise , Interleucina-4/análise , Interleucina-6/análise , Masculino , Pessoa de Meia-Idade , Estresse Oxidativo , Escarro/química , Escarro/citologia , Capacidade Vital
3.
Neurology ; 61(2): 199-205, 2003 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-12874399

RESUMO

BACKGROUND: Epidemiologic and experimental data suggest that cholesterol may play a role in the pathogenesis of AD. Modulation of cholesterolemia in transgenic animal models of AD strongly alters amyloid pathology. OBJECTIVE: To determine whether a relationship exists between amyloid deposition and total cholesterolemia (TC) in the human brain. METHODS: The authors reviewed autopsy cases of patients older than 40 years and correlated cholesterolemia and presence or absence of amyloid deposition (amyloid positive vs amyloid negative subjects) and cholesterolemia and amyloid load. Amyloid load in human brains was measured by immunohistochemistry and image analysis. To remove the effect of apoE isoforms on cholesterol levels, cases were genotyped and duplicate analyses were performed on apoE3/3 subjects. RESULTS: Cholesterolemia correlates with presence of amyloid deposition in the youngest subjects (40 to 55 years) with early amyloid deposition (diffuse type of senile plaques) (p = 0.000 for all apoE isoforms; p = 0.009 for apoE3/3 subjects). In this group, increases in cholesterolemia from 181 to 200 almost tripled the odds for developing amyloid, independent of apoE isoform. A logistic regression model showed consistent results (McFadden rho2 = 0.445). The difference in mean TC between subjects with and without amyloid disappeared as the age of the sample increased (>55 years: p = 0.491), possibly reflecting the effect of cardiovascular deaths among other possibilities. TC and amyloid load were not linearly correlated, indicating that there are additional factors involved in amyloid accumulation. CONCLUSIONS: Serum hypercholesterolemia may be an early risk factor for the development of AD amyloid pathology.


Assuntos
Doença de Alzheimer/epidemiologia , Peptídeos beta-Amiloides/análise , Angiopatia Amiloide Cerebral/epidemiologia , Hipercolesterolemia/epidemiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/etiologia , Doença de Alzheimer/patologia , Apolipoproteínas E/sangue , Apolipoproteínas E/genética , Angiopatia Amiloide Cerebral/etiologia , Angiopatia Amiloide Cerebral/patologia , Feminino , Hipocampo/química , Hipocampo/patologia , Humanos , Hipercolesterolemia/complicações , Hipercolesterolemia/tratamento farmacológico , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Placa Amiloide , Isoformas de Proteínas/sangue , Isoformas de Proteínas/genética , Estudos Retrospectivos , Fatores de Risco , Lobo Temporal/química , Lobo Temporal/patologia
4.
J Neurochem ; 80(1): 191-6, 2002 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11796757

RESUMO

Clinical studies have shown that estrogen deprivation through menopause is a risk factor in both the initiation and progression of Alzheimer's disease (AD) and that estrogen replacement therapy may be protective. One of the major pathological features in the human AD brain is the senile plaque, a proteinaceous structure composed mainly of heterogeneous peptides collectively known as A-beta (A(beta)). In vitro studies have linked estrogen with A(beta) modulation, suggesting that one-way that estrogen depletion at menopause may exacerbate the features of AD is through A(beta) accumulation. To test this, two studies were performed on transgenic models of amyloidosis. Firstly, transgenic mice without detectable amyloid aggregates were subjected to ovariectomy and estradiol supplementation, and A(beta) levels were assessed. Secondly, the effects of estrogen modulation were assessed in mice at an age when plaques would be forming initially. Overall, A(beta) levels were higher in estrogen-deprived mice than intact mice, and this effect could be reversed through the administration of estradiol. These data suggest that, in vivo, estrogen depletion leads to the accumulation of A(beta) in the CNS, which can be reversed through replacement of estradiol. These results provide evidence that post-menopausal estrogen depletion may be linked to an increased risk of AD through A(beta) modulation.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Estradiol/farmacologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Transgênicos/genética , Ovariectomia , Fragmentos de Peptídeos/metabolismo , Presenilina-1
5.
Neurobiol Dis ; 8(5): 890-9, 2001 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11592856

RESUMO

Clinical, epidemiological, and laboratory studies suggest that cholesterol may play a role in the pathogenesis of Alzheimer's disease (AD). Transgenic mice exhibiting an Alzheimer's beta-amyloid phenotype were treated with the cholesterol-lowering drug BM15.766 and tested for modulation of beta-amyloid levels. BM15.766 treatment reduced plasma cholesterol, brain Abeta peptides, and beta-amyloid load by greater than twofold. A strong, positive correlation between the amount of plasma cholesterol and Abeta was observed. Furthermore, drug treatment reduced the amyloidogenic processing of the amyloid precursor protein, suggesting alterations in processing in response to cholesterol modulation. This study demonstrates that hypocholesterolemia is associated with reduced Abeta accumulation suggesting that lowering cholesterol by pharmacological means may be an effective approach for reducing the risk of developing AD.


Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/análise , Anticolesterolemiantes/uso terapêutico , Química Encefálica/efeitos dos fármacos , Proteínas do Tecido Nervoso/análise , Oxirredutases atuantes sobre Doadores de Grupo CH-CH , Piperazinas/uso terapêutico , Doença de Alzheimer/sangue , Doença de Alzheimer/tratamento farmacológico , Secretases da Proteína Precursora do Amiloide , Precursor de Proteína beta-Amiloide/análise , Animais , Anticolesterolemiantes/farmacologia , Ácido Aspártico Endopeptidases , Colesterol/análise , Colesterol/sangue , Colesterol/fisiologia , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos , Endopeptidases/metabolismo , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/uso terapêutico , Feminino , Humanos , Masculino , Proteínas de Membrana/análise , Camundongos , Camundongos Transgênicos , Oxirredutases/antagonistas & inibidores , Piperazinas/farmacologia , Presenilina-1 , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Processamento de Proteína Pós-Traducional/fisiologia , Componente Amiloide P Sérico/análise
6.
Neurobiol Dis ; 7(4): 321-31, 2000 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10964604

RESUMO

Recent data suggest that cholesterol metabolism is linked to susceptibility to Alzheimer's disease (AD). However, no direct evidence has been reported linking cholesterol metabolism and the pathogenesis of AD. To test the hypothesis that amyloid beta-peptide (Abeta) deposition can be modulated by diet-induced hypercholesterolemia, we used a transgenic-mouse model for AD amyloidosis and examined the effects of a high-fat/high-cholesterol diet on central nervous system (CNS) Abeta accumulation. Our data showed that diet-induced hypercholesterolemia resulted in significantly increased levels of formic acid-extractable Abeta peptides in the CNS. Furthermore, the levels of total Abeta were strongly correlated with the levels of both plasma and CNS total cholesterol. Biochemical analysis revealed that, compared with control, the hypercholesterolemic mice had significantly decreased levels of sAPPalpha and increased levels of C-terminal fragments (beta-CTFs), suggesting alterations in amyloid precursor protein processing in response to hypercholesterolemia. Neuropathological analysis indicated that the hypercholesterolemic diet significantly increased beta-amyloid load by increasing both deposit number and size. These data demonstrate that high dietary cholesterol increases Abeta accumulation and accelerates the AD-related pathology observed in this animal model. Thus, we propose that diet can be used to modulate the risk of developing AD.


Assuntos
Doença de Alzheimer/etiologia , Peptídeos beta-Amiloides/metabolismo , Colesterol na Dieta/efeitos adversos , Modelos Animais de Doenças , Hipercolesterolemia/complicações , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Animais , Encéfalo/metabolismo , Colesterol na Dieta/administração & dosagem , Colesterol na Dieta/sangue , Hipercolesterolemia/sangue , Hipercolesterolemia/etiologia , Camundongos , Camundongos Transgênicos
7.
Neurobiol Dis ; 7(2): 87-98, 2000 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10783293

RESUMO

To examine the normal cellular function of tau and its role in pathogenesis, we have created transgenic mice that overexpress a tau transgene derived from a human PAC that contains the coding sequence, intronic regions, and regulatory regions of the human gene. All six isoforms of human tau are represented in the transgenic mouse brain at the mRNA and protein level and the human tau is distributed in neurites and at synapses, but is absent from cell bodies. A comparison between the genomic tau mice and mice that overexpress a tau cDNA transgene shows that overall, the distribution of tau is similar in the two lines, but human tau is located in the somatodendritic compartment of many neurons in the cDNA mice. Tau-immunoreactive axonal swellings were found in the spinal cords of the cDNA mice, which correlated with a hind-limb abnormality, whereas neuropathology was essentially normal in the genomic mice up to 8 months of age.


Assuntos
Encéfalo/patologia , Regulação da Expressão Gênica/fisiologia , Proteínas tau/análise , Doença de Alzheimer/patologia , Doença de Alzheimer/fisiopatologia , Animais , Encéfalo/fisiopatologia , Humanos , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , Microscopia Eletrônica , Neurônios/patologia , Neurônios/ultraestrutura , Regiões Promotoras Genéticas/fisiologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transcrição Gênica/fisiologia
8.
J Neurochem ; 73(6): 2383-8, 1999 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-10582597

RESUMO

Autosomal dominant mutations in the presenilin 1 (PS1) gene are associated with familial, early-onset Alzheimer's disease. Although the pathogenic mechanism of these mutations is unclear, their common feature is that they lead to an increased concentration of amyloid beta-peptide (Abeta) 42 in the plasma of early-onset patients, in the conditioned media of transfected cells, and in the brains of transgenic mice that overexpress mutant PS1. To address the mechanism(s) by which the pathogenic PS1 mutations increase Abeta42, we constructed human cell lines expressing a doxycyclin (dox)-inducible antisense PS1 RNA and measured its effects on the levels of PS1, amyloid precursor protein (APP), and Abeta. In time course experiments, we observed a statistically significant (p = 0.0038) more than twofold elevation in secreted Abeta42 as early as 12 days after addition of dox. This correlated with an 80% decrease in the 46-kDa PS1 holoprotein and a 30% decrease in the 26-kDa N-terminal fragment (NTF). Furthermore, there was a significant fivefold (p = 0.002) increase in Abeta42 after 14-day dox treatment; this correlated with a >90% decrease in PS1 holoprotein and 60% decrease in NTF. At no time point did we observe significant changes in Abeta40, APP holoprotein, presenilin 2, or tubulin. Ten days after the removal of dox, we observed a return to constitutive levels for Abeta42, PS1 holoprotein, and NTF. These results suggest that in human cell lines, the reduction of normal PS1 activity results in the increased production of Abeta42. Furthermore, our results are consistent with a loss of function or dominant negative mechanism for the pathogenic PS1 mutations.


Assuntos
Doença de Alzheimer/genética , Peptídeos beta-Amiloides/biossíntese , Regulação da Expressão Gênica/efeitos dos fármacos , Proteínas de Membrana/metabolismo , Fragmentos de Peptídeos/biossíntese , RNA Antissenso/farmacologia , Peptídeos beta-Amiloides/genética , Linhagem Celular , Doxiciclina/farmacologia , Humanos , Rim , Proteínas de Membrana/genética , Fragmentos de Peptídeos/genética , Presenilina-1 , Transfecção , Tubulina (Proteína)/biossíntese , Tubulina (Proteína)/genética
9.
J Biol Chem ; 274(38): 26810-4, 1999 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-10480887

RESUMO

The Alzheimer's amyloid protein (Abeta) is released from the larger amyloid beta-protein precursor (APP) by unidentified enzymes referred to as beta- and gamma-secretase. beta-Secretase cleaves APP on the amino side of Abeta producing a large secreted derivative (sAPPbeta) and an Abeta-bearing C-terminal derivative that is subsequently cleaved by gamma-secretase to release Abeta. Alternative cleavage of the APP by alpha-secretase at Abeta16/17 releases the secreted derivative sAPPalpha. In yeast, alpha-secretase activity has been attributed to glycosylphosphatidylinositol (GPI)-anchored aspartyl proteases. To examine the role of GPI-anchored proteins, we specifically removed these proteins from the surface of mammalian cells using phosphatidylinositol-specific phospholipase C (PI-PLC). PI-PLC treatment of fetal guinea pig brain cultures substantially reduced the amount of Abeta40 and Abeta42 in the medium but had no effect on sAPPalpha. A mutant CHO cell line (gpi85), which lacks GPI-anchored proteins, secreted lower levels of Abeta40, Abeta42, and sAPPbeta than its parental line (GPI+). When this parental line was treated with PI-PLC, Abeta40, Abeta42, and sAPPbeta decreased to levels similar to those observed in the mutant line, and the mutant line was resistant to these effects of PI-PLC. These findings provide strong evidence that one or more GPI-anchored proteins play an important role in beta-secretase activity and Abeta secretion in mammalian cells. The cell-surface GPI-anchored protein(s) involved in Abeta biogenesis may be excellent therapeutic target(s) in Alzheimer's disease.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/biossíntese , Glicosilfosfatidilinositóis/metabolismo , Doença de Alzheimer/enzimologia , Secretases da Proteína Precursora do Amiloide , Animais , Ácido Aspártico Endopeptidases , Encéfalo/enzimologia , Células CHO , Células Cultivadas , Cricetinae , Endopeptidases/metabolismo , Ativação Enzimática , Cobaias , Humanos , Hidrólise , Fosfatidilinositol Diacilglicerol-Liase , Fosfoinositídeo Fosfolipase C , Proteína Quinase C/metabolismo , Fosfolipases Tipo C/metabolismo
10.
Ann Neurol ; 43(2): 256-8, 1998 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9485068

RESUMO

Mutations in the presenilin 1 (PS1) gene on chromosome 14 are a major cause of autosomal dominant, early-onset Alzheimer's disease. Here, we show that transfecting cells with several mutant, but not wild-type, PS1 cDNAs alters the processing of the amyloid precursor protein (APP) such that more Abeta42(43) is produced, confirming and extending several recent reports. The most effective mutation in this regard was the exon 9 splice-out mutation (delta9). The correlation between the size of the effect on APP processing and the age of onset of disease assessed in families with the mutations was not informative, and the possible reasons for this are discussed.


Assuntos
Cromossomos Humanos Par 14 , Proteínas de Membrana/genética , Mutação Puntual , Idade de Início , Doença de Alzheimer/genética , Análise de Variância , Western Blotting , Linhagem Celular , Células Clonais , DNA Complementar/análise , Regulação da Expressão Gênica , Humanos , Rim/embriologia , Presenilina-1 , Transfecção
11.
Hum Mol Genet ; 6(12): 2087-9, 1997 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-9328472

RESUMO

We report a novel mutation in the amyloid precursor protein gene (APP I716V) which probably leads to familial early onset Alzheimer's disease with an onset age in the mid 50s. Cells transfected with cDNAs bearing this mutation produce more A beta 1-42(43) than those transfected with wild-type APP and this effect is additive with that of the previously reported APP V717I mutation thus providing a novel approach for further increasing A beta 1-42(43) in model systems.


Assuntos
Doença de Alzheimer/genética , Peptídeos beta-Amiloides/genética , Precursor de Proteína beta-Amiloide/genética , Fragmentos de Peptídeos/genética , Mutação Puntual , Idade de Início , Doença de Alzheimer/etiologia , Feminino , Humanos , Pessoa de Meia-Idade
12.
J Biol Chem ; 271(49): 31407-11, 1996 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-8940150

RESUMO

Alzheimer's disease is characterized by the extracellular deposition of beta-amyloid peptide (Abeta) in cerebral plaques and evidence is accumulating that amyloid is neurotoxic. Abeta is derived from the beta-amyloid precursor protein (APP). Proteolytic processing of APP by the enzyme, beta-secretase, produces the N terminus of Abeta, and releases a secreted ectodomain of APP (beta-s-APP). To develop animal models for measuring beta-secretase activity in specific brain cells in vivo, we have targeted the expression of the full-length human APP to either neurons or astrocytes in transgenic mice using the neuron- specific enolase (NSE) promoter or a modified glial fibrillary acidic protein (GFAP) gene, respectively. The APP cDNAs expressed were mutated (KM to NL at 670/671) to encode amino acid substitutions that enhance amyloidogenic processing in vitro. Western analyses revealed abundant production of beta-s-APP in the brains of NSE-APP mice and enzyme-linked immunosorbent assay analyses showed production of Abeta in fetal primary mixed brain cultures and brain homogenates from these transgenic animals. Because the NSE promoter drives expression primarily in neurons, this provides in vivo evidence that the beta-secretase cleavage necessary for generation of beta-s-APP and Abeta is efficiently performed in neurons. In contrast, only little beta-s-APP was detected in brain homogenates of GFAP-APP mice, indicating that astrocytes show very little beta-secretase activity in vivo. This provides strong in vivo evidence that the major source of Abeta in brain is from neurons and not from astrocytes.


Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Astrócitos/metabolismo , Endopeptidases/metabolismo , Neurônios/metabolismo , Secretases da Proteína Precursora do Amiloide , Animais , Ácido Aspártico Endopeptidases , Western Blotting , Encéfalo/metabolismo , Éxons , Proteína Glial Fibrilar Ácida/genética , Humanos , Camundongos , Camundongos Transgênicos , Fosfopiruvato Hidratase/genética , Ratos
13.
Nature ; 383(6602): 710-3, 1996 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-8878479

RESUMO

Mutations in the genes encoding amyloid-beta precursor protein (APP), presenilin 1 (PS1) and presenilin 2 (PS2) are known to cause early-onset, autosomal dominant Alzheimer's disease. Studies of plasma and fibroblasts from subjects with these mutations have established that they all alter amyloid beta-protein (beta APP) processing, which normally leads to the secretion of amyloid-beta protein (relative molecular mass 4,000; M(r) 4K; approximately 90% A beta1-40, approximately 10% A beta1-42(43)), so that the extracellular concentration of A beta42(43) is increased. This increase in A beta42(43) is believed to be the critical change that initiates Alzheimer's disease pathogenesis because A beta42(43) is deposited early and selectively in the senile plaques that are observed in the brains of patients with all forms of the disease. To establish that the presenilin mutations increase the amount of A beta42(43) in the brain and to test whether presenilin mutations act as true (gain of function) dominants, we have now constructed mice expressing wild-type and mutant presenilin genes. Analysis of these mice showed that overexpression of mutant, but not wild-type, PS1 selectively increases brain A beta42(43). These results indicate that the presenilin mutations probably cause Alzheimer's disease through a gain of deleterious function that increases the amount of A beta42(43) in the brain.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Proteínas de Membrana/genética , Fragmentos de Peptídeos/metabolismo , Animais , Humanos , Proteínas de Membrana/biossíntese , Camundongos , Camundongos Transgênicos , Mutagênese , Presenilina-1
14.
J Neurochem ; 67(2): 872-5, 1996 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-8764618

RESUMO

alpha-Secretase cleaves the full-length Alzheimer's amyloid precursor protein (APP) within the amyloid beta peptide sequence, thus precluding amyloid formation. The resultant soluble truncated APP is constitutively secreted. This nonamyloidogenic processing of APP is increased on stimulation of the phospholipase C/protein kinase C pathway by phorbol esters. Here we used C6 cells transfected with APP751 to examine whether the alpha-secretase cleavage is regulated by the adenylate cyclase signal transduction pathway. Forskolin, an activator of adenylate cyclase, inhibited both the constitutive and phorbol ester-stimulated secretion of nexin II (NXII), the secreted product of the alpha-secretase cleavage of APP751. At 1 microM, forskolin inhibited secretion of NXII by approximately 50% without affecting either the intracellular levels of total APP or the secretion of secretory alkaline phosphatase. In contrast, 1,9-dideoxyforskolin, an inactive analogue of forskolin, did not affect secretion of NXII. These results indicated that forskolin specifically inhibited the alpha-secretase cleavage of APP751. Forskolin treatment increased the intracellular concentration of cyclic AMP (cAMP), suggesting that the forskolin effects on APP cleavage may be mediated by cAMP. In support of this suggestion, both dibutyryl cAMP, a cAMP analogue, and isoproterenol, an activator of adenylate cyclase, also inhibited secretion of NXII. These data indicate that forskolin inhibition of the nonamyloidogenic cleavage of APP is mediated by the second messenger cAMP, which together with the protein kinase C signal transduction pathway modulates the secretory cleavage of APP.


Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Proteínas de Transporte/metabolismo , AMP Cíclico/farmacologia , Animais , Bucladesina/farmacologia , Células Cultivadas , Colforsina/farmacologia , Isoproterenol/farmacologia , Ésteres de Forbol/farmacologia , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Ratos , Transdução de Sinais/efeitos dos fármacos
15.
Neurosci Lett ; 192(2): 105-8, 1995 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-7675314

RESUMO

The heat shock or stress response may play a role in the pathogenesis of Alzheimer's disease. We conducted experiments to visualize microscopically the distribution of wild type amyloid precursor protein (APP) and the behavior of an APP deletion mutant under stress. This was achieved by heat-shock treatment of cells expressing fusion recombinant APP proteins tagged with secreted placental alkaline phosphatase (SEAP). The fusion proteins were cleaved and secreted in a manner similar to wild type APP in unstressed control cells. SEAP activity was detected by cytochemical methods within the cytoplasm in less than 10% of transfected unstressed cells. Heat shocked cells showed a striking difference from the control cells in that over 90% of the stressed cells displayed strong intracytoplasmic SEAP activity occurring with Golgi-like pattern and/or membranous distribution. The effects of heat shock were not due to a peculiar behavior of the clones and depended on the APP portion of the constructs. This study shows miscompartmentalization of APP under stress. Such cellular changes may bear important implications in the processing of APP.


Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Temperatura Alta , Proteínas Recombinantes de Fusão/metabolismo , Choque/metabolismo , Choque/patologia , Fosfatase Alcalina/genética , Fosfatase Alcalina/metabolismo , Precursor de Proteína beta-Amiloide/genética , Citoplasma/metabolismo , Histocitoquímica , Placenta/metabolismo , Proteínas Recombinantes de Fusão/genética , Distribuição Tecidual , Células Tumorais Cultivadas
16.
J Neurosci Res ; 40(5): 694-706, 1995 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-7602619

RESUMO

Three different treatments (methylamine, colchicine, and 18 degrees C temperature block), known to disrupt normal endocytic internalization, significantly reduced the secretory cleavage of cell surface-derived Alzheimer amyloid precursor (APP) in non-transfected C6 cell cultures. Conversely, treatments with methylamine or colchicine had no significant effect on the secretion of total APP. Treatment of these cells with the lysosomotropic amine chloroquine resulted in a significant increase in the levels of both cell surface full-length APP and cell surface-derived secreted nexin II (NXII). Immunofluorescence analysis of C6 glioma cells transfected with APP751 indicated that under normal conditions, cell surface APP was internalized, and within 30 minutes was localized in discrete intracellular vesicles. These vesicles contained the endocytic tracer Texas red-conjugated ovalbumin and probably represented late endosomes or lysosomes. However, treatment of the transfected C6 cultures with methylamine or colchicine prevented localization of cell surface APP in intracellular vesicles, suggesting that these treatments altered the normal intracellular trafficking of cell surface-derived APP. Both the biochemical and immunofluorescence data are compatible with the suggestion that inhibition of normal endocytic internalization reduces the secretory cleavage of cell surface APP. Furthermore, our results suggest that following internalization, cell surface APP is cleaved by secretase(s) and secreted or routed to the lysosomes where it is degraded.


Assuntos
Doença de Alzheimer/enzimologia , Precursor de Proteína beta-Amiloide/metabolismo , Endocitose/fisiologia , Endopeptidases/metabolismo , Secretases da Proteína Precursora do Amiloide , Animais , Ácido Aspártico Endopeptidases , Linhagem Celular , Cloroquina/farmacologia , Temperatura Baixa , Endocitose/efeitos dos fármacos , Imunofluorescência , Glioma/metabolismo , Humanos , Immunoblotting , Imuno-Histoquímica , Metilaminas/farmacologia , Testes de Precipitina , Ratos
17.
J Neurosci Res ; 38(1): 81-90, 1994 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-8057394

RESUMO

Phorbol esters (PDBu) stimulate alpha-secretase cleavage and secretion of the Alzheimer amyloid precursor protein (APP). To determine whether any cytoplasmic residues or sequence motifs mediate the PDBu effect on APP processing, this region of APP was altered by point mutations or deletions. To differentiate the mutated APP from the endogenous APP, the APP751 ectodomain between amino acids 1 and 647 was replaced by a human secreted alkaline phosphatase derivative (SEAP). The resultant fusion protein (SEAP-APP751) was cleaved by alpha-secretase at the same site as full-length APP, and its secretion was stimulated by PDBu at a level similar to APP751. However, PDBu-stimulated secretion of the SEAP-APP751 fusion protein reached its maximum level after 30 min of treatment, while secretion of APP751 reached its maximum after 60 min, suggesting that the APP ectodomain affects the kinetics of APP secretion. Mutation of the cytoplasmic serines to alanines had no effect on the PDBu-stimulated secretion of the SEAP-APP, indicating that protein kinase C (PKC) phosphorylation of the cytoplasmic domain of APP is not important for stimulation of APP secretion. Similarly, deletion of the cytoplasmic domain between amino acids 719 and 751 had no effect on the PDBu-stimulated secretion. However, deletion of amino acids 707-751 resulted in a significant increase in the secretory cleavage of the SEAP-APP707 delta C construct, suggesting that the sequence 707-719 is important for the regulated secretion of APP. Cholera toxin, but not pertussis toxin, reduced the PDBu-induced secretion of APP by more than two-fold, suggesting that the PDBu response may be modulated by a cholera toxin sensitive heterotrimeric G-protein.


Assuntos
Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Toxina da Cólera/farmacologia , Acetato de Tetradecanoilforbol/farmacologia , Precursor de Proteína beta-Amiloide/genética , Animais , Neoplasias Encefálicas/metabolismo , Citoplasma/metabolismo , Proteínas de Ligação ao GTP/biossíntese , Glioma/metabolismo , Mutagênese , Proteínas do Tecido Nervoso/biossíntese , Proteínas do Tecido Nervoso/metabolismo , Plasmídeos , Testes de Precipitina , Ratos , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Células Tumorais Cultivadas
18.
Ann N Y Acad Sci ; 695: 132-8, 1993 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-8239271

RESUMO

Amyloid beta protein (beta/A4 or A beta), the main proteinaceous component of the amyloid depositions of the Alzheimer's brain, derives from the proteolytic processing of the amyloid precursor protein (APP). Cleavage of the amyloid precursor by at least two distinct secretase activities produces soluble secreted APP. The major secretase cleavage (site I) takes place between A beta 16 and 17, while the minor cleavage (site II) takes place after A beta Lys 28 and may produce potentially amyloidogenic secreted APP. Full-length cellular APP is cleaved by secretase intracellularly in the Trans-Golgi Network (TGN) or in post-Golgi vesicles. The resultant soluble APP is transported to the plasma membrane and exocytosed. The biological activity of the APP is still not completely understood, although it seems to act as a cell adhesion molecule. Recent studies have shown that in glioma cells, most of the soluble secreted APP occurs as a chondroitin sulfate proteoglycan (CSPG). In addition, full length APP CSPG has been detected in neuroblastoma and fibroblast cells as well as on the surface of glioma cells, and in human brain. These results suggest that the proteoglycan nature of the APP proteins may be important for their biological function.


Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Proteoglicanas de Sulfatos de Condroitina/metabolismo , Neurônios/metabolismo , Processamento de Proteína Pós-Traducional , Proteoglicanas/metabolismo , Sequência de Aminoácidos , Secretases da Proteína Precursora do Amiloide , Animais , Ácido Aspártico Endopeptidases , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular , Proteoglicanas de Sulfatos de Condroitina/química , Endopeptidases/metabolismo , Complexo de Golgi/metabolismo , Humanos , Rim , Lisossomos/metabolismo , Modelos Biológicos , Fatores de Crescimento Neural/farmacologia , Células PC12 , Transfecção
19.
Ann N Y Acad Sci ; 695: 194-7, 1993 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-8239282

RESUMO

The Alzheimer's disease (AD) brain contains many abnormal protein modifications. These include the abnormal processing of amyloid precursor protein (APP) to form the amyloidogenic beta/A4 peptide and the abnormal phosphorylation of tau to form A68, the major constituent of the neurofibrillary tangle. In addition, many of the biochemical alterations found in the AD brain are also found in heat-shocked or stressed cells. We used heat-shocked neuronal PC12 cells to investigate the effects of stress on APP and tau. We found that by simply exposing neuronal PC12 cells to an elevated temperature (45 degrees C) for 30 minutes, they exhibited several features characteristic of the heat shock response. These included a 45% reduction in total protein synthesis, the induction of heat shock protein (hsp) 72, and increased phosphorylation of the protein synthesis initiation factor eIF-2 alpha. The heat-shocked cells also exhibited alterations in the metabolism and phosphorylation of APP. Under heat shock conditions, we found two additional APP-like polypeptides not present in controls and a significant decrease in the phosphorylation state of APP. We also found that an A68-like protein is formed in neuronal PC12 cells when subjected to elevated temperature. This A68-like protein was formed with heat shock even in the absence of protein synthesis, suggesting that its production occurred post-translationally. The tau/A68 polypeptides were identified as phosphoproteins, and the phosphorylation of tau to form A68 was reversed with recovery of the cells from heat shock. Immunoprecipitation of lysates from heat shocked cells with antibodies to hsp72/73 resulted in co-precipitation of tau, but not A68 with hsp72 indicating a stable complex formation between these two proteins. These results suggest that heat shock proteins may play either a protective or promoting role in the formation of A68 and/or the amyloidogenic C-terminal fragment of APP.


Assuntos
Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Neurônios/metabolismo , Proteínas tau/metabolismo , Peptídeos beta-Amiloides/biossíntese , Precursor de Proteína beta-Amiloide/biossíntese , Animais , Proteínas de Choque Térmico/biossíntese , Temperatura Alta , Humanos , Metionina/metabolismo , Fatores de Crescimento Neural/farmacologia , Células PC12 , Proteínas tau/biossíntese
20.
Brain Res Mol Brain Res ; 19(1-2): 140-8, 1993 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-8361337

RESUMO

The pathology of the Alzheimer's disease (AD) brain, including amyloid plaques, neurofibrillary tangles and neuronal degeneration, indicates that neurons affected by AD exist under conditions of stress. In fact, the brains of AD patients undergo many changes classically associated with the heat shock response, which is one form of a stress response. These changes include reduced protein synthesis, disrupted cytoskeleton, increased number of proteins associated with ubiquitin, and the induction of heat shock proteins. To investigate the response of neurons to stress, we examined neuronal PC12 cells incubated at either 37 degrees C (control cells) or 45 degrees C (heat-shocked cells). After a 30 min exposure at 45 degrees C, the heat-shocked cells exhibited several features characteristic of the classical heat shock response including a 45% reduction in total protein synthesis, the induction of heat shock protein 72, and an increased phosphorylation of the protein synthesis initiation factor eIF-2 alpha. We used this cellular model system to study the neuronal response to stress specifically focusing on protein synthesis elongation factor 2 (EF-2) and the Alzheimer's amyloid precursor protein (APP), the precursor form of beta-amyloid peptide. Hyperphosphorylation of EF-2 has been observed in the neocortex and hippocampus of AD brain. However, in our system, we find no hyperphosphorylation of EF-2 in response to heat shock. Heat-shocked neuronal PC12 cells exhibited two additional APP-like polypeptides not present in controls. We also found a significant decrease in the phosphorylation state of APP in response to heat shock.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Precursor de Proteína beta-Amiloide/biossíntese , Precursor de Proteína beta-Amiloide/metabolismo , Regulação Neoplásica da Expressão Gênica , Proteínas de Choque Térmico/biossíntese , Neurônios/metabolismo , Precursor de Proteína beta-Amiloide/isolamento & purificação , Animais , Autorradiografia , Eletroforese em Gel Bidimensional , Eletroforese em Gel de Poliacrilamida , Expressão Gênica , Proteínas de Choque Térmico/isolamento & purificação , Temperatura Alta , Metionina/metabolismo , Células PC12 , Fosfatos/metabolismo , Radioisótopos de Fósforo , Fosforilação , Radioisótopos de Enxofre
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