RESUMO
INTRODUCTION: Large variability among Alzheimer's disease (AD) cases might impact genetic discoveries and complicate dissection of underlying biological pathways. METHODS: Genome Research at Fundacio ACE (GR@ACE) is a genome-wide study of dementia and its clinical endophenotypes, defined based on AD's clinical certainty and vascular burden. We assessed the impact of known AD loci across endophenotypes to generate loci categories. We incorporated gene coexpression data and conducted pathway analysis per category. Finally, to evaluate the effect of heterogeneity in genetic studies, GR@ACE series were meta-analyzed with additional genome-wide association study data sets. RESULTS: We classified known AD loci into three categories, which might reflect the disease clinical heterogeneity. Vascular processes were only detected as a causal mechanism in probable AD. The meta-analysis strategy revealed the ANKRD31-rs4704171 and NDUFAF6-rs10098778 and confirmed SCIMP-rs7225151 and CD33-rs3865444. DISCUSSION: The regulation of vasculature is a prominent causal component of probable AD. GR@ACE meta-analysis revealed novel AD genetic signals, strongly driven by the presence of clinical heterogeneity in the AD series.
Assuntos
Doença de Alzheimer/genética , Endofenótipos , Loci Gênicos , Estudo de Associação Genômica Ampla , Idoso , Doença de Alzheimer/classificação , Demência/genética , Feminino , Predisposição Genética para Doença , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único/genética , EspanhaRESUMO
The choroid plexuses (CP) release numerous biologically active enzymes and neurotrophic factors, and contain a subpopulation of neural progenitor cells providing the capacity to proliferate and differentiate into other types of cells. These characteristics make CP epithelial cells (CPECs) excellent candidates for cell therapy aiming at restoring brain tissue in neurodegenerative illnesses, including Alzheimer's disease (AD). In the present study, using in vitro approaches, we demonstrated that CP were able to diminish amyloid-ß (Aß) levels in cell cultures, reducing Aß-induced neurotoxicity. For in vivo studies, CPECs were transplanted into the brain of the APP/PS1 murine model of AD that exhibits advanced Aß accumulation and memory impairment. Brain examination after cell implantation revealed a significant reduction in brain Aß deposits, hyperphosphorylation of tau, and astrocytic reactivity. Remarkably, the transplantation of CPECs was accompanied by a total behavioral recovery in APP/PS1 mice, improving spatial and non-spatial memory. These findings reinforce the neuroprotective potential of CPECs and the use of cell therapies as useful tools in AD.
Assuntos
Doença de Alzheimer/cirurgia , Peptídeos beta-Amiloides/metabolismo , Transplante de Tecido Encefálico , Encéfalo/cirurgia , Plexo Corióideo/metabolismo , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/terapia , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Células Cultivadas , Plexo Corióideo/citologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ratos , Ratos WistarRESUMO
BACKGROUND: Mounting data suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of AD, possibly instigating amyloid-beta (Aß) accumulation decades before the onset of clinical symptoms. However, human in vivo evidence linking HSV-1 infection to AD pathology is lacking in normal aging, which may contribute to the elucidation of the role of HSV-1 infection as a potential AD risk factor. METHODS: To shed light into this question, serum anti-HSV IgG levels were correlated with 18F-Florbetaben-PET binding to Aß deposits and blood markers of neurodegeneration (pTau181 and neurofilament light chain) in cognitively normal older adults. Additionally, we investigated whether associations between anti-HSV IgG and AD markers were more evident in APOE4 carriers. RESULTS: We showed that increased anti-HSV IgG levels are associated with higher Aß load in fronto-temporal regions of cognitively normal older adults. Remarkably, these cortical regions exhibited abnormal patterns of resting state-functional connectivity (rs-FC) only in those individuals showing the highest levels of anti-HSV IgG. We further found that positive relationships between anti-HSV IgG levels and Aß load, particularly in the anterior cingulate cortex, are moderated by the APOE4 genotype, the strongest genetic risk factor for AD. Importantly, anti-HSV IgG levels were unrelated to either subclinical cognitive deficits or to blood markers of neurodegeneration. CONCLUSIONS: All together, these results suggest that HSV infection is selectively related to cortical Aß deposition in normal aging, supporting the inclusion of cognitively normal older adults in prospective trials of antimicrobial therapy aimed at decreasing the AD risk in the aging population.
Assuntos
Doença de Alzheimer , Herpes Simples , Herpesvirus Humano 1 , Humanos , Idoso , Apolipoproteína E4 , Estudos Prospectivos , Peptídeos beta-Amiloides/metabolismo , Herpesvirus Humano 1/metabolismo , Herpes Simples/diagnóstico por imagem , Herpes Simples/metabolismo , Envelhecimento/metabolismo , Imunoglobulina G , Doença de Alzheimer/diagnósticoRESUMO
Long runs of homozygosity (ROH) are contiguous stretches of homozygous genotypes, which are a footprint of inbreeding and recessive inheritance. The presence of recessive loci is suggested for Alzheimer's disease (AD); however, their search has been poorly assessed to date. To investigate homozygosity in AD, here we performed a fine-scale ROH analysis using 10 independent cohorts of European ancestry (11,919 AD cases and 9181 controls.) We detected an increase of homozygosity in AD cases compared to controls [ßAVROH (CI 95%) = 0.070 (0.037-0.104); P = 3.91 × 10-5; ßFROH (CI95%) = 0.043 (0.009-0.076); P = 0.013]. ROHs increasing the risk of AD (OR > 1) were significantly overrepresented compared to ROHs increasing protection (p < 2.20 × 10-16). A significant ROH association with AD risk was detected upstream the HS3ST1 locus (chr4:11,189,482â11,305,456), (ß (CI 95%) = 1.09 (0.48 â 1.48), p value = 9.03 × 10-4), previously related to AD. Next, to search for recessive candidate variants in ROHs, we constructed a homozygosity map of inbred AD cases extracted from an outbred population and explored ROH regions in whole-exome sequencing data (N = 1449). We detected a candidate marker, rs117458494, mapped in the SPON1 locus, which has been previously associated with amyloid metabolism. Here, we provide a research framework to look for recessive variants in AD using outbred populations. Our results showed that AD cases have enriched homozygosity, suggesting that recessive effects may explain a proportion of AD heritability.
Assuntos
Doença de Alzheimer , Doença de Alzheimer/genética , Homozigoto , Humanos , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Elevated cerebral levels of amyloid beta-protein (Abeta) occur in Alzheimer's disease (AD), yet only a few patients show evidence of increased Abeta production. This observation suggests that many, perhaps most, cases of AD are caused by faulty clearance of Abeta. Megalin, which plays an important role in mediating Abeta clearance, is an attractive candidate gene for genetic association with AD. To investigate this hypothesis, we analyzed the megalin gene in a population of 2,183 subjects. Genetic analysis indicated that the rs3755166 (G/A) polymorphism located in the megalin promoter associated with risk for AD, dependently of apolipoprotein E genotype. The rs3755166 AA genotype frequency was significantly greater in AD patients than in control subjects. Furthermore, the luciferase reporter assay indicated that the rs3755166 A variant has 20% less transcriptional activity than the rs3755166 G variant. This study provides strong evidence that this megalin polymorphism confers a greater risk for AD, and supports a biological role for megalin in the neurodegenerative processes involved in AD.
Assuntos
Doença de Alzheimer/genética , Polimorfismo Genético , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/imunologia , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/imunologia , Apolipoproteínas E/genética , Apolipoproteínas E/imunologia , Estudos de Casos e Controles , Feminino , Genes , Genótipo , Humanos , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/genética , Proteína-2 Relacionada a Receptor de Lipoproteína de Baixa Densidade/imunologia , Masculino , Estudos Multicêntricos como Assunto , Sequências Reguladoras de Ácido Nucleico , Fatores de RiscoRESUMO
The polymorphic -219T/G variant in the APOE promoter has been associated with variations in basal transcriptional activity as well as with the risk of developing Alzheimer's disease, myocardial infarction and early-onset coronary heart disease. The molecular mechanisms underlying these effects are presently unknown. In this report, we show that nuclear extracts from Jurkat cells form a T-specific complex with a motif including the -219 site within the APOE promoter. By DNA-affinity chromatography and mass spectrometry, the human heterogeneous nuclear ribonucleoprotein hnRNPA1(A1) was identified as one component of the complex. In vitro binding analysis indicated that a fragment of A1 had a marked binding specificity for the T form. Interaction of A1 with this region is driven by an adjacent telomeric-like sequence; however, the presence of G, but not T, at -219 position inhibited this interaction. The differences in transcriptional activity between the -219T and -219G promoter allelic forms correlated with the expression levels of A1 in several cell lines; also, over-expression of A1 increased the activity of the T form relative to that of the G form. These results indicate that A1 transactivates APOE promoter activity by direct and specific interaction with the -219T site.
Assuntos
Apolipoproteínas E/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo A-B/metabolismo , Polimorfismo Genético , Regiões Promotoras Genéticas , Ribonucleoproteínas , Ativação Transcricional , Alelos , Sítios de Ligação , DNA Helicases/metabolismo , Ribonucleoproteína Nuclear Heterogênea A1 , Ribonucleoproteínas Nucleares Heterogêneas Grupo A-B/genética , Humanos , Células Jurkat , Proteínas Nucleares/metabolismo , Proteínas Recombinantes/metabolismo , Sequências Reguladoras de Ácido Nucleico , Hormônios do Timo/metabolismo , Células Tumorais CultivadasRESUMO
To investigate the potential involvement of adrenergic signaling in Alzheimer's disease (AD) pathogenesis, we performed genetic and functional studies of genes initiating the cascade. We chose two functional single-nucleotide polymorphisms (SNPs) in the beta1-adrenergic receptor (ADRB1) and the G protein beta3 subunit (GNB3) genes, respectively, and analyzed their allelic frequencies in a case-control sample of AD. We found that the GNB3 T allele produces a significant risk for AD in individuals homozygous for the ADRB1 C allele, suggesting that the combined effect of both polymorphisms influences AD susceptibility. Interestingly, the co-expression of GNB3 T and ADRB1 C alleles, compared with GNB3 C and ADRB1 G, produced increased cAMP levels and MAPK activation following adrenergic stimulation of transfected human cell lines. Furthermore, the co-expression of these alleles also produced increases in APP expression. These data strongly indicate that the combination of GNB3 and ADRB1 polymorphisms produces AD susceptibility by changing the cell responsiveness to adrenergic stimulation, pointing to the modulation of brain adrenergic receptors as a potential target for novel AD therapeutic strategies.
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Doença de Alzheimer/genética , Subunidades beta da Proteína de Ligação ao GTP/genética , Predisposição Genética para Doença , Polimorfismo de Nucleotídeo Único/genética , Receptores Adrenérgicos beta 1/genética , Idoso , Doença de Alzheimer/epidemiologia , Precursor de Proteína beta-Amiloide/metabolismo , Estudos de Casos e Controles , Células Cultivadas , Distribuição de Qui-Quadrado , AMP Cíclico/metabolismo , Frequência do Gene , Humanos , Modelos Logísticos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fatores de Risco , Espanha/epidemiologia , TransfecçãoRESUMO
Mounting evidence suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of Alzheimer's disease (AD). Epidemiological analyses have shown that HSV-1 is a risk factor for AD in people with at least 1 type 4 allele of the apolipoprotein E gene. Recent studies have also suggested that HSV-1 contributes to the appearance of the biochemical anomalies characteristic of AD brains. In addition, autophagic activity appears to be reduced with aging, and the final stages of autophagy in neurodegenerative process appear to be impaired. The present work reports that HSV-1 provokes the strong intracellular accumulation of both the main species of ß-amyloid (Aß) in the autophagic compartments and that it is associated with a marked inhibition of Aß secretion. Autophagosomes containing Aß failed to fuse with lysosomes in HSV-1-infected cells, indicating the impaired degradation of Aß localized in the autophagic vesicles. In addition, HSV-1 infection was associated with the inhibition of the nonamyloidogenic pathway of amyloid precursor protein (APP) processing without significantly affecting the activity of the secretases involved in the amyloidogenic pathway. Taken together, these data suggest that HSV-1 infection modulates autophagy and amyloid precursor protein processing, contributing to the accumulation of Aß characteristic of AD.
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Peptídeos beta-Amiloides/metabolismo , Proteínas Amiloidogênicas/metabolismo , Autofagia , Herpesvirus Humano 1/fisiologia , Neuroblastoma/metabolismo , Neuroblastoma/virologia , Transdução de Sinais , Linhagem Celular Tumoral , Humanos , Neuroblastoma/patologiaRESUMO
Autophagy is a homeostatic process involved in the turnover or elimination of cytoplasmic components, damaged organelles, and protein aggregates via a lysosomal degradation mechanism. Autophagy also provides a mechanism of innate immunity, known as xenophagy, designed to protect cells from intracellular pathogens, but it may unfortunately be subverted to act as a pro-viral pathway facilitating the replication of certain viruses. Herpes simplex virus type I (HSV-1) is a neurotropic virus that remains latent in host neurons; it is the most common cause of sporadic viral encephalitis. Moreover, HSV-1 has been related to the pathogenesis of Alzheimer's disease. HSV-1 can modulate the autophagic process through a mechanism mediated by the viral protein ICP34.5. Here we report that HSV-1 induces a strong increase in GFP-LC3 and endogenous LC3 lipidation, and triggers the accumulation of intracellular autophagic compartments (mainly autophagosomes) without enhancing autophagic long-lived protein degradation in the late stages of infection. Autophagy inhibition mediated by ATG5 gene silencing had no effect on viral growth. The present results suggest that HSV-1 infection activates the host autophagic machinery and strongly controls the autophagic process, blocking the fusion of autophagosomes with lysosomes. These events might be important in the neurodegenerative process associated with HSV-1 infection.
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Autofagia/fisiologia , Herpesvirus Humano 1/patogenicidade , Neuroblastoma/patologia , Neuroblastoma/virologia , Animais , Linhagem Celular Tumoral , Chlorocebus aethiops , Humanos , Células VeroRESUMO
Insulin-like growth factor I (IGF-I), a neuroprotective factor with a wide spectrum of actions in the adult brain, is involved in the pathogenesis of Alzheimer's disease (AD). Circulating levels of IGF-I change in AD patients and are implicated in the clearance of brain amyloid beta (Aß) complexes. To investigate this hypothesis, we screened the IGF-I gene for various well known single nucleotide polymorphisms (SNPs) covering % of the gene variability in a population of 2352 individuals. Genetic analysis indicated different distribution of genotypes of 1 single nucleotide polymorphism, and 1 extended haplotype in the AD population compared with healthy control subjects. In particular, the frequency of rs972936 GG genotype was significantly greater in AD patients than in control subjects (63% vs. 55%). The rs972936 GG genotype was associated with an increased risk for disease, independently of apolipoprotein E genotype, and with enhanced circulating levels of IGF-I. These findings suggest that polymorphisms within the IGF-I gene could infer greater risk for AD through their effect on IGF-I levels, and confirm the physiological role IGF-I in the pathogenesis of AD.
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Doença de Alzheimer/epidemiologia , Doença de Alzheimer/genética , Fator de Crescimento Insulin-Like I/genética , Polimorfismo de Nucleotídeo Único/genética , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/sangue , Apolipoproteínas E/genética , Análise Mutacional de DNA/métodos , Feminino , Gelsolina/genética , Frequência do Gene , Genótipo , Humanos , Fator de Crescimento Insulin-Like I/metabolismo , Masculino , Pré-Albumina/genética , Fatores de Risco , Espanha/epidemiologia , Estatísticas não ParamétricasRESUMO
We report the fine mapping/sequencing results of promoter and regulatory regions of APOE cluster genes (APOE, APOC1, APOC4, APOC2, and TOMM40) in Alzheimer's disease (AD) risk as well as in the progression from mild cognitive impairment (MCI) to AD. Long-range sequencing in 29 MCI subjects who progressed to dementia revealed 7 novel variants. Two potentially relevant novel variants and 34 single nucleotide polymorphisms (SNPs) were genotyped in a large sample of AD, MCI, and control subjects (n = 1453). Globally, very little association signal was observed in our sample in the absence of APOE ε4. Rs5158 (APOC4 intron 1) and rs10413089 (3' to APOC2) showed a trend toward an increase in AD risk independently from APOE ε4 associated risk though it did not survive multiple test correction (uncorrected p = 0.0099 and 0.01, respectively). Interestingly, rs10413089 showed a similar effect in an independent series. The analysis of the discovery sample showed an association of TOMM40 single nucleotide polymorphisms with progression from MCI stage to AD (rs59007384 and rs11556510), as well as with a shorter time to progression from MCI status to AD (rs10119), though these results could not be replicated in independent series. Further studies are needed to investigate the role of APOE cluster variants in AD risk.