RESUMO
The levels of pro-inflammatory cytokines, such as tumour necrosis factor-alpha (TNF-alpha), are increased in the brain in Alzheimer's disease (AD). Most of the biological properties of TNF-alpha are mediated through its two receptors, tumour necrosis factor receptors I and II (TNF-RI and TNF-RII). We have used immunohistochemistry, Western blotting and real time-PCR (RT-PCR) on frontal (BA 6/24) and temporal (BA 20-22) neocortex and hippocampus from AD and control brains to determine if both receptor proteins were present and expressed in AD and if sequence variations (SNPs) in the promoter regions of the two genes are associated with AD. Expression of TNF-RI exceeded that of TNF-RII in AD and control brains at protein and mRNA levels. The level of TNF-RI protein varied considerably in individual brains but not between AD and control brains. None of the identified TNF-RI and -RII SNPs in the promoter regions of the genes was linked with AD. Our findings suggest that TNF-RI and -RII promoter gene polymorphisms and variations in protein and gene expression of these receptors are unlikely to play a major role in the development of AD.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas , Receptores Tipo II do Fator de Necrose Tumoral/genética , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Idoso , Idoso de 80 Anos ou mais , Sequência de Bases , Encéfalo/metabolismo , Estudos de Casos e Controles , Feminino , Expressão Gênica , Humanos , Imuno-Histoquímica , Masculino , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Estudos Retrospectivos , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Interleukin 10 (IL-10) is an important anti-inflammatory cytokine produced in response to neuroinflammation and might be involved in modulating the progression of Alzheimer's disease (AD) through inhibiting the action of pro-inflammatory cytokines. We have used immunohistochemistry, Western blotting, real time-PCR (RT-PCR) on frontal (BA 6/24) and temporal (BA 20-22) neocortex and hippocampus from AD and control brains as well as genetic association analysis to address the possible involvement of IL-10 in AD. Expression of IL-10 in AD and control brains at both protein and mRNA levels were detected. However, the level of expression, particularly of IL-10 protein, varied considerably in individual brains and we did not find a significant difference between AD and controls. Using direct sequencing we examined five single nucleotide polymorphisms (SNPs) (-3538, -1354, -1087, -824, -597) and two microsatellites (IL-10-G, IL-10-R) in the promoter region of the IL-10 gene. None of the identified SNPs were found to be associated with AD either individually or as haplotypes. Levels of IL-10 protein and gene expression examined also did not appear to be related to AD. Despite this being a relatively small sample, these data suggest that IL-10 does not play a major role in the development of AD.
Assuntos
Doença de Alzheimer , Córtex Cerebral/metabolismo , Interleucina-10/genética , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Córtex Cerebral/citologia , Córtex Cerebral/patologia , Feminino , Predisposição Genética para Doença , Humanos , Interleucina-10/metabolismo , Masculino , Estudos RetrospectivosRESUMO
Polymorphisms in the APOE promoter, ACE1 and CYP46 genes have all been reported to be associated with Alzheimer's disease (AD). We studied the relationship of these polymorphisms to the presence of AD in 86 neuropathologically confirmed cases of AD and 58 controls. In addition, we assessed the effects of these polymorphisms on the accumulation of beta-amyloid (Abeta) in the cerebral parenchyma and vasculature. No association was observed between any of the polymorphisms and the presence of AD, the parenchymal Abeta load or the severity of cerebral amyloid angiopathy (CAA). Here we report that polymorphisms within the APOE promoter, ACE1 and CYP46 gene are not risk factors for AD and are not associated with parenchymal or vascular accumulation of Abeta.
Assuntos
Doença de Alzheimer/genética , Peptídeos beta-Amiloides/genética , Apolipoproteínas E/genética , Peptidil Dipeptidase A/genética , Polimorfismo Genético , Regiões Promotoras Genéticas , Esteroide Hidroxilases/genética , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Colesterol 24-Hidroxilase , Feminino , Frequência do Gene/genética , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Recent findings suggest that production of pro-inflammatory cytokines, such as tumour necrosis factor-alpha (TNF-alpha), is increased in the brains of people with Alzheimer's disease (AD). We used direct sequencing methods on a section of the enhancer/promoter region and on a smaller fragment located 10.5 kb upstream of the TNF-alpha gene to respectively examine TNF-alpha polymorphisms and TNF-a and -b microsatellite alleles in a cohort of 235 post-mortem confirmed AD and 130 control cases. None of the TNF-alpha point mutations or microsatellite alleles investigated proved to be independent risk factors for AD. However, when -308/A, -238/G and TNF-a2 were examined as a 2-1-2 haplotype, we observed that the absence of that haplotype was significantly associated with AD (P = 0.014, Fisher's exact test) suggesting that the 2-1-2 haplotype may be protective against AD.
Assuntos
Doença de Alzheimer/genética , Polimorfismo Genético , Fator de Necrose Tumoral alfa/genética , Idoso , Idoso de 80 Anos ou mais , Alanina/genética , Alelos , Estudos de Casos e Controles , Estudos de Coortes , Elementos Facilitadores Genéticos , Feminino , Frequência do Gene , Glicina/genética , Haplótipos , Humanos , Linfotoxina-alfa/genética , Masculino , Repetições de Microssatélites , Reação em Cadeia da Polimerase , Regiões Promotoras GenéticasRESUMO
Micro-RNAs (miRNAs) are short non-coding RNAs capable of regulating gene expression at the translational level. A number of studies have suggested that the expression of several miRNAs is changed in AD. The pro-inflammatory cytokine tumour necrosis factor-a (TNF-α) is increased in serum and CSF in AD. We measured the expression of TNFA and several AD candidate gene-associated miRNAs (let7a/b, miR-128a/b, miR-27a/b, miR-155) in frontal and temporal neocortex from AD and control brains. The expression of these miRNAs was also measured after incubating non-differentiated (NDC) and retinoic acid -differentiated (DC) SH-SY5Y neuroblastoma cells with TNF-α. TNFA expression was similar in AD and control brains but miR-128a/b levels were significantly reduced in the temporal cortex and miR-128b in the frontal cortex in AD. MiRNA levels did not correlate with TNFA expression in brain tissue but exposure of NDC and DC SH-SY5Y cells to TNF-α caused a variable dose-dependent response in the level of some of the miRNAs studied. Our brain tissue findings argue against a role for TNF-α in influencing the expression of these miRNAs in AD.
RESUMO
Pro-inflammatory cytokines, such as tumour necrosis factor-α (TNF-α), are increased in serum and CSF in Alzheimer's disease (AD). We investigated the effect of TNF-α on gene and protein expression levels of Aß degrading enzymes (ACE, ECE-1, ECE- 2, IDE and NEP) in vitro. Differentiated (DC) and non-differentiated (NDC) neuroblastoma cells (SH-SY5Y) were exposed to TNF-α for 15 minutes and 3 hours and protein and gene expression levels measured using western blotting or sandwich ELISA (ECE-2), and real time-PCR (RT-PCR). Only ECE-2 protein levels decreased significantly in NDCs in a dose-dependent manner after 15 minutes of TNF-α exposure but reverted to basal levels after 3 hours. Basal NEP gene expression levels were higher in control DCs compared to NDCs but TNF-α treatment did not significantly alter the levels of expression of any of the Aß degrading enzymes. In conclusion, apart from a transient reduction in ECE-2 protein levels, TNF-α had no impact in our in vitro experimental system on transcription or translation of any of our selected mediators of Aß degradation.
RESUMO
Levels of tumor necrosis factor-alpha (TNF-alpha) are increased in the brain in Alzheimer's disease (AD). The TNF-alpha/TNF-R signaling pathways involve complex interactions between several proteins, including TNF-receptor-associated factor-2 (TRAF-2). We have examined the distribution and levels of TRAF-2 in AD and control brains and also whether single nucleotide polymorphisms (SNPs) in the TRAF-2 gene are associated with AD and influence TRAF-2 expression. Immunohistochemistry demonstrated TRAF-2 in AD and control cortex in neurons, within plaque-associated neurites and some neurofibrillary tangles. Western blots revealed a band of the expected apparent molecular mass (approximately 50kDa) for TRAF-2, in homogenates of AD and control cortex. RT-PCR showed the levels of TRAF-2 mRNA to be significantly higher in the frontal cortex of AD than control brains (p=0.015). TRAF-2 mRNA expression was not linked to any SNPs. The 3' UTR SNP (rs7852970) GG allele was significantly protective against AD (p=0.030). Our findings suggest that the TRAF-2 pathway is involved AD. The mechanisms are currently unclear and need further examination.