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
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.