RESUMO
Lower levels of the cognitively beneficial docosahexaenoic acid (DHA) are often observed in Alzheimer's disease (AD) brains. Brain DHA levels are regulated by the blood-brain barrier (BBB) transport of plasma-derived DHA, a process facilitated by fatty acid-binding protein 5 (FABP5). This study reports a 42.1 ± 12.6% decrease in the BBB transport of 14 C-DHA in 8-month-old AD transgenic mice (APPswe,PSEN1∆E9) relative to wild-type mice, associated with a 34.5 ± 6.7% reduction in FABP5 expression in isolated brain capillaries of AD mice. Furthermore, short-term spatial and recognition memory deficits were observed in AD mice on a 6-month n-3 fatty acid-depleted diet, but not in AD mice on control diet. This intervention led to a dramatic reduction (41.5 ± 11.9%) of brain DHA levels in AD mice. This study demonstrates FABP5 deficiency and impaired DHA transport at the BBB are associated with increased vulnerability to cognitive deficits in mice fed an n-3 fatty acid-depleted diet, in line with our previous studies demonstrating a crucial role of FABP5 in BBB transport of DHA and cognitive function.
Assuntos
Barreira Hematoencefálica , Transtornos Cognitivos/etiologia , Ácidos Docosa-Hexaenoicos/farmacocinética , Proteínas de Ligação a Ácido Graxo/fisiologia , Proteínas de Neoplasias/fisiologia , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Química Encefálica , Transtornos Cognitivos/genética , Transtornos Cognitivos/metabolismo , Gorduras na Dieta/administração & dosagem , Ácidos Docosa-Hexaenoicos/deficiência , Proteínas de Escherichia coli , Proteínas de Ligação a Ácido Graxo/biossíntese , Ácidos Graxos Ômega-3/deficiência , Feminino , Humanos , Masculino , Aprendizagem em Labirinto , Transtornos da Memória/etiologia , Transtornos da Memória/genética , Transtornos da Memória/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mutação de Sentido Incorreto , Proteínas de Neoplasias/biossíntese , Polissacarídeo-Liases , Presenilina-1/genética , Presenilina-1/metabolismo , Reconhecimento Psicológico , Proteínas Recombinantes de Fusão/metabolismoRESUMO
INTRODUCTION: The insulin-regulated aminopeptidase (IRAP) is expressed in several cell types, where it is mainly located in specialized secretory endosomes that are quickly recruited to the cell surface upon cell type-specific activation. Here we describe for the first time the expression and subcellular distribution of IRAP in macrophages. METHODS: IRAP mRNA expression, protein expression and presence at the cell surface was investigated by real-time polymerase chain reaction (PCR), Western blot and [(3)H]IVDE77 binding, respectively. RESULTS: IRAP mRNA expression was increased by interferon-γ (IFN-γ) and lipopolysaccharide (LPS), but not by anti-inflammatory cytokines (interleukin (IL)-4, IL-10, transforming growth factor ß (TGF-ß)). IFN-γ increased [(3)H]IVDE77 binding steadily over time, while LPS quickly and transiently recruited IRAP to the cell surface. Combined stimulations with IFN-γ and LPS showed the same pattern as LPS alone. Latex particles also induced a transient recruitment of IRAP to the cell surface, but no difference was observed in phagocytic uptake between wild-type and IRAP(-/-) macrophages, suggesting that the enzymatic activity of IRAP is not required for the ingestion of particles. CONCLUSION: IRAP is more highly expressed in pro-inflammatory M1-activated macrophages and its presence at the cell surface is modulated upon exposure to IFN-γ, LPS or exogenous particles.
Assuntos
Cistinil Aminopeptidase/metabolismo , Macrófagos Peritoneais/enzimologia , Células 3T3-L1 , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Cistinil Aminopeptidase/deficiência , Cistinil Aminopeptidase/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Glucose/metabolismo , Inflamação/patologia , Interferon gama/farmacologia , Espaço Intracelular/efeitos dos fármacos , Espaço Intracelular/metabolismo , Lectinas Tipo C/metabolismo , Ligantes , Lipopolissacarídeos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos Peritoneais/efeitos dos fármacos , Receptor de Manose , Lectinas de Ligação a Manose/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , NF-kappa B/metabolismo , Fagocitose/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Receptores de Superfície Celular/metabolismoRESUMO
It is proposed that insulin-regulated aminopeptidase (IRAP) is the site of action of two peptides, angiotensin IV and LVV-hemorphin 7, which have facilitatory effects on learning and memory. In fat and muscles, IRAP codistributes with the insulin-responsive glucose transporter GLUT4 in specialised vesicles, where it plays a role in the tethering and/or trafficking of these vesicles. This study investigated whether an analogous system exists in two functionally distinct regions of the brain, the hippocampus and the cerebellum. In the hippocampus, IRAP was found in the pyramidal neurones where it exhibited a high degree of colocalisation with GLUT4. Consistent with the role of GLUT4 in insulin-responsive tissues, the glucose transporter was thought to be responsible for facilitating glucose uptake into these pyramidal neurones in response to potassium-induced depolarisation or cAMP activation as the glucose influx was sensitive to indinavir treatment. Angiotensin IV and LVV-hemorphin 7 enhanced this activity-dependent glucose uptake in hippocampal slices. In contrast, in the cerebellum, where the distribution of IRAP was dissociated from GLUT4, the effect of the peptides on glucose uptake was absent. We propose that the modulation of glucose uptake by angiotensin IV and LVV-hemorphin 7 is region-specific and is critically dependent on a high degree of colocalisation between IRAP and GLUT4. These findings also confirm a role for IRAP and GLUT4 in activity-dependent glucose uptake in hippocampal neurones.
