RESUMO
Alzheimer's disease (AD) is a progressive degenerative disorder and the most common cause of dementia in aging populations. Although the pathological hallmarks of AD are well defined, currently no effective therapy exists. Liver growth factor (LGF) is a hepatic albumin-bilirubin complex with activity as a tissue regenerating factor in several neurodegenerative disorders such as Parkinson's disease and Friedreich's ataxia. Our aim here was to analyze the potential therapeutic effect of LGF on the APPswe mouse model of AD. Twenty-month-old mice received intraperitoneal (i.p.) injections of 1.6 µg LGF or saline, twice a week during three weeks. Mice were sacrificed one week later, and the hippocampus and dorsal cortex were prepared for immunohistochemical and biochemical studies. LGF treatment reduced amyloid-ß (Aß) content, phospho-Tau/Tau ratio and the number of Aß plaques with diameter larger than 25 µm. LGF administration also modulated protein ubiquitination and HSP70 protein levels, reduced glial reactivity and inflammation, and the expression of the pro-apoptotic protein Bax. Because the administration of this factor also restored cognitive damage in APPswe mice, we propose LGF as a novel therapeutic tool that may be useful for the treatment of AD.
Assuntos
Doença de Alzheimer/etiologia , Doença de Alzheimer/metabolismo , Bilirrubina/genética , Bilirrubina/metabolismo , Suscetibilidade a Doenças , Albumina Sérica Humana/genética , Albumina Sérica Humana/metabolismo , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Animais , Comportamento Animal , Córtex Cerebral/metabolismo , Córtex Cerebral/patologia , Modelos Animais de Doenças , Expressão Gênica , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Memória de Curto Prazo , Camundongos , Camundongos Transgênicos , Microglia/metabolismo , Fosforilação , Placa Amiloide/etiologia , Placa Amiloide/metabolismo , Placa Amiloide/patologia , Ubiquitinação , Proteínas tau/metabolismoRESUMO
Parkinson's disease is a neurodegenerative disorder characterized by the progressive death of dopaminergic (DA) neurons in the substantia nigra (SN), which leads to a loss of the neurotransmitter dopamine in the basal ganglia. Current treatments relieve the symptoms of the disease, but none stop or delay neuronal degeneration. Liver growth factor (LGF) is an albumin-bilirubin complex that stimulates axonal growth in the striatum and protects DA neurons in the SN of 6-hydroxydopamine-lesioned rats. Our previous results suggested that these effects observed in vivo are mediated by microglia and/or astrocytes. To determine if these cells are LGF targets, E14 (embryos from Sprague Dawley rats of 14 days) rat mesencephalic glial cultures were used. Treatment with 100 pg/mL of LGF up-regulated the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinases 1/2 (ERK1/2) and the cyclic AMP response element binding protein (CREB) phosphorylation in glial cultures, and it increased the microglia marker Iba1 and tumor necrosis factor alpha (TNF-alpha) protein levels. The treatment of E14 midbrain neurons with a glial-conditioned medium from LGF-treated glial cultures (GCM-LGF) prevented the loss of DA neurons caused by 6-hydroxy-dopamine. This neuroprotective effect was not observed when GCM-LGF was applied in the presence of a blocking antibody of TNF-alpha activity. Altogether, our findings strongly suggest the involvement of microglia and TNF-alpha in the neuroprotective action of LGF on DA neurons observed in vitro.
