RESUMEN
A healthy lifestyle, including regular physical exercise, is generally believed to improve cognitive function and enhance neurogenesis. Such physical exercise-induced effects are associated with increased brain expression of neurotrophic and growth factors. In the present study, we investigated Bdnf, Igf-1, Fgf-2, Egf, and VegfA messenger RNA (mRNA) expression levels in the male rat hippocampus and frontal cortex after 2 weeks of voluntary physical exercise. Whereas the expression of Fgf-2 was upregulated in the hippocampus and prefrontal cortex by physical exercise, the expression levels of Bdnf transcript 1, Bdnf transcript 4, Igf-1, and VegfA were upregulated only in the hippocampus. We focused our subsequent analyses on the VegfA gene, which encodes vascular endothelial growth factor, a signaling molecule important for angiogenesis, vasculogenesis, and neurogenesis. To study the epigenetic mechanisms involved in the physical exercise-mediated induction of VegfA expression, we used oxidative and non-oxidative bisulfite pyrosequencing to analyze VegfA promoter DNA methylation and DNA hydroxymethylation. We observed discrete DNA hypomethylation at specific CpG sites in rats that engaged in physical exercise relative to sedentary rats. This is exemplified by a CpG site located within a VegfA promoter Sp1/Sp3 transcription factor recognition element. DNA hydroxymethylation was present at the VegfA promoter, but no differences in DNA hydroxymethylation were observed in rats that engaged in physical exercise relative to sedentary rats. Moreover, we observed increased Tet1 and decreased Dnmt3b mRNA expression in the hippocampi of rats that engaged in physical exercise. The presented results substantiate the involvement of epigenetics as a mediator of the beneficial effects of physical exercise and point to the importance of analyzing factors beyond Bdnf to delineate the mechanisms behind the functional impacts of physical exercise in mediating benefits to the brain.
Asunto(s)
Epigénesis Genética , Hipocampo/metabolismo , Condicionamiento Físico Animal , Factor A de Crecimiento Endotelial Vascular/genética , Acetilación , Animales , Islas de CpG/genética , Metilación de ADN/genética , Histonas/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Lisina/metabolismo , Masculino , Factores de Crecimiento Nervioso/metabolismo , Corteza Prefrontal/metabolismo , Regiones Promotoras Genéticas/genética , Unión Proteica , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas Wistar , Elementos de Respuesta/genética , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
Physical exercise results in the increased expression of neurotrophic factors and the subsequent induction of signal transduction cascades with a positive impact on neuronal functions. In this study, we used a voluntary physical exercise rat model to determine correlations in hippocampus mRNA expression of the neurotropic factors Bdnf, VegfA, and Igf1; their receptors TrkB, Igf1R, VegfR1, and VegfrR2; and downstream signal transducers Creb, Syn1, and Vgf. In hippocampi of physically exercised rats, the mRNA expression levels of Bdnf transcript 4 (Bdnf-t4), VegfA, and Igf1, as well as VegfR1, TrkB, Creb, Vgf, and Syn1, were increased. Bdnf-t4 mRNA expression positively correlated with mRNA expression of Creb, Vgf, and Syn1 in hippocampi of exercised rats. A correlation between Bdnf-t4 and Syn1 mRNA expression was also observed in hippocampi of sedentary rats. Igf1 and VegfA mRNA expression was positively correlated in hippocampi of both exercised and sedentary rats. But, neither Igf1 nor VegfA mRNA expression was correlated with the expression of Bdnf-t4 or the expression of the signal transducers Creb, Syn1, and Vgf. In hippocampi of exercised rats, Creb mRNA expression was positively correlated with TrkB, Syn1, and Vgf mRNA expression and with the correlation between Creb and Vgf mRNA expression also observed in hippocampi of sedentary rats. To examine for causality of the in vivo observed correlated mRNA expression levels between Bdnf-t4 and the other examined transcripts, we used nuclease-deactivated CRISPR-Cas9 fused with VP64 to induce mRNA expression of endogenous Bdnf-t4 in rat PC12 cells. Following Bdnf-t4 mRNA induction, we observed increased Creb mRNA expression. This in vitro result is in accordance with the in vivo results and supports that under specified conditions, an increase in Creb mRNA expression can be a downstream signal transduction event due to induction of endogenous Bdnf mRNA expression.
Asunto(s)
Hipocampo/metabolismo , Factores de Crecimiento Nervioso/metabolismo , Condicionamiento Físico Animal , ARN Mensajero/genética , Transducción de Señal , Animales , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/genética , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Células HEK293 , Hipocampo/fisiología , Humanos , Masculino , Neuropéptidos/genética , Neuropéptidos/metabolismo , Células PC12 , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Receptor IGF Tipo 1/genética , Receptor IGF Tipo 1/metabolismo , Receptor trkB/genética , Receptor trkB/metabolismo , Receptores de Factores de Crecimiento Endotelial Vascular/genética , Receptores de Factores de Crecimiento Endotelial Vascular/metabolismo , Sinapsinas/genética , Sinapsinas/metabolismoRESUMEN
Reported is the gram-scale synthesis of tert-butyldiphenylsilyl 4-(N-benzyloxycarbonyl)-amino-2-azido-2,4,6-trideoxy-ß-D-galactopyranoside, which represents an orthogonally protected 2,4-diamino-D-fucose building block, a common constituent of various zwitterionic polysaccharides. The building block has been synthesized from D-glucosamine in 19% overall yield over 14 steps, requiring 5 chromatographic purifications. The key step in the synthesis is the introduction of the C-4 amino substituent, which has been accomplished by a one-pot three step procedure, involving regioselective C-3-O-trichloroacetimidate formation, C-4-O-triflation, and intramolecular substitution. The building block can be used as an acceptor and is readily transformed into a donor glycoside.
