RESUMO
Alzheimer's disease (AD) involves a neurodegenerative process that has not yet been prevented, reversed, or stopped. Continuing with the search for natural pharmacological treatments, flavonoids are a family of compounds with proven neuroprotective effects and multi-targeting behavior. The American genus Dalea L. (Fabaceae) is an important source of bioactive flavonoids. In this opportunity, we tested the neuroprotective potential of three prenylated flavanones isolated from Dalea species in a new in vitro pre-clinical AD model previously developed by us. Our approach consisted in exposing neural cells to conditioned media (3xTg-AD ACM) from neurotoxic astrocytes derived from hippocampi and cortices of old 3xTg-AD mice, mimicking a local neurodegenerative microenvironment. Flavanone 1 and 3 showed a neuroprotective effect against 3xTg-AD ACM, being 1 more active than 3. The structural requirements to afford neuroprotective activity in this model are a 5'-dimethylallyl and 4'-hydroxy at the B ring. In order to search the mechanistic performance of the most active flavanone, we focus on the flavonoid-mediated regulation of GSK-3ß-mediated tau phosphorylation previously reported. Flavanone 1 treatment decreased the rise of hyperphosphorylated tau protein neuronal levels induced after 3xTg-AD ACM exposure and inhibited the activity of GSK-3ß. Finally, direct exposure of these neurotoxic 3xTg-AD astrocytes to flavanone 1 resulted in toxicity to these cells and reduced the neurotoxicity of 3xTg-AD ACM as well. Our results allow us to present compound 1 as a natural prenylated flavanone that could be used as a precursor to development and design of future drug therapies for AD.
Assuntos
Doença de Alzheimer , Flavanonas , Fármacos Neuroprotetores , Camundongos , Animais , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Glicogênio Sintase Quinase 3 beta/metabolismo , Camundongos Transgênicos , Proteínas tau/metabolismo , Flavanonas/farmacologia , Flavanonas/uso terapêutico , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Modelos Animais de Doenças , Fosforilação , Peptídeos beta-Amiloides/metabolismoRESUMO
Neurodegenerative diseases (NDs) represent a global problem on public health, with a growing incidence as human longevity increases. Currently, although there are palliative strategies available for most of these diseases, there is a lack of effective therapies for their cure. Flavonoids are extensively studied for their multi-target behavior. Among numerous biological activities, it has been reported that they act at the CNS level, presenting neuroprotective activity through different mechanisms of action. Dalea L. (Fabaceae) is an American genus, with about 172 species. Dalea elegans Gillies ex. Hook. & Arn and Dalea pazensis Rusby, both South American species, are the important source of natural compounds of the prenylated flavanones type. In the present study, five prenylated flavanones isolated from Dalea species were assayed for their neuroprotective activity in two in vitro models of neurodegeneration. Flavanones 1 and 2 exhibited neuroprotective effects against oxidative stress-induced death in both models, granular cerebellar neurons and (NGF)-differentiated PC12 cells. Structure-activity relationships were also reported. Our results indicated that an 8-prenyl group at the A-ring accompanied by an unsubstituted B-ring, or a 2',4'-dihydroxy-5'-dimethylallyl substitution, lead to the most potent flavanones. Furthermore, in silico studies were performed, and several putative targets in NDs were identified for compounds 1 and 2. Between them, the enzyme acetylcholinesterase was selected for its validation in vitro. The present in vitro and in silico results imply that prenylated flavanones 1 and 2 may be useful in the development and design of future strategies for the treatment of NDs diseases.
Assuntos
Simulação por Computador , Fabaceae/química , Flavanonas/química , Flavanonas/farmacologia , Fármacos Neuroprotetores/química , Fármacos Neuroprotetores/farmacologia , Prenilação , Animais , Diferenciação Celular/efeitos dos fármacos , Flavanonas/isolamento & purificação , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fármacos Neuroprotetores/isolamento & purificação , Estresse Oxidativo/efeitos dos fármacos , Células PC12 , Ratos , Relação Estrutura-AtividadeRESUMO
In previous studies, 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin, a prenylated flavonoid isolated from Dalea elegans roots, showed activity against multiresistant Staphylococcus aureus and Candida albicans, as well as an uncoupling effect on mitochondria and antioxidant activity. The aim of this study was to evaluate the inhibitory effects of 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin and fluconazole on the efflux of rhodamine 6 G in azole-resistant C. albicans 12-99 that expresses multidrug transporters Cdr1p, Cdr2p, and Mdr1p. The effect of fluconazole and 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin on rhodamine 6 G efflux was assessed in both azole-sensitive and azole-resistant C. albicans. Between 1 and 1000 µM, 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin inhibited rhodamine 6 G efflux only in azole-resistant C. albicans 12-99 in a concentration-dependent manner (IC50 = 119 µM); a competitive effect was observed. It also showed selectivity of action in comparison with other flavanones (6-prenylpinocembrin, isolated from aerial parts of D. elegans, pinocembrin, naringenin, and hesperetin, all at 250 µM). To check the possible implications of the inhibition of azole efflux on cell growth, antifungal assays were conducted. Minimal inhibitory concentration values were 150 µM for 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin and higher than 400 µM for fluconazole. The combination of both compounds at either inhibitory or subinhibitory concentrations was significantly more effective than each compound separately. Minimal inhibitory concentration for fluconazole decreased by more than 400 times in the presence of 100 µM 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin, reversing azole resistance and giving values similar to those of azole-sensitive C. albicans. These data are consistent with a dual action of 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-6-prenylpinocembrin: direct antifungal effect on azole-resistant C. albicans 12-99 and inhibition of azole transporters, which results in reversion of fluconazole resistance.