Amburana cearensis seed extract stimulates astrocyte glutamate homeostatic mechanisms in hippocampal brain slices and protects oligodendrocytes against ischemia.

BACKGROUND: Stroke is a leading cause of death and disability worldwide. A major factor in brain damage following ischemia is excitotoxicity caused by elevated levels of the neurotransmitter glutamate. In the brain, glutamate homeostasis is a primary function of astrocytes. Amburana cearensis has long been used in folk medicine and seed extract obtained with dichloromethane (EDAC) have previously been shown to exhibit cytoprotective activity in vitro. The aim of the present study was to analyse the activity of EDAC in hippocampal brain slices. METHODS: We prepared a dichloromethane extract (EDAC) from A. cearensis seeds and characterized the chemical constituents by 1H and 13C-NMR. Hippocampal slices from P6-8 or P90 Wistar rats were used for cell viability assay or glutamate uptake test. Hippocampal slices from P10-12 transgenic mice SOX10-EGFP and GFAP-EGFP and immunofluorescence for GS, GLAST and GLT1 were used to study oligodendrocytes and astrocytes. RESULTS: Astrocytes play a critical role in glutamate homeostasis and we provide immunohistochemical evidence that in excitotoxicity EDAC increased expression of glutamate transporters and glutamine synthetase, which is essential for detoxifying glutamate. Next, we directly examined astrocytes using transgenic mice in which glial fibrillary acidic protein (GFAP) drives expression of enhanced green fluorescence protein (EGFP) and show that glutamate excitotoxicity caused a decrease in GFAP-EGFP and that EDAC protected against this loss. This was examined further in the oxygen-glucose deprivation (OGD) model of ischemia, where EDAC caused an increase in astrocytic process branching, resulting in an increase in GFAP-EGFP. Using SOX10-EGFP reporter mice, we show that the acute response of oligodendrocytes to OGD in hippocampal slices is a marked loss of their processes and EDAC protected oligodendrocytes against this damage. CONCLUSION: This study provides evidence that EDAC is cytoprotective against ischemia and glutamate excitotoxicity by modulating astrocyte responses and stimulating their glutamate homeostatic mechanisms.

Genistein protects against amyloid-beta-induced toxicity in SH-SY5Y cells by regulation of Akt and Tau phosphorylation.

Alzheimer's disease is a neurodegenerative disorder characterized by extracellular deposition of amyloid-ß (Aß) peptide and hyperphosphorylation of Tau protein, which ultimately leads to the formation of intracellular neurofibrillary tangles and cell death. Increasing evidence indicates that genistein, a soy isoflavone, has neuroprotective effects against Aß-induced toxicity. However, the molecular mechanisms involved in its neuroprotection are not well understood. In this study, we have established a neuronal damage model using retinoic-acid differentiated SH-SY5Y cells treated with different concentrations of Aß25-35 to investigate the effect of genistein against Aß-induced cell death and the possible involvement of protein kinase B (PKB, also termed Akt), glycogen synthase kinase 3ß (GSK-3ß), and Tau as an underlying mechanism to this neuroprotection. Differentiated SH-SY5Y cells were pre-treated for 24 hr with genistein (1 and 10 nM) and exposed to Aß25-35 (25 µM), and we found that genistein partially inhibited Aß induced cell death, primarily apoptosis. Furthermore, the protective effect of genistein was associated with the inhibition of Aß-induced Akt inactivation and Tau hyperphosphorylation. These findings reinforce the neuroprotective effects of genistein against Aß toxicity and provide evidence that its mechanism may involve regulation of Akt and Tau proteins.

Anticancer activity of flavonoids isolated from Achyrocline satureioides in gliomas cell lines.

Achyrocline satureioides, popularly known as "marcela", is a medicinal plant found in South America. This plant is rich in flavonoids, which have been reported to exert numerous biological activities. The aim of this study was to purify, identify and evaluate the mechanisms underlining anticancer activity of A. satureioides flavonoids in glioma cell lines (U87, U251 and C6) as well as their comparative toxicity in normal brain cells (primary astrocytes, neurons and organotypic hippocampal cultures). The main flavonoids present in A. satureioides are luteolin, quercetin, 3-O-methyl-quercetin and achyrobichalcone, the later a very unique metabolite present in this plant. Isolated flavonoids as well as A. satureioides extracts reduced proliferation and clonogenic survival, and induced apoptosis of glioma cell lines. In addition, A. satureioides flavonoids potentiated the cytotoxic effect and apoptosis induction by the glioma chemotherapeutic temozolomide (TMZ). Importantly, A. satureioides flavonoids were less cytotoxic to astrocytes, neuron:astrocytes co-cultures and hippocampal cultures if compared to gliomas. Investigation of 10 cancer-related pathways showed a reduced activation of MYC and the Map kinases ERK and JNK by A. satureioides flavonoid-enriched extract, an effect not observed when individual flavonoids were evaluated. Altogether, the herein presented results show that A. satureioides extract possesses a combination of flavonoids, some unique for this plant, which have synergistic anticancer activity and potential for further studies in vivo.