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

Rafael Short Ferreira, Paulo Roberto Ribeiro, Juliana Helena Castro E. Silva, Juliana Bender Hoppe, Monique Marylin Alves de Almeida, Beatriz Correia de Lima Ferreira, Gustavo Borges Andrade, Suzana Braga-de-Souza, Luzimar Gonzaga Ferdandez, Maria de Fátima Dias Costa, Christianne Gazzana Salbego, Andrea Rivera, Aline Longoni, Adriano Martimbianco De Assis, Francesca Pieropan, José Cláudio Fonseca Moreira, Silvia Lima Costa, Arthur Butt, Victor Diogenes Amaral Da Silva

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Abstract

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 GFAPEGFP 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.
Original languageEnglish
Article number154
Number of pages17
JournalBMC Complementary Medicine and Therapies
Volume23
DOIs
Publication statusPublished - 11 May 2023

Keywords

  • Amburana cearensis
  • hippocampus
  • oligodendrocyte
  • astrocyte
  • stroke
  • UKRI
  • BBSRC
  • BB/M029379/1
  • MRC
  • MR/33 P025811/1

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