The Effects and Regulatory Mechanism of Flavonoids from Stems and Leaves of Scutellaria baicalensis Georgi in Promoting Neurogenesis and Improving Memory Impairment Mediated by the BDNF-ERK-CREB Signaling Pathway in Rats

Abstract

Background: It is well known that Alzheimer's Disease (AD) is a neurodegenerative disease accompanied by memory impairment and major pathological changes of the extracellular Senile Plaque (SP) and intracellular Neurofibrillary Tangles (NFTs). However, many pieces of evidence indicate that neurogenesis disorders are also regarded as a new opinion in AD. Objective: This study aims to investigate the effects and regulatory mechanism of flavonoids from the stems and leaves of Scutellaria baicalensis Georgi in promoting neurogenesis and improving memory impairment mediated by BDNF-ERK-CREB signaling pathway in rats. Methods: Male Wistar rats were intracerebroventricularly injected with amyloid-beta protein 25-35 (Aβ25-35) in combination with Aluminum Trichloride (Alcl3) and recombinant human transforming growth factor-β1 (RHTGF-β1) (composited Aβ), to establish an AD model. Morris water maze was used to screen AD model rats and measure the learning and memory ability of model rats. The expression of Ki67 protein, which is involved in cell neurogenesis, in the hippocampal gyrus of rats was detected by the immunohistochemical method. The mRNA and protein expression levels of Grb2, SOS1, Ras, ERK, and BDNF, in the BDNF-ERK-CREB signaling pathway, in the hippocampus and cerebral cortex regions of rats were assayed by the Quantitative real-time PCR (qPCR) and Western blotting methods, respectively. Results: Intracerebroventricular injection of composited Aβ could induce rats’ memory impairment, decrease the protein expression of Ki67 in the hippocampal gyrus, and increase the mRNA and protein expression levels of Grb2, SOS1, Ras, ERK, and BDNF in the hippocampus and cerebral cortex. However, SSF could significantly ameliorate rats’ memory impairment induced by composited Aβ, lower the Ki67 protein expression in the hippocampal gyrus, and regulate the abnormal mRNA and protein expression levels of Grb2, SOS1, Ras, ERK and BDNF in the hippocampus and cerebral cortex regions of rat brains. Conclusion: Composited Aβ induced memory impairment, decreased neurogenesis and initiated the abnormal mRNA and protein expressions of Grb2, SOS1, Ras, ERK, and BDNF in the BDNF- ERK-CREB signaling pathway. The effects of SSF in promoting neurogenesis and improving memory impairment may be related to the regulation of the abnormal expressions of Grb2, SOS1, Ras, ERK, and BDNF molecules in the BDNF-ERK-CREB signaling pathway.