Abstract
The present study explored the effect and mechanism of repeatedly steamed and sundried Rehmanniae Radix Praeparata(RRP) in delaying brain aging in ovariectomized mice. After ovariectomy, the mice were randomly divided into a model group, an estradiol valerate group(0.3 mg·kg~(-1)), and low-(1.0 g·kg~(-1)), medium-(2.0 g·kg~(-1)), and high-dose(4.0 g·kg~(-1)) RRP groups, and a sham operation group was also set up, with 15 mice in each group. One week after the operation, intragastric administration was carried out for 15 consecutive weeks. The step-down test and Morris water maze test were used to detect the behavioral changes of mice. HE staining and Nissl staining were used to observe the morphological changes of mouse brain tissues. Immunohistochemistry was used to detect the expression of Aβ and ER_β in mouse brain tissues. The serum estrogen levels and cholinesterase and cholinesterase transferase levels in brain tissues of mice were detected by assay kits. The extracted hippocampal protein was detected by the Nano-ESI-LC-MS system, identified by the Protein Discovery, and analyzed quantitatively and qualitatively by the SIEVE. The PANTHER Classification System was used for GO analysis and KEGG pathway enrichment analysis of the differential proteins. Compared with the sham operation group, the model group showed decreased learning and memory ability, shortened step-down latency(P<0.05), prolonged escape latency(P<0.05), reduced platform crossings and residence time in the target quadrant, scattered nerve cells in the hippocampus with enlarged intercellular space, increased expression of Aβ-positive cells(P<0.05), declining expression of ER_β-positive cells and estrogen level(P<0.05), and weakened cholinergic function(P<0.05). Compared with the model group, the RRP groups showed improved learning and memory ability, prolonged step-down latency(P<0.05), increased estrogen level(P<0.05), neatly arranged nerve cells in the hippocampus with complete morphology, declining Aβ-positive cells, and elevated expression of ER_β-positive cells. A total of 146 differential proteins were screened out by proteomics, and KEGG pathway enrichment yielded 75 signaling pathways. The number of proteins involved in the dopaminergic synapse signaling pathway was the largest, with 13 proteins involved. In summary, RRP can delay brain aging presumedly by increasing the level of estrogen, mediating the dopaminergic synapse signaling pathway, and improving cholinergic function.
