RESUMO
ObjectiveTo investigate the impact of early intervention with Yishen Huazhuo prescription （YHP） on the learning and memory of accelerated aging model mice， as well as its underlying mechanism. MethodForty-eight 3-month-old male SAMP8 mice were randomly assigned into four groups， including the model group， low-dose YHP group， high-dose YHP group， and donepezil group. Additionally， 24 SAMR1 mice of the same age were divided into a control group and a YHP treatment control group， each consisting of 12 mice. The YHP groups received YHP at doses of 6.24 g·kg-1 and 12.48 g·kg-1， while the donepezil group was treated with donepezil at a dose of 0.65 mg·kg-1. The model group and control groups were given physiological saline. The mice were gavaged once daily for a duration of four weeks. Spatial learning and memory abilities of mice were assessed using the Morris water maze test. Immunofluorescence staining was employed to evaluate neuronal density as well as expression levels of M1 microglial （MG） polarization marker inducible nitric oxide synthase （iNOS） and M2 MG polarization marker arginase-1 （Arg-1） in the hippocampus region. Enzyme-linked immunosorbent assay （ELISA） was used to measure serum levels of pro-inflammatory factor interleukin 1β （IL-1β） and anti-inflammatory factor transforming growth factor-β1 （TGF-β1）. Furthermore， Western blot analysis was conducted to determine expressions of amyloid β peptide1-42 （Aβ1-42） along with triggering receptor expressed on myeloid cells 2 （TREM2）/nuclear factor kappa B （NF-κB） signaling pathway-related proteins TREM2， phospho （p）-NF-κB p65， and phospho-inhibitory kappa B kinase β （IKKβ） in the hippocampus. ResultCompared with the control group， the model group exhibited a significantly prolonged escape latency （P<0.01）， a significant reduction in neuron-specific nuclear protein （NeuN） expression in the hippocampus， a significant increase in iNOS expression in MG， and a significant decrease in Arg-1 expression. The serum IL-1β content was significantly increased， while the TGF-β1 content was significantly decreased. Additionally， there was a significant decrease in TREM2 expression in the hippocampus and significant increases in p-NF-κB p65， p-IKKβ， and Aβ1-42 expressions （P<0.05， P<0.01）. However， no significant changes were observed in escape latency， times of crossing the platform， and hippocampal NeuN expression in the YHP treatment control group. Conversely， iNOS expression in MG as well as the hippocampal p-NF-κB p65， p-IKKβ， and Aβ1-42 expressions were significantly decreased. Furthermore， TREM2 expression was significantly increased （P<0.05， P<0.01）. In comparison to the model group， the low-dose YHP group showed a significantly shortened escape latency and an increased number of crossing the platform （P<0.05， P<0.01）. In the high-dose YHP group， the escape latency was significantly shortened （P<0.05）. In the low-dose YHP group， high-dose YHP group， the expression of NeuN in the hippocampus was significantly increased， the expression of iNOS in MG was significantly decreased， and the expression of Arg-l was significantly increased. The serum IL-1β content was significantly decreased， while the TGF-β1 content was significantly increased. Furthermore， the expression of TREM2 in the hippocampus was significantly increased， and the expressions of p-NF-κB p65， p-IKKβ， and Aβ1-42 were significantly decreased （P<0.01）. ConclusionEarly YHP intervention may promote the transformation of hippocampal MG from M1 to M2 by regulating the TREM2/NF-κB signaling pathway， reduce the release of neuroinflammatory factors， protect hippocampal neurons， and reduce the deposition of Aβ1-42， and finally delay the occurrence of learning and memory decline in SAMP8 mice.