Study on the action mechanism of Buyang Huanwu Decoction against ischemic stroke based on S1P/S1PR1/PI3K/Akt signaling pathway

Abstract

Ethnopharmacological relevance: Ischemic stroke is a common and frequent clinical disease. Recent studies have demonstrated that sphingolipid plays an important role in the pathological process of ischemic stroke. PI3K-Akt is a classic protective signaling pathway of cerebral ischemic injury. After acting on the S1P receptor, S1P can activate the downstream PI3K/Akt signaling pathway and play an anti-cerebral ischemia role. Buyang Huanwu Decoction (BHD) is a traditional Chinese medicine formula used to treat ischemic stroke. However, the mechanisms of BHD on ischemic stroke remain unclear based on S1P/S1PR1/PI3K/Akt signaling pathway.

Aim of the study: The present study is intended to investigate the action mechanism of BHD on ischemic stroke based on the S1P/S1PR1/PI3K/Akt signaling pathway from multiple perspectives.

Materials and methods: The BHD lyophilized product was prepared by vacuum freeze-drying method, of which the chemical composition was determined by UPLC-Q-TOF/MS. The mouse permanent middle cerebral artery occlusion (pMCAO) model was established by the suture-occluded method. Male KM mice were randomly divided into seven groups: sham group, model group, FTY720 (positive control) group, BHD group, BHD + W146 (selective S1PR1 inhibitor) group, SEW2871 (selective S1PR1 agonist) group, and Calycosin group. Each group was administered continuously for 14 days and evaluated with modified neurological severity score (mNSS) and cerebral infarct volume on the 1st, 4th, 7th, and 14th days. The SphK1, SphK2, S1PR1, PI3K, Akt, and p-Akt protein in the prefrontal lobe, hippocampus, and striatum was quantified by Western blot and immunohistochemical (IHC) experiment respectively. The qRT-PCR method was employed to evaluate SphK1, SphK2, and S1PR1 mRNA expression in the above tissue.

Results: BHD and Calycosin both effectively improved mNSS scores with smaller infarct volumes. The SphK1 level in the prefrontal lobe, hippocampus, and striatum of mice in the BHD group was significantly lower, and SphK2, PI3K, and p-Akt in the hippocampus and striatum were significantly higher than those in the model group. BHD significantly decreased SphK1 mRNA expression in the prefrontal lobe, hippocampus, and striatum, and significantly up-regulated SphK2 mRNA and S1PR1 mRNA expression. Additionally, SphK1 protein expression levels of the prefrontal lobe, hippocampus, and striatum in the BHD group was significantly lower than model group, and SphK2, S1PR1, PI3K, Akt, and p-Akt protein expressions levels were increased obviously. Furthermore, SEW2871 can increase S1PR1 and Akt expression, and up-regulate SphK2 and S1PR1 mRNA expression. The effect of BHD on the expression of S1P/S1PR1/PI3K/Akt signaling pathway-related proteins and mRNA were weakened by BHD + W146.

Conclusion: BHD and Calycosin significantly improved the symptoms of neurological deficits in pMCAO mice, reduced the cerebral infarction volume, up-regulated SphK2 and S1PR1 mRNA levels, enhanced SphK2, S1PR1, PI3K, Akt, p-Akt protein expression of the prefrontal lobe, hippocampus and striatum, and down-regulated SphK1 mRNA and protein expression, which may be helpful to clarify the mechanism of BHD through S1P/S1PR1/PI3K/Akt signaling pathway to protect against cerebral ischemic injury.

Keywords: Action mechanism; Buyang Huanwu Decoction; Ischemic stroke; S1P/S1PR1/PI3K/Akt signaling pathway.