Xiao-xu-ming Decoction Improved Synaptic Damage after Acute Cerebral Ischemia and Reperfusion via JAK2/STAT3 Pathway in Rats

Ethnopharmacological relevance: Ischemic stroke is an important cause of death and disability worldwide. Xiao-xu-ming Decoction (XXMD) is a classic prescription for the treatment of stroke patients, which has been widely used in China and has significant therapeutic effect, but the therapeutic target and mechanism are still unclear.

Aim of the study: The current study aimed to investigate temporal alternation of synaptic damage and the protective effects of XXMD on synaptic damage following cerebral ischemia and reperfusion in vivo.

Materials and methods: Adult male Sprague-Dawley (SD) rats subjected to 90 mins of middle cerebral artery occlusion (MCAO) and subsequent reperfusion at various time points. Neurobehavioral function was assessed using modified neurological severity scores (mNSS), while pro-inflammatory cytokine levels were measured using ELISA kits. Histological assessment involved silver staining and Luxol Fast Blue (LFB) staining, and the ultrastructural alterations in neurons and synapses were examined using a transmission electron microscope (TEM). Golgi-cox staining was used to evaluate the density of dendritic spines. Levels of synapse-related proteins were quantified via immunofluorescence staining and Western blotting. Additionally, JAK2/STAT3 pathway related protein levels were assessed using Western blotting. In the second part, the rats were randomly divided into sham operation group, 24 hours of reperfusion group, and XXMD group. The ultrastructural alterations and dendrite spine density of synapses were observed by TEM and Golgi-Cox staining respectively, and the expression levels of SYN, PSD95, GAP43, p-JAK2 and p-STAT3 were evaluated by WB.

Results: Findings included deteriorated neurobehavioral function, increased release of IL-6, IL-1β, and TNFα, and time-dependent neuronal and synaptic damages during the initial phase of ischemia and reperfusion. At the ultrastructural level, neurons and synapses exhibited structural failure in the peri-infarct cortex. In addition, golgi-cox staining showed dendritic density in ischemic cortex significantly reduced after cerebral ischemia and reperfusion. Moreover, significant reductions in SYN, PSD95, and GAP43 expression levels, along with increases in p-JAK2 and p-STAT3 expression levels, were observed after cerebral ischemia and reperfusion. Meantime, XXMD significantly reduced synaptic impairment and down-regulated SYN, GAP43, PSD95 expression and phosphorylation expression of JAK2 and STAT3 following MCAO and 24 hours of reperfusion.

Conclusion: Collectively, these results indicates XXMD may play a neuroprotective role in reducing synaptic damage via JAK2/STAT3 signaling pathway.