Tongqiao Huoxuetang Improves Neurological Deficits in CIRI Rats by Regulating Glu-Gln Circulation to Reduce Glutamate Excitotoxicity of Astrocytes / 中国实验方剂学杂志

ABSTRACT

Objective:To observe and compare the protective effects of Tongqiao Huoxue decoction （TQHX） prepared by three methods against cerebral ischemia-reperfusion injury （CIRI）， and to explore its mechanism through the glutamate （Glu） metabolic pathway in astrocytes. Method:The male SD rats of SPF grade were subjected to CIRI model induction by the modified middle cerebral artery occlusion method. The model rats were randomly divided into a model group， a sham operation group， and water-decocted， wine-decocted， and alcohol-extracted TQHX （6.3 g·kg^-1·d^-1） groups. The rats were treated correspondingly for 7 days. Those in the sham operation group and the model group were treated with an equal volume of normal saline by gavage. After the final treatment， the neurological function of rats was assessed by the modified neurological severity score （mNSS）. Hematoxylin-eosin （HE） staining was used to observe the morphological changes of ischemic brain tissues in rats. High-performance liquid chromatography （HPLC） was used to detect glutamate （Glu） in ischemic brain tissues. The expression of glutamate transporter-1 （GLT-1） and glial fibrillary acidic protein （GFAP） and co-expression of glutamine synthetase （GS） and GFAP in ischemic brain tissues were detected by immunofluorescence assay. Western blot was used to detect the protein expression of GFAP， GLT-1， and GS. Result:Compared with the sham operation group， the model group showed increased mNSS （<italic>P</italic><0.01）， large necrosis of cerebral cortex in ischemic brain tissues with disordered cell arrangement， obscure boundary， intracellular edema， and inflammatory infiltration， elevated Glu in ischemic brain tissues （<italic>P</italic><0.01）， declining GLT-1-GFAP co-expression and GS-GFAP co-expression （<italic>P</italic><0.01）， up-regulated expression of GFAP protein， and reduced protein expression of GLT-1 and GS（<italic>P<</italic>0.05，<italic>P<</italic>0.01）. Compared with the model group， the TQHX groups showed decreased mNSS （<italic>P<</italic>0.01）， relieved injury in the cerebral cortex and hippocampal nerve cells in ischemic brain tissues， reduced Glu expression（<italic>P<</italic>0.05，<italic>P<</italic>0.01）， elevated co-expression of GLT-1 and GFAP （<italic>P<</italic>0.05，<italic>P<</italic>0.01）， and up-regulated protein expression of GFAP and GLT-1（<italic>P<</italic>0.05，<italic>P<</italic>0.01）. The co-expression of GS and GFAP （<italic>P<</italic>0.05，<italic>P<</italic>0.01）and the expression of GS （<italic>P<</italic>0.01）were increased in the wine-decocted and alcohol-extracted TQHX groups. Compared with the water-decocted TQHX group， the alcohol-extracted group showed increased GLT-1-GFAP and GS-GFAP co-expression（<italic>P<</italic>0.05）； the wine-decocted and alcohol-extracted TQHX groups exhibited elevated GS protein expression （<italic>P<</italic>0.05）； the alcohol-extracted TQHX group displayed declining Glu content （<italic>P</italic><0.01） and increased protein expression of GFAP and GLT-1 （<italic>P<</italic>0.05， <italic>P<</italic>0.01）. Compared with the wine-decocted TQHX group， the alcohol-extracted TQHX group showed increased protein expression of GFAP and GLT-1（<italic>P<</italic>0.05，<italic>P<</italic>0.01）. Conclusion:TQHX prepared by three methods can improve neurological deficits in CIRI rats. The effect is presumedly achieved by promoting the further activation of astrocytes， increasing the expression of GLT-1 and GS， promoting the clearance of Glu accumulated in the synaptic cleft by astrocytes through the Glu-glutamine （Gln） circulation， and reducing the excitotoxicity of Glu. The alcohol-extracted TQHX group was superior to the water-decocted and wine-decocted TQHX groups in reducing the content of Glu in ischemic brain tissues， promoting the activation of astrocytes， and enhancing the protein expression of GLT-1 and GS.