Spinal cord injury(SCI)is one kind of severe trauma for central nervous system.Myelin debris clearance and axon regeneration are essential for nerve regeneration after SCI.Metformin,a glucose-lowering drug,has been demonstrated to promote the locomotor functional recovery after SCI.In this study,we investigated the role and molecular mechanism of metformin on myelin preservation in a rat SCI model.SCI was induced in rats by compression at T9 level using a vascular clip.We showed that administration of metformin(50mg·kg-1·d-1,ip)for 28 days significantly improved locomotor function in SCI rats.Metformin also ameliorated SCI-induced neuronal apoptosis and promoted axon regeneration in the spinal cord.Using co-immunofluorescence of IBa-1 and MBP,and luxol fasting blue(LFB)staining,we demonstrated that metformin promoted the transformation of M1 to M2 phenotype polarization of microglial cells,then greatly facilitated myelin debris clearance and protected the myelin in SCI rats.Furthermore,metformin ameliorated SCI-induced blockade of autophagic flux in the spinal cord,and enhanced the fusion of autophagosome and lysosome by inhibiting the AMPK-mTOR signaling pathway.Moreover,metformin significantly attenuated inflammatory responses in the spinal cord.In LPS-treated BV2 cells,pretreatment with metformin(2 mM)significantly enhanced autophagy level,suppressed inflammation and cell apoptosis.The protective effects were blocked in the presence of an autophagy inhibitor 3-methyladenine(3-MA,5 mM),suggesting that the effect of metformin on autophagy in microglial cells is essential for the myelin preservation during nerve recovery.This study reveals a novel therapeutic effect of metformin in SCI recovery by regulating the activation of microglial cells and enhancing its autophagy level.

Yan-qing Wu;Jun Xiong;Zi-li He;Yuan Yuan;Bei-ni Wang;Jing-yu Xu;Man Wu;Su-su Zhang;Shu-fang Cai;Jia-xin Zhao;Ke Xu;Hong-yu Zhang;Jian Xiao

The Institute of Life Sciences,Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors,Biomedical Collaborative Innovation Center of Wenzhou,Wenzhou University,Wenzhou 325035,China;Molecular Pharmacology Research Center,School of Pharmaceutical Science Wenzhou Medical University,Wenzhou 325035,China;Department of Pharmacy,Hangzhou Red Cross Hospital,Zhejiang Province Hospital of Integrated Traditional Chinese and Western Medicine,Hangzhou 310003,China

中国药理学报（英文版）

[1]Yan-qing Wu;Jun Xiong;Zi-li He;Yuan Yuan;Bei-ni Wang;Jing-yu Xu;Man Wu;Su-su Zhang;Shu-fang Cai;Jia-xin Zhao;Ke Xu;Hong-yu Zhang;Jian Xiao-.Metformin promotes microglial cells to facilitate myelin debris clearance and accelerate nerve repairment after spinal cord injury)[J].中国药理学报（英文版）,2022(06):1360-1371

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