Promotion mechanism of astragaloside on axon repair and regeneration in experimental autoimmune encephalomyelitis mice
Objective To investigate the effects of astragaloside Ⅳ(AS-Ⅳ)on axon growth inhibitory factor A(Nogo-A)and its downstream pathway protein RHO-associated coiled spiral kinase 2(ROCK2)in experimental autoimmune encephalomyelitis(EAE)mice,and to explore the mechanism by which it promotes axon repair and regeneration.Methods EAE model was induced in C57BL/6 female mice by subcutaneous injection of myelin oligodendrocyte glycoprotein 35-55(MOG35-55).Mice were randomly divided into EAE group and AS-Ⅳ group(n=8 per group).EAE group received intraperitoneal injection of PBS on the 3rd day post-immunization,while AS-Ⅳ group was administered AS-Ⅳ at a dosage of 30mg/(kg.d)once daily,0.2 ml per injection,for 25 consecutive days.On the 28th day post-immunization,the expression levels of growth-associated protein 43(GAP-43),neuronal core antigen(NeuN),microtubule associated protein 2(MAP-2),glial fibroacidic protein(GFAP),and Iba1 in the spinal cord were detected using immunofluorescence assay.Real-time fluorescence quantitative PCR(qRT-PCR)was conducted to detect mRNA expression levels of GAP-43,Nogo-A,and Nogo receptor(NgR)genes.Western blotting was utilized to determine the expression levels of GAP-43,Nogo-A,ROCK2,phosphorylated myosin phosphatase(p-MYPT1),B-lymphoblastoma-2(Bcl-2),and Bcl-2 associated X protein(Bax).Results Compared with EAE group,AS-Ⅳ treatment significantly reduced the positive cell expression rates of Iba1 microglia and GFAP astrocyte in spinal cord(P<0.01 and P<0.001,respectively),while it also increased the positive expression rates of NeuN and MAP-2(P<0.001 and P<0.05,respectively).The treatment also upregulated the expression level of anti-apoptotic factor Bcl-2(P<0.001)and downregulated the expression level of pro-apoptotic factor Bax(P<0.05),leading to an increase in Bcl-2/Bax ratio(P<0.05).Furthermore,AS-Ⅳ enhanced the expression of GAP-43 protein(P<0.05)and decreased the mRNA expression levels of neuroregeneration inhibitor Nogo receptor(NgR)and ROCK2 gene(P<0.001,P<0.05,respectively);as well as decreased the expression levels of Nogo-A,ROCK2 and p-MYPT1 proteins(P<0.05,P<0.001).Conclusion AS-Ⅳ may inhibit the activation of microglia and astrocytes and neuronal apoptosis in EAE mice by inhibiting Nogo-A and downstream pathway ROCK 2,thereby promoting the expression of GAP-43,NeuN and MAP-2,alleviating neuronal damage,and facilitating axon repair and regeneration.
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