Mechanism Of AKBA-induced ERK Signaling Pathway And Schwann Cell Repair Peripheral Nerve Injury

The incidence of peripheral nerve injury in veterinary clinics is not high,but in recent years,the disease has shown an upward trend in small animals.In this experiment,3-Acetyl-11-keto-?-boswellic Acid(AKBA)was used for the treatment of injured sciatic nerve in rats.Therapeutic effects and mechanisms provide a new theoretical basis for the treatment of clinical peripheral nerve injury in small animals.In vivo experiments: A total of 120 male SD rats weighing 150-200 g were selected and surgically treated with a vascular forceps to mechanically compress the injury to produce a sciatic nerve injury model.The rats were randomLy divided into model control group,AKBA low dose group(1.5 mg/kg),AKBA middle dose group(3 mg/kg)and AKBA high dose group(6 mg/kg).The intraperitoneal injection began on the first postoperative day and was administered on alternate days for a total of 30 days.At 10 days,20 days and 30 days after operation,the neurological function index(SFI),triceps wet weight index(TSCI)and the expression of ERK and p-ERK protein in the injured sciatic nerve tissue were measured.At the 30 th day after operation,the injured sciatic nerve segments of the affected side of the rat were harvested,and the recovery of the peripheral nerve injury was observed by HE staining.The number of myelin in the rats were determined by Luxol Fast Blue staining;immunohistochemical staining to determine the expression level of NF200 and S100,Used to determine neurons and Schwann cells(Schwann cells)of the proliferation of regeneration.In vitro: Using AKBA to intervene in Schwann cell culture,determine the non-toxic dose range of AKBA,and use the non-toxic dose range to screen the optimal concentration of AKBA for Schwann cell proliferation.The optimal concentration of AKBA was used to incubate Schwann cells and the protein expression levels of ERK,p-ERK,JNK and p-JNK in Schwann cells were determined at 0h,6h,12 h and 24 h.After treatment of Schwann cells with inhibitor PD98059,the expression levels of ERK and p-ERK proteins in Schwann cells were determined.After knock-down of ERK by siRNA,the expression of P0 and P75 proteins in Schwann cells was determined.Results:(1)After 30 days,the recovery of motor nerve function in rats was optimistic.At 20 days and 30 days,the SFI index of the middle and high dose AKBA groups was significantly higher than that of the model control group(p < 0.05 or p < 0.01).The TSCI index of the high dose AKBA group was significantly higher than the sham operation group(p < 0.05).During the experimental period,the SFI and TSCI index of the high-dose AKBA group was the highest value at the 30 th day,and the rats had the best exercise recovery.(2)At 30 d,the nerve fibers in the model control group were sparse,swollen and dissolved,myelin sheath disintegrated,and inflammatory cell infiltration was involved.In the AKBA low-dose group,the nerve fiber was bent,and there was a clear demyelination phenomenon around the blood vessels.There was inflammatory cell infiltration;nerve fibers in the AKBA middle dose group were swollen and demyelination was lighter;nerve fibers in the AKBA high dose group were slightly swollen and were almost normal.(3)30 days after operation,the expression levels of NF200 and S100 protein were increased,and the change trend was the same.With the increase of AKBA dose,the content of NF200 and S100 protein increased significantly(p < 0.05 or p < 0.01).(4)The number of myelin in the low,middle and high doses of AKBA was significantly higher than that in the model control group.The number of myelin in the high dose group was the highest(p<0.05 or p < 0.01);while in the model control group,the myelin sheath was largely dissolved and formed a large amount The lipid vacuoles and myelin sheaths were of different shapes.The AKBA low,middle,and high dose groups improved in varying degrees.The shape of the myelin sheath in the high dose group was relatively regular,and the others were normal.(5)After 30 days of different doses of AKBA,the phosphorylation level of ERK signal pathway increased with the increase of AKBA dose,and the expression level of p-ERK protein in high dose group was significantly higher than that of model control group at 30 days(p < 0.01).(6)Schwann cells cultured in vitro with AKBA concentration were used to detect the increase of p-ERK protein level with the increase of time.After 24 hours,the level of p-ERK protein was the highest(p < 0.05),while the protein level of p-JNK was increased.The rising trend is not obvious.After treatment with PD98059,even though AKBA incubated Schwann cells,the degree of phosphorylation of ERK protein was not significant;after siRNA intervention;P0,P75 protein in AKBA group was significantly higher than the control group(p < 0.01),while the levels of P0 and P75 proteins in the siRNA+AKBA group were lower than those in the control group(p < 0.05 or p < 0.01).Conclusion:AKBA can significantly promote the recovery of injured sciatic nerve motor function,nerve fiber repair,nerve myelin regeneration and axon regeneration;and promote the proliferation of Schwann cells in rat sciatic nerve.AKBA can increase the expression of P0 and P75 proteins and regulate the degree of myelination of Schwann cells.AKBA can increase the phosphorylation of ERK signal pathway,promote the expression of p-ERK protein,regulate the proliferation of Schwann cells and myelination,so as to achieve the repair of sciatic nerve injury in rats.