Effect of AMPA-GluR2 on apoptosis of oligodendrocyte precursor cells in acute stage of spinal cord injury in rats

English Keywords:Spinal cord injury  AMPA receptor  Glutamate receptor subunit 2  NBQX  JSTx  Oligodendrocyte precursor cells  Apoptosis

English Abstract:

  【Abstract】 Objectives: To investigate the effect of AMPA-glutamate receptor subunit-2(AMPA-GluR2) on the apoptosis of oligodendrocyte precursor cells(OPCs) in the acute phase of spinal cord injury in rats. Methods: 60 female SD rats were randomly divided into sham operation group(Sham group, n=15), spinal cord injury group(SCI group, n=15), AMPA receptor antagonist NBQX group(n=15) and Ca2+ permeability AMPA receptor antagonist JSTx group(n=15). Allen′s method was used in SCI group, NBQX group and JSTx group to establish a rat spinal cord(T9) injury model using. BBB score was used to evaluate the recovery of motor function after spinal cord injury in rats. The pathological changes after spinal cord injury were observed by HE staining. The expression of AMPA-GluR2 in spinal cord tissue of each group was detected by immunohistochemistry and Western blot. The OPCs was labeled with immunofluorescence and its apoptosis in each group was detected by TUNEL method. Results: The BBB score of SCI group was lower than that of Sham group(P<0.05), the BBB scores of NBQX group(3.60±0.65) and JSTx group(3.80±0.76) were higher than that of SCI group(1.50±0.35) on the 3rd day after spinal cord injury(P<0.05) and there was no difference between NBQX group and JSTx group(P>0.05). The results of HE staining showed that there were spinal cord injuries in SCI group and two antagonist groups, the ventral and ventrolateral white matter pathological damage scores of spinal cord tissue showed that the scores of NBQX group(1.60±0.42) and JSTx group(1.50±0.35) were lower than that of SCI group(2.30±0.20)(P<0.05). The results of AMPA-GluR2 immunohistochemistry showed that the number of positive cells in SCI group(6.15±0.52) was significantly lower than that in Sham group(13.25±0.21) 3 days after spinal cord injury(P<0.05), the number of positive cells in NBQX group(2.10±0.42) and JSTx group(4.45±0.54) was lower than that in SCI group(P<0.05) and the number of positive cells in NBQX group was the least, the number of positive cells in JSTx group was higher than that in the NBQX group(P<0.05). Western blot results showed that the expression of AMPA-GluR2 in SCI group and two antagonist groups was lower than that in Sham group(0.94±0.07) 3 days after spinal cord injury(P<0.05), the expression level of AMPA-GluR2 in NBQX group(0.37±0.07) was lower than that in JSTx group(0.54±0.12)(P<0.05), and the expression level of AMPA-GluR2 was the lowest in the NBQX group. Immunofluorescence showed that positive-labeled OPCs were presented in the spinal cord of rats in each group 3 days after spinal cord injury, the apoptosis index of OPCs in NBQX group and JSTx group was lower than that in SCI group(0.42±0.02) by TUNEL method(P<0.05), and the apoptotic index of JSTx group(0.17±0.01) was lower than that of NBQX group(0.21±0.02)(P<0.05). Conclusions: The apoptosis of OPCs in the acute stage of spinal cord injury in rats is related to the decrease of AMPA-GluR2 expression in spinal cord.