Effects of glycyrrhizin on repairing sciatic nerve injury in mice

Abstract

Objective To investigate the effects of glycyrrhizin on repairing sciatic nerve injury in BALB/c mice. Methods After mouse sciatic nerve injury model was constructed, the mice were randomly divided into 4 groups: control group, low-dose glycyrrhizin group, middle-dose glycyrrhizin group, and high-dose glycyrrhizin group. At 4th and 8th week after sciatic nerve injury, functional outcome measurements were evaluated by the sciatic functional index (SFI). At 1st day, 1st, 2nd, 4th, and 8th week after sciatic nerve injury, spinal cord (L4-L6) at injured side was cut to perform Western blotting and real-time quantitative polymerase chain reaction (Real-time PCR). The protein and mRNA levels of growth associated protein 43 (GAP-43) and p75 neurotrophic receptor (p75NTR) were detected. Results SFI values were gradually restored after the surgery, SFI values in treatment groups were significantly better than in control group. SFI mean values in high-, middle-, low-dose and control groups were respectively 61.300±1.319, 63.180±1.030, 68.680±0.653, 72.108±0.823 (4th week), 41.440±0.373, 46.210±0.747, 50.830±0.866, 61.350±1.123 (8th week). SFI values in high-, middle-, low-dose groups compared with in control group, t values were respectively 16.560, 16.504, 8.485 (4th week), 37.581, 25.088, 16.577 (8th week) after surgery. P values were all 0.000. In the spinal cord (L4-L6) at the same side of the injured sciatic nerve, the protein and mRNA expressions of GAP-43 were significantly increased in the treatment groups. mRNA expressions of GAP-43 in high-, middle-, low-dose groups compared with in control group, t values were respectively 114.858, 110.170, 12.810 (1st week); 122.115, 63.360, 30.745 (2nd week); 28.027, 20.757, 15.967 (4th week); 33.467, 27.828, 12.513 (8th week). P values were all 0.000. The protein and mRNA expressions of p75NTR were significantly decreased in the treatment groups. mRNA expressions of p75NTR in high-, middle-, low-dose groups compared with in control group, t values were respectively 55.937, 33.212, 12.364 (1st week); 41.779, 29.553, 14.953 (2nd week); 37.000, 22.638, 18.198 (4th week); 42.345, 26.800, 20.250 (8th week). P values were all 0.000. Conclusion Glycyrrhizin treatment can promote the regeneration of mouse sciatic nerve injury and recovery of motor function, which may be associated with the increase of GAP-43 expression and the decrease of p75NTR expression in the corresponding nerve tissues. Key words: Glycyrrhizin; Sciatic nerve injury; Neural repair