ABSTRACT
Objective:To observe the effect of astragaloside Ⅳ on lysophosphatidic acid(LPA)- induced neurite retraction of N1E-115 cells and its potential mechanism.Methods:N1E-115 cells were divided into blank group, model group, the low, medium and high dose groups of astragaloside Ⅳ. The blank group and model group was not intervened by astragaloside; while the low, medium and high dose groups were treated with 20,40 and 80 μg/ml astragaloside Ⅳ for 24 h. Each group was cultured with serum-free medium for 12 h. The model group and astragaloside Ⅳ groups were intervened by 40 μmol/L LPA for 10 min. Each group was observed and photographed with the inverted microscope, and the number of neurites in N1E-115 cells was counted by Image J software. The fluorescence expression of recombinant ras homolog gene family member A (RhoA), rho associated coiledcoil protein kinase 2 (ROCK2), phospho-rho associated coiledcoil protein kinase 2 (p-ROCK2) and phospho-myosin light chain 2 (p-MLC2) proteins was detected by immunohistochemistry. Real-time fluorescent quantitative polymerase chain reaction was used to detect the mRNA expression levels of RhoA and ROCK2 ; the protein expression levels of RhoA, ROCK2, p-MLC2 and myosin light chain 2 (MLC2) were detected by Western blotting.Results:Compared with 20 μg/ml astragaloside Ⅳ group, the inhibition rate of neurite retraction in 40 and 80 μg/ml astragalosideⅣ groups increased ( P<0.05). Compared with model group, the average fluorescence intensity of RhoA, p-ROCK2, p-MLC2 in 20, 40, 80 μg/ml astragaloside Ⅳ groups and the ROCK2 average fluorescence intensity in 40 μg/ml astragaloside Ⅳ group were decreased ( P<0.05, P<0.01); the expression of RhoA mRNA (0.89±0.09, 0.41±0.01, 0.09±0.03 vs. 1.50±0.01) and ROCK2 mRNA (0.89±0.09, 0.14±0.01, 0.20±0.01 vs. 1.62±0.17) decreased in 20, 40, 80 μg/ml astragaloside Ⅳ groups ( P<0.05, P<0.01); the ROCK2 protein (0.75±0.06, 0.57±0.02, 0.66±0.01 vs. 1.08±0.02), p-MLC2 protein (1.72±0.03, 1.40±0.04, 1.29±0.03 vs. 2.19±0.11), MLC2 protein (1.13±0.02, 0.68±0.03, 0.75±0.03 vs. 1.60±0.03) in 20, 40, 80 μg/ml astragaloside Ⅳ groups and the RhoA protein (0.35±0.01, 0.40±0.03 vs. 0.57±0.08) in 20, 40 μg/ml astragaloside Ⅳ groups were decreased ( P<0.05, P<0.01). Conclusion:Astragaloside Ⅳ can prevent LPA-induced neurite retraction and promote damaged nerve regeneration. The mechanism may down-regulae the protein expression levels of RhoA, ROCK2, p-ROCK2, p-MLC2 and MLC2 in RhoA-ROCK2 signaling pathway, and inhibite nerve growth cone collapse.