Neuroprotective effects of tianmagouteng decoction on retinal ganglion cells in optic nerve crush model

Abstract

Objective To investigate the neuroprotective effect and antioxidation mechanism of tianmagouteng decoction on retinal ganglion cells (RGCs) in optic nerve crush model. Methods Optic nerve crush models were established using optic nerve clamping method in the right eyes of 50 SPF male Wistar rats.The rats were randomized into model group (17 rats), 1.2 g/ml tianmagouteng decoction group (16 rats) and 2.4 g/ml tianmagouteng decoction group (17 rats). Ttianmagouteng decoction at the dose of 1.2 g/(ml·d) or 2.4 g/(ml·d) was intragastrically administered 2 hours after onset of optic nerve damage (10 ml/kg), respectively, based on grouping for consecutive 28 days, and equal volume of distilled water was used in the same way in the model group.Fluoro-gold (FG, 3 μl, 3%) was bilaterally injected into superior colliculus to retrogradely label RGCs 23 days following modeling.The rats were sacrificed at day 28 and retinal flatmounts were prepared to count RGCs.Retinal glutathione peroxidase (GSH-Px) activity in rat retinas was detected by chemical colorimetric analysis. Results The survival rate of RGCs was (59.67±9.85)%, (71.33±9.14)% and (73.63±8.33)% in the model group, 1.2 g/ml tianmagouteng decoction group and 2.4 g/ml tianmagouteng decoction group, respectively, showing a significant difference among the three groups (F=5.322, P=0.014), and the survival rate of RGCs was evidently higher in the 1.2 g/ml tianmagouteng decoction group and 2.4 g/ml tianmagouteng decoction group than that in the model group (P=0.023, 0.006). The GSH-Px activity was (222.20±76.67), (311.30±46.93) and (473.65±117.73)μmol/(s·mg) in the model group, 1.2 g/ml tianmagouteng decoction group and 2.4 g/ml tianmagouteng decoction group, respectively, with a significant difference among the three groups (F=20.005, P<0.001), and the GSH-Px activity in the 2.4 g/ml tianmagouteng decoction group is considerably increased as compared to the model group and 1.2 g/ml tianmagouteng decoction group (P<0.001; P=0.001). Conclusions Tianmagouteng decoction plays a neuroprotective effect on RGCs after optic nerve damage in rat, which may be achieved by improving the activity of the GSH-Px in retina, suggesting that antioxidation probably be one of the neuroprotective mechanisms of tianmagouteng decoction. Key words: Injury, optic nerve; Neuroprotection; Chinese herbal medicine; Retinal ganglion cells; Glutathione peroxidase; Disease models; Rats, Wistar; Tianmagouteng decoction