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Objective
To explore the protective effect of vitexin on retinal ganglion stem cells (RGCs) from oxidative stress caused by retinal ischemia-reperfusion (RIR) in rats and its possible mechanism.
Methods
Sixty male SD rats were randomly divided into the model group, vitexin group and normal control group by random number table, with 20 rats in each group.The right eyes were taken as experimental eyes.Rats in the model group and the vitexin group were treated with anterior chamber perfusion to establish RIR models.Rats in the vitexin group were given intraperitoneal injection of vitexin at a dose of 25 mg/(kg·d) for 7 days.Rats in the model group were intraperitoneally injected with the same volume of normal saline.For the normal control group, the experimental eyes underwent anterior chamber puncture without increasing the intraocular pressure, and were intraperitoneally injected with the same volume of normal saline.On the 7th day following modeling, the rats were sacrificed by overdose anesthesia.Histopathology staining was used to detect the thickness of retina and the number of RGCs.Retrograde tracing with Fluoro-Gold was used to detect the density of RGCs.TUNEL staining was used to detect the apoptosis of RGCs.Colorimetric method was used to detected superoxidate dismutase (SOD) activity and concentration of malondialdehyde (MDA) and nitric oxide (NO). Western blot method was used to detect the relative expression levels of cytoplasmic Nrf2, HO-1, NQO1, nuclear Nrf2 proteins in rat retina.The use and care of animals followed the ARVO Statement.This study protocol was approved by the Experimental Animal Ethics Committee of Henan Eye Hospital (No.HNEECA-2019-04).
Results
The retinal thickness was (90.21±3.55)μm in the model group, which was significantly lower than (128.20±5.31)μm in the normal control group and (119.65±6.14)μm in the vitexin group, and the differences were statistically significant (both at P<0.05). The average density of RGCs was (1 300.85±14.00)/mm2 in the model group, which was significantly lower than(2 330.12±15.05)/mm2 in the normal control group and (1 921.64±11.78)/mm2 in the vitexin group, and the differences were statistically significant (both at P<0.05). The rate of TUNEL positive RGCs was (68.34±5.04)% in the model group, which was significantly higher than (3.01±0.18)% in the normal control group and (35.51±2.04)% in the vitexin group, and the differences were statistically significant (both at P<0.05). Compared with the normal control group and the vitexin group, the SOD activity in the retinal tissue of the rats was lower and the concentrations of MDA and NO were higher in the model group, and the differences were statistically significant (all at P<0.05). The expression level of cytoplasmic Nrf2 protein was the lowest in the vitexin group, then following the model group and the normal control group, and the relative expression levels of HO-1, NQO1 and nuclear Nrf2 protein were the highest in the vitexin group, then followed the model group and normal control group, and the differences were statistically significant (all at P<0.05).
Conclusions
Vitexin can reduce the apoptosis of RGCs and alleviate oxidative stress damage of retina in RIR rat model.This protective effect may be achieved by activating Nrf2-related signaling pathway.