Abstract:

Objective To discuss the protective effect of salidroside （SAL） on rat retinal ganglion （RG） cells，and to clarify its possible mechanism. Methods A total of 30 SPF-grade male SD rats were randomly divided into control group， diabetes group and SAL group. Except for control group， the remaining rats were intraperitoneally injected with streptozotocin （STZ） to establish diabetes models. Optical coherence tomography （OCT） was used to detect retinal thickness of rats in various groups； HE staining was used to observe the morphological manifestations of retina in rats in various groups. The high glucose-induced RG cell injury model was established with 300 mmol·L^-1 glucose. Cell counting kit-8 （CCK-8） method was used to evaluate the activity and quantity of RG cells； flow cytometry was used to detect reactive oxygen species （ROS） level in RG cells. Bioinformatics analysis was performed to screen the core targets that may interact with SAL. Real-time fluorescence quantitative PCR（RT-qPCR） method was used to detect the mRNA expression levels of core targets in RG cells. Protein docking was used to predict the core target with the highest correlation with SAL in protecting high glucose-induced RG cell injury； Western blotting method was used to detect the expression levels of glutathione peroxidase 4 （Gpx4） and nuclear factor （erythroid-derived 2）-like 2 （Nfe2l2） proteins in the cells in various groups， so as to verify the mechanism of key proteins on RG cells. Results The OCT results showed that compared with control group， the retinal thickness of the rats in diabetes group was significantly thinned （P<0.05）， which confirmed the successful establishment of diabetic retinopathy model； compared with diabetes group， the retinal thickness of the rats in SAL group was increased （P<0.05）. The HE staining results showed that the boundaries of each retinal layer in diabetes group were unclear， a large number of vacuoles appeared， and RG cells were massively lost； retinal ganglion cells in SAL group were arranged neatly with normal nuclear morphology. The CCK-8 and microscopic observation results showed that compared with control group， the cell activity and cell quantity in high glucose group were decreased （P<0.05）； compared with high glucose group， the cell viability and cell quantity in SAL group were increased （P<0.05）. The flow cytometry results showed that compared with control group， the ROS level in RG cells of high glucose group was significantly increased； compared with high glucose group， the ROS level in cells of SAL group was significantly decreased. A total of 10 Hub genes highly associated with SAL were screened out by bioinformatics analysis， namely mammalian target of rapamycin （MTOR）， cysteine-aspartic protease 3 （CASP3）， hypoxia-inducible factor 1A （HIF1A）， sirtuin 1 （SIRT1）， toll-like receptor 4 （TLR4）， heat shock protein family A member 5 （HSPA5）， nuclear factor （erythroid-derived 2）-like 2 （NFE2L2）， nitric oxide synthase 3 （NOS3）， cysteine-aspartic protease 8 （CASP8） and nucleotide-binding oligomerization domain-like receptor protein 3 （NLRP3）. The mRNA expression of the above genes was verified by RT-qPCR method. The protein docking results indicated that NFE2L2 was the core target with the highest correlation with SAL in protecting high glucose-induced RG cell injury. The Western blotting results showed that compared with control group， the expression level of Nfe2l2 protein in the cells （P<0.05） in high glucose group was increased and the expression level of Gpx4 protein was decreased （P<0.05）； compared with high glucose group， the expression level of Nfe2l2 protein in the cells in Nfe2l2 silencing group and SAL group was decreased （P<0.05） and the expression level of Gpx4 protein was increased （P<0.05）. Conclusion SAL treatment increases retinal thickness， alleviates retina tissue damage， enhances RG cell viability and reduces intracellular ROS levels in diabetic rats， and exerts a protective effect on the retina of diabetic rats. Its mechanism may be related to the down-regulation of Nfe2l2 expression by SAL.

Key words: Salidroside, Diabetes, Retinal ganglion cell, Bioinformatics, Oxidative stress