Gadd45α affects retinal ganglion cell injury in chronic ocular hypertension rats by regulating p38MAPK pathway

Objective: To investigate the impact and the mechanism of Gadd45 alpha mediating p38MAPK pathway on the retinal ganglion cells (RGCs) injury in chronic ocular hypertension (COH) rats. Methods: COH model in rats were established and intraocular pressure (IOP) was tested. Retrograde labeling was used for counting RGCs and TUNEL staining was performed for RGCs apoptosis. Western Blotting was conducted to examine the expression of Gadd45 alpha and p38MAPK pathway. Besides, RGC-5 cells cultured in vitro were treated with H2O2. Cell viability was detected by CCK-8, ROS level tested by DCFH-DA assay, and cell apoptosis examined by flow cytometry. Results: COH rats had increased expression of Gadd45 alpha and p-p38/p38 protein 1-4 weeks after surgery. Rats in COH group enhanced obviously in IOP, RGC apoptosis rate and the protein expression of Gadd45 alpha, p-p38/p38, Bax/Bcl-2 and cleaved caspase-3, but declined appreciably in RGC counting. However, the above indicators of COH rats were effectively improved by Gadd45 alpha shRNA treatment. Additionally, RGC-5 cells in H2O2 group reduced in cell viability and went up in ROS level and apoptosis rate. The H2O2-induced RGC-5 cells treated with Gadd45 alpha shRNA were improved apparently in those indicators, and cells treated with pcDNA Gadd45 alpha showed an opposite trend. Moreover, p38 MAPK inhibitor SB203580 can effectively reverse the damage of pcDNA Gadd45 alpha from H2O2-induced RGC-5 cells. Conclusion: Silencing Gadd45 alpha can reduce the RGC damage in COH rats by inhibiting p38MAPK pathway and such a protective role may be associated with the suppression of RGC apoptosis and the mitigation of oxidative stress.