Granulocyte Colony-Stimulating Factor-Induced TAF9 Modulates P53-TRIAP1-CASP3 Axis to Prevent Retinal Ganglion Cell Death after Optic Nerve Ischemia

Abstract

BackgroundOptic nerve head (ONH) infarct can result in progressive retinal ganglion cell (RGC) death. Some evidences indicated that the granulocyte colony-stimulating factor (GCSF) provides positive effects against ischemic damage on RGCs. However, protective mechanisms of the GCSF after ONH infarct are complex and remain unclear. MethodsTo investigate the complex mechanisms, the transcriptome profiles of the GCSF-treated retinas were examined using microarray technology. The retinal mRNA samples on days 3 and 7 post rat anterior ischemic optic neuropathy model (rAION) were analyzed by microarray and bioinformatics analyses. To evaluate the TAF9 function in RGC apoptosis, GCSF plus TAF9 siRNA-treated rats were evaluated using retrograde labeling with FluoroGold assay, TUNEL assay, and Western blotting in a rAION.ResultsGCSF treatment influenced 3101 genes and 3332 genes on days 3 and 7 post rAION, respectively. ONH infarct led to changes in 702 and 179 genes on days 3 and 7 post rAION, respectively. After cluster analysis, the TATA box-binding protein (TBP)-associated factor levels were significantly reduced after ONH infarct but significantly increased after GCSF treatment. The network analysis revealed that TBP associated factor 9 (TAF9) can bind to TP53 to induce TP53 regulated inhibitor of apoptosis 1 (TRIAP1) expression. The RGC density in the GCSF plus TAF9 siRNA-treated group was 1.95-fold (central retina) and 1.75-fold (midperipheral retina) lower than that in the GCSF-treated group (p < 0.05). The number of apoptotic RGC in the GCSF plus TAF9 siRNA-treated group is threefold higher than that in the GCSF-treated group (p < 0.05). Treatment with TAF9 siRNA significantly reduced GCSF-induced TP53 and TRIAP1 expression by 2.4-fold and 4.7-fold, respectively, in the rAION model. Overexpression of TAF9 significantly reduced apoptotic RGC and CASP3 levels and induced TP53 and TRIAP1 expression in the rAION model. ConclusionOur in vivo study is the first to report that GCSF is able to induce TAF9 expression to control RGC death and survival after ON infarct. Besides, the binding of TAF9 and TP53 is crucial to inhibit TP53 degradation and to modulate TRIAP1-CASP3 axis. Thus, we considered that TAF9 is a potential drug for patient with NAION.