Objective: To explore the protective role of Vitamin D Receptor (VDR) in retinal ganglion cells (RGCs) after high-level glucose induction, and to investigate its underlying mechanism.
Materials and methods: Primary RGCs were isolated from 24-hour-old Sprague Dawley (SD) rats and cultured in 50 mmol/L glucose. The expression of VDR in RGCs induced by 50 mmol/L glucose at different time points was determined by Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot, respectively. Subsequently, VDR siRNA was transfected into RGCs. Transfection efficiency was determined by qRT-PCR and Western blot, respectively. The protein expressions levels of VDR, signal transducer and activator of transcription 3 (STAT3) and p-STAT3 in RGCs after VDR knockdown were determined by Western blot. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) and cell counting kit-8 (CCK-8) assay were conducted to access the viability of RGCs after high-level glucose induction. Ki-67 staining was performed to detect the proliferation of RGCs. Meanwhile, the apoptosis of RGCs was evaluated by using Annexin-V FITC/PI and TUNEL (terminal dexynucleotidyl transferase(TdT)-mediated dUTP nick end labeling) assay, respectively. In addition, caspase-3 activity in RGCs was detected by relative commercial kit.
Results: After 4 days of high-level glucose induction, the viability of RGCs was remarkably decreased. VDR was highly expressed in RGCs during high-level glucose culture. The mRNA and protein expression levels of VDR were both significantly downregulated after the transfection of VDR siRNA in RGCs. Meanwhile, VDR knockdown in RGCs significantly increased the viability and proliferative ability of RGCs, whereas significantly decreased apoptotic rate and caspase-3 activity. In addition, the protein level of p-STAT3 in RGCs was remarkably downregulated after VDR knockdown.
Conclusions: Inhibition of VDR exerts a protective role in high-level glucose induced RGCs damage by activating the STAT3 pathway.