USP14-Dependent IGF1R Aggravates High Glucose-Induced Diabetic Retinopathy by Upregulating BAP1.

Diabetic retinopathy (DR) is a microvascular complication of diabetes. Insulin-like growth factor 1 receptor (IGF1R) has been implicated in the pathogenesis of DR; however, the underlying mechanism remains unclear. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to assess IGF1R mRNA expression. Western blotting assays were performed to analyze the protein expression of IGF1R, ubiquitin-specific peptidase 14 (USP14), and BRCA1-associated protein 1 (BAP1). Cell viability, apoptosis, interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) levels were analyzed using cell counting kit-8 assay, flow cytometry, and enzyme-linked immunosorbent assays, respectively. Fluorescent microscopy and flow cytometry were performed for reactive oxygen species (ROS) level assessment, and colorimetric assays for iron (Fe) and glutathione (GSH) levels. Co-immunoprecipitation assays and/or colocalization techniques were employed to validate the association of IGF1R with USP14 and BAP1. Treatment with high glucose (HG) increased the protein expression of IGF1R, USP14, and BAP1 in ARPE-19 cells. Silencing of IGF1R mitigated HG-induced apoptosis, inflammatory response, and ferroptosis in ARPE-19 cells. USP14 was found to stabilize IGF1R protein expression through deubiquitination. Overexpression of USP14 exacerbated HG-induced cellular injury, whereas silencing of USP14 protected ARPE-19 cells by reducing IGF1R expression. Interaction between IGF1R and BAP1 was confirmed in ARPE-19 cells and IGF1R silencing protected cells from HG-induced injury by regulating BAP1 expression. Thus, USP14-dependent regulation of IGF1R expression and its interaction with BAP1 play a crucial role in the pathogenesis of high glucose-induced diabetic retinopathy.