Circ_0006667 contributes to high glucose-induced retinal pigment epithelial cell dysfunction by mediating miR-7-5p/TGFA axis in diabetic retinopathy

Background Diabetic retinopathy (DR) is a common complication of diabetes mellitus and it can lead to visual impairment and blindness. The loss of retinal pigment epithelial (RPE) cells is associated with the etiology of DR. Moreover, dysregulated circular RNAs (circRNAs) are implicated in DR progression. Therefore, this project aims to explore the role and potential mechanism of circ_0006667 in DR. Methods RPE cells (ARPE-19) were stimulated with high glucose (33 mM; HG group) for 24 h to establish the DR cell model. Circ_0006667, microRNA-7-5p (miR-7-5p), and transforming growth factor alpha (TGFA) expression was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cell viability, proliferation, and apoptosis were analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-ethynyl-2′-deoxyuridine (EdU), and flow cytometry. CyclinD1, Cleaved-caspase-3, and TGFA protein levels were detected using western blot. Using Circinteractome and starBase analysis, the binding miR-7-5p and circ_0006667 or TGFA was predicted, and then validated using dual-luciferase reporter and RNA Immunoprecipitation (RIP). Results Circ_0006667 expression was up-regulated in DR patients and HG-induced ARPE-19 cells. HG stimulation suppressed ARPE-19 cell proliferation and promoted cell apoptosis and inflammation, which were alleviated via circ_0006667 silence. Circ_0006667 acted as a molecular sponge for miR-7-5p, and circ_0006667 absence-mediated protective effects in HG-induced ARPE-19 cells were largely overturned by the interference of miR-7-5p. miR-7-5p directly targeted TGFA, and miR-7-5p overexpression protected ARPE-19 cells from HG-induced dysfunction largely by down-regulating TGFA. Circ_0006667 can up-regulate the expression of TGFA by sponging miR-7-5p in ARPE-19 cells. Conclusion Circ_0006667 silencing protected ARPE-19 cells from HG-induced dysfunction by mediating miR-7-5p/TGFA axis.