CircFAT1 regulates retinal pigment epithelial cell pyroptosis and autophagy via mediating m6A reader protein YTHDF2 expression in diabetic retinopathy

Diabetic retinopathy (DR) is a serious blinding complication of diabetes. At present, the therapeutic intervention effect is limited. We aimed to investigate the circRNA expression profiles in retinal proliferative fibrovascular membranes of patients with DR and explore the effect of circFAT1 on pyroptosis and autophagy of high glucose (HG)-induced retinal pigment epithelial (RPE) cells and its molecualr mechanism. In this study, circRNA sequencing was performed to determine the expression profiles of circRNAs in DR patients. The expression of circFAT1 was measured by qRT-PCR. Cell counting kit-8, transmission electron microscope, western blot, immunofluorescence and enzyme-linked immunosorbent assay were conducted to explore the roles of HG and circFAT1 in RPE cell pyroptosis and autophagy. RNA pull down was used to determine the binding protein of circFAT1. Our data showed that HG significantly reduced the viability of RPE cells, inhibited cell autophagy and contributed to cell pyroptosis. In addition, a total of 189 differentially expressed circRNAs (DEcircRNAs) were identified between DR patients and non-DR patients, including 93 upregulated and 96 downregulated DEcircRNAs in the retinal proliferative fibrovascular membranes of DR patients. Pathway analysis showed that DEcircRNAs were mainly involved in MAPK signaling pathway, TGF-beta signaling pathway and adherens junction. Moreover, circFAT1 was significantly downregulated in retinal proliferative fibrovascular membranes of DR patients and HG-induced RPE cells. CircFAT1 overexpression remarkably enhanced the expression of LC3B, while reduced the expression of GSDMD in HG-induced RPE cells. RNA pull down combined with western blot analysis indicated that circFAT1 bound to m6A reader YTHDF2. YTHDF2 overexpression significantly increased the protein expression of LC3B in HG-induced RPE cells. In summary, circFAT1 promoted autophagy and inhibited pyroptosis of RPE cells induced by HG, and could combine with YTHDF2. This study provides new ideas for DR prevention and treatment.