Circular Ribonucleic Acid circFTO Promotes Angiogenesis and Impairs Blood–Retinal Barrier Via Targeting the miR-128-3p/Thioredoxin Interacting Protein Axis in Diabetic Retinopathy

Abstract

Background: Increasing attention has been attracted by the role of circular RNAs (circRNAs) in ocular diseases. Previous study has revealed that circ_0005941 (also known as circFTO, an alpha-ketoglutarate–dependent dioxygenase) was upregulated in the vitreous humor of diabetic retinopathy (DR), while its underlying mechanism in DR remains unknown.Methods: Retinal vascular endothelial cells (RVECs) treated with high glucose (HG) were used to establish the DR cell model. The in vivo assays were conducted using streptozotocin-induced diabetic mice. The circular structure and stability of circFTO were identified by Sanger sequencing and RNase R treatment. RT-qPCR analysis was used to detect the RNA expression. The levels of the mRNA-encoded protein thioredoxin-interacting protein (TXNIP) or angiogenesis-associated proteins (VEGFA, PDGF, and ANG2) and blood–retinal barrier (BRB)-related proteins (ZO-1, Occludin, and Claudin-5) were measured by Western blot. The viability of RVECs was measured using CCK-8 assays. The angiogenesis of RVECs was assessed using tube formation assays in vitro. Endothelial permeability assays were conducted to examine the function of the BRB. The binding between genes was explored using RNA pulldown and luciferase reporter assays.Results: CircFTO was upregulated in HG-treated RVECs. CircFTO deficiency reversed the HG-induced increase in the viability and angiogenesis of RVECs and alleviated HG-mediated impairment of the BRB. MiR-128-3p bound with circFTO and was downregulated in HG-treated RVECs. TXNIP was a downstream target gene of miR-128-3p. TXNIP was highly expressed in the DR cell model. Rescue assays revealed that circFTO promoted angiogenesis and impaired the blood–retinal barrier by upregulating TXNIP. In the DR mouse model, circFTO silencing inhibited angiogenesis and promoted BRB recovery in vivo.Conclusion: CircFTO promotes angiogenesis and impairs the blood–retinal barrier in vitro and in vivo by binding with miR-128-3p to upregulate TXNIP in DR.

circFTO upregulates transforming growth factor-alpha through sponging miR-148a-3p to regulate high glucose-induced ARPE-19 cells injury

“…Jianjin Guo et al showed that circFTO could act as a ceRNA to regulate miR-128-3p in the progress of DR, especially in BRB damage and angiogenesis [ 13 ]. However, the function of circFTO on the regulation of the growth and apoptosis of retinal epithelial cells is still unknown.…”

“…However, the underlying regulatory mechanism is still unclear. In addition, recent studies reported that circFTO promoted BRB damage and angiogenesis by targeting miR-128-3p/TXNIP axis [ 13 ]. However, it is still unclear regarding the role of miR-128-3p as the only target regulated by circFTO during the occurrence and development of DR. Further, the roles of circFTO in regulating other cellular events during these processes yet remain to be further studied.…”

Diabetic retinopathy: Involved cells, biomarkers, and treatments

“…For example, circHIPK3 increases endothelial proliferation by blocking miR-30a function ( Shan et al, 2017 ). Moreover, circCOL1A2 and circFTO can facilitate angiogenesis during the pathological progression of DR, and their respective pathways are the miR-29b/VEGF axis and the miR-128–3p/thioredoxin-interacting protein axis ( Zou et al, 2020 ; Guo et al, 2021 ). Finally, the roles of miR-29b and miR-128–3p suggest that microRNA is also significant for angiogenesis in DR.…”

Circular RNAs in diabetes and its complications: Current knowledge and future prospects

“…It increased vascular endothelial growth factor-C, FZD4, and WNT2 expression by blocking miR-30a-3p, which led to the endothelial proliferation and vascular dysfunction ( Shan et al, 2017 ). Moreover, studies found that circDNMT3B, circFTO, circ_001209, circCOL1A2, circ-UBAP2, circSLC16A12 and exosomal circFndc3 can also regulate diabetic retinal vascular function ( Zou et al, 2020 ; Guo et al, 2021 ; Jiewei et al, 2021 ; Li et al, 2021 ; Wang et al, 2022a ). All of these are potential targets to control DR. CircDNMT3B downregulation exacerbated visual damage and circDNMT3B overexpression contributed to the alleviation of retinal vascular dysfunction, while circ_001209 upregulation aggravated the retinal injury by sponging miR-15b-5p in diabetic rats ( Zhu et al, 2019 ; Wang and Zhang, 2021 ).…”