MiR-155-5p promotes endothelial-mesenchymal transition and oxidative stress in diabetic retinopathy

MicroRNA (miRNA) has been confirmed to be related to gene expression regulation and disease progression. However, the role of miR-155-5p in diabetic retinopathy remains unclear.

The retinal microvascular endothelial cells (RMECs) were treated with high glucose, and then the changes of miR-155-5p, endothelial cell markers (CD31 and VE-cadherin), mesenchymal cell markers (SM22α and α-SMA), and VEGF were detected by RT-qPCR. The apoptotic markers (Bax, Bcl-2, cleaved caspase-3) were detected by Western blotting. Additionally, miRNA inhibitors or small interfering RNA were used to regulate the levels of miR-155-5p and DDAH1. Subsequently, the changes in endothelial-mesenchymal transition markers, oxidative stress markers, and apoptotic proteins were observed. The regulatory relationship between miR-155-5p and DDAH1 was investigated using dual-luciferase reporter assays, RNA immunoprecipitation, and RNA pull-down assays.

After culturing RMECs with high glucose, the level of miR-155-5p increased. After the miR-155-5p level was reduced, the levels of CD31 and VE-cadherin increased, while the levels of SM22α, α-SMA and VEGF decreased. Additionally, the downregulation of miR-155-5p significantly inhibited the increase in ROS and Malondialdehyde (MDA) levels as well as cell apoptosis. DDAH1 is the downstream target of miR-155-5p. The downregulation of DDAH1 significantly weakened the inhibitory effects of miR-155-5p downregulation on endothelial-mesenchymal transition, oxidative stress, and cell apoptosis.

In diabetic retinopathy, miR-155-5p affects the endothelial-mesenchymal transition process and oxidative stress levels of RMECs through DDAH1 and reduces cell apoptosis induced by high glucose.