Salusin-β Mediates High Glucose-Induced Inflammation and Apoptosis in Retinal Capillary Endothelial Cells via a...

Diabetic retinopathy (DR) is characterized by retinal vascular endothelial cell death and vascular inflammation, which are microvascular complications of diabetes mellitus (DM). Salusin-β, a newly identified peptide, is closely associated with hypertension, atherosclerosis and diabetic cardiomyopathy. However, the exact role of salusin-β in high glucose (HG)-induced retinal capillary endothelial cell (REC) inflammation and apoptosis remains unclear.

A total of 60 patients with type 2 diabetes and 20 healthy controls were included in this study. Based on fundus fluorescein angiography findings, the diabetic patients were divided into three subgroups: diabetes without retinopathy (DWR), non-proliferative DR (NPDR) and proliferative DR (PDR). Serum salusin-β levels were measured by enzyme-linked immunosorbent assay. Human RECs (HRECs) were cultured in normal glucose (NG) and HG medium with or without salusin-β. Salusin-β expression was analysed by Western blotting and immunofluorescence staining. Expression of the pro-inflammatory cytokines MCP-1, IL-1β, TNF-α, and VCAM-1 was analysed by Western blotting. Reactive oxygen species (ROS) production was measured with 2',7'-dichlorofluorescein diacetate (DCFH-DA). Cell apoptosis rates were determined by flow cytometry. The levels of p38, JNK, p-p38, and p-JNK and the apoptosis-related proteins cleaved caspase-3, Bax, and cl2 were analysed by Western blotting.

Serum salusin-β levels were higher in diabetic patients than in healthy controls (p = 0.0027), especially in patients with NPDR and PDR (both p<0.01). HG upregulated salusin-β expression in HRECs in a time-dependent manner. Salusin-β exacerbated inflammation and apoptosis, upregulated intracellular ROS production in HG-induced HRECs, and activated ROS-dependent JNK and p38 MAPK signalling, while knockdown of salusin-β suppressed these effects.

Our findings indicate that salusin-β can promote inflammation and apoptosis via ROS-dependent JNK and p38 MAPK signalling in HG-induced HRECs and could be a therapeutic target for DR.