Netrin-1 restores cell injury and impaired angiogenesis in vascular endothelial cells upon high glucose by PI3K/AKT-eNOS

Abstract

Diabetic foot ulceration (DFU) represents a common vascular complication of diabetes mellitus (DM) with high morbidity and disability resulting from amputation. Netrin-1 level was decreased in type 2 DM patients and has been identified as a protective regulator against diabetes-triggered myocardial infarction and nephropathy. Unfortunately, its role and molecular mechanism in DFU remain poorly elucidated. Here, netrin-1 levels were reduced in DM and DFU patients relative to healthy controls, with netrin-1 levels being the lowest in DFU patients. Moreover, exposure to high glucose (HG) also suppressed netrin-1 expression in human umbilical vein endothelial cells (HUVECs). Elevated netrin-1 expression by infection with Ad-netrin-1 adenovirus vector protected against HUVEC injury in response to HG by ameliorating the inhibitory effects on cell viability, lactate dehydrogenase (LDH) and malondialdehyde (MDA) levels, cell apoptotic rate and caspase-3 activity. Importantly, HG-impaired angiogenesis was improved after netrin-1 overexpression by elevating cell migration, capillary-like tube formation and VEGF production. Mechanism assay substantiated that netrin-1 elevation increased the phosphorylation levels of AKT and eNOS, and NO production, which was notably suppressed by HG, indicating that netrin-1 overexpression restored HG-triggered impairment of the PI3K/AKT-eNOS pathway. More intriguingly, preconditioning with LY294002 (PI3K/AKT antagonist) or N^G-monomethyl-l-arginine (eNOS inhibitor) antagonized netrin-1-induced activation of the PI3K/AKT-eNOS pathway. Concomitantly, treatment with these antagonists also attenuated the protective role of netrin-1 in endothelial dysfunction upon HG stimulation. These results suggest that elevation of netrin-1 may restore HG-triggered impairment of HUVEC and angiogenesis by activating the PI3K/AKT-eNOS pathway, indicating a potential agent for wound healing in DFU patients.

Keywords: PI3K/AKT; diabetic foot ulcer; eNOS; endothelial dysfunction; high glucose; netrin-1.