Objectives Diabetes-induced impairment of collateral formation in ischaemic myocardium has been demonstrated both in experimental and clinical studies, which may contribute to unfavorableprognosis among diabetic individuals. However, the underlying mechanism remains to be defined. Endothelial cell (EC) is thought to be one of the important elements in the development and maturation of coronary collaterals. Since ERK5 is a novel regulator of angiogenesis and closely related with VEGF, in present study we aim to determine whether ERK5 exerts a causative effect on advanced glycation end products (AGEs)-induced impairment of angiogenic capacity in cardiac ECs under hypoxia condition, and to identify the down streamtarget molecule.
Methods Cardiac ECs were isolated from left ventricle of Sprague-Dawley rats with a enzyme digestion procedure described in our previous publications. Cells were treated with or without AGEs and then exposed to hypoxia or normoxia. Proliferation, migration and tube-forming of endothelial cells were detected by MTT, Transwell and Matrigel assay respectively. Protein of interest were further validated using ELISA and Western-blot techniques.
Results Hypoxia promoted proliferation, migration and tube-forming capacity in cardiac ECs, which was inhibited significantly by combined administration of AGEs. Incubation with AGEs induced decrease of VEGF secretion and increase of ERK5 phosphorylation after hypoxia stimulation. XMD8-92, a inhibitor of ERK5 phosphorylation, treatment caused elevation of VEGF secretion, and counteracted AGEs-induced impairment of angiogenic capacity in cardiac ECs under hypoxia condition, which has a similar effect with supplementation of exogenous VEGF.
Conclusions Our study demonstrated for the first time that hypoxia-induced enhancement of angiogenic capacity in cardiac ECs was inhibited in the presence of AGEs, which was related with downregulation of VEGF expression caused by ERK5 phosphorylation. Thus ERK5 may function as an important regulator in diabetes-induced impairment of angiogenesis and thereby exacerbated myocardial ischaemic injury through coordinately targeting VEGF in cardiac ECs. Intervention of ERK5 pathway mayrepresent an avenue for therapeutic exploitation to improve prognosis in diabetic individuals with coronary artery disease.