Abstract P226: Endothelin-1 Overexpression Exaggerates Diabetes-induced Endothelial Dysfunction by Altering Oxidative Stress

Abstract

Objective: Increased endothelin (ET)-1 expression has been shown to cause endothelial dysfunction and oxidative stress. Plasma ET-1 is increased in patients with diabetes mellitus. Since endothelial dysfunction often precedes vascular complications in diabetes, we sought to determine whether ET-1 contributes to diabetes-induced endothelial dysfunction. We hypothesized that overexpression of ET-1 in the endothelium will exaggerate diabetes-induced endothelial dysfunction. Methods: Diabetes was induced by streptozotocin IP injections (STZ, 55 mg/kg/day) for 5 days in 6-week-old male wild-type (WT) mice and in mice overexpressing human ET-1 restricted to the endothelium (eET-1). Mice were studied 14 weeks later. Endothelial function and vascular remodeling using pressurized myography, reactive oxygen species (ROS) production by dihydroethidium staining and mRNA expression by reverse transcription-quantitative PCR were assessed in mesenteric arteries (MA). Results: MA endothelium-dependent vasodilatory responses to acetylcholine were reduced 24% by diabetes in WT (E max : 61±6 vs 84±3%, P <0.05), and further decreased by 12% in eET-1 (E max : 49±5, P <0.05). Diabetes decreased MA media/lumen in WT (2.4±0.1% vs 3.3±0.2%, P <0.05) and eET-1 (2.9±0.2% vs 4.0±0.2%, P <0.05), whereas ET-1 overexpression increased MA media/lumen to a similar extent in diabetic and non-diabetic WT mice ( P <0.05). Vascular ROS production in MA was increased 2-fold by diabetes in WT (5.0±0.5 vs 2.5±0.3 relative fluorescence units [RFU]/μm 2 , P <0.05) and further augmented 1.7-fold in eET-1 (8.5±1.2 RFU/μm 2 , P <0.05). Diabetes reduced endothelial nitric oxide synthase (eNOS, Nos3) mRNA expression in eET-1 by 50% (0.7±0.1 vs 1.4±0.2, P <0.05) but not in WT. Induction of diabetes caused a 50% increase in superoxide dismutase 1 ( Sod1 , 1.5±0.2 vs 1.0±0.0, P <0.05) and a 30% increase in Sod2 (1.3±0.1 vs 1.0±0.0, P <0.05) mRNA expression in WT but not in eET-1. Conclusions: Increased expression of ET-1 exaggerates diabetes-induced endothelial dysfunction. This may be caused by an increase in vascular oxidative stress, a decrease in eNOS expression and a decrease in antioxidant capacity.