Role of EDHF in type 2 diabetes-induced endothelial dysfunction

Am J Physiol Heart Circ Physiol. 2008 Nov;295(5):H1982-8. doi: 10.1152/ajpheart.01261.2007. Epub 2008 Sep 12.

Abstract

Endothelium-derived hyperpolarizing factor (EDHF) plays a crucial role in modulating vasomotor tone, especially in microvessels when nitric oxide-dependent control is compromised such as in diabetes. Epoxyeicosatrienoic acids (EETs), potassium ions (K+), and hydrogen peroxide (H2O2) are proposed as EDHFs. However, the identity (or identities) of EDHF-dependent endothelial dilators has not been clearly elucidated in diabetes. We assessed the mechanisms of EDHF-induced vasodilation in wild-type (WT, normal), db/db (advanced type 2 diabetic) mice, and db/db mice null for TNF (dbTNF-/dbTNF-). In db/db mice, EDHF-induced vasodilation [ACh-induced vasodilation in the presence of N(G)-nitro-L-arginine methyl ester (L-NAME, 10 micromol/l) and prostaglandin synthase inhibitor indomethacin (Indo, 10 mumol/l)] was diminished after the administration of catalase (an enzyme that selectively dismutates H2O2 to water and oxygen, 1,000 U/ml); administration of the combination of charybdotoxin (a nonselective blocker of intermediate-conductance Ca2+-activated K+ channels, 10 micromol/l) and apamin (a selective blocker of small-conductance Ca2+-activated K+ channels, 50 micromol/l) also attenuated EDHF-induced vasodilation, but the inhibition of EETs synthesis [14,15-epoxyeicosa-5(Z)-enoic acid; 10 mumol/l] did not alter EDHF-induced vasodilation. In WT controls, EDHF-dependent vasodilation was significantly diminished after an inhibition of K+ channel, EETs synthesis, or H2O2 production. Our molecular results indicate that mRNA and protein expression of interleukin-6 (IL-6) were greater in db/db versus WT and dbTNF-/dbTNF- mice, but neutralizing antibody to IL-6 (anti-IL-6; 0.28 mg.ml(-1).kg(-1) ip for 3 days) attenuated IL-6 expression in db/db mice. The incubation of the microvessels with IL-6 (5 ng/ml) induced endothelial dysfunction in the presence of l-NAME and Indo in WT mice, but anti-IL-6 restored ACh-induced vasodilation in the presence of L-NAME and Indo in db/db mice. In db(TNF-)/db(TNF-) mice, EDHF-induced vasodilation was greater and comparable with controls, but IL-6 decreased EDHF-mediated vasodilation. Our results indicate that EDHF compensates for diminished NO-dependent dilation in IL-6-induced endothelial dysfunction by the activation of H2O2 or a K+ channel in type 2 diabetes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arterioles / metabolism
  • Arterioles / physiopathology
  • Biological Factors / metabolism*
  • Blood Glucose / metabolism
  • Body Weight
  • Coronary Vessels / metabolism
  • Coronary Vessels / physiopathology
  • Cyclooxygenase Inhibitors / pharmacology
  • Diabetes Mellitus, Type 2 / metabolism*
  • Diabetes Mellitus, Type 2 / physiopathology
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / metabolism*
  • Endothelium, Vascular / physiopathology
  • Female
  • Hydrogen Peroxide / metabolism
  • Interleukin-6 / genetics
  • Interleukin-6 / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase / antagonists & inhibitors
  • Nitric Oxide Synthase / metabolism
  • Potassium Channel Blockers / pharmacology
  • Potassium Channels / metabolism
  • RNA, Messenger / metabolism
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism
  • Vasodilation* / drug effects
  • Vasodilator Agents / pharmacology

Substances

  • Biological Factors
  • Blood Glucose
  • Cyclooxygenase Inhibitors
  • Interleukin-6
  • Potassium Channel Blockers
  • Potassium Channels
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • Vasodilator Agents
  • endothelium-dependent hyperpolarization factor
  • Nitric Oxide
  • Hydrogen Peroxide
  • Nitric Oxide Synthase