H2O2 Is the Transferrable Factor Mediating Flow-Induced Dilation in Human Coronary Arterioles

• Published in: Circulation research 2011-03, Vol.108 (5), p.566-573
• Main Authors: Liu, Yanping, Bubolz, Aaron H, Mendoza, Suelhem, Zhang, David X, Gutterman, David D
• Format: Article
• Language: English
• Subjects: Arterioles - drug effects; Arterioles - physiology; Biological and medical sciences; Biological Factors - metabolism; Catalase - metabolism; Coronary Vessels - drug effects; Coronary Vessels - physiology; Endothelium, Vascular - metabolism; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen Peroxide - metabolism; Hydrogen Peroxide - pharmacology; Indoles - pharmacology; Large-Conductance Calcium-Activated Potassium Channels - metabolism; Muscle, Smooth, Vascular - metabolism; Patch-Clamp Techniques; Polyethylene Glycols - metabolism; Potassium Channel Blockers - pharmacology; Regional Blood Flow - physiology; Vasodilation - drug effects; Vasodilation - physiology; Vertebrates: cardiovascular system
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/CIRCRESAHA.110.237636

RATIONALE:Endothelial derived hydrogen peroxide (H2O2) is a necessary component of the pathway regulating flow-mediated dilation (FMD) in human coronary arterioles (HCAs). However, H2O2 has never been shown to be the endothelium-dependent transferrable hyperpolarization factor (EDHF) in response to shear stress. OBJECTIVE:We examined the hypothesis that H2O2 serves as the EDHF in HCAs to shear stress. METHODS AND RESULTS:Two HCAs were cannulated in series (a donor intact vessel upstream and endothelium-denuded detector vessel downstream). Diameter changes to flow were examined in the absence and presence of polyethylene glycol catalase (PEG-CAT). The open state probability of large conductance Ca-activated K (BKCa) channels in smooth muscle cells downstream from the perfusate from an endothelium-intact arteriole was examined by patch clamping. In some experiments, a cyanogen bromide–activated resin column bound with CAT was used to remove H2O2 from the donor vessel. When flow proceeds from donor to detector, both vessels dilate (donor:68±7%; detector45±11%). With flow in the opposite direction, only the donor vessel dilates. PEG-CAT contacting only the detector vessel blocked FMD in that vessel (6±4%) but not in donor vessel (61±13%). Paxilline inhibited dilation of endothelium-denuded HCAs to H2O2. Effluent from donor vessels elicited K channel opening in an iberiotoxin- or PEG-CAT–sensitive fashion in cell-attached patches but had little effect on channel opening on inside-out patches. Vasodilation of detector vessels was diminished when exposed to effluent from CAT-column. CONCLUSIONS:Flow induced endothelial production of H2O2, which acts as the transferrable EDHF activating BKCa channels on the smooth muscle cells.