H2O2 is the transferrable factor mediating flow-induced dilation in human coronary arterioles - PubMed (original) (raw)

H2O2 is the transferrable factor mediating flow-induced dilation in human coronary arterioles

Yanping Liu et al. Circ Res. 2011.

Abstract

Rationale: Endothelial derived hydrogen peroxide (H(2)O(2)) is a necessary component of the pathway regulating flow-mediated dilation (FMD) in human coronary arterioles (HCAs). However, H(2)O(2) has never been shown to be the endothelium-dependent transferrable hyperpolarization factor (EDHF) in response to shear stress.

Objective: We examined the hypothesis that H(2)O(2) 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(2+)-activated K(+) (BK(Ca)) 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 H(2)O(2) from the donor vessel. When flow proceeds from donor to detector, both vessels dilate (donor:68±7%; detector: 45±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 H(2)O(2). 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 H(2)O(2), which acts as the transferrable EDHF activating BK(Ca) channels on the smooth muscle cells.

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Figures

Figure 1

Figure 1

Two HCAs were connected in series with donor (with endothelium, +E) upstream and detector vessel (without endothelium, -E) downstream. A. When flow proceeds from donor to detector, both donor and detector vessel dilated. B. With flow was reversed, only the donor dilated, but not detector vessels.

Figure 2

Figure 2

Effect of PEG-CAT (500 U/ml) on FMD in donor vessels (A) and detector vessels (B). When PEG-CAT was placed in detector vessel chamber (cross bar), FMD was inhibited in detector vessels, but was reserved in donor vessels. When PEG-CAT was placed in the perfusate traversing both vessels (gray bar), FMD was eliminated in both donor and detector vessels.

Figure 3

Figure 3

Effect of paxilline on H2O2 induce dilation in human coronary arterioles. H2O2 elicited dose-dependent vasodilation, which was significantly inhibited by 100 nM paxilline.

Figure 4

Figure 4

Effect of effluent from donor vessel on K+ channel activity in cell-attached patches of coronary smooth muscle cells. As indicated in sample traces (A) and summarized data (B), effluent from donor vessel greatly enhanced open state probability in cell-attached patches of smooth muscle cells. The enhancement was blocked by 100 nmol/L iberiotoxin.

Figure 5

Figure 5

Effect of PEG-CAT on K+ channel opening induced by effluent from donor vessel in cell-attached patches of coronary smooth muscle cells. The increased opening of K+ channels by effluent was abolished in the presence of PEG-CAT as illustrated in sample traces (A) and summarized data (B).

Figure 6

Figure 6

Effect of effluent from donor vessel on K+ activity in inside-out patches of coronary smooth muscle cells. K+ channel activity was significantly reduced in response to vessel effluent after elimination of intracellular components. A. Sample traces. B. Data summarized from 6 experiments.

Figure 7

Figure 7

A. A significant reduction in H2O2 concentration was observed in effluent from CAT-column compared to effluent from CF-column. B. Sample images comparing fluorescence intensity of DCFH representing the production of H2O2. DCFH fluorescence intensities were increased in HCA exposed to effluent from donor vessel. Fluorescence intensities were greatly reduced in HCA incubated with effluent passing through the CAT-column. C. Summary of fluorescence intensities (normalized to control) in 4 arteries of each group. Donor effluent-induced increases in DCFH fluorescence were reduced in vessels exposed to effluent from CAT-column.

Figure 8

Figure 8

Comparison of dilator response of detector vessels to effluent from donor vessel, CF-column or CAT-column. Detector vessel dilated to effluent from donor vessels or CF-column in as volume of donor effluent increase. The dilator response was significantly reduced in detector vessels incubated in effluent from CAT-column.

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