Faculty Collaboration Database

Endothelium-derived hyperpolarizing factor in human internal mammary artery is 11,12-epoxyeicosatrienoic acid and causes relaxation by activating smooth muscle BK(Ca) channels. Circulation 2003 Feb 11;107(5):769-76

Date

02/13/2003

Pubmed ID

12578883

DOI

10.1161/01.cir.0000047278.28407.c2

Scopus ID

2-s2.0-0037432150 (requires institutional sign-in at Scopus site)   240 Citations

Abstract

BACKGROUND: Left internal mammary arteries (LIMAs) synthesize endothelium-derived hyperpolarizing factor (EDHF), a short-lived K(+) channel activator that persists after inhibition of nitric oxide (NO) and prostaglandin synthesis. EDHF hyperpolarizes and relaxes smooth muscle cells (SMCs). The identity of EDHF in humans is unknown. We hypothesized that EDHF (1) is 11,12-epoxyeicosatrienoic acid (11,12-EET); (2) is generated by cytochrome P450-2C, CYP450-2C; and (3) causes relaxation by opening SMC large-conductance Ca(2+)-activated K(+) channels (BK(Ca)).

METHODS AND RESULTS: The identity of EDHF and its mechanism of action were assessed in 120 distal human LIMAs and 20 saphenous veins (SVs) obtained during CABG. The predominant EET synthesized by LIMAs is 11,12-EET. Relaxations to exogenous 11,12-EET and endogenous EDHF are of similar magnitudes. Inhibition of EET synthesis by chemically distinct CYP450 inhibitors (17-octadecynoic acid, N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide), or a selective EET antagonist (4,15-epoxyeicosa-5(Z)-enoic acid) impairs EDHF relaxation. 11,12-EET activates a BK(Ca) current and hyperpolarizes LIMA SMCs. Inhibitors of BK(Ca) but not inward-rectifier or small-conductance K(Ca) channels abolish relaxation to endogenous EDHF and exogenous 11,12-EET. BK(Ca) and CYP450-2C mRNA and proteins are more abundant in LIMAs than in SVs, perhaps explaining the lack of EDHF activity of the SV. Laser capture microdissection and quantitative RT-PCR demonstrate that BK(Ca) channels are primarily in vascular SMCs, whereas the CYP450-2C enzyme is present in both the endothelium and SMCs.

CONCLUSIONS: In human LIMAs, EDHF is 11,12-EET produced by an EDHF synthase CYP450-2C and accounting for approximately 40% of net endothelial relaxation. 11,12-EET causes relaxation by activating SMC BK(Ca) channels.

Author List

Archer SL, Gragasin FS, Wu X, Wang S, McMurtry S, Kim DH, Platonov M, Koshal A, Hashimoto K, Campbell WB, Falck JR, Michelakis ED

Author

William B. Campbell PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

8,11,14-Eicosatrienoic Acid
Acetylcholine
Biological Factors
Bradykinin
Cytochrome P-450 Enzyme System
Humans
In Vitro Techniques
Large-Conductance Calcium-Activated Potassium Channels
Mammary Arteries
Muscle, Smooth, Vascular
Nitric Oxide Synthase
Patch-Clamp Techniques
Potassium Channel Blockers
Potassium Channels, Calcium-Activated
Prostaglandin-Endoperoxide Synthases
Signal Transduction
Vasodilation
Vasodilator Agents