Smooth muscle relaxation and activation of the large conductance Ca++ - activated K+ (BKCa) channel by novel oestrogens

Jacqueline Maher, A.C. Hunter, Jon Mabley, J.D. Lippiat, Marcus Allen

Research output: Contribution to journalArticleResearchpeer-review

Abstract

BACKGROUND AND PURPOSE: Oestrogens can interact directly with membrane receptors and channels and can activate vascular BKCa channels. We hypothesised that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BKCa channel, rather than at an intracellular site. EXPERIMENTAL APPROACH: We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable. KEY RESULTS: Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol induced relaxation was iberiotoxin-sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol. CONCLUSIONS AND IMPLICATIONS: The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on nitric oxide and BKCa channel activation. The activation of BKCa currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane- impermeant Quat DME-oestradiol, lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.
Original languageEnglish
JournalBritish Journal of Pharmacology
Volume169
Issue number5
DOIs
Publication statusPublished - 16 Apr 2013

Fingerprint

Muscle Relaxation
Smooth Muscle
Estradiol
Estrogens
HEK293 Cells
Estrone
Binding Sites
Membranes
Ion Channels
Ammonium Compounds
Endothelium
Blood Vessels
Aorta
Hydrogen
Potassium
Nitric Oxide
Antioxidants
estrone oxime

Bibliographical note

© 2013 Wiley-Blackwell

Keywords

  • oestrogens
  • Ca++-activated K+ channel
  • β1 subunit

Cite this

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title = "Smooth muscle relaxation and activation of the large conductance Ca++ - activated K+ (BKCa) channel by novel oestrogens",
abstract = "BACKGROUND AND PURPOSE: Oestrogens can interact directly with membrane receptors and channels and can activate vascular BKCa channels. We hypothesised that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BKCa channel, rather than at an intracellular site. EXPERIMENTAL APPROACH: We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable. KEY RESULTS: Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol induced relaxation was iberiotoxin-sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol. CONCLUSIONS AND IMPLICATIONS: The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on nitric oxide and BKCa channel activation. The activation of BKCa currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane- impermeant Quat DME-oestradiol, lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.",
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Smooth muscle relaxation and activation of the large conductance Ca++ - activated K+ (BKCa) channel by novel oestrogens. / Maher, Jacqueline; Hunter, A.C.; Mabley, Jon; Lippiat, J.D.; Allen, Marcus.

In: British Journal of Pharmacology, Vol. 169, No. 5, 16.04.2013.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Smooth muscle relaxation and activation of the large conductance Ca++ - activated K+ (BKCa) channel by novel oestrogens

AU - Maher, Jacqueline

AU - Hunter, A.C.

AU - Mabley, Jon

AU - Lippiat, J.D.

AU - Allen, Marcus

N1 - © 2013 Wiley-Blackwell

PY - 2013/4/16

Y1 - 2013/4/16

N2 - BACKGROUND AND PURPOSE: Oestrogens can interact directly with membrane receptors and channels and can activate vascular BKCa channels. We hypothesised that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BKCa channel, rather than at an intracellular site. EXPERIMENTAL APPROACH: We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable. KEY RESULTS: Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol induced relaxation was iberiotoxin-sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol. CONCLUSIONS AND IMPLICATIONS: The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on nitric oxide and BKCa channel activation. The activation of BKCa currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane- impermeant Quat DME-oestradiol, lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.

AB - BACKGROUND AND PURPOSE: Oestrogens can interact directly with membrane receptors and channels and can activate vascular BKCa channels. We hypothesised that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BKCa channel, rather than at an intracellular site. EXPERIMENTAL APPROACH: We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable. KEY RESULTS: Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol induced relaxation was iberiotoxin-sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol. CONCLUSIONS AND IMPLICATIONS: The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on nitric oxide and BKCa channel activation. The activation of BKCa currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane- impermeant Quat DME-oestradiol, lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.

KW - oestrogens

KW - Ca++-activated K+ channel

KW - β1 subunit

U2 - 10.1111/bph.12211

DO - 10.1111/bph.12211

M3 - Article

VL - 169

JO - British Journal of Pharmacology

JF - British Journal of Pharmacology

SN - 0007-1188

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