This Article Full Text Full Text (PDF) All Versions of this Article: 2006-0281OCv1 36/5/633    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Morin, C. Articles by Rousseau, E. Search for Related Content PubMed PubMed Citation Articles by Morin, C. Articles by Rousseau, E.

Epoxyeicosatrienoic Acid Relaxing Effects Involve Ca²⁺-Activated K⁺ Channel Activation and CPI-17 Dephosphorylation in Human Bronchi

Le Bilarium, Department of Physiology and Biophysics; Service of Thoracic Surgery; Department of Pathology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada

Correspondence and requests for reprints should be addressed to Eric Rousseau, Le Bilarium, Department of Physiology and Biophysics, Faculty of Medicine and Health Sciences, University of Sherbrooke, 3001 12th Avenue North, Sherbrooke, PQ, J1H 5N4 Canada. E-mail: eric.rousseau{at}usherbrooke.ca

The aim of the present study was to provide a mechanistic insight into how 14,15-epoxyeicosatrienoic acid (EET) relaxes organ-cultured human bronchi. Tension measurements, performed on either fresh or 3-d–cultured bronchi, revealed that the contractile responses to 1 µM methacholine and 10 µM arachidonic acid were largely relaxed by the eicosanoid regioisomer in a concentration-dependent manner (0.01–10 µM). Pretreatments with 14,15-epoxyeicosa-5(Z)-enoic acid, a specific 14,15-EET antagonist, prevented the relaxing effect, whereas iberitoxin pretreatments (10 nM) partially abolished EET-induced relaxations. In contrast, pretreatments with 1 µM indomethacin amplified relaxations in explants and membrane hyperpolarizations triggered by 14,15-EET on airway smooth muscle cells. The relaxing responses induced by 14,15-EET were likely related to reduced Ca²⁺ sensitivity of the myofilaments, because free Ca²⁺ concentration–response curves performed on -escin–permeabilized cultured explants were shifted toward higher [Ca²⁺] (lower pCa²⁺ values). 14,15-EET also abolished the tonic responses induced by phorbol-ester-dybutyrate (PDBu) (a protein kinase C [PKC]–sensitizing agent), on both fresh (intact) and -escin–permeabilized explants. Western blot analyses, using two specific primary antibodies against CPI-17 and its PKC-dependent phosphorylated isoform (p-CPI-17), confirmed that the eicosanoid interferes with this intracellular process. These data indicate that 14,15-EET hyperpolarizes airway smooth muscle cells and relaxes precontracted human bronchi while reducing Ca²⁺ sensitivity of fresh and cultured explants. The intracellular effects are related to a PKC-dependent process involving a lower phosphorylation level of CPI-17.

Key Words: calcium sensitivity • CPI-17 • epoxyeicosatrienoic acid • membrane potential • organ culture

CLINICAL RELEVANCE The current research and the results obtained may be highly relevant for human diseases such as asthma and chronic obstructive pulmonary disease.

 

This article has been cited by other articles:

				E. K. Hoffmann, I. H. Lambert, and S. F. Pedersen Physiology of Cell Volume Regulation in Vertebrates Physiol Rev, January 1, 2009; 89(1): 193 - 277. [Abstract] [Full Text] [PDF]

				C. Morin, M. Sirois, V. Echave, E. Rizcallah, and E. Rousseau Relaxing effects of 17(18)-EpETE on arterial and airway smooth muscles in human lung Am J Physiol Lung Cell Mol Physiol, January 1, 2009; 296(1): L130 - L139. [Abstract] [Full Text] [PDF]

				C. Morin, M. Sirois, V. Echave, and E. Rousseau CPI-17 Silencing-Reduced Responsiveness in Control and TNF-{alpha}-Treated Human Bronchi Am. J. Respir. Cell Mol. Biol., December 1, 2008; 39(6): 638 - 643. [Abstract] [Full Text] [PDF]

				C. Morin, C. Guibert, M. Sirois, V. Echave, M. M. Gomes, and E. Rousseau Effects of {omega}-hydroxylase product on distal human pulmonary arteries Am J Physiol Heart Circ Physiol, March 1, 2008; 294(3): H1435 - H1443. [Abstract] [Full Text] [PDF]

				C. Morin, M. Sirois, V. Echave, M. M. Gomes, and E. Rousseau EET Displays Anti-Inflammatory Effects in TNF-{alpha} Stimulated Human Bronchi: Putative Role of CPI-17 Am. J. Respir. Cell Mol. Biol., February 1, 2008; 38(2): 192 - 201. [Abstract] [Full Text] [PDF]

				C. Morin, M. Sirois, V. Echave, M. M. Gomes, and E. Rousseau Functional effects of 20-HETE on human bronchi: hyperpolarization and relaxation due to BKCa channel activation Am J Physiol Lung Cell Mol Physiol, October 1, 2007; 293(4): L1037 - L1044. [Abstract] [Full Text] [PDF]