Protein phosphatase 2A and Ca2+-activated K+ channels contribute to 11,12-epoxyeicosatrienoic acid analog mediated mesenteric arterial relaxation.
Epoxyeicosatrienoic acids (EETs) are considered to be endothelium-derived hyperpolarizing factors, and are potent activators of the large-conductance, Ca(2+)-activated K(+) (BK(Ca)) channel in vascular smooth muscle. Here, we investigate the signal transduction pathway involved in the activation of BK(Ca) channels by 11,12-EET and 11,12-EET stable analogs in rat mesenteric vascular smooth muscle cells. 11,12-EET and the 11,12-EET analogs, 11-nonyloxy-undec-8(Z)-enoic acid (11,12-ether-EET-8-ZE), 11-(9-hydroxy-nonyloxy)-undec-8(Z)-enoic acid (11,12-ether-EET-8-ZE-OH) and 11,12-trans-oxidoeicosa-8(Z)-enoic acid (11,12-tetra-EET-8-ZE), caused vasorelaxation of mesenteric resistance arteries. Mesenteric myocyte whole-cell (perforated-patch) currents were substantially (approximately 150%) increased by 11,12-EET and 11,12-EET analogs. Single-channel recordings were conducted to identify the target for 11,12-EET. 11,12-EET and 11,12-EET analogs also increased mesenteric myocyte BK(Ca) channel activity in cell-attached patches. Similar results were obtained in cell-free patches. Baseline mesenteric myocyte BK(Ca) channel activity (NPo) in cell-free patches averaged less than 0.001 at +50 mV and 11,12-EET (1 micromol/L) increased NPo to 0.03+/-0.02 and 11,12-EET analogs (1 micromol/L) increased NPo to 0.09+/-0.006. Inhibition of protein phosphatase 2A (PP2A) activity with okadaic acid (10 nmol/L) completely reversed 11,12-EET stimulated BK(Ca) channel activity and greatly attenuated 11,12-ether-EET-8-ZE mesenteric resistance artery vasorelaxation. 11,12-EET and 11,12-EET analogs increased mesenteric myocyte PP2A activity by 3.5-fold. Okadaic acid and the EET inhibitor, 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) inhibited the 11,12-EET mediated increase in PP2A activity. These findings provide initial evidence that PP2A activity contributes to 11,12-EET and 11,12-EET analog activation of mesenteric resistant artery BK(Ca) channels and vasorelaxation.
Dimitropoulou
Christiana
C
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA, USA.
West
Lashondra
L
Field
Mary B
MB
White
Richard E
RE
Reddy
L Manmohan
LM
Falck
John R
JR
Imig
John D
JD
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects* / Q000201:enzymology*; D032342:Muscle Cells / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D054648:Protein Phosphatase 2; D051381:Rats; D017207:Rats, Sprague-Dawley; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D018999:Charybdotoxin; D019319:Okadaic Acid; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D015126:8,11,14-Eicosatrienoic Acid