Endothelin-1 mediates hypoxia-induced inhibition of voltage-gated K+ channel expression in pulmonary arterial myocytes.
Prolonged exposure to decreased oxygen tension causes contraction and proliferation of pulmonary arterial smooth muscle cells (PASMCs) and pulmonary hypertension. Hypoxia-induced inhibition of voltage-gated K(+) (K(v)) channels may contribute to the development of pulmonary hypertension by increasing intracellular calcium concentration ([Ca(2+)](i)). The peptide endothelin-1 (ET-1) has been implicated in the development of pulmonary hypertension and acutely decreases K(v) channel activity. ET-1 also activates several transcription factors, although whether ET-1 alters K(V) channel expression is unclear. The hypoxic induction of ET-1 is regulated by the transcription factor hypoxia-inducible factor-1 (HIF-1), which we demonstrated to regulate hypoxia-induced decreases in K(V) channel activity. In this study, we tested the hypothesis that HIF-1-dependent increases in ET-1 lead to decreased K(v) channel expression and subsequent elevation in [Ca(2+)](i). Resting [Ca(2+)](i) and K(v) channel expression were measured in cells exposed to control (18% O(2), 5% CO(2)) and hypoxic (4% O(2), 5% CO(2)) conditions. Hypoxia caused a decrease in expression of K(v)1.5 and K(v)2.1 and a significant increase in resting [Ca(2+)](i). The increase in [Ca(2+)](i) was reduced by nifedipine, an inhibitor of voltage-dependent calcium channels, and removal of extracellular calcium. Treatment with BQ-123, an ET-1 receptor inhibitor, prevented the hypoxia-induced decrease in K(v) channel expression and blunted the hypoxia-induced increase in [Ca(2+)](i) in PASMCs, whereas ET-1 mimicked the effects of hypoxia. Both hypoxia and overexpression of HIF-1 under normoxic conditions increased ET-1 expression. These results suggest that the inhibition of K(v) channel expression and rise in [Ca(2+)](i) during chronic hypoxia may be the result of HIF-1-dependent induction of ET-1.
Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA.
E Miles
EM
Whitman
Sarah
S
Pisarcik
Trevor
T
Luke
Michele
M
Fallon
Jian
J
Wang
J T
JT
Sylvester
Gregg L
GL
Semenza
Larissa A
LA
Shimoda
D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D019332:Endothelin-1 / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D051666:Kv1.5 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008954:Models, Biological; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010477:Perfusion; D010880:Piperidines / Q000494:pharmacology; D011651:Pulmonary Artery / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D051669:Shab Potassium Channels / Q000235:genetics / Q000378:metabolism*
D019332:Endothelin-1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051666:Kv1.5 Potassium Channel; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D051669:Shab Potassium Channels; C086539:BQ 788; C072247:cyclo(Trp-Asp-Pro-Val-Leu)