title: Docosahexaenoic acid attenuates hypoxic pulmonary vasoconstriction by activating the large conductance Ca2+-activated K+ currents in pulmonary artery smooth muscle cells.
abstract: BACKGROUND
  The inhibition of potassium (K(+)) channels plays an important role in pulmonary circulation for its close relationship with hypoxic pulmonary vasoconstriction (HPV). Docosahexaenoic acid (DHA), a n-3 polyunsaturated fatty acid, is well known for its prevention and treatment of cardiovascular diseases. However the role which DHA plays in HPV remains unclear. Here, we tested the hypothesis that DHA contributes to pulmonary vascular tone by activating the large conductance Ca(2+)-activated K(+) (BKCa) channels via calcium sparks.
  
  
  RESULTS
  Isolated resistance pulmonary artery preparation was used to study the vasomotor response to DHA. Pulmonary artery smooth muscle cells (PASMCs) were isolated from third- to fourth order branches of pulmonary arteries by collagenase digestion method. BKCa and the voltage-dependent potassium channel (Kv) currents in PASMCs were measured by the whole-cell patch-clamp technique. Fluo-8 was used as a fluorescence indicator for the real-time measurement of calcium dynamics in PASMCs. DHA dilated resistance pulmonary arteries in a dose-dependent manner in hypoxic or normoxic solution, and the effects of DHA were abolished after pre-treatment with heparin (100 μg/ml), a 1,4,5-triphosphate (IP3) receptor (IP3R) inhibitor or iberiotoxin (100 nmol/L), a specific inhibitor of BKCa channel. DHA activated BKCa channels in a dose-dependent manner, however, the activation induced by DHA was not seen in PASMCs pre-incubated with heparin. While the Kv currents decreased from 102.6 ± 5.4 to 36.5 ± 6.7 pA/pF by addition of 10 μmol/L DHA. DHA also caused calcium sparks in PASMCs. Moreover, hypoxia inhibited BKCa currents in PASMCs, but this inhibition was reversed by DHA.
  
  
  CONCLUSIONS
  Our findings suggest that DHA is a novel BKCa opener in PASMCs, which may indicate a potential therapeutic role in HPV.
authors.affiliation: Department of Cardiology, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu Province 212001, China. Electronic address: yanjinchuan@hotmail.com.
authors.forename: Jinchuan
authors.initials: J
authors.lastname: Yan
authors.affiliation: Department of Cardiology, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu Province 212001, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Cardiology, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu Province 212001, China. Electronic address: jdfylpj@sina.com.
authors.forename: Peijing
authors.initials: P
authors.lastname: Liu
authors.affiliation: Institute of Molecular Medicine, Peking University, Beijing 100871, China.
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Gu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015687:Cell Hypoxia; D017364:Collagenases / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006493:Heparin / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D004281:Docosahexaenoic Acids; C064719:iberiotoxin; D006493:Heparin; D017364:Collagenases; D002118:Calcium
keywords: BK(Ca) channel; Docosahexaenoic acid; Hypoxia; Pulmonary arterial smooth muscle cell