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Decreased membrane cholesterol facilitates depolarizationinduced Ca 2+ ‐sensitization in pulmonary vascular smooth muscle following chronic hypoxia
Author(s) -
Norton Charles E,
Naik Jay S,
Walker Benjimen R,
Resta Thomas C
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.873.14
Subject(s) - sensitization , depolarization , cholesterol , chemistry , vascular smooth muscle , biophysics , medicine , endocrinology , membrane potential , hypoxia (environmental) , filipin , biochemistry , biology , smooth muscle , oxygen , immunology , organic chemistry
Previous studies support a role for caveolin‐1 (cav‐1) dysfunction in membrane depolarization‐induced Ca 2+ sensitization in pulmonary vascular smooth muscle (VSM) from rats exposed to chronic hypoxia (CH). Because caveolar cholesterol content is important in regulation of cav‐1‐protein interactions, we hypothesized that reduced membrane cholesterol contributes to enhanced Ca 2+ sensitivity following CH. We therefore examined vasoconstrictor responses to depolarizing concentrations of KCl (30–120 mM) under VSM Ca 2+ ‐clamp conditions following administration of supplemental cholesterol [500 μM ‐ 5 mM methyl‐β‐cyclodextrin (MβCD)], or cholesterol depletion (MβCD, 10 mM) in pressurized endothelium‐disrupted pulmonary arteries (~150 μm diameter) from control and CH (4 wk at 0.5 atm) rats. Consistent with our hypothesis, cholesterol repletion decreased KCl‐dependent constriction in CH arteries and normalized reactivity between groups, while MβCD had no effect in either group. Additionally, CH reduced membrane cholesterol content as determined by filipin fluorescence. However, CH did not affect either arterial cav‐1 levels or caveolar density assessed by western blot and electron microscopy, respectively. We conclude that decreased membrane cholesterol is necessary but not sufficient for enhanced depolarization‐induced pulmonary VSM Ca 2+ ‐ sensitization following CH.