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Altered Lipid Domains in Pulmonary Arterial Smooth Muscle Facilitate Enhanced Depolarization‐Induced Vasoconstriction following Chronic Hypoxia
Author(s) -
Ahmadian Rosstin,
Norton Charles E.,
Jernigan Nikki L.,
Paffett Michael L.,
Naik Jay S.,
Walker Benjimen R.,
Resta Thomas C.
Publication year - 2020
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.2020.34.s1.07109
Subject(s) - caveolae , depolarization , vasoconstriction , hypoxic pulmonary vasoconstriction , vascular smooth muscle , nadph oxidase , medicine , endocrinology , chemistry , caveolin 1 , biophysics , biology , biochemistry , signal transduction , oxidative stress , smooth muscle
Chronic hypoxia (CH) augments depolarization‐induced pulmonary vasoconstriction through a myofilament Ca 2+ sensitization mechanism involving epidermal growth factor receptor (EGFR) and NADPH oxidase‐dependent Rho kinase activation. Although the mechanism that links CH exposure to activation of this pathway is unknown, previous studies support a role for caveolin‐1 and cholesterol to regulate both EGFR and NADPH oxidase. Furthermore, membrane cholesterol content can influence caveolin‐1 interactions with a variety of proteins. Therefore, we hypothesized that derangement of these lipid domain components contributes to increased depolarization‐induced Ca 2+ sensitization and pulmonary vasoconstriction following CH. To test this hypothesis, we examined vasoconstrictor responses to depolarizing concentrations of KCl (30–120 mM) in pressurized, endothelium‐disrupted pulmonary arteries (~150 um diameter) from control and CH (4 wk at 0.5 atm) rats under conditions in which vascular smooth muscle Ca 2+ was clamped with ionomycin (3 mM). The effects of altered lipid domains on vasomotor responses were tested utilizing a solution of MβCD and cholesterol (10 mM and 2 mM respectively) to increase cholesterol, and the caveolin‐1 scaffolding domain peptide, AP‐Cav (10 mM). We also assessed the incidence of caveolae using transmission electron microscopy and caveolin‐1 levels by western blotting. Membrane cholesterol content was quantified by filipin (50 mg/ml) fluorescence using confocal microscopy. In agreement with our hypothesis, CH reduced membrane cholesterol content in pulmonary arterial smooth muscle. However, CH was without effect on caveolin‐1 expression or the incidence of caveolae. CH augmented vasoconstrictor sensitivity in response to depolarizing concentrations of KCl as previously described. Both cholesterol repletion and AP‐Cav prevented effects of CH to enhance KCl‐dependent constriction and normalized reactivity between groups. Interestingly, AP‐Cav restored smooth muscle membrane cholesterol in arteries from CH rats to the level of controls, consistent with evidence that caveolin‐1 can regulate cholesterol trafficking to the cell membrane. These results support an effect of AP‐Cav to attenuate KCl‐dependent vasoconstriction following CH by normalizing membrane cholesterol levels. We conclude that alterations in the lipid domains resulting from reduced cholesterol facilitate enhanced depolarization induced pulmonary vasoconstriction following CH. Support or Funding Information NIH Grants R01 HL132883 and T32 HL007736. AHA Grant 13PRE14580015