title: Caveolin-1 in cytokine-induced enhancement of intracellular Ca(2+) in human airway smooth muscle.
abstract: Diseases such as asthma are characterized by airway hyperresponsiveness. Enhanced airway smooth muscle (ASM) intracellular Ca(2+) ([Ca(2+)](i)) response to agonist stimulation leading to increased airway constriction has been suggested to contribute to airway hyperresponsiveness. Caveolae are flask-shaped plasma membrane invaginations that express the scaffolding protein caveolin and contain multiple proteins important in [Ca(2+)](i) signaling (e.g., agonist receptors, ion channels). We recently demonstrated that caveolae and caveolin-1 are important in [Ca(2+)](i) regulation in human ASM. Proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-13 modulate [Ca(2+)](i) in ASM. We hypothesized that cytokine upregulation of caveolar signaling in ASM contributes to enhanced agonist-induced [Ca(2+)](i) in inflammation. Enzymatically dissociated human ASM cells were exposed to medium (control), 20 ng/ml TNF-α, or 50 ng/ml IL-13 for 24 h. Caveolae-enriched membrane fractions displayed substantial increase in caveolin-1 and -2 expressions by TNF-α and IL-13. Transfection with caveolin-1-mRed DNA substantially accelerated and increased plasma membrane caveolin-1 expression by TNF-α and to a lesser extent by IL-13. Caveolin-1 enhancement was inhibited by nuclear factor-κB and mitogen-activated protein kinase inhibitors. In fura 2-loaded ASM cells, [Ca(2+)](i) responses to 1 μM ACh, 10 μM histamine, or 10 nM bradykinin were all exaggerated by TNF-α as well as IL-13 exposure. However, disruption of caveolae using caveolin-1 suppression via small-interfering RNA resulted in significant blunting of agonist-induced [Ca(2+)](i) responses of vehicle and TNF-α-exposed cells. These functional data were correlated to the presence of TNFR(1) receptor (but not the IL-4/IL-13 receptor) within caveolae. Overall, these results indicate that caveolin-1 plays an important role in airway inflammation by modulating the effect of specific cytokines on [Ca(2+)](i).
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Venkatachalem
authors.initials: V
authors.lastname: Sathish
authors.forename: Amard J
authors.initials: AJ
authors.lastname: Abcejo
authors.forename: Sarah Kay
authors.initials: SK
authors.lastname: VanOosten
authors.forename: Michael A
authors.initials: MA
authors.lastname: Thompson
authors.forename: Y S
authors.initials: YS
authors.lastname: Prakash
authors.forename: Christina M
authors.initials: CM
authors.lastname: Pabelick
mesh_terms: D015153:Blotting, Western; D001920:Bradykinin / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D021941:Caveolae / Q000187:drug effects* / Q000378:metabolism; D051242:Caveolin 1 / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D005453:Fluorescence; D015870:Gene Expression; D020868:Gene Silencing / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D018793:Interleukin-13 / Q000378:metabolism / Q000494:pharmacology*; D018613:Microscopy, Confocal; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D051242:Caveolin 1; D018793:Interleukin-13; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D006632:Histamine; D020928:Mitogen-Activated Protein Kinases; D001920:Bradykinin; D002118:Calcium