Enhanced Ca2+ sensitivity in hyperresponsive cultured bronchi is mediated by TNFalpha and NF-kappaB.
The mechanical properties and Ca2+ sensitivity of an organ-culture model derived from guinea pig airways have been examined. The cultured explants develop airway hyperresponsiveness to pharmacological agonists after 3-day culture, when compared with fresh and ovalbumin-sensitized tissues. The reactivity of cultured explants is dependent on the presence of the epithelium. They are also sensitive to glucocorticosteroid pretreatments, which neutralize the TNFalpha antibody and NF-kappaB inhibitor. Hence, specific immunostaining of NF-kappaB subunits (p65 and p50) was increased in the nuclear extract of cultured explants. In beta-escin-permeabilized preparations, step-increases in pCa revealed enhanced Ca2+ sensitivity of the contractile apparatus in cultured explants, which was prevented by epithelium removal. Pretreatments of cultured explants with neutralizing TNFalpha antibody and NF-kappaB inhibitor consistently reduced their Ca2+ sensitivity. These findings suggest that AHR developed in this organ culture model may be triggered by an inflammatory process mediated by the TNFalpha and NF-kappaB transcription factor, which results in an increased sensitivity to [Ca2+]i.
Morin
Caroline
C
Le Bilarium, Département de Physiologie et Biophysique, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
Rousseau
Eric
E
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D019138:Antibodies, Blocking / Q000494:pharmacology; D000941:Antigens / Q000276:immunology; D015153:Blotting, Western; D001980:Bronchi / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D002118:Calcium / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells / Q000502:physiology; D004928:Escin / Q000494:pharmacology; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D006168:Guinea Pigs; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008856:Microscopy, Fluorescence; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology*; D009924:Organ Culture Techniques; D010047:Ovalbumin / Q000276:immunology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000502:physiology*
D000893:Anti-Inflammatory Agents; D019138:Antibodies, Blocking; D000941:Antigens; D005938:Glucocorticoids; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D004928:Escin; D010047:Ovalbumin; D002118:Calcium