Ca2+-signaling in airway smooth muscle cells is altered in T-bet knock-out mice.
BACKGROUND
Airway smooth muscle cells (ASMC) play a key role in bronchial hyperresponsiveness (BHR). A major component of the signaling cascade leading to ASMC contraction is calcium. So far, agonist-induced Ca2+-signaling in asthma has been studied by comparing innate properties of inbred rat or mouse strains, or by using selected mediators known to be involved in asthma. T-bet knock-out (KO) mice show key features of allergic asthma such as a shift towards TH2-lymphocytes and display a broad spectrum of asthma-like histological and functional characteristics. In this study, we aimed at investigating whether Ca2+-homeostasis of ASMC is altered in T-bet KO-mice as an experimental model of asthma.


METHODS
Lung slices of 100 to 200 microm thickness were obtained from T-bet KO- and wild-type mice. Airway contraction in response to acetylcholine (ACH) was measured by video-microscopy and Ca2+-signaling in single ASMC of lung slices was assessed using two-photon-microscopy.


RESULTS
Airways from T-bet KO-mice showed increased baseline airway tone (BAT) and BHR compared to wild-type mice. This could be mimicked by incubation of lung slices from wild-type mice with IL-13. The increased BAT was correlated with an increased incidence of spontaneous changes in intracellular Ca2+-concentrations, whereas BHR correlated with higher ACH-induced Ca2+-transients and an increased proportion of ASMC showing Ca2+-oscillations. Emptying intracellular Ca2+-stores using caffeine or cyclopiazonic acid induced higher Ca2+-elevations in ASMC from T-bet KO- compared to wild-type mice.


CONCLUSIONS
Altered Ca2+-homeostasis of ASMC contributes to increased BAT and BHR in lung slices from T-bet KO-mice as a murine asthma model. We propose that a higher Ca2+-content of the intracellular Ca2+-stores is involved in the pathophysiology of these changes.
Bergner
Albrecht
A
Pneumology, Medizinische Klinik-Innenstadt, Ludwig-Maximilians-University, Munich, Germany. albrecht.bergner@med.uni-muenchen.de
Kellner
Julia
J
Silva
Anita Kemp da
AK
Gamarra
Fernando
F
Huber
Rudolf M
RM
D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D006706:Homeostasis / Q000502:physiology; D008168:Lung / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics; D000098815:T-bet Transcription Factor
D020825:T-Box Domain Proteins; D000098815:T-bet Transcription Factor; D014157:Transcription Factors