View Abstract

A1231 - Inhibition of Gq Signaling Induces Airway Relaxation in Mouse Models of Asthma
Author Block: D. Wenzel1, M. Matthey1, R. Roberts2, A. Seidinger1, A. Simon1, R. Schröder3, M. Kuschak4, S. Annala3, G. König5, C. E. Müller4, I. P. Hall6, E. Kostenis3, B. K. Fleischmann1; 1Institute of Physiology I, University of Bonn, Bonn, Germany, 2University Hospital of Nottingham, Nottingham, United Kingdom, 3Molecular-, Cellular-, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany, 4Institute of Pharmaceutical Chemistry I,, University of Bonn, Bonn, Germany, 5Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany, 6Univ Hosp of Nottingham, Nottingham NG7 2UH, United Kingdom.
Rationale: G protein coupled receptors (GPCRs) that are coupled to Gq play an important role in controlling the tone of airway smooth muscle. The activation of many of these receptors induces an increase of airway resistance, which is a hallmark of airway hyperresponsiveness. Moreover, increased expression of Gq and elevated Gq coupled receptor agonists have been found in animal models or patients with asthma. Because there is a number of patients that does not respond well to current treatment regimens for asthma we sought to explore the impact of the recently reported Gq protein inhibitor FR900359 (FR) on the regulation of airway tone in health and disease.
Methods: We have tested FR in isolated airway smooth muscle cells (ASMCs) using dynamic mass redistribution (DMR) and Ca2+ imaging measurements. The peptide`s effects on airway tone regulation in different species were determined by a wire-myograph or precision cut lung slices (PCLS) ex vivo. Additionally, we applied FR locally to the lung in mouse in vivo and determined airway resistance, cardiovascular parameters as well as tissue levels of the peptide. Finally, we assessed the effects of FR in ovalbumin (OVA)-induced and house dust mite (HDM)-induced murine asthma models.
Results: FR specifically inhibited Gq-dependent responses in DMR and Ca2+ imaging experiments of human and mouse ASMCs. In the wire-myograph FR induced a dose-dependent bronchorelaxation in tissues from mouse, pig and humans. Also in PCLS FR was able to reverse Gq-dependent constriction of intrapulmonary airways completely. When FR was applied as an aerosol to the lungs of mice in vivo, more than 10-fold higher local concentrations of the peptide were obtained compared to other tissues and plasma. These prevented the increase of airway resistance by Gq-dependent agonists without inducing cardiovascular side effects. In the OVA- or HDM-induced asthma models FR abrogated airway hyperresponsiveness when given to already asthmatic animals or given during the challenge period of the induction protocol. Interestingly, there was no effect on the number of inflammatory cells in bronchoalveolar lavage.
Conclusion: Our data demonstrate that the pharmacological Gq inhibitor FR is a powerful bronchorelaxant in healthy and allergen-sensitized mice and does not induce systemic side effects when locally applied.