Background: Airflow in the lungs of patients with allergic asthma is impaired by excessive mucus production and airway smooth muscle contractions. Elevated levels of the cytokines IL-4 and IL-13 are associated with this pathology. In vitro studies have suggested that IL-4 receptor alpha (IL-4Ralpha) signaling on smooth muscle cells is critical for airway inflammation and airway hyperresponsiveness.
Objective: To define the contribution of IL-4 and IL-13 to the onset of asthmatic pathology, the role of their key receptor IL-4Ralpha in smooth muscle cells was examined in vivo.
Methods: By using transgenic smooth muscle myosin heavy chain(cre)IL-4Ralpha(-/lox) mice deficient in IL-4Ralpha in smooth muscle cells, in vivo effects of impaired IL-4Ralpha signaling in smooth muscle cells on the outcome of asthmatic disease were investigated for the first time. Allergic asthma was introduced in mice by repeated sensitization with ovalbumin/aluminum hydroxide on days 0, 7, and 14, followed by intranasal allergen challenge on days 21 to 23. Mice were investigated for the presence of airway hyperresponsiveness, airway inflammation, allergen-specific antibody production, T(h)2-type cytokine responses, and lung pathology.
Results: Airway hyperresponsiveness, airway inflammation, mucus production, T(h)2 cytokine production, and specific antibody responses were unaffected in smooth muscle myosin heavy chain(cre)IL-4Ralpha(-/lox) mice compared with control animals.
Conclusion: The impairment of IL-4Ralpha on smooth muscle cells had no effect on major etiologic markers of allergic asthma. These findings suggest that IL-4Ralpha responsiveness in airway smooth muscle cells during the early phase of allergic asthma is not, as suggested, necessary for the outcome of the disease.
Copyright 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.