Expression of IL-4 receptor α on smooth muscle cells is not necessary for development of experimental allergic asthma

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 a (IL-4R alpha) 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-4R alpha in smooth muscle cells was examined in vivo. Methods: By using transgenic smooth muscle myosin heavy chain(cre)IL-4R alpha(-/lox) mice deficient in IL-4R alpha in smooth muscle cells, in vivo effects of impaired IL-4R alpha 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-4R alpha(-/lox) mice compared with control animals. Conclusion: The impairment of IL-4R alpha on smooth muscle cells had no effect on major etiologic markers of allergic asthma. These findings suggest that IL-4R alpha responsiveness in airway smooth muscle cells during the early phase of allergic asthma is not, as suggested, necessary for the outcome of the disease. (J Allergy Clin Immunol 2010;126:347-54.)