Annexin-1-deficient mice exhibit spontaneous airway hyperresponsiveness and exacerbated allergen-specific antibody responses in a mouse model of asthma
Correspondence: Dr L. H. K. Lim, Inflammation and Cancer Lab, Immunology Program, Centre for Life Sciences (#03-06J), National University of Singapore, 28 Medical Drive, Singapore 117456. E-mail: email@example.com
Glucocorticoids are the mainstream drugs used in the treatment and control of inflammatory diseases such as asthma. Annexin-1 (ANXA1) is an anti-inflammatory protein which has been described as an endogenous protein responsible for some anti-inflammatory glucocorticoid effects. Previous studies have identified its importance in other immune diseases such as rheumatoid arthritis and cystic fibrosis. ANXA1-deficient (−/−) mice are Th2 biased, and ANXA1 N-terminus peptide exhibits anti-inflammatory activity in a rat model of pulmonary inflammation.
ANXA1 protein is found in bronchoalveolar lavage fluid from asthmatics. However, the function of ANXA1 in the pathological development of allergy or asthma is unclear. Thus, in this study we intended to examine the effect of ANXA1 deficiency on allergen-specific antibody responses and airway responses to methacholine (Mch).
ANXA1−/− mice were sensitized with ovalbumin (OVA) and challenged with aerosolized OVA. Airway resistance, lung compliance and enhanced pause (PenH) were measured in naïve, sensitized and saline or allergen-challenged wild-type (WT) and ANXA1−/− mice. Total and allergen-specific antibodies were measured in the serum.
We show that allergen-specific and total IgE, IgG2a and IgG2b levels were significantly higher in ANXA1−/− mice. Furthermore, naïve ANXA1−/− mice displayed higher airway hypersensitivity to inhaled Mch, and significant differences were also observed in allergen-sensitized and allergen-challenged ANXA1−/− mice compared with WT mice.
In conclusion, ANXA1−/− mice possess multiple features characteristic to allergic asthma, such as airway hyperresponsiveness and enhanced antibody responses, suggesting that ANXA1 plays a critical regulatory role in the development of asthma.
We postulate that ANXA1 is an important regulatory factor in the development of allergic disease and dysregulation of its expression can lead to pathological changes which may affect disease progression.