Both Hematopoietic-Derived and Non–Hematopoietic-Derived β-Arrestin–2 Regulates Murine Allergic Airway Disease

Abstract

Allergic asthma, a major cause of morbidity and leading cause of hospitalizations, is an inflammatory disease orchestrated by T helper cells and characterized by the lung migration of eosinophils, which are important asthma effector cells. Lung migration of inflammatory cells requires, among other events, the chemokine receptor transduction of lung-produced inflammatory chemokines. Despite the widespread prevalence of this disease, the molecular mechanisms regulating chemokine production and receptor regulation in asthma are poorly understood. Previous work from our laboratory demonstrated that b-arrestin22 positively regulates the development of allergic airway disease in a mouse model, partly through positive regulation of T-lymphocyte chemotaxis to the lung. However, b-arrestin22 is expressed in many cell types, including other hematopoietic cells and lung structural cells, which are involved in the development and manifestation of allergic airway disease. To determine the cell types required for b-arrestin-2-dependent allergic inflammation, we generated bone marrow chimera mice. Using the ovalbumin murine model of allergic airway disease, we show that eosinophilic and lymphocytic inflammation is restored in chimeric mice, with expression of b-arrestin22 exclusively on hematopoieticderived cell types. In contrast, airway hyperresponsiveness is dependent on the expression of b-arrestin22 in structural cells. Our data demonstrate that the expression of b-arrestin22 in at least two divergent cell types contributes to the pathogenesis of allergic airway disease.

Genetic Deletion of β-Arrestin-2 and the Mitigation of Established Airway Hyperresponsiveness in a Murine Asthma Model

“…There is good evidence to suggest that barr2-dependent signaling downstream of b2ARs and chemokine receptors is proinflammatory in asthma (16)(17)(18)22). barr2 promotes the chemotaxis of lymphocytes and eosinophils to the airways (1,16,17,28).…”

“…barr2 positively regulates inflammatory cell migration to the lung in a murine model of allergic airway inflammation. In particular, lung migration of CD4 1 T cells and eosinophils is impaired in barr2-knockout (KO) mice (16,17 To generate the conditional knockout arrb2 allele, coding exon 2 of arrb2 was flanked by loxP sequences. The loxP-flanked exon 2 was excised from arrb2 by tamoxifen-inducible Cre recombinase.…”

“…For differential cell counts, cytocentrifuged lavage preparations were stained using a Hema-3 staining kit (Fisher Scientific, Kalamazoo, MI), and 200 cells were classified using standard morphologic criteria (details are provided in the online supplement) (17).…”

“…Paraformaldehyde-fixed, paraffinembedded lung sections were stained with hematoxylin and eosin or periodic acid Schiff for evaluation of cellular inflammation or airway mucin content, respectively, using a four-tiered semiquantitative scoring method (details are provided in the online supplement) that was performed in a blinded manner (17,18).…”

β-Arrestin2 mediates progression of murine primary myelofibrosis

“…In a paper by Hollingsworth et al, for example, the authors transplanted βarr2 -/-donor cells into WT recipients and WT cells into βarr2 -/-mice. In both scenarios, high and equal engraftment of donor cells was achieved in recipient mice, demonstrating that it is possible to achieve long-term engraftment of βarr2 -/-cells in a murine transplant model (40). However, these transplants were done with unmanipulated cells, as opposed to the cells used in our PMF model that are characterized by excessive cell proliferation and associated cellular stress.…”