Allergen-induced murine upper airway inflammation: local and systemic changes in murine experimental allergic rhinitis

Abstract

The role of inflammatory effector cells in the pathogenesis of airway allergy has been the subject of much investigation. However, whether systemic factors are involved in the development of local responses in both upper and lower airways has not been fully clarified. The present study was performed to investigate aspects of the pathogenesis of isolated allergic rhinitis in a murine model sensitized to ovalbumin (OVA). Both upper- and lower-airway physiological responsiveness and inflammatory changes were assessed, as well as bone marrow progenitor responses, by culture and immunohistological methods. Significant nasal symptoms and hyper-responsiveness appeared after intranasal OVA challenge (P < 0.0001 and P < 0.01, respectively), accompanied with significant nasal mucosal changes in CD4+ cells (P < 0.001), interleukin (IL)-4+ cells (P < 0.01), IL-5+ cells (P < 0.01), basophilic cells (P < 0.02) and eosinophils (P < 0.001), in the complete absence of hyper-responsiveness or inflammatory changes in the lower airway. In the bone marrow, there were significant increases in CD34+ cells, as well as in eosinophils and basophilic cells. In the presence in vitro of mouse recombinant IL-5, IL-3 or granulocyte-macrophage colony-stimulating factor (GM-CSF), the level of bone marrow eosinophil/basophil (Eo/Baso) colony-forming cells increased significantly in the OVA-sensitized group. We conclude that, in this murine model of allergic rhinitis, haemopoietic progenitors are upregulated, which is consistent with the involvement of bone marrow in the pathogenesis of nasal mucosal inflammation. Both local and systemic events, initiated in response to allergen provocation, may be required for the pathogenesis of allergic rhinitis. Understanding these events and their regulation could provide new therapeutic targets for rhinitis and asthma.

Figure 1

Protocol for ovalbumin (OVA) sensitization and subsequent OVA intranasal (i.n.) challenge. OVA-2w i.n. OVA group: mice in which OVA challenge was given intranasally from day 22 to day 35 after sensitization from day 1 to day 21. OVA-1w i.n. OVA group: mice that were challenged with OVA from day 22 to day 28 after sensitization. OVA-non-i.n. group: mice that were given sensitization without OVA challenge. Sham-Sham group: mice treated with diluent, during both sensitization and challenge, instead of with OVA. i.p., intraperitoneal.

Figure 2

Nasal symptoms after ovalbumin (OVA) antigen challenge. The clinical allergic nasal symptoms of (a) sneezing and (b) rubbing, were determined in sensitized mice. OVA-2w i.n. OVA: mice in which OVA challenge was given intranasally from day 22 to day 35 after sensitization from day 1 to day 21. OVA-1w i.n. OVA: mice that were challenged with OVA from day 22 to day 28 after sensitization. Sham-Sham: mice treated with diluent, during both sensitization and challenge, instead of with OVA.

Figure 3

Upper and lower airway responsiveness in sensitized and nonsensitized mice. (a) Nasal histamine responsiveness as represented by the limiting concentration of histamine that caused sneezing and itching. (b) Lower airway responsiveness based on the total lower respiratory system resistance to increasing intravenous doses of methacholine. Filled triangle, ovalbumin (OVA)-2w intranasal (i.n.) OVA group; filled square, OVA-1w i.n. OVA group; filled circle, Sham-Sham group.

Figure 4

Immunohistochemistry of murine ovalbumin (OVA)-sensitized nasal mucosa. (a) Eosinophils (pink-cytoplasm and blue-nucleus stained cells) and basophilic cells (purple-stained cells); scale bar = 25 µm. (b) CD4⁺ cells (red, stained by streptABC-PO); scale bar = 100 µm. (c) Interleukin (IL)-5⁺ cells [red, stained by streptavidin–biotin peroxidase detection system (streptABC-PO)]; scale bar = 100 µm. (d) IL-4⁺ cells (pink, stained by ABC-AP); scale bar = 62·5 µm.

Figure 5

Bone marrow eosinophil/basophil colony-forming units (Eo/Baso-CFU) in murine allergic rhinitis. Dose–response curves of Eo/Baso-CFU growth from bone marrow in ovalbumin (OVA)-sensitized (OVA-2w i.n. OVA group, i.e. mice in which OVA challenge was given intranasally from day 22 to day 35 after sensitization from day 1 to day 21) or non-sensitized (Sham-Sham group, i.e. mice treated with diluent, during both sensitization and challenge, instead of with OVA) mice using a range of mouse recombinant cytokines (n = 8 each for each point): (a) Interleukin (IL)-5; (b) IL-3; and (c) granulocyte–macrophage colony-stimulating factor (GM-CSF). The closed circle represents the result from OVA-2w i.n. OVA group and the closed triangle represents that from Sham-Sham group (mean±SE). *P < 0·05 when compared to the Sham-Sham group.

Figure 6

Results of a 24-h kinetic study of nasal mucosa and bone marrow. (a) Number of CD4⁺ cells in nasal mucosa. (b) Number of eosinophils in nasal mucosa. (c) Number of CD34⁺ cells in sternal bone marrow. (d) Number of eosinophils in sternal bone marrow. Each x-axis depicts certain time-points after ovalbumin (OVA) challenge. Pre, prechallenge. Each y-axis depicts positive cell counts in nasal mucosa or in bone marrow. *P < 0·05 compared with the prechallenge value.