The H1 histamine receptor regulates allergic lung responses

Abstract

Histamine, signaling via the type 1 receptor (H1R), has been shown to suppress Th2 cytokine production by in vitro cultured T cells. We examined the role of H1R in allergic inflammation in vivo using a murine asthma model. Allergen-stimulated splenic T cells from sensitized H1R-/- mice exhibited enhanced Th2 cytokine production. Despite this Th2 bias, allergen-challenged H1R-/- mice exhibited diminished lung Th2 cytokine mRNA levels, airway inflammation, goblet cell metaplasia, and airway hyperresponsiveness (AHR). Restoration of pulmonary Th2 cytokines in H1R-/- mice by intranasal IL-4 or IL-13 restored inflammatory lung responses and AHR. Further investigation revealed that histamine acts as a T cell chemotactic factor and defective T cell trafficking was responsible for the absence of lung inflammation. Cultured T cells migrated in response to histamine in vitro, but this was ablated by blockade of H1R but not H2R. In vivo, allergen-specific WT but not H1R-/- CD4+ T cells were recruited to the lungs of naive recipients following inhaled allergen challenge. H1R-/- T cells failed to confer airway inflammation or AHR observed after transfer of WT T cells. Our data establish a role for histamine and H1R in promoting the migration of Th2 cells into sites of allergen exposure.

Figure 1. H1R^–/– mice do not develop inflammatory airway responses to antigen.

OVA-immunized (OVA) or sham-immunized (Sal) WT or H1R^–/– mice were exposed to OVA by inhalation and studied for inflammatory airway changes. (A) The cellular composition of the BAL fluid was determined. Data represent mean ± SEM. n = 9–10 individuals. **P < 0.01 by Student’s t test. (B) Representative histological sections stained with H&E or PAS at ×200 magnification.

Figure 2. Hyperproduction of Th2 cytokines by splenocytes from H1R^–/– mice.

Splenocytes were stimulated for 72 hours in the presence of antigen (OVA). Cytokine secretion was determined by sandwich ELISA. Data represent mean ± SEM from 4 individuals per group. **P < 0.01 by Student’s t test, compared with WT OVA values.

Figure 3. IL-4 and IL-13 induce airway inflammation in H1R^–/– mice.

Five micrograms of recombinant mouse IL-4 or IL-13 or 5 μg BSA was administered intranasally for 3 days, and inflammation was determined. Each group consisted of 5 mice. (A) The numbers of eosinophils, neutrophils, and lymphocytes in the BAL fluid. (B) Representative airway histology in WT and H1R^–/– lung tissue. Sections were examined at ×200.

Figure 4. OVA-specific T cells migrate toward histamine via an H1R-dependent process.

Chemotaxis to histamine was investigated using the OVA-specific DO11.10 T cell hybridoma. (A) DO11.10 cells migrate in response to histamine. Cells were added to the upper chamber of Transwell chambers, and histamine was added to the lower chamber. After 4 hours, the number of cells in the lower chamber was determined by FACS. (B) Diphenhydramine (DPH), an H1R antagonist; ranitidine (RAN), an H2R antagonist; and thioperamide (THIOP), an H3R/H4R antagonist, were added to assess their effects on T cell chemotaxis induced by histamine (100 μM). Data represent the number of cells moving through Transwell chambers (mean cells ± SEM) from 3 separate experiments. **P < 0.01 by Student’s t test.

Figure 5. Inflammatory airway responses to antigen can be induced by WT T cells but not by H1R^–/– T cells.

Antigen-expanded CD4⁺ T cells from WT or H1R^–/– mice were adoptively transferred into naive WT or H1R^–/– recipients, and the development of airway inflammation was studied after inhaled OVA challenge. (A) The numbers of eosinophils, neutrophils, and lymphocytes in BAL fluid were determined (n = 9/group). **P < 0.01, Student’s t test. (B) Representative lung histology at ×200 magnification. Sections were stained with H&E.

Figure 6. H1R^–/– T cells do not migrate into the lung following antigen challenge.

Thy1 congenic antigen-expanded CD4⁺ T cells (A) or CD3⁺ T cells (B) from WT or H1R^–/– mice were adoptively transferred into naive WT or H1R^–/– recipients. Cells were adoptively transferred into naive recipients and their movement into spleen, whole lung tissue, and BAL fluid studied. Single-cell suspensions were stained using FITC-Thy1.1 or FITC-Thy1.2 (see Methods) and PE-CD4 or PE-CD8 to determine the presence of the transferred cells. The plots shown were obtained by analysis of the pooled cells of 5 animals of each group and represent 3 individual experiments.