The translational repressor T-cell intracellular antigen-1 (TIA-1) is a key modulator of Th2 and Th17 responses driving pulmonary inflammation induced by exposure to house dust mite

Abstract

T-cell intracellular antigen-1 (TIA-1) is a translational repressor that dampens the production of proinflammatory cytokines and enzymes. In this study we investigated the role of TIA-1 in a mouse model of pulmonary inflammation induced by exposure to the allergenic extract (Df) of the house dust mite Dermatophagoides farinae. When intranasally challenged with a low dose of Df, mice lacking TIA-1 protein (Tia-1(-/-)) showed more severe airway and tissue eosinophilia, infiltration of lung bronchovascular bundles, and goblet cell metaplasia than wild-type littermates. Tia-1(-/-) mice also had higher levels of Df-specific IgE and IgG(1) in serum and ex vivo restimulated Tia-1(-/-) lymph node cells and splenocytes transcribed and released more Th2/Th17 cytokines. To evaluate the site of action of TIA-1, we studied the response to Df in bone marrow chimeras. These experiments revealed that TIA-1 acts on both hematopoietic and non-hematopoietic cells to dampen pulmonary inflammation. Our results identify TIA-1 as a negative regulator of allergen-mediated pulmonary inflammation in vivo. Thus, TIA-1 might be an important player in the pathogenesis of bronchial asthma.

Fig. 1. Df-induced airway inflammation in WT and Tia-1^−/− mice

WT and Tia-1^−/− mice were exposed to six doses of NaCl or Df 1 μg intranasally over three weeks. Twenty-four hours after the last treatment mice were euthanized and bronchoalveolar lavage (BAL) was performed. Cells from the BAL were separated from the fluid, counted, cytocentrifuged onto slides and stained with Diff-Quick. (A) Total and (B) subpopulation differential cell counts from BAL of WT (■; n = 22 for NaCl-treated group and n = 54 for Df-treated group) and Tia-1^−/− (□; n = 22 for NaCl-treated group and n = 65 for Df-treated group) mice. Data are combined from seven independent experiments. Values are mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 2. Df-induced lung inflammation in WT and Tia-1^−/− mice

(A) Lung sections showing bronchovascular bundles (BVBs) from mice treated with NaCl (WT: a, e; Tia-1^−/−: b, f) or Df (WT: c, g; Tia-1^−/−: d, h) 24 h after the last intranasal challenge were stained by the chloroacetate esterase reaction (CAE, a–d) to assess inflammatory cell infiltrates or by the periodic acid Schiff reaction (PAS, e–h) to depict mucus-secreting cells (arrows). (B) Lung sections of Df-treated WT (a) and Tia-1^−/− (b) mice stained by Congo red dye to demonstrate accumulation of eosinophils (arrows) in BVBs. Pictures are from one representative mouse per strain and treatment from five separate experiments. Original magnifications, x20 (A) and x40 (B). (C) Quantitative analysis of pulmonary inflammation. The extent of cellular infiltration, on a total of 15 BVBs, and of goblet cell metaplasia, measured as the numbers of PAS- positive goblet cells per mm of bronchial basal lamina, was determined on glycolmethacrylate-embedded lung sections from WT (■; n = 39) and Tia-1^−/− (□; n = 46) mice exposed to Df. Data are combined from five independent experiments. Values are mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 3. Parabronchial lymph node cellularity and cytokine generation from in vitro restimulated WT and Tia-1^−/− parabronchial lymph node cells and splenocytes

Parabronchial lymph node cells and splenocytes were isolated from NaCl- and Df-treated WT and Tia-1^−/− mice and incubated in vitro with Df, as described in Methods. At the end of the incubation the indicated cytokines were measured in the supernatants by ELISA. Cytokine release from Df-restimulated (A) splenocytes and (B) parabronchial lymph node cells of WT (■) and Tia-1^−/− (□) mice exposed to Df. Data are combined from five (splenocytes) or three (lymph node cells) independent experiments. Values are mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 4. Levels of Df-specific IgE and Df-specific IgG₁ in serum of WT and Tia-1^−/− mice

Df-specific IgE (A) and Df-specific IgG₁ (B) in serum of wild-type mice (■) and Tia-1^−/− (□) mice 24 h after the last intranasal instillation were measured by ELISA. Data are combined from six (Df-specific IgE) and seven (Df-specific IgG₁) independent experiments. Values represent the mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 5. Df-induced pulmonary inflammation and immunologic response in WT/Tia-1^−/− bone marrow chimeras

WT and Tia-1^−/− mice were irradiated and reconstituted with bone marrow from sex-matched WT and Tia-1^−/− mice in order to generate four groups of chimeras: WT + WT BM, WT + Tia-1^−/− BM, Tia-1^−/− + WT BM, and Tia-1^−/− + Tia-1^−/− BM. Mice were then exposed to six doses of NaCl 0.9% or Df 1 μg intranasally and euthanized 24 h after the last administration. (A) Total and (B) subpopulation differential cell counts from BAL of chimeras reconstituted with WT (n = 14 for WT recipients and n = 11 for Tia-1^−/− recipients) and Tia-1^−/− (n = 16 for WT recipients and n = 14 Tia-1^−/− recipients) bone marrow. Data are combined from three independent experiments. Values are mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.