Deficiency of endothelial heparan sulfates attenuates allergic airway inflammation.

The effect of targeted inactivation of the gene encoding N-deacetylase/N-sulfotransferase-1 (Ndst1), a key enzyme involved in the biosynthesis of heparan sulfate (HS) chains, on the inflammatory response associated with allergic inflammation in a murine model of OVA-induced acute airway inflammation was investigated. OVA-exposed Ndst1(f/f)TekCre(+) (mutant) mice deficient in endothelial and leukocyte Ndst1 demonstrated significantly decreased allergen-induced airway hyperresponsiveness and inflammation characterized by a significant reduction in airway recruitment of inflammatory cells (eosinophils, macrophages, neutrophils, and lymphocytes), diminished IL-5, IL-2, TGF-beta1, and eotaxin levels, as well as decreased expression of TGF-beta1 and the angiogenic protein FIZZ1 (found in inflammatory zone 1) in lung tissue compared with OVA-exposed Ndst1(f/f)TekCre(-) wild-type littermates. Furthermore, murine eosinophils demonstrated significantly decreased rolling on lung endothelial cells (ECs) from mutant mice compared with wild-type ECs under conditions of flow in vitro. Treatment of wild-type ECs, but not eosinophils, with anti-HS Abs significantly inhibited eosinophil rolling, mimicking that observed with Ndst1-deficient ECs. In vivo, trafficking of circulating leukocytes in lung microvessels of allergen-challenged Ndst1-deficient mice was significantly lower than that observed in corresponding WT littermates. Endothelial-expressed HS plays an important role in allergic airway inflammation through the regulation of recruitment of inflammatory cells to the airways by mediating interaction of leukocytes with the vascular endothelium. Furthermore, HS may also participate by sequestering and modulating the activity of allergic asthma-relevant mediators such as IL-5, IL-2, and TGF-beta1.

Induction and effector phase of allergic lung inflammation is independent of CCL21/CCL19 and LT-beta.

The chemokines CCL21 and CCL19, and cell bound TNF family ligand lymphotoxin beta (LTbeta), have been associated with numerous chronic inflammatory diseases. A general role in chronic inflammatory diseases cannot be assumed however; in the case of allergic inflammatory disease, CCL21/CCL19 and LTbeta have not been associated with the induction, recruitment, or effector function of Th2 cells nor dendritic cells to the lung. We have examined the induction of allergic inflammatory lung disease in mice deficient in CCL21/CCL19 or LTbeta and found that both kinds of mice can develop allergic lung inflammation. To control for effects of priming differences in knockout mice, adoptive transfers of Th2 cells were also performed, and they showed that such effector cells had equivalent effects on airway hyper-responsiveness in both knockout background recipients. Moreover, class II positive antigen presenting cells (B cells and CD11c+ dendritic cells) showed normal recruitment to the peribronchial spaces along with CD4 T cells. Thus, the induction of allergic responses and recruitment of both effector Th2 cells and antigen presenting cells to lung peribronchial spaces can develop independently of CCL21/CCL19 and LTbeta.

Galectin-3 functions as an adhesion molecule to support eosinophil rolling and adhesion under conditions of flow.

Allergic inflammation involves the mobilization and trafficking of eosinophils to sites of inflammation. Galectin-3 (Gal-3) has been shown to play a critical role in eosinophil recruitment and airway allergic inflammation in vivo. The role played by Gal-3 in human eosinophil trafficking was investigated. Eosinophils from allergic donors expressed elevated levels of Gal-3 and demonstrated significantly increased rolling and firm adhesion on immobilized VCAM-1 and, more surprisingly, on Gal-3 under conditions of flow. Inhibition studies with specific mAbs as well as lactose demonstrated that: 1) eosinophil-expressed Gal-3 mediates rolling and adhesion on VCAM-1; 2) alpha(4) integrin mediates eosinophil rolling on immobilized Gal-3; and 3) eosinophil-expressed Gal-3 interacts with immobilized Gal-3 through the carbohydrate recognition domain of Gal-3 during eosinophil trafficking. These findings were further confirmed using inflamed endothelial cells. Interestingly, Gal-3 was found to bind to alpha(4) integrin by ELISA, and the two molecules exhibited colocalized expression on the cell surface of eosinophils from allergic donors. These findings suggest that Gal-3 functions as a cell surface adhesion molecule to support eosinophil rolling and adhesion under conditions of flow.

Critical role for galectin-3 in airway inflammation and bronchial hyperresponsiveness in a murine model of asthma.

Galectin-3 is a member of a beta-galactoside-binding animal lectin family. Previous in vitro studies have demonstrated that galectin-3 is involved in a number of activities; however, the roles of this lectin in physiological and pathological processes in vivo remain to be elucidated. Herein, we show, in a murine model of ovalbumin (OVA)-induced asthma that 1) peribronchial inflammatory cells expressed large amounts of galectin-3; 2) bronchoalveolar lavage fluid from OVA-challenged mice contained significantly higher levels of galectin-3 compared to control mice; and 3) macrophages in bronchoalveolar lavage fluid were the major cell type that contained galectin-3. We investigated the role of galectin-3 in the allergic airway response by comparing galectin-3-deficient (gal3(-/-)) mice and wild-type (gal3(+/+)) mice. OVA-sensitized gal3(-/-) mice developed fewer eosinophils and lower goblet cell metaplasia, after airway OVA challenge compared to similarly treated gal3(+/+) mice. In addition, the OVA-sensitized gal3(-/-) mice developed significantly less airway hyperresponsiveness after airway OVA challenge compared to gal3(+/+) mice. Finally, gal3(-/-) mice developed a lower Th2 response, but a higher Th1 response, suggesting that galectin-3 regulates the Th1/Th2 response. We conclude that galectin-3 may play an important role in the pathogenesis of asthma and inhibitors of this lectin may prove useful for treatment of this disease.

IgE-dependent mast cell activation potentiates airway responses in murine asthma models.

We have studied murine models of asthma using FcepsilonRIalpha-chain-deficient (FcepsilonRIalpha(-/-)) mice to investigate the role of IgE-dependent mast cell activation in these models. When mice were either 1) immunized once with OVA in alum i.p. and then challenged with OVA intranasally, or 2) repeatedly immunized with OVA in the absence of adjuvant and subsequently challenged with nebulized OVA, FcepsilonRalpha(-/-) mice had significantly fewer eosinophils and lower IL-4 levels in their bronchoalveolar lavage fluid compared with wild-type mice. When mice were given anti-IL-5 antibody before OVA challenge in protocol 1, eosinophilic infiltration into the airways was significantly suppressed in both genotypes, but only FcepsilonRIalpha(-/-) mice showed significantly reduced airway hyperresponsiveness (AHR). In addition, when mice immunized and challenged with OVA also received a late OVA provocation at a higher concentration and were then exposed to methacholine, only wild-type mice developed a substantial increase in AHR. Since FcepsilonRI is expressed mainly on mast cells in mouse airways, we conclude that IgE-dependent activation of this cell type plays an important role in the development of allergic airway inflammation and AHR in mice. The models used may be of value for testing inhibitors of IgE or mast cells for development of therapeutic agents for human asthma.