Galectin-9 in allergic airway inflammation and hyper-responsiveness in mice

Galectin-9 (Gal-9) is a member of the growing family of beta-galactoside-binding lectins. Gal-9 is an eosinophil chemoattractant and inducer of Th1 cell apoptosis. These effects suggest its potential role in the pathogenesis of asthma. Our aim was to study the expression of Gal-9 in an ovalbumin (OVA)-induced mouse model of allergic asthma.

To investigate the significance of Gal-9 in allergic inflammation and airway hyperresponsiveness (AHR), a group of BALB/c mice was sensitized and challenged with OVA (G(OVA)). Another group of animals was allergized with OVA and also treated with dexamethasone (DEX) (G(OVA+DEX)). The control group (G(PBS)) received phosphate-buffered saline instead of OVA as placebo. Airway reactivity to intravenous methacholine was assessed.

The percentage of Gal-9-positive cells and their intracellular Gal-9 content and Th1/Th2 cytokine levels in the bronchoalveolar lavage (BAL) were determined by flow cytometry. Gal-9 mRNA expression and protein level were measured in the lung tissue by real-time RT-PCR and Western blot. In G(OVA )mice, airway inflammation and mucus hypersecretion developed. DEX treatment inhibited the main features of experimental asthma. The number of Gal-9-positive lymphocytes, eosinophil and neutrophil granulocytes and the levels of Th2 cytokines were higher in the BAL of G(OVA) compared to G(PBS) or G(OVA+DEX )mice. Moreover, Gal-9 protein level was elevated in the lungs of G(OVA) mice.

These results suggest that Gal-9 plays a role as a mediator contributing to the development of allergic airway inflammation. Gal-9 may serve as a recruiter of eosinophil granulocytes and promoter of Th2 dominance.