S76 Role of galectin-3 in the development of idiopathic pulmonary fibrosis

IntroductionIdiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease with a poor prognosis. Activation of the profibrotic cytokine transforming growth factor ß (TGFß) is crucial in IPF development. It has been shown that the ß-galactoside binding lectin galectin-3 can promote fibrosis through altering cellular responses to TGFß.1 However, the precise mechanism of this is currently unknown.MethodsImmunohistochemistry (IHC) staining for galectin-3 in lung sections from patients with IPF and mice treated with 28 day of saline or bleomycin. Transformed mink lung epithelial cells (TMLCs) which stably express firefly luciferase at the plasminogen activator inhibitor-1 promotor region were used as a measure of TGFß activity. TMLCs were treated with increasing concentrations of recombinant human galectin-3 (rhGal-3) and luciferase activity was measured. Human lung fibroblasts (HLFs) isolated from control patients (non-IPF) and patients with IPF, and immortalised human bronchial epithelial cells (IHBECs) were treated with 50 µM TGFß receptor type 1 inhibitor (Alk5 inhibitor), or 1 µM galectin-3 inhibitor TD139 (currently in clinical trials for IPF treatment) and 10 µg/ml rhGal-3. Mouse embryonic fibroblasts expressing the integrin avß6 (MEFß6), HLFs, and IHBECs were treated with 1 µM TD139 and 2 ng/ml TGFß. Protein expression of phosphorylated Smad2 (pSmad2) and total Smad2 were assessed by western blot. qPCR was used to measure galectin-3 at the mRNA level in HLFs treated with 2 ng/ml TGFß.ResultsIHC showed that galectin-3 is increased in patients with IPF and in the bleomycin mouse model; where expression is increased in airway epithelial cells, fibroblasts, and macrophages. Treatment with rhGal-3 increased TGFß activity in TMLCs, and significantly increased levels of pSmad2 in HLFs but not IHBECs which was inhibited by the Alk5 inhibitor and TD139. Treatment with the galectin-3 inhibitor TD139 significantly inhibited TGFß dependent Smad2 phosphorylation in MEFß6 and HLFs but not in IHBECs. TGFß stimulation significantly increased galectin-3 expression at the mRNA level in IPF HLFs but not control HLFs.ConclusionGalectin-3 is involved in TGFß signalling where it can promote TGFß activation and activity in fibroblasts. Results indicate the presence of a TGFß-galectin-3 positive feedback loop (figure 1). Thus galectin-3 can potentially be a therapeutic target for IPF treatment.ReferencesPartridge EA. Regulation of cytokine receptors by Golgi N-