S34 The adhesion receptor CADM1 on mast cells mediates adhesion to lung fibroblasts and smooth muscle

Lipoxin A4 Attenuates Constitutive and TGF-β1-Dependent Profibrotic Activity in Human Lung Myofibroblasts

Idiopathic pulmonary fibrosis (IPF) is a common, progressive, and invariably lethal interstitial lung disease with no effective therapy. The key cell driving the development of fibrosis is the myofibroblast. Lipoxin A₄ (LXA₄) is an anti-inflammatory lipid, important in the resolution of inflammation, and it has potential antifibrotic activity. However, the effects of LXA₄ on primary human lung myofibroblasts (HLMFs) have not previously been investigated. Therefore, the aim of this study was to examine the effects of LXA₄ on TGF-β1–dependent responses in IPF- and nonfibrotic control (NFC)–derived HLMFs. HLMFs were isolated from IPF and NFC patients and grown in vitro. The effects of LXA₄ on HLMF proliferation, collagen secretion, α-smooth muscle actin (αSMA) expression, and Smad2/3 activation were examined constitutively and following TGF-β1 stimulation. The LXA₄ receptor (ALXR) was expressed in both NFC- and IPF-derived HLMFs. LXA₄ (10⁻¹⁰ and 10⁻⁸ mol) reduced constitutive αSMA expression, actin stress fiber formation, contraction, and nuclear Smad2/3, indicating regression from a myofibroblast to fibroblast phenotype. LXA₄ also significantly inhibited FBS-dependent proliferation and TGF-β1–dependent collagen secretion, αSMA expression, and Smad2/3 nuclear translocation in IPF-derived HLMFs. LXA₄ did not inhibit Smad2/3 phosphorylation. In summary, LXA₄ attenuated profibrotic HLMF activity and promoted HLMF regression to a quiescent fibroblast phenotype. LXA₄ or its stable analogs delivered by aerosol may offer a novel approach to the treatment of IPF.