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High Mobility Group Box 1 (HMGB1) promotes extracellular matrix synthesis and wound repair in human bronchial epithelial cells

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AJP Lung Cellular and Molecular Physiology

Published online on

Abstract

HMGB1 is a damage associated molecular pattern (DAMP) protein that binds toll-like receptors (e.g. TLR4) and the receptor for advanced glycated end products (RAGE). Direct effects of HMGB1 on airway structural cells are not fully known. As epithelial cell responses are fundamental drivers of asthma, including abnormal repair-restitution linked to changes in extracellular matrix (ECM) synthesis, we tested the hypothesis that HMGB1 promotes bronchial epithelial cell wound repair via TLR4 and/or RAGE signalling that regulates ECM (fibronectin and the 2 chain of laminin-5) and integrin protein abundance. To assess impact of HMGB1 we used molecular and pharmacological inhibitors of RAGE or TLR4 signalling in scratch wound, immunofluorescence and immunoblotting assays to assess wound repair, ECM synthesis and phosphorylation of intracellular signalling. HMGB1 increased wound closure and this effect was attenuated by blocking RAGE and TLR4 signalling. HMGB1 induced fibronectin and laminin-5 (2 chain) was diminished by blocking RAGE and/or blunting TLR4 signalling. Similarly, induction of α3 integrin receptor for fibronectin and laminin-5 was also diminished by blocking TLR4 signalling and RAGE. Lastly, rapid and/or sustained phosphorylation of SMAD2, ERK1/2 and JNK signalling modulated HMGB1 induced wound closure. Our findings suggest a role for HMGB1 in human airway epithelial cell repair and restitution via multiple pathways mediated by TLR4 and RAGE that underpin increased ECM synthesis and modulation of cell-matrix adhesion.