Increased β2-adrenoceptor phosphorylation in airway smooth muscle in severe asthma: possible role of mast cell-derived growth factors.

L Chachi,P Bradding,R Bagadood,A Alzahrani,C Koziol-White,R A Panettieri,M Biddle,Y Amrani

doi:10.1111/cei.13191

Abstract

The purpose of this study was to investigate whether growth factors produced by activated human lung mast cells (HLMCs) impair β2 -adrenoceptor (β2 -AR) function in human airway smooth muscle (ASM) cells. Protein array analysis confirmed the presence of various growth factors, including transforming growth factor (TGF)-β1, in the supernatants of high-affinity IgE receptor (FcεRI)-activated HLMCs which, when applied to ASM cells, impaired albuterol-induced cyclic adenosine monophosphate (cAMP) production, an effect that was prevented following neutralization of TGF-β1. This blunted β2 -AR response was reproduced by treating ASM cells with TGF-β1 or fibroblast growth factor (FGF)-2, which induced β2 -AR phosphorylation at tyrosine residues Tyr141 and Tyr350 , and significantly reduced the maximal bronchorelaxant responses to isoproterenol in human precision cut lung slices (PCLS). Finally, ASM cells isolated from severe asthmatics displayed constitutive elevated β2 -AR phosphorylation at both Tyr141 and Tyr350 and a reduced relaxant response to albuterol. This study shows for the first time that abnormal β2 -AR phosphorylation/function in ASM cells that is induced rapidly by HLMC-derived growth factors, is present constitutively in cells from severe asthmatics.

Highlights

Studies performed in different cell types have reported that some but not all growth factors can impair cell responsiveness to β2-agonists by phosphorylating β2-AR on several serine or tyrosine residues (Tyr350/354/141), resulting in receptor uncoupling and internalisation [3,4,5,6]
Summary The purpose of the study was to investigate whether growth factors produced by activated human lung mast cells (HLMCs) impair β2-adrenoceptor (β2-AR) function in human airway smooth muscle (ASM) cells
Protein array analysis confirmed the presence of various growth factors, including TGFβ1, in the supernatants of FcεRI-activated HLMCs which when applied to ASM cells impaired albuterol-induced cAMP production, an effect that was prevented following neutralisation of TGFβ1

Summary

Introduction

Studies performed in different cell types have reported that some but not all growth factors can impair cell responsiveness to β2-agonists by phosphorylating β2-AR on several serine (ser345/346) or tyrosine residues (Tyr350/354/141), resulting in receptor uncoupling and internalisation [3,4,5,6]. In human lung mast cells (HLMCs), we showed that stem cell factor (SCF) can uncouple β2-AR following receptor phosphorylation at similar Tyr350 residues [7]. We observed that β2-AR responses were suppressed in both mast cells (suppression of FcεR1-induced activation) and ASM cells (inhibition of ASM contraction) following cell-cell contact via β2-AR phosphorylation on Tyr350 residues [8]. Whether mast cells blunt β2-AR responses in ASM cells via the action of secreted different growth factors remains unknown

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