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

Abstract

The purpose of this study was to investigate whether growth factors produced by activated human lung mast cells (HLMCs) impair β -adrenoceptor (β -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 β -AR response was reproduced by treating ASM cells with TGF-β1 or fibroblast growth factor (FGF)-2, which induced β -AR phosphorylation at tyrosine residues Tyr and Tyr , 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 β -AR phosphorylation at both Tyr and Tyr and a reduced relaxant response to albuterol. This study shows for the first time that abnormal β -AR phosphorylation/function in ASM cells that is induced rapidly by HLMC-derived growth factors, is present constitutively in cells from severe asthmatics.

Dexamethasone rescues TGF-β1-mediated β2-adrenergic receptor dysfunction and attenuates phosphodiesterase 4D expression in human airway smooth muscle cells

“…3, we show that TGF-β1 attenuates, rather than augments, grk2 and grk3 expression. Despite our previous findings showing that β 2 AR phosphorylation is increased following TGF-β1 exposure [26], we determined that the increase in TGF-β1induced β 2 AR phosphorylation is not due to increased expression of GRK2/3.…”

“…Despite this limitation, we have shown effects of TGF-β1 on HASM to be recapitulated in small airways derived from human lungs [10]. Additionally, while it would be interesting to study this phenomenon in asthma-derived HASM, we and others have demonstrated that β 2 -agonist-induced cAMP production in these cells is already blunted due partially to increased PDE expression [26,38]. Therefore, exposure of asthma-derived HASM to TGF-β1 will likely have little effect on modulating β 2 -agonist-induced cAMP production.…”

“…Activation of GRK2 and GRK3, members of the GRK (G proteincoupled receptor kinase) family, provide a mechanism by which β 2 AR desensitization occurs. We previously demonstrated that TGF-β1 stimulation induces β 2 AR phosphorylation that is consistent with desensitization of the receptor [26]. To assess a potential role for GRKs in attenuating β 2 -agonist-induced relaxation of HASM, grk2 and grk3 expression were assessed with overnight TGF-β1 treatment.…”

Neuro-immune crosstalk and allergic inflammation

“…However, some studies report that this neuronal regulation is modified by immune cells. Mast cells infiltrate in airway smooth muscles of patients with asthma (68), and mast cell-derived TGF-β induces phosphorylation of β2AR on smooth muscle cells, which results in a reduced response to a β2AR agonist (69). In addition, noradrenaline can directly suppress proinflammatory cytokine production from immune cells through β2AR, and β2AR-deficient mice have more severe type 2 airway inflammation in allergen-nonspecific asthma mouse models.…”

Human Lung Mast Cells Impair Corticosteroid Responsiveness in Human Airway Smooth Muscle Cells

“…Infiltration of mast cells has been described within the epithelium, submucosa layer and airway smooth muscle and has been shown to correlate with disease severity [reviewed in ( 3 )]. Bidirectional interactions between human lung mast cells, and structural airway tissues have been demonstrated using a co-culture model system with mast cells being able to drive pro-asthmatic responses in airway smooth muscle (ASM) cells including loss of β2-adrenoceptor function indirectly via the paracrine action of secreted TGFβ ( 4 ), or following direct cell-cell physical interaction ( 5 , 6 ). Similarly, β2-adrenoceptor dysfunction can also be observed in human lung mast cells as a result of the autocrine action of secreted SCF ( 5 , 7 ).…”