P38 MAPK and glucocorticoid receptor crosstalk in bronchial epithelial cells

Rosie Gaskell,Dave Singh,Jian Li,Kate Gaffey,Chris Harbron,Sarah Mason,Simon Lea,Jonathan Plumb

doi:10.1007/s00109-020-01873-3

Abstract

p38 MAPK inhibition may have additive and synergistic anti-inflammatory effects when used with corticosteroids. We investigated crosstalk between p38 MAPK inhibitors and corticosteroids in bronchial epithelial cells to investigate synergistic effects on cytokine production and the molecular mechanisms involved. Effects of the p38 MAPK inhibitor BIRB-796 and dexamethasone alone and in combination on LPS, polyI:C or TNFα -induced IL-6, CXCL8 and RANTES were assessed in 16HBEs (human epithelial cell line) and on TNFα-induced IL-6 and CXCL8 in primary human epithelial cells from asthma patients and healthy controls. 16HBEs were used to assess effects of BIRB-796 alone and in combination with dexamethasone on glucocorticoid receptor (GR) activity by reporter gene assay, expression of GR target genes and nuclear localisation using Western blot. The effects of BIRB-796 on TNFα stimulated phosphorylation of p38 MAPK and GR at serine (S) 226 by Western blot. Epithelial levels of phosphorylated p38 MAPK and GR S226 were determined by immunohistochemistry in bronchial biopsies from asthma patients and healthy controls. BIRB-796 in combination with dexamethasone increased inhibition of cytokine production in a synergistic manner. Combination treatment significantly increased GR nuclear localisation compared to dexamethasone alone. BIRB-796 inhibited TNFα-induced p38 MAPK and GR S226 phosphorylation. Phosphorylated GR S226 and p38 MAPK levels were increased in bronchial epithelium of more severe asthma patients. Molecular crosstalk exists between p38 MAPK activation and GR function in human bronchial epithelial cells, which alters GR activity. Combining a p38 MAPK inhibitor and a corticosteroid may demonstrate therapeutic potential in severe asthma.Key messages• Combination of corticosteroid and p38 inhibitor in human bronchial epithelial cells• Combination increased cytokine inhibition synergistically and nuclear GR• p38 MAPK inhibition reduced TNFα-induced phosphorylation of GR at S226 but not S211• Phosphorylated GRS226 and p38 is increased in bronchial epithelium in severe asthma• Combining a p38 inhibitor and a corticosteroid may be effective in asthma treatment

Highlights

Inhaled corticosteroids (ICS) are the mainstay of antiinflammatory treatment for asthma
LPS, polycytidylic acid (poly I):C- and TNFαstimulated cytokine secretion was significantly reduced by dexamethasone or BIRB-796 in a concentration-dependent manner (Fig. S3)
Using BIRB-796 in combination with dexamethasone generally provided greater inhibition of LPS, poly I:C- or TNFαinduced cytokine production compared with either drug alone

Summary

Introduction

Inhaled corticosteroids (ICS) are the mainstay of antiinflammatory treatment for asthma. There are numerous phosphorylation sites within the GR Nterminus, changes in which can lead to the alterations of GR function through ligand binding, nuclear localisation, modulating interactions with co-regulators or transcriptional activation [3, 4]. Combining p38 MAPK inhibitors and corticosteroids results in additive anti-inflammatory effects in these cell models, due to the different mechanisms of action [8, 11]. These studies have shown some evidence that the combination effects are more than additive, with a synergistic interaction observed [8, 11]

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