Restoration of Corticosteroid Sensitivity by p38 Mitogen Activated Protein Kinase Inhibition in Peripheral Blood Mononuclear Cells from Severe Asthma

Abstract

BackgroundSevere asthma accounts for a small number of asthmatics but represents a disproportionate cost to health care systems. The underlying mechanism in severe asthma remains unknown but several mechanisms are likely to be involved because of a very heterogeneous profile. We investigated the effects of a p38MAPK inhibitor in corticosteroid sensitivity in peripheral blood mononuclear cells (PBMCs) from severe asthmatics and the profile of its responders.Methodology/Principal FindingsCorticosteroid sensitivity was determined by measuring dexamethasone inhibition of CD3/28 and TNF-α induced IL-8 production in PBMCs by using ELISA. PBMCs from severe asthmatics were relatively less sensitive to dexamethasone (Dex) as compared to those of non-severe asthmatics and healthy volunteers. The IC50 values of Dex negatively correlated with decreased glucocorticoid receptor (GR) nuclear translocation assessed using immunocytochemistry (r = −0.65; p<0.0005) and with decreased FEV1 (% predicted) (r = 0.6; p<0.0005). A p38α/β inhibitor (SB203580) restored Dex-sensitivity in a subpopulation of severe asthma that was characterized by a defective GR nuclear translocation, clinically by lower FEV1 and higher use of oral prednisolone. We also found that SB203580 partially inhibited GR phosphorylation at serine 226, resulting in increased GR nuclear translocation in IL-2/IL-4 treated corticosteroid insensitive U937s.Conclusions/Significancep38MAPKα/β is involved in defective GR nuclear translocation due to phosphorylation at Ser226 and this will be a useful biomarker to identify responders to p38MAPKα/β inhibitor in the future.

Basal p38 Mitogen-Activated Protein Kinase Regulates Unliganded Glucocorticoid Receptor Function in Airway Smooth Muscle Cells

“…Different groups have shown that GR phosphorylation at S226 is an important inhibitory mechanism of GC function, although some controversy exists regarding the nature of upstream kinases involved (6,14). For example, in some reports, c-Jun N-terminal kinase (JNK) MAPK-induced GR phosphorylation at S226 was found to inhibit GR function (6,12), whereas other studies identified p38 MAPK as another potential kinase regulating phosphorylation of GR at S226 and inhibiting its function (11,23). In contrast to these latter studies, we found that p38 MAPK negatively regulates GR phosphorylation on S211 but had no effect on S226 (Figure 1).…”

“…p38 MAPK is activated by upstream MAPK kinases (MKK3 or MKK6) in response to a number of inflammatory or environmental signals (17)(18)(19). Different reports have convincingly implicated p38 MAPK pathways in the pathogenesis of patients with asthma, in particular those with severe disease (20)(21)(22)(23)(24). The exact role of p38 MAPK in GR functions in human diseases has just started to emerge.…”

“…Earlier studies in immune cells suggested that the p38 MAPK-GR interaction acts as a novel mechanism driving GC resistance in patients with severe asthma (11). Indeed, the blockade of p38 MAPK pathways by soluble inhibitors (20,23) or by the longacting b agonists (LABAs) formoterol and salmeterol (24) was associated with a restoration of cell sensitivity to GC. Those reports identified p38 MAPK as an important kinase in peripheral blood mononuclear cells (PBMCs) that reduces GR functions by impairing GR nuclear translocation and/or DNA binding affinity.…”

New and developing non-adrenoreceptor small molecule drugs for the treatment of asthma

“…Several p38 mitogen-activated protein kinase (MAPK) inhibitors restore corticosteroid sensitivity in peripheral blood mononuclear cells (PBMCs) and alveolar macrophages from patients with severe asthma 63,66 . A phase II trial is registered as investigating the efficacy and safety of the inhaled p38MAPK inhibitor AZD7624 in corticosteroid resistant asthma (ClinicalTrials.gov Identifier: NCT02753764) 33 .…”

Addressing corticosteroid insensitivity in adults with asthma

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Protein kinase inhibitors Inhibition of protein kinase, such as p38MAPK, narrow spectrum kinase and tyrosine kinase, that are involved in cellular signaling of pro-inflammatory cytokines, may have a role in the treatment of severe asthma associated with corticosteroid insensitivity [121][122][123]. Several p38MAPK inhibitors restore corticosteroid sensitivity in PBMCs from patients with severe asthma [121,124] and COPD [125]. Clinical trials of p38MAPK inhibitors, such as oral losmapimod (GW856553) and inhaled AZD7624 are underway in COPD, although none are registered in asthma.…”