Mechanisms of corticosteroid insensitivity in COPD alveolar macrophages exposed to NTHiReport as inadecuate

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Respiratory Research

, 18:61

First Online: 18 April 2017Received: 11 January 2017Accepted: 28 March 2017DOI: 10.1186-s12931-017-0539-4

Cite this article as: Khalaf, R.M., Lea, S.R., Metcalfe, H.J. et al. Respir Res 2017 18: 61. doi:10.1186-s12931-017-0539-4


BackgroundNon-typeable Haemophilus influenza NTHi infection is common in COPD. Corticosteroids can have limited therapeutic effects in COPD patients. NTHi causes corticosteroid insensitive cytokine production from COPD alveolar macrophages. We investigated the mechanisms by which NTHi causes corticosteroid insensitive inflammatory responses, and the effects of NTHi exposure on COPD macrophage polarisation.

MethodAlveolar macrophages from COPD patients and controls were exposed to NTHi in conjunction with the corticosteroid dexamethasone and-or the p38 MAPK inhibitor BIRB-796. Cytokine release, GR phosphorylation and modulation and macrophage phenotype were analysed.

ResultsDexamethasone significantly inhibited NTHi induced TNF-α, IL-6 and IL-10 from COPD macrophages but, CXCL8 was not suppressed.

BIRB-796 combined with dexamethasone caused significantly greater inhibition of all cytokines than either drug alone p < 0.05 all comparisons. NTHi caused phosphorylation of GR S226 reducing GR nuclear localisation, an effect regulated by p38 MAPK. NTHi altered macrophage polarisation by increasing IL-10 and decreasing CD36, CD206, CD163 and HLA-DR.

ConclusionNTHi exposure causes p38 MAPK dependent GR phosphorylation associated with decreased GR function in COPD alveolar macrophages. Combining a p38 MAPK inhibitor with corticosteroids can enhance anti-inflammatory effects during NTHi exposure of COPD alveolar macrophages. NTHi causes macrophage polarisation that favours bacterial persistence.

Electronic supplementary materialThe online version of this article doi:10.1186-s12931-017-0539-4 contains supplementary material, which is available to authorized users.

Author: Rana M. Khalaf - Simon R. Lea - Hannah J. Metcalfe - Dave Singh


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