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Corticosteroids and β₂-agonists upregulate mitogen-activated protein kinase phosphatase 1: in vitro mechanisms

M Manetsch1, E E Ramsay, E M King

  • 1Respiratory Research Group, Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia.

British Journal of Pharmacology
|March 1, 2012
PubMed
Abstract

Insights

Corticosteroids and formoterol upregulate MAPK phosphatase 1 (MKP-1) in airway smooth muscle by increasing its transcription. This provides insights into optimizing therapies for airway inflammation and remodeling.

Area of Science:

  • Pulmonary Medicine
  • Molecular Biology
  • Pharmacology

Background:

  • Airway remodeling results from chronic inflammation, with mitogen-activated protein kinases (MAPKs) driving pro-inflammatory pathways.
  • MAPK phosphatase 1 (MKP-1) is a crucial endogenous inhibitor of MAPK-activated inflammatory signaling in the airway.

Purpose of the Study:

  • To investigate the molecular mechanisms by which dexamethasone and formoterol upregulate MKP-1 expression in airway smooth muscle (ASM).
  • To elucidate the roles of protein kinase A (PKA) and transcriptional regulation in mediating these effects.

Main Methods:

  • Investigated MKP-1 expression in ASM cells treated with dexamethasone and formoterol, alone and in combination.
  • Utilized PKIα (a PKA inhibitor) to assess PKA's role in β₂-agonist-induced MKP-1 upregulation.
  • Analyzed MKP-1 promoter activity and mRNA stability using reporter assays and actinomycin D chase experiments.

Main Results:

  • MKP-1 is a corticosteroid-inducible gene, with expression enhanced additively by long-acting β₂-agonists like formoterol.
  • Formoterol upregulates MKP-1 via the β₂-adrenoceptor, mediated by PKA signaling.
  • Dexamethasone increases MKP-1 transcription through a specific corticosteroid-responsive element in the promoter; mRNA stability is not affected.

Conclusions:

  • Dexamethasone and formoterol primarily enhance MKP-1 expression through additive transcriptional upregulation in ASM.
  • Understanding these regulatory mechanisms is key to developing improved corticosteroid-sparing therapies for airway diseases.
  • This research deepens the understanding of MKP-1 regulation by common asthma medications.

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