Anti-inflammatory role of the cAMP effectors Epac and PKA: implications in chronic obstructive pulmonary disease

PLoS One. 2012;7(2):e31574. doi: 10.1371/journal.pone.0031574. Epub 2012 Feb 21.

Abstract

Cigarette smoke-induced release of pro-inflammatory cytokines including interleukin-8 (IL-8) from inflammatory as well as structural cells in the airways, including airway smooth muscle (ASM) cells, may contribute to the development of chronic obstructive pulmonary disease (COPD). Despite the wide use of pharmacological treatment aimed at increasing intracellular levels of the endogenous suppressor cyclic AMP (cAMP), little is known about its exact mechanism of action. We report here that next to the β(2)-agonist fenoterol, direct and specific activation of either exchange protein directly activated by cAMP (Epac) or protein kinase A (PKA) reduced cigarette smoke extract (CSE)-induced IL-8 mRNA expression and protein release by human ASM cells. CSE-induced IκBα-degradation and p65 nuclear translocation, processes that were primarily reversed by Epac activation. Further, CSE increased extracellular signal-regulated kinase (ERK) phosphorylation, which was selectively reduced by PKA activation. CSE decreased Epac1 expression, but did not affect Epac2 and PKA expression. Importantly, Epac1 expression was also reduced in lung tissue from COPD patients. In conclusion, Epac and PKA decrease CSE-induced IL-8 release by human ASM cells via inhibition of NF-κB and ERK, respectively, pointing at these cAMP effectors as potential targets for anti-inflammatory therapy in COPD. However, cigarette smoke exposure may reduce anti-inflammatory effects of cAMP elevating agents via down-regulation of Epac1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anti-Inflammatory Agents / metabolism*
  • Bronchi / pathology
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Cyclic AMP / analogs & derivatives
  • Cyclic AMP / metabolism*
  • Cyclic AMP / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / genetics
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Female
  • Fenoterol / pharmacology
  • Gene Knockdown Techniques
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • I-kappa B Proteins / metabolism
  • Interleukin-8 / genetics
  • Interleukin-8 / metabolism
  • Male
  • Middle Aged
  • Myocytes, Smooth Muscle / metabolism
  • NF-KappaB Inhibitor alpha
  • Phosphorylation / drug effects
  • Protein Transport / drug effects
  • Pulmonary Disease, Chronic Obstructive / enzymology*
  • Pulmonary Disease, Chronic Obstructive / genetics
  • Pulmonary Disease, Chronic Obstructive / pathology
  • Signal Transduction / drug effects
  • Smoking
  • Transcription Factor RelA / metabolism

Substances

  • Anti-Inflammatory Agents
  • Guanine Nucleotide Exchange Factors
  • I-kappa B Proteins
  • Interleukin-8
  • NFKBIA protein, human
  • RAPGEF3 protein, human
  • RAPGEF4 protein, human
  • Transcription Factor RelA
  • NF-KappaB Inhibitor alpha
  • Fenoterol
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Extracellular Signal-Regulated MAP Kinases