cAMP-dependent protein kinase activation decreases cytokine release in bronchial epithelial cells

• Published in: American journal of physiology. Lung cellular and molecular physiology 2014-10, Vol.307 (8), p.L643-L651
• Main Authors: Wyatt, Todd A, Poole, Jill A, Nordgren, Tara M, DeVasure, Jane M, Heires, Art J, Bailey, Kristina L, Romberger, Debra J
• Format: Article
• Language: English
• Subjects: 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Acetylcysteine - analogs & derivatives; Acetylcysteine - metabolism; ADAM Proteins - metabolism; ADAM17 Protein; Animal Feed; Animals; Bronchi - drug effects; Bronchi - immunology; Bronchi - metabolism; Cell adhesion & migration; Cells, Cultured; Cyclic AMP-Dependent Protein Kinases - metabolism; Cytokines; Dust; Enzyme-Linked Immunosorbent Assay; Erythromycin - analogs & derivatives; Erythromycin - metabolism; Humans; Interleukin-6 - metabolism; Interleukin-8 - metabolism; Kinases; Lung diseases; Mice; Mice, Inbred C57BL; Protein Kinase C-epsilon - metabolism; Rodents; Swine; Tumor Necrosis Factor-alpha - metabolism
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00373.2013

Lung injury caused by inhalation of dust from swine-concentrated animal-feeding operations (CAFO) involves the release of inflammatory cytokine interleukin 8 (IL-8), which is mediated by protein kinase C-ε (PKC-ε) in airway epithelial cells. Once activated by CAFO dust, PKC-ε is responsible for slowing cilia beating and reducing cell migration for wound repair. Conversely, the cAMP-dependent protein kinase (PKA) stimulates contrasting effects, such as increased cilia beating and an acceleration of cell migration for wound repair. We hypothesized that a bidirectional mechanism involving PKA and PKC regulates epithelial airway inflammatory responses. To test this hypothesis, primary human bronchial epithelial cells and BEAS-2B cells were treated with hog dust extract (HDE) in the presence or absence of cAMP. PKC-ε activity was significantly reduced in cells that were pretreated for 1 h with 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) before exposure to HDE (P < 0.05). HDE-induced IL-6, and IL-8 release was significantly lower in cells that were pretreated with 8-Br-cAMP (P < 0.05). To exclude exchange protein activated by cAMP (EPAC) involvement, cells were pretreated with either 8-Br-cAMP or 8-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8-CPT-2Me-cAMP) (EPAC agonist). 8-CPT-2Me-cAMP did not activate PKA and did not reduce HDE-stimulated IL-6 release. In contrast, 8-Br-cAMP decreased HDE-stimulated tumor necrosis factor (TNF)-α-converting enzyme (TACE; ADAM-17) activity and subsequent TNF-α release (P < 0.001). 8-Br-cAMP also blocked HDE-stimulated IL-6 and keratinocyte-derived chemokine release in precision-cut mouse lung slices (P < 0.05). These data show bidirectional regulation of PKC-ε via a PKA-mediated inhibition of TACE activity resulting in reduced PKC-ε-mediated release of IL-6 and IL-8.