TNFalpha-induced GM-CSF release from human airway smooth muscle cells depends on activation of an ET-1 autoregulatory positive feedback mechanism.
BACKGROUND
There is an urgent need to inhibit endothelin-1 (ET-1) induced chronic inflammatory processes in early stages of lung diseases in order to prevent untreatable irreversible stages often accompanied by lung fibrosis and pulmonary hypertension. Nothing is known about the airway inflammation-inducing and/or maintaining role of ET-1 in human airway smooth muscle cells (HASMCs).


OBJECTIVE
ET-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in response to tumour necrosis factor alpha (TNFalpha) and ET-1 stimulation was investigated, and the impact of mitogen-activated protein kinase (MAPK) pathways in this context was studied. To elucidate the anti-inflammatory properties of the dual endothelin receptor antagonist bosentan that targets both endothelin receptor subtypes A (ET(A)R) and B (ET(B)R), its effect on the TNFalpha/ET-1/GM-CSF network was investigated.


METHODS
ET-1 and GM-CSF expression and activation of MAPKs were investigated via quantitative reverse transcription-PCR (RT-PCR), western blotting and ELISA.


RESULTS
Both TNFalpha and ET-1 activated p38(MAPK) and extracellular signal-regulated kinase (ERK)-1/-2 signalling. ET-1 expression was induced by TNFalpha and by ET-1 itself. Both effects were inhibited by bosentan and by specific ET(A)R or p38(MAPK) blockade. ET-1- and TNFalpha-induced GM-CSF expression were both reduced by bosentan as well as by specific inhibition of either ET(A)R, ET(B)R, p38(MAPK) or ERK-1/-2.


CONCLUSIONS
TNFalpha activates an ET(A)R- and p38(MAPK)-dependent ET-1 autoregulatory positive feedback loop to maintain GM-CSF release from HASMCs. Since bosentan impairs ET-1 autoregulation and TNFalpha-induced ET-1 release, as well as TNFalpha- and ET-1-induced GM-CSF release, the present data suggest therapeutic utility for bosentan in treating particularly the early stages of chronic inflammatory airway diseases.
Department of Pneumology, Clinic III for Internal Medicine, University of Cologne, Kerpener Str. 62, D-50937 Cologne, Germany.
J
J
Knobloch
H
H
Peters
D
D
Jungck
K
K
Müller
J
J
Strauch
A
A
Koch
D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D044022:Receptor, Endothelin A / Q000502:physiology; D044023:Receptor, Endothelin B / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
D019332:Endothelin-1; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D014409:Tumor Necrosis Factor-alpha; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases