Suppression of inflammatory cytokine production by carbon monoxide involves the JNK pathway and AP-1.
The stress-inducible protein heme oxygenase-1 provides protection against oxidative stress and modulates pro-inflammatory cytokines. As the sepsis syndrome results from the release of pro-inflammatory mediators, we postulated that heme oxygenase-1 and its enzymatic product CO would protect against lethality in a murine model of sepsis. Mice treated with a lethal dose of lipopolysaccharide (LPS) and subsequently exposed to inhaled CO had significantly better survival and lower serum interleukin (IL)-6 and IL-1beta levels than their untreated counterparts. In vitro, mouse macrophages exposed to LPS and CO had significantly attenuated IL-6 production; this effect was concentration-dependent and occurred at a transcriptional level. The same effect was seen with increased endogenous CO production through overexpression of heme oxygenase-1. Mutation within the AP-1-binding site in the IL-6 promoter diminished the effect of CO on promoter activity, and treatment of macrophages with CO decreased AP-1 binding in an electrophoretic mobility shift assay. Electrophoretic mobility supershift assay indicated that the JunB, JunD, and c-Fos components of AP-1 were particularly affected. Upstream of AP-1, CO decreased JNK phosphorylation in murine macrophages and lung endothelial cells. Mice deficient in the JNK pathway had decreased serum levels of IL-6 and IL-1beta in response to LPS compared with control mice, and no effect of CO on these cytokine levels was seen in Jnk1 or Jnk2 genedeleted mice. In summary, these results suggest that CO provides protection in a murine model of sepsis through modulation of inflammatory cytokine production. For the first time, the effect of CO is shown to be mediated via the JNK signaling pathway and the transcription factor AP-1.
Morse
Danielle
D
Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
Pischke
Soeren E
SE
Zhou
Zhihong
Z
Davis
Roger J
RJ
Flavell
Richard A
RA
Loop
Torsten
T
Otterbein
Sherrie L
SL
Otterbein
Leo E
LE
Choi
Augustine M K
AM
D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology*; D006419:Heme Oxygenase (Decyclizing) / Q000502:physiology; D051547:Heme Oxygenase-1; D007375:Interleukin-1 / Q000096:biosynthesis*; D015850:Interleukin-6 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000633:toxicity; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D048055:Mitogen-Activated Protein Kinase 8; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000502:physiology*
D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D018808:Transcription Factor AP-1; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D048056:Mitogen-Activated Protein Kinase 9; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases