Granulocyte-macrophage colony-stimulating factor delays neutrophil constitutive apoptosis through phosphoinositide 3-kinase and extracellular signal-regulated kinase pathways.
Activated neutrophils play an important role in the pathogenesis of sepsis, glomerulonephritis, acute renal failure, and other inflammatory processes. The resolution of neutrophil-induced inflammation relies, in large part, on removal of apoptotic neutrophils. Neutrophils are constitutively committed to apoptosis, but inflammatory mediators, such as GM-CSF, slow neutrophil apoptosis by incompletely understood mechanisms. We addressed the hypothesis that GM-CSF delays neutrophil apoptosis by activation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI 3-kinase) pathways. GM-CSF (20 ng/ml) significantly inhibited neutrophil apoptosis (GM-CSF, 32 vs 65% of cells p < 0. 0001). GM-CSF activated the PI 3-kinase/Akt pathway as determined by phosphorylation of Akt and BAD. GM-CSF-dependent Akt and BAD phosphorylation was blocked by the PI 3-kinase inhibitor LY294002. A role for the PI 3-kinase/Akt pathway in GM-CSF-stimulated delay of apoptosis was indicated by the ability of LY294002 to attenuate apoptosis delay. GM-CSF-dependent inhibition of apoptosis was significantly attenuated by PD98059, an ERK pathway inhibitor. LY294002 and PD98059 did not produce additive inhibition of apoptosis delay. To determine whether PI 3-kinase and ERK are used by other ligands that delay neutrophil apoptosis, we examined the role of these pathways in IL-8-induced apoptosis delay. LY294002 blocked IL-8-dependent Akt phosphorylation. PD98059 and LY294002 significantly attenuated IL-8 delay of apoptosis. These results indicate IL-8 and GM-CSF act, in part, to delay neutrophil apoptosis by stimulating PI 3-kinase and ERK-dependent pathways.
Klein
J B
JB
Kidney Disease Program and Department of Biochemistry and Molecular Biology, University of Louisville and Veterans Affairs Medical Center, Louisville, KY 40292, USA. jon.klein@louisville.edu
Rane
M J
MJ
Scherzer
J A
JA
Coxon
P Y
PY
Kettritz
R
R
Mathiesen
J M
JM
Buridi
A
A
McLeish
K R
KR
D017209:Apoptosis / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D016209:Interleukin-8 / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D009025:Morpholines / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D051025:bcl-Associated Death Protein
D002352:Carrier Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D016209:Interleukin-8; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D051025:bcl-Associated Death Protein; C494819:BAD protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one