Oxidants inhibit ERK/MAPK and prevent its ability to delay neutrophil apoptosis downstream of mitochondrial changes and at the level of XIAP.
Normal spontaneous apoptosis in neutrophils is enhanced by "stress" stimuli such as tumor necrosis factor-alpha, Fas ligand, and oxidants, and this effect is inhibited by anti-apoptotic stimuli including granulocyte-macrophage colony-stimulating factor, lipopolysaccharide, and formylmethionine-leucine-phenylalanine. In this report we demonstrate that anti-apoptotic stimuli protect neutrophils from stress-induced apoptosis via activation of the ERK/MAPK pathway. The protection occurs downstream of mitochondrial alterations assessed as a decrease in membrane potential concomitant with enhanced cytochrome c release. ERK activation was shown to inhibit apoptosis by maintaining levels of XIAP, which is normally decreased in the presence of the pro-apoptotic/stress stimuli. This report also demonstrates that potent intra- and extracellular oxidants inhibit the protective effect of ERK. Oxidant-dependent inhibition of ERK was because of activation of p38 MAPK and activation of the protein phosphatases PP1 and PP2A. Our data suggest that ERK suppresses stress-induced apoptosis downstream of mitochondrial alterations by maintaining XIAP levels and that oxidants block this effect through activation of p38 and protein phosphatases.
Gardai
Shyra J
SJ
Program in Cell Biology, the Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206, USA.
Whitlock
Ben B
BB
Xiao
Yi Qun
YQ
Bratton
Donna B
DB
Henson
Peter M
PM
D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis; D015153:Blotting, Western; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D005419:Flavonoids / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009504:Neutrophils / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D013997:Time Factors; D014466:Ultraviolet Rays; D051636:X-Linked Inhibitor of Apoptosis Protein; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000975:Antioxidants; D004791:Enzyme Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D005419:Flavonoids; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016877:Oxidants; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D045304:Cytochromes c; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D010749:Phosphoprotein Phosphatases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one