Lipopolysaccharide stimulation of ERK1/2 increases TNF-alpha production via Egr-1.
Lipopolysaccharide (LPS) is a potent activator of tumor necrosis factor-alpha (TNF-alpha) production by macrophages. LPS stimulates the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and increases TNF-alpha mRNA and protein accumulation in RAW 264.7 murine macrophages. However, the role of ERK1/2 activation in mediating LPS-stimulated TNF-alpha production is not well understood. Inhibition of ERK1/2 activation with PD-98059 or overexpression of dominant negative ERK1/2 decreased LPS-induced TNF-alpha mRNA quantity. LPS rapidly increased early growth response factor (Egr)-1 binding to the TNF-alpha promoter; this response was blunted in cells treated with PD-98059 or transfected with dominant-negative ERK1/2. Using a chloramphenicol acetyltransferase reporter gene linked to the Egr-1 promoter, we show that LPS increased Egr-1 promoter activity via an ERK1/2-dependent mechanism. These results delineate the role of ERK1/2 activation of Egr-1 activity in mediating LPS-induced increases in TNF-alpha mRNA expression in macrophages.
Shi
Liang
L
Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106-4906, USA.
Kishore
Raj
R
McMullen
Megan R
MR
Nagy
Laura E
LE
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D005799:Genes, Dominant; D017930:Genes, Reporter; D017874:Immediate-Early Proteins; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D004791:Enzyme Inhibitors; D005419:Flavonoids; D017874:Immediate-Early Proteins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one