Early growth response factor-1 mediates prostaglandin E2-dependent transcriptional suppression of cytokine-induced tumor necrosis factor-alpha gene expression in human macrophages and rheumatoid arthritis-affected synovial fibroblasts.
Tumor necrosis factor-alpha (TNF-alpha) is a pleiotropic proinflammatory cytokine that modulates a broad range of inflammatory and immunological processes. We have investigated the potential immunomodulatory properties of prostaglandin E2 (PGE2) by examining the molecular mechanism by which the eicosanoid suppresses T-cell-derived interleukin-17 (IL-17)-induced TNF-alpha mRNA expression and protein synthesis in human macrophages and rheumatoid arthritis-affected synovial fibroblasts. Initial studies confirmed that PGE2 induces egr-1 mRNA expression and protein synthesis by restricted SAPK2/p38 MAPK-dependent activating transcription factor-2 (ATF-2) dimer transactivation of the egr-1 promoter as judged by studies using wild-type (WT) and deletion mutant egr-1 promoter constructs, Northern and Western blotting, and standard and supershift electrophoretic mobility shift analyses. Using human leukemic monocytic THP-1 cells stably transfected with WT and dominant-negative mutant expression constructs of Egr-1, cotransfected or not with a WT pTNF-615SVOCAT construct, we observed that PGE2 inhibition of IL-17-stimulated TNF-alpha mRNA expression and promoter activity was dependent on Egr-1 expression, as mutants of Egr-1, alone or in combination, markedly abrogated any inhibitory effect of PGE2. Standard and supershift electrophoretic mobility shift analysis, signaling "decoy" overexpression studies, and pTNF-615SVOCAT promoter assays using WT and mutant promoter constructs revealed that IL-17-up-regulated promoter activity was largely dependent on ATF-2/c-Jun transactivation. PGE2 suppression of IL-17-induced ATF-2/c-Jun transactivation and DNA binding was dependent on Egr-1-mediated inhibition of induced c-Jun expression. We suggest that egr-1 is an immediate-early PGE2 target gene that may be a key regulatory factor in mediating eicosanoid control of genes involved in the immune and inflammatory responses.
Faour
Wissam H
WH
Department of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
Alaaeddine
Nada
N
Mancini
Arturo
A
He
Qing Wen
QW
Jovanovic
Dragan
D
Di Battista
John A
JA
D016475:3T3 Cells; D000818:Animals; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics*; D015232:Dinoprostone / Q000494:pharmacology*; D051766:Early Growth Response Protein 1; D005347:Fibroblasts / Q000276:immunology / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics*; D020381:Interleukin-17 / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology; D051379:Mice; D009000:Monocytes / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D013583:Synovial Membrane / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D020381:Interleukin-17; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D015232:Dinoprostone