Transcriptional regulation of IL-8 by iron chelator in human epithelial cells is independent from NF-kappaB but involves ERK1/2- and p38 kinase-dependent activation of AP-1.
We have shown that the bacterial iron chelator, deferoxamine (DFO), triggers inflammatory signals including the production of CXC chemokine IL-8, in human intestinal epithelial cells (IECs) by activating the ERK1/2 and p38 kinase pathways. In this study we investigated the mechanisms involved in IL-8 generation by DFO, focusing on the transcription factors involved and the roles of both mitogen-activated protein kinases (MAPKs) in the transcription factor activation. Treatment of human epithelial HT-29 cells with DFO markedly up-regulated the expression of the essential components of the transcription factor AP-1 at a transcriptional level, while it minimally affected the expression of the NF-kappaB subunits. DFO also induced AP-1-dependent transcriptional activity in HT-29 cells, and this activity was further augmented by the wild-type c-Jun transfection. In contrast, the AP-1 activity by DFO was markedly decreased by the dominant-negative c-Jun transfection. Electrophoretic mobility shift assays revealed that DFO increases the specific binding of AP-1 but not of NF-kappaB. Such AP-1 binding and transcriptional activities were blocked by the inhibitors of the ERK1/2 and p38 kinase pathways, suggesting that both mitogen-activated protein kinases (MAPKs) lie upstream of AP-1. Besides its action on AP-1, DFO also induced the specific binding of other transcription factors such as CREB and Egr-1. In summary, our results indicate that iron chelator-induced IL-8 generation in IECs involves activation of ERK1/2 and p38 kinase and downstream activation of AP-1. A possible link between iron status and two additional transcription factors, that is, CREB and Egr-1, rather than NF-kappaB, was also suggested.
Choi
Eun-Young
EY
Department of Life Science, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea.
Park
Zee-Yong
ZY
Choi
Eun-Ju
EJ
Oh
Hyun-Mee
HM
Lee
SungGa
S
Choi
Suck-Chei
SC
Lee
Kang-Min
KM
Im
Sin-Hyeog
SH
Chun
Jang-Soo
JS
Jun
Chang-Duk
CD
D002470:Cell Survival / Q000187:drug effects; D003106:Colon / Q000473:pathology; D003676:Deferoxamine / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005562:Formazans / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D007502:Iron Chelating Agents / Q000494:pharmacology*; D008156:Luciferases / Q000032:analysis / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D013778:Tetrazolium Salts / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D005562:Formazans; D016209:Interleukin-8; D007502:Iron Chelating Agents; D016328:NF-kappa B; D013778:Tetrazolium Salts; D018808:Transcription Factor AP-1; C079782:MTT formazan; D008156:Luciferases; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D003676:Deferoxamine