Differential cytokine regulation by NF-kappaB and AP-1 in Jurkat T-cells.
BACKGROUND
Activator protein (AP)-1 and nuclear factor (NF)-kappaB largely control T-cell activation, following binding of foreign antigens to the T-cell receptor leading to cytokine secretion. Elevated levels of pro-inflammatory cytokines and chemokines such as TNF, IL-6 and CXCL8 are associated with several human diseases including cystic fibrosis, pulmonary fibrosis and AIDS. The aim of this study was to investigate the role of the transcription factors, AP-1 and NF-kappaB, in IL-6 and CXCL8 regulation in Jurkat T-cells.


RESULTS
Phorbol myristate acetate (PMA) exposure resulted in an up-regulation of AP-1 and down-regulation of NF-kappaB activity, however, exposure to heat killed (HK) Escherichia. coli MG1655 resulted in a dose-dependent increase in NF-kappaB activity without affecting AP-1. The cytokine profile revealed an up-regulation of the chemokine CXCL8 and the pro-inflammatory cytokines TNF, IL-2 and IL-6 following treatment with both PMA and HK E. coli, while the levels of the anti-inflammatory cytokine IL-10 were not affected by PMA but were significantly down-regulated by HK E. coli. AP-1 activation was significantly increased 2 h after PMA exposure and continued to increase thereafter. In contrast, NF-kappaB responded to PMA exposure by a rapid up-regulation followed by a subsequent down-regulation. Increased intracellular Ca2+ concentrations countered the down-regulation of NF-kappaB by PMA, while similar treatment with calcium ionophore resulted in a reduced NF-kappaB activity following induction with HK E. coli. In order to further study NF-kappaB activation, we considered two up-stream signalling proteins, PKC and Bcl10. Phosphorylated-PKC levels increased in response to PMA and HK E. coli, while Bcl10 levels significantly decreased following PMA treatment. Using an NF-kappaB activation inhibitor, we observed complete inhibition of IL-6 expression while CXCL8 levels only decreased by 40% at the highest concentration. Treatment of Jurkat T-cells with PMA in the presence of JNK-inhibitor suppressed both CXCL8 and IL-6 while PKC-inhibitor primarily decreased CXCL8 expression.


CONCLUSIONS
The present study shows that NF-kappaB regulated IL-6 but not CXCL8. This complex regulation of CXCL8 suggests that there is a need to further evaluate the signalling pathways in order to develop new treatment for diseases with elevated CXCL8 levels, such as AIDS and autoimmune diseases.
Khalaf
Hazem
H
Biology, Orebro Life Science Center, School of Science and Technology, Orebro University, SE-701 82 Orebro, Sweden.
Jass
Jana
J
Olsson
Per-Erik
PE
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000074018:B-Cell CLL-Lymphoma 10 Protein; D016207:Cytokines / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism*; D016209:Interleukin-8 / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019169:Jurkat Cells; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
D048868:Adaptor Proteins, Signal Transducing; D000074018:B-Cell CLL-Lymphoma 10 Protein; C118591:BCL10 protein, human; C508606:CXCL8 protein, human; D016207:Cytokines; D015850:Interleukin-6; D016209:Interleukin-8; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate