PPAR-gamma agonists inhibit toll-like receptor-mediated activation of dendritic cells via the MAP kinase and NF-kappaB pathways.
Dendritic cells (DCs) play an important role in initiating and maintaining primary immune responses. However, mechanisms involved in the resolution of these responses are elusive. We analyzed the effects of 15d-PGJ2 and the synthetic peroxisome proliferator-activated receptor (PPAR)-gamma ligand troglitazone (TGZ) on the immunogenicity of human monocyte-derived DCs upon stimulation with toll-like receptor (TLR) ligands. Activation of PPAR-gamma resulted in a reduced stimulation of DCs via the TLR ligands 2, 3, 4, and 7, characterized by down-regulation of costimulatory and adhesion molecules and reduced secretion of cytokines and chemokines involved in T-lymphocyte activation and recruitment. MCP-1 (monocyte chemotactic protein-1) production was increased due to PPAR-gamma activation. Furthermore, TGZ-treated DCs showed a significantly reduced capacity to stimulate T-cell proliferation, emphasizing the inhibitory effect of PPAR-gamma activation on TLR-induced DC maturation. Western blot analyses revealed that these inhibitory effects on TLR-induced DC activation were mediated via inhibition of the NF-kappaB and mitogen-activated protein (MAP) kinase pathways while not affecting the PI3 kinase/Akt signaling. Our data demonstrate that inhibition of the MAP kinase and NF-kappaB pathways is critically involved in the regulation of TLR and PPAR-gamma-mediated signaling in DCs.
Appel
Silke
S
Department of Hematology, Oncology and Immunology, University of Tübingen, Otfried-Müller Str 10, D-72076 Tübingen, Germany.
Mirakaj
Valdete
V
Bringmann
Anita
A
Weck
Markus M
MM
Grünebach
Frank
F
Brossart
Peter
P
D015153:Blotting, Western; D002465:Cell Movement / Q000276:immunology; D002839:Chromans / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism*; D047495:PPAR gamma / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000494:pharmacology; D045162:Thiazolidinediones / Q000494:pharmacology; D051193:Toll-Like Receptors / Q000276:immunology / Q000378:metabolism*; D000077288:Troglitazone
C477819:15-deoxyprostaglandin J2; D002839:Chromans; D016207:Cytokines; D007004:Hypoglycemic Agents; D016328:NF-kappa B; D047495:PPAR gamma; D045162:Thiazolidinediones; D051193:Toll-Like Receptors; D020928:Mitogen-Activated Protein Kinases; D000077288:Troglitazone; D015230:Prostaglandin D2