Peroxisome Proliferator-activated Receptor α Negatively Regulates the Vascular Inflammatory Gene Response by Negative Cross-talk with Transcription Factors NF-κB and AP-1

doi:10.1074/jbc.274.45.32048

Peroxisome Proliferator-activated Receptor α Negatively Regulates the Vascular Inflammatory Gene Response by Negative Cross-talk with Transcription Factors NF-κB and AP-1*

From the ^‡INSERM U325, Département d'Athérosclérose, Institut Pasteur de Lille, 1 rue Pr. Calmette 59019 Lille, and Faculté de Pharmacie, Université de Lille II, 59000 Lille, France, the ^¶Laboratory of Molecular Biology, University of Gent and VIB, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium, the ^**INSERM U141, 41 Bd. de la Chapelle, 75745 Paris Cédex 10, France, and the ^‡Department of Molecular Carcinogenesis, NCI, National Institutes of Health, Bethesda, Maryland 20892

Abstract

Interleukin-6 (IL-6) is a pleiotropic cytokine, whose plasma levels are elevated in inflammatory diseases such as atherosclerosis. We have previously reported that peroxisome proliferator-activated receptor α (PPARα) ligands (fibrates) lower elevated plasma concentrations of IL-6 in patients with atherosclerosis and inhibit IL-1-stimulated IL-6 secretion by human aortic smooth muscle cells (SMC). Here, we show that aortic explants isolated from PPARα-null mice display an exacerbated response to inflammatory stimuli, such as lipopolysaccharide (LPS), as demonstrated by increased IL-6 secretion. Furthermore, fibrate treatment represses IL-6 mRNA levels in LPS-stimulated aortas of PPARα wild-type, but not of PPARα-null mice, demonstrating a role for PPARα in this fibrate action. In human aortic SMC, fibrates inhibit IL-1-induced IL-6 gene expression. Furthermore, activation of PPARα represses both c-Jun- and p65-induced transcription of the human IL-6 promoter. Transcriptional interference between PPARα and both c-Jun and p65 occurs reciprocally, since c-Jun and p65 also inhibit PPARα-mediated activation of a PPAR response element-driven promoter. This transcriptional interference occurs independent of the promoter context as demonstrated by cotransfection experiments using PPARα, p65, and c-Jun Gal4 chimeras. Overexpression of the transcriptional coactivator cAMP-responsive element-binding protein-binding protein (CBP) does not relieve PPARα-mediated transcriptional repression of p65 and c-Jun. Finally, glutathione S-transferase pull-down experiments demonstrate that PPARα physically interacts with c-Jun, p65, and CBP. Altogether these data indicate that fibrates inhibit the vascular inflammatory response via PPARα by interfering with the NF-κB and AP-1 transactivation capacity involving direct protein-protein interaction with p65 and c-Jun.

Footnotes

↵* This work was supported by grants of the Institut Pasteur de Lille, INSERM, Comité Français de Coordination des Recherches sur l'Athèrosdèrose et le cholestèrol, Rhône-Poulenc Rorer, Laboratoires Fournier, and the Région Nord-Pas-de-Calais/FEDER.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¶¶ To whom correspondence should be addressed: U.325 INSERM, Dépt. d'Athérosclérose, Institut Pasteur de Lille, 1 rue du Pr. Calmette, 59019 Lille, France. Tel.: 33-3-20-87-73-88; Fax: 33-3-20-87-73-60; E-mail: bart.staels@pasteur-lille.fr.
↵§ Supported by a grant from the Région Nord-Pas-de-Calais.
↵‖ Holds a fellowship of the IWT.
↵§§ Research director with the FWO-Vlaanderen.
↵2 Gervois, P., Torra, I. P., Chinetti, G., Grötzinger, T., Dubois, G., Fruchart, J. C., Fruchart-Najib, J., Leitersdorf, E., and Staels, B. (1999) Mol. Endocrinol. 13, 1535–1549.
Abbreviations:

SMC

smooth muscle cells

IL

interleukin

PPAR

peroxisome proliferator-activated receptor

PPRE

PPAR-response element

LPS

lipopolysaccharide

FCS

fetal calf serum

PCR

polymerase chain reaction

aa

amino acids

DMEM

Dulbecco's modified Eagle's medium

GST

glutathioneS-transferase

LBD

ligand binding domain

DBD

DNA binding domain

JNK

c-Jun N-terminal kinase

CBP

cAMP-responsive element-binding protein-binding protein
- Received June 21, 1999.
- Revision received August 16, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.