Abstract |
The inflammation that occurs during atherosclerosis is characterized by the release of large amounts of group IIA secretory phospholipase A2 (sPLA2-IIA). This study was designed to define the function of the three peroxisome proliferator-activated receptors (PPARs) on sPLA2 expression in vascular smooth muscle cells (VSMCs). We found that PPAR ligands decreased sPLA2-IIA activity and inhibited mRNA accumulation under inflammatory conditions. Furthermore, interleukin-1beta-induced sPLA2-IIA promoter activity was inhibited by the three PPAR ligands and in a similar way when cells were cotransfected with PPARalpha, PPARbeta, or PPARgamma, plus retinoid X receptor alpha (RXRalpha). Our study revealed that the regulation of sPLA2-IIA gene transcription by PPARalpha/RXR and PPARgamma/RXR heterodimers requires an interaction with a PPAR response element (PPRE) of the sPLA2-IIA promoter. In contrast, PPARbeta operates through a PPRE-independent mechanism. In addition, we demonstrated that VSMCs expressed the transcriptional repressor BCL-6. Overexpression of BCL-6 markedly reduced sPLA2-IIA promoter activity in VSMCs, while a dominant negative form of BCL-6 abrogated sPLA2 repression by PPARbeta. The PPARbeta agonist induced a BCL-6 binding to the sPLA2 promoter in VSMCs under inflammatory conditions. The knockdown of BCL-6 by short interfering RNA abolished the inhibitory effect of the PPARbeta ligand on sPLA2 activity and prostaglandin E2 release. Thus, the inhibition of sPLA2-IIA activity by PPARbeta agonists may provide a promising approach to impacting the initiation and progression of atherosclerosis.
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Authors | Lucas Ravaux, Chantal Denoyelle, Claire Monne, Isabelle Limon, Michel Raymondjean, Khadija El Hadri |
Journal | Molecular and cellular biology
(Mol Cell Biol)
Vol. 27
Issue 23
Pg. 8374-87
(Dec 2007)
ISSN: 1098-5549 [Electronic] United States |
PMID | 17908795
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Interleukin-1beta
- Ligands
- PPAR-beta
- Proto-Oncogene Proteins c-bcl-6
- RNA, Messenger
- RNA, Small Interfering
- Repressor Proteins
- Retinoid X Receptors
- Group II Phospholipases A2
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Topics |
- Animals
- Cattle
- Enzyme Induction
(drug effects)
- Gene Expression Regulation, Enzymologic
(drug effects)
- Group II Phospholipases A2
(biosynthesis, genetics)
- Interleukin-1beta
(pharmacology)
- Ligands
- Male
- Muscle, Smooth, Vascular
(cytology, drug effects, enzymology)
- Myocytes, Smooth Muscle
(drug effects, enzymology)
- PPAR-beta
(metabolism)
- Protein Binding
(drug effects)
- Proto-Oncogene Proteins c-bcl-6
(metabolism)
- RNA, Messenger
(genetics, metabolism)
- RNA, Small Interfering
(metabolism)
- Rats
- Rats, Wistar
- Repressor Proteins
(metabolism)
- Response Elements
- Retinoid X Receptors
(metabolism)
- Sequence Deletion
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