Abstract
A functional interaction between peroxisome proliferator-activated receptor α (PPARα) and components of the circadian clock has been suggested, but whether these transcriptional factors interact to regulate the expression of their target genes remains obscure. Here we used a PPARα ligand, bezafibrate, to search for PPARα-regulated genes that are expressed in a CLOCK-dependent circadian manner. Microarray analyses using hepatic RNA isolated from bezafibrate treated-wild type, Clock mutant (Clk/Clk), and PPARα-null mice revealed that 136 genes are transcriptionally regulated by PPARα in a CLOCK-dependent manner. Among them, we focused on the plasminogen activator inhibitor-1 (PAI-1) gene, because its expression typically shows circadian variation, and it has transcriptional response elements for both PPAR and CLOCK. The bezafibrate-induced expression of PAI-1 mRNA was attenuated in Clk/Clk mice and in PPARα-null mice. The protein levels of PPARα were reduced in Clk/Clk hepatocytes. However, the overexpression of PPARα could not rescue bezafibrate-induced PAI-1 expression in Clk/Clk hepatocytes, suggesting that impaired bezafibrate-induced PAI-1 expression in Clk/Clk mice is not due to reduced PPARα expression. Luciferase reporter and chromatin immunoprecipitation analyses using primary hepatocytes demonstrated that DNA binding of both PPARα and CLOCK is essential for bezafibrate-induced PAI-1 gene expression. Pull-down assays in vitro showed that both PPARα and its heterodimerized partner retinoic acid receptor-α can serve as potential interaction targets of CLOCK. The present findings revealed that molecular interaction between the circadian clock and the lipid metabolism regulator affects the bezafibrate-induced gene expression.
Footnotes
-
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
-
This study was supported by the Ministry of Education, Culture, Sport, Science and Technology [Grant-in-Aid for Scientific Research on Priority Areas “Cancer” 20014016]; a Grant-in-Aid for Scientific Research (B) [Grant 21390047]; the Japan Society for the Promotion of Science [Grant-in-Aid for Challenging Exploratory Research 21659041]; and a Grant-in-Aid from the Mochida Memorial Foundation.
-
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.064402.
-
ABBREVIATIONS:
- PPARα
- peroxisome proliferator-activated receptor α
- PAI-1
- plasminogen activator inhibitor-1
- RXRα
- retinoic acid receptor α
- RT-PCR
- reverse-transcriptase polymerase chain reaction
- PCR
- polymerase chain reaction
- ChIP
- chromatin immunoprecipitation
- PPRE
- peroxisomal proliferator response element
- ROR
- retinoic acid-related orphan receptor.
- Received February 25, 2010.
- Accepted April 16, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|