PPAR Receptors Expressed from Vectors Containing CMV Promoter Can Enhance Self-Transcription in the Presence of Fatty Acids from CLA-Enriched Egg Yolks—A Novel Method for Studies of PPAR Ligands

Abstract

PPAR receptors are ligand-dependent transcription factors activated in response to various small lipophilic ligands controlling the expression of different genes involved in cellular differentiation, development, metabolism, and tumorigenesis. Unexpectedly, our previous studies have shown that single plasmid-based expression of PPARs under the control of CMV promoter/enhancer was significantly elevated in the presence of PPAR agonists. Here we show that the PPAR reporters controlled by the CMV promoter/enhancer, that was shown to contain three internal non-canonical PPRE elements, can be used as a fast screening system for more effective PPAR ligands. This model allowed us to confirm our previous results indicating that fatty acids of CLA-enriched egg yolks (EFA-CLAs) are efficient PPAR ligands that can specifically upregulate the expression of PPARα and PPARγ leading to downregulation of MCF-7 cancer cell proliferation. We also show that synthetic cis9,trans11CLA is more effective in transactivation of PPARγ, while trans10,cis12CLA of PPARα receptor indicating the selectivity of the CLA isomers. This report presents a novel, fast, and reliable strategy for simple testing of PPAR ligands using PPAR expressing plasmids containing the CMV promoter/enhancer that can trigger the positive feedback loop of PPAR self-transcription in the presence of PPAR ligands.

Disclosure Statement

The authors report no financial or other conflict of interest relevant to the subject of this article.

Authors’ Contributions

Conception and design of experiment: Adam Master, Aneta A. Koronowicz, Paula Banks.

Acquisition of data: Dominik Domagała, Ewelina Piasna-Słupecka, Mariola Drozdowska, Aneta A. Koronowicz.

Analysis and interpretation of data: Aneta A. Koronowicz, Adam Master.

Writing—original draft: Aneta A. Koronowicz, Paula Banks.

Revising the article critically for important intellectual content: Adam Master.

Writing—review and editing: Aneta A. Koronowicz.

Project manager: Teresa Leszczyńska.

Additional information

Funding

This work was supported by the Polish National Science Center (grant number 2011/03/B/NZ9/01423) “Conjugated linoleic acid (CLA)-induced transcriptional activation of PPAR-an investigation of molecular mechanisms of putative anticancer action of fatty acids of CLA-enriched egg yolks.”