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Inhibitory Effects of a Novel PPAR-? Agonist MEKT1 on Pomc Expression/ACTH Secretion in AtT20 Cells.


ABSTRACT: Although therapeutic effects of the peroxisome proliferator-activated receptor gamma (PPAR-?) agonists rosiglitazone and pioglitazone against Cushing's disease have been reported, their effects are still controversial and inconsistent. We therefore examined the effects of a novel PPAR-? agonist, MEKT1, on Pomc expression/ACTH secretion using murine corticotroph-derived AtT20 cells and compared its effects with those of rosiglitazone and pioglitazone. AtT20 cells were treated with either 1?nM~10??M MEKT1, rosiglitazone, or pioglitazone for 24 hours. Thereafter, their effects on proopiomelanocortin gene (Pomc) mRNA expression were studied by qPCR and the Pomc promoter (-703/+58) activity was demonstrated by luciferase assay. Pomc mRNA expression and promoter activity were significantly inhibited by MEKT1 at 10??M compared to rosiglitazone and pioglitazone. SiRNA-mediated PPAR-? knockdown significantly abrogated MEKT1-mediated Pomc mRNA suppression. ACTH secretion from AtT20 cells was also significantly inhibited by MEKT1. Deletion/point mutant analyses of Pomc promoter indicated that the MEKT1-mediated suppression was mediated via NurRE, TpitRE, and NBRE at -404/-383, -316/-309, and -69/-63, respectively. Moreover, MEKT1 significantly suppressed Nur77, Nurr1, and Tpit mRNA expression. MEKT1 also was demonstrated to inhibit the protein-DNA interaction of Nur77/Nurr1-NurRE, Tpit-TpitRE, and Nur77-NBRE by ChIP assay. Taken together, it is suggested that MEKT1 could be a novel therapeutic medication for Cushing's disease.

SUBMITTER: Parvin R 

PROVIDER: S-EPMC5937427 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Inhibitory Effects of a Novel PPAR-<i>γ</i> Agonist MEKT1 on <i>Pomc</i> Expression/ACTH Secretion in AtT20 Cells.

Parvin Rehana R   Noro Erika E   Saito-Hakoda Akiko A   Shimada Hiroki H   Suzuki Susumu S   Shimizu Kyoko K   Miyachi Hiroyuki H   Yokoyama Atsushi A   Sugawara Akira A  

PPAR research 20180423


Although therapeutic effects of the peroxisome proliferator-activated receptor gamma (PPAR-<i>γ</i>) agonists rosiglitazone and pioglitazone against Cushing's disease have been reported, their effects are still controversial and inconsistent. We therefore examined the effects of a novel PPAR-<i>γ</i> agonist, MEKT1, on <i>Pomc</i> expression/ACTH secretion using murine corticotroph-derived AtT20 cells and compared its effects with those of rosiglitazone and pioglitazone. AtT20 cells were treated  ...[more]

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