Dibutyltin dichloride is a potent PPAR alpha antagonist

Abstract

Organotins are endocrine disruptors and a widely distributed environmental chemical. The best‐studied organotin is tributyltin (TBT), which has been shown to bind to PPAR gamma/RXR alpha and induces adipogenesis in different mammalian cells. Dibutyltin (DBT) is another organotin used as a stabilizer in the production of polyvinyl chloride plastics, and it is also the major metabolite formed from TBT in vivo. Recently, we demonstrated that DBTs are PPARγ partial agonists and that DBT chloride and dilaurate are also partial RXRα agonists. Additionally, DBTs induce adipogenesis in a PPARγ‐dependent manner and repress inflammatory genes in preadipocyte cell culture. However, the role of DBTs on PPAR alpha is still unknown. In the present study, we investigate the effect of dibutyltins pharmacological effects on PPAR alpha in mammalian cells. In reporter gene assay using HeLa cells, we observed that dibutyltins do not display an agonist effect on PPAR alpha. Therefore, we decided to explore the antagonistic effects on PPARα. In the cell‐based reporter gene assay, treatment with PPAR alpha agonist (bezafibrate) induced a 3.3‐fold activation on PPAR alpha. On the other hand, DBT dilaurate and DBT dichloride produced a dose‐dependently inhibition of the PPAR alpha transcription transactivation induced by bezafibrate. These effects were not due to the cytotoxicity. Next, we compared the antagonistic results of DBT dilaurate and DBT dichloride to GW6471, a well‐known synthetic specific PPAR alpha antagonist. Transfected cells were treated with vehicle, an increasing concentration of DBT dilaurate, DBT dichloride or GW6471 in the presence of Bezafibrate (10μM). Bezafibrate activation in the absence of antagonist was considered as 100%. The percentage of GW6471, DBT dilaurate, and DBT dichloride were calculated in comparison to bezafibrate. DBT dilaurate and DBT dichloride showed a dose‐dependent inhibition of bezafibrate induced PPARα transcriptional activity. The median inhibitory concentration (IC50) of DBT dilaurate (4.1μM) was significantly higher than GW647, which displayed an IC50 value of 0.13μM. However, IC50 of DBT dichloride upon PPAR alpha was significantly lower (0.26μM) and similar to GW647. Therefore, DBT dilaurate was considered as a weak antagonist, while the dibutyltin dichloride displayed a potent antagonist effect on PPAR alpha. Next, to further characterize these effects on a physiological assay, we analyzed the catalase activity induced by WKY14643, a PPAR alpha agonist in the presence and absence of DBT dilaurate and DBT dichloride in HepG2 and HFF‐1 cells. As was observed with GW647, DBT dilaurate and DBT dichloride inhibited the catalase activity induced by WKY14643 in a dose‐dependent manner. These results showed for the first time that DBT dilaurate and dichloride display a PPAR alpha antagonist effect.Support or Funding InformationNational Council for Scientific and Technological Development–Grant number: CNPq 486613/2013‐5 and Fundacao de Apoio a Pesquisa do Distrito Federal ‐ FAPDF ‐ Edital 04/2017.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.