Zearalenone-Induced Interaction between PXR and Sp1 Increases Binding of Sp1 to a Promoter Site of the eNOS, Decreasing Its Transcription and NO Production in BAECs.

Hyeon-Ju Lee,Du-Hyong Cho,Se-Young Oh,Suji Kim,Jung-Hyun Park,Inho Jo

doi:10.3390/toxins12060421

Abstract

Zearalenone (ZEN) is a non-steroidal mycotoxin that has various toxicological impacts on mammalian health. Here, we found that ZEN significantly affected the production of nitric oxide (NO) and the expression of endothelial NO synthase (eNOS) of bovine aortic endothelial cells (BAECs). A promoter analysis using 5′-serially deleted human eNOS promoter revealed that the proximal region (−135 to +22) was responsible for ZEN-mediated reduction of the human eNOS promoter activity. This effect was reversed by mutation of two specificity protein 1 (Sp1) binding elements in the human eNOS promoter. A chromatin immunoprecipitation assay revealed that ZEN increased Sp1 binding to the bovine eNOS promoter region (−113 to −12), which is homologous to −135 to +22 of the human eNOS promoter region. We also found that ZEN promoted the binding of the pregnane X receptor (PXR) to Sp1 of the bovine eNOS, consequently decreasing eNOS expression. This reduction of eNOS could have contributed to the decreased acetylcholine-induced vessel relaxation upon ZEN treatment in our ex vivo study using mouse aortas. In conclusion, our data demonstrate that ZEN decreases eNOS expression by enhancing the binding of PXR-Sp1 to the eNOS promoter, thereby decreasing NO production and potentially causing vessel dysfunction.

Highlights

Zearalenone (ZEN) is an estrogenic mycotoxin from Fusarium fungi, and it is a common contaminant of cereal grains such as oat, barley, and sorghum worldwide
We found that ZEN significantly decreased both nitric oxide (NO) production (Figure 1a) and endothelial NO synthase (eNOS) protein expression (Figure 1b) in a dose- and time-dependent manner in bovine aortic endothelial cells (BAECs)
When endothelial cells (ECs) were exposed to ZEN, we found that pregnane X receptor (PXR) interacted with specificity protein 1 (Sp1) as a cofactor to decrease eNOS expression, indicating that it affects the gene transcription of eNOS indirectly by altering the binding affinity of Sp1 to the promoter of eNOS

Summary

Introduction

Zearalenone (ZEN) is an estrogenic mycotoxin from Fusarium fungi, and it is a common contaminant of cereal grains such as oat, barley, and sorghum worldwide. Despite the regulation limit of ZEN for human food intake, humans are at risk of ZEN and its metabolites by intaking animal products. Toxins 2020, 12, 421 in Rutgers-New Brunswick, New Jersey, USA [2] Their concentrations are positively correlated with meat intake and body mass index, suggesting that humans can be exposed to ZEN through the consumption of livestock fed with contaminated corn/grains, which could commonly occur in animal industries in any attempt to reduce production cost. Most toxicity studies of ZEN have been focused on animals, yet some reported toxic effects on human embryonic stem cells and SNO human esophageal carcinoma cells [9,10] due to the potential risk of ZEN exposure from intaking animal products [2]. To understand better the potential risk posed by ZEN exposure, it would be important to assess its potential toxicological effects on blood vessels as well as endothelial cells (ECs)

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Conclusion