Diisononyl Phthalate Differentially Affects Sirtuin Expression in the HepG2 Cell Line

Diethyl phthalate and dibutyl phthalate disrupt sirtuins expression in the HepG2 cells

Background

Phthalates are additives used as plasticizers among other uses, classified as endocrine disruptors and may contribute to some metabolic disorders. The aim of this work was to determine the effect of the exposure of diethyl phthalate (DEP) and dibutyl phthalate (DBP) on cell viability and reactive oxygen species (ROS) production, as well as the regulation of sirloins in HepG2 cells.

Methods

HepG2 cells were exposed to DEP or DBP at 0.1, 1, 10 and 100 μg/mL, and after 48 or 72 h the gene and protein expression of sirtuins was quantified by qRT-PCR and Western-Blot, respectively.

Results

Results showed that even at a low concentration of 0.1 μg/mL DEP affected the expression of Sirt3 and Sirt4, whereas DBP at 0.1 μg/mL affected Sirt3 and Sirt5 gene expression. Protein analysis showed a reduction in Sirt1 levels at a DEP concentration of 1 μg/mL and higher, while DBP at higher dose (100 μg/mL) decreased Sirt3 protein levels. Cell viability decreased by 20% only at higher dose (100 μg/mL) and ROS production increased at 10 and 100 μg/mL for both phthalates.

Conclusion

These findings indicate that exposure to low concentrations (0.1 μg/mL) of DEP or DBP can negatively influence the expression of some sirtuins.

Microfibrous Extracellular Matrix Changes the Liver Hepatocyte Energy Metabolism via Integrins

Cell line-based liver models are critical tools for liver-related studies. However, the conventional monolayer culture of hepatocytes, the most widely used in vitro model, does not have the extracellular matrix (ECM), which contributes to the three-dimensional (3D) arrangement of the hepatocytes in the liver. As a result, the metabolic properties of the hepatocytes in the monolayer tissue culture may not accurately reflect those of the hepatocytes in the liver. Here, we developed a modular platform for 3D hepatocyte cultures on fibrous ECMs produced by electrospinning, a technique that can turn a polymer solution to the micro/nanofibers and has been widely used to produce scaffolds for 3D cell cultures. Metabolomics quantitation by liquid chromatography-mass spectrometry (LC-MS) indicated that Huh7 hepatocytes grown in microfibers electrospun from silk fibroin exhibited reduced glycolysis and tricarboxylic acid (TCA) cycle, as compared to the cells cultured as a monolayer. Further mechanistic studies suggested that integrins were correlated to the ECM's effects. This is the first time to report how an ECM scaffold could affect the fundamental metabolism of the hepatocytes via integrins.

The Promises and Challenges of Toxico-Epigenomics: Environmental Chemicals and Their Impacts on the Epigenome

BACKGROUND

It has been estimated that a substantial portion of chronic and noncommunicable diseases can be caused or exacerbated by exposure to environmental chemicals. Multiple lines of evidence indicate that early life exposure to environmental chemicals at relatively low concentrations could have lasting effects on individual and population health. Although the potential adverse effects of environmental chemicals are known to the scientific community, regulatory agencies, and the public, little is known about the mechanistic basis by which these chemicals can induce long-term or transgenerational effects. To address this question, epigenetic mechanisms have emerged as the potential link between genetic and environmental factors of health and disease.

OBJECTIVES

We present an overview of epigenetic regulation and a summary of reported evidence of environmental toxicants as epigenetic disruptors. We also discuss the advantages and challenges of using epigenetic biomarkers as an indicator of toxicant exposure, using measures that can be taken to improve risk assessment, and our perspectives on the future role of epigenetics in toxicology.

DISCUSSION

Until recently, efforts to apply epigenomic data in toxicology and risk assessment were restricted by an incomplete understanding of epigenomic variability across tissue types and populations. This is poised to change with the development of new tools and concerted efforts by researchers across disciplines that have led to a better understanding of epigenetic mechanisms and comprehensive maps of epigenomic variation. With the foundations now in place, we foresee that unprecedented advancements will take place in the field in the coming years. https://doi.org/10.1289/EHP6104.