# Polystyrene Nanoplastic Exposure Causes Reprogramming of Anti-Oxidative Genes Hmox1 and Sod3 by Inhibiting Nuclear Receptor RORγ in the Mouse Liver

## TL;DR

Polystyrene nanoplastics harm mice livers by altering antioxidant genes and reducing body weight, causing oxidative stress through changes in gene regulation.

## Contribution

This study reveals how PS-NPs reprogram antioxidant genes via RORγ inhibition and histone modifications in mice livers.

## Key findings

- PS-NPs reduced body weight and increased oxidative stress markers in mice livers.
- PS-NPs decreased Hmox1 and Sod3 gene expression and RORγ activity in the liver.
- Histone modifications at Hmox1 and Sod3 loci were altered by PS-NP exposure.

## Abstract

Polystyrene nanoplastics (NPs) are emerging environmental contaminants that may pose serious health hazards to human health. There is a remarkable lack of comparable research in mammalian models, although systemic toxicity studies have been carried out on a variety of aquatic species and poultry. This study investigated organ damage caused by NPs in mice through a comprehensive examination of biological parameters. The current work also demonstrates that PS-NPs cause oxidative stress in mice’s livers by altering levels of Hmox1 and Sod3 through histone modifications and nuclear receptor RORγ regulation. The findings of the study provide a comprehensive theoretical basis for the toxicity of PS-NPs and a potential therapy avenue for PS-NP-induced health damage.

Plastic pollution is acknowledged as a serious problem for ecosystems. Among these plastics, polystyrene nanoplastics (PS-NPs) are emerging environmental pollutants, and their biological effects on hepatotoxicity are the least explored. Therefore, the present work examined the effect of PS-NPs on the hepatic transcription of the antioxidant genes Hmox1 and Sod3 in mice (n = 6, treatment (PS-NPs) vs. vehicle group (Veh)), mediated by RORγ and epigenetic modifications. The results show that PS-NP mice had significantly reduced body weight; increased activity of adenosine triphosphate (ATP), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH), and Complexes I, III, and V in the liver; and increased Alanine Transaminase (ALT), Aspartate Transaminase (ASP), Alkaline Phosphatase (ALP), malondialdehyde (MDA) and reactive oxygen species (ROS) compared to the Veh group. Furthermore, PS-NPs resulted in considerably lower relative mRNA expression of Hmox1, Sod3, and RORγ in the liver than the Veh group. Likewise, when compared to Veh, PS-NPs significantly reduced the enrichment of RORγ, as well as the occupancies of the key components of the transcriptional activation pathway (P300, SRC1, Pol II, Ser5-Pol II, and Ser2-Pol II) at the loci of Hmox1 and Sod3. In comparison to Veh, PS-NPs showed downregulated occupancies of the histone active marks H3K9ac and H3K18ac, while H3K4me3 and H3K27me3 were higher at the target loci of Hmox1 and Sod3. In conclusion, the present study highlights that PS-NPs induce oxidative stress by modifying Hmox1 and Sod3 in mice’s livers through histone changes and nuclear receptor RORγ modulation.