# Blockade of the estrogen receptor alpha–pregnane X receptor axis protects ovariectomized mice against ethanol-induced hepatotoxicity

## TL;DR

Blocking estrogen and a related receptor protects female mice from alcohol-related liver damage, suggesting a new pathway for treating alcohol-induced liver disease.

## Contribution

Identifies a novel estrogen receptor alpha–pregnane X receptor–NRF2 signaling axis contributing to sexual dimorphism in alcohol-related liver disease.

## Key findings

- OVX mice showed reduced ethanol-induced hepatotoxicity compared to sham-operated mice.
- Estrogen receptor alpha, PXR, and proinflammatory genes were upregulated in sham mice but not in OVX mice.
- NRF2 and antioxidant genes were upregulated in OVX mice, protecting against ethanol-induced liver damage.

## Abstract

Women develop alcohol-associated liver disease (ALD) faster than men at any level of alcohol consumption, implicating estrogen as a contributing factor. However, the precise mechanism remains unknown. Therefore, 12-week-old female C57BL/6N mice were subjected to either bilateral ovariectomy (OVX) or sham surgery. After a 3-week recovery period, the mice were fed either a 5% ethanol (EtOH)-containing liquid diet or paired-fed control diet for 10 days followed by a single gavage dose of EtOH (5 g/kg, 30% EtOH solution). The mice were examined for serum biochemical parameters, hepatotoxicity, histology, expression of xenobiotic nuclear receptors, pregnane X receptor (PXR) and constitutive androstane receptor, and their target gene mRNAs and proteins in hepatic and perigonadal white adipose tissues (pgWATs). While OVX mice on a control diet significantly gained weight, EtOH significantly increased hepatotoxicity, residual EtOH levels, lipid peroxidation, and oxidative stress in sham-operated mice but not in their OVX counterparts. In addition, in the livers and pgWAT of the sham mice, EtOH significantly increased the mRNA and/or protein levels of the major estrogen receptor (estrogen receptor α), PXR, constitutive androstane receptor, and their target genes, proinflammatory cytokines and chemokines, lipogenic genes, and fibroblast growth factor 21 levels, a predictive biomarker for ALD severity in humans, but inhibited nuclear factor erythroid 2-related factor 2 (NRF2) and its target genes encoding NQO1 and BHMT (betaine-homocysteine S-methyltransferase). Unexpectedly, all these changes were attenuated in the EtOH-fed OVX mice by the upregulation of NRF2 and aryl hydrocarbon receptor and their downstream antioxidant target genes. Together, these results suggest the existence of an estrogen-regulated estrogen receptor α–PXR–NRF2 signaling axis in liver and pgWAT, which contributes to sexual dimorphism in ALD.