A New Target for Absin in Treating Necrotizing Enterocolitis in Newborns: Intestinal FXR and Ferroptosis

Necrotizing enterocolitis (NEC) is a common and often fatal intestinal disease in premature infants, yet its pathogenesis remains incompletely understood. A recent study published in Immunity has elucidated the molecular mechanisms by which the bile acid receptor farnesoid X receptor (FXR) exacerbates NEC through the regulation of ferroptosis in intestinal epithelial cells (IECs) and dysfunction of group 3 innate lymphoid cells (ILC3). The study also proposed potential therapeutic targets. This article will guide you through the key technologies, experimental designs, and core conclusions of this research.

I. Panoramic View of Core Experimental Technologies

This study integrated multi-omics technologies and cutting-edge molecular biological approaches to verify the scientific hypotheses step by step:

1. Single-cell RNA sequencing (scRNA-seq)

Analysis of the transcriptomic heterogeneity of intestinal epithelial cells (IECs) in NEC mice identified specific high expression of FXR in enterocytes.

2. Flow cytometry and cell sorting

Detection of FXR protein expression in IECs and sorting of ILC3 (CD45⁺Lin⁻CD90.2⁺CD127⁺KLRG1⁻) for functional analysis.

3. Multiplexed immunohistochemistry (mIHC)

Panel design:

FGF19 localization: FGF19 (red) + EpCAM (white, for epithelial cell marking) + DAPI (blue, for nuclear staining).

FXR and lipid peroxidation: FXR (red) + 4-HNE (green, lipid peroxidation marker) + EpCAM (white) + DAPI (blue).

Colocalization analysis revealed the spatiotemporal association between FXR and oxidative damage in the intestines of NEC patients.

4. Lipidomics (LC-MS/MS)

Quantification of phospholipid peroxides (PE-PUFAs) confirmed that FXR promotes ferroptosis by upregulating ACSL4.

5. Genetic editing and animal models

Generation of intestine-specific FXR knockout mice (Fxr^AlEC) combined with NEC induction models (hypoxia + cold exposure + formula feeding).

6. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays

Verification that FXR directly binds to the ACSL4 promoter to regulate its transcriptional activity.

II. Sample Grouping Logic

The study validated its findings through clinical cohorts and animal models:

1. Clinical samples

NEC group: 6 surgically confirmed NEC infants (plasma, intestinal tissue).

Control group: 6 age-matched non-NEC infants (normal bowel resected during congenital intestinal malformation surgery).

2. Mouse experiments

Genotype grouping: Fxr^AlEC (intestinal FXR knockout) vs. Fxr^fl/fl (wild-type control).

Interventional grouping:

FXR modulation: agonist Fexaramine, antagonist Gly-β-MCA.

Ferroptosis intervention: inhibitor Liproxstatin-1, ACSL4 inhibitor PRGL493.

Microbial intervention: fecal microbiota transplantation from NEC patients + butyrate supplementation.

III. Disruptive Conclusions

1. FXR as a key driver of NEC

Intestinal FXR expression in NEC patients was significantly elevated and positively correlated with plasma FGF19 (an FXR downstream target), suggesting that FXR activation exacerbates the disease.

2. Dysbiosis of microbiota-epithelial cell interactions

NEC-associated dysbiosis reduced short-chain fatty acids (SCFAs, e.g., butyrate), lifting their inhibitory effect on FXR and leading to enterocyte ferroptosis.

3. The ferroptosis-ILC3 axis exacerbates inflammation

FXR transcriptionally activates ACSL4, promoting lipid peroxidation and ferroptosis. Oxidized phospholipids (PEox) released from dying enterocytes inhibit ILC3 secretion of IL-22, weakening intestinal barrier repair.

4. Novel therapeutic strategies

Targeted inhibition of intestinal FXR, ACSL4, or ferroptosis significantly alleviated NEC symptoms in mice, increasing survival rates by over 50%.

IV. Implications for Clinical Translation

1. Diagnostic biomarkers: Plasma FGF19 combined with lipid peroxidation products (LPO) may serve as early warning indicators for NEC.

2. Therapeutic directions: Development of intestine-specific FXR antagonists (e.g., Gly-β-MCA) or ferroptosis inhibitors, or modulation of microbiota via probiotics/butyrate supplementation.

Summary

This study first revealed the central role of the FXR-ferroptosis-ILC3 axis in NEC, providing a new perspective for understanding the molecular mechanisms of intestinal inflammation and offering precise targets for clinical intervention. The integration of multi-omics technologies and cross-species models highlights the power of translational medical research.

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