# Human Breast Milk‐Derived Exosomal FP671120.4 Inhibits Macrophage M1 Polarization via Modulating the ELAVL1/Nrf2 Axis in Sepsis‐Associated Liver Injury

## TL;DR

Human breast milk exosomes reduce liver damage in sepsis by preventing harmful macrophage activation through a specific protein pathway.

## Contribution

Identifies FP671120.4 in breast milk exosomes as a novel inhibitor of M1 macrophage polarization via the ELAVL1/Nrf2/HO-1 pathway in sepsis-associated liver injury.

## Key findings

- HBM-Exos inhibit M1 macrophage polarization via the Nrf2/HO-1 pathway in LPS-induced Kupffer cells.
- FP671120.4 enhances ELAVL1-Nrf2 interaction and stabilizes Nrf2 mRNA.
- FP671120.4 reverses HBM-Exos-mediated Nrf2 mRNA increase and inhibits M1 polarization.

## Abstract

Sepsis‐associated liver injury (SALI) plays a major role in aggravating disease progression and worsening prognosis in patients with sepsis. Macrophage polarization is a key factor in the modulation of SALI progression. Recent studies have shown that human breast milk‐derived exosomes (HBM‐Exos) regulate processes involved in macrophage polarization. Here, we investigated the function and mechanism of action of HBM‐Exos in a macrophage polarization model of SALI. The extracted HBM‐Exos were identified by morphological analysis and detection of marker proteins using flow cytometry. Human Kupffer cells were treated with lipopolysaccharide (LPS) to simulate macrophage polarization in SALI. Cell viability was measured using a CCK‐8 kit. Protein and gene expression levels were evaluated using western blotting and RT‐qPCR, respectively. ELISA kits were used to assess the levels of inflammatory cytokines. The interactions between FP671120.4, ELAV Like RNA binding protein 1 (ELAVL1), and nuclear factor erythroid 2‐related factor 2 (Nrf2) were verified by RIP analysis. HBM‐Exos inhibited M1 macrophage polarization by promoting Nrf2 expression and phosphorylation via activation of the Nrf2/Heme oxygenase‐1 (HO‐1) signaling pathway in LPS‐induced Kupffer cells. Furthermore, FP671120.4 reversed the HBM‐Exos‐mediated increase in Nrf2 mRNA stability. HBM‐Exos‐derived FP671120.4 enhanced the interaction between ELAVL1 and Nrf2. As a result, FP671120.4 inhibited M1 polarization by inducing Nrf2 expression via activation of the Nrf2/HO‐1 pathway. These findings suggest that HBM‐Exos‐derived FP671120.4 may inhibit M1 macrophage polarization through the ELVAL1/Nrf2/HO‐1 signaling pathway in LPS‐induced Kupffer cells.