Ginsenoside Rb1-Enriched Saponin Fraction Inhibits M1 Macrophage Polarization by Suppression of TLR4 Trafficking in Metabolic Dysfunction-Associated Alcoholic Liver Disease.

Background/

Objectives

Metabolic dysfunction-associated alcoholic liver disease (MetALD) is a serious worldwide health concern, exhibiting metabolic dysfunction-associated lipid accumulation, alcohol-associated oxidative damage, and endotoxin-induced inflammation. Rb1-enriched red ginseng saponin fraction (RGSF) has been known to exhibit anti-inflammatory and anti-oxidative properties, but its role in MetALD remains to be fully elucidated. This study aims to investigate the specific mechanism of RGSF in the MetALD mouse model.

Methods

The MetALD mouse model was administered with or without Rb1-RGSF for 7 weeks. Histopathological and molecular analyses, along with primary cell isolation, were conducted for in vivo and ex vivo investigations. M1 macrophage polarization was assessed by analyzing pro-inflammatory cytokine expression. NF-kB/p65 and TLR4 protein expression were measured before being visualized using immunofluorescence assays and confocal microscopy.

Results

Histopathological examination revealed that RGSF treatment markedly reduced hepatic steatosis and attenuated inflammatory lesions in MetALD independent of oxidative stress. Notably, RGSF administration suppressed the LPS-induced internalization of surface TLR4. During the early inflammatory phase, RGSF prevented the LPS-mediated loss of the 130 kDa TLR4 form at the cell membrane, thereby limiting the generation of its 110 kDa cytoplasmic form. LPS-binding assay confirmed the direct interactions between TLR4 and RGSF.

Conclusions

Collectively, these findings demonstrate that RGSF regulates TLR4 expression and trafficking, leading to the suppression of M1 macrophage polarization by inhibiting LPS-TLR4 surface interactions, thus exhibiting hepatoprotective effects.