Polyphyllin Ⅵ modulates macrophage polarization through autophagy-NLRP3 inflammasome to alleviate inflammatory bowel disease

Background

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract with a rising global prevalence. If left untreated, it can result in severe complications, including colon cancer. Key factors in IBD pathogenesis include macrophages, NOD-like receptor thermal protein domain associated protein 3 (NLRP3), and autophagy. Polyphyllin Ⅵ (PPⅥ), a metanoidal saponin derived from the traditional Chinese herb Chonglou, exhibits significant anti-inflammatory and anti-cancer properties, making it a compound of considerable therapeutic interest.

Purpose

The present study investigated the relevant mechanism of PPⅥ on protecting IBD from the perspective of NLRP3 as well as macrophage immunomodulation and laid a theoretical foundation for the development of novel IBD therapeutic drugs.

Methods

The IBD mice were prepared by dextran sodium sulfate, and RAW 264.7 inflammatory cells were established through LPS and ATP stimulation. The indicators of macrophage polarization, NLRP3, and autophagy were detected using Western Blot, RT-qPCR, H&E staining, immunofluorescence, and flow cytometry.

Results

PPⅥ can enhance the inflammatory state of LPS-induced RAW264.7 macrophages, which can reduce weight loss, decrease DAI score, increase colon length, reduce oxidative stress, and decrease intestinal epithelial barrier damage, and thus diminish inflammatory injury in DSS-induced IBD mice. PPⅥ can modify intestinal inflammation and injury by modulating macrophage function. The administration of PPⅥ can maintain the balance between M1-type macrophages and M2-type macrophages while regulating the intestinal macrophage polarization via the NLRP3 inflammasome and autophagy through wildtype mice, cells, and Nlrp3^-/- mice.

Conclusion

PPⅥ can regulate macrophage polarization through autophagic modulation of NLRP3 inflammasome to promote the repair of intestinal epithelial damage and maintain the integrity of the mucosal barrier, which contributes to the attenuation of inflammatory injury in DSS-induced IBD mice and provides a database for the development of novel clinical drugs.

Innovations

1. This subject discovered the protective effect of PPⅥ on IBD mice.

2. This subject proved that macrophages have an important role in the intestinal protection of PPⅥ in IBD mice, and PPⅥ can inhibit the polarization of M1-type macrophages and promote the polarization of M2-type macrophages.

3. This subject demonstrated that PPⅥ could regulate macrophage polarization through NLRP3 inflammasome and ameliorate intestinal inflammation in vitro, in vivo, and in Nlrp3^-/- mice.

4. This subject confirmed that PPⅥ could regulate macrophage polarization to alleviate inflammatory injury by inhibiting NLRP3 inflammasome through modulating autophagy in vitro, in vivo, and the application of inhibitors.

5. This study explored the developmental value of PPⅥ and laid the theoretical foundation for the development of novel therapeutic drugs as well as therapeutic strategies for IBD.