Puerarin ameliorates colitis by direct suppression of macrophage M1 polarization in DSS mice

Background

Ulcerative colitis (UC) is a type of inflammatory bowel disease primarily affecting the colon and rectum. The clinical symptoms of UC include persistent diarrhea, abdominal pain, and rectal bleeding, with chronic inflammation often limited to the mucosal layer of the colon. Macrophages play a significant role in the pathogenesis of UC in response to the presence of gut microbiota. Puerarin is an active compound derived from the root of pueraria lobata, a traditional Chinese herbal medicine, and exhibits potent anti-inflammatory properties in various diseases and disease models including UC-like colitis in mice. However, how the molecule achieves its therapeutic effect in colitis by re-polarizing macrophages remains poorly understood.

Purpose

Utilizing in vivo and in vitro experimental methods along with multi-omics analysis, we aimed to elucidate the potential mechanism by which puerarin targets macrophages to treat colitis.

Methods

The inflammation induced by DSS was assessed both locally in the gut and systemically, and the anti-inflammatory effect of puerarin was evaluated using molecular and histological assays such as H&E staining, qPCR, ELISA, Western blot, and immunofluorescence. Intestinal permeability parameters were measured by in vivo imaging, immunofluorescence, Western blot, qPCR, and PAS staining. The central role of macrophages in colitis was investigated through macrophage depletion/infusion using cytological methods. The direct effects of puerarin on the macrophages were examined by CCK8, flow cytometry, and qPCR in vitro. Additionally, 16S rRNA sequencing and metabolomics analysis of gut contents were conducted. Identification of key pathogenic flora was facilitated by a trans-omic approach and validated both in vitro and in vivo.

Results

Puerarin exerted a direct and robust suppression of M1-like polarization of macrophages in vitro, which was sufficient to confer therapeutic benefits in terms of colonic lesions and systemic inflammation in DSS mice. Puerarin also reduced the abundance of Akkermansia muciniphila in the gut, which was significantly upregulated in DSS mice in our experimental context. Further study demonstrated that puerarin effectively suppressed M1-like macrophage activation induced by Akkermansia muciniphila secreted protein Amuc_2172, thereby altering the pathology in the DSS model.

Conclusion

Our data suggest that the pathogenesis of DSS colitis is mediated by host cellular responses to toxic foreign molecules and the gut microbiota, and targeting specific cell populations, such as macrophages, with puerarin holds potential therapeutic value.