Flos sophorae immaturus exosome-like nanovesicles alleviate ulcerative colitis by attenuating intestinal oxidative stress and inflammation through activating Aryl hydrocarbon receptor via gut microbiota and tryptophan metabolism regulation.

Flos Sophorae immaturus exosome-like nanovesicles (FSIEVs) were successfully isolated with high purity, uniform particle size, and excellent biocompatibility and biosafety.

• FSIEVs were characterized as demonstrating 'high purity, uniform particle size, and excellent biocompatibility and biosafety'
• The nanovesicles were isolated from Flos Sophorae immaturus (FSI), an immature flower bud used in traditional medicine
• The characterization established potential for treating UC based on these physicochemical properties

FSIEVs improved the overall condition of dextran sodium sulfate (DSS)-induced murine UC models by reducing intestinal inflammation and oxidative stress.

• The in vivo model used was a dextran sodium sulfate-induced murine model of UC
• FSIEVs reduced intestinal inflammation and oxidative stress in treated animals
• FSIEVs also repaired intestinal barrier integrity in the DSS-induced UC model
• Improvements in 'overall condition' of the animals were observed with FSIEV treatment

FSIEVs modulated gut microbiota composition by enhancing Lactobacillus species, particularly L. paracasei.

• FSIEVs exhibited anti-UC effects by 'modulating the gut microbiota (enhancing Lactobacillus species)'
• Mono-colonization experiments with L. paracasei confirmed this species as a key beneficial anti-UC Lactobacillus species enriched by FSIEVs
• FSIEVs alleviated UC symptoms 'involving the enrichment of beneficial anti-UC Lactobacillus species, L. paracasei by mono-colonization'

FSIEVs promoted tryptophan metabolism and increased production of indole-3-acetic acid (IAA), which was identified as a key mediating metabolite.

• FSIEVs promoted tryptophan metabolism and increased the production of indole-3-acetic acid (IAA)
• Antibiotic treatment, fecal microbiota transplantation (FMT), and intestinal organoid models all confirmed that 'IAA is a key metabolite mediating the anti-UC effects of FSIEVs'
• All three experimental approaches (antibiotic treatment, FMT, intestinal organoids) significantly activated the aryl hydrocarbon receptor (AhR) via IAA

FSIEVs activated the aryl hydrocarbon receptor (AhR), and this activation was confirmed as essential to the anti-UC mechanism.

• AhR activation was demonstrated through multiple experimental approaches including antibiotic treatment, FMT, and intestinal organoid models
• The role of AhR in the anti-UC effects of FSIEVs was 'further validated using AhR antagonists'
• AhR antagonist experiments confirmed that AhR activation is required for the anti-UC effects of FSIEVs

FSIEVs suppressed NLRP3 inflammasome activation and ROS production as downstream effectors of the AhR pathway.

• The mechanism of action involved 'suppressing NLRP3 inflammasome activation and ROS production'
• These effects were downstream of AhR activation mediated by IAA
• Suppression of both NLRP3 inflammasome and ROS contributed to the reduction of intestinal oxidative stress and inflammation

Fecal microbiota transplantation (FMT) experiments confirmed that the gut microbiota changes induced by FSIEVs were causally linked to anti-UC effects.

• FMT was used as one of three experimental approaches to confirm IAA as a key mediating metabolite
• FMT experiments demonstrated transferability of the anti-UC effect through microbiota manipulation
• The FMT findings confirmed that microbiota modulation by FSIEVs, not just direct drug effects, contributed to therapeutic outcomes

Intestinal organoid models were used to validate the role of IAA and AhR activation in the anti-UC effects of FSIEVs.

• Intestinal organoid models were employed alongside antibiotic treatment and FMT to confirm IAA as the key mediating metabolite
• Organoid experiments 'significantly activated the aryl hydrocarbon receptor (AhR)'
• This ex vivo model provided mechanistic confirmation of the FSIEVs' pathway of action independent of whole-animal confounders