Danshen ligustrazine injection ameliorates MCAO/R rats through the AhR-SOCS2 axis in association with gut microbiota-derived tryptophan metabolism

Danshen Ligustrazine Injection (DSLI), composed of the extract of Salvia miltiorrhiza Bunge and Conioselinum anthriscoides 'Chuanxiong', is commonly used in the clinical treatment of ischemic stroke, which is the most common type of cerebrovascular disease, affected by multiple factors. The brain-gut axis is a new type of influencing factor for ischemic stroke, however, there is a lack of systematic research on the relationship between microbiota and host metabolic phenotype. This study aimed to investigate the host metabolic phenotype-microbiome interface in ischemic stroke and the immunomodulatory effects of DSLI. In the study, liquid chromatography-mass spectrometry was used to primarily analyze the quality markers (Q-markers) and the polyphenols of DSLI. Based on 16S rRNA gene sequencing and metabolomics, the variations of microbial composition in different groups were characterized. In addition, a network diagram was constructed to reveal the interrelationship between DSLI-regulated gut microbiota changes and DSLI-regulated brain metabolites in MCAO/R rats. The expression of the aryl hydrocarbon receptor (AhR) in the colon and brain by immunofluorescence and suppressors of cytokine signaling 2 (SOCS2) by western blot were further detected. Diminished metabolic diversity and alterations in the tryptophan metabolism pathway were a feature of IS in the study. The results revealed that Clostri_UCG-014 was positively correlated with indoleacrylic acid, indole-3-methylacetate, and Ruminococcaceae was strongly related with L-tryptophan, 3-methylindole, and indole. The results of immunofluorescence showed that the expression of AhR in the colon and brain tissues of rats in the model group was greatly reduced compared with that in the sham-operated group, and was heavily activated with the treatment of DSLI. The levels of aryl hydrocarbon nuclear receptor ARNT2 and SOCS2 were down-regulated in the brains of Model rats, whereas increased by DSLI, further confirming that the brain-gut microbiota-Trp metabolism exists in the pathological changes of stroke and the intervention mechanism of DSLI. The present study findings suggest Clostri_UCG-014, Ruminococcaceae, and Firmicute_RF39 play an important role in improving the regulation of immune function in stroke through tryptophan metabolites by acting on the AhR-SOCS2 axis.