Revealing the enhancing mechanism and material basis of bile-processed Coptidis Rhizoma in anti-anxiety from perspective of cross organ regulation.

ETHNOPHARMACOLOGICAL RELEVANCE: Coptidis Rhizoma (CR) is a typical cold-attribute herb with potential anti-anxiety properties. Bile is of cold nature and can also interfere with the central nervous system. Bile-processed CR (BCR) exhibits synergistically enhanced anti-anxiety performance. However, the underlying mechanism and material basis for this synergism are not clear.

AIM OF THE STUDY: To decipher the enhanced anti-anxiety mechanism and material basis of BCR from the perspective of cross-organ regulation.

METHODS: A rat model of anxiety with sthenic heat syndrome was established to systematically evaluate the enhanced anti-anxiety efficacy of BCR in terms of anxiety behaviour, liver metabolism, and histopathology. Subsequently, the gut microbiome sequencing and untargeted metabolomics of the brain, liver, and serum were performed to explore the mechanism of BCR and CR in regulating the gut-liver-brain axis. In vivo and in vitro molecular biology experiments were performed to further clarify the mechanisms underlying the differential efficacy of BCR and CR. Finally, supramolecular self-assembly simulation and tissue distribution in target organs were carried out to predict the material basis for the enhanced efficacy of BCR.

RESULTS: BCR performed better than CR in improving the anxiety behaviour and liver metabolism and in alleviating cerebral injury in the rat model of anxiety. The results of gut microbiome and metabolomic analyses indicated that BCR was superior to CR in reshaping the gut microbiota composition and correcting the metabolic disorders in the brain, liver, and serum. Mechanistically, multiomic analysis revealed that BCR and CR (especially BCR) could block the TLR4/NF-κB pathway in the colon, attenuate hepatic inflammation, improve the integrity of the intestinal mucosa and blood-brain barrier, and inhibit the NLRP3/Caspase-1/IL-1β pathway in the brain, thereby blocking the transmission of inflammation along the gut-liver-brain axis and exerting anti-anxiety effects. BCR and CR (particularly BCR) could suppress the overactivation of ammonia-induced MAPK/NF-κB/iNOS pathway and overexpression of glutamine synthetase in the brain, consequently maintaining the normal morphology and glutamate uptake function (GLAST and GLT-1 activities) of astrocytes, alleviating neuronal apoptosis caused by glutamate excitotoxicity (GluN2B), and ultimately blocking the transmission of neurotoxicity along the gut-liver-brain axis to relieve anxiety. The alkaloid-bile acid supramolecules assembled during the decoction of BCR enabled more alkaloids and bile acids to be distributed in the brain and liver, providing material support for the enhanced effect of BCR.

CONCLUSIONS: BCR was superior to CR in blocking the transmission of inflammation and neurotoxic substances along the gut-liver-brain axis and, hence, exerted stronger efficacy in alleviating neuroinflammation and improving neuronal survival in the rat model of anxiety. The alkaloid-bile acid supramolecules may provide the material foundation. This study fully considers the characteristic of traditional Chinese medicine being able to exert therapeutic effects through multiple pathways, providing novel avenues for research on the processing mechanism.