Xiao-Er-An-Shen Granule inhibits dopamine production to ameliorate Tourette syndrome in mice

Background

Tourette syndrome (TS) is a neuropsychiatric disorder that typically manifests in childhood. Currently, anti-psychotic drugs that aim to reduce dopaminergic hyperinnervation in the brain are recommended for TS. These drugs have been proven to increase the risk of extrapyramidal symptoms, which hinder their use. Gut microbiota has been shown to modulate dopamine (Da) metabolism along gut-brain axis and be relevant to the development of TS, and which may be a novel strategy for TS therapy. Xiao-Er-An-Shen Granule (XEASG) is a clinically prescribed herbal mixture that has demonstrated clinical efficacy in treating TS. The detailed mechanism of XEASG in alleviating TS symptoms through the gut-brain axis however remains incompletely understood.

Purpose

This study aimed to investigate the effect of XEASG on TS through regulating Da synthesis both in the brain and gut microbiota.

Methods

XEASG at doses of 2 and 4 g/kg/d was administered orally to 3,3′-iminodipropionitrile (IDPN)-induced TS model mice. Behavioral assessments, targeted metabolomics analysis, 16S rRNA sequencing and enzyme-linkedimmunosorbent assay (ELISA) were employed to elucidate the therapeutic effects and mechanisms of XEASG for TS treatment.

Results

Data showed that XEASG treatment significantly alleviated IDPN-induced tic-like behavior in mice. XEASG significantly reduced Da level in the brain tissues of TS mice, resulting from down-regulated Da synthesis but up-regulated Da degradation. Aberrant Da metabolism was also found in serum and colon contents of TS mice, which was restored by XEASG treatment. Furthermore,16S rRNA sequence revealed that XEASG altered the microbial community composition. Finally, experimental validation confirmed that XEASG suppressed Da synthesis pathway by reducing tyrosine hydroxylase level in the gut microbiota.

Conclusion

Our findings reveal that XEASG alleviates TS via inhibiting Da synthesis in the brain and gut, which suggests that the regulation of Da through gut microbiota by XEASG could be a therapeutic strategy for TS treatment.