Jing An decoction alleviates neuroinflammation in Tourette syndrome by regulating butyrate-mediated microbiota-gut-brain axis.

Background: Jing An decoction (JA), a traditional Chinese medicine formulation, has demonstrated notable clinical efficacy in the treatment of Tourette syndrome (TS) over the past two decades. The gut-brain axis (GBA) critically regulates neuroinflammation and neurodevelopmental processes, suggesting its potential as a therapeutic target in TS. However, the mechanisms by which JA alleviates TS via the GBA remain unclear.

Purpose: This study investigated gut microbiota and its metabolites to explore the potential mechanisms by which JA alleviates TS, a chronic neurodevelopmental disorder.

Methods: A TS rat model was established via intraperitoneal injection of 3,3'-iminodipropionitrile (IDPN). Behavioral assessments, including stereotyped behavior, motor behavior, open-field testing, and novel object recognition, were conducted to evaluate the effect of JA. Gut microbiota was assessed by 16S rRNA sequencing, while short-chain fatty acids were quantified via GC-MS. Inflammatory cytokine levels were measured using ELISA. Gene expression related to tight junctions, key bacterial taxa, and metabolic enzymes was quantified using qPCR. Immunohistochemistry, immunofluorescence, and western blotting were employed to evaluate microglial polarization, barrier integrity, and the expression of key signaling pathway proteins. Additionally, an LPS-induced primary microglial inflammation model was used to investigate the role of butyrate in regulating microglia-mediated neuroinflammation.

Results: JA significantly reduced stereotypic behaviors, hyperactivity, and cognitive impairments in TS rats. It restored gut microbiota diversity by increasing the abundance of butyrate-producing bacteria-particularly the Lachnospiraceae NK4A136 group-and upregulating the expression of butyrate-metabolizing enzymes (Buk and ButCOA). Butyrate levels in the colon and striatum were elevated in JA-treated rats, correlating with reduced neuroinflammation and enhanced intestinal and blood-brain barrier integrity. JA promoted M2 microglial polarization, suppressed HDAC3 expression, and inhibited the TLR4/NF-κB pathway. In primary microglial cells, butyrate attenuated LPS-induced neuroinflammation-an effect comparable to that of TLR4/NF-κB inhibitors (TAK-242, PDTC)-but this effect was reversed by an MCT1 inhibitor and HDAC3 activator (AZD3965, ITSA-1).

Conclusions: JA alleviates TS by regulating the GBA axis through butyrate-producing bacteria. Butyrate alleviates neuroinflammation by inhibiting the TLR4/HDAC3/NF-κB pathway, thereby promoting M2 microglial polarization.