Abstract
OBJECTIVES: To investigate the mechanism by which Acorus tatarinowii Schott volatile oil (VOA) alleviates tic disorder (TD) in rats. METHODS: Forty-eight 3-week-old SD rats were randomly divided into blank group (n=8) and TD model group with intraperitoneal injection of iminodipropionitrile (n=40). The rat models were further randomized into 5 groups (n=8) for treatment with daily gavage of saline (model group), tiapride (47.91 mg/kg) or VOA (51.12 mg/kg), intraperitoneal injection of TAK-242 (a TLR4 inhibitor; 3 mg/kg), or both VOA gavage and TAK242 injection for 28 days. Behavioral changes of the rats were assessed, and Nissl staining was used to observe neuronal morphology in the striatum. The levels of TNF-α, C1q, TGF-β, and VEGF in the serum and striatum were measured using ELISA. The mRNA and protein expressions of TLR4, MyD88, and NF‑κB p65 in the striatum were detected using RT-PCR and Western blotting, and NF‑κB p65 nuclear translocation and expressions of Iba1 (a MG-specific marker), CD86 and CD206 were analyzed using immunofluorescence staining. RESULTS: VOA treatment significantly reduced tic-like behavior scores and ameliorated striatal neuronal damage in the rat models, resulting also in lowered levels of TNF-α and C1q and increased levels of TGF-β and VEGF in both the serum and striatum, decreased mRNA and protein expression levels of TLR4, MyD88, and NF‑κB p65 in the striatum, and reduced nuclear translocation of NF‑κB p65. Immunofluorescence staining revealed significantly weakened expressions of Iba1 and CD86 and enhanced CD206 expression in the striatum of VOA-treated rats. All these ameliorative effects of VOA were significantly attenuated by treatment with TAK-242. CONCLUSIONS: VOA alleviates tic symptoms in rats by inhibiting microglia activation and polarization to reduce neuroinflammation possibly through suppression of the TLR4/MyD88/NF-κB signaling pathway.