Electroacupuncture inhibits pyroptosis to improve motor function in an MPTP-induced mouse model of Parkinson's disease.

Abstract

Objectives: To investigate whether electroacupuncture (EA) ameliorates motor dysfunction and protects nigrostriatal dopaminergic neurons in Parkinson's disease (PD) mice by inhibiting NLRP3 inflammasome-mediated pyroptosis.

Methods: Male C57BL/6 mice were randomly assigned before model induction to seven groups: saline-treated control, MPTP model, MPTP plus EA, MPTP plus Nigericin, MPTP plus EA and Nigericin, MPTP plus MCC950, and MPTP plus EA and MCC950 groups. Mice in the control group received equal-volume saline, whereas mice in the other six groups were administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 30 mg/kg, intraperitoneally) once daily for five consecutive days. Following model induction, EA was applied at Baihui (GV20) and Dazhui (GV14) at 100 Hz for 20 min per session over 14 days. Nigericin and MCC950 were used as an NLRP3 inflammasome activator and inhibitor, respectively. Motor function was assessed using the open-field and pole tests. Dopaminergic neuronal integrity, neuronal injury, microglial activation, and the cellular localization of NLRP3 were evaluated using immunohistochemistry, hematoxylin-eosin staining, and immunofluorescence. The expression levels of tyrosine hydroxylase, NLRP3, ASC, Caspase-1, and the N-terminal fragment of gasdermin D (GSDMD-N) were determined using immunofluorescence and western blotting.

Results: EA alleviated abnormal open-field hyperlocomotion and prolonged pole-descent latency in MPTP-treated mice, preserved tyrosine hydroxylase-positive dopaminergic neurons in the substantia nigra, restored striatal tyrosine hydroxylase expression, and reduced neuronal injury and microglial activation. NLRP3 was predominantly colocalized with tyrosine hydroxylase-positive dopaminergic neurons, whereas limited colocalization was observed with IBA-1-positive microglia. Electroacupuncture significantly suppressed the MPTP-induced upregulation of NLRP3, ASC, Caspase-1, and GSDMD-N. Nigericin exacerbated motor abnormalities, nigrostriatal injury, and pyroptosis-related signaling and largely abolished the protective effects of EA. Conversely, MCC950 produced protective effects comparable to those of EA, whereas their combined administration provided no significant additional benefit.

Conclusion: EA improves motor dysfunction and protects the nigrostriatal dopaminergic system in MPTP-induced PD mice, at least partly by suppressing NLRP3 inflammasome-mediated pyroptosis in dopaminergic neurons. These findings identify the NLRP3 inflammasome as an important mechanistic target underlying the neuroprotective effects of electroacupuncture in experimental PD.