Methylene blue alleviates dopaminergic neuronal pyroptosis to improve motor dysfunction in Parkinson's disease mouse models / 中华神经医学杂志

ABSTRACT

Objective:To investigate the effect of methylene blue (MB) on motor dysfunction and its mechanism in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse models.Methods:Forty healthy male C57BL/6 mice were randomly divided into 4 groups: control group, model group, low-dose treatment group and medium-dose treatment group ( n=10); PD mouse models were established by intraperitoneal injection of 25 mg/kg/d MPTP for a consecutive 7 d; low-dose treatment group and medium-dose treatment group were pretreated intraperitoneally with MB 2 mg/kg/d or MB 10 mg/kg/d for a consecutive 3 d, respectively; and then, MPTP 25 mg/kg/d+MB 2 mg/kg/d or MPTP 25 mg/kg/d+MB 10 mg/kg/d were injected intraperitoneally into the low-dose treatment group or medium-dose treatment group for a consecutive 7 d (MPTP and MB were given at 12 h of interval). Eight d after modeling, open field experiment, pole climbing experiment and rod rotating experiment were carried out to evaluate the spontaneous movement, coordination, endurance and motor ability. And then, the mice were sacrificed; immunofluorescent staining was used to observe tyrosine hydroxylase (TH) expression in the substantia nigra; Western blotting was used to detect the expressions of TH, α-synuclein, nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), cleaved-Caspase-1 and Gasdermin D (GSDMD) in the striatum and substantia nigra of mice. Contents of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-18 in the substantia nigra and striatum of mice were detected by ELISA. Results:Compared with the control group, the model group had shortened residence time in rod rotating, prolonged descent time in rod climbing, reduced total movement distance in open field, decreased number of TH-positive cells in the substania nigra, decreased TH protein levels in the substania nigra and striatum, and increased NLRP3, ASC, cleaved-Caspase-1, GSDMD and GSDMD-N protein levels in the substania nigra and striatum, and increased TNF-α, IL-1β and IL-18 contents in the substania nigra and striatum, with significant differences ( P<0.05). Compared with the model group, low-dose treatment group and medium-dose treatment group had prolonged residence time in rod rotating, shortened descent time in rod climbing, increased total movement distance in open field, increased number of TH-positive cells in the substania nigra, and increased TH protein levels in the substania nigra and striatum, decreased NLRP3, ASC, and cleaved-Caspase-1 levels in the substania nigra and striatum, and decreased TNF-α, IL-1β and IL-18 contents in the substania nigra and striatum, with significant differences ( P<0.05). No statistical differences in the above indexes were noted between the low-dose treatment group and medium-dose treatment group ( P>0.05). Conclusion:Low-/medium-dose MB can ameliorate motor dysfunction in PD mouse models, whose mechanism may be related to downregulate NLRP3 inflammasome and inhibit neuroinflammatory response to reduce dopaminergic neuron pyroptosis.