Safranal exerts a neuroprotective effect on Parkinson's disease with suppression of NLRP3 inflammation activation

Abstract

Background: Parkinson's disease (PD) is a common central nervous system neurodegenerative disease. Neuroinflammation is one of the significant neuropathological hallmarks. As a traditional Chinese medicine, Safranal exerts anti-inflammatory effects in various diseases, however, whether it plays a similar effect on PD is still unclear. The study was to investigate the effects and mechanism of Safranal on PD.

Methods: The PD mouse model was established by 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine MPTP firstly. Next, the degree of muscle stiffness, neuromuscular function, motor retardation and motor coordination ability were examined by observing and testing mouse movement behavior. Immunofluorescence staining was used to observe the expression of tyrosine hydroxylase (TH). The dopamine (DA) content of the striatum was detected by High-performance liquid chromatography (HPLC). The expression of TH and NLRP3 inflammasome-related markers NLRP3, IL-1β, and Capase-1 were detected by Real-time Polymerase Chain Reaction (qRT-PCR) and western blotting (WB) respectively.

Results: Through behavioral testing, Parkinson's mouse showed a higher muscle stiffness and neuromuscular tension, a more motor retardation and activity disorders, together with a worse motor coordination compared with sham group. Simultaneously, DA content and TH expression in the striatum were decreased. However, after using Safranal treatment, the above pathological symptoms of Parkinson's mouse all improved compared with Safranal untreated group, the DA content and TH expression were also increased to varying degrees. Surprisingly, it observed a suppression of NLRP3 inflammation in the striatum of Parkinson's mouse.

Conclusions: Safranal played a neuroprotective effect on the Parkinson's disease and its mechanism was related to the inhibition of NLRP3 inflammasome activation.

Keywords: NLRP3; Neuroprotective; Parkinson’s disease; Safranal.

Fig. 1

The Parkinson’s mouse model was successfully constructed using the MPTP method. A Stiffness was assessed by the Catalepsy test. The graph shows the time of the movement of the hind limb to the surface. B Neuromuscular tension is tested through grip strength. C Passive movement was assessed with a rotarod, and the graph shows the residence time on the rotating rod. D Adaptive exercise was assessed with a pole climbing test, and the graph shows the time to turn around and climb down. E-H Walking track analysis of the swing speed and stride length of the forelimbs and hindlimbs. I Spontaneous movement was assessed with the open field test, and the graph shows the movement time (n = 8, ^*P < 0.05). J Dopamine (DA) content in the striatum in the Sham and MPTP-treated groups. K TH (tyrosine hydroxylase) protein expression in the striatum in the Sham and MPTP-treated groups. L Quantitative analysis of TH protein expression. M mRNA expression of TH in the striatum in the Sham and MPTP-treated groups. N Immunofluorescence staining of Striatum in two groups of mice. The magnification is 200 times, and the scale is 50 μm. O The mean fluorescence density analysis (n = 6, ^*P < 0.05)

Fig. 2

The expression of the NLRP inflammasome-related markers NLRP3, IL-1β, and Capase-1 in the Striatum. A NLRP3, IL-1β, and Capase-1 protein expression. B Quantitative analysis of NLRP3, IL-1β, and Capase-1 protein expression. CNLRP3, IL-1β, and Capase-1 mRNA expression (n = 6, ^*P < 0.05, ^#P < 0.05, ^†P < 0.05). Data are expressed as the mean ± SD

Fig. 3

Safranal ameliorated motor deficits of the Parkinson’s mouse A Stiffness was assessed by the Catalepsy test, and the graph shows the time of the movement of the hind limb to the surface. B Neuromuscular tension is tested through grip strength. C Spontaneous movement was assessed with the open field test. The graph shows the movement time. D Adaptive exercise was assessed with the pole climbing test, and the graph shows the time to turn around and climb down. E Passive movement was assessed with a rotarod, and the graph shows the residence time on the rotating rod. F, G, H, I Walking track analysis of the swing speed and stride length of the forelimbs and hindlimbs. Data are expressed as the Mean ± SD. (n = 8, ^*P < 0.05, ^#P < 0.05)

Fig. 4

Safranal increased the DA and TH content in the Parkinson’s disease mouse A TH protein expression in each group. B Quantitative analysis of TH protein expression. C the mRNA expression of TH in each group. D DA content in each group. E, F Immunofluorescence staining of Striatum in each group. The magnification is 200 times, and the scale is 50 μm. Data are expressed as the Mean ± SD. (n = 6, ^*P < 0.05, ^#P < 0.05)

Fig. 5

NLRP3 inflammasome were inhibited after using Safranal treatment in Parkinson’s disease mouse. A NLRP3, IL-1β, and Capase-1 protein expression level. B Quantitative analysis of NLRP3 protein expression level. C Quantitative analysis of IL-1β protein expression level. D Quantitative analysis of Capase-1 protein expression. EIL-1β mRNA expression level. FCapase-1 mRNA expression level. GNLRP3 mRNA expression level. Data are expressed as the mean ± SD. (n = 6, ^*P < 0.05, ^#P < 0.05)