Echinacoside exerts neuroprotection via suppressing microglial α-synuclein/TLR2/NF-κB/NLRP3 axis in parkinsonian models.

BACKGROUND: Echinacoside (ECH), a natural active compound, was found to exert neuroprotection in Parkinson's disease (PD). However, the underlying molecular mechanisms remain controversial. PURPOSE: This study aimed to explore the roles of ECH in PD and its engaged mechanisms. CONCLUSION: In vivo, MPTP was adapted to construct subacute PD mouse model to explore the regulation of ECH on NLRP3 inflammasome. In vitro, α-synuclein (α-syn)/MPP+ was used to mediate the activation of NLRP3 inflammasome in BV2 cells, and the mechanism of ECH regulation of it was explored with molecular docking, immunofluorescence, Western blotting, and small molecule inhibitors. CONCLUSION: The activation of microglial NLRP3 inflammasome could be evoked by MPTP in vitro, but its toxic metabolite MPP+ alone cannot trigger the activation of NLRP3 inflammasome in vitro, which requires α-synuclein (α-syn) priming. Exogenous α-syn could evoke microglial TLR2/NF-κB/NLRP3 axis, playing the priming role in MPP+ -mediated NLRP3 inflammasome activation. ECH can suppress the upregulation of α-syn in MPTP-treated mice and BV2 microglia. It can also suppress the activation of the TLR2/NF-κB/NLRP3 axis induced by α-syn. CONCLUSION: ECH exerts neuroprotective effects by downregulating the TLR2/NF-κB/NLRP3 axis via reducing the expression of α-syn in the PD models.

Baicalin exerts neuroprotective actions by regulating the Nrf2-NLRP3 axis in toxin-induced models of Parkinson's disease.

Baicalin, a potent anti-oxidative and anti-inflammatory flavonoid compound derived from Scutellaria baicalensis, has emerged as a neuroprotective agent. However, the mechanisms by which baicalin is neuroprotective in Parkinson's disease (PD) remain unclear. In this research, α-syn/MPP+ and MPTP were used to establish PD models in BV2 cells and C57BL/6 mice, respectively. The effect and mechanism of action of baicalin in PD were investigated by Western blotting, RT-qPCR, ELISA, Immunohistochemistry (IHC) staining, Immunofluorescence (IF) staining, HPLC and methods. Results demonstrate that baicalin mitigates oxidative stress, microglia activation and inflammatory response caused by α-syn/MPP+ and MPTP. It protects against dopaminergic neuron loss and relieves motor deficits. Meanwhile, baicalin not only significantly up-regulates the expression of Nrf2 and its downstream antioxidant enzyme, but also suppresses the activation of NLRP3 inflammasome simultaneously. Notably, the beneficial effects of baicalin in PD treatment are blocked by Nrf2 knockdown. This research reveals that baicalin may exert neuroprotective effects in PD treatment by suppressing the activation of NLRP3 inflammasome and it is dependent on the Nrf2-mediated antioxidative response.

Echinacoside Protects Dopaminergic Neurons Through Regulating IL-6/JAK2/STAT3 Pathway in Parkinson's Disease Model.

Echinacoside (ECH), the major active constituent of Cistanche deserticola, was found to exert neuroprotection through neurotrophic and anti-inflammatory functions in Parkinson's disease (PD) models. However, a clear intermediate molecule or pathway that unifies these two effects has to be found. In this study, our results demonstrate that ECH can protect DA neurons in PD mice with Western blot and immunohistochemistry staining. The quantitative real-time polymerase chain reaction was adapted to confirm its anti-inflammatory function with decreased cytokines (interleukin- (IL-) 6, IL-1ß, and TNF-α) in PD mice and LPS-induced BV2 cells. Further studies found that ECH inhibited the IL-6/JAK2/STAT3 pathway and decreased phosphorylation of STAT3 on tyr705 by Western blot. It can also increase p-STAT3 (ser727) and brain-derived neurotrophic factor (BDNF) expression in PD mice and LPS-induced BV2 cells. This study revealed that ECH exerts neurotrophic and anti-inflammatory effects by regulating the IL-6/JAK2/STAT3 pathway and the phosphorylation of STAT3, promoting the mutually beneficial influence of the two effects to maximize its neuroprotective function.

Alpha-synuclein/MPP+ mediated activation of NLRP3 inflammasome through microtubule-driven mitochondrial perinuclear transport.

1- methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can activate nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 3 (NLRP3) inflammasome in Parkinson's disease (PD) mice, while 1-methyl-4-phenyl- 1, 2, 3, 6-tetrahydropyridinium ion (MPP+), the toxic metabolite of MPTP was not enough to achieve it in vitro. We hypothesized that the accumulation of Alpha-synuclein (α-syn) caused by MPP+ can be a priming signal of MPP+ mediated NLRP3 activation, and its mechanism was explored. This study demonstrated the α-syn can mediate NLRP3 priming in BV2 cells. It can also act on ERK-p67phox-nicotinamide adenine dinucleotide phosphate oxidase 2 (Nox2) axis and induce mitochondrial damage. The co-treatment of α-syn/MPP+ can cause aberrant mitochondrial homeostasis to diminish the concentration of the coenzyme nicotinamide adenine dinucleotide (NAD+), mediate accumulation of ac-α-tubulin, and induce mitochondrial perinuclear aggregation, navigating the co-localization of NLRP3 and apoptosis-associated speck-like protein containing a CARD domain (ASC). This study suggested that α-syn/MPP+ mediated NLRP3 inflammasome activation through microtubule-driven mitochondrial perinuclear transport.

Plasma neurofilament light chain levels in Alzheimer's disease.

Plasma neurofilament light (NFL) levels may be a marker of neuronal injury. We examined whether plasma NFL might be a potential biomarker for the prodromal and dementia stages of AD. Participants included 193 cognitively normal (CN), 198 amnestic mild cognitive impairment (aMCI) and 187 Alzheimer's disease (AD) individuals enrolled in the Alzheimer's Disease Neuroimaging Initiative (ADNI). Plasma NFL levels were examined by the Single Molecule array (Simoa) technique. Our results showed significantly increased plasma NFL levels in both AD (50.9pg/ml) and aMCI (43.0pg/ml) groups compared to CN (34.7pg/ml) group (both p<0.001), but with substantial overlap between the groups. Plasma NFL levels in AD group was also markedly increased, compared with aMCI group (p<0.001). Plasma NFL levels were positively associated with age (r=0.355, p<0.001) and negatively with global cognition (r=-0.355, p<0.001) in all subjects. Our results suggest that plasma NFL levels may not be a useful biomarker for the diagnosis of prodromal and dementia stages of AD.

Iron Deposition Leads to Neuronal α-Synuclein Pathology by Inducing Autophagy Dysfunction.

Growing evidence has indicated that iron deposition in the substantia nigra plays an important role in Parkinson's disease (PD). However, the underlying mechanism is still elusive. Using primary dopaminergic neurons and SH-SY5Y cells cultured in vitro, we observed that iron loading increased α-synuclein and reactive oxygen species (ROS) levels in these cells but did not affect the intracellular α-synuclein mRNA levels. Furthermore, iron loading significantly downregulated Beclin-1 levels and decreased the ratio of microtubule-associated protein 1 light chain 3 isoforms (LC3 II/LC3 I). However, a significant change in the levels of autophagy-related gene 5 (Atg5) was not observed in either neurons or SH-SY5Y cells after iron treatment. After treatment with rapamycin, the iron loading-induced increase in the α-synuclein level was significantly reversed and ROS generation was alleviated in both cultured neurons and SH-SY5Y cells. These results indicate that the inhibition of autophagy is critical for the pathological alterations in α-synuclein induced by iron loading. Moreover, treatment with vitamin E did not affect the increase in the α-synuclein levels but significantly eliminated the iron-induced ROS production. Together, our study shows that autophagy dysfunction contributes to iron-induced α-synuclein pathology.