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

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.

Cross-talk between α-synuclein and the microtubule cytoskeleton in neurodegeneration

Looking at the puzzle that depicts the molecular determinants in neurodegeneration, many pieces are lacking and multiple interconnections among key proteins and intracellular pathways still remain unclear. Here we focus on the concerted action of α-synuclein and the microtubule cytoskeleton, whose interplay, indeed, is emerging but remains largely unexplored in both its physiology and pathology. α-Synuclein is a key protein involved in neurodegeneration, underlying those diseases termed synucleinopathies. Its propensity to interact with other proteins and structures renders the identification of neuronal death trigger extremely difficult. Conversely, the unbalance of microtubule cytoskeleton in terms of structure, dynamics and function is emerging as a point of convergence in neurodegeneration. Interestingly, α-synuclein and microtubules have been shown to interact and mediate cross-talks with other intracellular structures. This is supported by an increasing amount of evidence ranging from their direct interaction to the engagement of in-common partners and culminating with their respective impact on microtubule-dependent neuronal functions. Last, but not least, it is becoming even more clear that α-synuclein and tubulin work synergically towards pathological aggregation, ultimately resulting in neurodegeneration. In this respect, we supply a novel perspective towards the understanding of α-synuclein biology and, most importantly, of the link between α-synuclein with microtubule cytoskeleton and its impact for neurodegeneration and future development of novel therapeutic strategies.

Zfra Inhibits the TRAPPC6AΔ-Initiated Pathway of Neurodegeneration

When WWOX is downregulated in middle age, aggregation of a protein cascade, including TRAPPC6AΔ (TPC6AΔ), TIAF1, and SH3GLB2, may start to occur, and the event lasts more than 30 years, which results in amyloid precursor protein (APP) degradation, amyloid beta (Aβ) generation, and neurodegeneration, as shown in Alzheimer's disease (AD). Here, by treating neuroblastoma SK-N-SH cells with neurotoxin MPP+, upregulation and aggregation of TPC6AΔ, along with aggregation of TIAF1, SH3GLB2, Aβ, and tau, occurred. MPP+ is an inducer of Parkinson's disease (PD), suggesting that TPC6AΔ is a common initiator for AD and PD pathogenesis. Zfra, a 31-amino-acid zinc finger-like WWOX-binding protein, is known to restore memory deficits in 9-month-old triple-transgenic (3xTg) mice by blocking the aggregation of TPC6AΔ, SH3GLB2, tau, and amyloid β, as well as inflammatory NF-κB activation. The Zfra4-10 peptide exerted a strong potency in preventing memory loss during the aging of 3-month-old 3xTg mice up to 9 months, as determined by a novel object recognition task (ORT) and Morris water maize analysis. Compared to age-matched wild type mice, 11-month-old Wwox heterozygous mice exhibited memory loss, and this correlates with pT12-WWOX aggregation in the cortex. Together, aggregation of pT12-WWOX may link to TPC6AΔ aggregation for AD progression, with TPC6AΔ aggregation being a common initiator for AD and PD progression.

Neuroinflammation and Parkinson's Disease-From Neurodegeneration to Therapeutic Opportunities

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder worldwide. Clinically, it is characterized by a progressive degeneration of dopaminergic neurons (DAn), resulting in severe motor complications. Preclinical and clinical studies have indicated that neuroinflammation can play a role in PD pathophysiology, being associated with its onset and progression. Nevertheless, several key points concerning the neuroinflammatory process in PD remain to be answered. Bearing this in mind, in the present review, we cover the impact of neuroinflammation on PD by exploring the role of inflammatory cells (i.e., microglia and astrocytes) and the interconnections between the brain and the peripheral system. Furthermore, we discuss both the innate and adaptive immune responses regarding PD pathology and explore the gut–brain axis communication and its influence on the progression of the disease.