The primary neuronal cells are more resistant than PC12 cells to α-synuclein toxic aggregates.

BACKGROUND: Alpha-synuclein (αSN) is an abundant presynaptic brain protein that its aggregated species believed to play pivotal roles in the development of neurodegenerative diseases, especially Parkinson's disease (PD). In this study, we compared the response of primary neuronal cells with a well-known cell line model, PC12, against the toxic aggregates of αSN. METHODS: Primary hippocampal neurons (PHNs) were isolated from 17 to 18 days old rat embryos. Fibrillization was induced in recombinant αSN and monitored by standard methods. The toxicity of different aggregates of αSN on the treated cells was then studied. Furthermore, changes in the intracellular reactive oxygen species (ROS) and Ca2+ levels were also compared in two kinds of treated cells. We also studied the gene expression profile of certain Ca2+ channels and carriers using the GEO2 database. RESULTS: The viability rate was significantly lower in PC12 versus PHNs, in response to αSN. This is while the intracellular ROS and Ca2+ levels were significantly increased in both cell types. Analysis of microarray data indicated that some factors involved in Ca2+ hemostasis may face significant changes in the PD condition. CONCLUSION: By putting these data together, it is clear that PHN is more resistant than PC12 toward αSN cytotoxicity even in the presence of rising cytoplasmic ROS and Ca2+ levels. Exploring the supporting mechanisms which PHN uses to be more resistant to αSN cytotoxicity can help to open a roadmap toward therapeutic plans in PD and other synucleinopathy disorders.

Four-repeat tauopathies.

Tau is a microtubule-associated protein with versatile functions in the dynamic assembly of the neuronal cytoskeleton. Four-repeat (4R-) tauopathies are a group of neurodegenerative diseases defined by cytoplasmic inclusions predominantly composed of tau protein isoforms with four microtubule-binding domains. Progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease or glial globular tauopathy belong to the group of 4R-tauopathies. The present review provides an introduction in the current concept of 4R-tauopathies, including an overview of the neuropathological and clinical spectrum of these diseases. It describes the genetic and environmental etiological factors, as well as the contemporary knowledge about the pathophysiological mechanisms, including post-translational modifications, aggregation and fragmentation of tau, as well as the role of protein degradation mechanisms. Furthermore, current theories about disease propagation are discussed, involving different extracellular tau species and their cellular release and uptake mechanisms. Finally, molecular diagnostic tools for 4R-tauopathies, including tau-PET and fluid biomarkers, and investigational therapeutic strategies are presented. In summary, we report on 4R-tauopathies as overarching disease concept based on a shared pathophysiological concept, and highlight the challenges and opportunities on the way towards a causal therapy.

Formulation and anti-neurotoxic activity of baicalein-incorporating neutral nanoliposome.

Despite extensive studies of the effects of herbal-derived small molecules in the biopharmaceutical and biomedical sciences, their low solubility and stability remain a challenge. Here we focus on baicalein, a small molecule showing potential against neurodegenerative diseases such as Parkinson's and Alzheimer's. However, therapeutic usage in vivo is challenged by low solubility and stability. To address this we have applied neutrally-charged nanoliposome (NLP) as carrier for baicalein. Baicalein was incorporated into NLP to form NLP-Ba at molar baicalain:lipid ratios of up to 1:3, giving a drug entrapment efficiency of 96.71%, slow release of approximately 22% after a week and increased baicalein stability up to 27%. Ascorbic acid increased baicalein's stability further, particularly when incorporated in NLP where baicalein stability intensified by 53% in NLP-Ba. Moreover, NLP-Ba did not show significant cytotoxic effects against neurons; rather, showed considerable protective effect against reactive oxygen species. In addition, NLP promoted internalization of baicalein into cells, showing good biocompatibility. We conclude that NLP-Ba can enhance baicalein's therapeutic potential in neurodegenerative diseases.

The potential of zwitterionic nanoliposomes against neurotoxic alpha-synuclein aggregates in Parkinson's Disease.

The protein α-synuclein (αSN) aggregates to form fibrils in neuronal cells of Parkinson's patients. Here we report on the effect of neutral (zwitterionic) nanoliposomes (NLPs), supplemented with cholesterol (NLP-Chol) and decorated with PEG (NLP-Chol-PEG), on αSN aggregation and neurotoxicity. Both NLPs retard αSN fibrillization in a concentration-independent fashion. They do so largely by increasing lag time (formation of fibrillization nuclei) rather than elongation (extension of existing nuclei). Interactions between neutral NLPs and αSN may locate to the N-terminus of the protein. This interaction can even perturb the interaction of αSN with negatively charged NLPs which induces an α-helical structure in αSN. This interaction was found to occur throughout the fibrillization process. Both NLP-Chol and NLP-Chol-PEG were shown to be biocompatible in vitro, and to reduce αSN neurotoxicity and reactive oxygen species (ROS) levels with no influence on intracellular calcium in neuronal cells, emphasizing a prospective role for NLPs in reducing αSN pathogenicity in vivo as well as utility as a vehicle for drug delivery.

Cuminaldehyde as the Major Component of Cuminum cyminum, a Natural Aldehyde with Inhibitory Effect on Alpha-Synuclein Fibrillation and Cytotoxicity.

Fibrillation of alpha-synuclein (α-SN) is a critical process in the pathophysiology of several neurodegenerative diseases, especially Parkinson's disease. Application of bioactive inhibitory compounds from herbal extracts is a potential therapeutic approach for this cytotoxic process. Here, we investigated the inhibitory effects of the Iranian Cuminum cyminum essential oil on the fibrillation of α-SN. Analysis of different fractions from the total extract identified cuminaldehyde as the active compound involved in the antifibrillation activity. In comparison with baicalein, a well-known inhibitor of α-SN fibrillation, cuminaldehyde showed the same activity in some aspects and a different activity on other parameters influencing α-SN fibrillation. The presence of spermidine, an α-SN fibrillation inducer, dominantly enforced the inhibitory effects of cuminaldehyde even more intensively than baicalein. Furthermore, the results from experiments using preformed fibrils and monobromobimane-labeled monomeric protein also suggest that cuminaldehyde prevents α-SN fibrillation even in the presence of seeds, having no disaggregating impact on the preformed fibrils. Structural studies showed that cuminaldehyde stalls protein assembly into ß-structural fibrils, which might be achieved by the interaction with amine groups through its aldehyde group as a Schiff base reaction. This assumption was supported by FITC labeling efficiency assay. In addition, cytotoxicity assays on PC12 cells showed that cuminaldehyde is a nontoxic compound, treatment with cuminaldehyde throughout α-SN fibrillation showed no toxic effects on the cells. Taken together, these results show for the first time that the small abundant natural compound, cuminaldehyde, can modulate α-SN fibrillation. Hence, suggesting that such natural active aldehyde could have potential therapeutic applications.

Alpha-Synuclein Fibrils Interact with Dopamine Reducing its Cytotoxicity on PC12 Cells.

Aggregated alpha-synuclein (α-SYN) is the major component of Lewy bodies and Lewy neurites, two of the pathological hallmarks of Parkinson's disease (PD). Aggregation of α-SYN leads to toxic species involved in the degeneration of dopaminergic neurons in the midbrain. Different studies suggest a strong association between the presence of dopamine (DA) and the cell specific degeneration caused by α-SYN aggregates in PD. Despite extensive studies on the effect of DA on α-SYN fibrillation, it remains unclear how the simultaneous presence of DA and α-SYN influences the degeneration of dopaminergic neurons. In this study we show that separate treatments with specific doses of DA or early stage α-SYN aggregates (ESAA) are both cytotoxic to PC12 cells. Surprisingly, simultaneous treatment of cells with DA and ESAA significantly decreased this toxicity. This cytotoxicity was further reduced by the presence of heavier particles of α-SYN aggregates with more fibrillogenic characteristics. Spectrometric analysis revealed that α-SYN fibrils interact with DA even after the sample was dialyzed for 48 h, suggesting a strong interaction. Interestingly, digestion of unprotected N- and C-α-SYN-fibril terminals by proteinase K did not affect this interaction. Our results suggest that fibrillar forms of α-SYN with localized expanded active surfaces may interact with DA and moderate its cytotoxicity. Thus, highlighting the importance of fibrillar proteins in developing clinical approaches for amyloid diseases.