Intraneuronal α-synuclein (α-Syn) aggregates known as Lewy bodies (LBs) and the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) are the pathological hallmarks of Parkinson’s disease (PD). Braak’s hypothesis based on autopsy studies suggests that Lewy pathology initially occurs in the enteric nervous system (ENS) and then travels retrogradely to the dorsal motor nucleus of the vagus nerve (dmX), proceeding from there in a caudo-rostral direction. Recent evidence that α-Syn aggregates propagate between interconnected neurons supports this hypothesis. However, there is no direct evidence demonstrating this transmission from the ENS to the dmX and then to the SNpc. We inoculated α-Syn preformed fibrils (PFFs) or phosphate-buffered saline (PBS) into the mouse gastric wall and analyzed the progression of the pathology. The mice inoculated with α-Syn PFFs, but not with PBS, developed phosphorylated α-Syn (p-α-Syn)–positive LB-like aggregates in the dmX at 45 days postinoculation. This aggregate formation was completely abolished when vagotomy was performed prior to inoculation of α-Syn PFFs, suggesting that the aggregates in the dmX were retrogradely induced via the vagus nerve. Unexpectedly, the number of neurons containing p-α-Syn–positive aggregates in the dmX decreased over time, and no further caudo-rostral propagation beyond the dmX was observed up to 12 months postinoculation. P-α-Syn–positive aggregates were also present in the myenteric plexus at 12 months postinoculation. However, unlike in patients with PD, there was no cell-type specificity in neurons containing those aggregates in this model. Conclusions: These results indicate that α-Syn PFF inoculation into the mouse gastrointestinal tract can induce α-Syn pathology resembling that of very early PD, but other factors are apparently required if further progression of PD pathology is to be replicated in this animal model.

The application of marine resources, instead of fossil fuels, for biomass production is important for building a sustainable society. Seaweed is valuable as a source of marine biomass for producing biofuels such as ethanol, and can be used in various fields. Alginate is an anionic polysaccharide that forms the main component of brown algae. Various alginate lyases (e.g. exo- and endo-types and oligoalginate lyase) are generally used to degrade alginate. We herein describe a novel alginate lyase, AlgC-PL7, which belongs to the polysaccharide lyase 7 family. AlgC-PL7 was isolated from the halophilic Gram-negative bacterium Cobetia sp. NAP1 collected from the brown algae Padina arborescens Holmes. The optimal temperature and pH for AlgC-PL7 activity were 45 °C and 8, respectively. Additionally, AlgC-PL7 was thermostable and salt-tolerant, exhibited broad substrate specificity, and degraded alginate into monosaccharides. Therefore, AlgC-PL7 is a promising enzyme for the production of biofuels.

Alginate, which is an anionic polysaccharide, is widely distributed in the cell wall of brown algae. Alginate and the products of its degradation (oligosaccharides) are used in stabilizers, thickeners and gelling agents, especially in the food industry. The degradation of alginate generally involves a combination of several alginate lyases (exo-type, endo-type and oligoalginate lyase). Enhancing the efficiency of the production of alginate degradation products may require the identification of novel alginate lyases with unique characteristics. In this study, we isolated an alginate-utilizing bacterium, Shewanella sp. YH1, from seawater collected off the coast of Tottori prefecture, Japan. The detected novel alginate lyase was named AlgSI-PL7, and was classified in polysaccharide lyase family 7. The enzyme was purified from Shewanella sp. YH1 and a recombinant AlgSI-PL7 was produced in Escherichia coli. The optimal temperature and pH for enzyme activity were around 45°C and 8, respectively. Interestingly, we observed that AlgSI-PL7 was not thermotolerant, but could refold to its active form following an almost complete denaturation at approximately 60°C. Moreover, the degradation of alginate by AlgSI-PL7 produced two to five oligosaccharides, implying this enzyme was an endo-type lyase. Our findings suggest that AlgSI-PL7 may be useful as an industrial enzyme.

Polysaccharides from seaweeds are widely used in various fields, including the food, biomedical material, cosmetic, and biofuel industries. Alginate, which is a major polysaccharide in brown algae, and the products of its degradation (oligosaccharides) have been used in stabilizers, thickeners, and gelling agents, especially in the food industry. Discovering novel alginate lyases with unique characteristics for the efficient production of oligosaccharides may be relevant for the food and pharmaceutical fields. In this study, we identified a unique alginate lyase derived from an alginate-utilizing bacterium, Shewanella species YH1. The recombinant enzyme (rAlgSV1-PL7) was produced in an Escherichia coli system and it was classified in the Polysaccharide Lyase family 7. The optimal temperature and pH for rAlgSV1-PL7 activity were around 45 °C and 8, respectively. Interestingly, we observed that rAlgSV1-PL7 retained over 80% of its enzyme activity after incubation at 30 °C for at least 20 days, indicating that rAlgSV1-PL7 is a long-lived enzyme. Moreover, the degradation of alginate by rAlgSV1-PL7 produced one to four sugars because of the broad substrate specificity of this enzyme. Our findings suggest that rAlgSV1-PL7 may represent a new commercially useful enzyme.

Amyloid fibril formation is implicated in numerous protein misfolding disorders. Fucoidan, a sulfated polysaccharide primarily derived from brown algae, exhibits diverse biological activities. In this study, we investigated the inhibitory effect of Sargassum horneri fucoidan (S-fucoidan) on insulin amyloid fibrillation in vitro. Initial screening of fucoidans derived from Cladosiphon okamuranus, Kjellmaniella crassifolia, and S. horneri identified S-fucoidan as the most effective inhibitor of insulin fibrillation. Therefore, we characterized the inhibitory effect of S-fucoidan using Thioflavin T fluorescence, transmission electron microscopy, circular dichroism spectroscopy, size-exclusion chromatography, and cell viability assays. Both S-fucoidan and low-molecular-weight S-fucoidan inhibited fibrillation in a concentration-dependent manner. When present from the onset of the reaction, S-fucoidan prevented detectable fibril formation, preserved the initial secondary structure of insulin, and maintained insulin in a monomeric or near-monomeric state. In contrast, addition during nucleation or elongation did not effectively halt ongoing fibrillation. These findings indicate that S-fucoidan predominantly suppresses the early stage of insulin amyloid fibrillation and provide a basis for investigating the molecular mechanisms underlying its anti-fibrillation activity.