The accumulation and aggregation of α-synuclein (α-syn) is the main pathologic event in Parkinson’s disease (PD), dementia with Lewy bodies, and multiple system atrophy. α-Syn-seeded fibril formation and its induced toxicity occupy a major role in PD pathogenesis. Thus, assessing compounds that inhibit this seeding process is considered a key towards the therapeutics of synucleinopathies. Using biophysical and biochemical techniques and seeding-dependent cell viability assays, we screened a total of nine natural compounds of alkaloid origin extracted from Chinese medicinal herbs. Of these compounds, synephrine, trigonelline, cytisine, harmine, koumine, peimisine, and hupehenine exhibited in vitro inhibition of α-syn-seeded fibril formation. Furthermore, using cell viability assays, six of these compounds inhibited α-syn-seeding-dependent toxicity. These six potent inhibitors of amyloid fibril formation and toxicity caused by the seeding process represent a promising therapeutic strategy for the treatment of PD and other synucleinopathies.

Aggregated α-synuclein (αSyn) protein is a core pathological feature of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Both PD and DLB demonstrate the presence of diverse intracellular α-synuclein (αSyn) species, including C-terminally truncated αSyn (C-αSyn), although it is unknown how C-αSyn species contribute to disease progression. Using recombinant C-αSyn and PD and DLB brain lysates as seeds in the real-time quaking-induced conversion (RT-QuIC) assay, we explored how C-αSyn may be involved in disease stratification. Comparing the seeding activity of aqueous-soluble fractions to detergent-soluble fractions, and using αSyn 1-130 as substrate for the RT-QuIC assay, the temporal cortex seeds differentiated PD and DLB from healthy controls. In contrast to the temporal cortex, where PD and DLB could not be distinguished, αSyn 1-130 seeded by the detergent-soluble fractions from the PD frontal cortex demonstrated greater seeding efficiency compared to the DLB frontal cortex. Moreover, proteinase K-resistant (PK^res) fragments from the RT-QuIC end products using C-αSyn 1-130 or C-αSyn 1-115 were more obvious in the frontal cortex compared to the temporal cortex. Morphological examinations of RT-QuIC end products showed differences in the size of the fibrils between C-αSyn 1-130 and C-αSyn 1-115, in agreement with the RT-QuIC results. These data show that C-αSyn species can distinguish PD from DLB and suggest diversity in αSyn species across these synucleinopathies, which could play a role in disease progression.

Background: Lactate Dehydrogenase C (LDHC) is a promising therapeutic target due to its highly tumor-specific expression, immunogenicity, and oncogenic functions. We previously showed that LDHC silencing in triple-negative breast cancer (TNBC) cells enhances treatment response to DNA-damage response-related drugs, supporting its therapeutic potential. However, no selective LDHC inhibitors exist, highlighting the need for innovative targeting strategies. Methods: We assessed the physicochemical properties and evaluated the delivery efficiency, anti-tumor activity, and safety of four cell-penetrating peptides (CPPs)—R10, 10R-RGD, cRGD-10R, and iRGD-10R—for siRNA-mediated LDHC silencing in TNBC. Clonogenic assays were used to evaluate effects on olaparib sensitivity, and TNBC zebrafish xenografts were utilized to study in vivo anti-tumor activity. Results: All CPP:siRNA complexes formed uniform nanocomplexes (129–168 nm) with low polydispersity indices (<0.25) and positive zeta potentials (+6.47 to +29.6 mV). Complexes remained stable in human serum for 24 h and showed no significant cytotoxicity in TNBC and non-cancerous cell lines. The 10R-RGD and cRGD-10R:siLDHC complexes achieved 40% LDHC protein knockdown, reduced TNBC clonogenicity by 30–36%, and enhanced olaparib sensitivity. Treatment of TNBC zebrafish xenografts with 10R-RGD or cRGD-10R:siLDHC complexes significantly reduced tumor growth by approximately 50% without major toxicity. Conclusions: These results demonstrate that CPP-mediated siRNA delivery enables selective LDHC silencing with tumor growth inhibition in triple-negative breast cancer models. This approach represents a novel, effective, and safe proof-of-concept therapeutic strategy to target LDHC, with potential translational relevance as a standalone therapy or in combination with common anti-cancer drugs.

Aggregation and seeded propagation of α-synuclein (α-syn) are central to the pathogenesis of Parkinson’s disease and related synucleionopathies. Modulation of seeded aggregation and amplification of pathological α-syn species represents a promising strategy for limiting disease progression. Here, we investigated the effects of naturally derived polyphenolic compounds on α-syn fibrillation, seeded aggregation, and associated cytotoxicity. Among the compounds examined, salvianolic acid B and dihydromyricetin exhibited significant inhibitory effects on α-syn aggregation. Biochemical and biophysical analyses using Thioflavin-T fluorescence, Congo Red binding, and transmission electron microscopy demonstrated that both compounds inhibited fibril formation and altered fibril morphology. Notably, dihydromyricetin efficiently disaggregated preformed fibrils and suppressed seeded fibril elongation, whereas salvianolic acid B primarily delayed aggregation kinetics. Both compounds significantly reduced α-syn-induced cytotoxicity in BE(2)-M17 cells. These findings demonstrate that salvianolic acid B and dihydromyricetin differentially modulate key steps in the α-syn aggregation pathway and reduce associated cellular toxicity. Collectively, these results provide mechanistic insight into the modulation of seeded α-syn aggregation and identify salvianolic acid B and dihydromyricetin as effective modulators of pathological α-syn assembly.