Thiosemicarbazone Derivatives as Inhibitors of Amyloid-β Aggregation: Effect of Metal Coordination

Transition Metal Complexes as Therapeutics: A New Frontier in Combatting Neurodegenerative Disorders through Protein Aggregation Modulation

Neurodegenerative disorders (NDDs) are a class of debilitating diseases that progressively impair the protein structure and result in neurological dysfunction in the nervous system. Among these disorders, Alzheimer's disease (AD), prion diseases such as Creutzfeldt-Jakob disease (CJD), and Parkinson's disease (PD) are caused by protein misfolding and aggregation at the cellular level. In recent years, transition metal complexes have gained significant attention for their potential applications in diagnosing, imaging, and curing these NDDs. These complexes have intriguing possibilities as therapeutics due to their diverse ligand systems and chemical properties and can interact with biological systems with minimal detrimental effects. This review focuses on the recent progress in transition metal therapeutics as a new era of hope in the battle against AD, CJD, and PD by modulating protein aggregation in vitro and in vivo. It may shed revolutionary insights into unlocking new opportunities for researchers to develop metal-based drugs to combat NDDs.

Desulfurization of thiosemicarbazones: the role of metal ions and biological implications

Thiosemicarbazones are biologically active substances whose structural formula is formed by an azomethine, an hydrazine, and a thioamide fragments, to generate a R2C=N-NR-C(=S)-NR2 backbone. These compounds often act as ligands to generate highly stable metal-organic complexes. In certain experimental conditions, however, thiosemicarbazones undergo reactions leading to the cleavage of the chain. Sometimes, the breakage involves desulfurization processes. The present work summarizes the different chemical factors that influence the desulfurization reactions of thiosemicarbazones, such as pH, the presence of oxidant reactants or the establishment of redox processes as those electrochemically induced, the effects of the solvent, the temperature, and the electromagnetic radiation. Many of these reactions require coordination of thiosemicarbazones to metal ions, even those present in the intracellular environment. The nature of the products generated in these reactions, their detection in vivo and in vitro, together with the relevance for the biological activity of these compounds, mainly as antineoplastic agents, is discussed.

Evaluation of azothioformamides and their copper(I) and silver(I) complexes for biological activity

Redox-active azothioformamides (ATFs) contain an NNCS 1,3-heterodiene motif typically found in other molecular subclasses that exhibit a wide range of cytotoxic and anti-neoplastic effects, either alone or as chelation complexes with various metals. For this study, a small library of ATF compounds was synthesized and tested across a range of microbes, fungi, and cancer cell lines for biological activity, both alone and as metal chelates of copper(I) and silver(I) salts. Alone, the ATF compounds exhibited little antimicrobial activity, but all inhibited the cell growth of A549 lung carcinoma cells (IC50 values of 1-6 μM). As copper(I) and silver(I) coordination complexes, several of the ATFs showed antimicrobial activity against gram positive Staphylococcus aureus and Bacillus subtilis cells (IC50 ∼ 5-20 μM) and the fungi Candida albicans (IC50 ∼ 8-12 μM); as well as cytotoxicity against both lung carcinoma A549 cells and lymphoblastic leukemia K562 cells.

Mesenchymal stromal cell-derived secretome-based therapy for neurodegenerative diseases: overview of clinical trials

BACKGROUND

Over the past few years, mesenchymal stromal cells (MSCs) have attracted a great deal of scientific attention owing to their promising results in the treatment of incurable diseases. However, there are several concerns about their possible side effects after direct cell transplantation, including host immune response, time-consuming cell culture procedures, and the dependence of cell quality on the donor, which limit the application of MSCs in clinical trials. On the other hand, it is well accepted that the beneficial effects of MSCs are mediated by secretome rather than cell replacement. MSC secretome refers to a variety of bioactive molecules involved in different biological processes, specifically neuro-regeneration.

MAIN BODY

Due to the limited ability of the central nervous system to compensate for neuronal loss and relieve disease progress, mesenchymal stem cell products may be used as a potential cure for central nervous system disorders. In the present study, the therapeutic effects of MSC secretome were reviewed and discussed the possible mechanisms in the three most prevalent central nervous system disorders, namely Alzheimer's disease, multiple sclerosis, and Parkinson's disease. The current work aimed to help discover new medicine for the mentioned complications.

CONCLUSION

The use of MSC-derived secretomes in the treatment of the mentioned diseases has encouraging results, so it can be considered as a treatment option for which no treatment has been introduced so far.

Conversion of a double-tetranuclear cluster silver helicate into a dihelicate via a rare desulfurization process

We show the first example of a bisthiosemicarbazone silver double-tetranuclear cluster helicate [Ag4L2]2 obtained by electrochemical synthesis which undergoes a rare desulfurization process giving rise to a cationic silver dihelicate [Ag2(H2L)2]SO4.

Multifunctional Gold Nanoparticle-Conjugated Cellulose Nanoonions Alleviate Aβ42 Fibrillation-Induced Toxicity via Regulation of Oxidative Stress and Ion Homeostasis

Inhibition of hen egg white lysozyme (HEWL) and Aβ42 fibrillation have been established as the main models for the treatment of systemic lysozyme amyloidosis and Alzheimer's disease (AD), respectively. Several antiamyloidogenic nanomaterials have been developed over the period; however, their intracellular mechanism of action is still not well understood. In this context, plant-based, gold-conjugated, injectable, hydrophilic cellulose nanoonions (CNOs), viz., DH-CNO (∼60 ± 5 nm) and LC-CNO (∼55 ± 12 nm), were developed from their respective hydrophobic cellulose nanocrystals (DH-CNC and LC-CNC) using a single-step chemical template-mediated process. This unique nanocellulose architecture was chemically and morphologically characterized by various spectroscopic and microscopic techniques. Further, the different biophysical studies documented marked the inhibition/disintegration potential of gold-conjugated LC-CNO against HEWL and Aβ42 peptide aggregation. It was further observed that inhibition of protein fibrillation could be achieved within ∼10 min when the same materials were used under photoirradiation conditions. In vitro protein aggregation studies using HEK293 cells suggested that gold-conjugated LC-CNO could effectively reduce the cellular toxicity via regulation of oxidative stress and ion homeostasis. The outcome of the present study will help in designing cellulose-based novel functional nanochaperones against various neurodegenerative diseases.

Zn-doped Cu2S quantum dots as new high-efficiency inhibitors against human insulin fibrillation based on specific electrostatic interaction with oligomers

Inhibition of protein fibrillation process with nanomaterials is a promising strategy to combat neurodegenerative diseases. Copper-based nanomaterials have been seldom utilized in fibrillation inhibiting research due to Copper ions are generally considered as accelerators of fibrosis. Here, we proposed ultra-small Zn doped Cu₂S (Zn:Cu₂S) QDs as inhibitors of human insulin (HI) fibrosis. ThT, DLS, CD and TEM confirm that Zn:Cu₂S QDs effectively inhibited insulin fibrosis in a dose-dependent manner with lag phase time extended (beyond 13-time by Zn:Cu₂S QDs of 1 mg·mL^-1), final fibril formation and the conversion from α-helix to β-sheet reduced. Additionally, thermodynamics analyzed results reveal that the HI fluorescence quenching process is static quenching dominated, and the Zn:Cu₂S QDs inhibit HI fibrosis mainly through specific electrostatic interaction with oligomers. The positively charged amino acid residues of oligomers bind to the negatively charged Zn:Cu₂S QDs, which prevents the self-assembly of the oligomers from growing into mature fibers to enhance the stability of the protein. Unlike free Copper ions, the as-prepared QDs show an excellent inhibition in HI fibrillation, breaking through the bottleneck of copper-based materials in inhibiting protein fibrosis and providing a potential strategy to inhibit protein fibrosis in-situ by biosynthesizing copper-based fibrosis inhibitors.

Dual Effect of Prussian Blue Nanoparticles on Aβ40 Aggregation: β-Sheet Fibril Reduction and Copper Dyshomeostasis Regulation

Alzheimer's disease (AD), affecting almost 50 million individuals worldwide, is currently the first cause of dementia. Despite the tremendous research efforts in the last decade, only four supportive or palliative drugs, namely, acetylcholinesterase (AChE) inhibitors donepezil, galantamine, and rivastigmine and the glutamate NMDA receptor antagonist memantine, are currently available. New therapeutic strategies are becoming prominent, such as the direct inhibition of amyloid formation or the regulation of metal homeostasis. In the present report, the potential use of Prussian blue (PB), a drug that is in the World Health Organization Model List of Essential Medicines, in AD treatment is demonstrated. Both in vitro and in cellulo studies indeed suggest that PB nanoparticles (PBNPs) are capable of reducing the formation of typical amyloid-β fibers (detected by thioflavin T fluorescence) and restoring the usual amyloid fibrillation pathway via chelation/sequestration of copper, which is found in high concentrations in senile plaques.

Thiosemicarbazone Complexes of Transition Metals as Catalysts for Cross-Coupling Reactions

Catalysis of cross-coupling reactions under phosphane-free conditions represents an important ongoing challenge. Although transition metal complexes based on the thiosemicarbazone unit have been known for a very long time, their use in homogeneous catalysis has been studied only relatively recently. In particular, reports of cross-coupling catalytic reactions with such complexes have appeared only in the last 15 years. This review provides a survey of the research in this area and a discussion of the prospects for future developments.