Metal Complex Formation and Anticancer Activity of Cu(I) and Cu(II) Complexes with Metformin.

Metformin has been used for decades in millions of type 2 diabetes mellitus patients. In this time, correlations between metformin use and the occurrence of other disorders have been noted, as well as unpredictable metformin side effects. Diabetes is a significant cancer risk factor, but unexpectedly, metformin-treated diabetic patients have lower cancer incidence. Here, we show that metformin forms stable complexes with copper (II) ions. Both copper(I)/metformin and copper(II)/metformin complexes form adducts with glutathione, the main intracellular antioxidative peptide, found at high levels in cancer cells. Metformin reduces cell number and viability in SW1222 and K562 cells, as well as in K562-200 multidrug-resistant cells. Notably, the antiproliferative effect of metformin is enhanced in the presence of copper ions.

Copper(II) and Amylin Analogues: A Complicated Relationship.

Protein aggregation has attracted substantial interest because of its role in causing many serious illnesses, such as neurodegenerative diseases and type II diabetes. Recent studies have shown that protein aggregation can be prevented by forming metal ion complexes with a target protein, which affects their conformation in solution and their physical properties, such as aggregation. Thus, understanding the interactions between aggregating molecules and bioactive metal ions such as Cu2+ is beneficial for new drug discovery. Pramlintide, a synthetic peptide drug, and its natural counterpart rat amylin are known to be resistant to aggregation because of the presence of proline residues, which are usually ß-sheet "breakers" within their amino acid sequence. Here, we investigate the Cu2+ coordination properties of pramlintide and rat amylin using nuclear magnetic resonance, circular dichroism, electron paramagnetic resonance, ultraviolet-visible spectroscopy, potentiometry, and mass spectrometry. We test the influence of Cu2+ on the aggregation properties of these amylin analogues with thioflavin T assays. We find that both peptides form stable complexes with Cu2+ with similar affinities at a 1:1 ratio. The N-termini of both peptides are involved in Cu2+ binding; His18 imidazole is an equally attractive binding site in the case of pramlintide. Our results show that Cu2+ ions influence the aggregation of pramlintide, but not that of rat amylin.

Using NMR spectroscopy to investigate the role played by copper in prion diseases.

Prion diseases are a group of rare neurodegenerative disorders that develop as a result of the conformational conversion of normal prion protein (PrPC) to the disease-associated isoform (PrPSc). The mechanism that actually causes disease remains unclear. However, the mechanism underlying the conformational transformation of prion protein is partially understood-in particular, there is strong evidence that copper ions play a significant functional role in prion proteins and in their conformational conversion. Various models of the interaction of copper ions with prion proteins have been proposed for the Cu (II)-binding, cell-surface glycoprotein known as prion protein (PrP). Changes in the concentration of copper ions in the brain have been associated with prion diseases and there is strong evidence that copper plays a significant functional role in the conformational conversion of PrP. Nevertheless, because copper ions have been shown to have both a positive and negative effect on prion disease onset, the role played by Cu (II) ions in these diseases remains a topic of debate. Because of the unique properties of paramagnetic Cu (II) ions in the magnetic field, their interactions with PrP can be tracked even at single atom resolution using nuclear magnetic resonance (NMR) spectroscopy. Various NMR approaches have been utilized to study the kinetic, thermodynamic, and structural properties of Cu (II)-PrP interactions. Here, we highlight the different models of copper interactions with PrP with particular focus on studies that use NMR spectroscopy to investigate the role played by copper ions in prion diseases.

"What Doesn't Kill You Makes You Stronger": Future Applications of Amyloid Aggregates in Biomedicine.

Amyloid proteins are linked to the pathogenesis of several diseases including Alzheimer's disease, but at the same time a range of functional amyloids are physiologically important in humans. Although the disease pathogenies have been associated with protein aggregation, the mechanisms and factors that lead to protein aggregation are not completely understood. Paradoxically, unique characteristics of amyloids provide new opportunities for engineering innovative materials with biomedical applications. In this review, we discuss not only outstanding advances in biomedical applications of amyloid peptides, but also the mechanism of amyloid aggregation, factors affecting the process, and core sequences driving the aggregation. We aim with this review to provide a useful manual for those who engineer amyloids for innovative medicine solutions.

Mitigating diabetes associated with reactive oxygen species (ROS) and protein aggregation through pharmacological interventions.

Diabetes mellitus, a complex metabolic disorder, presents a growing global health challenge. In 2021, there were 529 million diabetics worldwide. At the super-regional level, Oceania, the Middle East, and North Africa had the highest age-standardized rates. The majority of cases of diabetes in 2021 (>90.0%) were type 2 diabetes, which is largely indicative of the prevalence of diabetes in general, particularly in older adults (K. L. Ong, et al., Global, regional, and national burden of diabetes from 1990 to 2021, with projections of prevalence to 2050: a systematic analysis for the Global Burden of Disease Study 2021, Lancet, 2023, 402(10397), 203-234). Nowadays, slowing the progression of diabetic complications is the only effective way to manage diabetes with the available therapeutic options. However, novel biomarkers and treatments are urgently needed to control cytokine secretion, advanced glycation end products (AGEs) production, vascular inflammatory effects, and cellular death. Emerging research has highlighted the intricate interplay between reactive oxygen species (ROS) and protein aggregation in the pathogenesis of diabetes. In this scenario, the main aim of this paper is to provide a comprehensive review of the current understanding of the molecular mechanisms underlying ROS-induced cellular damage and protein aggregation, specifically focusing on their contribution to diabetes development. The role of ROS as key mediators of oxidative stress in diabetes is discussed, emphasizing their impact on cellular components and signaling. Additionally, the involvement of protein aggregation in impairing cellular function and insulin signaling is explored. The synergistic effects of ROS and protein aggregation in promoting ß-cell dysfunction and insulin resistance are examined, shedding light on potential targets for therapeutic intervention.

Living with the enemy: from protein-misfolding pathologies we know, to those we want to know.

Conformational diseases are caused by the aggregation of misfolded proteins. The risk for such pathologies develops years before clinical symptoms appear, and is higher in people with alpha-1 antitrypsin (AAT) polymorphisms. Thousands of people with alpha-1 antitrypsin deficiency (AATD) are underdiagnosed. Enemy-aggregating proteins may reside in these underdiagnosed AATD patients for many years before a pathology for AATD fully develops. In this perspective review, we hypothesize that the AAT protein could exert a new and previously unconsidered biological effect as an endogenous metal ion chelator that plays a significant role in essential metal ion homeostasis. In this respect, AAT polymorphism may cause an imbalance of metal ions, which could be correlated with the aggregation of amylin, tau, amyloid beta, and alpha synuclein proteins in type 2 diabetes mellitus (T2DM), Alzheimer's and Parkinson's diseases, respectively.

Natural Polysaccharides as Preventive and Therapeutic Horizon for Neurodegenerative Diseases.

Neurodegenerative diseases are a serious and widespread global public health burden amongst aging populations. The total estimated worldwide global cost of dementia was US$818 billion in 2015 and has been projected to rise to 2 trillion US$ by 2030. While advances have been made to understand different neurodegenerative disease mechanisms, effective therapeutic strategies do not generally exist. Several drugs have been proposed in the last two decades for the treatment of different types of neurodegenerative diseases, with little therapeutic benefit, and often with severe adverse and side effects. Thus, the search for novel drugs with higher efficacy and fewer drawbacks is an ongoing challenge in the treatment of neurodegenerative disease. Several natural compounds including polysaccharides have demonstrated neuroprotective and even therapeutic effects. Natural polysaccharides are widely distributed in plants, animals, algae, bacterial and fungal species, and have received considerable attention for their wide-ranging bioactivity, including their antioxidant, anti-neuroinflammatory, anticholinesterase and anti-amyloidogenic effects. In this review, we summarize different mechanisms involved in neurodegenerative diseases and the neuroprotective effects of natural polysaccharides, highlighting their potential role in the prevention and therapy of neurodegenerative disease.

Undercover Toxic Ménage à Trois of Amylin, Copper (II) and Metformin in Human Embryonic Kidney Cells.

In recent decades, type 2 diabetes complications have been correlated with amylin aggregation, copper homeostasis and metformin side effects. However, each factor was analyzed separately, and only in some rare cases copper/amylin or copper/metformin complexes were considered. We demonstrate for the first time that binary metformin/amylin and tertiary copper (II)/amylin/metformin complexes of high cellular toxicity are formed and lead to the formation of aggregated multi-level lamellar structures on the cell membrane. Considering the increased concentration of amylin, copper (II) and metformin in kidneys of T2DM patients, our findings on the toxicity of amylin and its adducts may be correlated with diabetic nephropathy development.

Interaction of amylin species with transition metals and membranes.

Islet Amyloid Polypeptide (IAPP), also known as amylin, is a 37-amino-acid peptide hormone that is secreted by pancreatic islet ß-cells. Amylin is complementary to insulin in regulating and maintaining blood glucose levels in the human body. The misfolding and aggregation of amylin is primarily associated with type 2 diabetes mellitus, which is classified as an amyloid disease. Recently, the interactions between amylin and specific metal ions, e.g., copper(II), zinc(II), and iron(II), were found to impact its performance and aggregation processes. Therefore, the focus in this review will be on how the chemistry and structural properties of amylin are affected by these interactions. In addition, the impact of amylin and other amyloidogenic peptides interacting with metal ions on the cell membranes is discussed. In particular, recent studies on the interactions of amylin with copper, zinc, iron, nickel, gold, ruthenium, and vanadium are discussed.