A Co(III) complex cleaving soluble oligomers of h-IAPP in the presence of polymeric aggregates of h-IAPP

Natural Products as Regulators against Matrix Metalloproteinases for the Treatment of Cancer

Cancers are currently the major cause of mortality in the world. According to previous studies, matrix metalloproteinases (MMPs) have an impact on tumor cell proliferation, which could lead to the onset and progression of cancers. Therefore, regulating the expression and activity of MMPs, especially MMP-2 and MMP-9, could be a promising strategy to reduce the risk of cancers. Various studies have tried to investigate and understand the pathophysiology of cancers to suggest potent treatments. In this review, we summarize how natural products from marine organisms and plants, as regulators of MMP-2 and MMP-9 expression and enzymatic activity, can operate as potent anticancer agents.

Metal Complexes as Promising Matrix Metalloproteinases Regulators

Nowadays, cancers and dementia, such as Alzheimer's disease, are the most fatal causes of death. Many studies tried to understand the pathogenesis of those diseases clearly and develop a promising way to treat the diseases. Matrix metalloproteinases (MMPs) have been reported to be involved in the pathology of cancers and AD through tumor cell movement and amyloid degradation. Therefore, control of the levels and actions of MMPs, especially MMP-2 and MMP-9, is necessary to care for and/or cure cancer and AD. Various molecules have been examined for their potential application as regulators of MMPs expression and activity. Among the molecules, multiple metal complexes have shown advantages, including simple synthesis, less toxicity and specificity toward MMPs in cancer cells or in the brain. In this review, we summarize the recent studies and knowledge of metal complexes (e.g., Pt-, Ru-, Au-, Fe-, Cu-, Ni-, Zn-, and Sn-complexes) targeting MMPs and their potentials for treating and/or caring the most fatal human diseases, cancers and AD.

Islet amyloid toxicity: From genesis to counteracting mechanisms

Islet amyloid polypeptide (IAPP or amylin) is a hormone co-secreted with insulin by pancreatic β-cells and is the major component of islet amyloid. Islet amyloid is found in the pancreas of patients with type 2 diabetes (T2D) and may be involved in β-cell dysfunction and death, observed in this disease. Thus, investigating the aspects related to amyloid formation is relevant to the development of strategies towards β-cell protection. In this sense, IAPP misprocessing, IAPP overproduction, and disturbances in intra- and extracellular environments seem to be decisive for IAPP to form islet amyloid. Islet amyloid toxicity in β-cells may be triggered in intra- and/or extracellular sites by membrane damage, endoplasmic reticulum stress, autophagy disruption, mitochondrial dysfunction, inflammation, and apoptosis. Importantly, different approaches have been suggested to prevent islet amyloid cytotoxicity, from inhibition of IAPP aggregation to attenuation of cell death mechanisms. Such approaches have improved β-cell function and prevented the development of hyperglycemia in animals. Therefore, counteracting islet amyloid may be a promising therapy for T2D treatment.

Studies on the effect of a Fupenzi glycoprotein on the fibrillation of bovine serum albumin and its antioxidant activity

In this study, the effect of a glycoprotein obtained from Fupenzi (FPZ) (Rubus chingii Hu.) on the fibrillation of bovine serum album (BSA) was investigated by multi-spectroscopic methods and transmission electron microscopy. Moreover, the cytotoxicity of the glycoprotein and the effect of it on H₂O₂-induced cell viability were investigated by cell counting kit and β-galactosidase kit, respectively. The experimental results indicated that the glycoprotein showed very low toxicity to NRK-52E cells and could obviously delay cell senescence and improve cell viability. Moreover, the glycoprotein could effectively inhibit the formation of BSA fibrils and destroy the stability of preformed BSA fibrils in a concentration-dependent manner. Generally, antioxidant capacities are thought to be related to the anti-amyloidogenic activity of inhibitors; therefore, to reveal the inhibitory mechanism, the anti-oxidative property of the glycoprotein was examined by DPPH and ABTS assays. The results demonstrated that FPZ glycoprotein had a remarkable antioxidant activity and the IC₅₀ values of DPPH and ABTS were 0.249 mg mL^-1 and 0.092 mg mL^-1, respectively. This work suggested that the FPZ glycoprotein had the potential to be designed a new therapeutic agent for attenuating aging and preventing the age-related diseases.

A dual-inhibitor system for the effective antifibrillation of Aβ40 peptides by biodegradable EGCG–Fe(iii)/PVP nanoparticles

By the synergistic effect of dual inhibition, EFPP NPs exhibited a significant effect on the inhibition of Aβ40 fibrillation and on the disaggregation of existing Aβ40 fibrils.

Dual effect of PEG-PE micelle over the oligomerization and fibrillation of human islet amyloid polypeptide

The oligomerization and fibrillation of human islet amyloid polypeptide (hIAPP) play a central role in the pathogenesis of type 2 diabetes. Strategies for remodelling the formation of hIAPP oligomers and fibrils have promising application potential in type 2 diabetes therapy. Herein, we demonstrated that PEG-PE micelle could inhibit hIAPP oligomerization and fibrillation through blocking the hydrophobic interaction and the conformational change from random coil to β-sheet structures of hIAPP. In addition, we also found that PEG-PE micelle could remodel the preformed hIAPP fibrils allowing the formation of short fibrils and co-aggregates. Taken together, PEG-PE micelle could rescue hIAPP-induced cytotoxicity by decreasing the content of hIAPP oligomers and fibrils that are related to the oxidative stress and cell membrane permeability. This study could be beneficial for the design and development of antiamyloidogenic agents.

The effects of a series of carbon dots on fibrillation and cytotoxicity of human islet amyloid polypeptide

Carbon dots can change hIAPP aggregation kinetics and have a potential to reduce the cytotoxicity of the polypeptide.

Ruthenium complexes as inhibitors of human islet amyloid polypeptide aggregation, an effect that prevents beta cell apoptosis

Herein we show that ruthenium complexes could inhibit fibrosis of hIAPP and protect the hIAPP-induced cell damage by suppressing ROS generation, indicating the application potential of the complexes in treatment of T2DM by targeting hIAPP.

Site-Selective Peptide/Protein Cleavage

Site-selective peptide/protein degradation through chemical cleavage methods is an important modification of biologically relevant macromolecules which complements enzymatic hydrolysis. In this review, recent progress in chemical, site-selective peptide bond cleavage is overviewed, with an emphasis on postulated mechanisms and their implications on reactivity, selectivity, and substrate scope.

Inhibition of islet amyloid polypeptide fibril formation by selenium-containing phycocyanin and prevention of beta cell apoptosis

Human islet amyloid polypeptide (hIAPP) fibril is the major constituent of amyloid deposits in pancreatic islets of type 2 diabetes. Misfolding and hIAPP fibril formation are thought to be important in the pathogenesis of diabetes. Studies have showed that selenium-containing phycocyanin (Se-PC) inhibited the fibrillation of hIAPP to form nanoscale particles, which is mainly by interfering with the combination between hIAPP. Small nanoscale oligomers tended to grow into larger nanoparticles and the size of nanoparticles increased with the incubation time. By interfering with the fibrillation of hIAPP and altering the structure, Se-PC alleviated hIAPP-induced cell apoptosis. Meantime, generation of ROS produced during the fibrillation process was inhibited, which was proposed to be the main factor for the hIAPP-cytotoxicity in beta cells. Taken together, Se-PC inhibited hIAPP fibrillation, thus suppressed the formation of ROS to show protective effect on hIAPP mediated cell apoptosis. Our studies provide useful information for our understanding of the interaction mechanisms of Se-PC on hIAPP structure and protective mechanisms on hIAPP cytotoxicity, presenting useful candidate for anti-diabetes drug development.

Islet amyloid polypeptide toxicity and membrane interactions

Islet amyloid polypeptide (IAPP) is responsible for amyloid formation in type 2 diabetes and contributes to the failure of islet cell transplants, however the mechanisms of IAPP-induced cytotoxicity are not known. Interactions with model anionic membranes are known to catalyze IAPP amyloid formation in vitro. Human IAPP damages anionic membranes, promoting vesicle leakage, but the features that control IAPP-membrane interactions and the connection with cellular toxicity are not clear. Kinetic studies with wild-type IAPP and IAPP mutants demonstrate that membrane leakage is induced by prefibrillar IAPP species and continues over the course of amyloid formation, correlating additional membrane disruption with fibril growth. Analyses of a set of designed mutants reveal that membrane leakage does not require the formation of β-sheet or α-helical structures. A His-18 to Arg substitution enhances leakage, whereas replacement of all of the aromatic residues via a triple leucine mutant has no effect. Biophysical measurements in conjunction with cytotoxicity studies show that nonamyloidogenic rat IAPP is as effective as human IAPP at disrupting standard anionic model membranes under conditions where rat IAPP does not induce cellular toxicity. Similar results are obtained with more complex model membranes, including ternary systems that contain cholesterol and are capable of forming lipid rafts. A designed point mutant, I26P-IAPP; a designed double mutant, G24P, I26P-IAPP; a double N-methylated variant; and pramlintide, a US Food and Drug Administration-approved IAPP variant all induce membrane leakage, but are not cytotoxic, showing that there is no one-to-one relationship between disruption of model membranes and induction of cellular toxicity.