ABSTRACT
Mangiferin is a natural xanthone glycoside with therapeutic potential. Herein, its cytotoxic properties were explored in a human cell model of breast adenocarcinoma. The results supported the multi-target nature of mangiferin action, as the inhibition of three enzymatic systems, namely HMG-CoA reductase, the proteasome and plasmin, respectively in charge of regulating cholesterol homeostasis, protein turnover and cell adhesion, was documented for the first time. Globally, mangiferin was able to selectively block breast cancer cell growth by inducing apoptosis and by arresting cell proliferation through a combined action on cholesterol and proteasome pathways, as well as to inhibit plasmin-mediated mechanisms of cell migration.
Subject(s)
Apoptosis/drug effects , Cell Proliferation/drug effects , Mevalonic Acid/metabolism , Proteasome Endopeptidase Complex/metabolism , Xanthones/pharmacology , Biomarkers , Breast Neoplasms , Cadherins/metabolism , Cell Adhesion/drug effects , Cell Line, Tumor , Cell Movement/drug effects , Cholesterol/metabolism , Dose-Response Relationship, Drug , Female , Fibrinolysin , Humans , Proteasome Inhibitors/administration & dosage , Proteasome Inhibitors/pharmacology , Xanthones/administration & dosageABSTRACT
Aberrant cellular proliferation and compromised apoptotic pathways are hallmarks of cancer aggressiveness, and in this framework, the role of protein degradation machineries has been extensively dissected. Among proteases, the proteasome is unequivocally central in the intracellular regulation of both these processes, thus several proteasome-directed therapies have been investigated, aiming at controlling its activity and possibly restoring normal cell functions. Numerous studies reported proteasome inhibitors (both synthetic and natural occurring) to potently and selectively induce apoptosis in many types of cancer cells. In this review we discuss recent advances in proteasomal modulation by some natural occurring polyphenols, globally providing evidence of the proteasome role as therapeutic target in cancer treatment.
Subject(s)
Antineoplastic Agents/therapeutic use , Biological Products/therapeutic use , Neoplasms/drug therapy , Protease Inhibitors/therapeutic use , Proteasome Inhibitors , Animals , Humans , Neoplasms/metabolism , Proteasome Endopeptidase Complex/metabolismABSTRACT
Electromagnetic fields are an assessed cause of prolonging free radicals lifespan. This study was carried out to investigate the influence of extremely low frequency electromagnetic fields on protein oxidation and on the 20S proteasome functionality, the complex responsible for the degradation of oxidized proteins. Caco 2 cells were exposed, for 24-72 hours, to 1 mT, 50 Hz electromagnetic fields. The treatment induced a time-dependent increase both in cell growth and in protein oxidation, more evident in the presence of TPA, while no changes in cell viability were detected. Exposing the cells to 50 Hz electromagnetic fields caused a global activation of the 20S proteasome catalytic components, particularly evident at 72 hours exposure and in the presence of TPA. The finding that EGCG, a natural antioxidant compound, counteracted the field-related pro-oxidant effects demonstrates that the increased proteasome activity was due to an enhancement in intracellular free radicals.
Subject(s)
Electromagnetic Fields/adverse effects , Neoplasms/metabolism , Proteasome Endopeptidase Complex/radiation effects , Protein Carbonylation/radiation effects , Analysis of Variance , Caco-2 Cells , Carcinogens/pharmacology , Catechin/analogs & derivatives , Catechin/pharmacology , Cell Survival/drug effects , Cell Survival/radiation effects , Cyclin-Dependent Kinase Inhibitor p27/metabolism , Dose-Response Relationship, Radiation , Humans , Radiation-Protective Agents/pharmacology , Temperature , Tetradecanoylphorbol Acetate/pharmacologyABSTRACT
Aflatoxins are highly hazardous contaminants of common food and feed. Aflatoxin B1 in particular, the most predominant among aflatoxins, was thoroughly demonstrated to be highly toxic, mutagenic, teratogenic and carcinogenic in many animal species. Besides its established targets and effects, this work investigates on the possible direct interaction between aflatoxin B1 and three major serine proteases, namely elastase, thrombin and trypsin. These proteases belongs to a class of structurally and functionally related proteins pivotal in both direct and indirect regulation of a number of cellular events. Additionally, several pathological processes, including cancer, inflammatory processes and thrombosis, rely upon the subtle equilibrium between these enzymes and their potential modulators: in fact, their misregulation, caused by foreign molecules, could facilitate (or be the cause for) the occurrence of these pathologies. Our results provide the evidence for a reversible binding between AFB1 and these enzymes, likely to have profound implications in the manifestation of aflatoxicosis. Precisely, the toxin behaved as a moderate competitive inhibitor toward the enzymatic activity of the serine proteases in the low micromolar range.
Subject(s)
Aflatoxin B1/metabolism , Poisons/metabolism , Serine Endopeptidases/metabolism , Serine Proteinase Inhibitors/metabolism , Aflatoxin B1/chemistry , Aflatoxin B1/toxicity , Animals , Binding Sites , Binding, Competitive , Cattle , Humans , Pancreatic Elastase/antagonists & inhibitors , Pancreatic Elastase/chemistry , Pancreatic Elastase/metabolism , Pharmacokinetics , Poisons/chemistry , Poisons/toxicity , Protein Binding , Serine Endopeptidases/chemistry , Serine Proteinase Inhibitors/chemistry , Serine Proteinase Inhibitors/toxicity , Swine , Thrombin/antagonists & inhibitors , Thrombin/chemistry , Thrombin/metabolism , Trypsin/chemistry , Trypsin/metabolismABSTRACT
Pomegranate (Punica granatum) is an important source of polyphenols with assessed antioxidant properties. The aims of this study were: (i) the characterization of the monomeric phenolic variability on each isolated fruit component (endocarp, mesocarp, aril); (ii) the study on the effect of pomegranate fruit components on human thrombin amidolytic activity. Collectively, our data show that pomegranate components contain bioactive metabolites (mainly ellagic acid) and suggest a potential role for the pomegranate extract in the regulation of a number of physio-pathological processes involving thrombin (or thrombin-like proteinase).
Subject(s)
Lythraceae/chemistry , Phenols/pharmacology , Plant Extracts/pharmacology , Thrombin/antagonists & inhibitors , Antioxidants/isolation & purification , Antioxidants/pharmacology , Fruit , Humans , Phenols/isolation & purification , Plant Extracts/chemistry , Plant Extracts/isolation & purificationABSTRACT
We present thick, uniform and rather flat melanin films obtained using spray deposition. The morphology of the films was investigated using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Temperature-dependent electrical resistance of melanin thin films evidenced a semiconductor-like character and a hysteretic behavior linked to an irreversible process of water molecule desorption from the melanin film. X-ray Photoelectron Spectroscopy (XPS) was carried out to analyze the role of the functional groups in the primary and secondary structure of the macromolecule, showing that the contribution of the 5,6-dihydroxyindole-2-carboxylic acid (DHICA) subunit to the molecule is about 35%. Comparison of the optical absorption of the thick (800nm) and thin (80nm) films showed a spectral change when the thickness increases. From in vacuum photoconductivity (PC) measured at controlled temperatures, we suggest that the melanin films exhibit a possible charge transport mechanism by means of delocalized pi states along the stacked planar secondary structure.
Subject(s)
Biophysics/methods , Melanins/chemistry , Electrons , Humans , Indoles/chemistry , Light , Materials Testing , Microscopy, Electron, Scanning/methods , Microscopy, Scanning Tunneling/methods , Molecular Conformation , Optics and Photonics , Polymers/chemistry , Spectrum Analysis/methods , X-RaysABSTRACT
Dipeptidyl peptidase II (DPPII) from bovine kidney cortex and lung was purified to the electrophoretically homogeneous state. The molecular and catalytic characteristics of the enzyme were determined. It was revealed that DPPII preparations possess adenosine deaminase (ADA) activity at all purification steps. For the first time, the ADA-binding ability of DPPII has been shown similar to the well-known ADA-binding enzyme, DPPIV. The dissociation constant of the DPPII-ADA complex was estimated using a resonant mirror biosensor (80 nM), fluorescence polarization (60 nM), and differential spectroscopy (36 nM) techniques. The data demonstrate that DPPII can form a complex with ADA, but with one order of magnitude higher dissociation constant than that of DPPIV (7.8 nM).
Subject(s)
Adenosine Deaminase/metabolism , Dipeptidyl-Peptidases and Tripeptidyl-Peptidases/metabolism , Multiprotein Complexes/metabolism , Adenosine Deaminase/isolation & purification , Animals , Cattle , Dipeptidyl Peptidase 4/metabolism , Dipeptidyl-Peptidases and Tripeptidyl-Peptidases/isolation & purification , Humans , Kidney Cortex/enzymology , Lung/enzymology , Protein BindingABSTRACT
The effect of a group of natural flavonoids on human thrombin amidolytic activity was investigated using a spectrophotometric inhibition assay while information on the kinetics and thermodynamics was obtained using optical biosensor techniques. All the flavonoids tested acted as reversible inhibitors, and the quercetin-thrombin complex was found to be most stable at pH=7.5. Docking analysis indicated that quercetin's inhibitory behavior could be related to its planar structure and low steric hindrance, and to its ability to form a critical H-bond with thrombin His57.
Subject(s)
Flavonoids/chemistry , Flavonoids/pharmacology , Quantitative Structure-Activity Relationship , Thrombin/antagonists & inhibitors , Thrombin/chemistry , Amidohydrolases/antagonists & inhibitors , Amidohydrolases/chemistry , Arginine/analogs & derivatives , Binding Sites/drug effects , Binding, Competitive , Biosensing Techniques , Blood Coagulation/drug effects , Enzyme Activation/drug effects , Enzyme Stability , Humans , Kinetics , Models, Molecular , Molecular Structure , Pipecolic Acids/chemistry , Pipecolic Acids/pharmacology , SulfonamidesABSTRACT
The proteasome and heat shock proteins have been found in the centrosome. The evidence of their copurification reported by several studies suggests that they form stable complex. In addition, Hsp90 is involved in the loading of proteasome-generated antigenic peptides to the class I major histocompatibility complex. In this article, we report a detailed thermodynamic and kinetic characterization of the Hsp90-20S proteasome interaction, using a surface plasmon resonance technique. The modulation exerted by protons in solution has been investigated, and the results have been discussed, taking into account structural motifs characterizing the binding interface between the two macromolecules.
