The interaction mechanism of plasma iron transport protein transferrin with nanoparticles

In the biological systems, exposure to nanoparticles (NPs) can cause complicated interactions with proteins, the formation of protein corona and structural changes to proteins. These changes depend not only on NP physicochemical properties, but also on the intrinsic stability of protein molecules. Although, the formation of protein corona on the surface of NPs and the underlying mechanisms have been fully explored in various studies, no comprehensive review has discussed the direct biochemical and biophysical interactions between NPs and blood proteins, particularly transferrin. In this review, we first discussed the interaction of NPs with proteins to comprehend the effects of physicochemical properties of NPs on protein structure. We then overviewed the transferrin structure and its direct interaction with NPs to explore transferrin stability and its iron ion (Fe³⁺) release behavior. Afterwards, we surveyed the various biological functions of transferrin, such as Fe³⁺ binding, receptor binding, antibacterial activity, growth, differentiation, and coagulation, followed by the application of transferrin-modified NPs in the development of drug delivery systems for cancer therapy. We believe that this study can provide useful insight into the design and development of bioconjugates containing NP-transferrin for potential biomedical applications.

Inhibition of Iron Release from Donkey Spleen Ferritin through Malt-Derived Protein Z-Ferulic Acid Interactions

Protein-small molecule interactions naturally occur in foodstuffs, which could improve the properties of protein and small molecules. Meanwhile, they might affect the bioavailability and nutritional value of proteins. Ferritin, as an iron-storage protein, has been a focus of research. However, the complexity of foodstuffs enables the interaction between ferritin and food components, especially polyphenols, which can induce iron release from ferritin. Thus, the application of ferritin in food is limited. Inspired by the natural-occurring, strong protein-polyphenol interactions in beer, to inhibit the iron release of ferritin, the malt-derived protein Z (PZ) was chosen to interact with ferulic acid (FA), an abundant reductant in malt, beer, and other foodstuffs. The analysis of the interaction between PZ and FA was carried out using fluorescence spectroscopy, the results of which suggest that one PZ molecule can bind with 22.11 ± 2.13 of FA, and the binding constant is (4.99 ± 2.13) × 10⁵ M^-1. In a molecular dynamics (MD) simulation, FA was found to be embedded in the internal hydrophobic pocket of PZ, where it formed hydrogen bonds with Val-389 and Tyr-234. As expected, compared to iron release induced by FA, the iron release from donkey spleen ferritin (DSF) induced by FA decreased by 86.20% in the presence of PZ. Meanwhile, based on the PZ-FA interaction, adding PZ in beer reduced iron release from DSF by 40.5% when DSF:PZ was 1:40 (molar ratio). This work will provide a novel method of inhibiting iron release from ferritin.

Destruction of Lysozyme Amyloid Fibrils Induced by Magnetoferritin and Reconstructed Ferritin

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), or systemic amyloidosis, are characterized by the specific protein transformation from the native state to stable insoluble deposits, e.g., amyloid plaques. The design of potential therapeutic agents and drugs focuses on the destabilization of the bonds in their beta-rich structures. Surprisingly, ferritin derivatives have recently been proposed to destabilize fibril structures. Using atomic force microscopy (AFM) and fluorescence spectrophotometry, we confirmed the destructive effect of reconstructed ferritin (RF) and magnetoferritin (MF) on lysosome amyloid fibrils (LAF). The presence of iron was shown to be the main factor responsible for the destruction of LAF. Moreover, we found that the interaction of RF and MF with LAF caused a significant increase in the release of potentially harmful ferrous ions. Zeta potential and UV spectroscopic measurements of LAF and ferritin derivative mixtures revealed a considerable difference in RF compared to MF. Our results contribute to a better understanding of the mechanism of fibril destabilization by ferritin-like proteins. From this point of view, ferritin derivatives seem to have a dual effect: therapeutic (fibril destruction) and adverse (oxidative stress initiated by increased Fe²⁺ release). Thus, ferritins may play a significant role in various future biomedical applications.

Iron delivery systems for controlled release of iron and enhancement of iron absorption and bioavailability

Iron deficiency is a global nutritional problem, and adding iron salts directly to food will have certain side effects on the human body. Therefore, there is growing interest in food-grade iron delivery systems. This review provides an overview of iron delivery systems, with emphasis on the controlled release of iron during gastrointestinal digestion, as well as the enhancement of iron absorption and bioavailability. Iron-bearing proteins are easily degraded by digestive enzymes and absorbed through receptor-mediated endocytosis. Instead, protein aggregates are slowly degraded in the stomach, which delays iron release and serves as a potential iron supplement. Amino acids, peptides and polysaccharides can bind iron through iron binding sites, but the formed compounds are prone to dissociation in the stomach. Moreover, peptides and polysaccharides can deliver iron by mediating the formation of ferric oxyhydroxide which is absorbed through endocytosis or bivalent transporter 1. In addition, liposomes are unstable during gastric digestion and iron is released in large quantities. Complexes formed by polysaccharides and proteins, and microcapsules formed by polysaccharides can delay the release of iron in the gastric environment and prolong iron release in the intestinal environment. This review is conducive to the development of iron functional ingredients and dietary supplements.

Oxidative degradation perturbs physico-chemical properties of hemoglobin in cigarette smokers: a threat to different biomolecules

CONTEXT

Cigarette smokers develop structural modification in hemoglobin (Hb) and this modification enable Hb to undergo higher rate of auto-oxidation, leading to generation of further intracellular ROS.

OBJECTIVE

In this study, we exhibited the possible cause and consequences of Hb modification in cigarette smokers.

METHODS

Twenty-two smokers and 16 nonsmokers, aged 25 to 35 years, having a smoking history of 7-10 years were recruited in this study. Carbonyl content, ferryl form, peroxidase-like and esterase-like activities of Hb were assayed. Free iron release by Hb, erythrocyte membrane-bound Hb and plasma Hb were also measured along with assessment of important biomolecular degradations by Hb.

RESULTS AND DISCUSSION

Increase in carbonyl content in Hb indicates its oxidative degradation. Increase in ferryl Hb formation, peroxidase-like activity and decrease in esterase like activity of Hb along with increased release of nonheme iron (from Hb) clearly indicates alteration in physico-chemical properties of Hb in smokers. Moreover, increase in erythrocyte membrane-bound Hb and plasma-free Hb provide further evidences for higher rate of Hb oxidation in smokers' erythrocyte. The rates of protein, lipid, sugar and DNA degradation were noticed to be higher by smokers' Hb; and were further attenuated by desferrioxamine as well as mannitol.

CONCLUSION

We conclude that in cigarette smokers, there is oxidative degradation of Hb and the degradation causes alteration in its physico-chemical properties, which in turn may degrade different biomolecules in its close vicinity by releasing more iron and production of more superoxide as well as hydroxyl radical.

Superparamagnetic Iron Oxide Nanoparticles Modified with Silica Layers as Potential Agents for Lung Cancer Treatment

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising drug delivery carriers and hyperthermia agents for the treatment of cancer. However, to ensure their safety in vivo, SPIONs must be modified in order to prevent unwanted iron release. Thus, SPIONs were coated with silica layers of different morphologies: non-porous (@SiO₂), mesoporous (@mSiO₂) or with a combination of non-porous and mesoporous layers (@SiO₂@mSiO₂) deposited via a sol-gel method. The presence of SiO₂ drastically changed the surface properties of the nanoparticles. The zeta potential changed from 19.6 ± 0.8 mV for SPIONs to -26.1 ± 0.1 mV for SPION@mSiO₂. The Brunauer-Emmett-Teller (BET) surface area increased from 7.54 ± 0.02 m²/g for SPIONs to 101.3 ± 2.8 m²/g for SPION@mSiO₂. All types of coatings significantly decreased iron release (at least 10 fold as compared to unmodified SPIONs). SPIONs and SPION@mSiO₂ were tested in vitro in contact with human lung epithelial cells (A549 and BEAS-2B). Both nanoparticle types were cytocompatible, although some delay in proliferation was observed for BEAS-2B cells as compared to A549 cells, which was correlated with increased cell velocity and nanoparticles uptake.

Iron Release Profile of Silica-Modified Zero-Valent Iron NPs and Their Implication in Cancer Therapy

To evaluate the iron ion release profile of zero-valent iron (ZVI)-based nanoparticles (NPs) and their relationship with lysosomes in cancer cells, silica and mesoporous silica-coated ZVI NPs (denoted as ZVI@SiO2 and ZVI@mSiO2) were synthesized and characterized for the following study of cytotoxicity, intracellular iron ion release, and their underlying mechanisms. ZVI@mSiO2 NPs showed higher cytotoxicity than ZVI@SiO2 NPs in the OEC-M1 oral cancer cell line. In addition, internalized ZVI@mSiO2 NPs deformed into hollow and void structures within the cells after a 24-h treatment, but ZVI@SiO2 NPs remained intact after internalization. The intracellular iron ion release profile was also accordant with the structural deformation of ZVI@mSiO2 NPs. Burst iron ion release occurred in ZVI@mSiO2-treated cells within an hour with increased lysosome membrane permeability, which induced massive reactive oxygen species generation followed by necrotic and apoptotic cell death. Furthermore, inhibition of endosome-lysosome system acidification successfully compromised burst iron ion release, thereby reversing the cell fate. An in vivo test also showed a promising anticancer effect of ZVI@mSiO2 NPs without significant weight loss. In conclusion, we demonstrated the anticancer property of ZVI@mSiO2 NPs as well as the iron ion release profile in time course within cells, which is highly associated with the surface coating of ZVI NPs and lysosomal acidification.

Intrinsic Iron Release Is Associated with Lower Mortality in Patients with Stable Coronary Artery Disease-First Report on the Prospective Relevance of Intrinsic Iron Release

Intrinsic iron release is discussed to have favorable effects in coronary artery disease (CAD). The aim of this study was to evaluate the prognostic relevance of intrinsic iron release in patients with CAD. Intrinsic iron release was based on a definition including hepcidin and soluble transferrin receptor (sTfR). In a cohort of 811 patients with angiographically documented CAD levels of hepcidin and sTfR were measured at baseline. Systemic body iron release was defined as low levels of hepcidin (<24 ng/mL) and high levels of sTfR (≥2 mg/L). A commercially available ELISA (DRG) was used for measurements of serum hepcidin. Serum sTfR was determined by using an automated immunoassay (). Cardiovascular mortality was the main outcome measure. The criteria of intrinsic iron release were fulfilled in 32.6% of all patients. Significantly lower cardiovascular mortality rates were observed in CAD patients with systemic iron release. After adjustment for body mass index, smoking status, hypertension, diabetes, dyslipidemia, sex, and age, the hazard ratio for future cardiovascular death was 0.41. After an additional adjustment for surrogates of the size of myocardial necrosis (troponin I), anemia (hemoglobin), and cardiac function and heart failure severity (N-terminal pro B-type natriuretic peptide), this association did not change (Hazard ratio 0.37 (95% confidence interval 0.14⁻0.99), p = 0.047). In conclusion, significantly lower cardiovascular mortality rates were observed in CAD patients with intrinsic iron release shown during follow-up.

Cancer cell death induced by ferritins and the peculiar role of their labile iron pool

Cellular uptake of human H-ferritin loaded with 50 or 350 iron ions results in significant cytotoxicity on HeLa cells at submicromolar concentrations. Conversely, Horse Spleen Ferritin, that can be considered a model of L-cages, as it contains only about 10% of H subunits, even when loaded with 1000 iron ions, is toxic only at >1 order of magnitude higher protein concentrations. We propose here that the different cytotoxicity of the two ferritin cages originates from the presence in H-ferritin of a pool of non-biomineralized iron ions bound at the ferroxidase catalytic sites of H-ferritin subunits. This iron pool is readily released during the endosomal-mediated H-ferritin internalization.

Iron Release from Soybean Seed Ferritin Induced by Cinnamic Acid Derivatives

Plant ferritin represents a novel class of iron supplement, which widely co-exists with phenolic acids in a plant diet. However, there are few reports on the effect of these phenolic acids on function of ferritin. In this study, we demonstrated that cinnamic acid derivatives, as widely occurring phenolic acids, can induce iron release from holo soybean seed ferritin (SSF) in a structure-dependent manner. The ability of the iron release from SSF by five cinnamic acids follows the sequence of Cinnamic acid > Chlorogenic acid > Ferulic acid > p-Coumaric acid > Trans-Cinnamic acid. Fluorescence titration in conjunction with dialysis results showed that all of these five compounds have a similar, weak ability to bind with protein, suggesting that their protein-binding ability is not related to their iron release activity. In contrast, both Fe²⁺-chelating activity and reducibility of these cinnamic acid derivatives are in good agreement with their ability to induce iron release from ferritin. These studies indicate that cinnamic acid and its derivatives could have a negative effect on iron stability of holo soybean seed ferritin in diet, and the Fe²⁺-chelating activity and reducibility of cinnamic acid and its derivatives have strong relations to the iron release of soybean seed ferritin.

The putative siderophore-interacting protein from Vibrio anguillarum: protein production, analysis, crystallization and X-ray crystallographic studies

Siderophore-interacting proteins (SIPs) play an important role in iron acquisition in many bacteria. SIPs release iron from the internalized ferric siderophore complex by reducing ferric iron to ferrous iron, but how the iron is reduced is not well understood. Here, a sip gene was identified in the genome of Vibrio anguillarum 775. To further understand the catalytic mechanism of the protein, the SIP was overexpressed in Escherichia coli Rosetta (DE3) cells, purified and crystallized for X-ray diffraction analysis. The crystal diffracted to 1.113 Å resolution and belonged to space group P21, with unit-cell parameters a = 64.63, b = 58.47, c = 70.65 Å, β = 114.19°.

[Relative Importance of Factors Influencing Iron Release in Drinking Water Distribution Systems]

Iron release in drinking water distribution systems (DWDSs) has attracted significant attention in recent years. There are many factors influencing iron release in DWDSs. In this study, we select pH, dissolved oxygen (DO), alkalinity (Alk), hardness, chloride (Cl^-), sulfate (SO₄^2-), temperature (T), and hydraulic retention time (HRT) as factors to investigate. Stepwise regression and partial correlation analysis are used as methods for establishing nonlinear power exponent iron release models and determining the relative importance of these factors by comparing standardized regression coefficients and partial correlation coefficients. The results show that the iron release models fit well. The important factors are SO₄^2-, HRT, Cl^-, and T, and the relative importance of the effect of the factors on iron release is SO₄^2-≈HRT > Cl^- > T, when measured by standardized regression coefficients; whereas, the important factors are HRT, SO₄^2-, Alk, Cl^-, and T, and the order of importance is HRT > SO₄^2- > Alk > Cl^- > T, when measured by partial correlation coefficients. Combining these two results, we conclude HRT, SO₄^2-, and Cl^- are the most important factors affecting iron release in pipes for the conditions in this study. The relative importance of T and Alk changes depending on the actual situation.

Iron Acquisition Strategies of Vibrio anguillarum

The hemorrhagic septicemic disease vibriosis caused by Vibrio anguillarum shows noticeable similarities to invasive septicemia in humans, and in this case, the V. anguillarum–host system has the potential to serve as a model for understanding native eukaryotic host–pathogen interactions. Iron acquisition, as a fierce battle occurring between pathogenic V. anguillarum and the fish host, is a pivotal step for virulence. In this article, advances in defining the roles of iron uptake pathways in growth and virulence of V. anguillarum have been summarized, divided into five aspects, including siderophore biosynthesis and secretion, iron uptake, iron release, and regulation of iron uptake. Understanding the molecular mechanisms of iron acquisition will have important implications for the pathogenicity of this organism.