Alteration of human serum albumin binding properties induced by modifications: A review

A nomogram including admission serum glycated albumin/albumin ratio to predict mortality in patients with severe fever with thrombocytopenia syndrome

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is a novel tick-borne infectious disease with a high fatality rate. Although several nomograms based on demographic and laboratory data have been reported to predict the prognosis of SFTS in recent studies, baseline serum glycated albumin (GA)/albumin (ALB) ratio included risk model has not been evaluated for the prediction of clinical outcome.

METHODS

A total of 214 SFTS patients with integral data admitted to our hospital from May, 2020 to November, 2022 were included in this study. SFTS infection was confirmed by real time fluorescent quantitative PCR (qRT-PCR). The demographic characteristics, clinical and laboratory data were collected with in 24 h of admission and 1 to 2 days before discharge and were analysed retrospectively.

RESULTS

Fiffty-seven patients (26.6%) died. Multivariate logistic regression analysis showed that age, aspartate aminotransferase (AST), blood glucose (GLU), GA/ALB ratio, neutrophil counts (NEU) and lymphocyte percentage (LYM%) were the independent risk factors for mortality. A nomogram by these factors was created using RMS package in the R program. Area under the receiver operating characteristic (ROC) curve (AUC) of this nomogram was 0.88 (95% CI: 0.83, 0.93). This model showed the excellent net benefit, as revealed by the decision curve analysis. GA/ALB ratios were also independent risk factors for poor out clinical come in subgroups of patients with hyperglycemia on admission and with diabetes history. Nomograms were constructed by the independent risk factors in the subgroups. AUCs of the nomograms in the subgroups showed high predictive values for adverse prognosis.

CONCLUSIONS

GA/ALB ratios were independent risk factors for mortality in all SFTS patients and subgroups of with hyperglycemia on admission and diabetes history. The nomograms including GA/ALB ratio had high predictive value for adverse clinical outcome.The nomograms provide a basis for clinical decision-making for the treatment of SFTS patients in different clinical settings.

Tannin-albumin particles as stable carriers of medicines

Background: The effectiveness of a drug is dependent on its accumulation at the site of therapeutic action, as well as its time in circulation. The aim of the research was the creation of stable albumin/tannin (punicalagin, punicalin) particles, which might serve for the delivery of medicines. Methods: Numerous chromatographic and analytical methods, docking analyses and in vivo testing were applied and used. Results: Stable tannin-albumin/medicine particles with a diameter of ∼100 nm were obtained. The results of in vivo experiments proved that tannin-albumin particles are more stable than albumin particles. Conclusion: Based on the experiments and docking analyses, these stable particles can carry an extended number of medicines, with diverse chemical structures.

Inhibition of toxic metal-alpha synuclein interactions by human serum albumin

Human serum albumin (HSA), the most abundant protein in plasma and cerebrospinal fluid, not only serves as a crucial carrier of various exogenous and endogenous ligands but also modulates the aggregation of amyloidogenic proteins, including alpha synuclein (αSyn), which is associated with Parkinson's disease and other α-synucleinopathies. HSA decreases αSyn toxicity through the direct binding to monomeric and oligomeric αSyn species. However, it is possible that HSA also sequesters metal ions that otherwise promote aggregation. Cu(ii) ions, for example, enhance αSyn fibrillization in vitro, while also leading to neurotoxicity by generating reactive oxygen species (ROS). However, it is currently unclear if and how HSA affects Cu(ii)-binding to αSyn. Using an integrated set of NMR experiments, we show that HSA is able to chelate Cu(ii) ions from αSyn more efficiently than standard chelators such as EDTA, revealing an unexpected cooperativity between the HSA metal-binding sites. Notably, fatty acid binding to HSA perturbs this cooperativity, thus interfering with the sequestration of Cu(ii) ions from αSyn. We also observed that glycation of HSA diminished Cu(ii)-binding affinity, while largely preserving the degree of cooperativity between the HSA metal-binding sites. Additionally, our results show that Cu(ii)-binding to HSA stabilizes the interactions of HSA with αSyn primarily at two different regions, i.e. the N-terminus, Tyr 39 and the majority of the C-terminus. Our study not only unveils the effect of fatty acid binding and age-related posttranslational modifications, such as glycation, on the neuroprotective mechanisms of HSA, but also highlights the potential of αSyn as a viable NMR-based sensor to investigate HSA-metal interactions.

Translational Challenges and Prospective Solutions in the Implementation of Biomimetic Delivery Systems

Biomimetic delivery systems (BDSs), inspired by the intricate designs of biological systems, have emerged as a groundbreaking paradigm in nanomedicine, offering unparalleled advantages in therapeutic delivery. These systems, encompassing platforms such as liposomes, protein-based nanoparticles, extracellular vesicles, and polysaccharides, are lauded for their targeted delivery, minimized side effects, and enhanced therapeutic outcomes. However, the translation of BDSs from research settings to clinical applications is fraught with challenges, including reproducibility concerns, physiological stability, and rigorous efficacy and safety evaluations. Furthermore, the innovative nature of BDSs demands the reevaluation and evolution of existing regulatory and ethical frameworks. This review provides an overview of BDSs and delves into the multifaceted translational challenges and present emerging solutions, underscored by real-world case studies. Emphasizing the potential of BDSs to redefine healthcare, we advocate for sustained interdisciplinary collaboration and research. As our understanding of biological systems deepens, the future of BDSs in clinical translation appears promising, with a focus on personalized medicine and refined patient-specific delivery systems.

Ternary Cobalt (II)-Metformin-Glycine/Histidine/Proline Complexes: Multispectroscopic DNA, HSA, and BSA Interaction and Cytotoxicity Studies

The synthesized water-soluble ternary complexes [Co(met)(gly)(Cl)2] (1), [Co(met)(hist)(Cl)2] (2), and [Co(met)(pro)(Cl)2] (3), (met = metformin, gly = glycine, hist = histidine, and pro = proline) were evaluated using spectro-analytical techniques, and the stereochemistry of the complexes was determined to be octahedral. UV-Vis absorption, competitive DNA-binding experiments using ethidium bromide (EB) by fluorescence, fluorescence emission studies, viscosity studies, and gel electrophoresis techniques were all employed to explore the binding characteristics of the cobalt (II) complexes with CT-DNA and groove-binding mechanism established. The salt-dependent association of the complexes to CT-DNA was investigated using UV-Vis spectrophotometric analysis. The association of the cobalt (II) complexes with BSA and HSA was explored by utilizing UV-Vis absorption and fluorescence spectroscopy approaches. The findings show that the complexes exhibit adequate capacity to quench BSA and HSA fluorescence and that the binding response is mostly a static quenching mechanism. The cytotoxicity of the complexes has also been appraised with the human breast adenocarcinoma cell lines (MCF-7) and (MDA-MB-231) by utilizing the MTT assay. For each cell line, the IC50 values were computed. In both cell lines, all the complexes were active.

Discovery of novel glucosinolates inhibiting advanced glycation end products: Virtual screening and molecular dynamic simulation

Protein glycation can result in the formation of advanced glycation end products (AGEs), which pose a potential health risk due to their association with diabetic complications. Natural products are a source of drugs discovery and the search for potential natural inhibitors of AGEs is of great significance. Glucosinolates (GSLs) mainly from cruciferous plants have potential antioxidant, anti-inflammatory, and anti-glycation activities. In this study, the inhibitory activity of GSLs on bovine serum albumin (BSA) along with its mechanism was investigated by virtual screening and various computational simulation techniques. Virtual screening revealed that 174 GSLs were screened using Maestro based on the glide score and 89% of the compounds were found to have potential anti-glycation ability with the docking scores less than -5 kcal/mol. Molecular docking showed that the top 10 GSLs were bound to the IIA structural domain of BSA. Among them, glucohesperin (1) and 2-hydroxyethyl glucosinolate (2) had the lowest docking scores of -9.428 and -9.333 kcal/mol, respectively, reflecting their good binding affinity. Molecular dynamics simulations of 1 (ΔG = -43.46 kcal/mol) and 2 (ΔG = -43.71 kcal/mol) revealed that the complexes of these two compounds with proteins had good stability. Further binding site analysis suggested that the mechanism of inhibition of protein glycation by these two active ingredients might be through competitive hydrogen bonding to maintain the structural integrity of the protein, thus inhibiting glycation reaction. Moreover, the ADMET values and CYP450 metabolism prediction data were within the recommended values. Therefore, it can be concluded that 1 and 2 may act as potential anti-glycation agents.

Characterization of binding by sulfonylureas with normal or modified human serum albumin using affinity microcolumns prepared by entrapment

Modification of proteins can occur during diabetes due to the formation of advanced glycation end-products (AGEs) with reactive dicarbonyls such as glyoxal (Go) and methylglyoxal (MGo). Human serum albumin (HSA) is a serum protein that binds to many drugs in blood and that is known to be modified by Go and MGo. This study examined the binding of various sulfonylurea drugs with these modified forms of HSA by using high-performance affinity microcolumns prepared by non-covalent protein entrapment. Zonal elution experiments were employed to compare the retention and overall binding constants for the drugs with Go- or MGo-modified HSA vs normal HSA. The results were compared to values from the literature, such as measured or estimated using affinity columns containing covalently immobilized HSA or biospecifically-adsorbed HSA. The entrapment-based approach provided estimates of global affinity constants within 3-5 min for most of the tested drugs and with typical precisions of ±10-23%. Each entrapped protein microcolumn was stable for over at least 60-70 injections and one month of use. The results obtained with normal HSA agreed at the 95% confidence level with global affinity constants that have been reported for the given drugs in the literature. It was found for HSA that had been modified with clinically-relevant levels of either Go or MGo that an increase in the global affinity constant of up to 2.1-fold occurred for some of the tested drugs. The information acquired in this study can be used in the future to adapt this entrapment-based approach to study and evaluate interactions between other types of drugs and normal or modified binding agents for clinical testing and biomedical research.

Production of WE43 magnesium alloy by powder metallurgy and the effect of glucose on wear resistance in biocorrosive wear

In this study, WE43 magnesium alloy was produced by the powder metallurgy method. Microstructural analyses of the produced samples were carried out using the scanning electron microscopy method. X-ray fluorescence, energy dispersive x-ray (EDS) analysis, and hardness tests were also implemented to investigate the physical and chemical properties of the alloys. The volumetric hardness was measured to be approximately 53 HV. The microstructural analysis and EDS results indicated the presence of Mg24Y5 and Mg41Nd5 phases in the alloys. Reciprocating-type experiments were carried out in dry and corrosive environments to evaluate the wear resistance. Hanks’s solution containing 2% g/l glucose was used as the corrosive environment. Gluconic acid resulting from the oxidation of glucose in the Hanks’s solution formed a new thin layer on the alloy surface, which was observed in the worn surface images. The formation of the thin film on the alloy surface resulted in an increase in wear resistance by 37%. The results unraveled the potential of the WE43 alloys as implant materials in areas in contact with glucose.

New look at the metabolism of nonsteroidal anti-inflammatory drugs: influence on human serum albumin antioxidant activity

Body's homeostasis is dependent on many factors, such as maintaining balance between free radicals formation and degradation. Human serum albumin (HSA) also plays an important role in homeostasis. The aim of this study was thermodynamic analysis of the interaction between ketoprofen (KET), naproxen (NPX), diclofenac (DIC) and HSA, as well as the effect of drug-albumin binding on HSA antioxidant activity using calorimetric and spectrophotometric techniques. Based on the calorimetric analysis it has been shown that accompanied by hydrophobic interaction drugs-albumin binding is an exoenergetic reaction. All analyzed drugs and HSA showed the ability to react with free radicals such as a radical cation, formed as a result of the reaction between 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and potassium persulfate (K₂S₂O₈). Using ABTS assay a synergistic effect of ketoprofen (KET) and naproxen (NPX) on HSA antioxidant activity was observed while the effect of diclofenac (DIC) binding with albumin was probably additive. Because some medications including KET, NPX and DIC belong to over the counter (OTC) non-steroidal anti-inflammatory drugs (NSAIDs), it is necessary to understand their influence on HSA antioxidant activity.Communicated by Ramaswamy H. Sarma.

Protein sustained release from isobutyramide-grafted stellate mesoporous silica nanoparticles

Proteins are great therapeutic candidates as endogenous biomolecules providing a wide range of applications. However, their delivery suffers from some limitations and specifically designed delivery systems having an efficient protein anchoring and delivery strategy are still needed. In this work, we propose to combine large pore stellate mesoporous silica (STMS) with isobutyramide (IBAM), as a "glue" molecule which has been shown promising for immobilization of various biomacromolecules at silica surface. We address here for the first time the ability of such IBAM-modified NPs to sustainably deliver proteins over a prolonged time. In this work, a quantitative loading study of proteins (serum albumin (HSA), peroxidase (HRP), immunoglobulin (IgG) and polylysine (PLL)) on STMS@IBAM is first presented using three complementary detection techniques to ensure precision and avoid protein quantification issues. The results demonstrated a high loading capacity for HSA and HRP (≥ ca. 350 μg.mg-1) but a moderate one for IgG and PLL. After evaluating the physicochemical properties of the loaded particles and their stability over scaling-up and washings, the ability of STMS@IBAM to release proteins over prolonged time was evaluated in equilibrium (static) and flow mimicking (dynamic) conditions and at different temperatures (25, 37, 45 °C). Results show not only the potential of such "glue" functionalized STMS to release proteins in a sustained way, but also the retention of the biological activity of immobilized and released HRP, used as an enzyme model. Finally, an AFM-force spectroscopy study was conducted to decipher the interactions between IBAM and proteins, showing the involvement of different interactions in the adsorption and release processes.

Elucidation of the binding mechanism of astragaloside IV derivative with human serum albumin and its cardiotoxicity in zebrafish embryos

LS-102 is a new derivative of astragaloside IV (AGS IV) that has been shown to possess potentially significant cardioprotective effects. However, there are no reports concerning its interaction with human serum albumin (HSA) and toxicology in vertebrates. The present investigation was undertaken to characterize the interaction of AGS IV and LS-102 with HSA using equilibrium dialysis and UHPLC-MS/MS methods, along with computational methods. Notably, the effects of AGS IV and LS-102 were studied in vivo using the zebrafish embryo model. Markers related to embryonic cardiotoxicity and thrombosis were evaluated. We showed that the plasma protein binding rate of AGS IV (94.04%–97.42%) was significantly higher than that of LS-102 (66.90%–69.35%). Through site marker competitive experiments and molecular docking, we found that AGS IV and LS-102 were located at the interface of subdomains IIA and IIIA, but the site I might be the primary binding site. Molecular dynamics revealed that AGS IV showed a higher binding free energy mainly due to the stronger hydrophobic and hydrogen bonding interactions. Moreover, the secondary structure implied no obvious effect on the protein structure and conformation during the binding of LS-102. LS-102 significantly ameliorated the astramizole-induced heart rate slowing, increased SV-BA spacing, and prevented arachidonic acid-induced thrombosis in zebrafish. To our knowledge, we are the first to reveal that LS-102 binds to HSA with reversible and moderate affinity, indicating its easy diffusion from the circulatory system to the target tissue, thereby providing significant insights into its pharmacokinetic and pharmacodynamic properties when spread in the human body. Our results also provide a reference for the rational clinical application of LS-102 in the cardiovascular field.

New Materials Based on Molecular Interaction between Hyaluronic Acid and Bovine Albumin

In this work, the interactions between hyaluronic acid and bovine serum albumin were investigated. The film-forming properties of the mixture were proven, and the mechanical and surface properties of the films were measured. The results showed the interactions between hyaluronic acid and albumin, mainly by hydrogen bonds. Molecular docking was used for the visualization of the interactions. The films obtained from the mixture of hyaluronic acid possessed different properties to films obtained from the single component. The addition of bovine serum albumin to hyaluronic acid led to a decrease in the mechanical properties, and to an increase in the surface roughness of the film. The new materials that have been obtained by blending can form a new group of materials for biomedicine and cosmetology.

Comprehensive profiling and kinetic studies of glycated lysine residues in human serum albumin

Lysine residues of proteins slowly react with glucose forming Amadori products. In hyperglycemic conditions, such as diabetes mellitus, this non-enzymatic glycation becomes more pervasive causing severe medical complications. The structure and conformation of a protein predisposes lysine sites to differing reactivity influenced by their steric availability and amino acid microenvironment. The goal of our study was to identify these sites in albumin and measure glycation affinities of lysine residues. We applied a bottom-up approach utilizing a combination of three LC-MS instruments: timsTOF, Orbitrap, and QTRAP. To prove applicability to samples of varying glycemic status, we compared in vitro glycated and non-glycated HSA, as well as diabetic and non-diabetic individual samples. The analysis of lysine glycation affinities based on peptide intensities provide a semi-quantitative approach, as the results depend on the mass spectrometry platform used. We found that glycation levels based on multiple reaction monitoring (MRM) quantitation better reflect individual glycemic status and that the glycation percentage for each site is in linear relation to all other sites. To develop an approach which more accurately reflects glycation affinity, we developed a kinetics model which uses results from stable isotope dilution HPLC-MRM methodology. Through glycation of albumin at different glucose concentrations, we determine the rate constants of glycation for every lysine residue by simultaneous comparative analysis.

The Influence of Coronary Artery Disease in the Development of Aortic Stenosis and the Importance of the Albumin Redox State

Calcific aortic valve and coronary artery diseases are related cardiovascular pathologies in which common processes lead to the calcification of the corresponding affected tissue. Among the mechanisms involved in calcification, the oxidative stress that drives the oxidation of sulfur-containing amino acids such ascysteines is of particular interest. However, there are important differences between calcific aortic valve disease and coronary artery disease, particularly in terms of the reactive oxygen substances and enzymes involved. To evaluate what effect coronary artery disease has on aortic valves, we analyzed valve tissue from patients with severe calcific aortic stenosis with and without coronary artery disease. Proteins and peptides with oxidized cysteines sites were quantified, leading to the identification of 16 proteins with different levels of expression between the two conditions studied, as well as differences in the redox state of the tissue. We also identified two specific sites of cysteine oxidation in albumin that have not been described previously. These results provide evidence that coronary artery disease affects valve calcification, modifying the molecular profile of aortic valve tissue. In addition, the redox proteome is also altered when these conditions coincide, notably affecting human serum albumin.

Dynamic Protein and Polypeptide Hydrogels Based on Schiff Base Co-assembly for Biomedicine

Stimuli-responsive hydrogels are promising building blocks for biomedical devices, attributable to their excellent hydrophilicity, biocompatibility, and dynamic responsiveness to temperature, light, pH, and water content. Although hydrogels find interesting applications...

Albumin-binding tag derived Exendin-4 analogue for treating hyperglycemia and diabetic complications

Current study was conducted to design and screen a long-lasting Exendin-4 analog for treating type 2 diabetes via the novel strategy of albumin binding combined with thrombin enzymolysis. First, a series of fusion peptides, containing different albumin-binding tags, a determinate thrombin-cleavable linker and a native Exendin-4, were prepared via chemosynthesis for in vitro and in vivo characterization. Surface plasmon resonance assay, thrombin cleavage assay and plasma stability test were performed for screening the optimal HEX peptide with enhanced albumin-binding affinity, controlled-release as well as plasma stability. The in vivo anti-diabetic efficacies of the selected candidate were further assessed via both acute and chronic pharmacodynamic evaluation in diabetic model animals. HEX15 exhibited either the highest affinity for human serum albumin or the superior in vitro stability and controlled release of Exendin-4 among 21 HEX peptides. Glucose tolerance test and hypoglycemic duration assay both revealed the notably improved the glucose tolerance and prolonged normoglycemic duration, respectively, of diabetic mice after single treatment of HEX15. Furthermore, chronic dosing of HEX15 significantly ameliorated the manifestations of diabetes in the db/db mice, including body weight, food intake, glycometabolism as well as hyperlipemia. Interestingly, combination therapy of HEX15 and long non-coding RNA-ENST00000411554 notably accelerated the wound healing and improved foot ulcer symptoms in model rats with diabetic foot ulcers. In summary, based on the strategy of linking the heptapeptide tag and thrombin-based sustained release, a long-acting Exendin-4 analog, HEX15, holds potential to be developed as a drug for ameliorating T2D as well as diabetic complications.

Comprehensive insights into the interactions of dicyclohexyl phthalate and its metabolite to human serum albumin

Phthalate esters (PAEs) are a type of persistent organic pollutants and have received widespread concerns due to their adverse effects on human health. Dicyclohexyl phthalate (DCHP) and its metabolite monocyclohexyl phthalate (MCHP) were selected to explore the mechanism for interaction of PAEs with human serum albumin (HSA) through molecular docking and several spectroscopic techniques. The results showed that DCHP/MCHP can spontaneously occupy site I to form a binary complex with HSA, and DCHP exhibited higher binding affinity to HSA than MCHP. At 298 K, the binding constants (K_b) of DCHP and MCHP to HSA were 24.82 × 10⁴ and 1.04 × 10⁴ M^-1, respectively. Hydrogen bonds and van der Waals forces were the major driving forces in DCHP/MCHP-HSA complex. The presence of DCHP/MCHP induced the secondary structure changes in HSA, and the pi electrons of the benzene ring skeleton of DCHP/MCHP played a key role in this binding processes. Exposure of DCHP/MCHP to TM4 cells revealed that interactions between PAEs and serum albumin can affect their cytotoxicity; DCHP showed higher toxicity than MCHP. The binding affinity of PAEs with HSA may be a valuable parameter for rapid assessment of their toxicity to organisms.

Thermodynamic and kinetic insights into the interactions between functionalized CdTe quantum dots and human serum albumin: A surface plasmon resonance approach

To explore in vivo application of quantum dots (QDs), it is essential to understand the dynamics and energetics of interactions between QDs and proteins. Here, surface plasmon resonance (SPR) and molecular docking were employed to investigate the kinetics and thermodynamics of interactions between human serum albumin (HSA) and CdTe QDs (~3 nm) functionalized with mercaptopropionic acid (MPA) or thioglycolic acid (TGA). Kinetic analysis showed that HSA-QD interactions involved transition-complex formation. Despite the structural similarities between MPA and TGA, the [HSA-CdTe@TGA]^‡ formation by association of free HSA and QDs demanded 70% more energy and higher entropic gain (E_a-TGA^‡= 65.10 and T∆S_a-TGA^‡= 28.62 kJ mol^-1) than the formation of [HSA-CdTe@MPA]^‡ (E_a-MPA^‡ = 38.13 and T∆S_a-MPA^‡ = 0.53kJ mol^-1). While the [HSA-CdTe@MPA]^° dissociation required higher energy and lower entropy loss (E_d-MPA^‡ = 49.96 and T∆S_d-MPA^‡ = - 32.18kJ mol^-1) than the [HSA-CdTe@TGA]^° dissociation (E_d-TGA^‡= 30.78 and T∆S_d-TGA^‡= - 51.12 kJ mol^-1). The stability of [HSA-QDs]^° was independent of the temperature and functionalizing group. However, the enthalpic and entropic components were highly affected by the substitution of MPA (ΔH° = - 11.83 and TΔS° = 32.72 kJ mol^-1) with TGA (ΔH° = 34.31 and TΔS° = 79.73 kJ mol^-1). Furthermore, molecular docking results indicated that the metal site on the QDs contributes to the stabilization of [HSA-QDs]^°. Therefore, differences in QD functionalization and surface coverage densities can alter the HSA-QD interaction, thus their application.

Glycation of albumin and its implication in Diabetes: A comprehensive analysis using mass spectrometry

AIM

To understand the mechanism of glycation of albumin and effects on cysteinylation and methionine oxidation.

METHODS

The in vitro glycation of HSA and BSA was studied with varying concentrations of glucose. Clinical blood samples of diabetic subjects with varying HbA1c values, were analyzed to assess in vivo glycation. All samples and their tryptic digests were analyzed using liquid chromatography/mass spectrometry. Glycation sites were mapped on to the three-dimensional structure of the HSA and BSA.

RESULTS

A total thirty-one sites for glycation and eight sites of N^ε-carboxymethyl-lysine (CML) modification were identified on albumin. The site selectivity of glycation was correlated with the environment of the reactive residue in the three-dimensional structure.

CONCLUSIONS

The maximum percentage glycation under extreme conditions was in the range of ~55 to 88% in four weeks. Two major glycation sites K-233 and K-525 were identified, which together accounted for 40-50% of total glycation. A correlation was observed between glycation and oxidation of methionine residues in samples glycated in vitro. The role of spatially proximate residues in facilitating the glycation process is evident. The tri- and tetra-glycated isoforms of albumin can serve as biomarkers for the severe uncontrolled diabetic state.

One-step construction of a food-grade expression system based on the URA3 gene in Kluyveromyces lactis

Proteins from food-grade expression systems can be used in food products and medical applications. Herein, we describe a one-step method of constructing an expression vector in Kluyveromyces lactis by combining a URA3-deficient strain and a plasmid vector with no drug-resistant selection. Adjacent DNA elements of the vector were assembled in a targeted manner through a reaction with a special recombinase to form a plasmid vector using a one-step reaction. The unnecessary fragments containing the pUC origin and the ampicillin resistance gene were removed, and the vector was isolated and purified before transformation. A single transformation of the vector can produce a URA3-deficient strain. PCR assay, sequencing, and western blot analysis all indicated that the method of vector construction and target protein expression (mCherry and human serum albumin) were successful. This method may potentially be applied to any species containing the URA3 gene; this system has the potential to become a safe and powerful tool for promoting protein expression in food-safe species.

The Influence of Oxidative Stress on Serum Albumin Structure as a Carrier of Selected Diazaphenothiazine with Potential Anticancer Activity

Albumin is one of the most important proteins in human blood. Among its multiple functions, drug binding is crucial in terms of drug distribution in human body. This protein undergoes many modifications that are certain to influence protein activity and affect its structure. One such reaction is albumin oxidation. Chloramine T is a strong oxidant. Solutions of human serum albumin, both non-modified and modified by chloramine T, were examined with the use of fluorescence, absorption and circular dichroism (CD) spectroscopy. 10H-3,6-diazaphenothiazine (DAPT) has anticancer activity and it has been studied for the first time in terms of binding with human serum albumin—its potential as a transporting protein. Using fluorescence spectroscopy, in the presence of dansylated amino acids, dansyl-l-glutamine (dGlu), dansyl-l-proline (dPro), DAPT binding with two main albumin sites—in subdomain IIA and IIIA—has been evaluated. Based on the conducted data, in order to measure the stability of DAPT complexes with human (HSA) and oxidized (oHSA) serum albumin, association constant (K_a) for ligand-HSA and ligand-oHSA complexes were calculated. It has been presumed that oxidation is not an important issue in terms of 10H-3,6-diazaphenothiazine binding to albumin. It means that the distribution of this substance is similar regardless of changes in albumin structure caused by oxidation, natural occurring in the organism.

Oxidized Albumin as a Mediator of Kidney Disease

Renal diseases are a global health concern, and nearly 24% of kidney disease patients are overweight or obese. Particularly, increased body mass index has been correlated with oxidative stress and urinary albumin excretion in kidney disease patients, also contributing to increased cardiovascular risk. Albumin is the main plasma protein and is able to partially cross the glomerular filtration barrier, being reabsorbed mainly by the proximal tubule through different mechanisms. However, it has been demonstrated that albumin suffers different posttranslational modifications, including oxidation, which appears to be tightly linked to kidney damage progression and is increased in obese patients. Plasma-oxidized albumin levels correlate with a decrease in estimated glomerular filtration rate and an increase in blood urea nitrogen in patients with chronic kidney disease. Moreover, oxidized albumin in kidney disease patients is independently correlated with higher plasma levels of transforming growth factor beta (TGF-β1), tumor necrosis factor (TNF-α), and interleukin (IL)-1β and IL-6. In addition, oxidized albumin exerts a direct effect on neutrophils by augmenting the levels of neutrophil gelatinase-associated lipocalin, a well-accepted biomarker for renal damage in patients and in different experimental settings. Moreover, it has been suggested that albumin oxidation occurs at early stages of chronic kidney disease, accelerating the patient requirements for dialytic treatment during disease progression. In this review, we summarize the evidence supporting the role of overweight- and obesity-induced oxidative stress as a critical factor for the progression of renal disease and cardiovascular morbimortality through albumin oxidation.

Effect of antioxidants on preimplantation embryo development in vitro: a review

In vitro culture of the embryo is a useful method to treat infertility that shows embryo potential for selecting the best one to transfer and successfully implantation. However, embryo development in vitro is affected by oxidative stresses such as reactive oxygen species that may damage embryo development. Antioxidants are molecules found in fruits, vegetables, and fish that play an important role in reducing oxidative processes. In the natural environment, there is a physiological antioxidant system that protects embryos against oxidative damage. This antioxidant system does not exist in vitro. Antioxidants act as free radical scavengers and protect cells or repair damage done by free radicals. Various studies have shown that adding antioxidants into embryo culture medium improves embryo development in vitro. This review article emphasizes different aspects of various antioxidants, including types, functions and mechanisms, on the growth improvement of different species of embryos in vitro.

Synthesis, DNA/RNA-interaction and biological activity of benzo[k,l]xanthene lignans

Interactions of two newly synthesized and six previously reported benzoxanthene lignans (BXLs), analogues of rare natural products, with DNA/RNA, G-quadruplex and HSA were evaluated by a set of spectrophotometric methods. Presence/absence of methoxy and hydroxy groups on the benzoxanthene core and minor modifications at C-1/C-2 side pendants - presence/absence of phenyl ring and presence/absence of methoxy and hydroxy groups on phenyl ring - influenced the fluorescence changes and the binding strength to double-stranded (ds-) and G-quadruplex structures. In general, compounds without phenyl ring showed stronger fluorescence changes upon binding than phenyl-substituted BXLs. On the other hand, BXLs with an unsubstituted phenyl ring showed the best stabilization effects of G-quadruplex. Circular dichroism spectroscopy results suggest mixed binding mode, groove binding and partial intercalation, to ds-DNA/RNA and end-stacking to top or bottom G-tetrads as the main binding modes of BXLs to those targets. All compounds exhibited micromolar binding affinities toward HSA and an increased protein thermal stability. Moderate to strong antiradical scavenging activity was observed for all BXLs with hydroxy groups at C-6, C-9 and C-10 positions of the benzoxanthene core, except for derivative bearing methoxy groups at these positions. BXLs with unsubstituted or low-substituted phenyl ring and one derivative without phenyl ring showed strong growth inhibition of Gram-positive Staphylococcus aureus. All compounds showed moderate to strong tumor cell growth-inhibitory activity and cytotoxicity.

Albumin binding function is a novel biomarker for early liver damage and disease progression in non-alcoholic fatty liver disease

PURPOSE

Indicators to assess early liver damage and disease progression in nonalcoholic fatty liver disease (NAFLD) remain unsatisfactory. Albumin binding function has been reported to be an early indicator of liver damage in hepatitis and liver cirrhosis. However, its role in NAFLD patients is unknown.

METHODS

An age/sex-matched, case-control study was performed. Albumin-binding capacity (ABiC) and albumin metal ion binding ability, assessed by ischemia modified albumin (IMA), were measured. Correlation analysis was performed to assess the association of albumin binding function with liver function enzymes and noninvasive liver fibrosis markers.

RESULTS

A total of 80 NAFLD patients and 41 healthy controls were included. Albumin binding function was significantly lower in NAFLD (ABiC: 196.00%, p < 0.001; IMA transformed (IMAT): 0.461, p < 0.001; and IMAT/albumin: 0.947 × 10^-2, p < 0.001) than controls (ABiC: 211.00%; IMAT: 0.575; and IMAT/albumin: 1.206 × 10^-2). Albumin binding function was also found to be significantly different among healthy participants and different severity groups of NAFLD (p < 0.001). Besides, albumin binding function showed positive correlation with BMI (ABiC: r = -0.247, p = 0.011; IMAT: r = -0.243, p = 0.013; IMAT/albumin: r = -0.254, p = 0.009) and FIB-4 index (ABiC: r = 0.230, p = 0.029). The ROC curve suggested that albumin binding function combined with BMI and triglyceride may predict the presence of NAFLD (area under ROC (AUROC) = 0.935, p < 0.001).

CONCLUSION

Our findings suggest albumin binding function is a novel biomarker for early liver damage and disease progression in NAFLD.

Ligand binding to natural and modified human serum albumin

This paper reports evaluation of ligand binding constants for unmodified or biotinylated HSA (HSA_B) for two well-known HSA binding ligands, naproxen and bromocresol green. Results demonstrate differential scanning calorimetry (DSC) is a reliable quantitative method for straight-forward and rapid evaluation of ligand binding constants for HSA and modified derivatives. DSC measured the thermodynamic stability of free and ligand-bound HSA and HSA_B at pH = 6.0, 7.4 and 8.0. DSC analysis provided a quantitative gauge of responses of HSA and HSA_B thermodynamic stability to ligand binding. The influence of different levels of biotinylation of HSA_B on ligand binding, and how ligand binding varied as a function of pH for these molecules was also examined. In the three pH environments, biotinylation increased stability of HSA_B alone compared to free HSA at pH 7.4. Stabilities of free protein and ligand-bound complexes varied with pH in the order, pH = 6.0>7.4>8.0. Our analytical approach provided very accurate estimates for known binding constants of these ligands for HSA. Results revealed, for both ligands, extent of biotinylation of HSA_B affected binding, reducing binding constants from three to 100-fold. DSC analysis was able to delineate inter-relationships between molecular structure and thermodynamic stability of HSA and HSA_B bound by ligands; and their variations with pH.

Growth of foetal bones and metabolic profile during gestation in primiparous ewes and multiparous ewes

Primiparous ewes and multiparous ewes show physiological differences during pregnancy, which can have an impact on the development of their offspring. The objective of this study was to compare the changes in the metabolic profile and in the size of some foetal bones throughout gestation between primiparous and multiparous ewes. Twelve primiparous (PM) ewes and 14 multiparous (MT) ewes were used. According to the dates of lambing, two groups of ewes were formed: Group 1 (G1, n = 6 PM and n = 7 MT) and Group 2 (G2, n = 6 PM and n = 7 MT). The body weight, body condition score, metabolic and foetal morphometric parameters were determined from before conception until the end of gestation. After lambing, the body weight and survival rate during the first 72 hr of life of lambs, as well as the maternal behaviour score were recorded. The PM ewes were lighter (p < .01) and had a greater mobilization of body reserves during gestation, mainly evidenced by a greater serum concentration of NEFAs and lower serum concentration of total proteins (p < .05) compared with the MT ewes. The parity did not affect the foetal morphometric variables. The lambs of MT ewes were heavier at parturition (p = .002) and tended to have a greater survival rate than those lambs of PM ewes (p = .09). In conclusion, PM ewes and MT ewes differ in their metabolic profile throughout the gestation. However, in the present study, we did not find parity differences in the dimensions of foetal bones during growth in gestation.

Impaired albumin function: a novel potential indicator for liver function damage?

Albumin is the most abundant plasma protein and albumin infusion is commonly used. Conventionally, the biologic and therapeutic effects of albumin have been thought to be due to its oncotic properties. However, albumin has a variety of biologic functions, including molecular transport, anti-oxidation, anti-inflammation, endothelial stabilisation, anti-thrombotic effects, and the adjustment of capillary permeability. Despite this, the functions of albumin have not been thoroughly investigated. Recent studies have shown non-alcoholic fatty liver disease (NAFLD), viral hepatitis, cirrhosis, and liver failure to be associated with impairments in albumin function, which are associated with impairments in liver function and disease prognosis. Post-translational modifications of albumin cause structural modifications that affect protein function. Recently, the concentration of albumin associated with normal function, the 'efficient albumin concentration', has been attracting more interest. In addition, although many biologic markers, including albumin concentration, are widely used for the assessment of early liver dysfunction in patients with liver diseases, the predictive values are unsatisfactory. However, clinical evidence has suggested that albumin function may represent a novel biomarker of early impairment in liver function. In this review, we summarise the factors affecting albumin function and discuss the clinical significance of impairments in albumin function in various liver diseases.Key messagesThe importance of albumin depends not only on its concentration, but also on its various physiological functions.Impaired albumin function has been reported in a variety of liver diseases, and is associated with disease severity and prognosis, thereby proposing the concept of 'effective albumin concentration'.Albumin dysfunction occurs earlier than other conventional indicators, and albumin dysfunction may be a new biomarker of early impairment in liver function.Many exogenous and endogenous factors lead to post-translational modifications of albumin, which alters the three-dimensional structure of albumin, resulting in a decrease in its biological activity.

An overview of albumin and alpha-1-acid glycoprotein main characteristics: highlighting the roles of amino acids in binding kinetics and molecular interactions

Although Albumin (ALB) and alpha-1-acid glycoprotein (AGP) have distinctive structural and functional characteristics, they both play a key role in binding a large variety of endogenous and exogenous ligands. An extensive binding to these plasma proteins could have a potential impact on drugs disposition (e.g. bioavailability, distribution and clearance), on their innocuity and their efficacy. This review summarizes the common knowledge about the structural and molecular characteristics of both ALB and AGP in humans, and about the most involved amino acids in their high-affinity binding pockets. However, the variability in residues found in binding pockets, for the same species, allows each plasma protein to interact differently with the ligands. The protein-ligand interaction influences differently the disposition of drugs that bind to either of these plasma proteins. The content of this review is useful for the design of new drug entities with high-binding characteristics, in qualitative and quantitative modelling (e.g. in vitro-in vivo extrapolations, 3D molecular docking, interspecies extrapolations), and for other interdisciplinary research.

Caffeic Acid Inhibits the Formation of Advanced Glycation End Products (AGEs) and Mitigates the AGEs-Induced Oxidative Stress and Inflammation Reaction in Human Umbilical Vein Endothelial Cells (HUVECs)

The advanced glycation end products (AGEs) are the compounds produced by non-enzymatic glycation reaction of proteins and sugars, which can induce the generation of free radicals and the expression of inflammatory factors, thereby playing an important role in vascular dysfunction in diabetes. To investigate the effects of caffeic acid (CA) on glycation formed by glucose and protein, various spectroscopic techniques and molecular docking methods were carried out. Furthermore, the protective effects of CA on human umbilical vein endothelial cells (HUVECs) damaged by AGEs were detected. The results indicated that CA inhibited AGEs formation in vitro, decreased the expression of IL-1β, IL-18, ICAM-1, VCAM-1, NLRP3, Caspase-1 and CRP (C-reactive protein) and reduced the ROS in HUVECs exposed to AGEs. Our findings suggested that the supplementation with dietary CA could prevent and delay the AGEs-induced vascular dysfunction in diabetes.

A next generation setup for pre-fractionation of non-denatured proteins reveals diverse albumin proteoforms each carrying several post-translational modifications

Proteomic biomarker search requires the greatest analytical reproducibility and detailed information on altered proteoforms. Our protein pre-fractionation applies orthogonal native chromatography and conserves important features of protein variants such as native molecular weight, charge and major glycans. Moreover, we maximized reproducibility of sample pre-fractionation and preparation before mass spectrometry by parallelization and automation. In blood plasma and cerebrospinal fluid (CSF), most proteins, including candidate biomarkers, distribute into a multitude of chromatographic clusters. Plasma albumin, for example, divides into 15-17 clusters. As an example of our technique, we analyzed these albumin clusters from healthy volunteers and from dogs and identified cluster-typical modification patterns. Renal disease further modifies these patterns. In human CSF, we found only a subset of proteoforms with fewer modifications than in plasma. We infer from this example that our method can be used to identify and characterize distinct proteoforms and, optionally, enrich them, thereby yielding the characteristics of proteoform-selective biomarkers.

Bound to bleed: How altered albumin binding may dictate warfarin treatment outcome

Although non-vitamin-K anticoagulants are now the preferred option for stroke prevention in atrial fibrillation (AF), warfarin is still used in a significant number of patients. Warfarin dosing requirements are susceptible to drug interactions and genetic polymorphisms in metabolising enzymes. Human serum albumin (HSA) is a candidate modifier of warfarin pharmacokinetics, with hypoalbuminemia now shown to correlate with supratherapeutic INR levels and annual bleeding risk. Warfarin is highly bound to HSA, and a relatively small shift, resulting from displacement by other xenobiotics, hypoalbuminemia or reduced binding capacity, can potentially lead to marked alterations in the free warfarin fraction. Precisely how this relates to the actual concentration of free, pharmacodynamically active, warfarin, is not clear, since measurement of this critical moiety remains an unsolved caveat. Yet awareness how disease, nutrition and polypharmacy affect warfarin binding to HAS and how this may impact (or not) on bioavailability and outcome, is essential for optimal treatment.

Recent advances in nanoengineering cellulose for cargo delivery

The recent decade has witnessed a growing demand to substitute synthetic materials with naturally-derived platforms for minimizing their undesirable footprints in biomedicine, environment, and ecosystems. Among the natural materials, cellulose, the most abundant biopolymer in the world with key properties, such as biocompatibility, biorenewability, and sustainability has drawn significant attention. The hierarchical structure of cellulose fibers, one of the main constituents of plant cell walls, has been nanoengineered and broken down to nanoscale building blocks, providing an infrastructure for nanomedicine. Microorganisms, such as certain types of bacteria, are another source of nanocelluloses known as bacterial nanocellulose (BNC), which benefit from high purity and crystallinity. Chemical and mechanical treatments of cellulose fibrils made up of alternating crystalline and amorphous regions have yielded cellulose nanocrystals (CNC), hairy CNC (HCNC), and cellulose nanofibrils (CNF) with dimensions spanning from a few nanometers up to several microns. Cellulose nanocrystals and nanofibrils may readily bind drugs, proteins, and nanoparticles through physical interactions or be chemically modified to covalently accommodate cargos. Engineering surface properties, such as chemical functionality, charge, area, crystallinity, and hydrophilicity, plays a pivotal role in controlling the cargo loading/releasing capacity and rate, stability, toxicity, immunogenicity, and biodegradation of nanocellulose-based delivery platforms. This review provides insights into the recent advances in nanoengineering cellulose crystals and fibrils to develop vehicles, encompassing colloidal nanoparticles, hydrogels, aerogels, films, coatings, capsules, and membranes, for the delivery of a broad range of bioactive cargos, such as chemotherapeutic drugs, anti-inflammatory agents, antibacterial compounds, and probiotics. SYNOPSIS: Engineering certain types of microorganisms as well as the hierarchical structure of cellulose fibers, one of the main building blocks of plant cell walls, has yielded unique families of cellulose-based nanomaterials, which have leveraged the effective delivery of bioactive molecules.

Influence of Piracetam on Gliclazide-Glycated Human Serum Albumin Interaction. A Spectrofluorometric Study

Advanced Glycation End-Products (AGEs) are created in the last step of protein glycation and can be a factor in aging and in the development or worsening of many degenerative diseases (diabetes, chronic kidney disease, atherosclerosis, Alzheimer’s disease, etc.). Albumin is the most susceptible to glycation plasma protein. Modified albumin by AGEs may be more resistant to enzymatic degradation, which further increases the local accumulation of AGEs in tissues. The aim of the present study was to analyze in vitro glycation of serum albumin in the presence of piracetam (PIR) and the gliclazide (GLZ)-glycated albumin interaction. The analysis of PIR as an inhibitor and GLZ interaction with nonglycated human albumin (HSA) and glycated by fructose human albumin (gHSA_FRC), in the absence and presence of piracetam (gHSA_FRC-PIR), was performed by fluorescence quenching of macromolecules. On the basis of obtained data we concluded that under the influence of glycation, association constant (Ka) of gliclazide to human serum albumin decreases and GLZ binds to HSA with less strength than under physiological conditions. PIR strongly inhibited the formation of AGEs in the system where the efficiency of HSA glycation was the largest. The analysis of piracetam influence on the GLZ-glycated albumin interaction has shown that piracetam increases the binding strength of GLZ to glycated albumin and weakens its therapeutic effect. Based on the obtained data we concluded that monitoring therapy and precautions are required in the treatment when the combinations of gliclazide and piracetam are used at the same time.

Binding mechanism of five typical sweeteners with bovine serum albumin

In this work, the interactions between bovine serum albumin (BSA) and five sweeteners including aspartame (APM), acesulfame (AK), sucralose (TGS), sodium cyclamate (SC), and rebaudioside-A (REB-A) have been studied by multispectroscopic techniques, and molecular simulation in order to provide much useful information for the application of new and safer artificial sweeteners. Fluorescence quenching assays indicated that the formation of complexes between sweeteners and BSA mainly induced the fluorescence quenching of protein and the binding site number were about 1 indicting that there is one mainly binding site of APM, AK, TGS, SC, or REB-A in domain of BSA with relatively weak interactions. Molecular modeling results indicated that hydrogen bonding interactions were the mainly binding forces of sweeteners with BSA. Circular dichroism spectra indicated that APM and REB-A obviously induced the secondary structure changes of BSA. The presence of APM increased the fraction of α-Helix of BSA from 65.4% to 73.8%, while the presence of REB-A resulted in decreasing the fraction of α-helix of BSA from 65.4% to 51.2%. The melting temperature studies showed that these five sweeteners except REB-A act as stabilizers to increase the thermal stability of BSA during the thermal denaturation process. In addition, AK, TGS, and SC obviously increased the esterase-like activity of BSA, and such loss of activity of BSA induced by APM and REB-A.

Identification of differences in the formation of plasma glycated proteins between dogs and humans under diabetes-like glucose concentration conditions

Dogs have been proposed as a translational model and used for studying aging, diabetes, and diabetes-related complications in humans. However, no studies have ever compared the glycation of plasma proteins between dogs and humans under similar experimental conditions. Thus, the aim of this study was to fill this gap by comparing the plasma protein glycation patterns of dogs and humans in an ex-vivo system. Canine and human plasma samples were incubated with glucose at concentrations comparable to those observed in diabetic patients. The final glucose plasma concentration resulted in similar glucose:albumin ratios in both species. Glycated proteins were evaluated by measuring the content of fructosamine, protein carbonyls, and the formation of advanced glycation end-products (AGEs). The concentrations of fructosamine and protein carbonyls in canine and human plasma increased in a glucose concentration-dependent manner (P < 0.0001). Of note, the relative increment of fructosamine and protein carbonyl content and AGE formation was always higher in human than in dog plasma. Our results reveal that the plasma glycation processes in dogs and humans are not similar. These novel findings could contribute to improve our understating about canine and human diabetes as well as other condition associated in the glycation of proteins.

Spectroscopic and molecular modelling studies on glycation modified bovine serum albumin with cyanidin-3-O-glucoside

In this study, we report the glycation mediated effect of bovine serum albumin (BSA) on the molecular interaction mechanism of cyanidin-3-O-glucoside (C3G) by molecular modelling, Uv-visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy, and circular dichroism spectroscopy studies. The structures of advanced glycation end-products (AGEs) modified BSA were modelled, energy minimized and analyzed for binding affinity by molecular docking studies using Autodock Vina. Glycation experiments are carried out using glucose and methylglyoxal to validate the molecular modelling results on the interaction of modified BSA with C3G. The modified structures were characterized by reduction in the binding pocket volume, surface, depth, hydrophobicity, and hydrogen bond donors/acceptors. Arg-194, Arg-196, Arg-198, Arg-217, Arg-409, Lys-114, Lys-116, Lys-204, Lys 221, and Lys-439 were found to be crucial in the context of glycation of BSA. TEM images represented the formation of unique globular aggregates in the event of glycation. Uv-visible spectroscopic studies showed the formation of new chromophores between 300 and 400 nm in the event of glycation. Fluorescence quenching was observed in a differential manner in the presence of C3G on glycation modified BSA. Circular dichroism studies suggested the loss of helical structure and formation of β-sheeted structure upon glycation, but subsequent C3G binding has resulted in the increase towards helical structure. Our findings suggested that drug binding affinity has been certainly impaired due to glycation and subsequent AGE modification. Arg-p modification has more austere impact on the structure and would affect the binding properties. We conclude that C3G had differential modulation of binding properties on glycated BSA which can help to protect the stability and bioavailability that has been impaired due to glycation mediated structural changes.

Oxidative Alteration of Trp-214 and Lys-199 in Human Serum Albumin Increases Binding Affinity with Phenylbutazone: A Combined Experimental and Computational Investigation

Human serum albumin (HSA) is a target for reactive oxygen species (ROS), and alterations of its physiological functions caused by oxidation is a current issue. In this work, the amino-acid residues Trp-214 and Lys-199, which are located at site I of HSA, were experimentally and computationally oxidized, and the effect on the binding constant with phenylbutazone was measured. HSA was submitted to two mild oxidizing reagents, taurine monochloramine (Tau-NHCl) and taurine dibromamine (Tau-NBr₂). The oxidation of Trp-214 provoked spectroscopic alterations in the protein which were consistent with the formation of N'-formylkynurenine. It was found that the oxidation of HSA by Tau-NBr₂, but not by Tau-NHCl, provoked a significant increase in the association constant with phenylbutazone. The alterations of Trp-214 and Lys-199 were modeled and simulated by changing these residues using the putative oxidation products. Based on the Amber score function, the interaction energy was measured, and it showed that, while native HSA presented an interaction energy of -21.3 kJ/mol, HSA with Trp-214 altered to N'-formylkynurenine resulted in an energy of -28.4 kJ/mol, and HSA with Lys-199 altered to its carbonylated form resulted in an energy of -33.9 kJ/mol. In summary, these experimental and theoretical findings show that oxidative alterations of amino-acid residues at site I of HSA affect its binding efficacy.

Metal-catalyzed oxidation of human serum albumin does not alter the interactive binding to the two principal drug binding sites

It is well known that various physiological factors such as pH, endogenous substances or post-translational modifications can affect the conformational state of human serum albumin (HSA). In a previous study, we reported that both pH- and long chain fatty acid-induced conformational changes can alter the interactive binding of ligands to the two principal binding sites of HSA, namely, site I and site II. In the present study, the effect of metal-catalyzed oxidation (MCO) caused by ascorbate/oxygen/trace metals on HSA structure and the interactive binding between dansyl-L-asparagine (DNSA; a site I ligand) and ibuprofen (a site II ligand) at pH 6.5 was investigated. MCO was accompanied by a time-dependent increase in carbonyl content in HSA, suggesting that the HSA was being oxidized. In addition, The MCO of HSA was accompanied by a change in net charge to a more negative charge and a decrease in thermal stability. SDS-PAGE patterns and α-helical contents of the oxidized HSAs were similar to those of native HSA, indicating that the HSA had not been extensively structurally modified by MCO. MCO also caused a selective decrease in ibuprofen binding. In spite of the changes in the HSA structure and ligand that bind to site II, no change in the interactive binding between DNSA and ibuprofen was observed. These data indicated that amino acid residues in site II are preferentially oxidized by MCO, whereas the spatial relationship between sites I and II (e.g. the distance between sites), the flexibility or space of each binding site are not altered. The present findings provide insights into the structural characteristics of oxidized HSA, and drug binding and drug-drug interactions on oxidized HSA.

Cys34 Adductomes Differ between Patients with Chronic Lung or Heart Disease and Healthy Controls in Central London

Oxidative stress generates reactive species that modify proteins, deplete antioxidant defenses, and contribute to chronic obstructive pulmonary disease (COPD) and ischemic heart disease (IHD). To determine whether protein modifications differ between COPD or IHD patients and healthy subjects, we performed untargeted analysis of adducts at the Cys34 locus of human serum albumin (HSA). Biospecimens were obtained from nonsmoking participants from London, U.K., including healthy subjects (n = 20) and patients with COPD (n = 20) or IHD (n = 10). Serum samples were digested with trypsin and analyzed by liquid chromatography-high resolution mass spectrometry. Effects of air pollution on adduct levels were also investigated based on estimated residential exposures to PM_2.5, O₃ and NO₂. For the 39 adducts with sufficient data, levels were essentially identical in blood samples collected from the same subjects on two consecutive days, consistent with the 28 day residence time of HSA. Multivariate linear regression revealed 21 significant associations, mainly with the underlying diseases but also with air-pollution exposures (p-value < 0.05). Interestingly, most of the associations indicated that adduct levels decreased with the presence of disease or increased pollutant concentrations. Negative associations of COPD and IHD with the Cys34 disulfide of glutathione and two Cys34 sulfoxidations, were consistent with previous results from smoking and nonsmoking volunteers and nonsmoking women exposed to indoor combustion of coal and wood.

In Vitro Investigation of the Interaction of Tolbutamide and Losartan with Human Serum Albumin in Hyperglycemia States

Serum albumin is exposed to numerous structural modifications which affect its stability and activity. Glycation is one of the processes leading to the loss of the original properties of the albumin and physiological function disorder. In terms of long lasting states of the hyperglycemia, Advanced Glycation End-products (AGEs) are formed. AGEs are responsible for cellular and tissue structure damage that cause the appearance of a number of health consequences and premature aging. The aim of the present study was to analyze the conformational changes of serum albumin by glycation—“fructation”—using multiple spectroscopic techniques, such as absorption (UV-Vis), fluorescence (SFM), circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy and evaluate of possible alteration of binding and competition between tolbutamide (TB, a first-generation sulfonylurea oral hypoglycemic drug) and losartan (LOS, an angiotensin II receptor (AT₁) blocker used in hypertension (1st line with a coexisting diabetes)) in binding to non-glycated (HSA) and glycated (gHSA_FRC) human serum albumin in high-affinity binding sites. The studies allowed us to indicate the structural alterations of human serum albumin as a result of fructose glycation. Changes in binding parameters, such as association (Ka) or Stern-Volmer (KSV) constants suggest that glycation increases the affinity of TB and LOS towards albumin and affects interactions between them. The process of albumin glycation influences the pharmacokinetics of drugs, thus monitored pharmacotherapy is reasonable in the case of diabetes and hypertension polypharmacy. This information may lead to the development of more effective drug treatments based on personalized medicine for patients with diabetes. Our studies suggest the validity of monitored polypharmacy of diabetes and coexisting diseases.