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

Effects of co-administration of lamotrigine on valproate transfer across the placenta and its brain entry in developing Genetic Absence Epilepsy Rats from Strasbourg (GAERS)

During development, embryos and foetuses may be exposed to maternally ingested antiseizure medications (ASM), valproate and lamotrigine, essential in some patients to control their epilepsy symptoms. Often, the two drugs are co-administered to reduce required doses of valproate, a known potential teratogen. This study used Genetic Absence Epilepsy Rat from Strasbourg to evaluate transfer of valproate and lamotrigine across late gestation placenta and their entry into cerebrospinal fluid (CSF) and brain of developing rats, in mono- and combination therapies. Animals at embryonic day (E) 19, postnatal day (P) 0, 4 and 21, and adults were administered valproate (30 mg/kg) or lamotrigine (6 mg/kg) with their respective [3H]-tracers, either alone or in combination. In chronic experiments, females consumed valproate-containing diet from 2 weeks prior to mating until offspring were used at E19 and P0. Drugs were injected 30 min before blood, CSF and brain samples were collected from terminally anaesthetised animals. Radioactivity in samples was measured. In acute monotherapy brain entry of valproate was higher in foetal than postnatal animals, correlating with its plasma protein binding. Brain entry of lamotrigine was not age-dependent. Combination therapy enhanced entry of lamotrigine into the adult brain but had no effects on brain and CSF entry of valproate. Following chronic valproate exposure, placental transfer of valproate decreased in combination therapy; however, foetal brain entry increased. Results suggest that during pregnancy, the use of combination therapy of valproate and lamotrigine may mitigate overall foetal exposure to valproate but potential risks to foetal brain development are less clear.

Contribution of the α1-Acid Glycoprotein in Drug Pharmacokinetics: The Usefulness of α1-Acid Glycoprotein-Knockout Mice

α1-Acid glycoprotein (AGP) is a primary binding protein for many basic drugs in plasma. The number of drugs that bind to AGP, such as molecular target anticancer drugs, has been continuously increasing. Since the plasma level of AGP fluctuates under various pathological conditions such as inflammation, it is important to evaluate the contribution of AGP to drug pharmacokinetics. Here, we generated conventional AGP-knockout (AGP-KO) mice and used them to evaluate the contribution of AGP. The pharmacokinetics of drugs that bind to two AGP variants (F1*S or A variants) or albumin were evaluated. Imatinib (a F1*S-binding drug) and disopyramide (an A-binding drug) or ibuprofen (an albumin-binding drug) were administered to wild-type (WT) and AGP-KO. The plasma level of imatinib and disopyramide decreased rapidly in AGP-KO as compared to WT. In AGP-KO, AUC and t1/2 were decreased, then CLtot was increased. Compared with disopyramide, imatinib pharmacokinetics showed more marked changes in AGP-KO as compared to WT. The results seemed to be due to the difference in plasma level of each AGP variant (F1*S:A = 2-3:1). No differences were observed in ibuprofen pharmacokinetics between the WT and AGP-KO mice. In vitro experiments using plasma from WT and AGP-KO showed that unbound fractions of imatinib and disopyramide were higher in AGP-KO. These results suggest that the rapid elimination of imatinib and disopyramide in AGP-KO could be due to decreased protein binding to AGP. Taken together, the AGP-KO mouse could be a potential animal model for evaluating the contribution of AGP to the pharmacokinetics of various drugs.

Selection of a suitable animal model to evaluate secretion of drugs in the human milk: a systematic approach

Lack of data on drug secretion in human milk is a concern for safe use of drugs during postpartum.Clinical studies are often difficult to perform; despite substantial improvements in computational methodologies such as physiologically based pharmacokinetic modelling, there is limited clinical data to validate such models for many drugs.Various factors that are likely to impact milk to plasma ratio were identified. A literature search was performed to gather available data on milk composition, total volume of milk produced per day, milk pH, haematocrit, and renal blood flow and glomerular filtration rate in various animal models.BLAST nucleotide and protein tools were used to evaluate the similarities between humans and animals in the expression and predominance of selected drug transporters, metabolic enzymes, and blood proteins.A multistep analysis of all the potential variables affecting drug secretion was considered to identify most appropriate animal model. The practicality of using the animal in a lab setting was also considered.Donkeys and goats were identified as the most suitable animals for studying drug secretion in milk and future studies should be performed in goats and donkeys to validate the preliminary observations.

Utility of life stage-specific chemical risk assessments based on New Approach Methodologies (NAMs)

The safety assessments for chemicals targeted for use or expected to be exposed to specific life stages, including infancy, childhood, pregnancy and lactation, and geriatrics, need to account for extrapolation of data from healthy adults to these populations to assess their human health risk. However, often adequate and relevant toxicity or pharmacokinetic (PK) data of chemicals in specific life stages are not available. For such chemicals, New Approach Methodologies (NAMs), such as physiologically based pharmacokinetic (PBPK) modeling, biologically based dose response (BBDR) modeling, in vitro to in vivo extrapolation (IVIVE), etc. can be used to understand the variability of exposure and effects of chemicals in specific life stages and assess their associated risk. A life stage specific PBPK model incorporates the physiological and biochemical changes associated with each life stage and simulates their impact on the absorption, distribution, metabolism, and elimination (ADME) of these chemicals. In our review, we summarize the parameterization of life stage models based on New Approach Methodologies (NAMs) and discuss case studies that highlight the utility of a life stage based PBPK modeling for risk assessment. In addition, we discuss the utility of artificial intelligence (AI)/machine learning (ML) and other computational models, such as those based on in vitro data, as tools for estimation of relevant physiological or physicochemical parameters and selection of model. We also discuss existing gaps in the available toxicological datasets and current challenges that need to be overcome to expand the utility of NAMs for life stage-specific chemical risk assessment.

Facing the Facts of Altered Plasma Protein Binding: Do Current Models Correctly Predict Changes in Fraction Unbound in Special Populations?

Accounting for variability in plasma protein binding of drugs is an essential input to physiologically-based pharmacokinetic (PBPK) models of special populations. Prediction of fraction unbound in plasma (fu) in such populations typically considers changes in plasma protein concentration while assuming that the binding affinity remains unchanged. A good correlation between predicted vs observed fu data reported for various drugs in a given special population is often used as a justification for such predictive methods. However, none of these analyses evaluated the prediction of the fold-change in fu in special populations relative to the reference population. This would be a more appropriate assessment of the predictivity, analogous to drug-drug interactions. In this study, predictive performance of the single protein binding model was assessed by predicting fu for alpha-1-acid glycoprotein and albumin bound drugs in hepatic impairment, renal impairment, paediatric, elderly, patients with inflammatory disease, and in different ethnic groups for a dataset of >200 drugs. For albumin models, the concordance correlation coefficients for predicted fu were >0.90 for 16 out of 17 populations with sub-groups, indicating strong agreement between predicted and observed values. In contrast, concordance correlation coefficients for predicted fold-change in fu for the same dataset were <0.38 for all populations and sub-groups. Trends were similar for alpha-1-acid glycoprotein models. Accordingly, the predictions of fu solely based on changes in protein concentrations in plasma cannot explain the observed values in some special populations. We recommend further consideration of the impact of changes in special populations to endogenous substances that competitively bind to plasma proteins, and changes in albumin structure due to posttranslational modifications. PBPK models of special populations for highly bound drugs should preferably use measured fu data to ensure reliable prediction of drug exposure or compare predicted unbound drug exposure between populations knowing that these will not be sensitive to changes in fu.

Genetic mutation and immune infiltration in embryonal tumor with multilayered rosettes

PURPOSE

Genetic mutations stand as pivotal factors leading to the occurrence of embryonal tumor with multilayered rosettes (ETMR). This study aims to identify improved treatment approaches by unraveling the genetic drivers and immune infiltration in ETMR.

METHODS

Two siblings with ETMR, treated at the General Hospital of Ningxia Medical University, were enrolled. Diagnosis involved MRI, Hematoxylin and Eosin (HE), and immunohistochemical (IHC) staining. Differentially expressed genes (DEGs) in ETMR were identified using GSE122077 and GSE14296 datasets. GO and KEGG analyses were used to determine ETMR-related pathways. Whole exome sequencing (WES) was utilized to annotate genetic variations in ETMR. Core genes, identified by protein-protein interaction (PPI), formed a diagnostic model evaluated by Logistic Regression. Single-sample Gene Set Enrichment Analysis (ssGSEA) assessed immune infiltration in ETMR, examining correlations between immune cells and core genes.

RESULTS

Two siblings were diagnosed with ETMR. In ETMR, 135 DEGs were identified, of which 25 genes were annotated with 28 mutation sites. Moreover, ETMR-related pathways included cell cycle, synaptic functions, and neurodegeneration. Three ETMR-related core genes (ALB, PSMD1, and PAK2) were screened by protein-protein interaction (PPI). The diagnostic model constructed using these genes demonstrated an AUC value of 0.901 (95% CI: 0.811-0.991) in the training set, indicating accurate predictions in ETMR. Enhanced ssGSEA scores for 16 immune cells in ETMR tissues suggested a strong immune response.

CONCLUSION

This study identifies diagnostic models associated with three core variant genes (ALB, PSMD1, PAK2) and enhanced immune cell activity in ETMR. It reveals crucial genetic features and significant immune responses in ETMR.

First-in-Human Predictions of Hepatic Clearance for Drugs With the Well-Stirred Model: Comparative Assessment Between Models of Fraction Unbound Based Either on the Free Drug Hypothesis, Albumin-Facilitated Hepatic Uptake or Dynamic Binding Kinetics

The well-stirred model (WSM) is commonly used to predict the hepatic clearance in vivo (CLH) of drugs. The necessary intrinsic clearance of the unbound drug (CLint-in vitro-unbound) is generated in the in vitro assays in the presence of microsomes or hepatocytes but in the absence of plasma proteins. The value of CLint-in vitro-unbound can be extrapolated with the fraction unbound determined in vitro in plasma (fup) only if the fraction unbound in vivo in liver is the same. However, this approach resulted to a systematic underprediction bias of CLH. With the goal of reducing this bias, two new models of fraction unbound were published in this journal. These models estimate the binding kinetics of the rates of association and dissociation of the drug-protein complex and propose that more dissociation in the liver compared to plasma will increase the fraction unbound available for the metabolism. Consequently, these two models generated higher values of fraction unbound, implying a lower underprediction bias of CLH with the WSM. The first model was developed by Poulin et al. and is referring to the value of fup that is adjusted (fu-adjusted) to quantify the effect of a full dissociation of the drug-protein complex at the hepatocyte membrane in accordance with the theory of the albumin-facilitated hepatic uptake. A second model was developed by Yan et al. who presented a dynamic fraction unbound (fu-dynamic) measuring the real dissociation kinetics of the drug-protein complex with a new in vitro assay in the presence and absence of a recombinant liver enzyme in plasma. Therefore, the objective of this study was to make the first comparative assessment between these two models. The results indicate that, in general, the WSM combined with the values of fu-adjusted was the most accurate approach for predicting CLH. The WSM combined with the values of fu-dynamic has underperformed particularly with the acidic and neutral drugs binding to the albumin and presenting a low metabolic turnover in vitro. Therefore, the new in vitro assay for fu-dynamic gave an underprediction bias of CLH for these drug properties. However, the values of fu-adjusted are significantly higher than those values of fu-dynamic, and, this resulted to no underprediction bias, which is reinforcing the theory of the ALB-facilitated hepatic uptake. For the other neutral and acidic drugs, the models of fu-dynamic and fu-adjusted are in closer agreement. Finally, for the basic drugs, the models of fu-adjusted and fu-dynamic as well as a third model only considering a pH gradient effect on fup are almost accurately equivalent.

Protopine and Allocryptopine Interactions with Plasma Proteins

A comprehensive study of the interactions of human serum albumin (HSA) and α-1-acid glycoprotein (AAG) with two isoquinoline alkaloids, i.e., allocryptopine (ACP) and protopine (PP), was performed. The UV-Vis spectroscopy, molecular docking, competitive binding assays, and circular dichroism (CD) spectroscopy were used for the investigations. The results showed that ACP and PP form spontaneous and stable complexes with HSA and AAG, with ACP displaying a stronger affinity towards both proteins. Molecular docking studies revealed the preferential binding of ACP and PP to specific sites within HSA, with site 2 (IIIA) being identified as the favored location for both alkaloids. This was supported by competitive binding assays using markers specific to HSA's drug binding sites. Similarly, for AAG, a decrease in fluorescence intensity upon addition of the alkaloids to AAG/quinaldine red (QR) complexes indicated the replacement of the marker by the alkaloids, with ACP showing a greater extent of replacement than PP. CD spectroscopy showed that the proteins' structures remained largely unchanged, suggesting that the formation of complexes did not significantly perturb the overall spatial configuration of these macromolecules. These findings are crucial for advancing the knowledge on the natural product-protein interactions and the future design of isoquinoline alkaloid-based therapeutics.

Serum Plasminogen Activator Inhibitor-1, α 1-Acid Glycoprotein, C-Reactive Protein, and Platelet Factor 4 Levels-Promising Molecules That Can Complete the "Puzzle" of the Biochemical Milieu in Severe Burns: Preliminary Results of a Cohort Prospective Study

Background: Burns represent a serious health problem, associated with multiple-organ failure, prolonged hospitalization, septic complications, and increased rate of mortality. The main aim of our study was to evaluate the levels of various circulating molecules in children with severe burns (more than 25% TBSA), in three different moments: 48 h, day 10, and day 21 post-burn. Materials and Methods: This study included 32 children with burns produced by flame, hot liquid, and electric arc and 21 controls. Serum plasminogen activator inhibitor-1 (PAI-1), α 1-acid glycoprotein (AGP), C-reactive protein (CRP), and platelet factor 4 (PF4) were detected using the Multiplex technique. Several parameters, such as fibrinogen, leucocyte count, thrombocyte count, triiodothyronine, thyroxine, and thyroid-stimulating hormone were also determined for each patient during hospitalization. Results: Significant statistical differences were obtained for CRP, AGP, and PF4 compared to the control group, in different moments of measurements. Negative correlations between CRP, AGP, and PF4 serum levels and burned body surface, and also the hospitalization period, were observed. Discussions: CRP levels increased in the first 10 days after burn trauma and then decreased after day 21. Serum PAI-1 levels were higher immediately after the burn and started decreasing only after day 10 post-burn. AGP had elevated levels 48 h after the burn, then decreased at 7-10 days afterwards, and once again increased levels after 21 days. PF4 serum levels increased after day 10 since the burning event. Conclusions: Serum CRP, AGP, PAI-1, and PF4 seem to be promising molecules in monitoring patients with a burn within the first 21 days.

Implication of serum and salivary albumin tests in the recent oral health related epidemiological studies: A narrative review

Albumin is the most abundant protein in human serum and a specific amount of albumin also can be found in the saliva. It has several physiological functions such as blood colloidal osmotic pressure, antioxidant activity, binding and transporting of endogenous and exogenous substrates. We conducted an electronic search across several databases such as PubMed, Scopus, Cochrane, Embase and Science Direct using the relevant MeSH terms and keywords like "albumin", "serum albumin", "salivary albumin", "oral health" "dental caries" and "epidemiology". Only the epidemiological studies published between 2010 and 2023 were included. After the application of the inclusion criteria, a total of 51 studied were included in this narrative review. Serum and salivary albumin tests have been used in various aspects of oral health as a diagnostic and prognostic factor. Some of the results point out to a pattern of association while some of them are inconclusive and even contradictory. This narrative review discusses the role, significance and impact of albumin in epidemiological oral health related studies including the categories of periodontal health and disease, dental caries, oral function and hypofunction, nutrition and malnutrition, tooth loss and its treatment, diabetes and cancer. In addition, it offers a short manual for the researchers on when, where and how to use albumin tests in planning their study designs whether investigating an association or measure them as a covariate.

Generation of affinity maps for thiazolidinediones with human serum albumin using affinity microcolumns. I. Studies of effects by glycation on multisite drug binding

Human serum albumin (HSA) is known to undergo modifications by glucose during diabetes. This process produces glycated HSA that can have altered binding to some drugs. In this study, high-performance affinity microcolumns and competition studies were used to see how glycation affects the binding by two thiazolidinedione-class drugs (i.e., pioglitazone and rosiglitazone) at specific regions of HSA. These regions included Sudlow sites I and II, the tamoxifen and digitoxin sites, and a drug-binding site located in subdomain IB. At Sudlow site II, the association equilibrium constants (or binding constants) for pioglitazone and rosiglitazone with normal HSA were 1.7 × 105 M-1 and 2.0 × 105 M-1 at pH 7.4 and 37 °C, with values that changed by up to 5.7-fold for glycated HSA. Sudlow site I of normal HSA had binding constants for pioglitazone and rosiglitazone of 3.4 × 105 M-1 and 4.6 × 105 M-1, with these values changing by up to 1.5-fold for glycated HSA. Rosiglitazone was found to also bind a second region that had a positive allosteric effect on Sudlow site I for all the tested preparations of HSA (binding affinity, 1.1-3.2 × 105 M-1; coupling constant for Sudlow site I, 1.20-1.34). Both drugs had a strong positive allosteric effect on the tamoxifen site of HSA (coupling constants, 13.7-19.9 for pioglitazone and 3.7-11.5 for rosiglitazone). Rosiglitazone also had weak interactions at a site in subdomain IB, with a binding constant of 1.4 × 103 M-1 for normal HSA and a value that was altered by up to 6.8-fold with glycated HSA. Neither of the tested drugs had any significant binding at the digitoxin site. The results were used to produce affinity maps that described binding by these thiazolidinediones with HSA and the effects of glycation on these interactions during diabetes.

Influence of Desialylation on the Drug Binding Affinity of Human Alpha-1-Acid Glycoprotein Assessed by Microscale Thermophoresis

Human serum alpha-1-acid glycoprotein (AAG) is an acute-phase plasma protein involved in the binding and transport of many drugs, especially basic and lipophilic substances. The sialic acid groups that terminate the N-glycan chains of AAG have been reported to change in response to numerous health conditions and may have an impact on the binding of drugs to AAG. In this study, we quantified the binding between native and desialylated AAG and seven drugs from different pharmacotherapeutic groups (carvedilol, diltiazem, dipyridamole, imipramine, lidocaine, propranolol, vinblastine) using microscale thermophoresis (MST). This method was chosen due to its robustness and high sensitivity, allowing precise quantification of molecular interactions based on the thermophoretic movement of fluorescent molecules. Detailed glycan analysis of native and desialylated AAG showed over 98% reduction in sialic acid content for the enzymatically desialylated AAG. The MST results indicate that desialylation generally alters the binding affinity between AAG and drugs, leading to either an increase or decrease in Kd values, probably due to conformational changes of AAG caused by the different sialic acid content. This effect is also reflected in an increased denaturation temperature of desialylated AAG. Our findings indicate that desialylation impacts free drug concentrations differently, depending on the binding affinity of the drug with AAG relative to human serum albumin (HSA). For drugs such as dipyridamole, lidocaine, and carvedilol, which have a higher affinity for AAG, desialylation significantly changes free drug concentrations. In contrast, drugs such as propranolol, imipramine, and vinblastine, which have a strong albumin binding, show only minimal changes. It is noteworthy that the free drug concentration of dipyridamole is particularly sensitive to changes in AAG concentration and glycosylation, with a decrease of up to 15% being observed, underscoring the need for dosage adjustments in personalized medicine.

Deciphering the binding mechanism of gingerol molecules with plasma proteins: implications for drug delivery and therapeutic potential

Ginger is a highly valued herb, renowned globally for its rich content of phenolic compounds. It has been traditionally used to treat various health conditions such as cardiovascular diseases, digestive issues, migraines, Alzheimer's disease, tumor reduction and chronic inflammation. Despite its potential medicinal applications, the therapeutic effectiveness of ginger is hindered by its limited availability and low plasma concentration levels. In this study, we explored the interaction of ginger's primary phenolic compounds, specifically 6-gingerol (6 G), 8-gingerol (8 G) and 10-gingerol (10 G), with plasma proteins which are human serum albumin (HSA) and α-1-acid glycoprotein (AGP). These two plasma proteins significantly influence drug distribution and disposition as they are key binding sites for most drugs. Fluorescence emission spectra indicated strong binding of 6, 8 and 10 G with HSA, with binding constants of 2.03 ± 0.01 × 104 M-1, 4.20 ± 0.01 × 104 M-1 and 6.03 ± 0.01 × 106 M-1, respectively. However, the binding of gingerols with AGP was found to be negligible. Molecular displacement by site-specific probes and molecular docking analyses revealed that gingerols bind at the IIA domain, with stability provided by hydrogen bonds, van der Waals forces, conventional hydrogen bonds, carbon-hydrogen bonds, alkyl and Pi-alkyl interactions. Further, the partial unfolding of the protein was observed upon binding the gingerol compound with HSA. In addition, molecular dynamic simulations demonstrated that gingerols remained stable in the subdomain IIA over 100 ns. This stability, coupled with Molecular Mechanics Generalized Born Surface Area indicating free energies of -43.765, -57.504 and -66.69 kcal/mol for 6, 8 and 10 G, respectively, reinforces the robust binding potential of these compounds. Circular dichroism studies suggested that the interaction of gingerols leads to the minimal transformation of HSA secondary structure, with the pattern being 10 G > 8 G > 6 G, a finding further substantiated by root mean square deviation and root mean square fluctuation fluctuations. These results propose that HSA has a stronger affinity to gingerols than AGP, which could have significant implications on the therapeutic circulating levels of gingerols.Communicated by Ramaswamy H. Sarma.

In vitro biodistribution studies on clinically approved FGFR inhibitors ponatinib, nintedanib, erlotinib and the investigational inhibitor KP2692

Binding towards human serum albumin (HSA) and α1-acid glycoprotein (AGP) of three approved fibroblast growth factor receptor (FGFR) inhibitors ponatinib (PON), nintedanib (NIN) and erdafitinib (ERD), as well as the experimental drug KP2692 was studied by means of spectrofluorometric and UV-visible spectrophotometric methods. Additionally, proton dissociation processes, lipophilicity, and fluorescence properties of these four molecules were investigated in detail. The FGFR inhibitors were predominantly presented in their single protonated form (HL+) at pH 7.4 (at blood pH). At gastric pH (pH 1-2) the protonated forms (+1 - +3) are present, which provide relatively good aqueous solubility of the drugs. All of the four inhibitors are highly or extremely lipophilic at pH 7.4 (logD7.4 ≥ 2.7). At acidic pH 2.0 PON and ERD are rather lipophilic, NIN is amphiphilic, while KP2692 is highly hydrophilic. All four compounds bind to HSA and AGP. Moderate binding of PON, KP2692 and NIN was found towards albumin (logK' = 4.5-4.7), while their affinity for AGP was about one order of magnitude higher (logK' = 5.2-5.7). ERD shows a larger affinity for both proteins (logK'HSA ≈ 5.2, logK'AGP ≈ 7.0). The computed constants were used to model the distribution of the FGFR inhibitors in blood plasma under physiological and pathological (acute phase) conditions. The changing levels of the two proteins under pathological conditions compensate each other for PON and NIN, so that the free drug fractions do not change considerably. In the case of ERD the higher AGP levels distinctly reduce the free available fraction of the drug. Comparison with clinical pharmacokinetic data indicates that the here presented solution distribution studies can very well predict the conditions in cancer patients.

Optical Screening and Classification of Drug Binding to Proteins in Human Blood Serum

Protein-drug interactions in the human bloodstream are important factors in applications ranging from drug design, where protein binding influences efficacy and dose delivery, to biomedical diagnostics, where rapid, quantitative measurements could guide optimized treatment regimes. Current measurement approaches use multistep assays, which probe the protein-bound drug fraction indirectly and do not provide fundamental structural or dynamic information about the in vivo protein-drug interaction. We demonstrate that ultrafast 2D-IR spectroscopy can overcome these issues by providing a direct, label-free optical measurement of protein-drug binding in blood serum samples. Four commonly prescribed drugs, known to bind to human serum albumin (HSA), were added to pooled human serum at physiologically relevant concentrations. In each case, spectral changes to the amide I band of the serum sample were observed, consistent with binding to HSA, but were distinct for each of the four drugs. A machine-learning-based classification of the serum samples achieved a total cross-validation prediction accuracy of 92% when differentiating serum-only samples from those with a drug present. Identification on a per-drug basis achieved correct drug identification in 75% of cases. These unique spectroscopic signatures of the drug-protein interaction thus enable the detection and differentiation of drug containing samples and give structural insight into the binding process as well as quantitative information on protein-drug binding. Using currently available instrumentation, the 2D-IR data acquisition required just 1 min and 10 μL of serum per sample, and so these results pave the way to fast, specific, and quantitative measurements of protein-drug binding in vivo with potentially invaluable applications for the development of novel therapies and personalized medicine.

Changes in plasma alpha-1 acid glycoprotein following hemorrhagic trauma: Possible role in dose differences of ALM drug therapy in rat and pig resuscitation

INTRODUCTION

The binding of drugs to plasma proteins is an important consideration in drug development. We have reported that the dose of adenosine, lidocaine, and magnesium (ALM) fluid therapy for resuscitation from hemorrhagic shock is nearly 3-times higher for pigs than rats. Since lidocaine strongly binds to serum alpha-1-acid glycoprotein (AGP), the aim of the study was to investigate the effect of hemorrhagic shock on levels of AGP in rats and pigs.

MATERIALS AND METHODS

Healthy adult male Sprague-Dawley rats and female crossbred pigs (n = 33 each) underwent tail vein and peripheral ear vein blood sampling, respectively, to collect plasma for AGP measurements. Rats (n = 17) and pigs (n = 16) underwent surgical instrumentation and uncontrolled hemorrhage via liver resection, and were treated with 3% NaCl ± ALM IV bolus followed 60 min later by 4 h 0.9% NaCl ± ALM IV drip. Rats were monitored for 72 h with blood samples taken post-surgery, and at 5.25, 24, and 72 h. Pigs were monitored for 6 h with blood samples taken post-surgery, and at 60 min and 6 h. Plasma AGP was measured with rat- and pig-specific enzyme-linked immunosorbent assay kits.

RESULTS

Baseline AGP levels in rats were 3.91 μg/mL and significantly 83-fold lower than in pigs (325 μg/mL). Surgical instrumentation was associated with ~10-fold increases in AGP in rats and a 21% fall in pigs. AGP levels remained elevated in rats after hemorrhage and resuscitation (28-29 μg/mL). In contrast, no significant differences in plasma AGP were found in ALM- or Saline-treated pigs over the monitoring period.

CONCLUSIONS

We conclude that the trauma of surgery alone was associated with significant increases in AGP in rats, compared to a contrasting decrease in pigs. Higher levels of plasma AGP in pigs prior to hemorrhagic shock is consistent with the higher ALM doses required to resuscitate pigs compared with rats.

Determination of α1-acid glycoprotein (AGP) concentration by HPLC in patients following local infiltration analgesia for primary total hip arthroplasty and its relation to ropivacaine (total and unbound)

Introduction: This study was performed to determine the levels of α1-acid glycoprotein (AGP) in old-age patients undergoing total hip arthroplasty. AGP is considered an acute phase protein produced during the acute phase reaction in the body to various stimuli; their proper monitoring is thus important. Methods: In order to study how AGP concentrations in old age patients change in response to surgical stress (total hip arthroplasty), a high-performance liquid chromatography assay was performed to measure AGP levels. AGP was isolated from the plasma by adding perchloric acid and was analyzed using PLRP-S 4000°A column. The mobile phase consisted of 1 mL TFA/L of water (Solvent A pH 2) and 1 mL TFA/L of acetonitrile (Solvent B). The gradient used was as follows: 0 min 18% B and 82% A, 15 min 60% B and 40% A, and 17 min 60% B and 40% A followed by column re-equilibration for 7 min before the next injection. AGP peak was obtained between 8.8 and 8.9 min. The method was fully optimised according to established guidelines. Results: The data obtained were analyzed on ChromQuest software. AGP concentrations were determined in all samples, including baseline and samples taken at different timed intervals. The peak for AGP was obtained between 8.8 and 8.9 min for both standard AGP and patient plasma. The graphs indicate that AGP concentration in almost all patient samples increased considerably, especially after 4 h and 24 h-for example, initial concentration in patient 1 was 10.36 mg/100 mL but, after 24 h, increased to 23.50 mg/100 mL. There was thus almost a 13 mg/100 mL increase in 24 h, which is confirmed by AGP concentration increasing after various conditions, including surgery. The increased plasma protein binding was comparatively associated with the unchanged free fraction of the drug. Conclusion: This surgically induced increase in AGP concentration resulted in increased plasma protein binding of the drug (ropivacaine), which in turn kept the free portion of ropivacaine stable during the postoperative period.

Potential Clinically Relevant Effects of Sialylation on Human Serum AAG-Drug Interactions Assessed by Isothermal Titration Calorimetry: Insight into Pharmacoglycomics?

Human serum alpha-1 acid glycoprotein is an acute-phase plasma protein involved in the binding and transport of many drugs, especially basic and lipophilic substances. It has been reported that the sialic acid groups that terminate the N-glycan chains of alpha-1 acid glycoprotein change in response to certain health conditions and may have a major impact on drug binding to alpha-1 acid glycoprotein. The interaction between native or desialylated alpha-1 acid glycoprotein and four representative drugs-clindamycin, diltiazem, lidocaine, and warfarin-was quantitatively evaluated using isothermal titration calorimetry. The calorimetry assay used here is a convenient and widely used approach to directly measure the amount of heat released or absorbed during the association processes of biomolecules in solution and to quantitatively estimate the thermodynamics of the interaction. The results showed that the binding of drugs with alpha-1 acid glycoprotein were enthalpy-driven exothermic interactions, and the binding affinity was in the range of 10-5-10-6 M. Desialylated alpha-1 acid glycoprotein showed significantly different binding with diltiazem, lidocaine, and warfarin compared with native alpha-1 acid glycoprotein, whereas clindamycin showed no significant difference. Therefore, a different degree of sialylation may result in different binding affinities, and the clinical significance of changes in sialylation or glycosylation of alpha-1 acid glycoprotein in general should not be neglected.

Plasma Protein-Mediated Uptake and Contradictions to the Free Drug Hypothesis: A Critical Review

According to the free drug hypothesis (FDH), only free, unbound drug is available to interact with biological targets. This hypothesis is the fundamental principle that continues to explain the vast majority of all pharmacokinetic and pharmacodynamic processes. Under the FDH, the free drug concentration at the target site is considered the driver of pharmacodynamic activity and pharmacokinetic processes. However, deviations from the FDH are observed in hepatic uptake and clearance predictions, where observed unbound intrinsic hepatic clearance (CL_int,u) is larger than expected. Such deviations are commonly observed when plasma proteins are present and form the basis of the so-called plasma protein-mediated uptake effect (PMUE). This review will discuss the basis of plasma protein binding as it pertains to hepatic clearance based on the FDH, as well as several hypotheses that may explain the underlying mechanisms of PMUE. Notably, some, but not all, potential mechanisms remained aligned with the FDH. Finally, we will outline possible experimental strategies to elucidate PMUE mechanisms. Understanding the mechanisms of PMUE and its potential contribution to clearance underprediction is vital to improving the drug development process.

Physiologically Based Pharmacokinetic Model of Brain Delivery of Plasma Protein Bound Drugs

INTRODUCTION

A physiologically based pharmacokinetic (PBPK) model is developed that focuses on the kinetic parameters of drug association and dissociation with albumin, alpha-1 acid glycoprotein (AGP), and brain tissue proteins, as well as drug permeability at the blood-brain barrier, drug metabolism, and brain blood flow.

GOAL

The model evaluates the extent to which plasma protein-mediated uptake (PMU) of drugs by brain influences the concentration of free drug both within the brain capillary compartment in vivo and the brain compartment. The model also studies the effect of drug binding to brain tissue proteins on the concentration of free drug in brain.

METHODS

The steady state and non-steady state PBPK models are comprised of 11-12 variables, and 18-23 parameters, respectively. Two model drugs are analyzed: propranolol, which undergoes modest PMU from the AGP-bound pool, and imipramine, which undergoes a high degree of PMU from both the albumin-bound and AGP-bound pools in plasma.

RESULTS

The free propranolol concentration in brain is under-estimated 2- to fourfold by in vitro measurements of free plasma propranolol, and the free imipramine concentration in brain is under-estimated by 18- to 31-fold by in vitro measurements of free imipramine in plasma. The free drug concentration in brain in vivo is independent of drug binding to brain tissue proteins.

CONCLUSIONS

In vitro measurement of free drug concentration in plasma under-estimates the free drug in brain in vivo if PMU in vivo from either the albumin and/or the AGP pools in plasma takes place at the BBB surface.

Species differences in plasma protein binding of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease inhibitor nirmatrelvir

Plasma protein binding (PPB) studies on the SARS-CoV-2 main protease inhibitor nirmatrelvir revealed considerable species differences primarily in dog and rabbit, which prompted further investigations into the biochemical basis for these differences.The unbound fraction (f_u) of nirmatrelvir in dog and rabbit plasma was concentration (2-200 µM)-dependent (dog f_u,p 0.024-0.69, rabbit f_u,p 0.010-0.82). Concentration (0.1-100 µM)-dependent binding in serum albumin (SA) (f_u,SA 0.040-0.82) and alpha-1-acid glycoprotein (AAG) (f_u,AAG 0.050-0.64) was observed in dogs. Nirmatrelvir showed minimal binding to rabbit SA (1-100 µM: f_u,SA 0.70-0.79), while binding to rabbit AAG was concentration-dependent (0.1-100 µM: f_u,AAG 0.024-0.66). In contrast, nirmatrelvir (2 µM) revealed minimal binding (f_u,AAG 0.79-0.88) to AAG from rat and monkeys. Nirmatrelvir showed minimal-to-moderate binding to SA (1-100 µM; f_u,SA 0.70-1.0) and AAG (0.1-100 µM; f_u,AAG 0.48-0.58) from humans across tested concentrations.Nirmatrelvir molecular docking studies using published crystal structures and homology models of human and preclinical species SA and AAG were used to rationalise the species differences to plasma proteins. This suggested that species differences in PPB are primarily driven by molecular differences in albumin and AAG resulting in differences in binding affinity.

The Nasal Innate Immune Proteome After Saline Irrigation: A Pilot Study in Healthy Individuals

BACKGROUND

Previous research has shown diminished nasal immune function following nasal saline irrigation (NSI), returning to baseline at 6 hours. The aim of this study was to examine the immune nasal proteome before and after 14 days of nasal irrigation.

METHODS

Seventeen healthy volunteers received either isotonic (IsoSal) or low salt (LowNa) NSI. Nasal secretions were collected before and 30 min after NSI at baseline and again after 14 days. Specimens were analyzed using mass spectrometry to detect proteins of relevance to nasal immune function.

RESULTS

One thousand eight hundred and sixty-five proteins were identified with significant changes in 71 proteins, of which 23 were identified as part of the innate immune system. Baseline analysis demonstrated an increase of 9 innate proteins after NSI, most after IsoSal. After 14 days, a greater increase in innate peptides was present, with most now in the LowNa group. When NSI solutions were compared, a significant increase in 4 innate proteins, including a 211% in lysozyme, was detected in the LowNa group.

CONCLUSION

LowNa NSI demonstrates evidence of improving the innate immune secretions, especially lysozyme, in healthy volunteers.

Quantification of the Chemical Chaperone 4-Phenylbutyric Acid (4-PBA) in Cell Culture Media via LC-HRMS: Applications in Fields of Neurodegeneration and Cancer

In recent years, 4-phenylbutyric acid (4-PBA), an FDA-approved drug, has increasingly been used as a nonspecific chemical chaperone in vitro and in vitro, but its pharmacodynamics is still not clear. In this context, we developed and validated a Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) method to quantify 4-PBA in NeuroBasal-A and Dulbecco's Modified Eagle widely used cell culture media. Samples were injected on a Luna® 3 µm PFP(2) 100 Å (100 × 2.0 mm) column maintained at 40 °C. Water and methanol both with 0.1% formic acid served as mobile phases in a step gradient mode. The mass acquisition was performed by selected ion monitoring (SIM) in negative mode for a total run time of 10.5 min at a flow rate of 0.300 mL/min. The analogue 4-(4-Nitrophenyl)-Butyric Acid served as internal standard. Validation parameters were verified according to FDA and EMA guidelines. The quantification ranges from 0.38-24 µM. Inter and intraday RSDs (Relative Standard Deviations) were within 15%. The developed LC-HRMS method allowed the estimation of 4-PBA absorption and adsorption kinetics in vitro in two experimental systems: (i) 4-PBA improvement of protein synthesis in an Alzheimer's disease astrocytic cell model; and (ii) 4-PBA reduction of endoplasmic reticulum stress in thapsigargin-treated melanoma cell lines.

Evaluation of In Vitro Distribution and Plasma Protein Binding of Selected Antiviral Drugs (Favipiravir, Molnupiravir and Imatinib) against SARS-CoV-2

There are a number of uncertainties regarding plasma protein binding and blood distribution of the active drugs favipiravir (FAVI), molnupiravir (MOLNU) and imatinib (IMA), which were recently proposed as therapeutics for the treatment of COVID-19 disease. Therefore, proton dissociation processes, solubility, lipophilicity, and serum protein binding of these three substances were investigated in detail. The drugs display various degrees of lipophilicity at gastric (pH 2.0) and blood pH (pH 7.4). The determined pK_a values explain well the changes in lipophilic character of the respective compounds. The serum protein binding was studied by membrane ultrafiltration, frontal analysis capillary electrophoresis, steady-state fluorometry, and fluorescence anisotropy techniques. The studies revealed that the ester bond in MOLNU is hydrolyzed by protein constituents of blood serum. Molnupiravir and its hydrolyzed form do not bind considerably to blood proteins. Likewise, FAVI does not bind to human serum albumin (HSA) and α1-acid glycoprotein (AGP) and shows relatively weak binding to the protein fraction of whole blood serum. Imatinib binds to AGP with high affinity (logK' = 5.8-6.0), while its binding to HSA is much weaker (logK' ≤ 4.0). The computed constants were used to model the distribution of IMA in blood plasma under physiological and 'acute-phase' conditions as well.

Characterization of binding properties of ephedrine derivatives to human alpha-1-acid glycoprotein

Most drugs, especially those with acidic or neutral moieties, are bound to the plasma protein albumin, whereas basic drugs are preferentially bound to human alpha-1-acid glycoprotein (AGP). The protein binding of the long-established drugs ephedrine and pseudoephedrine, which are used in the treatment of hypotension and colds, has so far only been studied with albumin. Since in a previous study a stereoselective binding of ephedrine and pseudoephedrine to serum but not to albumin was observed, the aim of this study was to check whether the enantioselective binding behavior of ephedrine and pseudoephedrine, in addition to the derivatives methylephedrine and norephedrine, is due to AGP and to investigate the influence of their different substituents and steric arrangement. Discontinuous ultrafiltration was used for the determination of protein binding. Characterization of ligand-protein interactions of the drugs was obtained by saturation transfer difference nuclear magnetic resonance spectroscopy. Docking experiments were performed to analyze possible ligand-protein interactions. The more basic the ephedrine derivative is, the higher is the affinity to AGP. There was no significant difference in the binding properties between the individual enantiomers and the diastereomers of ephedrine and pseudoephedrine.

Developmental changes in the extent of drug binding to rat plasma proteins

Binding of therapeutics to proteins in blood plasma is important in influencing their distribution as it is their free (unbound) form that is able to cross cellular membranes to enter tissues and exert their actions. The concentration and composition of plasma proteins vary during pregnancy and development, resulting in potential changes to drug protein binding. Here, we describe an ultrafiltration method to investigate the extent of protein binding of six drugs (digoxin, paracetamol, olanzapine, ivacaftor, valproate and lamotrigine) and two water soluble inert markers (sucrose and glycerol) to plasma proteins from pregnant and developing rats. Results showed that the free fraction of most drugs was lower in the non-pregnant adult plasma where protein concentration is the highest. However, plasma of equivalent protein concentration to younger pups obtained by diluting adult plasma did not always exhibit the same extent of drug binding, reinforcing the likelihood that both concentration and composition of proteins in plasma influence drug binding. Comparison between protein binding and brain drug accumulation in vivo revealed a correlation for some drugs, but not others. Results suggests that plasma protein concentration should be considered when using medications in pregnant and paediatric patients to minimise potential for fetal and neonatal drug exposure.

Interactions of fentanyl with blood platelets and plasma proteins: platelet sensitivity to prasugrel metabolite is not affected by fentanyl under in vitro conditions

BACKGROUND

Clinical trials indicate that fentanyl, like morphine, may impair intestinal absorption and thus decrease the efficacy of oral P2Y₁₂ inhibitors, such as clopidogrel, ticagrelor, and prasugrel. However, the ability of fentanyl to directly negate or reduce the inhibitory effect of P2Y₁₂ receptor antagonists on platelet function has not been established. A series of in vitro experiments was performed to investigate the ability of fentanyl to activate platelets, potentiate platelet response to ADP, and/or diminish platelet sensitivity to prasugrel metabolite (R-138727) in agonist-stimulated platelets. The selectivity and specificity of fentanyl toward major carrier proteins has been also studied.

METHODS

Blood was obtained from healthy volunteers (19 women and 12 men; mean age 40 ± 13 years). Platelet function was measured in whole blood, platelet-rich plasma and in suspensions of isolated platelets by flow cytometry, impedance and optical aggregometry. Surface plasmon resonance and molecular docking were employed to determine the binding kinetics of fentanyl to human albumin, α₁-acid glycoprotein, apolipoprotein A-1 and apolipoprotein B-100.

RESULTS

When applied at therapeutic and supratherapeutic concentrations under various experimental conditions, fentanyl had no potential to stimulate platelet activation and aggregation, or potentiate platelet response to ADP, nor did it affect platelet susceptibility to prasugrel metabolite in ADP-stimulated platelets. In addition, fentanyl was found to interact with all the examined carrier proteins with dissociation constants in the order of 10^-4 to 10^-9 M.

CONCLUSIONS

It does not seem that the delayed platelet responsiveness to oral P2Y₁₂ inhibitors, such as prasugrel, in patients undergoing percutaneous coronary intervention, results from direct interactions between fentanyl and blood platelets. Apolipoproteins, similarly to albumin and α₁-acid glycoprotein, appear to be important carriers of fentanyl in blood.

Spectroscopic Studies of Quinobenzothiazine Derivative in Terms of the In Vitro Interaction with Selected Human Plasma Proteins: Part 2

Synthesis of anticancer substances and studying their binding abilities towards human serum proteins as carriers are important parts of pharmaceutical and medical sciences development. The presented work is a continuation of studies of quinobenzothiazine derivatives binding with serum proteins. The main aim of this work was a spectroscopic analysis of second from benzothiazinium derivatives salt, 9-fluoro-5-alkyl-12(H)-quino [3,4-b][1,4]benzothiazinium chloride (Salt2), its interaction with carrier proteins, i.e., human serum albumin (HSA), α₁-acid glycoprotein (AGP), human gamma globulin (HGG), and the study of protein secondary and tertiary structure changes using spectroscopic techniques (spectrofluorescence, UV-Vis and circular dichroism CD spectroscopy). In order to mimic in vivo conditions, control normal serum (CNS) was used. Using the Klotz method, both binding constants (K_a [M^-1]) and the number of binding classes (n) were calculated. In addition, the percentage of displacement of binding site markers from HSA and AGP molecules has been defined. Based on the obtained data, it can be concluded that the main binding protein for Salt2 is AGP. HSA and HGG are also involved in the distribution of the studied substance in the bloodstream. Moreover, Salt2 very slightly interacts with CNS, which can cause strong therapeutic as well as toxic effects. The analysis of CD spectra confirms that there are no changes in the secondary structure of the main binding proteins in the presence of Salt2.

Generative models for age, race/ethnicity, and disease state dependence of physiological determinants of drug dosing

Dosing requires consideration of diverse patient-specific factors affecting drug pharmacokinetics and pharmacodynamics. The available pharmacometric methods have limited capacity for modeling the inter-relationships and patterns of variability among physiological determinants of drug dosing (PDODD). To investigate whether generative adversarial networks (GANs) can learn a generative model from real-world data that recapitulates PDODD distributions. A GAN architecture was developed for modeling a PDODD panel comprised of: age, sex, race/ethnicity, body weight, body surface area, total body fat, lean body weight, albumin concentration, glomerular filtration rate (EGFR), urine flow rate, urinary albumin-to-creatinine ratio, alanine aminotransferase to alkaline phosphatase R-value, total bilirubin, active hepatitis B infection status, active hepatitis C infection status, red blood cell, white blood cell, and platelet counts. The panel variables were derived from National Health and Nutrition Examination Survey (NHANES) data sets. The dependence of GAN-generated PDODD on age, race, and active hepatitis infections was assessed. The continuous PDODD biomarkers had diverse non-normal univariate distributions and bivariate trend patterns. The univariate distributions of PDODD biomarkers from GAN simulations satisfactorily approximated those in test data. The joint distribution of the continuous variables was visualized using three 2-dimensional projection methods; for all three methods, the points from the GAN simulation random variate vectors were well dispersed amongst the test data. The age dependence trend patterns in GAN data were similar to those in test data. The histograms for R-values and EGFR from GAN simulations overlapped extensively with test data histograms for the Hispanic, White, African American, and Other race/ethnicity groups. The GAN-simulated data also mirrored the R-values and EGFR changes in active hepatitis C and hepatitis B infection. GANs are a promising approach for simulating the age, race/ethnicity and disease state dependencies of PDODD.

Insights into the interaction of azinphos-methyl with bovine serum albumin: experimental and molecular docking studies

In the present study, combining spectroscopic and molecular modeling techniques has been used to analyze azinphos-methyl binding properties, as an organophosphorus pesticide, to bovine serum albumin. The quenching interaction of azinphos-methyl with bovine serum albumin was investigated in an appropriate physiological state (pH = 7.4). Fluorescence spectroscopy, UV-visible spectroscopy, circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). Findings showed differences in the secondary protein structure microenvironment following interaction with azinphos-methyl. The results from spectroscopic experiments suggest that azinphos-methyl binds to bovine serum albumin residues with a binding constant in the range of 0.099 × 10⁵-0.209 × 10⁵ M^-1 in one binding site (Tyr 160). The experimental results are supported by computational techniques such as docking using a bovine serum albumin crystal model. The results show that azinphos-methyl is linked to the site I of bovine serum albumin (in subdomain IB), and the result was in accordance with the experimental result. Based on the negative ΔG°, ΔH° and ΔS° values, the binding between azinphos-methyl and bovine serum albumin was spontaneous, and docking studies confirmed hydrogen bonding and van der Waals forces between them.Communicated by Ramaswamy H. Sarma.

Influence of Intrauterine Inflammation, Delivery, and Postnatal Feeding on the Temporal Changes of Serum Alpha 1 Acid Glycoprotein Levels in Extremely-Low-Birth-Weight Infants

Infection remains the primary cause of death in extremely-low-birth-weight infants (ELBWIs). Alpha 1 acid glycoprotein (α1AG), an acute-phase protein, has been shown to be elevated in sporadic cases of septic ELBWIs prior to abnormal clinical signs. To delineate the roles of inflammation, delivery, and feeding in postnatal α1AG changes in ELBWIs, 75 ELBWIs of 26.5 ± 2.2 weeks of gestation born between May 2011 and August 2017 were retrospectively studied. The dependence of α1AG levels obtained on days 0−5 on the clinical variables was examined by incorporating interactions with age, followed by estimations of regression coefficients between clinical variables and α1AG levels at the early and late postnatal ages, defined by their standard deviation. Chorioamnionitis (p < 0.001), funisitis (p = 0.045), vaginal delivery (p = 0.025), enteral feeding (p = 0.022), and probiotics (p = 0.005) were associated with early α1AG elevations. Hypertensive disorder of pregnancy (p < 0.001) and gestational age (p = 0.001) were associated with late α1AG elevation; premature rupture of membranes (p < 0.001), funisitis (p = 0.021), body weight z-scores (p < 0.001), and enteral feeding (p = 0.045) were associated with late α1AG reduction. Postnatal α1AG changes in ELBWIs were associated with variables representative of age, growth, delivery, inflammation, and enteral feeding, potentially reflecting the process of sensitization to extrinsic microbes in utero, at birth, and thereafter.

Analysis of drug interactions with serum proteins and related binding agents by affinity capillary electrophoresis: A review

Biomolecules such as serum proteins can interact with drugs in the body and influence their pharmaceutical effects. Specific and precise methods that analyze these interactions are critical for drug development or monitoring and for diagnostic purposes. Affinity capillary electrophoresis (ACE) is one technique that can be used to examine the binding between drugs and serum proteins, or other agents found in serum or blood. This article will review the basic principles of ACE, along with related affinity-based capillary electrophoresis (CE) methods, and examine recent developments that have occurred in this field as related to the characterization of drug-protein interactions. An overview will be given of the various formats that can be used in ACE and CE for such work, including the relative advantages or weaknesses of each approach. Various applications of ACE and affinity-based CE methods for the analysis of drug interactions with serum proteins and other binding agents will also be presented. Applications of ACE and related techniques that will be discussed include drug interaction studies with serum agents, chiral drug separations employing serum proteins, and the use of CE in hybrid methods to characterize drug binding with serum proteins.

The Role of Selected Serpins in Gastrointestinal (GI) Malignancies

Gastrointestinal (GI) cancers, which are a diverse group of malignant diseases, represent a major healthcare problem around the world. Due to the lack of specific symptoms in the early stages as well as insufficient diagnostic possibilities, these malignancies occupy the leading position in the causes of death worldwide. The currently available tests have too many limitations to be part of routine diagnostics. Therefore, new potential biomarkers that could be used as diagnostic and prognostic factors for these cancers are still being sought. Among the proteins that might fit this role are serpins, which are serine protease inhibitors. Although the serpins themselves have been known for many years, they have recently become the centre of attention for many authors, especially due to the fact that a number of proteins in this family are involved in many stages of neoplasia formation, from angiogenesis through tumour growth to progression. Therefore, the aim of this review is to present the current knowledge about the significance of serpins in GI malignancies, especially their involvement in the development and progression of oesophageal, gastric, pancreatic and colorectal cancers. This review summarises and confirms the important roles of selected serpins in the pathogenesis of various GI cancers and also points to their promising roles as therapeutic targets. However, due to the relatively nonspecific nature of serpins, future research should be carried out to elucidate the mechanisms involved in tumour pathogenesis in more detail.

Potential use of Cypridina luciferin for quantifying alpha 1-acid glycoprotein in human serum

Alpha 1-acid glycoprotein (AGP) is an acute phase protein in mammals, including humans. The amount of AGP in human serum varies in response to certain diseases; thus, many efforts have been made to develop methods for quantifying human AGP. We recently discovered that luminescence occurs merely by mixing Cypridina luciferin with human AGP under human serum-free neutral or basic buffer conditions. In this study, we tested an application of Cypridina luciferin for quantifying AGP contained in human serum. Our luminescence spectrum measurements of Cypridina luciferin with human serum samples showed that the maximum emission wavelength with human serum (480 nm) differed from that with human AGP (464 nm) due to the abundant presence of endogenous human serum albumin (HSA). Furthermore, the luminescence intensities of Cypridina luciferin with human AGP in HSA-depleted human serum were consistent with those in a human serum-free basic buffer, but those in human serum were not. These results indicated that depletion of HSA in human serum was required to use Cypridina luciferin for quantifying AGP in human serum. Additionally, we found that the luminescence intensity of Cypridina luciferin with bovine AGP was approximately tenfold lower than that with human AGP.

Unravelling Binding of Human Serum Albumin with Galantamine: Spectroscopic, Calorimetric, and Computational Approaches

Human serum albumin (HSA), an abundant plasma protein, binds to various ligands, acting as a transporter for numerous endogenous and exogenous substances. Galantamine (GAL), an alkaloid, treats cognitive decline in mild to moderate Alzheimer's disease and other memory impairments. A vital step in pharmacological profiling involves the interaction of plasma protein with the drugs, and this serves as an essential platform for pharmaceutical industry advancements. This study is carried out to understand the binding mechanism of GAL with HSA using computational and experimental approaches. Molecular docking revealed that GAL preferentially occupies Sudlow's site I, i.e., binds to subdomain IIIA. The results unveiled that GAL binding does not induce any conformational change in HSA and hence does not compromise the functionality of HSA. Molecular dynamics simulation (250 ns) deciphered the stability of the HSA-GAL complex. We performed the fluorescence binding and isothermal titration calorimetry (ITC) to analyze the actual binding of GAL with HSA. The results suggested that GAL binds to HSA with a significant binding affinity. ITC measurements also delineated thermodynamic parameters associated with the binding of GAL to HSA. Altogether, the present study deciphers the binding mechanism of GAL with HSA.

Albumin-Mediated Size Exclusion Chromatography: The Apparent Molecular Weight of PSMA Radioligands as Novel Parameter to Estimate Their Blood Clearance Kinetics

A meticulously adjusted pharmacokinetic profile and especially fine-tuned blood clearance kinetics are key characteristics of therapeutic radiopharmaceuticals. We, therefore, aimed to develop a method that allowed the estimation of blood clearance kinetics in vitro. For this purpose, ¹⁷⁷Lu-labeled PSMA radioligands were subjected to a SEC column with human serum albumin (HSA) dissolved in a mobile phase. The HSA-mediated retention time of each PSMA ligand generated by this novel 'albumin-mediated size exclusion chromatography' (AMSEC) was converted to a ligand-specific apparent molecular weight (MW_app), and a normalization accounting for unspecific interactions between individual radioligands and the SEC column matrix was applied. The resulting normalized MW_app,norm. could serve to estimate the blood clearance of renally excreted radioligands by means of their influence on the highly size-selective process of glomerular filtration (GF). Based on the correlation between MW and the glomerular sieving coefficients (GSCs) of a set of plasma proteins, GSC_calc values were calculated to assess the relative differences in the expected GF/blood clearance kinetics in vivo and to select lead candidates among the evaluated radioligands. Significant differences in the MW_app,norm. and GSC_calc values, even for stereoisomers, were found, indicating that AMSEC might be a valuable and high-resolution tool for the preclinical selection of therapeutic lead compounds for clinical translation.

Flavour compounds affect protein structure: The effect of methyl anthranilate on bovine serum albumin conformation

This study aims to understand possible effects of flavour compounds on the structure and conformation of endogenous proteins. Using methyl anthranilate (a grape flavour compound added to drinks, confectionery, and vape-liquids) and bovine serum albumin (BSA, a model serum protein) we designed experimental investigations using analytical ultracentrifugation, size exclusion chromatography small angle X-ray scattering, and fluorescence spectroscopy to reveal that methyl anthranilate spontaneously binds to BSA (ΔG°, ca. -21 KJ mol^-1) which induces a conformational compactness (ca. 10 %) in the monomer structure. Complementary molecular modelling and dynamics simulations suggested the binding occurs at Sudlow II of BSA via establishment of hydrogen bonds with arginine⁴⁰⁹, lysine⁴¹³ and serine⁴⁸⁸ leading to an increased conformational order in domains IA, IIB and IIIB. This work aims to set the foundation for future research on flavour-protein interactions and offer new sets of opportunities for understanding the effects of small compounds on protein structure.

Albumin as a Biomaterial and Therapeutic Agent in Regenerative Medicine

Albumin is a constitutional plasma protein, with well-known biological functions, e.g., a nutrient for stem cells in culture. However, albumin is underutilized as a biomaterial in regenerative medicine. This review summarizes the advanced therapeutic uses of albumin, focusing on novel compositions that take advantage of the excellent regenerative potential of this protein. Albumin coating can be used for enhancing the biocompatibility of various types of implants, such as bone grafts or sutures. Albumin is mainly known as an anti-attachment protein; however, using it on implantable surfaces is just the opposite: it enhances stem cell adhesion and proliferation. The anticoagulant, antimicrobial and anti-inflammatory properties of albumin allow fine-tuning of the biological reaction to implantable tissue-engineering constructs. Another potential use is combining albumin with natural or synthetic materials that results in novel composites suitable for cardiac, neural, hard and soft tissue engineering. Recent advances in materials have made it possible to electrospin the globular albumin protein, opening up new possibilities for albumin-based scaffolds for cell therapy. Several described technologies have already entered the clinical phase, making good use of the excellent biological, but also regulatory, manufacturing and clinical features of serum albumin.

Binding of temocillin to plasma proteins in vitro and in vivo: the importance of plasma protein levels in different populations and of co-medications

BACKGROUND

Temocillin plasma protein binding (PPB) in healthy individuals is reported to be ∼85% but had not been studied in patients.

OBJECTIVES

To obtain normative data on temocillin PPB in patients in relation to infection and impact of co-medications widely used in ICU.

METHODS

Plasma was obtained from healthy individuals (Group #1), non-ICU patients with UTI (Group #2), ICU patients with suspected/confirmed ventriculitis (Group #3) or with sepsis/septic shock (Group #4). Total and unbound temocillin concentrations were measured in spiked samples from temocillin-naive donors (in vitro) or in plasma from temocillin-treated subjects (in vivo). The impact of diluting plasma, using pharmaceutical albumin, or adding drugs potentially competing for PPB was tested in spiked samples. Data were analysed using a modified Hill-Langmuir equation taking ligand depletion into account.

RESULTS

Temocillin PPB was saturable in all groups, both in vitro and in vivo. Maximal binding capacity (Bmax) was 1.2-2-fold lower in patients. At 20 and 200 mg/L (total concentrations), the unbound fraction reached 12%-29%, 23%-42% and 32%-52% in Groups #2, #3, #4. The unbound fraction was inversely correlated with albumin and C-reactive protein concentrations. Binding to albumin was 2-3-fold lower than in plasma and non-saturable. Drugs with high PPB but active at lower molar concentrations than temocillin caused minimal displacement, while fluconazole (low PPB but similar plasma concentrations to temocillin) increased up to 2-fold its unbound fraction.

CONCLUSIONS

Temocillin PPB is saturable, 2-4-fold lowered in infected patients in relation to disease severity (ICU admission, hypoalbuminaemia, inflammation) and only partially reproducible with albumin. Competition with other drugs must be considered for therapeutic concentrations to be meaningful.

The effect of calcium-magnesium mixtures in sol-gel coatings on bone tissue regeneration

Calcium and magnesium are two elements essential for bone structure and metabolism. However, their synergistic or competitive effects on bone regeneration are often overlooked during biomaterial development. We examined the interactions between Ca and Mg in sol-gel coatings doped with mixtures of CaCl₂ (0.5%) and MgCl₂ (0.5, 1, and 1.5%). After physicochemical characterisation, the materials were incubated in vitro with MC3T3-E1 osteoblastic cells and RAW264.7 macrophages, and the protein adsorption was analysed using nLC-MS/MS. The incorporation of the ions did not lead to the formation of crystalline structures and did not affect the sol-gel network cross-linking. The release of the ions did not cause cytotoxic effects at any tested concentration. The proteomic analysis showed that adding the Ca and Mg ions elevated the adsorption of proteins associated with inflammatory response regulation (e.g., ALBU, CLUS, HPT, HPTR, A1AG1 and A1AG2) but decreased the adsorption of immunoglobulins. The CaMg coatings had reduced affinity to proteins associated with coagulation (e.g., FA9, FA10, FA11, FA12) but increased the adsorption of proteins involved in cell adhesion (DSG1, DESP, FBLN1, ZA2G). In vitro assays revealed that the cellular response was affected by changing the concentration of Mg. Moreover, our results show that these differences reflect the changes in the concentrations of both ions in the mix but are not a simple additive effect.

Human Apparent Volume of Distribution Predicts Bioaccumulation of Ionizable Organic Chemicals in Zebrafish Embryos

Chemicals with elevated bioaccumulation profiles present potential hazards to public health and the environment. Ionizable organic compounds (IOCs) increasingly represent a large proportion of commercial chemicals; however, historical approaches for bioaccumulation determinations are mainly developed for neutral chemicals, which were not appropriate for IOCs. Herein, we employed the zebrafish embryo, a common vertebrate model in environmental and biomedical studies, to elucidate toxicokinetics and bioconcentration of eight IOCs with diverse physicochemical properties and pharmacokinetic parameters. At an environmentally relevant pH (7.5), most IOCs exhibited rapid uptake and depuration in zebrafish, suggesting the ionized forms of IOCs are readily bioavailable. Bioconcentration factors (BCF) of these IOCs ranged from 0.0530 to 250 L·kg^-1 wet weight. The human pharmacokinetic proportionality factor, apparent volume of distribution (V_D), better predicted the BCF of selected IOCs than more commonly used hydrophobicity-based parameters (e.g., pH-dependent octanol-water distribution ratio, D_ow). Predictive bioaccumulation models for IOCs were constructed and validated using V_D alone or with D_ow. Significant relationships between fish BCF and human V_D, which is readily available for pharmaceuticals, highlighted the utility of biologically based "read-across" approaches for predicting bioaccumulative potential of IOCs. Our novel findings thus provided an understanding of the partitioning behavior and improved predictive bioconcentration modeling for IOCs.

Complexity and clinical significance of drug-drug interactions (DDIs) in oncology: challenging issues in the care of patients regarding cancer-associated thrombosis (CAT)

Cancer patients have an increased risk of developing venous thromboembolic events. Anticoagulation management includes prophylactic or therapeutic doses of low molecular weight heparins (LMWHs) or direct oral anticoagulants (DOACs). However, the management of thrombosis in patients with cancer is complex due to various individual and disease-related factors, including drug–drug interactions (DDIs). Furthermore, DDIs may impact both, cancer and venous thrombosis, treatment effectiveness and safety; their relevance is highlighted by the advances in cancer therapeutics. Given that these new oncology drugs are extensively used, more attention should be given to monitoring potential DDIs to minimize risks. Recognition of DDIs is of utmost importance in an era of rapid developments in cancer treatments and introduction of novel treatments and protocols. When managing cancer-associated thrombosis (CAT), the concomitant use of a DOAC and a moderate or strong modulator (inhibitor or inducer) of CYP3A4 or a P-glycoprotein (P-gp) is most likely to be associated with significant DDIs. Therefore, LMWHs remain the first-line option for the long-term management of CAT under these circumstances and physicians must consider utilizing LMWHs as first line. This review describes the risk of DDIs and their potential impact and outcomes in patients with cancer associated thrombosis (CAT) receiving anticoagulation.

Dialdehyde Starch Nanocrystals as a Novel Cross-Linker for Biomaterials Able to Interact with Human Serum Proteins

In recent years, new cross-linkers from renewable resources have been sought to replace toxic synthetic compounds of this type. One of the most popular synthetic cross-linking agents used for biomedical applications is glutaraldehyde. However, the unreacted cross-linker can be released from the materials and cause cytotoxic effects. In the present work, dialdehyde starch nanocrystals (NDASs) were obtained from this polysaccharide nanocrystal form as an alternative to commonly used cross-linking agents. Then, 5-15% NDASs were used for chemical cross-linking of native chitosan (CS), gelatin (Gel), and a mixture of these two biopolymers (CS-Gel) via Schiff base reaction. The obtained materials, forming thin films, were characterized by ATR-FTIR, SEM, and XRD analysis. Thermal and mechanical properties were determined by TGA analysis and tensile testing. Moreover, all cross-linked biopolymers were also characterized by hydrophilic character, swelling ability, and protein absorption. The toxicity of obtained materials was tested using the Microtox test. Dialdehyde starch nanocrystals appear as a beneficial plant-derived cross-linking agent that allows obtaining cross-linked biopolymer materials with properties desirable for biomedical applications.

The 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl Phthalimide Derivatives as Prodrugs—Spectroscopic and Theoretical Binding Studies with Plasma Proteins

Many publications in databases deal with the interactions of new drugs with albumin. However, it is not only albumin that is responsible for binding pharmaceutical molecules to proteins in the human body. There are many more proteins in plasma that are important for the study of the ADME pathway. Therefore, in this study, we have shown the results of the interactions between the plasma proteins albumin, orosomucoid, and gamma globulins and non-toxic anti-inflammatory phthalimide analogs, which due to the promising obtained results, may be potential candidates in the group of analgesic and anti-inflammatory drugs. Using spectroscopic methods and molecular modeling, we showed that all four tested compounds form complexes with the analyzed proteins. The formation of a complex with proteins raises the pharmacological efficacy of the drug. Therefore, the obtained results could be a step in the study of the pharmacokinetics and pharmacodynamics of new potential pharmaceuticals.

Prediction Models for Brain Distribution of Drugs Based on Biomimetic Chromatographic Data

The development of high-throughput approaches for the valid estimation of brain disposition is of great importance in the early drug screening of drug candidates. However, the complexity of brain tissue, which is protected by a unique vasculature formation called the blood−brain barrier (BBB), complicates the development of robust in silico models. In addition, most computational approaches focus only on brain permeability data without considering the crucial factors of plasma and tissue binding. In the present study, we combined experimental data obtained by HPLC using three biomimetic columns, i.e., immobilized artificial membranes, human serum albumin, and α1-acid glycoprotein, with molecular descriptors to model brain disposition of drugs. Kp,uu,brain, as the ratio between the unbound drug concentration in the brain interstitial fluid to the corresponding plasma concentration, brain permeability, the unbound fraction in the brain, and the brain unbound volume of distribution, was collected from literature. Given the complexity of the investigated biological processes, the extracted models displayed high statistical quality (R2 > 0.6), while in the case of the brain fraction unbound, the models showed excellent performance (R2 > 0.9). All models were thoroughly validated, and their applicability domain was estimated. Our approach highlighted the importance of phospholipid, as well as tissue and protein, binding in balance with BBB permeability in brain disposition and suggests biomimetic chromatography as a rapid and simple technique to construct models with experimental evidence for the early evaluation of CNS drug candidates.

Bioactive compounds: Application of albumin nanocarriers as delivery systems

Enriched products with bioactive compounds (BCs) show the capacity to produce a wide range of possible health effects. Most BCs are essentially hydrophobic and sensitive to environmental factors; so, encapsulation becomes a strategy to solve these problems. Many globular proteins have the intrinsic ability to bind, protect, encapsulate, and introduce BCs into nutraceutical or pharmaceutical matrices. Among them, albumins as human serum albumin (HSA), bovine serum albumin (BSA), ovalbumin (OVA) and α-lactalbumin (ALA) are widely abundant, available, and applied in many industrial sectors, becoming promissory materials to encapsulate BCs. Therefore, this review focuses on researches about the main groups of natural origin BCs (namely phenolic compounds, lipids, vitamins, and carotenoids), the different types of nanostructures based on albumins to encapsulate them and the main fields of application for BCs-loaded albumin systems. In this context, phenolic compounds (catechins, quercetin, and chrysin) are the most extensively BCs studied and encapsulated in albumin-based nanocarriers. Other extensively studied subgroups are stilbenes and curcuminoids. Regarding lipids and vitamins; terpenes, carotenoids (β-carotene), and xanthophylls (astaxanthin) are the most considered. The main application areas of BCs are related to their antitumor, anti-inflammatory, and antioxidant properties. Finally, BSA is the most used albumin to produced BCs-loaded nanocarriers.

Identification and Validation of New Interleukin-2 Ligands Using DNA-Encoded Libraries

Interleukin-2 (IL2) is a pro-inflammatory cytokine that plays a crucial role in immunity, which is increasingly being used for therapeutic applications. There is growing interest in developing IL2-based therapeutics which do not interact with the alpha subunit of the IL2 receptor (CD25) as this protein is primarily found on immunosuppressive regulatory T cells (T_regs). Screenings of a new DNA-encoded library, comprising 669,240 members, provided a novel series of IL2 ligands, subsequently optimized by medicinal chemistry. One of these molecules (compound 18) bound to IL2 with a dissociation constant of 0.34 μM was able to form a kinetically stable complex with IL2 in size-exclusion chromatography and recognized the CD25-binding site as evidenced by competition experiments with the NARA1 antibody. Compound 18 and other members of the series may represent the starting point for the discovery of potent small-molecule modulators of IL2 activity, abrogating the binding to CD25.