Protein Binding Characteristics Research Articles

Pharmacokinetic evaluation of oral deracoxib in geese (Anser anser domesticus).

The integration of pain management in veterinary practice, driven by heightened animal welfare concerns, extends to avian species where subtle and nonspecific behavioral signs pose challenges. Given that safety concerns with classical NSAIDs highlight the need for more targeted alternatives in birds, this study explores the pharmacokinetic (PK) properties of Deracoxib (DX), a COX-2 selective NSAID approved for use in dogs, following a single oral administration in geese. Six healthy female geese received 4 mg/kg DX. Blood was drawn from the left wing vein to heparinized tubes at 0, 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, and 24 h. Plasma DX concentrations were measured using HPLC coupled to an UV detector, and the data were pharmacokinetically analyzed using PKanalix™ software in a non-compartmental approach. The results indicated a terminal half-life of 6.3 h and a Tmax of 1 h, with no observed adverse effects. While refraining from claiming absolute safety based on a single dose, it is worth highlighting that further safety studies for DX in geese are warranted, suggesting a possibility for intermittent use. In addition, drawing conclusions on efficacy and suitability awaits further research, particularly in understanding COX-2 selectivity and protein binding characteristics specific to geese.

Introducing the Dynamic Well-Stirred Model for Predicting Hepatic Clearance and Extraction Ratio

The well-stirred model (WSM) incorporating the fraction of unbound drug (fu) to account for the effect of plasma binding on intrinsic clearance has been widely used for predicting hepatic clearance under the assumption that drug protein binding reaches equilibrium instantaneously. Our theoretical analysis reveals that the effect of protein binding on intrinsic clearance is better accounted for with the dynamic free fraction (fD), a measure of drug protein binding affinity, which leads to a putative dynamic well-stirred model (dWSM) without the instantaneous equilibrium assumption. Using recombinant CYP3A4 as the in vitro clearance system, we demonstrate that the binding effect of albumin on the intrinsic clearance of both highly bound midazolam and highly free verapamil is fully corrected by their corresponding fD values, respectively. On the other hand, fu only corrects the binding effect of albumin on the intrinsic clearance of verapamil, and yields severe over-correction of the intrinsic clearance of midazolam. The results suggest that the traditional WSM is suitable for highly free drugs like verapamil but not necessarily for highly bound drugs such as midazolam due to the violation of the instantaneous equilibrium assumption or under-estimating the true free drug concentration. In comparison, the dWSM incorporating fD holds true as long as drug elimination follows steady-state kinetics, and hence, it is more broadly applicable to drugs with different protein binding characteristics. Here we demonstrate with 36 diverse drugs, that the dWSM significantly improves the accuracy of predicting human hepatic clearance and liver extraction ratio from in vitro microsomal clearance data, highlighting the importance of drug plasma protein binding kinetics in addressing the under-prediction of hepatic clearance by the WSM.

Oxali-palladium nanoparticle synthesis, characterization, protein binding, and apoptosis induction in colorectal cancer cells

This paper focuses on the synthesis of nano-oxali-palladium coated with turmeric extract (PdNPs) using a green chemistry technique based on the reduction in the Pd (II) complex by phytochemicals inherent in turmeric extract. PdNPs were examined and characterized using Field Emission Scanning Electron Microscopy (FESEM), Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR), and Atomic Force Microscopy (AFM). Using different spectroscopic and molecular dynamics simulations, a protein-binding analysis of the produced nanoparticle was conducted by observing its interaction with human serum albumin (HSA). Lastly, the cytotoxic effects and apoptotic processes of PdNPs were studied against the HCT116 human colorectal cell line using the MTT assay and flow cytometry tests. According to the findings, PdNPs with spherical and homogenous morphology and a size smaller than 100 nm were generated. In addition, they can induce apoptosis in colorectal cancer cells in a dose-dependent manner with a lower Cc50 (78 µL) than cisplatin and free oxali-palladium against HCT116 cells. The thermodynamic characteristics of protein binding of nanoparticles with HSA demonstrated that PdNPs had a great capacity for quenching and interacting with HSA through hydrophobic forces. In addition, molecular dynamics simulations revealed that free oxali-palladium and PdNP attach to the same area of HSA via non-covalent interactions. It is conceivable to indicate that the synthesized PdNPs are a potential candidate for the construction of novel, nature-based anticancer treatments with fewer side effects and a high level of eco-friendliness.Graphical

Abstract A139: Preclinical characterization and prediction of human pharmacokinetics and efficacious dose for VIP236, a novel alpha V beta 3 binding small molecule-drug conjugate (SMDC)

Abstract VIP236 is a small molecule drug conjugate (SMDC) consisting of an alpha v beta 3 (αvβ3) integrin binder linked to an optimized camptothecin (optCPT) payload via a protease sensitive peptide sequence. The overall drug design strategy for VIP236 is targeted delivery to the tumor microenvironment (TME) with extracellular release of the opCPT by neutrophil elastase (NE) present in the TME. VIP236 is anticipated to kill tumor cells while reducing effects to normal tissue. VIP236 was characterized in preclinical pharmacokinetic (PK) and efficacy studies to predict its human PK and efficacious dose. Briefly, VIP236 was administered intravenously (IV) to mice, rats, and dogs to characterize both its in vivo PK (1-2 mg/kg) and its routes of excretion (bile-duct cannulated [BDC] rat at 10 mg/kg). VIP236 was evaluated in vitro for its protein binding characteristics and as a substrate of human drug transporters. In addition, VIP236 was dosed to MX-1 (breast cancer) xenografted mice at doses ranging from 26-40 mg/kg IV on a 3 days on/4 days off regimen to characterize its antitumor activity. VIP236 had low plasma clearance in mice, rats, and dogs (CL=2.7-4.4 mL/min/kg) and low volume of distribution (Vss = 0.11 to 0.25 L/kg). Terminal half-life ranged from 0.93 hour in mice to 3.07 hours in dogs. In BDC rats, VIP236 was primarily excreted in bile with biliary clearance accounting for essentially all the total body CL. There was minimal to no metabolites in rat bile and urine. In vitro VIP236 exhibited low permeability in MDCKII cell monolayers and was identified as a substrate of BSEP and MRP2. VIP236 was highly protein bound to plasma protein with fraction unbound being <5% in all species tested. VIP236 showed robust tumor regression in MX-1 xenografted mice at all doses tested. Allometric methods were used to predict a low human VIP236 CL (0.87-2.68 mL/min/kg) and Vss (0.10 L/kg). Translational pharmacokinetic/pharmacodynamic modeling was used to predict human efficacious doses and exposures by benchmarking VIP236 against irinotecan antitumor activity in MX-1 xenograft mice after 5 cycles of dosing. Based on this analysis, predicted human doses ranged from 1-5 mg/kg IV on a 2 days on/5 days off regimen. VIP236 is currently being evaluated in a first-in-human study in patients with advanced or metastatic solid tumors (NCT05712889). Citation Format: Harvey Wong, Beatrix Stelte-Ludwig, Hans-Georg Lerchen, Amy J Johnson, Melanie M Frigault, Raquel Izumi, Ahmed Hamdy. Preclinical characterization and prediction of human pharmacokinetics and efficacious dose for VIP236, a novel alpha V beta 3 binding small molecule-drug conjugate (SMDC) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A139.

Analysis of protein binding characteristics among Arabidopsis BBX protein family

Plants have evolved various mechanisms of adjusting their diurnal and seasonal growth and development in response to variations in day length and light quality. This plasticity is facilitated by intricate regulatory networks that comprise transcription factors, whose expression is modulated by the activity of photoreceptors. In Arabidopsis, B-box (BBX) transcription factors, which contain one or two Zn-ligating B-box motifs in their N-termini, serve as key mediators of light signaling for photomorphogenesis, shade avoidance, and photoperiodic flowering. While multiple BBX proteins may function as a single regulatory unit, the binding networks that form among members of the BBX family have not been extensively investigated. Here, we have demonstrated that the homodimerization of two B-box motifs containing CONSTANS protein (BBX1), which regulates light signaling and is the most extensively characterized among all BBX proteins, requires at least three B-box motifs. Therefore, the number of B-box motifs may significantly influence heterodimerization among BBX family members. An interactome analysis of all 32 known B-box family members revealed that the binding affinity between group III and V proteins with only one B-box motif is relatively weaker than that observed among other group members. In fact, the group V proteins BBX26 and BBX27 rarely interact with other BBX members. Taken together, the results of this study emphasize the importance of the B-box motif in network formation among BBX proteins and provide insights into investigating the various signaling pathways mediated by these networks.

Cannabinoids as Potential Cancer Therapeutics: The Concentration Conundrum.

Background: Studies have reported that cannabinoids, in particular Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD), significantly reduce cancer cell viability in vitro. Unfortunately, treatment conditions vary significantly across reports. In particular, a majority of reports utilize conditions with reduced serum concentrations (0-3%) that may compromise the growth of the cells themselves, as well as the observed results. Objectives: This study was designed to test the hypothesis that, based on their known protein binding characteristics, cannabinoids would be less effective in the presence of fetal bovine serum (FBS). Moreover, we wished to determine if the treatments served to be cytotoxic or cytostatic under these conditions. Methods: Six cancer cell lines, representing two independent lines of three different types of cancer (glioblastoma, melanoma, and colorectal cancer [CRC]), were treated with 10 μM pure Δ9-THC, CBD, KM-233, and HU-331 for 48 h (in the presence or absence of FBS). Cell viability was measured with the MTT assay. Dose-response curves were then generated comparing the potencies of the four cannabinoids under the same conditions. Results: We found that serum-free medium alone produces cell cycle arrest for CRC cells and slows cell growth for the other cancer types. The antineoplastic effects of three of the four cannabinoids (Δ9-THC, CBD, and KM-233) increase when serum is omitted from the media. In addition, dose-response curves for these drugs demonstrated lower IC50 values for serum-free media compared with the media with 10% serum in all cell lines. The fourth compound, HU-331, was equally effective under both conditions. A further confound we observed is that omission of serum produces dramatic binding of Δ9-THC and CBD to plastic. Conclusions: Treatment of cancer cells in the absence of FBS appears to enhance the potency of cannabinoids. However, omission of FBS itself compromises cell growth and represents a less physiological condition. Given the knowledge that cannabinoids are 90-95% protein bound and have well-known affinities for plastic, it may be ill-advised to treat cells under conditions where the cells are not growing optimally and where known concentrations cannot be assumed (i.e., FBS-free conditions).

Inhibition of SARS-CoV2 viral infection with natural antiviral plants constituents: An in-silico approach

Background and ObjectiveIn 2019, a novel coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) was declared pandemic. Advancement in computational technology has provided rapid and cost-effective techniques to test the efficacy of newer therapeutic agents. This study evaluated some of the potent phytochemicals obtained from AYUSH (Ayurveda, Yoga, Naturopathy, Unani, Siddha, Sowa-Rigpa, and Homeopathy)-listed medicinal plants against SARS-CoV-2 proteins using computational techniques. Materials and methodsThe potential SARS-CoV-2 protein targets were utilized to study the ligand–protein binding characteristics. The bioactive agents were obtained from ashwagandha, liquorice, amla, neem, tinospora, pepper, and stevia. Ivermectin was utilized as a reference agent to compare its efficacy with phytochemicals. ResultsThe computational analysis suggested that all the bioactive components from the selected plants possessed negative docking scores (ranging from −6.24 to −10.53). The phytoconstituents were well absorbed, distributed in the body except for the CNS, metabolized by liver enzymes, well cleared from the body, and well tolerated. The data suggest that AYUSH-recommended plants demonstrated therapeutic efficacy against SARS CoV-2 virus infection with significantly reduced toxicity. ConclusionThe phytoconstituents were found to hinder the early stages of infection, such as absorption and penetration, while ivermectin prevented the passage of genetic material from the cytoplasm to the nucleus. Additional research involving living tissues and clinical trials are suggested to corroborate the computational findings.

Curcumin and whey protein binding and structural characteristics of their complex evidenced by atomic force microscopy

Curcumin and whey protein binding and structural characteristics of their complex evidenced by atomic force microscopy

Abstract LB225: Toward comprehensive, single-molecule proteomics: Protein identification by short-epitope mapping

Abstract Protein Identification by Short-epitope Mapping (PrISM) is a novel proteomics method with the goal of comprehensive proteome quantification at single-molecule sensitivity. In this work, we present computational modeling demonstrating the feasibility of this goal and experimental application of the approach leveraging single-molecule protein measurements to identify a small number of model proteins. The implementation of PrISM as presented works by acquiring sequential affinity reagent binding measurements on single protein molecules. Counterintuitively, using affinity reagents with “poor” specificity (i.e. cross-reacting to many proteins) enables identification of tens of thousands of proteins with only hundreds of affinity reagents. To experimentally demonstrate PrISM, we use a small number of affinity reagents to quantify a larger number of proteins. In simulations, PrISM is able to identify more than 98% of proteins in human, mouse, yeast, and E. coli using 300 affinity reagents targeting short trimer epitopes. PrISM is robust to experimental confounders including non-specific binding and noisy, incomplete, or inaccurate estimation of affinity reagent to protein binding characteristics. Simulations of the approach with a chip containing 10 billion protein molecules measured in parallel show a dynamic range of detection of up to 9.5 and 11.5 orders of magnitude for HeLa cells and plasma, respectively. Using such a chip, the PrISM method can identify and quantify over 90% of the human proteome in a single experiment, potentially revolutionizing biomarker discovery and cancer research. Citation Format: Jarrett D. Egertson, Cassandra Stawicki, Taryn E. Gillies, James H. Joly, Noah Steiner, Kevin Cardenas, Jonathan B. Leano, Kevin Chen, Sophie Watts, Hunter B. Boyce, Dan DiPasquo, Alana Killeen, Vadim Lobanov, Greg Kapp, Sujal Patel, Parag Mallick. Toward comprehensive, single-molecule proteomics: Protein identification by short-epitope mapping [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB225.

Characterization of molecular interactions between cannabidiol and human plasma proteins (serum albumin and γ-globulin) by surface plasmon resonance, microcalorimetry, and molecular docking

A cannabidiol (CBD) oral solution (Epidiolex®) has been approved by the United States Food and Drug Administration to treat seizure conditions. However, the biomedical and pharmaceutical applications of CBD are hindered partially due to a limited understanding of CBD’s pharmacokinetic behaviors, such as its interactions with plasma proteins. Herein, we investigated the molecular interactions between CBD and two plasma proteins, namely, human serum albumin (HSA) and γ-globulin, using biophysical techniques including surface plasmon resonance (SPR), isothermal titration calorimetry, and differential scanning calorimetry, as well as molecular docking. CBD bound to HSA and γ-globulin in an exothermic manner (enthalpy: −9.3 ×104 and −3.7 ×104 kcal/mol, respectively) with a binding affinity of 1.8 × 10−5 and 1.3 × 10−5 M, respectively. The binding ratio between CBD and HSA or γ-globulin was approximately 1:1 and 3:1, respectively. Furthermore, computational modeling suggested that CBD and warfarin may bind to HSA independently, supported by data from a competitive SPR binding assay. Findings from the current study elucidate CBD’s plasma protein binding characteristics and shed light on their impact on CBD’s pharmacokinetic property.

Mechanistic Modeling of Placental Drug Transfer in Humans: How Do Differences in Maternal/Fetal Fraction of Unbound Drug and Placental Influx/Efflux Transfer Rates Affect Fetal Pharmacokinetics?

Background: While physiologically based pharmacokinetic (PBPK) models generally predict pharmacokinetics in pregnant women successfully, the confidence in predicting fetal pharmacokinetics is limited because many parameters affecting placental drug transfer have not been mechanistically accounted for.Objectives: The objectives of this study were to implement different maternal and fetal unbound drug fractions in a PBPK framework; to predict fetal pharmacokinetics of eight drugs in the third trimester; and to quantitatively investigate how alterations in various model parameters affect predicted fetal pharmacokinetics.Methods: The ordinary differential equations of previously developed pregnancy PBPK models for eight drugs (acyclovir, cefuroxime, diazepam, dolutegravir, emtricitabine, metronidazole, ondansetron, and raltegravir) were amended to account for different unbound drug fractions in mother and fetus. Local sensitivity analyses were conducted for various parameters relevant to placental drug transfer, including influx/efflux transfer clearances across the apical and basolateral membrane of the trophoblasts.Results: For the highly-protein bound drugs diazepam, dolutegravir and ondansetron, the lower fraction unbound in the fetus vs. mother affected predicted pharmacokinetics in the umbilical vein by ≥10%. Metronidazole displayed blood flow-limited distribution across the placenta. For all drugs, umbilical vein concentrations were highly sensitive to changes in the apical influx/efflux transfer clearance ratio. Additionally, transfer clearance across the basolateral membrane was a critical parameter for cefuroxime and ondansetron.Conclusion: In healthy pregnancies, differential protein binding characteristics in mother and fetus give rise to minor differences in maternal-fetal drug exposure. Further studies are needed to differentiate passive and active transfer processes across the apical and basolateral trophoblast membrane.

A novel lincRNA identified in buffalo oocytes with protein binding characteristics could hold the key for oocyte competence.

Studying the maternal oocyte-specific genes, in farm animals is a significant step towards delineating the underlying mechanisms that regulate oocyte quality, early embryonic development and survival. With the creation of buffalo oocyte-specific subtracted cDNA library, it has raised new questions which need to be answered. The present study has characterized one of the ESTs selected from the library and highlighted its importance in the oocyte quality. The selected EST was made full length by RLM-RACE and four transcript variants were identified. Bioinformatics analysis indicated the novelty of full-length transcript along with conserved intergenic nature. The largest transcript was identified as long intergenic noncoding RNA based upon coding potential calculator output. The expression analysis at different hours of oocyte maturation showed a significant variation in developmentally competent oocytes to that of incompetent ones. Along with this, the transcript was also found to have protein binding ability which was confirmed by RNA electrophoretic mobility shift assay. The protein used in the experiment was isolated from oocyte and cumulus cells via sonication. A novel lincRNA has been reported here that might have an important role in maturation of oocytes, inferred from its relative gene expression study and protein binding characteristics.

Nonclinical Pharmacokinetics, Protein Binding, and Elimination of KBP-7072, an Aminomethylcycline Antibiotic, in Animal Models

KBP-7072 is a semisynthetic aminomethylcycline with broad-spectrum activity against Gram-positive and Gram-negative pathogens, including multidrug-resistant bacterial strains. The pharmacokinetics (PK) of KBP-7072 after oral and intravenous (i.v.) administrations of single and multiple doses were investigated in animal models, including during fed and fasted states, and the protein binding and excretion characteristics were also evaluated. In Sprague-Dawley (SD) rats, beagle dogs, and CD-1 mice, KBP-7072 demonstrated a linear PK profile after the administration of single oral and i.v. and multiple oral doses. The oral bioavailability ranged from 12% to 32%. The mean time to maximum concentration (T max) ranged from 0.5 to 4 h, and the mean half-life ranged from approximately 6 to 11 h. The administration of oral doses in the fed state resulted in marked reductions in the maximum plasma concentration (C max) and the area under the concentration-time curve (AUC) compared with dosing in fasted animals. The mean bound fractions of KBP-7072 were 77.5%, 69.8%, 64.5%, 69.3%, and 69.2% in mouse, rat, dog, monkey, and human plasma, respectively. Following a single 22.5-mg/kg oral dose of KBP-7072 in SD rats, the cumulative excretion in feces was 64% and that in urine was 2.5% of the administered dose. The PK results in animal models are consistent with single- and multiple-ascending-dose studies in healthy volunteers and confirm the suitability of KBP-7072 for once-daily oral and i.v. administration in clinical studies.

The Impact of Plasma Protein Binding Characteristics and Unbound Concentration of Voriconazole on Its Adverse Drug Reactions.

This study investigated voriconazole (VRC) unbound plasma concentration and its relationship with adverse drug reactions (ADRs) in patients with malignant hematologic disease. Plasma samples were collected from patients or spiked in vitro. A time-saving rapid equilibrium dialysis assay was used for the separation of unbound and bound VRC, following a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis method for drug concentration detection. Liver function and treatment details were collected from the electronic medical records of patients. Protein concentration was determined according to instructions. VRC plasma protein binding rate (PPB) in patient is significantly higher [69.5 ± 6.2%] than that in in-vitro samples, influenced by total drug concentration (Ct), plasma protein concentration, and protein type. The α1-acid glycogen (AAG) has the highest affinity with VRC. Relationship between total PPB of VRC with PPB of individual protein is not a simple addition, but a compressive combination. Unbound drug concentration (Cu) of VRC shows significant relationships with Ct, protein concentration, AST level, metabolism type of CYP2C19 and co-administration of high PPB medicines. Unbound plasma concentration of VRC shows a more sensitive relationship with ADRs than Ct.

Population pharmacokinetics of ceftriaxone administered as continuous or intermittent infusion in critically ill patients.

To describe the population pharmacokinetics and protein-binding characteristics of unbound ceftriaxone administered as continuous or intermittent infusion. Additionally, to determine the optimal dosing regimen in critically ill patients. A pharmacokinetic study was performed in the ICU of a tertiary teaching hospital. Patients were treated with ceftriaxone as continuous or intermittent infusion. A population pharmacokinetic model was developed with non-linear mixed-effects analysis. Subsequently, the PTA of a 100% T>MIC was assessed for influential patient characteristics using Monte Carlo simulation. Fifty-five patients were included. The pharmacokinetics of ceftriaxone was best described by a one-compartment model with non-linear saturable protein binding including the following covariates: body weight, estimated CLCR, serum albumin concentration and mode of administration. For pathogens with an MIC of 1 mg/L, the simulation demonstrated that intermittent infusion of 2 g/24 h only resulted in a ≥90% PTA in patients with a reduced CLCR (0-60 mL/min). Intermittent infusion of 2 g/12 h led to sufficient exposure if CLCR was 0-90 mL/min and continuous infusion of 2 g/24 h led to a ≥90% PTA in all simulations (CLCR 0-180 mL/min). In the critically ill, the clearance of unbound ceftriaxone is closely related to CLCR. Furthermore, ceftriaxone protein binding is saturable, variable and dependent on serum albumin concentration. Intermittent dosing of 2 g/24 h ceftriaxone leads to subtherapeutic exposure in patients with a normal or increased CLCR. Treating these patients with continuous infusion of 2 g/24 h is more effective than an intermittent dosing regimen of 2 g/12 h.

Protein Binding Characteristics of the Principal Green Tea Catechins: A QCM Study Comparing Crude Extract to Pure EGCG.

Label-free detection methods such as the quartz crystal microbalance (QCM) are well suited to the analysis of molecular interactions in complex mixtures such as crude botanical extracts. In the present study, the binding characteristics of epigallocatechin gallate (EGCG) and crude green tea extract solutions to bovine serum albumin (BSA) have been investigated. The adsorbed mass levels onto BSA-functionalized surfaces were measured at various solution concentrations. Langmuir and Freundlich isotherms were used to model the adsorption data. The Langmuir isotherm better described the adsorption behavior with correlations of 0.68 and 0.70 for the EGCG and the crude extract solutions, respectively. The better fit of the Langmuir model indicates that adsorption occurs homogeneously and that aggregation is negligible. The mass saturation is estimated to be 58% higher for the crude green tea solution as compared to the pure EGCG solution (7.9 ng/cm2 for green tea and 5 ng/cm2 for EGCG). The increased adsorption for the crude extract indicates that the additional tea chemical constituents are binding to alternate sites on the protein molecule and that competitive binding is a nondominant effect. However, a reduced adsorption rate for the crude extract was also observed, indicating some presence of competitive mechanisms. The results demonstrate the utility of the QCM for the analysis of protein binding in crude mixtures as well as pure compounds.

Effects of an Ex Vivo Pediatric Extracorporeal Membrane Oxygenation Circuit on the Sequestration of Mycophenolate Mofetil, Tacrolimus, Hydromorphone, and Fentanyl.

With the expanding use of extracorporeal membrane oxygenation (ECMO), understanding drug pharmacokinetics has become increasingly important, particularly in pediatric patients. This ex vivo study examines the effect of a pediatric Quadrox-iD ECMO circuit on the sequestration and binding of mycophenolate mofetil (MMF), tacrolimus, and hydromorphone hydrochloride, which have not been extensively studied to date in pediatric ECMO circuits. Fentanyl, which has been well studied, was used as a comparator. ECMO circuits were set up using Quadrox-iD pediatric oxygenators and centrifugal pumps. The circuit was primed with whole blood and a reservoir was attached to represent a 5-kg patient. Fourteen French venous and 12 French arterial ECMO cannulas were inserted into the sealed reservoir. Temperature, pH, PO2, and PCO2 were monitored and corrected. MMF, tacrolimus, hydromorphone, and fentanyl were injected into the ECMO circuit. Serial blood samples were taken from a postoxygenator site at intervals over 12 hours, and levels were measured. Hydromorphone hydrochloride was not as significantly sequestered by the ex vivo pediatric ECMO circuit when compared with fentanyl. Both mycophenolic acid and tacrolimus serum concentrations were stable in the circuit over 12 hours. Hydromorphone may represent a useful medication for pain control for pediatric patients on ECMO due to its minimal sequestration. Mycophenolic acid and tacrolimus also did not show significant sequestration in the circuit, which was unexpected given their lipophilicity and protein-binding characteristics, but may provide insight into unexplored pharmacokinetics of particular medications in ECMO circuits.

Concentration, distribution, and influence of aging on the 18 kDa translocator protein in human brain: Implications for brain imaging studies

Positron emission tomography (PET) imaging of the translocator protein (TSPO) is widely used as a biomarker of microglial activation. However, TSPO protein concentration in human brain has not been optimally quantified nor has its regional distribution been compared to TSPO binding. We determined TSPO protein concentration, change with age, and regional distribution by quantitative immunoblotting in autopsied human brain. Brain TSPO protein concentration (>0.1 ng/µg protein) was higher than those reported by in vitro binding assays by at least 2 to 70 fold. TSPO protein distributed widely in both gray and white matter regions, with distribution in major gray matter areas ranked generally similar to that of PET binding in second-generation radiotracer studies. TSPO protein concentration in frontal cortex was high at birth, declined precipitously during the first three months, and increased modestly during adulthood/senescence (10%/decade; vs. 30% for comparison astrocytic marker GFAP). As expected, TSPO protein levels were significantly increased (+114%) in degenerating putamen in multiple system atrophy, providing further circumstantial support for TSPO as a gliosis marker. Overall, findings show some similarities between TSPO protein and PET binding characteristics in the human brain but also suggest that part of the TSPO protein pool might be less available for radioligand binding.

In vitro safety pharmacology evaluation of 2-hydroxybenzylamine acetate

2-hydroxybenzylamine (2-HOBA), a compound found in buckwheat, is a potent scavenger of reactive γ-ketoaldehydes, which are increased in diseases associated with inflammation and oxidative stress. While the potential of 2-HOBA is promising, studies were needed to characterize the safety of the compound before clinical trials. In a series of experiments, the risks of 2-HOBA-mediated mutagenicity and cardio-toxicity were assessed in vitro. The effects of 2-HOBA on the mRNA expression of select cytochrome P450 (CYP) enzymes were also assessed in cryopreserved human hepatocytes. Further, the distribution and metabolism of 2-HOBA in blood were determined. Our results indicate that 2-HOBA is not cytotoxic or mutagenic in vitro and does not induce the expression of CYP1A2, CYP2B6, or CYP3A4 in human hepatocytes. The results of the hERG testing showed a low risk of cardiac QT wave prolongation. Plasma protein binding and red blood cell distribution characteristics indicate low protein binding and no preferential distribution into erythrocytes. The major metabolites identified were salicylic acid and the glycoside conjugate of 2-HOBA. Together, these findings support development of 2-HOBA as a nutritional supplement and provide important information for the design of further preclinical safety studies in animals as well as for human clinical trials with 2-HOBA.

Hyperbranched Polyglycerol Derivatives as Prospective Copper Nanotransporter Candidates.

Hyperbranched polyglycerol (hPG) has been used as a multivalent scaffold to develop a series of nanocarriers capable of high-affinity encapsulation of copper (Cu). A rationally selected set of Cu-complexing motifs has been conjugated to hPG hydroxyl groups to render the constructs potentially usable as exogenous sources of Cu for addressing different pathological conditions associated with Cu-deficiency. We have utilized a newly discovered route to attach Cu-binding domains exclusively within a hPG core by selective differentiation between the primary and secondary hydroxyl groups of the polyol. These hPG-derivatives were found to form a stable complex with Cu ions depending on the type of immobilized ligands and corresponding degree of functionalization. In addition, these Cu-bearing nano-complexes demonstrated moderately cationic surface charge resulting in adjustable protein-binding characteristics and low cellular toxicity profile. We envision that these Cu-loaded hPG nanocarriers can be used as a stable platform to transport the metal ion across the systemic circulation to supply bioavailable quantity of Cu in disease-afflicted tissues.