TY  - JOUR
A1  - Schmidt, Sebastian
A1  - Holzgrabe, Ulrike
T1  - Do the enantiomers of ketamine bind enantioselectively to human serum albumin?
JF  - European Journal of Pharmaceutical Sciences
N2  - The binding of drugs to plasma proteins is an important process in the human body and has a significant influence on pharmacokinetic parameter. Human serum albumin (HSA) has the most important function as a transporter protein. The binding of ketamine to HSA has already been described in literature, but only of the racemate. The enantiomerically pure S-ketamine is used as injection solution for induction of anesthesia and has been approved by the Food and Drug Administration for the therapy of severe depression as a nasal spray in 2019. The question arises if there is enantioselective binding to HSA. Hence, the aim of this study was to investigate whether there is enantioselective binding of S-and R-ketamine to HSA or not. Ultrafiltration (UF) followed by chiral capillary electrophoretic analysis was used to determine the extent of protein binding. Bound fraction to HSA was 71.2 % and 64.9 % for enantiomerically pure R- and S-ketamine, respectively, and 66.5 % for the racemate. Detailed binding properties were studied by Saturation Transfer Difference (STD)-, waterLOGSY- and Carr-Purcell-Meiboom-Gill (CPMG)-NMR spectroscopy. With all three methods, the aromatic ring and the N-methyl group could be identified as the structural moieties most strongly involved in binding of ketamine to HSA. pK\(_{aff}\) values determined using UF and NMR indicate that ketamine is a weak affinity ligand to HSA and no significant differences in binding behavior were found between the individual enantiomers and the racemate.
KW  - protein binding
KW  - albumin
KW  - electrophoresis
KW  - nuclear magnetic resonance spectroscopy
KW  - ultrafiltration
KW  - enantioselectivity
Y1  - 2024
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-349791
VL  - 192
ER  - 
TY  - JOUR
A1  - Schmidt, Sebastian
A1  - Zehe, Markus
A1  - Holzgrabe, Ulrike
T1  - Characterization of binding properties of ephedrine derivatives to human alpha-1-acid glycoprotein
JF  - European Journal of Pharmaceutical Sciences
N2  - 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.
KW  - protein binding
KW  - AGP
KW  - ultrafiltration
KW  - saturation transfer difference NMR
KW  - epitope mapping
KW  - ephedrine
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300848
VL  - 181
ER  - 
TY  - JOUR
A1  - Shah, Nirav R.
A1  - Bulitta, Jürgen B.
A1  - Kinzig, Martina
A1  - Landersdorfer, Cornelia B.
A1  - Jiao, Yuanyuan
A1  - Sutaria, Dhruvitkumar S.
A1  - Tao, Xun
A1  - Höhl, Rainer
A1  - Holzgrabe, Ulrike
A1  - Kees, Frieder
A1  - Stephan, Ulrich
A1  - Sörgel, Fritz
T1  - Novel population pharmacokinetic approach to explain the differences between cystic fibrosis patients and healthy volunteers via protein binding
JF  - Pharmaceutics
N2  - The pharmacokinetics in patients with cystic fibrosis (CF) has long been thought to differ considerably from that in healthy volunteers. For highly protein bound β-lactams, profound pharmacokinetic differences were observed between comparatively morbid patients with CF and healthy volunteers. These differences could be explained by body weight and body composition for β-lactams with low protein binding. This study aimed to develop a novel population modeling approach to describe the pharmacokinetic differences between both subject groups by estimating protein binding. Eight patients with CF (lean body mass [LBM]: 39.8 ± 5.4kg) and six healthy volunteers (LBM: 53.1 ± 9.5kg) received 1027.5 mg cefotiam intravenously. Plasma concentrations and amounts in urine were simultaneously modelled. Unscaled total clearance and volume of distribution were 3% smaller in patients with CF compared to those in healthy volunteers. After allometric scaling by LBM to account for body size and composition, the remaining pharmacokinetic differences were explained by estimating the unbound fraction of cefotiam in plasma. The latter was fixed to 50% in male and estimated as 54.5% in female healthy volunteers as well as 56.3% in male and 74.4% in female patients with CF. This novel approach holds promise for characterizing the pharmacokinetics in special patient populations with altered protein binding.
KW  - cystic fibrosis patients
KW  - healthy volunteers
KW  - cefotiam
KW  - beta-lactam antibiotics
KW  - population pharmacokinetics
KW  - protein binding
KW  - allometric scaling
KW  - body size
KW  - body composition
KW  - S-ADAPT
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-196934
SN  - 1999-4923
VL  - 11
IS  - 6
ER  - 
TY  - JOUR
A1  - Devine, Eric
A1  - Krieter, Detlef H.
A1  - Rüth, Marieke
A1  - Jankovski, Joachim
A1  - Lemke, Horst-Dieter
T1  - Binding Affinity and Capacity for the Uremic Toxin Indoxyl Sulfate
JF  - Toxins
N2  - Protein binding prevents uremic toxins from removal by conventional extracorporeal therapies leading to accumulation in maintenance dialysis patients. Weakening of the protein binding may enhance the dialytic elimination of these toxins. In ultrafiltration and equilibrium dialysis experiments, different measures to modify the plasma binding affinity and capacity were tested: (i), increasing the sodium chloride (NaCl) concentration to achieve a higher ionic strength; (ii), increasing the temperature; and (iii), dilution. The effects on the dissociation constant K-D and the protein bound fraction of the prototypical uremic toxin indoxyl sulfate (IS) in plasma of healthy and uremic individuals were studied. Binding of IS corresponded to one site binding in normal plasma. K-D increased linearly with the NaCl concentration between 0.15 (K-D = 13.2 +/- 3.7 mu M) and 0.75 M (K-D = 56.2 +/- 2.0 mu M). Plasma dilution further reduced the protein bound toxin fraction by lowering the protein binding capacity of the plasma. Higher temperatures also decreased the protein bound fraction of IS in human plasma. Increasing the NaCl concentration was effective to weaken the binding of IS also in uremic plasma: the protein bound fraction decreased from 89% +/- 3% to 81% +/- 3% at 0.15 and 0.75 M NaCl, respectively. Dilution and increasing the ionic strength and temperature enhance the free fraction of IS allowing better removal of the substance during dialysis. Applied during clinical dialysis, this may have beneficial effects on the long-term outcome of maintenance dialysis patients.
KW  - protein binding
KW  - hemodialysis
KW  - human serum albumin
KW  - dialyzer membrane
KW  - P-cresyl sulfate
KW  - removal
KW  - dialysate
KW  - progression
KW  - clearance
KW  - kidney disease;
KW  - protein-bound solutes
KW  - chronic kidney-disease
KW  - ionic strength
KW  - uremic toxin
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117486
VL  - 6
IS  - 2
ER  - 
TY  - THES
A1  - Devine, Eric
T1  - Increased removal of protein bound uremic toxins through reversible modification of the ionic strength during hemodiafiltration
T1  - Erhöhte Elimination proteingebundener Urämietoxine durch reversible Modifikation der Ionenstärke während der Hämodiafiltration
N2  - A large number of metabolic waste products accumulate in the blood of patients with renal failure. Since these solutes have deleterious effects on the biological functions, they are called uremic toxins and have been classified in three groups: 1) small water soluble solutes (MW < 500 Da), 2) small solutes with known protein binding (MW < 500 Da), and 3) middle molecules (500 Da < MW < 60 kDa). Protein bound uremic toxins are poorly removed by conventional hemodialysis treatments because of their high protein binding and high distribution volume. The prototypical protein bound uremic toxins indoxyl sulfate (IS) and p-cresyl sulfate (pCS) are associated with the progression of chronic kidney disease, cardiovascular outcomes, and mortality of patients on maintenance hemodialysis. Furthermore, these two compounds are bound to albumin, the main plasma protein, via electrostatic and/or Van-der-Waals forces. The aim of the present thesis was to develop a dialysis strategy, based on the reversible modification of the ionic strength in the blood stream by increasing the sodium chloride (NaCl) concentration, in order to enhance the removal of protein bound substances, such as IS and pCS, with the ultimate goal to improve clinical patient outcomes. Enhancing the NaCl concentration ([NaCl]) in both human normal and uremic plasma was efficient to reduce the protein bound fraction of both IS and pCS by reducing their binding affinity to albumin. Increasing the ionic strength was feasible during modified pre-dilution hemodiafiltration (HDF) by increasing the [NaCl] in the substitution fluid. The NaCl excess was adequately removed within the hemodialyzer. This method was effective to increase the removal rate of both protein bound uremic toxins. Its ex vivo hemocompatibility, however, was limited by the osmotic shock induced by the high [NaCl] in the substituate. Therefore, modified pre-dilution HDF was further iterated by introducing a second serial cartridge, named the serial dialyzers (SDial) setup. This setting was validated for feasibility, hemocompatibility, and toxin removal efficiency. A better hemocompatibility at similar efficacy was obtained with the SDial setup compared with the modified pre-dilution HDF. Both methods were finally tested in an animal sheep model of dialysis to verify biocompatibility. Low hemolysis and no activation of both the complement and the coagulation systems were observed when increasing the [NaCl] in blood up to 0.45 and 0.60 M with the modified pre-dilution HDF and the SDial setup, respectively. In conclusion, the two dialysis methods developed to transitory enhance the ionic strength in blood demonstrated adequate biocompatibility and improved the removal of protein bound uremic toxins by decreasing their protein bound fraction. The concepts require follow-on clinical trials to assess their in vivo efficacy and their impact on long-term clinical outcomes.
N2  - Eine große Zahl von Stoffwechselprodukten akkumuliert im Blut urämischer Patienten mit Nierenversagen. Da diese Moleküle schädliche Wirkungen auf die biologischen Funktionen haben, werden sie als Urämietoxine bezeichnet. Man teilt sie in drei Gruppen ein: 1) kleine wasserlösliche Substanzen (MG < 500 Da), 2) kleine, proteingebundene Substanzen (MG < 500 Da), 3) Mittelmoleküle (500 Da < MG < 60 kDa). Proteingebundene Urämietoxine werden wegen ihrer starken Proteinbindung und ihres Verteilungsvolumen durch klassische Hämodialyseverfahrens nur schlecht entfernt. Die prototypischen proteingebundenen Urämietoxine Indoxylsulfat (IS) und p-Cresylsulfat (pCS) sind bei chronischen niereninsuffizienten Patienten mit dem Fortschreiten der Niereninsuffizienz, Herz-Kreislauf-Erkrankungen und der Mortalität verbunden. Außerdem sind diese beiden Toxine an Albumin, dem wichtigsten Plasmaprotein, durch elektrostatische und/oder Van-der-Waals-Kräfte gebunden. Das Ziel der vorliegenden Arbeit war es, ein Dialyseverfahren basierend auf einer reversiblen Modifikation der Ionenstärke im Blut durch Erhöhung der Natriumchlorid (NaCl)-Konzentration zu entwickeln, um die Entfernung von proteingebundenen Molekülen wie IS und pCS zu erhöhen und dadurch eine Verbesserung des klinischen Verlauf der Patienten zu erreichen. Die Erhöhung der NaCl-Konzentration ([NaCl]) sowohl in normalem als auch in urämischem menschlichem Plasma war geeignet, um den proteingebundenen Anteil von IS und pCS durch Schwächung ihrer Bindungsaffinität zu Albumin zu verringern. Die Erhöhung der Ionenstärke während einer modifizierten Prädilutions-Hämodiafiltration (HDF) konnte durch eine Erhöhung der [NaCl] in der Substitutionslösung umgesetzt werden; dabei wurde der NaCl-Überschuss innerhalb des Dialysators vollständig entfernt. Dieses Verfahren war effektiv, um die Entfernungsrate beider proteingebundenen Urämietoxine zu steigern; seine Ex-vivo-Hämokompatibilität war allerdings aufgrund des osmotischen Schocks infolge der hohen [NaCl] im Substituat begrenzt. Deshalb wurde eine Iteration der modifizierten Prädilutions-HDF durch Einbau eines zweiten, seriellen Dialysators vorgenommen, bezeichnet als serielles Dialysator System (SDial). Diese letzte Methode wurde dann bezüglich der Durchführbarkeit, der Hämokompatibilität und Toxinentfernung validiert. Durch das SDial-System konnte, verglichen mit der modifizierten Prädilutions-HDF, eine bessere Hämokompatibilität bei ähnlicher Wirksamkeit erzielt werden. Beide Methoden, modifizierte Prädilutions-HDF und SDial System, wurden abschließend in ein Tierdialysemodell mit Schafen transferiert, wobei eine zufriedenstellende Biokompatibilität demonstriert werden konnte. Beide, zur vorübergehenden Erhöhung der Ionenstärke im Blut entwickelten Dialyseverfahren zeigten bei zufriedenstellender Biokompatibilität eine verbesserte Entfernung proteingebundener Urämietoxine durch Reduktion ihrer proteingebundenen Fraktion. In einem nächsten Schritt sind klinische Studien erforderlich, die diese Konzepte bezüglich ihrer In-vivo-Wirksamkeit und ihrer langfristigen Wirkung auf den Krankheitsverlauf untersuchen.
KW  - Hämodiafiltration
KW  - Ionenstärke
KW  - Proteinbindung
KW  - Urämietoxine
KW  - Hämodialyse
KW  - Biokompatibilität
KW  - Ionic strength
KW  - protein binding
KW  - uremic toxin
KW  - hemodialysis
KW  - biocompatibility
KW  - Urämie
KW  - Toxin
KW  - Ionenstärke
KW  - Blut
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-83583
ER  -