Delivery of Chemically Modified Peptides and Proteins through the Blood-Brain Barrier

Peptide- and protein-based signal substances serve important functions in our body. Neuropeptides are a class of neurotransmitters involved in specific communication in the peripheral and central nervous system. Therefore, natural and synthetic neuropeptides have potential significance as neuropharmaceuticals. Monoclonal antibodies (MAb) represent another type of proteins which can be used potentially as diagnostic or therapeutic agents. However, the poor permeability of peptides and proteins through biological membranes (e.g. cell membranes) is among the principal reasons, why these compounds have not yet gained the significance as neuroactive drugs in practice which theoretically could be expected from their bioactivity. The blood-brain barrier (BBB) consists of tightly sealed cell membranes and prevents the free access of large and/or hydrophilic substances from blood to brain. There are, however, active uptake systems for some endogenous peptides and proteins present at the BBB, which may be exploited in a physiological approach of drug delivery to the brain. After an introduction to the physiology of the BBB, an overview of potential strategies of drug delivery is given. The physiological approach is presented with examples, showing how peptides and proteins can be modified to achieve pharmacologically significant brain concentrations after systemic administration

Absatzanalyse für regionale und fair gehandelte Öko-Lebensmittel im Rahmen der BÖL-Projekte 08OE132 und 08OE105

Ziel des vorliegenden Forschungsvorhabens war es, eine Informationsgrundlage über den Verkaufserfolg von fairen und regionalen Öko-Lebensmitteln im Naturkostfachhandel zu gewinnen. Zum einen wurde der absolute Absatzerfolg dieser Produkte analysiert, zum anderen die Auswirkung der Einführung bzw. Neuauszeichnung der Testprodukte auf die jeweiligen Warengruppenumsätze. Im Rahmen von Storetests wurde der Absatz von Testprodukten des BioFair-Vereins sowie der fair & regional-Initiative Berlin-Brandenburg unter realen Verkaufsbedingungen im Naturkostfachhandel analysiert. Parallel zur Einführung der Testprodukte wurde jeweils eine Verkaufsförderungsaktion von den Initiativen, die die Testprodukte stellten, durchgeführt, die jeweils von einem Storecheck begleitet wurde. Anhand der Abverkaufsdaten wurde die durchschnittliche wöchentliche Steigerung des Absatzes in der Aktionswoche und im zehnwöchigen Nachlauf gegenüber dem Vorlauf gemessen. Die Datenaufnahme erfolgte über die Scannerdaten der Kassensysteme in den Testgeschäften und wurde von dem Marktforschungsinstitut bioVista durchgeführt. Aufgrund von erheblichen Problemen der beiden Initiativen bei der Planung und Umsetzung der Testverkäufe waren die erzielten Ergebnisse wenig aufschlussreich. Bei den meisten Testprodukten konnten die Abverkäufe weder kurz- noch mittelfristig gesteigert werden. Insgesamt betrachtet lassen sich aus den Ergebnissen der Analyse kaum inhaltliche Schlussfolgerungen für Hersteller und Händler von fairen und regionalen Öko-Lebensmitteln ableiten. Es hat sich gezeigt, dass sich ethische Produktattribute wie ‚Fairness‘ und ‚Regionalität‘ nicht von selbst verkaufen, sondern die Markteinführung der Produkte und die Umsetzung von begleitenden Verkaufsförderungen ein in allen Bereichen professionelles Marketing erfordern. Ob dieses von Vereinen ohne wirtschaftliches Eigeninteresse zu leisten ist, ist in Frage zu stellen

Effects of Hepatic Ischemia-Reperfusion Injury on the Blood-Brain Barrier Permeability to [14C] and [13C]Sucrose

Hepatic encephalopathy that is associated with severe liver failure may compromise the blood-brain barrier (BBB) integrity. However, the effects of less severe liver diseases, in the absence of overt encephalopathy, on the BBB are not well understood. The goal of the current study was to investigate the effects of hepatic ischemia-reperfusion (IR) injury on the BBB tight junction permeability to small, hydrophilic molecules using the widely used [14C]sucrose and recently-proposed alternative [13C]sucrose as markers. Rats were subjected to 20 min of hepatic ischemia or sham surgery, followed by 8 h of reperfusion before administration of a single bolus dose of [14C] or [13C]sucrose and collection of serial (0–30 min) blood and plasma and terminal brain samples. The concentrations of [14C] and [13C]sucrose in the samples were determined by measurement of total radioactivity (nonspecific) and LC-MS/MS (specific), respectively. IR injury significantly increased the blood, plasma, and brain concentrations of both [14C] and [13C]sucrose. However, when the brain concentrations were corrected for their respective area under the blood concentration-time curve, only [14C]sucrose showed significantly higher (30%) BBB permeability values in the IR animals. Because [13C]sucrose is a more specific BBB permeability marker, these data indicate that our animal model of hepatic IR injury does not affect the BBB tight junction permeability to small, hydrophilic molecules. Methodological differences among studies of the effects of liver diseases on the BBB permeability may confound the conclusions of such studies

Acute Depression of Energy Metabolism After Microdialysis Probe Implantation is Distinct from Ischemia-Induced Changes in Mouse Brain

The current study used measurements of metabolites and markers of membrane integrity to determine the most suitable time point for microdialysis experiments following probe implantation. Leakage of Evans blue and sodium fluorescein indicated increased BBB permeability only immediately (15 min), but not 1.5 and 24 h following probe implantation. Acute implantation decreased glucose and lactate levels relative to the levels after 24 h (to 13–37% and 25–60%, respectively). No change in extracellular levels of glutamate or glycerol was seen. In comparison to acute probe implantation, the pattern of damage under brain ischemia (middle cerebral artery occlusion) differed: While glucose levels dropped, lactate levels rose after ischemia, and glutamate (tenfold) and glycerol (eightfold) increased sharply. In conclusion, acute implantation of a microdialysis probe causes transient depression of the energy metabolites, glucose and lactate, likely due to injury-induced hypermetabolism. However, no massive tissue damage or severe ischemic conditions around the probe occur

Unifying the Mathematical Modeling of \u3cem\u3ein vivo\u3c/em\u3e and \u3cem\u3ein vitro\u3c/em\u3e Microdialysis

A unifying approach is presented for developing mathematical models of microdialysis that are applicable to both in vitro and in vivo situations. Previous models for cylindrical probes have been limited by accommodating analyte diffusion through the surrounding medium in the radial direction only, i.e., perpendicular to the probe axis, or by incomplete incorporation of diffusion in the axial direction. Both radial and axial diffusion are included in the present work by employing two-dimensional finite element analysis. As in previous models, the nondimensional clearance modulus (Θ) represents the degree to which analyte clearance from the external medium influences diffusion through the medium for systems exhibiting analyte concentration linearity. Incorporating axial diffusion introduces a second dimensionless group, which is the length-to-radius aspect ratio of the membrane. These two parameter groups uniquely determine the external medium permeability, which is time dependent under transient conditions. At steady-state, the dependence of this permeability on the two groups can be approximated by an algebraic formula for much of the parameter ranges. Explicit steady-state expressions derived for the membrane and fluid permeabilities provide good approximations under transient conditions (quasi-steady-state assumption). The predictive ability of the unifying approach is illustrated for microdialysis of sucrose in vivo (brain) and inert media in vitro, under both well-stirred and quiescent conditions

Dynamik des Kaufverhaltens im Bio-Sortiment

Das Gesamtziel des vorliegenden Forschungsprojekts war es, eine detaillierte Informationsgrundlage zum tatsächlichen Kaufverhalten von deutschen Haushalten bei ökologischen Lebensmitteln auf der Basis von Haushaltspaneldaten zu erstellen. Dazu sollten zum einen relevante Aspekte des Kaufverhaltens von Haushalten bei Öko-Lebensmitteln im Zeitverlauf von 2004 bis 2008 analysiert und zum anderen die Einflussfaktoren des Kaufverhaltens bei Öko-Lebensmitteln für das Jahr 2008 identifiziert werden. Auf der Basis des tatsächlichen Kaufverhaltens wurden Kundensegmente des Öko-Markts identifiziert und ihr Kaufverhalten näher untersucht. Es zeigte sich, dass trotz einer stetigen Ausweitung der Käuferreichweite im Jahr 2008 nur eine kleine Gruppe von 17 % der Haushalte für 80 % des Umsatzes mit ökologischen Produkten verantwortlich war. Neue Erkenntnisse brachte die Analyse der Einflussfaktoren des Kaufverhaltens bei Öko-Lebensmitteln. Während der Einfluss der klassischen Segmentierungskriterien Einkommen und Bildung nicht signifikant nachweisbar war, wurde das Kaufverhalten primär von egoistischen Motiven bestimmt. Verbraucher kaufen Öko-Produkte, weil sie ihnen besser schmecken, weniger Rückstände enthalten und als gesünder angesehen werden. Vom Öko-Markt bisher nicht erreicht werden dagegen insbesondere Verbraucher, die gegenüber Fastfood und Snacks positiv eingestellt sind. Die Analyse der Einkaufsmengen bei saisonalen Preisschwankungen von Obst und Gemüse zeigte, dass nur ein geringer Einfluss von Produktpreisen und Mehrpreisen für ökologische Lebensmittel besteht. Neben der Kommunikation der Mehrwerte hinsichtlich gesundheitlicher und geschmacklicher Aspekte, die vor allem die etablierten Öko-Käufer anspricht, sollten die Öko-Sortimente um Produkte erweitert werden, die durch eine Orientierung an konventionellen Produkten hinsichtlich Geschmack und Aufmachung vor allem neue, junge Käuferschichten erreichen

Evaluation of [14C] and [13C]Sucrose as Blood-Brain Barrier Permeability Markers

Non-specific quantitation of [14C]sucrose in blood and brain has been routinely used as a quantitative measure of the in vivo blood-brain barrier (BBB) integrity. However, the reported apparent brain uptake clearance (Kin) of the marker varies widely (∼100 fold). We investigated the accuracy of the use of the marker in comparison with a stable isotope of sucrose ([13C]sucrose) measured by a specific LC-MS/MS method. Rats received single doses of each marker, and the Kin values were determined. Surprisingly, the Kin value of [13C]sucrose was 6-7 fold lower than that of [14C]sucrose. Chromatographic fractionation after in vivo administration of [14C]sucrose indicated that the majority of the brain content of radioactivity belonged to compounds other than the intact [14C]sucrose. However, mechanistic studies failed to reveal any substantial metabolism of the marker. The water: octanol partition coefficient of [14C]sucrose was \u3e 2 fold higher than that of [13C]sucrose, indicating presence of lipid-soluble impurities in the [14C]sucrose solution. Our data indicate that [14C]sucrose overestimates the true BBB permeability to sucrose. We suggest that specific quantitation of the stable isotope (13C) of sucrose is a more accurate alternative to the current widespread use of the radioactive sucrose as a BBB marker

Effects of Short-Term Portacaval Anastomosis on the Peripheral and Brain Disposition of the Blood-Brain Barrier Permeability Marker Sodium Fluorescein in Rats

Contradictory results have been reported with regard to the effects of various models of hepatic encephalopathy on the blood-brain barrier (BBB) permeability, which may be due partly to the use of brain concentrations of BBB markers without attention to their peripheral pharmacokinetics. The purpose of the current study was to investigate the effects of short-term portacaval anastomosis (PCA), a type B model of hepatic encephalopathy, on the peripheral pharmacokinetics and brain distribution of sodium fluorescein (FL), which is a small molecule marker of BBB passive permeability. A single 25 mg/kg dose of FL was administered intravenously to 10-day PCA and sham-operated rats, and serial blood and bile (0-30 min) and terminal (30 min) brain samples were collected, and the concentrations of FL and its glucuronidated metabolite (FL-Glu) were measured by HPLC. Additionally, the free fractions of FL (fu) in all the plasma samples were determined, and the effects of bile salts on fu were investigated in vitro. Passive permeability of BBB to FL was estimated by brain uptake clearance (Kin) based on both the brain concentrations of FL and plasma concentrations of free (unbound) FL. PCA caused a 26% increase in the fu of FL in plasma, which was due to competition of bile acids with FL for binding to plasma proteins. Additionally, PCA reduced the biliary excretion of FL-Glu by 55%. However, free Kin values (μl/min/g brain) for the sham (0.265 ± 0.034) and PCA (0.228 ± 0.038) rats were not significantly different. It is concluded that whereas 10-day PCA alters the peripheral pharmacokinetics of FL, it does not significantly affect the BBB permeability to the marker

Effects of Hepatic Ischemia-Reperfusion Injury on the P-Glycoprotein Activity at the Liver Canalicular Membrane and Blood-Brain Barrier Determined by In Vivo Administration of Rhodamine 123 in Rats

Purpose To investigate the effects of normothermic hepatic ischemia-reperfusion (IR) injury on the activity of P-glycoprotein (P-gp) in the liver and at the blood-brain barrier (BBB) of rats using rhodamine 123 (RH-123) as an in vivo marker. Methods Rats were subjected to 90 min of partial ischemia or sham surgery, followed by 12 or 24 h of reperfusion. Following intravenous injection, the concentrations of RH-123 in blood, bile, brain, and liver were used for pharmacokinetic calculations. The protein levels of P-gp and some other transporters in the liver and brain were also determined by Western blot analysis. Results P-gp protein levels at the liver canalicular membrane were increased by twofold after 24 h of reperfusion. However, the biliary excretion of RH-123 was reduced in these rats by 26%, presumably due to IR-induced reductions in the liver uptake of the marker and hepatic ATP concentrations. At the BBB, a 24% overexpression of P-gp in the 24-h IR animals was associated with a 30% decrease in the apparent brain uptake clearance of RH-123. The pharmacokinetics or brain distribution of RH-123 was not affected by the 12-h IR injury. Conclusions Hepatic IR injury may alter the peripheral pharmacokinetics and brain distribution of drugs that are transported by P-gp and possibly other transporters

Simultaneous UPLC–MS/MS Analysis of Two Stable Isotope Labeled Versions of Sucrose in Mouse Plasma and Brain Samples as Markers of Blood-Brain Barrier Permeability and Brain Vascular Space

Blood Brain Barrier (BBB) permeability is frequently compromised in the course of diseases affecting the central nervous system (CNS). Sucrose is a low molecular weight, hydrophilic marker with low permeability at the naive BBB and therefore one of the widely used indicators of barrier integrity. Our laboratory recently developed a highly sensitive UPLC-MS/MS method for stable isotope labelled [13C12]sucrose in biological matrices. Correction of total brain concentration for contribution of intravascular space is required in such experiments in order to accurately measure BBB permeability, and it is often accomplished by vascular perfusion with buffer solutions prior to brain sampling. The purpose of the present study was to develop a UPLC-MS/MS method, which allows simultaneous analysis of two different stable isotope labeled sucrose variants, one of which can be utilized as a vascular marker. The first analyte, [13C12]sucrose, serves to quantify brain uptake clearance as a measure of BBB permeability, while the second analyte, [13C6]sucrose, is administered just before termination of the animal experiment and is considered as the vascular marker. [2H2]sucrose is used as the internal standard for both 13C labeled compounds. Because the majority of recent studies on CNS diseases employ mice, another objective was to validate the new technique in this species. The UPLC-MS/MS method was linear (r2≥0.99) in the tested concentration ranges, from 10 to 1,000 ng/mL for both analytes in plasma, from 2 to 400 ng/g [13C12]sucrose in brain and from 10 to 400 ng/g [13C6]sucrose in brain. It was also validated in terms of acceptable intra and inter run accuracy and precision values (n=5). The dual analyte technique was applied in a study in mice. One group received intravenous bolus injections of 10 mg/kg [13C12]sucrose at time 0, and 10 mg/kg [13C6]sucrose at 14.5 min, and subsequent terminal blood and brain sampling was performed at 15 min. For comparison, another group received an intravenous bolus dose of 10 mg/kg [13C12]sucrose and was submitted to transcardiac perfusion with buffer after 15 min. We demonstrate that the two alternative techniques to correct for intravascular content deliver equivalent values for brain concentration and brain uptake clearance