Animal models are an important tool for studying ischemic mechanisms of stroke. Among them, the middle cerebral artery occlusion (MCAO) model via the intraluminal suture method in rodents is closest to human ischemic stroke. It is a model of transient occlusion followed by reperfusion, thus representing cerebral ischemia-reperfusion model that simulates patients with vascular occlusion and timely recanalization. Although reperfusion is very beneficial for the possibility of preserving brain functions after ischemia, it also brings a great risk in the form of brain edema, which can cause the development of intracranial hypertension, and increasing morbidity and mortality. In this paper, we present the results of our own transient reperfusion model of MCAO in which we tested the permeability of the blood-brain barrier (BBB) using Evans blue (EB), an intravital dye with a high molecular weight (68,500 Da) that prevents its penetration through the intact BBB. A total of 15 animals were used in the experiment and underwent the following procedures: insertion of the MCA occluder; assessment of ischemia by 2,3,5 -Triphenyltetrazolium chloride (TTC) staining; assessment of the BBB permeability using brain EB distribution. The results are presented and discussed. The test of BBB permeability using EB showed that 120 minutes after induction of ischemia, the BBB is open for the entry of large molecules into the brain. We intend to use this finding to time the application of neuroprotective agents via ICA injection in our next stroke model. Keywords: Cerebral ischemia-reperfusion model, Middle cerebral artery occlusion, Blood-brain barrier, 2,3,5 -Triphenyltetrazolium chloride, Evans blue.
- MeSH
- Evansova modř MeSH
- hematoencefalická bariéra * metabolismus MeSH
- infarkt arteria cerebri media * metabolismus MeSH
- ischemie mozku metabolismus MeSH
- kapilární permeabilita MeSH
- krysa rodu rattus MeSH
- modely nemocí na zvířatech * MeSH
- permeabilita MeSH
- pilotní projekty MeSH
- potkani Sprague-Dawley MeSH
- reperfuzní poškození * metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Sildenafil citrate has low oral bioavailability, systemic adverse effects, and a relatively delayed action. These issues may be addressed through direct transdermal delivery to the penis. This study aims to investigate the microemulsion formulation of the drug for effective transdermal delivery. Sildenafil citrate was formulated as a microemulsion using clove oil, dimethyl sulphoxide, phosphate buffer (pH 7), propylene glycol, Tween®80, and distilled water. Different proportions of these components were used to create six formulations of the microemulsion (F1-F6), which were then characterised by their physical appearance and clarity, pH, viscosity, conductivity, percent transmission, and droplet size. Furthermore, the stability, content analysis, in-vitro drug release, and transdermal permeation of sildenafil citrate from the generated drug-loaded microemulsions were studied. All prepared formulas contained nano-sized oil droplets (less than 20 nm), and the pH values were within the range of skin pH; however, two formulas were not transparent. Additionally, all formulations were thermodynamically stable, passing freeze-thaw, heating-cooling, and centrifugation tests. Next, the formulas demonstrated zero-order release kinetics, indicating that they can provide a sustained release profile for sildenafil citrate. Finally, the microemulsion formulation exhibited a 2.8-fold enhancement in skin permeation compared with that of the sildenafil citrate suspension. The prepared microemulsions demonstrated beneficial physical properties and skin permeation profiles that are promising for the local administration of sildenafil citrate.
- Klíčová slova
- mikroemulze,
- MeSH
- aplikace kožní * MeSH
- emulze MeSH
- hřebíčkový olej MeSH
- krysa rodu rattus MeSH
- lékové formy MeSH
- modely u zvířat MeSH
- permeabilita MeSH
- příprava léků metody MeSH
- sildenafil citrát * aplikace a dávkování farmakokinetika farmakologie MeSH
- stabilita léku MeSH
- suspenze MeSH
- uvolňování léčiv MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- klinická studie MeSH
The permeation of small molecules across biological membranes is a crucial process that lies at the heart of life. Permeation is involved not only in the maintenance of homeostasis at the cell level but also in the absorption and biodistribution of pharmacologically active substances throughout the human body. Membranes are formed by phospholipid bilayers that represent an energy barrier for permeating molecules. Crossing this energy barrier is assumed to be a singular event, and permeation has traditionally been described as a first-order kinetic process, proportional only to the concentration gradient of the permeating substance. For a given membrane composition, permeability was believed to be a unique property dependent only on the permeating molecule itself. We provide experimental evidence that this long-held view might not be entirely correct. Liposomes were used in copermeation experiments with a fluorescent probe, where simultaneous permeation of two substances occurred over a single phospholipid bilayer. Using an assay of six commonly prescribed drugs, we have found that the presence of a copermeant can either enhance or suppress the permeation rate of the probe molecule, often more than 2-fold in each direction. This can have significant consequences for the pharmacokinetics and bioavailability of commonly prescribed drugs when used in combination and provide new insight into so-far unexplained drug-drug interactions as well as changing the perspective on how new drug candidates are evaluated and tested.
- MeSH
- buněčná membrána metabolismus MeSH
- fluorescenční barviva farmakokinetika chemie MeSH
- fosfolipidy chemie MeSH
- léky na předpis farmakokinetika chemie MeSH
- lidé MeSH
- lipidové dvojvrstvy metabolismus MeSH
- liposomy * chemie MeSH
- permeabilita MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Self-assembled bilayer structures such as those produced from amphiphilic block copolymers (polymersomes) are potentially useful in a wide array of applications including the production of artificial cells and organelles, nanoreactors, and delivery systems. These constructs are of important fundamental interest, and they are also frequently considered toward advances in bionanotechnology and nanomedicine. In this framework, membrane permeability is perhaps the most important property of such functional materials. Having in mind these considerations, we herein report the manufacturing of intrinsically permeable polymersomes produced using block copolymers comprising poly[2-(diisopropylamino)-ethyl methacrylate] (PDPA) as the hydrophobic segment. Although being water insoluble at pH 7.4, its pKa(PDPA) ∼ 6.8 leads to the presence of a fraction of protonated amino groups close to the physiological pH, thus conducting the formation of relatively swollen hydrophobic segments. Rhodamine B-loaded vesicles demonstrated that this feature confers inherent permeability to the polymeric membrane, which can still be modulated to some extent by the solution pH. Indeed, even at higher pH values where the PDPA chains are fully deprotonated, the experiments demonstrate that the membranes remain permeable. While membrane permeability can be, for instance, regulated by introducing membrane proteins and DNA nanopores, examples of membrane-forming polymers with intrinsic permeability have been seldom reported so far, and the possibility to regulate the flow of chemicals in these compartments by tuning block copolymer features and ambient conditions is of due relevance. The permeable nature of PDPA membranes possibly applies to a wide array of small molecules, and these findings can in principle be translocated to a variety of disparate bio-related applications.
Encapsulation into liposomes is a formulation strategy that can improve efficacy and reduce side effects of active pharmaceutical ingredients (APIs) that exhibit poor biodistribution or pharmacokinetics when administered alone. However, many APIs are unsuitable for liposomal formulations intended for parenteral administration due to their inherent physicochemical properties─lipid bilayer permeability and water-lipid equilibrium partitioning coefficient. Too high permeability results in premature leakage from liposomes, while too low permeability means the API is not able to pass across biological barriers. There are several options for solving this issue: (i) change of the lipid bilayer composition, (ii) addition of a permeability enhancer, or (iii) modification of the chemical structure of the API to design a prodrug. The latter approach was taken in the present work, and the effect of small changes in the molecular structure of the API on its permeation rate across a lipidic bilayer was systematically explored utilizing computer simulations. An in silico methodology for prodrug design based on the COSMOperm approach has been proposed and applied to four APIs (abiraterone, cytarabine, 5-fluorouracil, and paliperidone). It is shown that the addition of aliphatic hydrocarbon chains via ester or amide bonds can render the molecule more lipophilic and increase its permeability by approximately 1 order of magnitude for each 2 carbon atoms added, while the formation of fructose adducts can provide a more hydrophilic character to the molecule and reduce its lipid partitioning. While partitioning was found to depend only on the size and type of the added group, permeability was found to depend also on the added group location. Overall, it has been shown that both permeability and lipid partitioning coefficient can be systematically shifted into the desired liposome formulability window by appropriate group contributions to the parental drug. This can significantly increase the portfolio of APIs for which liposome or lipid nanoparticle formulations become feasible.
Testy membránové permeability patří společně s testy metabolické stability a stanovením rozpustnosti mezi základní pilíře časných fází vývoje nových léčiv. Pro většinu terapeutických indikací je potřeba, aby látka na své cestě k cílové tkání, receptoru, enzymu překonala i několik biologických bariér, aniž by se přitom extenzivně biotransformovala. K vyšetřování permeability je k dispozici řada nástrojů, své nezastupitelné místo zde mají buněčné testy. Nejčastěji se používají zjednodušené dvoukompartmentové systémy, tzv. „Transwelly“, kde je na pomezí obou oddílů nosič s umělou lipidovou dvouvrstvou nebo monovrstvou těsně přiléhajících buněk. K dispozici jsou i mnohem sofistikovanější nástroje, kokultury více buněčných typů, případně 3D dynamické modely na čipu, jejich širšímu použití však brání časová i finanční náročnost. V základních testovacích cyklech, kde se pracuje s velkým množstvím látek, se proto nejčastěji uplatňuje Caco-2 nebo MDCK test.
Membrane permeability assays – together with metabolic stability and solubility assays – belong to the essential tools of early drug discovery process. In most therapeutic indications, a drug needs to pass several biological barriers to exert its desired effect to a target tissue, receptor, enzyme, without significant decay. There are numerous models available allowing us to evaluate compounds permeability, with cellular assays being particularly useful. Most frequently, these assays are based on a „Transwell“ system, where two compartments are separated by a filter bearing either artificial membrane or a monolayer of tightly connecting cells. More sophisticated permeability assays have been developed during the last decade, e.g., co-cultures of relevant cell types or 3D microfluidics on a chip. However, their high costs and time-consuming preparation prevent their widespread use. In basic drug development screening cycles Caco-2 and MDCK assays remain the gold standard.
Overcoming the skin barrier properties efficiently, temporarily, and safely for successful transdermal drug delivery remains a challenge. We synthesized three series of potential skin permeation enhancers derived from natural amino acid derivatives proline, 4-hydroxyproline, and pyrrolidone carboxylic acid, which is a component of natural moisturizing factor. Permeation studies using in vitro human skin identified dodecyl prolinates with N-acetyl, propionyl, and butyryl chains (Pro2, Pro3, and Pro4, respectively) as potent enhancers for model drugs theophylline and diclofenac. The proline derivatives were generally more active than 4-hydroxyprolines and pyrrolidone carboxylic acid derivatives. Pro2-4 had acceptable in vitro toxicities on 3T3 fibroblast and HaCaT cell lines with IC50 values in tens of μM. Infrared spectroscopy using the human stratum corneum revealed that these enhancers preferentially interacted with the skin barrier lipids and decreased the overall chain order without causing lipid extraction, while their effects on the stratum corneum protein structures were negligible. The impacts of Pro3 and Pro4 on an in vitro transepidermal water loss and skin electrical impedance were fully reversible. Thus, proline derivatives Pro3 and Pro4 have an advantageous combination of high enhancing potency, low cellular toxicity, and reversible action, which is important for their potential in vivo use as the skin barrier would quickly recover after the drug/enhancer administration is terminated.
- MeSH
- aplikace kožní MeSH
- hydroxyprolin metabolismus MeSH
- kožní absorpce * MeSH
- kůže metabolismus MeSH
- kyseliny karboxylové metabolismus MeSH
- léčivé přípravky metabolismus MeSH
- lidé MeSH
- organické látky metabolismus MeSH
- permeabilita MeSH
- prolin * metabolismus MeSH
- pyrrolidinony farmakologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The transverse-axial tubular system (tubular system) of cardiomyocytes plays a key role in excitation-contraction coupling. To determine the area of the tubular membrane in relation to the area of the surface membrane, indirect measurements through the determination of membrane capacitances are currently used in addition to microscopic methods. Unlike existing electrophysiological methods based on an irreversible procedure (osmotic shock), the proposed new approach uses a reversible short-term intermittent increase in the electrical resistance of the extracellular medium. The resulting increase in the lumen resistance of the tubular system makes it possible to determine separate capacitances of the tubular and surface membranes. Based on the analysis of the time course of the capacitive current, computational relations were derived to quantify the elements of the electrical equivalent circuit of the measured cardiomyocyte including both capacitances. The exposition to isotonic low-conductivity sucrose solution is reversible which is the main advantage of the proposed approach allowing repetitive measurements on the same cell under control and sucrose solutions. Experiments on rat ventricular cardiomyocytes (n = 20) resulted in the surface and tubular capacitance values implying the fraction of tubular capacitance/area of 0.327 ± 0.018. We conclude that the newly proposed method provides results comparable to the data obtained by the currently used detubulation method and, in addition, by being reversible, allows repeated evaluation of surface and tubular membrane parameters on the same cell.
Propofol has been shown to against intestinal reperfusion injury when treated either before or after ischemia, during which mast cell could be activated. The aim of this study was to evaluate the role of propofol in restoring the intestinal epithelial cells integrity disrupted by mast cell activation or the released tryptase after activation in vitro. We investigated the effect of: (1) tryptase on Caco-2 monolayers in the presence of PAR-2 inhibitor or propofol, (2) mast cell degranulation in a Caco-2/LAD-2 co-culture model in the presence of propofol, and (3) propofol on mast cell degranulation. Epithelial integrity was detected using transepithelial resistance (TER) and permeability to fluorescein isothiocyanate (FITC)-dextran (the apparent permeability coefficient, Papp). The expression of junctional proteins zonula occludens-1 (ZO-1/TJP1) and occludin were determined using western blot analysis and immunofluorescence microscopy. The intracellular levels of reactive oxidative species (ROS) and Ca2+ were measured using flow cytometry. Tryptase directly enhanced intestinal barrier permeability as demonstrated by significant reductions in TER, ZO-1, and occludin protein expression and concomitant increases in Papp. The intestinal barrier integrity was restored by PAR-2 inhibitor but not by propofol. Meanwhile, mast cell degranulation resulted in epithelial integrity disruption in the Caco-2/LAD-2 co-culture model, which was dramatically attenuated by propofol. Mast cell degranulation caused significant increases in intracellular ROS and Ca(2+) levels, which were blocked by propofol and NAC. Propofol pretreatment can inhibit mast cell activation via ROS/Ca(2+) and restore the intestinal barrier integrity induced by mast cell activation, instead of by tryptase.
- MeSH
- Caco-2 buňky MeSH
- degranulace buněk MeSH
- epitelové buňky metabolismus MeSH
- lidé MeSH
- mastocyty metabolismus MeSH
- okludin metabolismus MeSH
- permeabilita MeSH
- propofol * farmakologie MeSH
- reaktivní formy kyslíku metabolismus MeSH
- střevní sliznice metabolismus MeSH
- tryptasy metabolismus farmakologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
