Tuning the predictive capacity of the PAMPA-BBB model

The piper at the gates of brain: A systematic review of surface modification strategies on lipid nanoparticles to overcome the Blood-Brain-Barrier

The Blood-Brain Barrier (BBB) significantly impedes drug delivery to the central nervous system. Nanotechnology, especially surface-functionalized lipid nanoparticles, offers innovative approaches to overcome this barrier. However, choosing an effective functionalization strategy is challenging due to the lack of detailed comparative analysis in current literature. Our systematic review examined various functionalization strategies and their impact on BBB permeability from 2041 identified articles, of which 80 were included for data extraction. Peptides were the most common modification (18) followed by mixed strategies (12) proteins (9), antibodies (7), and other strategies (8). Interestingly, 26 studies showed BBB penetration with unmodified or modified nanoparticles using commonly applied strategies such as PEGylation or surfactant addition. Statistical analysis across 42 studies showed correlation between higher in vivo permeation improvements and nanoparticle type, size, and functionalization category. The highest ratios were found for nanostructured lipid carriers or biomimetic systems, in studies with particle sizes under 150 nm, and in those applying mixed functionalization strategies. The interstudy heterogeneity we observed highlights the importance of adopting standardized evaluation protocols to enhance comparability. Our systematic review aims to provide a comparative insight and identify future research directions in the development of more effective lipid nanoparticle systems for drug delivery to the brain to help improve the treatment of neurological and psychiatric disorders and brain tumours.

Extending the limitations in the prediction of PAMPA permeability with machine learning algorithms

Gastrointestinal absorption is a key factor amongst the ADME-related (absorption, distribution, metabolism and excretion) pharmacokinetic properties; therefore, it has a major role in drug discovery and drug safety determinations. The Parallel Artificial Membrane Permeability Assay (PAMPA) can be considered as the most popular and well-known screening assay for the measurement of gastrointestinal absorption. Our study provides quantitative structure-property relationship (QSPR) models based on experimental PAMPA permeability data for almost four hundred diverse molecules, which is a great extension of the applicability of the models in the chemical space. Two- and three-dimensional molecular descriptors were applied for the model building in every case. We have compared the performance of a classical partial least squares regression (PLS) model with two major machine learning algorithms: artificial neural networks (ANN) and support vector machine (SVM). Due to the applied gradient pH in the experiments, we have calculated the descriptors for the model building at pH values of 7.4 and 6.5, and compared the effect of pH on the performance of the models. After a complex validation protocol, the best model had an R2=0.91 for the training set, and R2= 0.84 for the external test set. The developed models are capable for the robust and fast prediction of new compounds with an excellent accuracy compared to the previous QSPR models.

Peripheral modulation of antidepressant targets MAO-B and GABAAR by harmol induces mitohormesis and delays aging in preclinical models

Reversible and sub-lethal stresses to the mitochondria elicit a program of compensatory responses that ultimately improve mitochondrial function, a conserved anti-aging mechanism termed mitohormesis. Here, we show that harmol, a member of the beta-carbolines family with anti-depressant properties, improves mitochondrial function and metabolic parameters, and extends healthspan. Treatment with harmol induces a transient mitochondrial depolarization, a strong mitophagy response, and the AMPK compensatory pathway both in cultured C2C12 myotubes and in male mouse liver, brown adipose tissue and muscle, even though harmol crosses poorly the blood-brain barrier. Mechanistically, simultaneous modulation of the targets of harmol monoamine-oxidase B and GABA-A receptor reproduces harmol-induced mitochondrial improvements. Diet-induced pre-diabetic male mice improve their glucose tolerance, liver steatosis and insulin sensitivity after treatment with harmol. Harmol or a combination of monoamine oxidase B and GABA-A receptor modulators extend the lifespan of hermaphrodite Caenorhabditis elegans or female Drosophila melanogaster. Finally, two-year-old male and female mice treated with harmol exhibit delayed frailty onset with improved glycemia, exercise performance and strength. Our results reveal that peripheral targeting of monoamine oxidase B and GABA-A receptor, common antidepressant targets, extends healthspan through mitohormesis.

Natural Lipid Extracts as an Artificial Membrane for Drug Permeability Assay: In Vitro and In Silico Characterization

In vitro non-cellular permeability models such as the parallel artificial membrane permeability assay (PAMPA) are widely applied tools for early-phase drug candidate screening. In addition to the commonly used porcine brain polar lipid extract for modeling the blood–brain barrier’s permeability, the total and polar fractions of bovine heart and liver lipid extracts were investigated in the PAMPA model by measuring the permeability of 32 diverse drugs. The zeta potential of the lipid extracts and the net charge of their glycerophospholipid components were also determined. Physicochemical parameters of the 32 compounds were calculated using three independent forms of software (Marvin Sketch, RDKit, and ACD/Percepta). The relationship between the lipid-specific permeabilities and the physicochemical descriptors of the compounds was investigated using linear correlation, Spearman correlation, and PCA analysis. While the results showed only subtle differences between total and polar lipids, permeability through liver lipids highly differed from that of the heart or brain lipid-based models. Correlations between the in silico descriptors (e.g., number of amide bonds, heteroatoms, and aromatic heterocycles, accessible surface area, and H-bond acceptor–donor balance) of drug molecules and permeability values were also found, which provides support for understanding tissue-specific permeability.

Effect of liposomal formulation of ascorbic acid on corneal permeability

Ascorbic acid (AA) has a pivotal role in corneal wound healing via stimulating the biosynthesis of highly organized extracellular matrix components, but its rapid degradation and low corneal permeability limits its therapeutic effects. In this paper, we present the pharmacokinetic properties of a liposomal-based formulation of AA in terms of corneal permeation. Chemical stability, shelf-life, and drug release rate of lyophilized liposome (AA-LLipo) formulation was determined in comparison to free-form of AA solution using high-performance liquid chromatography (HPLC) and rapid equilibrium dialysis. In vitro transcorneal permeability was studied using a parallel artificial membrane permeability assay (PAMPA). Ex vivo permeation was examined on AA-LLipo-treated porcine cornea by determining the AA content on the ocular surface, in the cornea as well as in the aqueous humor using HPLC, and by Raman-mapping visualizing the AA-distribution. Our results showed that the liposomal formulation improved the chemical stability of AA, while drug release was observed with the same kinetic efficiency as from the free-form of AA solution. Both corneal-PAMPA and porcine corneal permeability studies showed that AA-LLipo markedly improved the corneal absorption kinetics of AA, thus, increasing the AA content in the cornea and aqueous humor. AA-LLipo formulation could potentially increase the bioavailability of AA in corneal tissues.

Synthesis, Pharmacokinetic Characterization and Antioxidant Capacity of Carotenoid Succinates and Their Melatonin Conjugates

Carotenoid succinates were synthesized from hydroxy carotenoids and were coupled to a commercially available derivative of melatonin via amide bond for producing more powerful anti-oxidants and yet new hybrid lipophilic bifunctional molecules with additional therapeutic effects. The coupling reactions produced conjugates in acceptable to good yields. Succinylation increased the water solubility of the carotenoids, while the conjugation with melatonin resulted in more lipophilic derivatives. The conjugates showed self-assembly in aqueous medium and yielded relatively stable colloidal solutions in phosphate-buffered saline. Antioxidant behavior was measured with ABTS and the FRAP methods for the carotenoids, the carotenoid succinates, and the conjugates with melatonin. A strong dependence on the quality of the solvent was observed. TEAC values of the new derivatives in phosphate-buffered saline were found to be comparable to or higher than those of parent carotenoids, however, synergism was observed only in FRAP assays.

In vitro and in silico evaluation of Ononis isoflavonoids as molecules targeting the central nervous system

Isoflavonoids with various structural elements show a promising potential effect on central nervous system activities. Despite their favorable medicinal properties, the pharmacokinetic characteristics of this thoroughly investigated group of natural phenolics have only been described to a limited extent. Regarding the lack of information about the BBB permeability of isoflavones, isoflavanones, and pterocarpans found in Ononis species, the aim of our study was to investigate their physico-chemical properties influencing their absorption and distribution. Furthermore, we aimed to characterize the possible MAO-B inhibiting features of Ononis isoflavonoids in silico. Octanol-water partitioning and BBB-PAMPA permeability of formononetin, calycosin D, onogenin, sativanone, medicarpin and maackiain were assessed for the first time in our study. The log P values ranged from 2.21 to 3.03 and log D^7.4 values from 2.48 to 3.03, respectively, indicating optimal polarity for BBB permeation. The results of PAMPA-BBB expressed as log P_e values fell between -5.60 and -4.45, predicting their good permeation capability as well. The effective permeability values showed structure-dependent differences, indicating that the pterocarpan type skeleton was the most preferred type, followed by isoflavanones, then isoflavones. The methoxy or methylenedioxy substitution of the same skeleton did not influence the permeability significantly, contrary to an additional hydroxyl group. Membrane retention showed a similar structure dependent pattern to that of effective permeability, ranging from 16% to 70%. For the identification of volumes of chemical space related to particular biological activities the ChemGPS-NP framework was used. The MAO-B inhibitory potency and selectivity were also predicted and validated. Based on our results, MAO-B inhibitory potency could be predicted with good precision, but in the case of selectivity, only the direction could be concluded (favors MAO-B or MAO-A), not the magnitude. Our finding reflects that Ononis isoflavonoid aglycones show an excellent fit with the suggested parameters for BBB permeability and this is the first study to confirm the highly favorable position of these natural products for MAO-B inhibition.

Design, Synthesis, and Evaluation of Novel 2H-Benzo[b][1,4]thiazin-3(4H)-one Derivatives as New Acetylcholinesterase Inhibitors

Alzheimer’s disease (AD) is a slowly progressive neurodegenerative disease that causes dementia in people aged 65 and over. In the present study, a series of thiadiazole hybrid compounds with benzothiazine derivatives as acetylcholinesterase inhibitors were developed and evaluated for their biological activity. The AChE and BChE inhibition potentials of all compounds were evaluated by using the in vitro Ellman method. The biological evaluation showed that compounds 3i and 3j displayed significant inhibitory activity against AChE. Compounds 3i and 3j showed IC₅₀ values of 0.027 µM and 0.025 µM against AChE, respectively. The reference drug donepezil (IC₅₀ = 0.021 µM) also showed significant inhibition against AChE. Further docking simulation also revealed that these compounds (3i and 3j) interacted with the active site of the enzyme similarly to donepezil. The antioxidant study revealed that compounds 3i and 3j exhibited greater antioxidant effects. An in vitro blood–brain barrier permeability study showed that compounds 3i and 3j are promising compounds against AD. The cytotoxicity study of compounds 3i and 3j showed non-cytotoxic with an IC₅₀ value of 98.29 ± 3.98 µM and 159.68 ± 5.53 µM against NIH/3T3 cells, respectively.

New In Vitro Methodology for Kinetics Distribution Prediction in the Brain. An Additional Step towards an Animal-Free Approach

Simple Summary

The prevalence of neurological disorders in humans is rising year after year. This fact necessitates the development of new drugs for treating these pathologies. Traditionally, drugs have been tested in animals prior to use in human experiments; however, the use of animals in experimentation must be controlled and as low as possible. Because of that, here we proposed a new in vitro approach with which the access and distribution of drugs into the brain can be evaluated without using/killing any animals.

Abstract

The development of new drugs or formulations for central nervous system (CNS) diseases is a complex pharmacologic and pharmacokinetic process; it is important to evaluate their access to the CNS through the blood–brain barrier (BBB) and their distribution once they have acceded to the brain. The gold standard tool for obtaining this information is the animal microdialysis technique; however, according to 3Rs principles, it would be better to have an “animal-free” alternative technique. Because of that, the purpose of this work was to develop a new formulation to substitute the brain homogenate in the in vitro tests used for the prediction of a drug’s distribution in the brain. Fresh eggs have been used to prepare an emulsion with the same proportion in proteins and lipids as a human brain; this emulsion has proved to be able to predict both the unbound fraction of drug in the brain (f_u,brain) and the apparent volume of distribution in the brain (V_u,brain) when tested in in vitro permeability tests. The new formulation could be used as a screening tool; only the drugs with a proper in vitro distribution would pass to microdialysis studies, contributing to the refinement, reduction and replacement of animals in research.

A review of pregnancy-induced changes in opioid pharmacokinetics, placental transfer, and fetal exposure: Towards fetomaternal physiologically-based pharmacokinetic modeling to improve the treatment of neonatal opioid withdrawal syndrome

Physiologically-based pharmacokinetic (PBPK) modeling has emerged as a useful tool to study pharmacokinetics (PK) in special populations, such as pregnant women, fetuses, and newborns, where practical hurdles severely limit the study of drug behavior. PK in pregnant women is variable and everchanging, differing greatly from that in their nonpregnant female and male counterparts typically enrolled in clinical trials. PBPK models can accommodate pregnancy-induced physiological and metabolic changes, thereby providing mechanistic insights into maternal drug disposition and fetal exposure. Fueled by the soaring opioid epidemic in the United States, opioid use during pregnancy continues to rise, leading to an increased incidence of neonatal opioid withdrawal syndrome (NOWS). The severity of NOWS is influenced by a complex interplay of extrinsic and intrinsic factors, and varies substantially between newborns, but the extent of prenatal opioid exposure is likely the primary driver. Fetomaternal PBPK modeling is an attractive approach to predict in utero opioid exposure. To facilitate the development of fetomaternal PBPK models of opioids, this review provides a detailed overview of pregnancy-induced changes affecting the PK of commonly used opioids during gestation. Moreover, the placental transfer of these opioids is described, along with their disposition in the fetus. Lastly, the implementation of these factors into PBPK models is discussed. Fetomaternal PBPK modeling of opioids is expected to provide improved insights in fetal opioid exposure, which allows for prediction of postnatal NOWS severity, thereby opening the way for precision postnatal treatment of these vulnerable infants.

Pharmacokinetics-Driven Evaluation of the Antioxidant Activity of Curcuminoids and Their Major Reduced Metabolites-A Medicinal Chemistry Approach

Curcuminoids are the main bioactive components of the well-known Asian spice and traditional medicine turmeric. Curcuminoids have poor chemical stability and bioavailability; in vivo they are rapidly metabolized to a set of bioreduced derivatives and/or glucuronide and sulfate conjugates. The reduced curcuminoid metabolites were also reported to exert various bioactivities in vitro and in vivo. In this work, we aimed to perform a comparative evaluation of curcuminoids and their hydrogenated metabolites from a medicinal chemistry point of view, by determining a set of key pharmacokinetic parameters and evaluating antioxidant potential in relation to such properties.Reduced metabolites were prepared from curcumin and demethoxycurcumin through continuous-flow hydrogenation. As selected pharmacokinetic parameters, kinetic solubility, chemical stability, metabolic stability in human liver microsomes, and parallel artificial membrane permeability assay (PAMPA)-based gastrointestinal and blood-brain barrier permeability were determined. Experimentally determined logP for hydrocurcumins in octanol-water and toluene-water systems provided valuable data on the tendency for intramolecular hydrogen bonding by these compounds. Drug likeness of the compounds were further evaluated by a in silico calculations. Antioxidant properties in diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and oxygen radical absorbance capacity (ORAC) assays were comparatively evaluated through the determination of ligand lipophilic efficiency (LLE). Our results showed dramatically increased water solubility and chemical stability for the reduced metabolites as compared to their corresponding parent compound. Hexahydrocurcumin was found the best candidate for drug development based on a complex pharmacokinetical comparison and high LLE values for its antioxidant properties. Development of tetrahydrocurcumin and tetrahydro-demethoxycurcumin would be limited by their very poor metabolic stability, therefore such an effort would rely on formulations bypassing first-pass metabolism.

First Contact: 7-Phenyl-2-Aminoquinolines, Potent and Selective Neuronal Nitric Oxide Synthase Inhibitors That Target an Isoform-Specific Aspartate

Inhibition of neuronal nitric oxide synthase (nNOS), an enzyme implicated in neurodegenerative disorders, is an attractive strategy for treating or preventing these diseases. We previously developed several classes of 2-aminoquinoline-based nNOS inhibitors, but these compounds had drawbacks including off-target promiscuity, low activity against human nNOS, and only modest selectivity for nNOS over related enzymes. In this study, we synthesized new nNOS inhibitors based on 7-phenyl-2-aminoquinoline and assayed them against rat and human nNOS, human eNOS, and murine and (in some cases) human iNOS. Compounds with a meta-relationship between the aminoquinoline and a positively charged tail moiety were potent and had up to nearly 900-fold selectivity for human nNOS over human eNOS. X-ray crystallography indicates that the amino groups of some compounds occupy a water-filled pocket surrounding an nNOS-specific aspartate residue (absent in eNOS). This interaction was confirmed by mutagenesis studies, making 7-phenyl-2-aminoquinolines the first aminoquinolines to interact with this residue.

In Silico Studies on Triterpenoid Saponins Permeation through the Blood-Brain Barrier Combined with Postmortem Research on the Brain Tissues of Mice Affected by Astragaloside IV Administration

As the number of central nervous system (CNS) drug candidates is constantly growing, there is a strong need for precise a priori prediction of whether an administered compound is able to cross the blood–brain barrier (BBB). The aim of this study was to evaluate the ability to cross the BBB of triterpenoid saponins occurring in Astragalus mongholicus roots. The research was carried out using in silico methods combined with postmortem studies on the brain tissues of mice treated with isolated astragaloside IV (AIV). Firstly, to estimate the ability to cross the BBB by the tested saponins, new quantitative structure–activity relationship (QSAR) models were established. The reliability and predictability of the model based on the values of the blood–brain barrier penetration descriptor (logBB), the difference between the n-octanol/water and cyclohexane/water logP (ΔlogP), the logarithm of n-octanol/water partition coefficient (logP_ow), and the excess molar refraction (E) were both confirmed using the applicability domain (AD). The critical leverage value h* was found to be 0.128. The relationships between the standardized residuals and the leverages were investigated here. The application of an in vitro acetylcholinesterase-inhibition test showed that AIV can be recognized as the strongest inhibitor among the tested compounds. Therefore, it was isolated for the postmortem studies on brain tissues and blood using semi-preparative HPLC with the mobile phase composed of water, methanol, and ethyl acetate (1.7:2.1:16.2 v/v/v). The results of the postmortem studies on the brain tissues show a regular dependence of the final concentration of AIV in the analyzed brain samples of animals treated with 12.5 and 25 mg/kg b.w. of AIV (0.00012299 and 0.0002306 mg, respectively, per one brain). Moreover, the AIV logBB value was experimentally determined and found to be equal to 0.49 ± 0.03.

To Pass or Not To Pass: Predicting the Blood-Brain Barrier Permeability with the 3D-RISM-KH Molecular Solvation Theory

Predicting the ability of chemical species to cross the blood-brain barrier (BBB) is an active field of research for development and mechanistic understanding in the pharmaceutical industry. Here, we report the BBB permeability of a large data set of compounds by incorporating molecular solvation energy descriptors computed by the 3D-RISM-KH molecular solvation theory. We have been able to show, for the first time, that the computed excess chemical potential in different solvents can be successfully used to predict permeability of compounds in a binary manner (yes/no) via a minimum-descriptor-based model. Our findings successfully combine the molecular solvation theory with the machine learning approach to address one of the most daunting challenges in predictive structure-activity relationship modeling. The workflow presented in this work is simple enough to be used by nonexperts with ease.

Polyphenol Microbial Metabolites Exhibit Gut and Blood⁻Brain Barrier Permeability and Protect Murine Microglia against LPS-Induced Inflammation

Increasing evidence supports the beneficial effects of polyphenol-rich diets, including the traditional Mediterranean diet, for the management of cardiovascular disease, obesity and neurodegenerative diseases. However, a common concern when discussing the protective effects of polyphenol-rich diets against diseases is whether these compounds are present in systemic circulation in their intact/parent forms in order to exert their beneficial effects in vivo. Here, we explore two common classes of dietary polyphenols, namely isoflavones and lignans, and their gut microbial-derived metabolites for gut and blood-brain barrier predicted permeability, as well as protection against neuroinflammatory stimuli in murine BV-2 microglia. Polyphenol microbial metabolites (PMMs) generally showed greater permeability through artificial gut and blood-brain barriers compared to their parent compounds. The parent polyphenols and their corresponding PMMs were evaluated for protective effects against lipopolysaccharide-induced inflammation in BV-2 microglia. The lignan-derived PMMs, equol and enterolactone, exhibited protective effects against nitric oxide production, as well as against pro-inflammatory cytokines (IL-6 and TNF-α) in BV-2 microglia. Therefore, PMMs may contribute, in large part, to the beneficial effects attributed to polyphenol-rich diets, further supporting the important role of gut microbiota in human health and disease prevention.

Neuropharmacokinetics: a bridging tool between CNS drug development and therapeutic outcome

WHO classified neurological disorders to be among 6.3% of the global disease burden. Among the most central aspects of CNS drug development is the ability of novel molecules to cross the blood-brain barrier (BBB) to reach the target site over a desired time period for therapeutic action. Based on various aspects, brain pharmacokinetics is considered to be one of the foremost perspectives for the higher attrition rate of CNS biologics. Although drug traits are important, the BBB and blood-cerebrospinal fluid barrier together with transporters become the mechanistic approach behind CNS drug delivery. The present review emphasizes neuropharmacokinetic parameters, their importance, an assessment approach and the vast effect of transporters to brain drug distribution for CNS drug discovery.

Optimization of Blood-Brain Barrier Permeability with Potent and Selective Human Neuronal Nitric Oxide Synthase Inhibitors Having a 2-Aminopyridine Scaffold

Effective delivery of therapeutic drugs into the human brain is one of the most challenging tasks in central nervous system drug development because of the blood-brain barrier (BBB). To overcome the BBB, both passive permeability and efflux transporter liability of a compound must be addressed. Herein, we report our optimization related to BBB penetration of neuronal nitric oxide synthase (nNOS) inhibitors toward the development of new drugs for neurodegenerative diseases. Various approaches, including enhancing lipophilicity and rigidity of new inhibitors and modulating the p K_a of amino groups, have been employed. In addition to determining inhibitor potency and selectivity, crystal structures of most newly designed compounds complexed to various nitric oxide synthase isoforms have been determined. We have discovered a new analogue (21), which exhibits not only excellent potency ( K_i < 30 nM) in nNOS inhibition but also a significantly low P-glycoprotein and breast-cancer-resistant protein substrate liability as indicated by an efflux ratio of 0.8 in the Caco-2 bidirectional assay.

A new approach to examining the extraction process of Zhishi and Zhiqiao considering the synergistic effect of complex mixtures by PAMPA

Zhishi (ZS) and Zhiqiao (ZQ) are two important traditional Chinese medicines (TCMs) that exert various pharmacological functions due to their active ingredients. However, the oral absorption of these ingredients requires further study. At the early drug discovery stage, the high-throughput parallel artificial membrane permeability assay (PAMPA) is one of the most frequently used to predict transcellular passive absorption in in-vitro models. This study aims to establish a new approach to examine an optimal extraction process that can take into account not only the concentration of active ingredients but also the overall absorption properties of the mixtures extracted from TCMs. A high-performance liquid chromatography triple-quadrupole mass spectrometry (HPLC-QqQ-MS/MS) method was validated for the determination of the effective permeability value (P_e) applied to the above experimental medium. The PAMPA experiment showed that certain active ingredients such as diosmin, rhoifolin, eriocitrin, narirutin, naringin, hesperidin and neohesperidin were not detected in the permeability assay of mono-constituents but were well detected and achieved a better absorption in the permeability assay of the mixture, indicating that certain unknown ingredients may act as cosolvents to improve the solubility or permeability of other ingredients. Furthermore, solid phase extraction (SPE) as an enrichment and purification process enhances absorption. In the present study, a novel in vitro approach was developed to decipher the potential role of TCMs in global absorption, and the extraction process for complex TCMs was described and systematically optimized.

How To Design for a Tailored Subcellular Distribution of Systemic Agrochemicals in Plant Tissues

Foliar-applied systemic agrochemicals require entrance into the plant vascular system or into specific subcellular compartments to reach their target in planta or to be imbibed by piercing/sucking pests. An inappropriate subcellular localization, like accumulation of aphicides in vacuoles, might lower the compound's efficiency due to reduced exposure to the target. Permeabilities and mass distributions of 16 compounds covering a broad range of properties were measured across a pH gradient in a PAMPA ("parallel artificial membrane permeability assay") system, providing experimental evidence for ion trapping of acids and bases in basic and acidic compartments, respectively. The results validated a predictive model which was then expanded to simulate a standardized plant cell (cytosol and vacuole) with a vascular system (phloem and xylem). This approach underlined that the absolute mass distribution across aqueous phases is defined by membrane retention, whereas the relative mass distribution is determined by the species (neutral, acidic, basic) of compounds. These processes depend largely on p K_a and log  K_ow of the test compounds, which subsequently determine the partitioning of the substances in plant cell compartments. The validated model can be used as a tool in agrochemistry research to tailor the subcellular distribution by chemistry design and to interpret biology results.

From the Cover: In Vitro and In Vivo Blood-Brain Barrier Penetration Studies with the Novel Cyanide Antidote Candidate Dimethyl Trisulfide in Mice

Recent in vitro and in vivo studies highlight the strong potential of dimethyl trisulfide (DMTS) as an antidote for cyanide (CN) intoxication. Due to its high oxygen demand, the brain is one of the main target organs of CN. The blood-brain barrier (BBB) regulates the uptake of molecules into the brain. In the literature, there is no data about the ability of DMTS to penetrate the BBB. Therefore, our aim was to test the in vitro BBB penetration of DMTS and its in vivo pharmacokinetics in blood and brain. The in vitro BBB penetration of DMTS was measured by using a parallel artificial membrane permeability assay (BBB-PAMPA), and a triple BBB co-culture model. The pharmacokinetics was investigated in a mouse model by following the DMTS concentration in blood and brain at regular time intervals following intramuscular administration. DMTS showed high penetrability in both in vitro systems (apparent permeability coefficients: BBB-PAMPA 11.8 × 10-6 cm/s; cell culture 158 × 10-6 cm/s) without causing cell toxicity and leaving the cellular barrier intact. DMTS immediately absorbed into the blood after the intramuscular injection (5 min), and rapidly penetrated the brain of mice (10 min). In addition to the observed passive diffusion in the in vitro studies, the contribution of facilitated and/or active transport to the measured high permeability of DMTS in the pharmacokinetic studies can be hypothesized. Earlier investigations demonstrating the antidotal efficacy of DMTS against CN together with the present results highlight the promise of DMTS as a brain-protective CN antidote.

Drug permeability profiling using cell-free permeation tools: Overview and applications

Cell-free permeation systems are gaining interest in drug discovery and development as tools to obtain a reliable prediction of passive intestinal absorption without the disadvantages associated with cell- or tissue-based permeability profiling. Depending on the composition of the barrier, cell-free permeation systems are classified into two classes including (i) biomimetic barriers which are constructed from (phospho)lipids and (ii) non-biomimetic barriers containing dialysis membranes. This review provides an overview of the currently available cell-free permeation systems including Parallel Artificial Membrane Permeability Assay (PAMPA), Phospholipid Vesicle-based Permeation Assay (PVPA), Permeapad®, and artificial membrane based systems (e.g. the artificial membrane insert system (AMI-system)) in terms of their barrier composition as well as their predictive capacity in relation to well-characterized intestinal permeation systems. Given the potential loss of integrity of cell-based permeation barriers in the presence of food components or pharmaceutical excipients, the superior robustness of cell-free barriers makes them suitable for the combined dissolution/permeation evaluation of formulations. While cell-free permeation systems are mostly applied for exploring intestinal absorption, they can also be used to evaluate non-oral drug delivery by adjusting the composition of the membrane.

Metallomics for Alzheimer's disease treatment: Use of new generation of chelators combining metal-cation binding and transport properties

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting tens of million people. Currently marketed drugs have limited therapeutic efficacy and only slowing down the neurodegenerative process. Interestingly, it has been suggested that biometal cations in the amyloid beta (Aβ) aggregate deposits contribute to neurotoxicity and degenerative changes in AD. Thus, chelation therapy could represent novel mode of therapeutic intervention. Here we describe the features of chelators with therapeutically relevant mechanism of action. We have found that the tested compounds effectively reduce the toxicity of exogenous Aβ and suppress its endogenous production as well as decrease oxidative stress. Cholyl hydrazones were found to be the most active compounds. In summary, our data show that cation complexation, together with improving transport efficacy may represent basis for eventual treatment strategy in AD.

Improvement of Cell Permeability of Human Neuronal Nitric Oxide Synthase Inhibitors Using Potent and Selective 2-Aminopyridine-Based Scaffolds with a Fluorobenzene Linker

Inhibition of neuronal nitric oxide synthase (nNOS) is a promising therapeutic approach to treat neurodegenerative diseases. Recently, we have achieved considerable progress in improving the potency and isoform selectivity of human nNOS inhibitors bearing a 2-aminopyridine scaffold. However, these inhibitors still suffered from too low cell membrane permeability to enter into CNS drug development. We report herein our studies to improve permeability of nNOS inhibitors as measured by both PAMPA-BBB and Caco-2 assays. The most permeable compound (12) in this study still preserves excellent potency with human nNOS (K_i = 30 nM) and very high selectivity over other NOS isoforms, especially human eNOS (hnNOS/heNOS = 2799, the highest hnNOS/heNOS ratio we have obtained to date). X-ray crystallographic analysis reveals that 12 adopts a similar binding mode in both rat and human nNOS, in which the 2-aminopyridine and the fluorobenzene linker form crucial hydrogen bonds with glutamate and tyrosine residues, respectively.

Simplified strigolactams as potent analogues of strigolactones for the seed germination induction of Orobanche cumana Wallr

BACKGROUND

Strigolactones play an important role in the rhizosphere as signalling molecules stimulating the seed germination of parasitic weed seeds and hyphal branching of arbuscular micorrhiza, and also act as hormones in plant roots and shoots. Strigolactone derivatives, e.g. strigolactams, could be used as suicidal germination inducers in the absence of a host crop for the decontamination of land infested with parasitic weed seeds.

RESULTS

We report the stereoselective synthesis of novel strigolactams, together with some of their critical physicochemical properties, such as water solubility, hydrolytic stability, as well as their short soil persistence. In addition, we show that such strigolactams are potent germination stimulants of O. cumana parasitic weed seeds and do not affect the seed germination and the root growth of sunflower.

CONCLUSIONS

The novel strigolactam derivatives described here compare favourably with the corresponding GR-28 strigolactones in terms of biological activity and physicochemical properties. However, we believe strigolactone and strigolactam derivatives require further structural optimisation to improve their soil persistence to demonstrate a potential for agronomical applications. © 2016 Society of Chemical Industry.

In vitro screening of nanomedicines through the blood brain barrier: A critical review

The blood-brain barrier accounts for the high attrition rate of the treatments of most brain disorders, which therefore remain one of the greatest health-care challenges of the twenty first century. Against this background of hindrance to brain delivery, nanomedicine takes advantage of the assembly at the nanoscale of available biomaterials to provide a delivery platform with potential to raising brain levels of either imaging or therapeutic agents. Nevertheless, to prevent later failure due to ineffective drug levels at the target site, researchers have been endeavoring to develop a battery of in vitro screening procedures that can predict earlier in the drug discovery process the ability of these cutting-edge drug delivery platforms to cross the blood-brain barrier for biomedical purposes. This review provides an in-depth analysis of the currently available in vitro blood-brain barrier models (both cell-based and non-cell-based) with the focus on their suitability for understanding the biological brain distribution of forthcoming nanomedicines. The relationship between experimental factors and underlying physiological assumptions that would ultimately lead to a more predictive capacity of their in vivo performance, and those methods already assayed for the evaluation of the brain distribution of nanomedicines are comprehensively discussed.