Lipid Monolayer on Cell Surface Protein Templates Functional Extracellular Lipid Assembly.

When the ancestors of men moved from aquatic habitats to the drylands, their evolutionary strategy to restrict water loss is to seal the skin surface with lipids. It is unknown how these rigid ceramide-dominated lipids with densely packed chains squeeze through narrow extracellular spaces and how they assemble into their complex multilamellar architecture. Here it is shown that the human corneocyte lipid envelope, a monolayer of ultralong covalently bound lipids on the cell surface protein, templates the functional barrier assembly by partly fluidizing and rearranging the free extracellular lipids in its vicinity during the sculpting of a functional skin lipid barrier. The lipid envelope also maintains the fluidity of the extracellular lipids during mechanical stress. This local lipid fluidization does not compromise the permeability barrier. The results provide new testable hypotheses about epidermal homeostasis and the pathophysiology underlying diseases with impaired lipid binding to corneocytes, such as congenital ichthyosis. In a broader sense, this lipoprotein-mediated fluidization of rigid (sphingo)lipid patches may also be relevant to lipid rafts and cellular signaling events and inspire new functional materials.

Fabrication and characterization of new levan@CBD biocomposite sponges as potential materials in natural, non-toxic wound dressing applications.

Wound healing is a complex process; therefore, new dressings are frequently required to facilitate it. In this study, porous bacterial levan-based sponges containing cannabis oil (Lev@CBDs) were prepared and fully characterized. The sponges exhibited a suitable swelling ratio, proper water vapor transmission rate, sufficient thermal stability, desired mechanical properties, and good antioxidant and anti-inflammatory properties. The obtained Lev@CBD materials were evaluated in terms of their interaction with proteins, human serum albumin and fibrinogen, of which fibrinogen revealed the highest binding effect. Moreover, the obtained biomaterials exhibited antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, as well as being non-hemolytic material as indicated by hemolysis tests. Furthermore, the sponges were non-toxic and compatible with L929 mouse fibroblasts and HDF cells. Most significantly, the levan sponge with the highest content of cannabis oil, in comparison to others, retained its non-hemolytic, anti-inflammatory, and antimicrobial properties after prolonged storage in a climate chamber at a constant temperature and relative humidity. The designed sponges have conclusively proven their beneficial physicochemical properties and, at the preliminary stage, biocompatibility as well, and therefore can be considered a promising material for wound dressings in future in vivo applications.

Francisella tularensis Glyceraldehyde-3-Phosphate Dehydrogenase Is Relocalized during Intracellular Infection and Reveals Effect on Cytokine Gene Expression and Signaling.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is known for its multifunctionality in several pathogenic bacteria. Our previously reported data suggest that the GAPDH homologue of Francisella tularensis, GapA, might also be involved in other processes beyond metabolism. In the present study, we explored GapA's potential implication in pathogenic processes at the host cell level. Using immunoelectron microscopy, we demonstrated the localization of this bacterial protein inside infected macrophages and its peripheral distribution in bacterial cells increasing with infection time. A quantitative proteomic approach based on stable isotope labeling of amino acids in cell culture (SILAC) combined with pull-down assay enabled the identification of several of GapA's potential interacting partners within the host cell proteome. Two of these partners were further confirmed by alternative methods. We also investigated the impact of gapA deletion on the transcription of selected cytokine genes and the activation of the main signaling pathways. Our results show that ∆gapA-induced transcription of genes encoding several cytokines whose expressions were not affected in cells infected with a fully virulent wild-type strain. That might be caused, at least in part, by the detected differences in ERK/MAPK signaling activation. The experimental observations together demonstrate that the F. tularensis GAPDH homologue is directly implicated in multiple host cellular processes and, thereby, that it participates in several molecular mechanisms of pathogenesis.

Monomerization of Phthalocyanines in Water via Their Supramolecular Interactions with Cucurbiturils.

Aggregation of phthalocyanines (Pcs) represents a problematic feature that decreases the potential of these macrocycles in a number of applications. In this work, we present a supramolecular approach based on the interaction of aminoadamantyl-substituted Pcs with bulky and hydrophilic cucurbit[7]uril (CB[7]) to increase the levels of Pc monomers in water. A series of zinc(II) Pcs substituted at positions α or ß by an aminoadamantyl substituent (with a different level of alkylation of nitrogen) were prepared from the corresponding phthalonitriles. A 1H nuclear magnetic resonance study of the interaction of phthalonitriles with CB[7] in water confirmed the formation of an inclusion complex with an aminoadamantyl moiety with Ka values of ∼1012 M-1. The interaction of CB[7] with Pcs in water substantially weakened H-type aggregation and improved both fluorescence and singlet oxygen production, confirming that this approach is efficient for the monomerization of Pcs. In vitro evaluation of the photodynamic activity of prepared Pcs led to EC50 values in the submicromolar range on HeLa and SK-MEL-28 cells. However, the activity decreased for at least an order of magnitude after host-guest interaction with CB[7] despite better photophysical properties. This was attributed to a much lower uptake by cells due to the very bulky and hydrophilic character of the Pc-CB[7] assembly.

Proline, hydroxyproline, and pyrrolidone carboxylic acid derivatives as highly efficient but reversible transdermal permeation enhancers.

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.

Assessment of Streptococcus mutans biofilm formation on calcium phosphate ceramics: The role of crystalline composition and microstructure.

Streptococcus mutans is one of the bacteria that initiates the colonization of the pellicle at the tooth surface. It forms a plaque, together with other bacteria, which gradually dissolves the pellicle and leaves the tooth surface unprotected against the acidic oral environment. Calcium phosphate ceramics are excellent synthetic materials for the study of biofilm formation in dentistry because they are comparable to teeth in chemical composition and structure. Calcium phosphates can be processed to achieve a variety of crystalline compounds with biologically relevant ionic substitutions and structures that allow study of the effect of the surface chemistry and the topography independently. In this article, we describe the preparation and characterization of three types of calcium phosphate-based materials as a suitable surface for the formation of the S. mutans biofilm: beta-tricalcium phosphate (ß-TCP); sintered hydroxyapatite (SHA); and calcium-deficient hydroxyapatite (CDHA). The densest biofilms were formed on the surfaces of SHA and CDHA, with no significant differences due to the stoichiometry or microstructure. In contrast, ß-TCP showed a lower susceptibility to S. mutans biofilm formation, suggesting that the crystalline structure is the controlling parameter. Subsequently, SHA was selected to develop a dental biofilm model that allowed study of S. mutans biofilm susceptibility to chlorhexidine and ethanol.

Amphiphilic Cationic Phthalocyanines for Photodynamic Therapy of Cancer.

Effective interaction with biomembranes is essential for activity of photosensitizers; however, majority of them are highly charged symmetrical species. Amphiphilic cationic phthalocyanines differing in bulkiness of substitution on lipophilic part (-H, -SMe, -StBu) were therefore prepared. Compounds had high singlet oxygen production (ΦΔ =0.38-0.46, DMSO), good fluorescence emission (ΦF =0.21-0.26, DMSO), and log P values ranging -0.07-1.1 (1-octanol/PBS). Study of interaction with liposomes revealed that also bulky -StBu derivatives are able to enter biomembranes. Detail in vitro studies (toxicity, subcellular localization, type of cell death, and morphology) were performed. Compounds were characterized by excellent EC50 values in range of dozens of nM (HeLa, EA.hy926, MCF-7, HCT116), which were dependent on drug-light interval and reached plateau after 4 h on HeLa cells. Well-balanced lipophilicity with ability to interact with biomembranes rank these derivatives among perspective photosensitizers, even for vascular-targeted PDT (VTP) since they kill EA.hy926 without any preincubation time.

Renewable sorbent dispersive solid phase extraction automated by Lab-In-Syringe using magnetite-functionalized hydrophilic-lipophilic balanced sorbent coupled online to HPLC for determination of surface water contaminants.

An automated methodology for magnetic dispersive solid phase microextraction integrating bead injection approach for renewable sorbent introduction is presented for the first time and was successfully applied to the enrichment of water contaminants. For this purpose, a simple procedure was developed for the functionalization of commercial SupelTM-Select HLB (Hydrophilic modified styrene polymer) sorbent beads that allowed embedding magnetite nanoparticles (Fe3O4). The sorbent was then used in a dispersive solid phase extraction procedure that was carried out entirely inside the void of an automatic syringe pump following the flow-batch concept of Lab-In-Syringe including automated renewal of the sorbent for each analysis. Mixing processes, sorbent dispersion, and sorbent recovery were enabled by using a strong magnetic stirring bar, fabricated from a 3D printed polypropylene casing and neodymium magnets, inside the syringe. The final extract was submitted to online coupled liquid chromatography with spectrometric detection. System and methodology were applied to determine mebendazole, bisphenol A, benzyl 4-hydroxybenzoate, diclofenac, and triclosan selected as models from different groups of environmental contaminants of current concern. Experimental parameters including extraction and elution times, composition and volume of eluent, and bead recollection were optimized. Required system elements were produced by 3D printing. Enlarging the sample volume by repeated extraction to enhance the sensitivity of the method was studied. Using double extraction from 3.5 mL, limits of detection ranged from 1.2 µg L-1 to 6.5 µg L-1 with an RSD (n = 6) value less than 7% for all the analytes at 25 µg L-1 level. The method was linear in the range of 5-200 µg L-1 and was successfully implemented for the analysis of surface waters with analyte recoveries ranging from 78.4% to 105.6%.

Subphthalocyanines as Efficient Photosensitizers with Nanomolar Photodynamic Activity against Cancer Cells.

Because cancer is the second leading cause of death globally, investigation of new photosensitizers for photodynamic therapy is highly desirable. In this work, different peripherally substituted subphthalocyanines (SubPcs) with either a benzocrown moiety (CE-) or a tyrosine methyl ester (Tyr-) as the axial ligand have been prepared. Target SubPcs showed high ΦΔ values, >0.50 in EtOH. Both CE- and Tyr- moieties increased substantially the hydrophilicity of the compounds (log P = 1.79-2.63, n-octanol/PBS). Uptake to cells, subcellular localization, and monitoring of the progression of cell death over time are described. Improved spectroscopic behavior of the CE- series in cell culture medium resulted in higher photodynamic activity versus that of the Tyr- series. In particular, the peripherally triethylsulfanyl SubPc-CE exhibited extraordinarily low EC50 values of 2.3 and 4.4 nM after light activation and high TC50 values of 14.49 and 5.25 µM (i.e., dark toxicity without activation) on SK-MEL-28 and HeLa cells, respectively, which rank it among the best photosensitizers ever.

The electromembrane extraction of pharmaceutical compounds from animal tissues.

The reliable analysis of various compounds from tissue requires a tedious sample preparation. The sample pretreatment usually involves proper homogenization that facilitates extraction of target analytes, followed by an appropriate sample clean-up preventing matrix effects. Electromembrane extraction (EME) seems to have a significant potential to streamline the whole procedure. In this study, the applicability of EME for direct isolation of analytes from animal tissues was investigated for the first time. Extraction conditions were systematically optimized to isolate model analytes (daunorubicin and its metabolite daunorubicinol) from various tissues (myocardium, skeletal muscle and liver) coming from a pharmacokinetic study in rabbits. The relative recoveries of daunorubicin and its metabolite in all tissues, determined by the UHPLC-MS/MS method, were higher than 66 and 75%, respectively. Considerably low matrix effects (0 ± 8% with CV lower than 6%) and negligible content of phospholipids detected in EME extracts demonstrate the exceptional effectiveness of this microextraction approach in purification of tissue samples. The difference in the concentrations of the analytes determined after EME and reference liquid-liquid extraction of real tissue samples was lower than 12%, which further emphasized the trustworthiness of EME. Moreover, the considerable time reduction needed for sample treatment in case of EME must be emphasized. This study proved that EME is a simple, effective and reliable microextraction technique capable of direct extraction of the analytes from pulverized tissues without the need for an additional homogenization or purification step.

Tuning Photodynamic Properties of BODIPY Dyes, Porphyrins' Little Sisters.

The photodynamic properties of a series of non-halogenated, dibrominated and diiodinated BODIPYs with a phthalimido or amino end modification on the phenoxypentyl and phenoxyoctyl linker in the meso position were investigated. Halogen substitution substantially increased the singlet oxygen production based on the heavy atom effect. This increase was accompanied by a higher photodynamic activity against skin melanoma cancer cells SK-MEL-28, with the best compound reaching an EC50 = 0.052 ± 0.01 µM upon light activation. The dark toxicity (toxicity without light activation) of all studied dyes was not detected up to the solubility limit in cell culture medium (10 µM). All studied BODIPY derivatives were predominantly found in adiposomes (lipid droplets) with further lower signals colocalized in either endolysosomal vesicles or the endoplasmic reticulum. A detailed investigation of cell death indicated that the compounds act primarily through the induction of apoptosis. In conclusion, halogenation in the 2,6 position of BODIPY dyes is crucial for the efficient photodynamic activity of these photosensitizers.

Peripherally Crowded Cationic Phthalocyanines as Efficient Photosensitizers for Photodynamic Therapy.

Photodynamic therapy is a treatment modality of cancer based on the production of cytotoxic species upon the light activation of photosensitizers. Zinc phthalocyanine photosensitizers bearing four or eight bulky 2,6-di(pyridin-3-yl)phenoxy substituents were synthesized, and pyridyl moieties were methylated. The quaternized derivatives did not aggregate at all in water and retained their good photophysical properties. High photodynamic activity of these phthalocyanines was demonstrated on HeLa, MCF-7, and EA.hy926 cells with a very low EC50 of 50 nM (for the MCF-7 cell line) upon light activation while maintaining low toxicity in the dark (TC50 ≈ 600 µM), giving thus good phototherapeutic indexes (TC50/EC50) above 1400. The compounds localized primarily in the lysosomes, leading to their rupture after light activation. This induced an apoptotic cell death pathway with secondary necrosis because of extensive and swift damage to the cells. This work demonstrates the importance of a bulky and rigid arrangement of peripheral substituents in the development of photosensitizers.

Cationic Versus Anionic Phthalocyanines for Photodynamic Therapy: What a Difference the Charge Makes.

The literature reports on cationic and anionic phthalocyanines (Pcs) for photodynamic therapy suggest systematically significant differences in activity. In this work, ten different zinc(II) Pcs with carboxylate functions or quaternary nitrogens (hydrophilic anionic, hydrophilic cationic, amphiphilic anionic, and amphiphilic cationic) were investigated, with the aim of revealing reasons for such differences. In vitro assays on HeLa, MCF-7, and HCT-116 cells confirmed higher photoactivity for cationic Pcs (EC50 ∼ 3-50 nM) than for anionic Pcs (EC50 ∼ 0.3-10 µM), the latter being additionally significantly more active in serum-free medium. The environmental pH, binding to serum proteins, interaction with biomembranes, differences in subcellular localization, and relocalization after irradiation were found to be the main factors contributing to the generally lower photoactivity of anionic Pcs than that of the cationic derivatives. This result is not limited only to the presented derivatives and should be considered in the design of novel photosensitizers.

Dually directional glycosylated phthalocyanines as extracellular red-emitting fluorescent probes.

The development of new non-aggregated phthalocyanines bearing multivalent saccharide moieties on their macrocyclic rims is of great interest. Many characteristics, including water-solubility, non-toxicity and others, can be feasibly obtained by these amphiphiles which can be considered as a key solution for demonstrating highly efficient photoactive materials in water. Herein, a family of five newly prepared dually directional Zn(ii) containing phthalocyanines (PcG1-4) and azaphthalocyanine (AzaPcG1) glycoconjugates is described. The unique spatial arrangement of the glucoside units based on peripherally hexadeca-(PcG1) and nonperipherally octa-(PcG4) macrocycles provides a fully monomeric behaviour along with a high fluorescence (ΦF∼ 0.21) in aqueous solution. These amphiphiles were characterized by low toxicity, and an extremely low cellular uptake was obtained due to the highly polar nature of the glucoside substituents. Accordingly, their potential as suitable photoactive chromophores for red-emitting extracellular fluorescent probes has been confirmed upon the evaluation of paracellular transport using a layer of MDCKII cells with the permeability coefficient fully comparable with an established evaluator of the integrity of the monolayer.

Esters of terpene alcohols as highly potent, reversible, and low toxic skin penetration enhancers.

Skin penetration/permeation enhancers are compounds that improve (trans)dermal drug delivery. We designed hybrid terpene-amino acid enhancers by conjugating natural terpenes (citronellol, geraniol, nerol, farnesol, linalool, perillyl alcohol, menthol, borneol, carveol) or cinnamyl alcohol with 6-(dimethylamino)hexanoic acid through a biodegradable ester linker. The compounds were screened for their ability to increase the delivery of theophylline and hydrocortisone through and into human skin ex vivo. The citronellyl, bornyl and cinnamyl esters showed exceptional permeation-enhancing properties (enhancement ratios up to 82) while having low cellular toxicities. The barrier function of enhancer-treated skin (assessed by transepidermal water loss and electrical impedance) recovered within 24 h. Infrared spectroscopy suggested that these esters fluidized the stratum corneum lipids. Furthermore, the citronellyl ester increased the epidermal concentration of topically applied cidofovir, which is a potent antiviral and anticancer drug, by 15-fold. In conclusion, citronellyl 6-(dimethylamino)hexanoate is an outstanding enhancer with an advantageous combination of properties, which may improve the delivery of drugs that have a limited ability to cross biological barriers.

4-Methylcatechol, a Flavonoid Metabolite with Potent Antiplatelet Effects.

SCOPE: Intake of flavonoids from the diet can be substantial, and epidemiological studies suggest that these compounds can decrease the incidence of cardiovascular diseases by involvement with increased platelet aggregation. Although parent flavonoids possess antiplatelet effects, the clinical importance is disputable due to their very low bioavailability. Most of them are metabolized by human colon bacteria to smaller phenolic compounds, which reach higher plasma concentrations than the parent flavonoids. In this study, a series of 29 known flavonoid metabolites is tested for antiplatelet potential. METHODS AND RESULTS: Four compounds appear to have a biologically relevant antiplatelet effect using whole human blood. 4-Methylcatechol (4-MC) is clearly the most efficient being about 10× times more active than clinically used acetylsalicylic acid. This ex vivo effect is also confirmed using a potentially novel in-vivo-like ex ovo hen's egg model of thrombosis, where 4-MC significantly increases the survival of the eggs. The mechanism of action is studied and it seems that it is mainly based on the influence on intracellular calcium signaling. CONCLUSION: This study shows that some flavonoid metabolites formed by human microflora have a strong antiplatelet effect. This information can help to explain the antiplatelet potential of orally given flavonoids.

Red-Emitting Fluorescence Sensors for Metal Cations: The Role of Counteranions and Sensing of SCN- in Biological Materials.

The spatiotemporal sensing of specific cationic and anionic species is crucial for understanding the processes occurring in living systems. Herein, we developed new fluorescence sensors derived from tetrapyrazinoporphyrazines (TPyzPzs) with a recognition moiety that consists of an aza-crown and supporting substituents. Their sensitivity and selectivity were compared by fluorescence titration experiments with the properties of known TPyzPzs (with either one aza-crown moiety or two of these moieties in a tweezer arrangement). Method of standard addition was employed for analyte quantification in saliva. For K+ recognition, the new derivatives had comparable or larger association constants with larger fluorescence enhancement factors compared to that with one aza-crown. Their fluorescence quantum yields in the ON state were 18× higher than that of TPyzPzs with a tweezer arrangement. Importantly, the sensitivity toward cations was strongly dependent on counteranions and increased as follows: NO3- < Br- < CF3SO3- < ClO4- ≪ SCN-. This trend resembles the chaotropic ability expressed by the Hofmeister series. The high selectivity toward KSCN was explained by synergic association of both K+ and SCN- with TPyzPz sensors. The sensing of SCN- was further exploited in a proof of concept study to quantify SCN- levels in the saliva of a smoker and to demonstrate the sensing ability of TPyzPzs under in vitro conditions.

Novel SPME fibers based on a plastic support for determination of plasma protein binding of thiosemicarbazone metal chelators: a case example of DpC, an anti-cancer drug that entered clinical trials.

Solid-phase microextraction (SPME) is an alternative method to dialysis and ultrafiltration for the determination of plasma protein binding (PPB) of drugs. It is particularly advantageous for complicated analytes where standard methods are not applicable. Di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) is a lead compound of novel thiosemicarbazone anti-cancer drugs, which entered clinical trials in 2016. However, this agent exhibited non-specific binding on filtration membranes and had intrinsic chelation activity, which precluded standard PPB methods. In this study, using a simple and fast procedure, we prepared novel SPME fibers for extraction of DpC based on a metal-free, silicon string support, covered with C18 sorbent. Reproducibility of the preparation process was demonstrated by the percent relative standard deviation (RSD) of ≤ 9.2% of the amount of DpC extracted from PBS by several independently prepared fibers. The SPME procedure was optimized by evaluating extraction and desorption time profiles. Suitability of the optimized protocol was verified by examining reproducibility, linearity, and recovery of DpC extracted from PBS or plasma. All samples extracted by SPME were analyzed using an optimized and validated UHPLC-MS/MS method. The developed procedure was applied to the in vitro determination of PPB of DpC at two clinically relevant concentrations (500 and 1000 ng/mL). These studies showed that DpC is highly bound to plasma proteins (PPB ≥ 88%) and this did not differ significantly between both concentrations tested. This investigation provides novel data in the applicability of SPME for the determination of PPB of chelators, as well as useful information for the clinical development of DpC. Graphical abstract.

Regulation and role of endoglin in cholesterol-induced endothelial and vascular dysfunction in vivo and in vitro.

Our objective was to investigate the effect of cholesterol [hypercholesterolemia and 7-ketocholesterol (7K)] on endoglin (Eng) expression and regulation with respect to endothelial or vascular dysfunction in vivo and in vitro. In vivo experiments were performed in 2-mo-old atherosclerosis-prone apolipoprotein E-deficient/LDL receptor-deficient (ApoE-/-/LDLR-/-) female mice and their wild-type C57BL/6J littermates. In in vitro experiments, human aortic endothelial cells (HAECs) were treated with 7K. ApoE-/-/LDLR-/- mice developed hypercholesterolemia accompanied by increased circulating levels of P-selectin and Eng and a disruption of NO metabolism. Functional analysis of the aorta demonstrated impaired vascular reactivity, and Western blot analysis revealed down-regulation of membrane Eng/Smad2/3/eNOS signaling in ApoE-/-/LDLR-/- mice. 7K increased Eng expression via Krüppel-like factor 6 (KLF6), liver X nuclear receptor, and NF-κB in HAECs. 7K-induced Eng expression was prevented by the treatment with 2-hydroxypropyl-ß-cyclodextrin; 8-{[5-chloro-2-(4-methylpiperazin-1-yl) pyridine-4-carbonyl] amino}-1-(4-fluorophenyl)-4, 5-dihydrobenzo[g]indazole-3-carboxamide; or by KLF6 silencing. 7K induced increased adhesion and transmigration of monocytic human leukemia promonocytic cell line cells and was prevented by Eng silencing. We concluded that hypercholesterolemia altered Eng expression and signaling, followed by endothelial or vascular dysfunction before formation of atherosclerotic lesions in ApoE-/-/LDLR-/- mice. By contrast, 7K increased Eng expression and induced inflammation in HAECs, which was followed by an increased adhesion and transmigration of monocytes via endothelium, which was prevented by Eng inhibition. Thus, we propose a relevant role for Eng in endothelial or vascular dysfunction or inflammation when exposed to cholesterol.-Vicen, M., Vitverova, B., Havelek, R., Blazickova, K., Machacek, M., Rathouska, J., Najmanová, I., Dolezelova, E., Prasnicka, A., Sternak, M., Bernabeu, C., Nachtigal, P. Regulation and role of endoglin in cholesterol-induced endothelial and vascular dysfunction in vivo and in vitro.

Fluorescent Penetration Enhancers Reveal Complex Interactions among the Enhancer, Drug, Solvent, and Skin.

Skin penetration/permeation enhancers facilitate drug delivery through the skin barrier. However, the specific mechanisms that govern the enhancer interactions with the skin, drug, and donor solvent are not fully understood. We designed and synthesized fluorescent-labeled enhancers by attaching 7-nitrobenzo[c][1,2,5]oxadiazol-4-yl (NBD) groups to 6-aminohexanoic acid esters. These NBD esters (applied at a 1% concentration) enhanced the permeation of the model drugs theophylline and hydrocortisone through human skin in vitro up to 6.6- and 3.9-times, respectively. The enhancement effects were strongly affected by the ester chain length (C8-C12) and the polarity of the donor solvent. Using high-performance liquid chromatography with fluorescence detection, no NBD esters were detected in the acceptor buffer, but their hydrolysis product, NBD acid, was detected, whereas both acid and esters were found in the skin. The enhancer hydrolysis occurred in the lower stratum corneum and epidermis; more hydrophilic NBD acid, which is an inactive enhancer, penetrated deeper. This illustrates the principle of biodegradable enhancers. The enhancer concentrations in the skin depended not only on the enhancer chain length and the donor solvent, but also on the drug used. Thus, the drug, when coapplied with the enhancer, modulates the enhancer penetration into the skin and, consequently, its effect. Finally, active (NBD-C8 ester) and inactive (NBD acid) enhancers were visualized in human skin by confocal laser scanning microscopy. Both compounds were found mostly in the stratum corneum intercellular spaces, suggesting that although both are located within the skin barrier lipids, only the active ester is able to effectively interact with the lipids, which was proved by infrared spectroscopy of enhancer-treated stratum corneum. This proof-of-concept study illustrates the use of fluorescent enhancers to obtain insight into the skin penetration/permeation process; interactions among the enhancer, drug, solvent, and skin; and enhancer metabolism.