Postmortem chondrocyte viability in porcine articular cartilage: Influence of time, temperature, and burial under winter conditions.

The aim of the present study was to investigate the effects of time, temperature, and burial in a natural environment on the viability of chondrocytes in porcine femoral condyles using confocal laser scanning microscopy. Hind trotters from 10 pigs were buried or left unburied. Samples were collected daily and stained with a combination of vital dyes (calcein-AM and ethidium homodimer-1). The chondrocytes showed an intense staining corresponding to their vitality. In the first 3 days, viability decreased slowly and showed no statistical difference between buried and unburied samples. After the first 3 days, it decreased rapidly, with the viability of the buried samples being 66% on day 4, decreasing to 25% on day 8 and to 16% on day 10, while in the unburied samples it decreased to 43% on day 4, 13% on day 8 and 5% on day 10. Our results indicate a time, temperature, and burial dependent decrease in chondrocyte viability and suggest the use of chondrocyte viability as a marker for estimating PMI in both the natural environment and in animals, as well as its potential use in humans.

Characterization of two distinct immortalized endothelial cell lines, EA.hy926 and HMEC-1, for in vitro studies: exploring the impact of calcium electroporation, Ca2+ signaling and transcriptomic profiles.

BACKGROUND: Disruption of Ca2+ homeostasis after calcium electroporation (CaEP) in tumors has been shown to elicit an enhanced antitumor effect with varying impacts on healthy tissue, such as endothelium. Therefore, our study aimed to determine differences in Ca2+ kinetics and gene expression involved in the regulation of Ca2+ signaling and homeostasis, as well as effects of CaEP on cytoskeleton and adherens junctions of the established endothelial cell lines EA.hy926 and HMEC-1. METHODS: CaEP was performed on EA.hy926 and HMEC-1 cells with increasing Ca2+ concentrations. Viability after CaEP was assessed using Presto Blue, while the effect on cytoskeleton and adherens junctions was evaluated via immunofluorescence staining (F-actin, α-tubulin, VE-cadherin). Differences in intracellular Ca2+ regulation ([Ca2+]i) were determined with spectrofluorometric measurements using Fura-2-AM, exposing cells to DPBS, ionomycin, thapsigargin, ATP, bradykinin, angiotensin II, acetylcholine, LaCl3, and GdCl3. Molecular distinctions were identified by analyzing differentially expressed genes and pathways related to the cytoskeleton and Ca2+ signaling through RNA sequencing. RESULTS: EA.hy926 cells, at increasing Ca2+ concentrations, displayed higher CaEP susceptibility and lower survival than HMEC-1. Immunofluorescence confirmed CaEP-induced, time- and Ca2+-dependent morphological changes in EA.hy926's actin filaments, microtubules, and cell-cell junctions. Spectrofluorometric Ca2+ kinetics showed higher amplitudes in Ca2+ responses in EA.hy926 exposed to buffer, G protein coupled receptor agonists, bradykinin, and angiotensin II compared to HMEC-1. HMEC-1 exhibited significantly higher [Ca2+]i changes after ionomycin exposure, while responses to thapsigargin, ATP, and acetylcholine were similar in both cell lines. ATP without extracellular Ca2+ ions induced a significantly higher [Ca2+]i rise in EA.hy926, suggesting purinergic ionotropic P2X and metabotropic P2Y receptor activation. RNA-sequencing analysis showed significant differences in cytoskeleton- and Ca2+-related gene expression, highlighting upregulation of ORAI2, TRPC1, TRPM2, CNGA3, TRPM6, and downregulation of TRPV4 and TRPC4 in EA.hy926 versus HMEC-1. Moreover, KEGG analysis showed upregulated Ca2+ import and downregulated export genes in EA.hy926. CONCLUSIONS: Our finding show that significant differences in CaEP response and [Ca2+]i regulation exist between EA.hy926 and HMEC-1, which may be attributed to distinct transcriptomic profiles. EA.hy926, compared to HMEC-1, displayed higher susceptibility and sensitivity to [Ca2+]i changes, which may be linked to overexpression of Ca2+-related genes and an inability to mitigate changes in [Ca2+]i. The study offers a bioinformatic basis for selecting EC models based on research objectives.

Exploring pta Alternatives in the Development of Ruthenium-Arene Anticancer Compounds.

Organoruthenium pyrithione (1-hydroxypyridine-2-thione) complexes have been shown in our recent studies to be a promising family of compounds for development of new anticancer drugs. The complex [(η6-p-cymene)Ru(pyrithionato)(pta)]PF6 contains phosphine ligand pta (1,3,5-triaza-7-phosphaadamantane) as a functionality that improves the stability of the complex and its aqueous solubility. Here, we report our efforts to find pta alternatives and discover new structural elements to improve the biological properties of ruthenium anticancer drugs. The pta ligand was replaced by a selection of phosphine, phosphite, and arsine ligands to identify new functionalities, leading to improvement in inhibitory potency towards enzyme glutathione S-transferase. In addition, cytotoxicity in breast, bone, and colon cancers was investigated.

Novel Organoruthenium(II) Complex C1 Selectively Inhibits Butyrylcholinesterase without Side Effects on Neuromuscular Transmission.

Enzyme butyrylcholinesterase (BChE) shows increased activity in some brain regions after progression of Alzheimer's disease and is therefore one of the therapeutic targets for symptomatic treatment of this neurodegenerative disorder. The organoruthenium(II) complex [(η6-p-cymene)Ru(II)(1-hydroxy-3-methoxypyridine-2(1H)-thionato)pta]PF6 (C1) was designed based on the results of our previous structure-activity studies. Inhibitory activity toward cholinesterase enzymes shows that this complex selectively, competitively, and reversibly inhibits horse serum BChE (hsBChE) with an IC50 value of 2.88 µM. When tested at supra-pharmacological concentrations (30, 60, 90, and 120 µM), C1 had no significant effect on the maximal amplitude of nerve-evoked and directly elicited single-twitch and tetanic contractions. At the highest tested concentration (120 µM), C1 had no effect on resting membrane potential, but significantly decreased the amplitude of miniature end-plate potentials (MEPP) without reducing their frequency. The same concentration of C1 had no effect on the amplitude of end-plate potentials (EPP), however it shortened the half-decay time of MEPPs and EPPs. The decrease in the amplitude of MEPPs and shortening of the half-decay time of MEPPs and EPPs suggest a possible weak inhibitory effect on muscle-type nicotinic acetylcholine receptors (nAChR). These combined results show that, when applied at supra-pharmacological concentrations up to 120 µM, C1 does not importantly affect the physiology of neuromuscular transmission and skeletal muscle contraction.

Development of potent cholinesterase inhibitors based on a marine pharmacophore.

The management of neurological disorders such as dementia associated with Alzheimer's or Parkinson's disease includes the use of cholinesterase inhibitors. These compounds can slow down the progression of these diseases and can also be used in the treatment of glaucoma and myasthenia gravis. The majority of the cholinesterase inhibitors used in the clinic are derived from natural products and our current paper describes the use of a small marine pharmacophore to develop potent and selective cholinesterase inhibitors. Fourteen small inhibitors were designed based on recent discoveries about the inhibitory potential of a range of related marine secondary metabolites. The compounds were evaluated, in kinetic enzymatic assays, for their ability to inhibit three different cholinesterase enzymes and it was shown that compounds with a high inhibitory activity towards electric eel and human recombinant acetylcholinesterase (IC50 between 20-70 µM) could be prepared. It was also shown that this compound class was particularly active against horse serum butyrylcholinesterase, with IC50 values between 0.8-16 µM, which is an order of magnitude more potent than the clinically used positive control neostigmine. The compounds were further tested for off-target toxicity against both human umbilical vein endothelial cells and bovine and human erythrocytes and were shown to display a low mammalian cellular toxicity. Overall, the study illustrates how the brominated dipeptide marine pharmacophore can be used as a versatile natural scaffold for the design of potent, and selective cholinesterase inhibitors.

Fluctuations of Physiological Variables during Conditioning of Lipizzan Fillies before Starting under Saddle.

Scientific studies on the physiological responses of young horses to workloads are limited. Therefore, the aim of our study was to determine the basal values of some cardiovascular, thermoregulatory, hematological, and biochemical parameters in 10 purebred Lipizzan fillies aged 4 years in the initial phase of training, and their responses to a graded workload, i.e., by lunging for 15 min in four exercise tests at 2-week intervals. The basal values of the measured parameters were within a range for warm-blooded horses and mostly increased after exercise in all four exercise tests. Resting heart rates were above physiological values at the baseline but decreased as the study progressed. Bilateral symmetry of body surface temperatures (BSTs) was confirmed at rest and after exercise. The highest BSTs were measured at the cranial, followed by the caudal and distal body regions. A moderate increase in cortisol and a small increase in lactate concentration indicated a low intensity of workload. The results presented contribute to the knowledge of the complex physiological processes that occur in young horses during exercise and provide a basis for further research into the field of sports physiology and welfare, as well as the conservation and development of the Lipizzan breed.

Spatial Distribution and Stability of Cholinesterase Inhibitory Protoberberine Alkaloids from Papaver setiferum.

During a research program to identify new cholinesterase inhibitors of natural origin, two new 7,8-didehydroprotoberberine alkaloids (1 and 2) and nine known compounds (3-11) were isolated from the capsules of the common ornamental poppy, Papaver setiferum (previously P. pseudo-orientale). Despite their reported instability, the 7,8-didehydroprotoberberines isolated herein appeared relatively stable, particularly as their trifluoroacetic acid salts. The spatial distributions of the isolated alkaloids were also analyzed using desorption electrospray ionization imaging mass spectrometry. The alkaloids were localized predominantly within the walls and vascular bundles of the capsules, with the highest relative abundances occurring in the lower half of the capsules toward the peduncle. The relative abundances of the alkaloids were also compared across plant development stages. Although most alkaloids did not show clear patterns in their concentration across development stages, the concentration of suspected oxidation products clearly spiked upon plant death. Finally, all isolated natural products were screened for inhibitory activities against a panel of cholinesterases, from both human and animal sources. These studies identified several competitive inhibitors of cholinesterases with potency in the low micromolar range (1-4, 6, 7), offering new lead compounds for the development of cholinesterase inhibitory drugs.

Fine Tuning of Cholinesterase and Glutathione-S-Transferase Activities by Organoruthenium(II) Complexes.

Cholinesterases (ChEs) show increased activities in patients with Alzheimer's disease, and remain one of the main therapeutic targets for treatment of this neurodegenerative disorder. A library of organoruthenium(II) complexes was prepared to investigate the influence of their structural elements on inhibition of ChEs, and on another pharmacologically important group of enzymes, glutathione S-transferases (GSTs). Two groups of organoruthenium(II) compounds were considered: (i) organoruthenium(II) complexes with p-cymene as an arene ligand, and (ii) organoruthenium(II) carbonyl complexes as CO-releasing molecules. Eight organoruthenium complexes were screened for inhibitory activities against ChEs and GSTs of human and animal origins. Some compounds inhibited all of these enzymes at low micromolar concentrations, while others selectively inhibited either ChEs or GSTs. This study demonstrates the importance of the different structural elements of organoruthenium complexes for their inhibitory activities against ChEs and GSTs, and also proposes some interesting compounds for further preclinical testing as ChE or GST inhibitory drugs.

Effects of Bioinsecticidal Aegerolysin-Based Cytolytic Complexes on Non-Target Organisms.

Aegerolysin proteins ostreolysin A6 (OlyA6), pleurotolysin A2 (PlyA2) and erylysin A (EryA) produced by the mushroom genus Pleurotus bind strongly to an invertebrate-specific membrane sphingolipid, and together with a protein partner pleurotolysin B (PlyB), form transmembrane pore complexes. This pore formation is the basis for the selective insecticidal activity of aegerolysin/PlyB complexes against two economically important coleopteran pests: the Colorado potato beetle and the western corn rootworm. In this study, we evaluated the toxicities of these aegerolysin/PlyB complexes using feeding tests with two ecologically important non-target arthropod species: the woodlouse and the honey bee. The mammalian toxicity of the EryA/PlyB complex was also evaluated after intravenous administration to mice. None of the aegerolysin/PlyB complexes were toxic against woodlice, but OlyA6/PlyB and PlyA2/PlyB were toxic to honeybees, with 48 h mean lethal concentrations (LC50) of 0.22 and 0.39 mg/mL, respectively, in their food. EryA/PlyB was also tested intravenously in mice up to 3 mg/kg body mass, without showing toxicity. With no toxicity seen for EryA/PlyB for environmentally beneficial arthropods and mammals at the tested concentrations, these EryA/PlyB complexes are of particular interest for development of new bioinsecticides for control of selected coleopteran pests.

Electron Paramagnetic Resonance Gives Evidence for the Presence of Type 1 Gonadotropin-Releasing Hormone Receptor (GnRH-R) in Subdomains of Lipid Rafts.

This study investigated the effect of type 1 gonadotropin releasing hormone receptor (GnRH-R) localization within lipid rafts on the properties of plasma membrane (PM) nanodomain structure. Confocal microscopy revealed colocalization of PM-localized GnRH-R with GM1-enriched raft-like PM subdomains. Electron paramagnetic resonance spectroscopy (EPR) of a membrane-partitioned spin probe was then used to study PM fluidity of immortalized pituitary gonadotrope cell line αT3-1 and HEK-293 cells stably expressing GnRH-R and compared it with their corresponding controls (αT4 and HEK-293 cells). Computer-assisted interpretation of EPR spectra revealed three modes of spin probe movement reflecting the properties of three types of PM nanodomains. Domains with an intermediate order parameter (domain 2) were the most affected by the presence of the GnRH-Rs, which increased PM ordering (order parameter (S)) and rotational mobility of PM lipids (decreased rotational correlation time (τc)). Depletion of cholesterol by methyl-ß-cyclodextrin (methyl-ß-CD) inhibited agonist-induced GnRH-R internalization and intracellular Ca2+ activity and resulted in an overall reduction in PM order; an observation further supported by molecular dynamics (MD) simulations of model membrane systems. This study provides evidence that GnRH-R PM localization may be related to a subdomain of lipid rafts that has lower PM ordering, suggesting lateral heterogeneity within lipid raft domains.

Effect of Hydrolyzable Tannins on Glucose-Transporter Expression and Their Bioavailability in Pig Small-Intestinal 3D Cell Model.

Intestinal transepithelial transport of glucose is mediated by glucose transporters, and affects postprandial blood-glucose levels. This study investigates the effect of wood extracts rich in hydrolyzable tannins (HTs) that originated from sweet chestnut (Castanea sativa Mill.) and oak (Quercus petraea) on the expression of glucose transporter genes and the uptake of glucose and HT constituents in a 3D porcine-small-intestine epithelial-cell model. The viability of epithelial cells CLAB and PSI exposed to different HTs was determined using alamarBlue®. qPCR was used to analyze the gene expression of SGLT1, GLUT2, GLUT4, and POLR2A. Glucose uptake was confirmed by assay, and LC-MS/ MS was used for the analysis of HT bioavailability. HTs at 37 µg/mL were found to adversely affect cell viability and downregulate POLR2A expression. HT from wood extract Tanex at concentrations of 4 µg/mL upregulated the expression of GLUT2, as well as glucose uptake at 1 µg/mL. The time-dependent passage of gallic acid through enterocytes was influenced by all wood extracts compared to gallic acid itself as a control. These results suggest that HTs could modulate glucose uptake and gallic acid passage in the 3D cell model.

The first Kunitz-type proteins from a viperid venom that potentiate neuromuscular transmission.

Kunitz-type proteins that interfere with neuronal transmission have been thus far exclusively detected in venoms of elapid snakes. Here, we report for the first time that such proteins are also present in the venom of a viperid snake. From the venom of the nose-horned viper (Vipera ammodytes ammodytes; Vaa), we isolated Kunitz-type chymotrypsin inhibitors (VaaChi) and demonstrated that these molecules also significantly increase the amplitudes of an indirectly evoked simple muscle contraction of the mouse hemidiaphragm, the end-plate potential and the miniature end-plate potential. By facilitating neuromuscular transmission, these proteins resemble structurally homologous dendrotoxins from mamba (Dendroaspis spp.) venoms, which are blockers of voltage-dependent K+ channels at the presynaptic site of the neuromuscular junction. What is the mechanism behind facilitation of neuromuscular transmission by VaaChi has not been established yet, however, blocking of K+ channels does not seem to be the most probable option.

Structural and functional characterization of an organometallic ruthenium complex as a potential myorelaxant drug.

In addition to antibacterial and antitumor effects, synthetic ruthenium complexes have been reported to inhibit several medicinally important enzymes, including acetylcholinesterase (AChE). They may also interact with muscle-type nicotinic acetylcholine receptors (nAChRs) and thus affect the neuromuscular transmission and muscle function. In the present study, the effects of the organometallic ruthenium complex of 5-nitro-1,10-phenanthroline (nitrophen) were evaluated on these systems. The organoruthenium-nitrophen complex [(η6-p-cymene)Ru(nitrophen)Cl]Cl; C22H21Cl2N3O2Ru (C1-Cl) was synthesized, structurally characterized and evaluated in vitro for its inhibitory activity against electric eel acetylcholinesterase (eeAChE), human recombinant acetylcholinesterase (hrAChE), horse serum butyrylcholinesterase (hsBChE) and horse liver glutathione-S-transferase. The physiological effects of C1-Cl were then studied on isolated mouse phrenic nerve-hemidiaphragm muscle preparations, by means of single twitch measurements and electrophysiological recordings. The compound C1-Cl acted as a competitive inhibitor of eeAChE, hrAChE and hsBChE with concentrations producing 50 % inhibition (IC50) of enzyme activity ranging from 16 to 26 µM. Moreover, C1-Cl inhibited the nerve-evoked isometric muscle contraction (IC50 = 19.44 µM), without affecting the directly-evoked muscle single twitch up to 40 µM. The blocking effect of C1-Cl was rapid and almost completely reversed by neostigmine, a reversible cholinesterase inhibitor. The endplate potentials were also inhibited by C1-Cl in a concentration-dependent manner (IC50 = 7.6 µM) without any significant change in the resting membrane potential of muscle fibers up to 40 µM. Finally, C1-Cl (5-40 µM) decreased (i) the amplitude of miniature endplate potentials until a complete block by concentrations higher than 25 µM and (ii) their frequency at 10 µM or higher concentrations. The compound C1-Cl reversibly blocked the neuromuscular transmission in vitro by a non-depolarizing mechanism and mainly through an action on postsynaptic nAChRs. The compound C1-Cl may be therefore interesting for further preclinical testing as a new competitive neuromuscular blocking, and thus myorelaxant, drug.

Natural cholinesterase inhibitors from marine organisms.

Covering: Published between 1974 up to 2018Inhibition of cholinesterases is a common approach for the management of several disease states. Most notably, cholinesterase inhibitors are used to alleviate the symptoms of neurological disorders like dementia and Alzheimer's disease and treat myasthenia gravis and glaucoma. Historically, most drugs of natural origin have been isolated from terrestrial sources and inhibitors of cholinesterases are no exception. However, the last 50 years have seen a rise in the quantity of marine natural products with close to 25 000 reported in the scientific literature. A number of marine natural products with potent cholinesterase inhibitory properties have also been reported; isolated from a variety of marine sources from algae to ascidians. Representing a diverse range of structural classes, these compounds provide inspirational leads that could aid the development of therapeutics. The current paper aims to, for the first time, comprehensively summarize the literature pertaining to cholinesterase inhibitors derived from marine sources, including the first papers published in 1974 up to 2018. The review does not report bioactive extracts, only isolated compounds, and a specific focus lies on compounds with reported dose-response data. In vivo and mechanistic data is included for compounds where this is reported. In total 185 marine cholinesterase inhibitors and selected analogs have been identified and reported and some of the compounds display inhibitory activities comparable or superior to cholinesterase inhibitors in clinical use.

APS8 Delays Tumor Growth in Mice by Inducing Apoptosis of Lung Adenocarcinoma Cells Expressing High Number of α7 Nicotinic Receptors.

The alkylpyridinium polymer APS8, a potent antagonist of α7 nicotinic acetylcholine receptors (nAChRs), selectively induces apoptosis in non-small cell lung cancer cells but not in normal lung fibroblasts. To explore the potential therapeutic value of APS8 for at least certain types of lung cancer, we determined its systemic and organ-specific toxicity in mice, evaluated its antitumor activity against adenocarcinoma xenograft models, and examined the in-vitro mechanisms of APS8 in terms of apoptosis, cytotoxicity, and viability. We also measured Ca2+ influx into cells, and evaluated the effects of APS8 on Ca2+ uptake while siRNA silencing of the gene for α7 nAChRs, CHRNA7. APS8 was not toxic to mice up to 5 mg/kg i.v., and no significant histological changes were observed in mice that survived APS8 treatment. Repetitive intratumoral injections of APS8 (4 mg/kg) significantly delayed growth of A549 cell tumors, and generally prevented regrowth of tumors, but were less effective in reducing growth of HT29 cell tumors. APS8 impaired the viability of A549 cells in a dose-dependent manner and induced apoptosis at micro molar concentrations. Nano molar APS8 caused minor cytotoxic effects, while cell lysis occurred at APS8 >3 µM. Furthermore, Ca2+ uptake was significantly reduced in APS8-treated A549 cells. Observed differences in response to APS8 can be attributed to the number of α7 nAChRs expressed in these cells, with those with more AChRs (i.e., A549 cells) being more sensitive to nAChR antagonists like APS8. We conclude that α7 nAChR antagonists like APS8 have potential to be used as therapeutics for tumors expressing large numbers of α7 nAChRs.

Organoruthenium Prodrugs as a New Class of Cholinesterase and Glutathione-S-Transferase Inhibitors.

A small library of 17 organoruthenium compounds with the general formula [RuII (fcl)(chel)(L)]n+ (in which fcl=face capping ligand, chel=chelating bidentate ligand, and L=monodentate ligand) were screened for inhibitory activity against cholinesterases and glutathione-S-transferases of human and animal origins. Compounds were selected to include different chelating ligands (i.e., N,N-, N,O-, O,O-, S,O-) and monodentate ligands that can modulate the aquation rate of the metal species. Compounds with a labile ruthenium chloride bond that provided rapid aquation were found to inhibit both sets of enzymes in reversible competitive modes and at pharmaceutically relevant concentrations. When applied at concentrations that completely abolish the activity of human acetylcholinesterase, the lead compound [(η6 -p-cymene)Ru(pyrithionato)Cl] (C1 a) showed no undesirable physiological responses on the neuromuscular system. Finally, C1 a was not cytotoxic against non-transformed cells at pharmaceutically relevant concentrations.

Confocal micrographs: automated segmentation and quantitative shape analysis of neuronal cells treated with ostreolysin A/pleurotolysin B pore-forming complex.

Detailed shape analysis of cells is important to better understand the physiological mechanisms of toxins and determine their effects on cell morphology. This study aimed to develop a procedure for accurate morphological analysis of cell shape and use it as a tool to estimate toxin activity. With the aim of optimizing the method of cell morphology analysis, we determined the influence of ostreolysin A and pleurotolysin B complex (OlyA/PlyB) on the morphology of murine neuronal NG108-15 cells. A computational method was introduced and successfully applied to quantify morphological attributes of the NG108-15 cell line before and after 30 and 60 min exposure to OlyA/PlyB using confocal microscopy. The modified circularity measure [Formula: see text] for shape analysis was applied, which defines the degree to which the shape of the neuron differs from a perfect circle. It enables better detection of small changes in the shape of cells, making the outcome easily detectable numerically. Additionally, we analyzed the influence of OlyA/PlyB on the cell area, allowing us to detect the cells with blebs. This is important because the formation of plasma membrane protrusions such as blebs often reflects cell injury that leads to necrotic cell death. In summary, we offer a novel analytical method of neuronal cell shape analysis and its correlation with the toxic effects of the pore-forming OlyA/PlyB toxin in situ.

Increased permeability of blood vessels after reversible electroporation is facilitated by alterations in endothelial cell-to-cell junctions.

Delivery of electric field pulses, i.e. electroporation (EP), to tissues has been shown to have a blood flow modifying effect. Indeed, the diameter of blood vessels exposed to EP is immediately reduced resulting in blood flow abrogation, followed by an increase in vascular permeability. The main cause of the increased permeability remains unknown. The aim of this study was to determine whether the in vivo effects of EP on permeability of blood vessels are linked to the permeabilization of endothelial cells' membrane (EC) and/or disruption of cell-to-cell junctions. We used a dorsal window chamber model in C57Bl/6 mice coupled with multiphoton microscopy and fluorescently labelled antibodies against PECAM-1 (CD31) to visualize endothelial cell-to-cell junctions. Clinically validated EP parameters were used and behavior of cell-to-cell junctions, in combination with leakage of 70 kDa fluorescein isothiocyanate labelled dextran (FD), was followed in time. After EP, a constriction of blood vessels was observed and correlated with the change in the shape of ECs. This was followed by an increase in permeability of blood vessels for 70 kDa FD and a decrease in the volume of labelled cell-to-cell junctions. Both parameters returned to pre-treatment values in 50% of mice. For the remaining 50%, we hypothesize that disruption of cell-to-cell junctions after EP may trigger the platelet activation cascade. Our findings show for the first time in vivo that alterations in cell-to-cell junctions play an important role in the response of blood vessels to EP and explain their efficient permeabilization.

Natural polymeric 3-alkylpyridinium salt affects vertebrate skeletal muscle contractility by preferentially blocking neuromuscular transmission.

The effects of natural polymeric alkylpyridinium salt (nPoly-3-APS), a potent acetylcholinesterase inhibitor isolated from the marine sponge Reniera sarai, were studied on isolated mouse phrenic nerve-hemidiaphragm muscle preparations using electrophysiological approaches. nPoly-3-APS inhibited nerve-evoked isometric muscle twitch and tetanic contraction in a concentration-dependent manner (IC50=29.4µM and 18.5µM, respectively) and produced a 30-44% decrease of directly muscle-elicited twitch and tetanus amplitudes at 54.4µM. Additionally, nPoly-3-APS (9.1-27.2µM) markedly decreased the amplitude of miniature endplate potentials, while their frequency was only affected at the highest concentration used. Endplate potentials were also inhibited by nPoly-3-APS in a concentration-dependent manner (IC50=20.1µM), without significant change in the resting membrane potential of muscle fibers (up to 54.4µM). In conclusion, our results show, for the first time, that nPoly-3-APS preferentially blocks the neuromuscular transmission, in vitro, by a non-depolarizing mechanism. This strongly suggests that the in vivo toxicity of nPoly-3-APS mainly occurs through an antagonist action of the compound on nicotinic acetylcholine receptors of skeletal muscles.

Discorhabdin alkaloids from Antarctic Latrunculia spp. sponges as a new class of cholinesterase inhibitors.

The brominated pyrroloiminoquinone alkaloids discorhabdins B, L and G and 3-dihydro-7,8- dehydrodiscorhabdin C, isolated from methanol extracts of two specimens of Latrunculia sp. sponges collected near the Antarctic Peninsula, are here demonstrated for the first time to be reversible competitive inhibitors of cholinesterases. They showed Ki for electric eel acetylcholinesterase of 1.6-15.0 µM, for recombinant human acetylcholinesterase of 22.8-98.0 µM, and for horse serum butyrylcholinesterase of 5.0-76.0 µM. These values are promising when compared to the current cholinesterase inhibitors used for treatment of patients with Alzheimer's disease, to counteract the acetylcholine deficiency in the brain. Good correlation was obtained between IC50 data and results by molecular docking calculation on the binding interactions within the acetylcholinesterase active site, which also indicated the moieties in discorhabdin structures involved. To avoid unwanted peripheral side effects that can appear in patients using some acetylcholinesterase inhibitors, electrophysiological experiments were carried out on one of the most active of these compounds, discorhabdin G, which confirmed that it had no detectable undesirable effects on neuromuscular transmission and skeletal muscle function. These findings are promising for development of cholinesterase inhibitors based on the scaffold of discorhabdins, as potential new agents for treatment of patients with Alzheimer's disease.