Factors influencing the efficacy of recombinant tissue plasminogen activator: Implications for ischemic stroke treatment

Intravenous thrombolysis with a recombinant tissue plasminogen activator (rt-PA) is the first-line treatment of acute ischemic stroke. However, successful recanalization is relatively low and the underlying processes are not completely understood. The goal was to provide insights into clinically important factors potentially limiting rt-PA efficacy such as clot size, rt-PA concentration, clot age and also rt-PA in combination with heparin anticoagulant. We established a static in vitro thrombolytic model based on red blood cell (RBC) dominant clots prepared using spontaneous clotting from the blood of healthy donors. Thrombolysis was determined by clot mass loss and by RBC release. The rt-PA became increasingly less efficient for clots larger than 50 μl at a clinically relevant concentration of 1.3 mg/l. A tenfold decrease or increase in concentration induced only a 2-fold decrease or increase in clot degradation. Clot age did not affect rt-PA-induced thrombolysis but 2-hours-old clots were degraded more readily due to higher activity of spontaneous thrombolysis, as compared to 5-hours-old clots. Finally, heparin (50 and 100 IU/ml) did not influence the rt-PA-induced thrombolysis. Our study provided in vitro evidence for a clot size threshold: clots larger than 50 μl are hard to degrade by rt-PA. Increasing rt-PA concentration provided limited thrombolytic efficacy improvement, whereas heparin addition had no effect. However, the higher susceptibility of younger clots to thrombolysis may prompt a shortened time from the onset of stroke to rt-PA treatment.

Dexamethasone nanomedicines with optimized drug release kinetics tailored for treatment of site-specific rheumatic musculoskeletal diseases

The application of polymer-based drug delivery systems is advantageous for improved pharmacokinetics, controlled drug release, and decreased side effects of therapeutics for inflammatory disease. Herein, we describe the synthesis and characterization of linear N-(2-hydroxypropyl)methacrylamide-based polymer conjugates designed for controlled release of the anti-inflammatory drug dexamethasone through pH-sensitive bonds. The tailored release rates were achieved by modifying DEX with four oxo-acids introducing reactive oxo groups to the DEX derivatives. Refinement of reaction conditions yielded four well-defined polymer conjugates with varied release profiles which were more pronounced at the lower pH in cell lysosomes. In vitro evaluations in murine peritoneal macrophages, human synovial fibroblasts, and human peripheral blood mononuclear cells demonstrated that neither drug derivatization nor polymer conjugation affected cytotoxicity or anti-inflammatory properties. Subsequent in vivo tests using a murine arthritis model validated the superior anti-inflammatory efficacy of the prepared DEX-bearing conjugates with lower release rates. These nanomedicines showed much higher therapeutic activity compared to the faster release systems or DEX itself.

Therapeutic activity and biodistribution of a nano-sized polymer-dexamethasone conjugate intended for the targeted treatment of rheumatoid arthritis

Rheumatoid arthritis is a chronic inflammatory autoimmune disease caused by alteration of the immune system. Current therapies have several limitations and the use of nanomedicines represents a promising strategy to overcome them. By employing a mouse model of adjuvant induced arthritis, we aimed to evaluate the biodistribution and therapeutic effects of glucocorticoid dexamethasone conjugated to a nanocarrier based on biocompatible N-(2-hydroxypropyl) methacrylamide copolymers. We observed an increased accumulation of dexamethasone polymer nanomedicines in the arthritic mouse paw using non-invasive fluorescent in vivo imaging and confirmed it by the analysis of tissue homogenates. The dexamethasone conjugate exhibited a dose-dependent healing effect on arthritis and an improved therapeutic outcome compared to free dexamethasone. Particularly, significant reduction of accumulation of RA mediator RANKL was observed. Overall, our data suggest that the conjugation of dexamethasone to a polymer nanocarrier by means of stimuli-sensitive spacer is suitable strategy for improving rheumatoid arthritis therapy.

A forskolin-mediated increase in cAMP promotes T helper cell differentiation into the Th1 and Th2 subsets rather than into the Th17 subset

The adenylyl cyclase (AC) signaling pathway is suggested to be a key regulator of immune system functions. However, specific effects of cyclic adenosine monophosphate (cAMP) on T helper (Th) cell differentiation and functions are unclear. The involvement of cAMP in the Th cell differentiation program, in particular the development of Th1, Th2, and Th17 subsets, was evaluated employing forskolin (FSK), a labdane diterpene well known as an AC activator. FSK mediated an elevation in Th1-specific markers reinforcing the Th1 cell phenotype. The Th2 differentiation was supported by FSK, though cell metabolism was negatively affected. In contrast, the Th17 immunophenotype was severely suppressed leading to the highly specific upregulation of CXCL13. The causality between FSK-elicited cAMP production and the observed reinforcement of Th2 differentiation was established by using AC inhibitor 2',5'-dideoxyadenosine, which reverted the FSK effects. Overall, an FSK-mediated cAMP increase affects Th1, Th2 and Th17 differentiation and can contribute to the identification of novel therapeutic targets for the treatment of Th cell-related pathological processes.

An in vitro model that mimics the foreign body response in the peritoneum: Study of the bioadhesive properties of HA-based materials

A cascade of reactions known as the foreign body response (FBR) follows the implantation of biomaterials leading to the formation of a fibrotic capsule around the implant and subsequent health complications. The severity of the FBR is driven mostly by the physicochemical characteristics of implanted material, the method and place of implantation, and the degree of immune system activation. Here we present an in vitro model for assessing new materials with respect to their potential to induce a FBR in the peritoneum. The model is based on evaluating protein sorption and cell adhesion on the implanted material. We tested our model on the free-standing films prepared from hyaluronan derivatives with different hydrophobicity, swelling ratio, and rate of solubilization. The proteomic analysis of films incubated in the mouse peritoneum showed that the presence of fibrinogen was driving the cell adhesion. Neither the film surface hydrophobicity/hydrophilicity nor the quantity of adsorbed proteins were decisive for the induction of the long-term cell adhesion leading to the FBR, while the dissolution rate of the material proved to be a crucial factor. Our model thus helps determine the probability of a FBR to materials implanted in the peritoneum while limiting the need for in vivo animal testing.

Luminal Surface Plasma Treatment of Closed Cylindrical Microchannels: A Tool toward the Creation of On-Chip Vascular Endothelium

On-chip vascular microfluidic models provide a great tool to study aspects of cardiovascular diseases in vitro. To produce such models, polydimethylsiloxane (PDMS) has been the most widely used material. For biological applications, its hydrophobic surface has to be modified. The major approach has been plasma-based surface oxidation, which has been very challenging in the case of channels enclosed within a microfluidic chip. The preparation of the chip combined a 3D-printed mold with soft lithography and commonly available materials. We have introduced the high-frequency low-pressure air-plasma surface modification of seamless channels enclosed within a PDMS microfluidic chip. The plasma treatment modified the luminal surface more uniformly than in previous works. Such a setup enabled a higher degree of design freedom and a possibility of rapid prototyping. Further, plasma treatment in combination with collagen IV coating created a biomimetic surface for efficient adhesion of vascular endothelial cells as well as promoted long-term cell culture stability under flow. The cells within the channels were highly viable and showed physiological behavior, confirming the benefit of the presented surface modification.

Molecular weight and gut microbiota determine the bioavailability of orally administered hyaluronic acid

The ability of hyaluronan as a dietary supplement to increase skin moisture and relieve knee pain has been demonstrated in several clinical studies. To understand the mechanism of action, determining hyaluronan's bioavailability and in vivo fate is crucial. Here, we used ¹³C-hyaluronan combined with LC-MS analysis to compare the absorption and metabolism of oral hyaluronan in germ-free and conventional wild-type mice. The presence of Bacteroides spp. in the gut was crucial for hyaluronan absorption. Specific microorganisms cleave hyaluronan into unsaturated oligosaccharides (<3 kDa) which are partially absorbed through the intestinal wall. The remaining hyaluronan fragments are metabolized into short-chain fatty acids, which are only metabolites available to the host. The poor bioavailability (~0.2 %) of oral hyaluronan indicates that the mechanism of action is the result of the systematic regulatory function of hyaluronan or its metabolites rather than the direct effects of hyaluronan at distal sites of action (skin, joints).

Convergent Assembly of the Tricyclic Labdane Core Enables Synthesis of Diverse Forskolin-like Molecules

We report a new synthetic strategy for the flexible preparation of forskolin-like molecules. The approach is different from the previously published works and employs a convergent assembly of the tricyclic labdane-type core from pre-functionalized cyclic building blocks. Stereoselective Michael addition enabled the fragment coupling with excellent control over three newly created contiguous stereocenters, all-carbon quaternary centers included. Silyl enol ether-promoted ring-opening metathesis paired with ring closure were the other key steps enabling concise assembly of the tricyclic core. Late-stage functionalization sequences transformed the tricyclic intermediates into a set of different forskolin-like molecules. The modular nature of the synthetic scheme described herein has the potential to become a general platform for the preparation of analogs of forskolin and other complex tricyclic labdanes.

Intraperitoneally administered native and lauroyl-modified hyaluronan films: Pharmacokinetic and metabolism studies

Hyaluronan is being investigated extensively as a biocompatible and biodegradable material for use in biomedical applications. While the derivatization of hyaluronan broadens its potential therapeutic use, the pharmacokinetics and metabolization of the derivatives must be thoroughly investigated. The fate of intraperitoneally-applied native and lauroyl-modified hyaluronan films with varying degrees of substitution was investigated in-vivo employing an exclusive stable isotope-labelling approach and LC-MS analysis. The materials were gradually degraded in peritoneal fluid, lymphatically absorbed, preferentially metabolized in the liver and eliminated without any observable accumulation in the body. Hyaluronan acylation prolongs its presence in the peritoneal cavity depending on the degree of substitution. The safety of acylated hyaluronan derivatives was confirmed via a metabolic study that revealed its degradation into non-toxic metabolites, i.e. native hyaluronan and free fatty acid. Stable isotope-labelling with LC-MS tracking comprises a high-quality procedure for the investigation of the metabolism and biodegradability of hyaluronan-based medical products in-vivo.

Single-cell RNA sequencing analysis of T helper cell differentiation and heterogeneity

Single-cell transcriptomics has emerged as a powerful tool to investigate cells' biological landscape and focus on the expression profile of individual cells. Major advantage of this approach is an analysis of highly complex and heterogeneous cell populations, such as a specific subpopulation of T helper cells that are known to differentiate into distinct subpopulations. The need for distinguishing the specific expression profile is even more important considering the T cell plasticity. However, importantly, the universal pipelines for single-cell analysis are usually not sufficient for every cell type. Here, the aims are to analyze the diversity of T cell phenotypes employing classical in vitro cytokine-mediated differentiation of human T cells isolated from human peripheral blood by single-cell transcriptomic approach with support of labelled antibodies and a comprehensive bioinformatics analysis using combination of Seurat, Nebulosa, GGplot and others. The results showed high expression similarities between Th1 and Th17 phenotype and very distinct Th2 expression profile. In a case of Th2 highly specific marker genes SPINT2, TRIB3 and CST7 were expressed. Overall, our results demonstrate how donor difference, Th plasticity and cell cycle influence the expression profiles of distinct T cell populations. The results could help to better understand the importance of each step of the analysis when working with T cell single-cell data and observe the results in a more practical way by using our analyzed datasets.

Myeloperoxidase Deficiency Alters the Process of the Regulated Cell Death of Polymorphonuclear Neutrophils

Polymorphonuclear neutrophils (PMNs) play a key role in host defense. However, their massive accumulation at the site of inflammation can delay regenerative healing processes and can initiate pathological inflammatory processes. Thus, the efficient clearance of PMNs mediated by the induction of regulated cell death is a key process preventing the development of these pathological conditions. Myeloperoxidase (MPO), a highly abundant enzyme in PMN granules, primarily connected with PMN defense machinery, is suggested to play a role in PMN-regulated cell death. However, the contribution of MPO to the mechanisms of PMN cell death remains incompletely characterized. Herein, the process of the cell death of mouse PMNs induced by three different stimuli – phorbol 12-myristate 13-acetate (PMA), opsonized streptococcus (OST), and N-formyl-met-leu-phe (fMLP) – was investigated. MPO-deficient PMNs revealed a significantly decreased rate of cell death characterized by phosphatidylserine surface exposure and cell membrane permeabilization. An inhibitor of MPO activity, 4-aminobenzoic acid hydrazide, did not exhibit a significant effect on PMA-induced cell death compared to MPO deficiency. Interestingly, only the limited activation of markers related to apoptotic cell death was observed (e.g. caspase 8 activation, Bax expression) and they mostly did not correspond to phosphatidylserine surface exposure. Furthermore, a marker characterizing autophagy, cleavage of LC3 protein, as well as histone H3 citrullination and its surface expression was observed. Collectively, the data show the ability of MPO to modulate the life span of PMNs primarily through the potentiation of cell membrane permeabilization and phosphatidylserine surface exposure.

Retinoic Acid Grafted to Hyaluronic Acid Activates Retinoid Gene Expression and Removes Cholesterol from Cellular Membranes

All-trans-retinoic acid (atRA) is a potent ligand that regulates gene expression and is used to treat several skin disorders. Hyaluronic acid (HA) was previously conjugated with atRA (HA-atRA) to obtain a novel amphiphilic compound. HA-atRA forms micelles that incorporate hydrophobic molecules and facilitate their transport through the skin. The aim of this study was to determine the influence of HA-atRA on gene expression in skin cells and to compare it with that of unbound atRA. Gene expression was investigated using microarrays and a luciferase system with a canonical atRA promoter. HA-atRA upregulated gene expression similarly to atRA. However, HA-atRA activated the expression of cholesterol metabolism genes, unlike atRA. Further investigation using HPLC and filipin III staining suggested that the treated cells induced cholesterol synthesis to replenish the cholesterol removed from the cells by HA-atRA. HA modified with oleate (HA-C18:1) removed cholesterol from the cells similarly to HA-atRA, suggesting that the cholesterol removal stemmed from the amphiphilic nature of the two derivatives. HA-atRA induces retinoid signaling. Thus, HA-atRA could be used to treat skin diseases, such as acne and psoriasis, where the combined action of atRA signaling and anti-inflammatory cholesterol removal may be potentially beneficial.

Conductive Polymer PEDOT:PSS-Based Platform for Embryonic Stem-Cell Differentiation

Organic semiconductors are constantly gaining interest in regenerative medicine. Their tunable physico-chemical properties, including electrical conductivity, are very promising for the control of stem-cell differentiation. However, their use for combined material-based and electrical stimulation remains largely underexplored. Therefore, we carried out a study on whether a platform based on the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) can be beneficial to the differentiation of mouse embryonic stem cells (mESCs). The platform was prepared using the layout of a standard 24-well cell-culture plate. Polyethylene naphthalate foil served as the substrate for the preparation of interdigitated gold electrodes by physical vapor deposition. The PEDOT:PSS pattern was fabricated by precise screen printing over the gold electrodes. The PEDOT:PSS platform was able to produce higher electrical current with the pulsed-direct-current (DC) electrostimulation mode (1 Hz, 200 mV/mm, 100 ms pulse duration) compared to plain gold electrodes. There was a dominant capacitive component. In proof-of-concept experiments, mESCs were able to respond to such electrostimulation by membrane depolarization and elevation of cytosolic calcium. Further, the PEDOT:PSS platform was able to upregulate cardiomyogenesis and potentially inhibit early neurogenesis per se with minor contribution of electrostimulation. Hence, the present work highlights the large potential of PEDOT:PSS in regenerative medicine.

Insoluble hyaluronan films obtained by heterogeneous crosslinking with iron(III) as resorbable implants

We present water-insoluble hyaluronan films crosslinked by trivalent iron developed as potential resorbable implants. The films were crosslinked by sorption of ferric salt into solid HA films in water/2-propanol bath. These heterogeneously crosslinked films (het-FeHA) remained tough and dimensionally stable when rehydrated in saline. In contrast, films prepared by drying the well-known homogeneous ferric hyaluronate gels (hom-FeHA) softened upon rehydration and expanded rapidly. Differences between hom-FeHA and het-FeHA result from polymer network topology (dominant inter- or intra-molecular crosslink, respectively). Moreover, Mössbauer spectroscopy of het-FeHA revealed diiron complexes, while iron in the hom-FeHA was present exclusively as γ-FeOOH nanoparticles or amorphous FeOOH. The biocompatibility tests of het-FeHA did not show any adverse effect and the sample disintegrated within one day when implanted in mice peritoneum. In conclusion, we developed implantable hyaluronan-based free-standing film with minimal swelling that can be resorbed quickly enough to avoid induction of foreign-body reaction.

Pseurotin D Induces Apoptosis through Targeting Redox Sensitive Pathways in Human Lymphoid Leukemia Cells

Chronic lymphocytic leukemia (CLL) is the most prevalent lymphoid malignancy in many geographical regions of the world. Pseurotin D, a secondary metabolite of fungi, represents a group of bioactive natural products with a newly ascribed range of interesting biological activities. The purpose of this study was to bring new insights into the mechanism behind the effects of pseurotin D on MEC-1 cells as a representative CLL cell line, with a particular focus on selected signaling pathways important in the proliferation of cells and targeting mitochondrial metabolism. Our results showed that pseurotin D was able to significantly inhibit the proliferation of MEC-1 cells and arrested them in the G2/M cell cycle phase. In addition, pseurotin D was able to induce apoptosis. We found that all of these effects were associated with a change in mitochondrial membrane potential and the production of mitochondrial reactive oxygen species (ROS). We showed for the first time that pseurotin D suppresses MEC-1 cell proliferation and induces apoptotic cell death via induction of the collapse of the mitochondria respiratory chain and the ROS-related caspase pathway. Our results show the pseurotins family as promising compounds which could serve as a basis for the development of new compounds in the treatment of lymphoma.

Effect of Apixaban Pretreatment on Alteplase-Induced Thrombolysis: An In Vitro Study

Benefit of thrombolytic therapy in patients with acute stroke, who are on anticoagulant treatment, is not well addressed. The aim of this study was to investigate whether apixaban can modify the thrombolytic efficacy of alteplase in vitro. Static and flow models and two variants of red blood cell (RBC) dominant clots, with and without apixaban, were used. Clots were prepared from the blood of healthy human donors and subsequently exposed to alteplase treatment. Apixaban and alteplase were used in clinically relevant concentrations. Clot lysis in the static model was determined both by clot weight and spectrophotometric determination of RBC release. Clot lysis in the flow model was determined by measuring recanalization time, clot length and spectrophotometric determination of RBC release. In the static model, clots without apixaban; compared to those with apixaban had alteplase-induced mass loss 54 ± 8% vs. 53 ± 8%, p = 1.00; RBC release 0.14 ± 0.04 vs. 0.12 ± 0.04, p = 0.14, respectively. Very similar results were obtained if plasma was used instead of physiological buffered saline as the incubation medium. In the flow model, clot lysis without apixaban; compared to those with apixaban was as follows: recanalization time 107 ± 46 min vs. 127 ± 31 min, p = 1.00; recanalization frequency 90 ± 22% vs. 90 ± 22%, p = 1.00; clot volume reduction 32 ± 15% vs. 34 ± 10%, p = 1.00; RBC release 0.029 ± 0.007 vs. 0.022 ± 0.007, p = 0.16, respectively. Apixaban had no positive effect on alteplase-induced thrombolysis in both the in vitro static and flow models. Our data support current clinical practice, such that thrombolysis is contraindicated in stroke treatment for patients who have been treated with anticoagulants.

How the molecular weight affects the in vivo fate of exogenous hyaluronan delivered intravenously: A stable-isotope labelling strategy

There is inconsistent information regarding the size effects of exogenously given hyaluronan on its in vivo fate. The data are often biased by the poor quality of hyaluronan and non-ideal labelling strategies used for resolving exogenous/endogenous hyaluronan, which only monitor the label and not hyaluronan itself. To overcome these drawbacks and establish the pharmacokinetics of intravenous hyaluronan in relation to its Mw, 13C-labelled HA of five Mws from 13.6-1562 kDa was prepared and administered to mice at doses 25-50 mg kg-1. The elimination efficiency increased with decreasing Mw. Low Mw hyaluronan was rapidly eliminated as small hyaluronan fragments in urine, while high Mw hyaluronan exhibited saturable kinetics and complete metabolization within 48 h. All tested Mws exhibited a similar uptake by liver cells and metabolization into activated sugars. 13C-labelling combined with LC-MS provides an excellent approach to elucidating in vivo fate and biological activities of hyaluronan.

Myeloperoxidase mediated alteration of endothelial function is dependent on its cationic charge

Endothelial cell (EC) glycocalyx (GLX) comprise a multicomponent layer of proteoglycans and glycoproteins. Alteration of its integrity contributes to chronic vascular inflammation and leads to the development of cardiovascular diseases. Myeloperoxidase (MPO), a highly abundant enzyme released by polymorphonuclear neutrophils, binds to the GLX and deleteriously affects vascular EC functions. The focus of this study was to elucidate the mechanisms of MPO-mediated alteration of GLX molecules, and to unravel subsequent changes in endothelial integrity and function. MPO binding to GLX of human ECs and subsequent internalization was mediated by cell surface heparan sulfate chains. Moreover, interaction of MPO, which is carrying a cationic charge, with anionic glycosaminoglycans (GAGs) resulted in reduction of their relative charge. By means of micro-viscometry and atomic force microscopy, we disclosed that MPO can crosslink GAG chains. MPO-dependent modulation of GLX structure was further supported by alteration of wheat germ agglutinin staining. Increased expression of ICAM-1 documented endothelial cell activation by both catalytically active and also inactive MPO. Furthermore, MPO increased vascular permeability connected with reorganization of intracellular junctions, however, this was dependent on MPO's catalytic activity. Novel proteins interacting with MPO during transcytosis were identified by proteomic analysis. Altogether, these findings provide evidence that MPO through interaction with GAGs modulates overall charge of the GLX, causing modification of its structure and thus affecting EC function. Importantly, our results also suggest a number of proteins interacting with MPO that possess a variety of cellular localizations and functions.

12-O-Tetradecanoylphorbol-13-acetate increases cardiomyogenesis through PKC/ERK signaling

12-O-Tetradecanoylphorbol-13-acetate (TPA) is the most widely used diacylglycerol (DAG) mimetic agent and inducer of protein kinase C (PKC)-mediated cellular response in biomedical studies. TPA has been proposed as a pluripotent cell differentiation factor, but results obtained have been inconsistent. In the present study we show that TPA can be applied as a cardiomyogenesis-promoting factor for the differentiation of mouse embryonic stem (mES) cells in vitro. The mechanism of TPA action is mediated by the induction of extracellular signal-regulated kinase (ERK) activity and the subsequent phosphorylation of GATA4 transcription factor. Interestingly, general mitogens (FGF, EGF, VEGF and serum) or canonical WNT signalling did not mimic the effect of TPA. Moreover, on the basis of our results, we postulate that a TPA-sensitive population of cardiac progenitor cells exists at a certain time point (after days 6–8 of the differentiation protocol) and that the proposed treatment can be used to increase the multiplication of ES cell-derived cardiomyocytes.

The Role of Dietary Phenolic Compounds in Epigenetic Modulation Involved in Inflammatory Processes

A better understanding of the interactions between dietary phenolic compounds and the epigenetics of inflammation may impact pathological conditions and their treatment. Phenolic compounds are well-known for their antioxidant, anti-inflammatory, anti-angiogenic, and anti-cancer properties, with potential benefits in the treatment of various human diseases. Emerging studies bring evidence that nutrition may play an essential role in immune system modulation also by altering gene expression. This review discusses epigenetic mechanisms such as DNA methylation, post-translational histone modification, and non-coding microRNA activity that regulate the gene expression of molecules involved in inflammatory processes. Special attention is paid to the molecular basis of NF-κB modulation by dietary phenolic compounds. The regulation of histone acetyltransferase and histone deacetylase activity, which all influence NF-κB signaling, seems to be a crucial mechanism of the epigenetic control of inflammation by phenolic compounds. Moreover, chronic inflammatory processes are reported to be closely connected to the major stages of carcinogenesis and other non-communicable diseases. Therefore, dietary phenolic compounds-targeted epigenetics is becoming an attractive approach for disease prevention and intervention.

Cyanobacterial lipopeptides puwainaphycins and minutissamides induce disruptive and pro-inflammatory processes in Caco-2 human intestinal barrier model

Puwainaphycins (PUW) and minutissamides (MIN) are cyanobacterial lipopeptides found in various cyanobacterial species. The first possible target of human exposure to them is intestinal epithelium but effect of PUW/MIN on enterocytes is not known at all. Using differentiated Caco-2 cells, PUW F was found to be cytotoxic from 5 µM concentration based on lactate dehydrogenase release assay and total protein concentration. However, it is also able to induce production of interleukin 8 in non-cytotoxic concentrations 1 and 2.5 µM detected by ELISA. Effects of MIN A and C were similar but less pronounced compared to PUW F. On the other hand, MIN D was the least toxic compound with no significant pro-inflammatory effects. Surprisingly, pro-inflammatory activation of the cells by PUW F and MIN C resulted in an increase in tight junction (TJ) protein claudin 4 expression determined by western blot analysis and confirmed by confocal microscopy. Furthermore, decrease in expression of zonula occludens 3, another TJ protein, was observed after the exposure to PUW F. Taken together, these cytotoxic lipopeptides, especially PUW F, are to be studied more deeply due to their capability to activate and/or deregulate human enterocytes in low concentrations.

Natural pseurotins and analogs thereof inhibit activation of B-cells and differentiation into the plasma cells

BACKGROUND

The frequency of allergic diseases is constantly rising. Dysregulated production of isotype E immunoglobulins is one of the key factors behind allergic reactions and its modulation is therefore an important target for pharmacological intervention. Natural products of the pseurotin family were reported to be inhibitors of IgE production in B-cells. Mechanistic details underlying these effects are however not well understood.

PURPOSE

In the present study, we synthesized new analogs of natural pseurotins and extensively investigated their inhibitory effects on activation, proliferation and differentiation of B-cells, as well as on the production of IgE.

STUDY DESIGN

Effects of two natural pseurotins (pseurotins A and D) and a collection of fully synthetic pseurotin analogs were studied on mouse B-cells stimulated by the combination of IL-4 and E. coli lipopolysaccharide. The IgE production was determined along with cell viability and cell proliferation. The phosphorylation of selected members of the STAT transcription factor family was subsequently investigated. Finally, the in vivo effect of pseurotin D on the ovalbumin-induced delayed type hypersensitivity response was tested in mice.

RESULTS

We discovered that several fully synthetic pseurotin analogs were able to decrease the production of IgE in stimulated B-cells with potency comparable to that of pseurotins A and D. We found that the two natural pseurotins and the active synthetic analogs inhibited the phosphorylation of STAT3, STAT5 and STAT6 proteins in stimulated B-cells, resulting in the inhibition of B-cell proliferation and differentiation into the plasma cells. In vivo, pseurotin D decreased ovalbumin-induced foot pad edema.

CONCLUSION

Our results advance the current mechanistic understanding of the pseurotin-induced inhibition of IgE production in B-cells by linking the effect to STAT signaling, and associated modulation of B-cell proliferation and differentiation. Together with our finding that structurally simpler pseurotin analogs were able to reproduce the effects of natural pseurotins, the presented work has implications for the future research on these secondary metabolites in the context of allergic diseases.

The depletion of p38alpha kinase upregulates NADPH oxidase 2/NOX2/gp91 expression and the production of superoxide in mouse embryonic stem cells

P38alpha kinase plays an important role in the regulation of both cell stress response and cell fate. In this study, we report that p38alpha kinase-deficient embryonic stem cells exhibit a higher production of reactive oxygen species (ROS) in contrast to their wild-type counterpart. Analysis of the expressions of NADPH oxidases (NOXs) and dual oxidases, crucial enzymes involved in intracellular ROS formation, shows NOX2/gp91^phox is over-expressed in p38alpha deficient cells. The particular increase in superoxide formation was confirmed by the specific detection of hydroethidine derivate 2-hydroxyethidium. ROS formation decreased when the level of NOX2 was silenced by siRNA in p38alpha deficient cells. These data suggest the importance of p38alpha kinase in the regulation of ROS metabolism in embryonic stem cells and the significance of the observed phenomena of cancer cell-like phenotypes, which is discussed.