A novel tool to characterize paracellular transport: the APTS-dextran ladder

A Review on Microengineering of Epithelial Barriers for Biomedical and Pharmaceutical Research

Epithelial tissue forms a barrier around the human body and visceral organs, providing protection, permeation, sensation, and secretion. It is vital for our sustenance as it protects the tissue from harm and injury by restricting the entry of foreign bodies inside. Furthermore, it is a strong barrier to drugs, nutrients, and other essential deliverables. This layer also houses a large consortium of microbes, which thrive in tandem with human tissue, providing several health benefits. Moreover, the complex interplay of the microbiome with the barrier tissue is poorly understood. Therefore, replicating these barrier tissues on microdevices to generate physiological and pathophysiological models has been a huge interest for researchers over the last few decades. The artificially engineered reconstruction of these epithelial cellular barriers on microdevices could help underpin the host-microbe interaction, generating a physiological understanding of the tissue, tissue remodeling, receptor-based selective diffusion, drug testing, and others. In addition, these devices could reduce the burden of animal sacrifices for similar research and minimize the failure rate in drug discovery due to the use of primary human cells and others. This review discusses the nature of the epithelial barrier at different tissue sites, the recent developments in creating engineered barrier models, and their applications in pathophysiology, host-microbe interactions, drug discovery, and cytotoxicity. The review aims to provide know-how and knowledge behind engineered epithelial barrier tissue to bioengineers, biotechnologists, and scientists in allied fields.

Progress and prospects of polysaccharide-based nanocarriers for oral delivery of proteins/peptides

The oral route has long been recognized as the most preferred route for drug delivery as it offers high patient compliance and requires minimal expertise. Unlike small molecule drugs, the harsh environment of the gastrointestinal tract and low permeability across the intestinal epithelium make oral delivery extremely ineffective for macromolecules. Accordingly, delivery systems that are rationally constructed with suitable materials to overcome barriers to oral delivery are exceptionally promising. Among the most ideal materials are polysaccharides. Depending on the interaction between polysaccharides and proteins, the thermodynamic loading and release of proteins in the aqueous phase can be realized. Specific polysaccharides (dextran, chitosan, alginate, cellulose, etc.) endow systems with functional properties, including muco-adhesiveness, pH-responsiveness, and prevention of enzymatic degradation. Furthermore, multiple groups in polysaccharides can be modified, which gives them a variety of properties and enables them to suit specific needs. This review provides an overview of different types of polysaccharide-based nanocarriers based on different kinds of interaction forces and the influencing factors in the construction of polysaccharide-based nanocarriers. Strategies of polysaccharide-based nanocarriers to improve the bioavailability of orally administered proteins/peptides were described. Additionally, current restrictions and future trends of polysaccharide-based nanocarriers for oral delivery of proteins/peptides were also covered.

In Vitro Methods for Measuring the Permeability of Cell Monolayers

Cell monolayers, including endothelial and epithelial cells, play crucial roles in regulating the transport of biomolecules to underlying tissues and structures via intercellular junctions. Moreover, the monolayers form a semipermeable barrier across which leukocyte transmigration is tightly regulated. The inflammatory cytokines can disrupt the epithelial and endothelial permeability, thus the reduced barrier integrity is a hallmark of epithelial and endothelial dysfunction related with numerous pathological conditions, including cancer-related inflammation. Therefore, the assessment of barrier function is critical in in vitro models of barrier-forming tissues. This review summarizes the commercially available in vitro systems used to measure the permeability of cellular monolayers. The presented techniques are separated in two large groups: macromolecular tracer flux assays, and electrical impedance measurement-based permeability assays. The presented techniques are briefly described and compared.

Oral absorption characteristics and mechanisms of a pectin-type polysaccharide from Smilax china L. across the intestinal epithelium

The elucidation of the oral absorption of natural polysaccharides contributes to their further research and utilization. Herein, to explore the absorption of a pectin-type polysaccharide from Smilax china L. (SCLP), SCLP was respectively fluorescently labeled with fluorescein-5-thioicarbazide (FSCLP) and Cyanine7 amine (Cy7-SCLP) for in vitro and in vivo tracking. The near-infrared imaging demonstrated that Cy7-SCLP was absorbable in the small intestine and distributed in the liver and kidney after oral administration. Subsequently, in vitro intestinal epithelial tissue experiments showed that the jejunum was the dominant site of FSCLP transport. Further transport studies in the Caco-2 cell monolayer illustrated that FSCLP was delivered across the monolayer via transcellular transport by caveolae-mediated endocytosis and macropinocytosis together with paracellular transport by reversibly affecting tight junctions. In summary, this work presents the oral absorption characteristics and mechanisms of SCLP through the intestinal epithelium, which will facilitate the further development of SCLP and pectin polysaccharides.

Assessing the impacts on fetal dosimetry of the modelling of the placental transfers of xenobiotics in a pregnancy physiologically based pharmacokinetic model

The developmental origin of health and diseases theory supports the critical role of the fetal exposure to children's health. We developed a physiologically based pharmacokinetic model for human pregnancy (pPBPK) to simulate the maternal and fetal dosimetry throughout pregnancy. Four models of the placental exchanges of chemicals were assessed on ten chemicals for which maternal and fetal data were available. These models were calibrated using non-animal methods: in vitro (InV) or ex vivo (ExV) data, a semi-empirical relationship (SE), or the limitation by the placental perfusion (PL). They did not impact the maternal pharmacokinetics but provided different profiles in the fetus. The PL and InV models performed well even if the PL model overpredicted the fetal exposure for some substances. The SE and ExV models showed the lowest global performance and the SE model a tendency to underprediction. The comparison of the profiles showed that the PL model predicted an increase in the fetal exposure with the pregnancy age, whereas the ExV model predicted a decrease. For the SE and InV models, a small decrease was predicted during the second trimester. All models but the ExV one, presented the highest fetal exposure at the end of the third trimester. Global sensitivity analyses highlighted the predominant influence of the placental transfers on the fetal exposure, as well as the metabolic clearance and the fraction unbound. Finally, the four transfer models could be considered depending on the framework of the use of the pPBPK model and the availability of data or resources to inform their parametrization.

In Vitro Models of the Blood-Brain Barrier

Knowledge about the transport of active compounds across the blood-brain barrier is of essential importance for drug development. Systemically applied drugs for the central nervous system (CNS) must be able to cross the blood-brain barrier in order to reach their target sites, whereas drugs that are supposed to act in the periphery should not permeate the blood-brain barrier so that they do not trigger any adverse central adverse effects. A number of approaches have been pursued, and manifold in silico, in vitro, and in vivo animal models were developed in order to be able to make a better prediction for humans about the possible penetration of active substances into the CNS. In this particular case, however, in vitro models play a special role, since the data basis for in silico models is usually in need of improvement, and the predictive power of in vivo animal models has to be checked for possible species differences. The blood-brain barrier is a dynamic, highly selective barrier formed by brain capillary endothelial cells. One of its main tasks is the maintenance of homeostasis in the CNS. The function of the barrier is regulated by cells of the microenvironment and the shear stress mediated by the blood flow, which makes the model development most complex. In general, one could follow the credo "as easy as possible, as complex as necessary" for the usage of in vitro BBB models for drug development. In addition to the description of the classical cell culture models (transwell, hollow fiber) and guidance how to apply them, the latest developments (spheroids, microfluidic models) will be introduced in this chapter, as it is attempted to get more in vivo-like and to be applicable for high-throughput usage with these models. Moreover, details about the development of models based on stem cells derived from different sources with a special focus on human induced pluripotent stem cells are presented.

Transport Studies Using Blood-Brain Barrier In Vitro Models: A Critical Review and Guidelines

Permeation is one of the most evaluated parameters using preclinical in vitro blood-brain barrier models, as it has long been considered to be one of the major factors influencing central nervous system drug delivery. Blood-brain barrier permeability can be defined as the speed at which a compound crosses the brain endothelial cell barrier and is employed to assess barrier tightness, which is a crucial feature of brain capillaries in vivo. In addition, it is used to assess brain drug penetration. We review traditionally used methods to assess blood-brain barrier permeability in vitro and summarize often neglected in vivo (e.g., plasma protein and brain tissue binding) or in vitro (e.g., culture insert materials or methodology) factors that influence this property. These factors are crucial to consider when performing BBB permeability assessments, and especially when comparing permeability data obtained from different models, since model diversification significantly complicates inter-study comparisons. Finally, measuring transendothelial electrical resistance can be used to describe blood-brain barrier tightness; however, several parameters should be considered while comparing these measurements to the blood-brain barrier permeability to paracellular markers.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Multifaceted Mechanisms of WY-14643 to Stabilize the Blood-Brain Barrier in a Model of Traumatic Brain Injury

The blood-brain barrier (BBB) is damaged during ischemic insults such as traumatic brain injury or stroke. This contributes to vasogenic edema formation and deteriorate disease outcomes. Enormous efforts are pursued to understand underlying mechanisms of ischemic insults and develop novel therapeutic strategies. In the present study the effects of PPARα agonist WY-14643 were investigated to prevent BBB breakdown and reduce edema formation. WY-14643 inhibited barrier damage in a mouse BBB in vitro model of traumatic brain injury based on oxygen/glucose deprivation in a concentration dependent manner. This was linked to changes of the localization of tight junction proteins. Furthermore, WY-14643 altered phosphorylation of kinases ERK1/2, p38, and SAPK/JNK and was able to inhibit proteosomal activity. Moreover, addition of WY-14643 upregulated PAI-1 leading to decreased t-PA activity. Mouse in vivo experiments showed significantly decreased edema formation in a controlled cortical impact model of traumatic brain injury after WY-14643 application, which was not found in PAI-1 knockout mice. Generally, data suggested that WY-14643 induced cellular responses which were dependent as well as independent from PPARα mediated transcription. In conclusion, novel mechanisms of a PPARα agonist were elucidated to attenuate BBB breakdown during traumatic brain injury in vitro.

The pivotal role of astrocytes in an in vitro stroke model of the blood-brain barrier

Stabilization of the blood-brain barrier during and after stroke can lead to less adverse outcome. For elucidation of underlying mechanisms and development of novel therapeutic strategies validated in vitro disease models of the blood-brain barrier could be very helpful. To mimic in vitro stroke conditions we have established a blood-brain barrier in vitro model based on mouse cell line cerebEND and applied oxygen/glucose deprivation (OGD). The role of astrocytes in this disease model was investigated by using cell line C6. Transwell studies pointed out that addition of astrocytes during OGD increased the barrier damage significantly in comparison to the endothelial monoculture shown by changes of transendothelial electrical resistance as well as fluorescein permeability data. Analysis on mRNA and protein levels by qPCR, western blotting and immunofluorescence microscopy of tight junction molecules claudin-3,-5,-12, occludin and ZO-1 revealed that their regulation and localisation is associated with the functional barrier breakdown. Furthermore, soluble factors of astrocytes, OGD and their combination were able to induce changes of functionality and expression of ABC-transporters Abcb1a (P-gp), Abcg2 (bcrp), and Abcc4 (mrp4). Moreover, the expression of proteases (matrixmetalloproteinases MMP-2, MMP-3, MMP-9, and t-PA) as well as of their endogenous inhibitors (TIMP-1, TIMP-3, PAI-1) was altered by astrocyte factors and OGD which resulted in significant changes of total MMP and t-PA activity. Morphological rearrangements induced by OGD and treatment with astrocyte factors were confirmed at a nanometer scale using atomic force microscopy. In conclusion, astrocytes play a major role in blood-brain barrier breakdown during OGD in vitro.

Transport rankings of non-steroidal antiinflammatory drugs across blood-brain barrier in vitro models

The aim of this work was to conduct a comprehensive study about the transport properties of NSAIDs across the blood-brain barrier (BBB) in vitro. Transport studies with celecoxib, diclofenac, ibuprofen, meloxicam, piroxicam and tenoxicam were accomplished across Transwell models based on cell line PBMEC/C1-2, ECV304 or primary rat brain endothelial cells. Single as well as group substance studies were carried out. In group studies substance group compositions, transport medium and serum content were varied, transport inhibitors verapamil and probenecid were added. Resulted permeability coefficients were compared and normalized to internal standards diazepam and carboxyfluorescein. Transport rankings of NSAIDs across each model were obtained. Single substance studies showed similar rankings as corresponding group studies across PBMEC/C1-2 or ECV304 cell layers. Serum content, glioma conditioned medium and inhibitors probenecid and verapamil influenced resulted permeability significantly. Basic differences of transport properties of the investigated NSAIDs were similar comparing all three in vitro BBB models. Different substance combinations in the group studies and addition of probenecid and verapamil suggested that transporter proteins are involved in the transport of every tested NSAID. Results especially underlined the importance of same experimental conditions (transport medium, serum content, species origin, cell line) for proper data comparison.

Determination of pore sizes and relative porosity in porous nanoshell architectures using dextran retention with single monomer resolution and proton permeation

Unilamellar phospholipid vesicles prepared using the polymerizable lipid bis-sorbylphosphatidylcholine (bis-SorbPC) yield three-dimensional nanoarchitectures that are highly permeable to small molecules. The resulting porous phospholipid nanoshells (PPNs) are potentially useful for a range of biomedical applications including nanosensors and nanodelivery vehicles for cellular assays and manipulations. The uniformity and size distribution of the pores, key properties for sensor design and utilization, have not previously been reported. Fluorophore-assisted carbohydrate electrophoresis (FACE) was utilized to assess the nominal molecular weight cutoff limit (NMCL) of the PPN via analysis of retained dextran with single monomer resolution. The NMCL of PPNs prepared from pure bis-SorbPC was equivalent to a 1800 Da linear dextran, corresponding to a maximum pore diameter of 2.6 nm. Further investigation of PPNs prepared using binary mixtures of bis-SorbPC and dioleoylphosphatidylcholine (DOPC) revealed a similar NMCL when the bis-SorbPC content exceeded 30 mol %, whereas different size-dependent permeation was observed below this composition. Below 30 mol % bis-SorbPC, dextran retention provided insufficient mass resolution (162 Da) to observe porosity on the experimental time scale; however, proton permeability showed a marked enhancement for bis-SorbPC ≥ 10 mol %. Combined, these data suggest that the NMCL for native pores in bis-SorbPC PPNs results from an inherent property within the lipid assembly that can be partially disrupted by dilution of bis-SorbPC below a critical value for domain formation. Additionally, the analytical method described herein should prove useful for the challenging task of elucidating porosity in a range of three-dimensional nanomaterials.

Cereal β-glucan quantification with calcofluor-application to cell culture supernatants

The specific binding of the fluorescent dye calcofluor to cereal β-glucan results in increased fluorescence intensity of the formed complex and is in use for the quantification of β-glucan above a critical molecular weight (MW) by flow injection analysis. In this study, this method was applied in a fast and easy batch mode. In order to emphasize the spectral information of the emission spectra of the calcofluor/β-glucan complexes, derivative signals were calculated. A linear relationship was found between the amplitude of the second derivative signals and the β-glucan concentration between 0.1 and 0.4 μg/mL. The low detection limit of this new method (0.045 μg/mL) enabled its use to study the transport of cereal β-glucans over differentiated Caco-2 cell monolayers. Additionally, the method was applied to quantify β-glucan in arabinoxylan samples, which correlated well with data by an enzyme based method.

Stabilization of brain microvascular endothelial barrier function by shear stress involves VE-cadherin signaling leading to modulation of pTyr-occludin levels

Blood-brain barrier (BBB) regulation involves the coordinated interaction of intercellular adherens and tight junctions in response to stimuli. One such stimulus, shear stress, has been shown to upregulate brain microvascular endothelial cell (BMvEC) barrier function, although our knowledge of the signaling mechanisms involved is limited. In this article, we examined the hypothesis that VE-cadherin can transmit shear signals to tight junction occludin with consequences for pTyr-occludin and barrier function. In initial studies, chronic shear enhanced membrane localization of ZO-1 and claudin-5, decreased pTyr-occludin (in part via a dephostatin-sensitive mechanism), and reduced BMvEC permeability, with flow reduction in pre-sheared BMvECs having converse effects. In further studies, VE-cadherin inhibition (VE-cad ΔEXD) blocked shear-induced Rac1 activation, pTyr-occludin reduction, and barrier upregulation, consistent with an upstream role for VE-cadherin in transmitting shear signals to tight junctions through Rac1. As VE-cadherin is known to mediate Rac1 activation via Tiam1 recruitment, we subsequently confirmed that Tiam1 inhibition (Tiam1-C580) could elicit effects similar to VE-cad ΔEXD. Finally, the observed attenuation of shear-induced changes in pTyr-occludin level and barrier phenotype following Rac1 inhibition (NSC23766, T17N) establishes a downstream role for Rac1 in this pathway. In summary, we describe for the first time in BMvECs a role for VE-cadherin in the transmission of physiological shear signals to tight junction occludin through engagement of Tiam1/Rac1 leading to barrier stabilization. A downstream role is also strongly indicated for a protein tyrosine phosphatase in pTyr-occludin modulation. Importantly, these findings suggest an important route of inter-junctional signaling cross-talk during BBB response to flow.

Time lapse monitoring of CaCo-2 cell shapes and shape dependence of the distribution of integrin β1 and F-actin on their basal membrane

CaCo-2 cell line is a model system for cell differentiation. For the effective use of CaCo-2 cells, it is important to understand how their growth depends on environmental conditions. The authors grew them on laminin-1, fibronectin, and collagen-1 adsorbed to glass and polystyrene. The time lapse technique was applied to follow their growth and shape changes for 21.5 h post seeding. The results upgraded the auhtors' previous findings about the series of consecutive shape changes that occur post seeding. Most cells were initially rounded and then they changed shape in two directions. A smaller fraction of cells, which attained cumulus shapes, eventually detached and drifted away. Other cells attained a semispread, transient shape, which was followed by a fully spread shape that was dominant on all protein-coated surfaces. The average time over which cells changed their shape type was different on different surfaces. It was longer on protein-coated glass surfaces than on protein-coated polystyrene surfaces. On collagen-1-coated surfaces, cells spread in the shortest time. Different cell shape types exhibited different spatial distributions of integrin β1, F-actin, and focal adhesions.

Effects of NMDA receptor modulators on a blood-brain barrier in vitro model

Changes of the functionality of the blood-brain barrier (BBB) have been reported in the context of several brain related diseases such as multiple sclerosis, epilepsy, Alzheimer's disease and stroke. Several publications indicated the presence and functionality of the NMDA receptor (NMDAR) at the brain endothelium and a possible involvement of the NMDAR in the above-mentioned diseases. Recently, it was shown that the application of the NMDAR antagonist MK801 can block several adverse effects at the BBB in vitro, but also that MK801 can significantly change the proteome of brain endothelial cells without simultaneous stimulation of NMDAR by glutamate. Based on these reports we investigated if NMDAR antagonists MK801 and D-APV can affect the intracellular calcium level (Ca²⁺i) of an in vitro BBB model based on human cell line ECV304 on their own and compared these results to effects mediated by NMDAR agonists glutamate and NMDA. Treatment of ECV304 cells for 30 min with glutamate resulted in no significant change of Ca²⁺i. On the contrary, application of NMDA and NMDAR antagonists D-APV and MK801 led to a significant and concentration dependent decrease of Ca²⁺i. Further studies revealed that glutamate was able to decrease the transendothelial electrical resistance (TEER) of the BBB in vitro model, whereas NMDA and D-APV were able to increase TEER. Analysis of the protein expression levels of tight junctional molecules ZO-1 and occludin showed a complex regulation after application of NMDAR modulators. In summary, it was shown that NMDAR antagonists can alter BBB key properties in vitro on their own. Moreover, although qPCR results confirmed the presence of NMDA receptor subunits NR1, NR2A, NR2B and NR2C, membrane binding studies failed to prove the typical plasma membrane localization and functionality in human BBB cell line ECV304.

Curdione Plays an Important Role in the Inhibitory Effect of Curcuma aromatica on CYP3A4 in Caco-2 Cells

Curcuma aromatica is a plant belonging to genus Curcuma of family Zingiberaceae and is widely used as supplements in Japan. Rhizomes of C. aromatica have curcumin as a major yellow pigment and curdione as a main ingredient of essential oils. In this study, we investigated the affect of C. aromatica on CYP3A4 using 1α,25-(OH)₂-D₃-treated Caco-2 clone cells. Caco-2 cells were treated with methanol extract (0.1 mg ml⁻¹), its hexane soluble fraction (0.1 mg ml⁻¹), curcumin (4 μM) and curdione (20 μM) for 72 hours. Nifedipine was used as a substrate of CYP3A4. Methanol extract, hexane fraction and curdione inhibited the formation of oxidized nifedipine by 50–70%, and curcumin showed no effect. The IC50s of methanol extract, hexane fraction and curdione to oxidized nifedipine formation were 21, 14 and 3.9 μg ml⁻¹ (16.9 μM), respectively. The content of curdione in methanol extract was 11.4%. Moreover, all of methanol extract, hexane fraction and curdione decreased CYP3A4 protein expression but had no affect on CYP3A4 mRNA expression. Our results showed that these drugs further decreased the CYP3A4 protein expression level after the protein synthesis was inhibited by cychroheximide. These findings suggest that curdione plays an important role in the CYP3A4 inhibitory activity of C. aromatica and curdione might inhibit the activity by accelerating the degradation of CYP3A4.

Blood-brain barrier cell line PBMEC/C1-2 possesses functionally active P-glycoprotein

The blood-brain barrier (BBB) maintains the homeostasis between the central nervous system and the blood circulation. One of the main efflux transporter proteins at the BBB is P-glycoprotein (P-gP) also known as ABCB1 or MDR1. Due to the important role of P-gP for the transport barrier function of the BBB, the presence and functionality of P-gP was investigated in porcine cell line PBMEC/C1-2. Presence of P-gP was confirmed on the protein level by western blotting and immunofluorescence microscopy as well as on the mRNA level by qPCR. Functional assessment was accomplished by an established 96-well uptake assay using Rhodamine 123 and Doxorubicin as P-gP substrates and Verapamil as moderate P-gP inhibitor. In this regard, fluorescence microscopy confirmed a significant higher uptake of Rhodamine 123 into PBMEC/C1-2 cells when preincubated with Verapamil. Finally, knock-down of P-gP by antisense oligonucleotides revealed an increase of Rhodamine 123 uptake indicating decreased P-gP functionality. In summary, the presence and functionality of P-gP in the immortalised cell line PBMEC/C1-2 was proven with several techniques and assays. Thus, this cell line could be used for P-gP studies in the context of BBB relevant issues.

Validation of in vitro cell culture models of the blood-brain barrier: tightness characterization of two promising cell lines

In the course of the validation of blood-brain barrier in vitro models the aim of this work was to characterize two promising continuous cell lines with regard to their tightness properties. PBMEC/C1-2 and ECV304 cells were cultured in several media with different compositions on Transwell inserts. Inducibility and functionality of tightness were investigated by transendothelial electrical resistance (TEER) and by transport studies with transcellular marker diazepam, glycine antagonist Bu101 and paracellular marker APTS-dextran. Inducibility, expression and localization of tight junctional proteins were assessed by western blotting and immunofluorescence microscopy. Presence of factors derived from glioma cell line C6 resulted in increased TEER in both cell lines. Comparison to APTS-dextran data across Caco-2 layers emphasized that correlations between permeability of the paracellular marker and TEER are dependent on each investigated cell line and the corresponding growth medium. Presence and inducibility of tight junctional proteins ZO-1 and Occludin were proven for ECV304 layers. Cell line ECV304 seemed to be suitable for TEER dependent transport studies, whereas PBMEC/C1-2 showed higher potential for P-gP studies.

2'-O-Lysylaminohexyl oligonucleotides: modifications for antisense and siRNA

A novel type of oligonucleotide has been developed, characterized by the attachment of a lysyl moiety to a 2'-O-aminohexyl linker. A protected lysine building block was tethered to 2'-O-aminohexyluridine, and the product was converted into the corresponding phosphoramidite. Up to six modified nucleosides were incorporated in dodecamer DNA and RNA oligonucleotides using standard phosphoramidite chemistry. Each of the building blocks contributes one positive charge to the oligonucleotide instead of the negative charge of a wild-type nucleotide. Thermal denaturation profiles indicated a stabilizing effect of 2'-O-lysylaminohexyl chains that was more pronounced in RNA duplexes. Incubation of the oligonucleotides with 5'-exonuclease revealed an exceptionally high stability against enzymatic degradation. Incorporation of up to three modifications into functional antisense and siRNA oligonucleotides targeted at ICAM-1 showed that the gene-silencing activity was higher with an increasing number of lysylaminohexyl nucleotides. Compared with wild-type antisense or siRNA, compounds with three modifications led to equal or higher ICAM-1 downregulation.

Possible inhibitory mechanism of Curcuma drugs on CYP3A4 in 1α,25 dihydroxyvitamin D3 treated Caco-2 cells

Curcuma longa and C. zedoaria, belonging to genus Curcuma, have become prevalent as supplements in East Asia. Curcumin is the most well-studied bioactive component isolated from rhizomes of C. longa and other Curcuma species except C. zedoaria. In this study, we investigated the affects of C. longa, C. zedoaria from Japan and curcumin on CYP3A4. Caco-2 cells, in which CYP3A4 expression was induced by 1alpha,25-(OH)(2)-D(3), were used to mimic the metabolism of small intestine. Caco-2 cells were treated with methanol extracts from two Curcuma rhizomes (0.1mg/ml) or curcumin (30 microM) for 72 h. Both extracts significantly decreased the activity of CYP3A4 by about 85-98%. The 50% inhibitory concentrations of C. longa and C. zedoaria extracts were 0.019 and 0.014 mg/ml, respectively. They caused a 60-70% decrease in CYP3A4 protein. Otherwise, curcumin treatment caused a 30-40% decrease in CYP3A4 catalytic activity and a 38% decrease in CYP3A4 protein expression. Moreover, it was found that both Curcuma extracts and curcumin treatment had no influence on CYP3A4 mRNA expression. Our results suggested that administration of Curcuma drugs might inhibit the catalytic activity of intestinal CYP3A4. However, curcumin was not the major compound responsible for this inhibitory effect.

Restoration of barrier function in injured intestinal mucosa

Mucosal repair is a complex event that immediately follows acute injury induced by ischemia and noxious luminal contents such as bile. In the small intestine, villous contraction is the initial phase of repair and is initiated by myofibroblasts that reside immediately beneath the epithelial basement membrane. Subsequent events include crawling of healthy epithelium adjacent to the wound, referred to as restitution. This is a highly regulated event involving signaling via basement membrane integrins by molecules such as focal adhesion kinase and growth factors. Interestingly, however, ex vivo studies of mammalian small intestine have revealed the importance of closure of the interepithelial tight junctions and the paracellular space. The critical role of tight junction closure is underscored by the prominent contribution of the paracellular space to measures of barrier function such as transepithelial electrical resistance. Additional roles are played by subepithelial cell populations, including neutrophils, related to their role in innate immunity. The net result of reparative mechanisms is remarkably rapid closure of mucosal wounds in mammalian tissues to prevent the onset of sepsis.