Applications of the Caco-2 model in the design and development of orally active drugs: elucidation of biochemical and physical barriers posed by the intestinal epithelium

Amifostine loaded lipid-calcium carbonate nanoparticles as an oral drug delivery system for radiation protection

Amifostine (AMF) as the first-line radiation protection drug, usually suffered from low compliance and short half-life upon clinical applications. The development of oral drug delivery system (DDS) for AMF is a promising solution. However, the inherent shortages of AMF present significant challenges in the design of suitable oral DDS. Here in this study, we utilized the ability of calcium ions to bind with AMF and prepared AMF loaded calcium carbonate (CC) core, CC/AMF, using phase transferred coprecipitation method. We further modified the CC/AMF using phospholipids to prepare AMF loaded lipid-calcium carbonate (LCC) hybrid nanoparticles (LCC/AMF) via a thin-film dispersion method. LCC/AMF combines the oral advantages of lipid nanoparticles with the drug-loading capabilities of CC, which was shown as uniform nano-sized formulation with decent stability in aqueous solution. With favorable intestinal transport and absorption effects, it effectively enhances the in vivo radiation protection efficacy of AMF through oral administration. More importantly, we further investigated the cellular accumulation profile and intracellular transport mechanism of LCC/AMF using MDCK and Caco-2 cell lines as models. This research not only alters the current administration method of AMF to enhance its convenience and compliance, but also provides insights and guidance for the development of more suitable oral DDS for AMF in the future.

Quantifying the transport of biologics across intestinal barrier models in real-time by fluorescent imaging

Unsuccessful clinical translation of orally delivered biological drugs remains a challenge in pharmaceutical development and has been linked to insufficient mechanistic understanding of intestinal drug transport. Live cell imaging could provide such mechanistic insights by directly tracking drug transport across intestinal barriers at subcellular resolution, however traditional intestinal in vitro models are not compatible with the necessary live cell imaging modalities. Here, we employed a novel microfluidic platform to develop an in vitro intestinal epithelial barrier compatible with advanced widefield- and confocal microscopy. We established a quantitative, multiplexed and high-temporal resolution imaging assay for investigating the cellular uptake and cross-barrier transport of biologics while simultaneously monitoring barrier integrity. As a proof-of-principle, we use the generic model to monitor the transport of co-administrated cell penetrating peptide (TAT) and insulin. We show that while TAT displayed a concentration dependent difference in its transport mechanism and efficiency, insulin displayed cellular internalization, but was restricted from transport across the barrier. This illustrates how such a sophisticated imaging based barrier model can facilitate mechanistic studies of drug transport across intestinal barriers and aid in vivo and clinical translation in drug development.

Enhanced stability and oral bioavailability of erlotinib by solid self nano emulsifying drug delivery systems

The present investigation demonstrates the preparation of solid self nanoemulsfying drug delivery system (sSNEDDS) to enhance stability and bioavailability of Erlotinib (ERL) via the oral route. Capmul®MCM EP (CPM EP, oil), Cremophor® RH 40 (CMR RH 40, surfactant), and LBF CS (LBF CS, cosurfactant) were chosen as chief components for preparing Liquids SNEDDS (L-ERL-SNEDDS) based on solubility and emulsion forming ability. Pseudo ternary phase diagram and constrained mixture designs were applied to identify the self-emulsifying area and it was found that CPM EP, CMR RH 40, and LBF CS in the ratio of 59:11:30 showed optimized particle size (110.08 nm), with narrow PDI (0.114) and high ERL loading capacity (14.31 mg/g). Adsorption method was implemented for solidification of L-ERL-SNEDDS. Among various solid carriers were studied, Aerosil® 200 (A200) was finalized based on free flowing property and reconstitution ability. DSC and XRD studies revealed that crystallinity of drug was reduced in developed system. The developed formulation (named as, A200-ERL-sSNEDDS) showed increased cytotoxicity and apoptosis in PANC-1 and MIA PaCa-2 cells. Pharmacokinetic studies revealed ∼2.2 times increase in AUC0-∞values in case of A200-ERL-sSNEDDS as compared to free ERL. Thus current strategy can be extrapolated for delivering of poorly soluble drugs via oral route.

Application of Fucoidan in Caco-2 Model Establishment

The Caco-2 model is a common cell model for material intestinal absorption in vitro, which usually takes 21 days to establish. Although some studies have shown that adding puromycin (PM) can shorten the model establishment period to 7 days, this still requires a long modeling time. Therefore, exploring a shorter modeling method can reduce the experimental costs and promote the development and application of the model. Fucoidan is an acidic polysaccharide with various biological activities. Our study showed that the transepithelial electrical resistance (TEER) value could reach 600 Ω·cm2 on the fourth day after the addition of fucoidan and puromycin, which met the applicable standards of the model (>500 Ω). Moreover, the alkaline phosphatase (AKP) activity, fluorescein sodium transmittance, and cell morphology of this model all met the requirements of model establishment. Fucoidan did not affect the absorption of macromolecular proteins and drugs. The results indicate that fucoidan can be applied to establish the Caco-2 model and can shorten the model establishment period to 5 days.

Chlorothalonil induces the intestinal epithelial barrier dysfunction in Caco-2 cell-based in vitro monolayer model by activating MAPK pathway

The widespread use of chlorothalonil (CTL) has caused environmental residues and food contamination. Although the intestinal epithelial barrier (IEB) is directly involved in the metabolism and transportation of various exogenous compounds, there are few studies on the toxic effects of these compounds on the structure and function of IEB. The disassembly of tight junction (TJ) is a major cause of intestinal barrier dysfunction under exogenous compounds intake, but the precise mechanisms are not well understood. Here, we used Caco-2 cell monolayers as an in vitro model of human IEB to evaluate the toxicity of CTL exposure on the structure and function of IEB. Results showed that CTL exposure increased the paracellular permeability of the monolayers and downregulated mRNA levels of the TJ genes (ZO-1, OCLN, and CLDN1), polarity marker gene (SI), and anti-apoptosis gene (BCL-2) but upregulated the mRNA levels of apoptosis-related genes, including BAD, BAX, CASP3, and CASP8. Western blot analysis and immunofluorescence assay results showed the decreased levels and disrupted distribution of TJ protein network, including ZO-1 and CLDN1 in CTL-exposed IEB. In addition, the accumulation of intracellular reactive oxygen species, decreased mitochondrial membrane potential, and increased active CASP3 expression were observed in treated IEB. The result of TUNEL assay further confirmed the occurrence of cell apoptosis after CTL exposure. In addition, the phosphorylation of mitogen-activated protein kinases, including ERK, JNK and p38, was increased in CTL-exposed IEB. In summary, our results demonstrated that CTL exposure induced IEB dysfunction in Caco-2 cell monolayers by activating the mitogen-activated protein kinase pathway.

Nanoemulsion for Improving the Oral Bioavailability of Hesperetin: Formulation Optimization and Absorption Mechanism

This study aimed to prepare a nanoemulsion vehicle to improve the oral bioavailability of hesperetin. The pseudo-ternary phase diagrams and the RSM were used to optimize nanoemulsion parameters. Compared with hesperetin suspension, the AUC_0-t and C_max of nanoemulsion were increased by 5.67-fold and 2.64-fold, respectively. The proportion of lymphatic transport reached 87.72%, the cumulative absorption amount of jejunum, ileum, and duodenum increased by 1.1-fold, 1.92-fold, and 1.5-fold, respectively. The results implied that hesperetin nanoemulsion could effectively improve the bioavailability of hesperetin by increasing lymphatic transport and enhancing intestinal permeability. Therefore, nanoemulsion is a potential method to improve the bioavailability of hesperetin, which has strong practicability.

Salidroside as a potential neuroprotective agent for ischemic stroke: a review of sources, pharmacokinetics, mechanism and safety

Salidroside (Sal) is a bioactive extract principally from traditional herbal medicine such as Rhodiola rosea L., which has been commonly used for hundreds of years in Asia countries. The excellent neuroprotective capacity of Sal has been illuminated in recent studies. This work focused on the source, pharmacokinetics, safety and anti-ischemic stroke (IS) effect of Sal, especially emphasizing its mechanism of action and BBB permeability. Extensive databases, including Pubmed, Web of science (WOS), Google Scholar and China National Knowledge Infrastructure (CNKI), were applied to obtain relevant online literatures. Sal exerts powerful therapeutic effects on IS in experimental models either in vitro or in vivo due to its neuroprotection, with significantly diminishing infarct size, preventing cerebral edema and improving neurological function. Also, the findings suggest the underlying mechanisms involve anti-oxidation, anti-inflammation and anti-apoptosis by regulating multiple signaling pathways and key molecules, such as NF-κB, TNF-α and PI3K/Akt pathway. In pharmacokinetics, although showing a rapid absorption and elimination, bioavailability of Sal is elevated under some non-physiological conditions. The component and its metabolite (tyrosol) are capable of distributing to brain tissue and the later keeps a higher level of concentration. Moreover, Sal scarcely has obvious toxicity or side effects in a variety of animal experiments and clinical trials, but combination of drugs and perinatal use of medicine should be taken more attentions. Finally, as an active ingredient, not only is Sal isolated from diverse plants with limited yield, but also large batches of the products can be harvested by biological and chemical synthesis. With higher efficacy and better safety profiles, Sal could sever as a promising neuroprotectant for preventing and treating IS. Nevertheless, further investigations are still required to explore the pharmacodynamic and pharmacokinetic properties of Sal in the treatment of IS.

Changes of the glutathione redox system during the weaning transition in piglets, in relation to small intestinal morphology and barrier function

Background

Weaning is known to result in barrier dysfunction and villus atrophy in the immediate post-weaning phase, and the magnitude of these responses is hypothesized to correlate with changes in the glutathione (GSH) redox system. Therefore, these parameters were simultaneously measured throughout the weaning phase, in piglets differing in birth weight category and weaning age, as these pre-weaning factors are important determinants for the weaning transition. Low birth weight (LBW) and normal birth weight (NBW) littermates were assigned to one of three weaning treatments; i.e. weaning at 3 weeks of age (3w), weaning at 4 weeks of age (4w) and removal from the sow at 3 d of age and fed a milk replacer until weaning at 3 weeks of age (3d3w). For each of these treatments, six LBW and six NBW piglets were euthanized at 0, 2, 5, 12 or 28 d post-weaning piglets, adding up 180 piglets.

Results

Weaning increased the glutathione peroxidase activity on d 5 post-weaning in plasma, and duodenal and jejunal mucosa. Small intestinal glutathione-S-transferase activity gradually increased until d 12 post-weaning, and this was combined with a progressive rise of mucosal GSH up till d 12 post-weaning. Oxidation of the GSH redox status (GSH/GSSG E_h) was only observed in the small intestinal mucosa of 3d3w weaned piglets at d 5 post-weaning. These piglets also demonstrated increased fluorescein isothiocyanate dextran (FD4) and horseradish peroxidase fluxes in the duodenum and distal jejunum during the experiment, and specifically demonstrated increased FD4 fluxes at d 2 to d 5 post-weaning. On the other hand, profound villus atrophy was observed during the weaning transition for all weaning treatments. Finally, LBW and NBW piglets did not demonstrate notable differences in GSH redox status, small intestinal barrier function and histo-morphology throughout the experiment.

Conclusion

Although moderate changes in the GSH redox system were observed upon weaning, the GSH redox status remained at a steady state level in 3w and 4w weaned piglets and was therefore not associated with weaning induced villus atrophy. Conversely, 3d3w weaned piglets demonstrated GSH redox imbalance in the small intestinal mucosa, and this co-occurred with a temporal malfunction of their intestinal barrier function.

ADMET profiling of geographically diverse phytochemical using chemoinformatic tools

Aim: Phytocompounds are important due to their uniqueness, however, only few reach the development phase due to their poor pharmacokinetics. Therefore, preassessing the absorption, distribution, metabolism, excretion and toxicity (ADMET) properties is essential in drug discovery. Methodology: Biologically diverse databases (Phytochemica, SerpentinaDB, SANCDB and NuBBE_DB) covering the region of India, Brazil and South Africa were considered to predict the ADMET using chemoinformatic tools (Qikprop, pkCSM and DataWarrior). Results: Screening through each of pharmacokinetic criteria resulted in identification of 24 compounds that adhere to all the ADMET properties. Furthermore, assessment revealed that five have potent anticancer biological activity against cancer cell lines. Conclusion: We have established an open-access database (ADMET-BIS) to enable identification of promising molecules that follow ADMET properties and can be considered for drug development.

Bioinspired Engineering of Organ-on-Chip Devices

The human body can be viewed as an organism consisting of a variety of cellular and non-cellular materials interacting in a highly ordered manner. Its complex and hierarchical nature inspires the multi-level recapitulation of the human body in order to gain insights into the inner workings of life. While traditional cell culture models have led to new insights into the cellular microenvironment and biological control in vivo, deeper understanding of biological systems and human pathophysiology requires the development of novel model systems that allow for analysis of complex internal and external interactions within the cellular microenvironment in a more relevant organ context. Engineering organ-on-chip systems offers an unprecedented opportunity to unravel the complex and hierarchical nature of human organs. In this chapter, we first highlight the advances in microfluidic platforms that enable engineering of the cellular microenvironment and the transition from cells-on-chips to organs-on-chips. Then, we introduce the key features of the emerging organs-on-chips and their proof-of-concept applications in biomedical research. We also discuss the challenges and future outlooks of this state-of-the-art technology.

Graphene Quantum Dots Downregulate Multiple Multidrug-Resistant Genes via Interacting with Their C-Rich Promoters

Multidrug resistance (MDR) is the major factor in the failure of many forms of chemotherapy, mostly due to the increased efflux of anticancer drugs that mediated by ATP-binding cassette (ABC) transporters. Therefore, inhibiting ABC transporters is one of effective methods of overcoming MDR. However, high enrichment of ABC transporters in cells and their broad substrate spectra made to circumvent MDR are almost insurmountable by a single specific ABC transporter inhibitor. Here, this study demonstrates that graphene quantum dots (GQDs) could downregulate the expressions of P-glycoprotein, multidrug resistance protein MRP1, and breast cancer resistance protein genes via interacting with C-rich regions of their promoters. This is the first example that a single reagent could suppress multiple MDR genes, suggesting that it will be possible to target multiple ABC transporters simultaneously with a single reagent. The inhibitory ability of the GQDs to these drug-resistant genes is validated further by reversing the doxorubicin resistance of MCF-7/ADR cells. Notably, GQDs have superb chemical and physical properties, unique structure, low toxicity, and high biocompatibility; hence, their capability of inhibiting multiple drug-resistant genes holds great potential in cancer therapy.

Application of the rainbow trout derived intestinal cell line (RTgutGC) for ecotoxicological studies: molecular and cellular responses following exposure to copper

There is an acknowledged need for in vitro fish intestinal model to help understand dietary exposure to chemicals in the aquatic environment. The presence and use of such models is however largely restrictive due to technical difficulties in the culturing of enterocytes in general and the availability of appropriate established cell lines in particular. In this study, the rainbow trout (Oncorhynchus mykiss) intestinal derived cell line (RTgutGC) was used as a surrogate for the "gut sac" method. To facilitate comparison, RTgutGC cells were grown as monolayers (double-seeded) on permeable Transwell supports leading to a two-compartment intestinal model consisting of polarised epithelium. This two-compartment model divides the system into an upper apical (lumen) and a lower basolateral (portal blood) compartment. In our studies, these cells stained weakly for mucosubstances, expressed the tight junction protein ZO-1 in addition to E-cadherin and revealed the presence of polarised epithelium in addition to microvilli protrusions. The cells also revealed a comparable transepithelial electrical resistance (TEER) to the in vivo situation. Importantly, the cell line tolerated apical saline (1:1 ratio) thus mimicking the intact organ to allow assessment of uptake of compounds across the intestine. Following an exposure over 72 h, our study demonstrated that the RTgutGC cell line under sub-lethal concentrations of copper sulphate (Cu) and modified saline solutions demonstrated uptake of the metal with saturation levels comparable to short term ex situ gut sac preparations. Gene expression analysis revealed no significant influence of pH or time on mRNA expression levels of key stress related genes (i.e. CYP3A, GST, mtA, Pgp and SOD) in the Transwell model. However, significant positive correlations were found between all genes investigated suggesting a co-operative relationship amongst the genes studied. When the outlined characteristics of the cell line are combined with the division of compartments, the RTgutGC double seeded model represents a potential animal replacement model for ecotoxicological studies. Overall, this model could be used to study the effects and predict aquatic gastrointestinal permeability of metals and other environmentally relevant contaminants in a cost effective and high throughput manner.

Intestinal absorption mechanisms of 2'-deoxy-2'-β-fluoro-4'-azidocytidine, a cytidine analog for AIDS treatment, and its interaction with P-glycoprotein, multidrug resistance-associated protein 2 and breast cancer resistance protein

2'-Deoxy-2'-β-fluoro-4'-azidocytidine (FNC), a cytidine analog, has attracted great interest because of its potent activity against wild-type and multidrug-resistant HIV. The purpose of current study was to investigate the absorption mechanisms of FNC in the small intestine, as well as the interactions between FNC and P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP). The experiments were performed using Caco-2 cells and the rat small intestine. The uptake experiment indicated that FNC concentration, extracellular pH and the incubated temperature could influence the uptake of FNC in Caco-2 cells. NaN₃, verapamil, probenecid, MK571 and GF120918 could significantly increase the FNC uptake in Caco-2 cells. The transport experiment showed that both the absorption and secretion of FNC were concentration dependent. The secretion of FNC was approximately 2-fold greater than the absorption. In the presence of verapamil, probenecid, MK571 or GF120918, the efflux ratio decreased by >50%. In everted rat intestine, the absorption of FNC also depended on its concentration and was not significantly different in the different segments of the small intestine. Real-time RT-PCR results indicated that the gene expressions of P-gp, MRP2 and BCRP were up-regulated after exposure to FNC. The reduction in accumulation of rhodamine 123 after treatment with FNC revealed its ability to up-regulate P-gp activity. In conclusion, FNC was completely absorbed by passive diffusion and active transport mechanisms. P-gp, MRP2 and BCRP could influence the absorption of FNC in the small intestine. FNC could modulate the gene expressions of P-gp, MRP2 and BCRP, and increase the activity of P-gp.

Highly Potent, Selective, and Orally Bioavailable 4-Thiazol-N-(pyridin-2-yl)pyrimidin-2-amine Cyclin-Dependent Kinases 4 and 6 Inhibitors as Anticancer Drug Candidates: Design, Synthesis, and Evaluation

Cyclin D dependent kinases (CDK4 and CDK6) regulate entry into S phase of the cell cycle and are validated targets for anticancer drug discovery. Herein we detail the discovery of a novel series of 4-thiazol-N-(pyridin-2-yl)pyrimidin-2-amine derivatives as highly potent and selective inhibitors of CDK4 and CDK6. Medicinal chemistry optimization resulted in 83, an orally bioavailable inhibitor molecule with remarkable selectivity. Repeated oral administration of 83 caused marked inhibition of tumor growth in MV4-11 acute myeloid leukemia mouse xenografts without having a negative effect on body weight and showing any sign of clinical toxicity. The data merit 83 as a clinical development candidate.

Isolation and in vitro permeation of phenylpropylamino alkaloids from Khat (Catha edulis) across oral and intestinal mucosal tissues

ETHNOPHARMACOLOGICAL RELEVANCE

Khat, the leaves of Catha edulis, is used as a "natural amphetamine-like" stimulant in eastern and southern Africa, as well as in the Arabian Peninsula. Leaves are masticated to elicit a state of euphoria. Although the psychostimulatory effects of the leaves are attributed to the presence of phenylpropylamino alkaloids (i.e. cathinone, cathine and norephedrine), the extent of permeation of these alkaloids across the oral and intestinal mucosa has not been established.

MATERIALS AND METHODS

Cathinone was isolated in the form of the oxalate salt from young buds, following acid-base extraction. High performance countercurrent chromatography (HPCCC) was used to isolate cathine and norephedrine, following borohydride reduction of a mixture of the three alkaloids. The in vitro permeability of these three alkaloids in their pure form, as well as in a crude extract, was evaluated across Caco-2 cell monolayers and across excised porcine intestinal, sublingual and buccal tissues.

RESULTS

The purities of the isolated cathine and norephedrine were in excess of 90%, thereby proving that HPCCC can be applied for efficient separation of these alkaloids from extracts of Khat. The apparent permeability (P_app) coefficients for the Khat alkaloids in their pure form were all above 1.0×10^-6cm/s, indicating that the transport of the three alkaloids across the selected biological membranes is comparable to that of the highly permeable reference compound, caffeine. Although readily transported across the various membranes, the alkaloids were transported to a lesser extent when present in a leaf extract, suggesting that other phytochemicals present in the extract influence their permeation.

CONCLUSIONS

These results provide evidence that chewing of Khat contributes to the buccal and sublingual absorption of the psychoactive alkaloids in the bloodstream directly across the oral mucosal membranes. In addition, it confirms that these metabolites will be readily absorbed from the gastrointestinal tract when swallowed.

Complex, multi-scale small intestinal topography replicated in cellular growth substrates fabricated via chemical vapor deposition of Parylene C

Native small intestine possesses distinct multi-scale structures (e.g., crypts, villi) not included in traditional 2D intestinal culture models for drug delivery and regenerative medicine. The known impact of structure on cell function motivates exploration of the influence of intestinal topography on the phenotype of cultured epithelial cells, but the irregular, macro- to submicron-scale features of native intestine are challenging to precisely replicate in cellular growth substrates. Herein, we utilized chemical vapor deposition of Parylene C on decellularized porcine small intestine to create polymeric intestinal replicas containing biomimetic irregular, multi-scale structures. These replicas were used as molds for polydimethylsiloxane (PDMS) growth substrates with macro to submicron intestinal topographical features. Resultant PDMS replicas exhibit multiscale resolution including macro- to micro-scale folds, crypt and villus structures, and submicron-scale features of the underlying basement membrane. After 10 d of human epithelial colorectal cell culture on PDMS substrates, the inclusion of biomimetic topographical features enhanced alkaline phosphatase expression 2.3-fold compared to flat controls, suggesting biomimetic topography is important in induced epithelial differentiation. This work presents a facile, inexpensive method for precisely replicating complex hierarchal features of native tissue, towards a new model for regenerative medicine and drug delivery for intestinal disorders and diseases.

In vitro oral drug permeation models: the importance of taking physiological and physico-chemical factors into consideration

INTRODUCTION

The assessment of intestinal membrane permeability properties of new chemical entities is a crucial step in the drug discovery and development process and a variety of in vitro models, methods and techniques are available to estimate the extent of oral drug absorption in humans. However, variations in certain physiological and physico-chemical factors are often not reflected in the results and the complex dynamic interplay between these factors is sometimes oversimplified with in vitro models. Areas covered: In vitro models to evaluate drug pharmacokinetics are briefly outlined, while both physiological and physico-chemical factors that may have an influence on these techniques are critically reviewed. The shortcomings identified for some of the in vitro techniques are discussed in conjunction with novel ways to improve and thereby overcome some challenges. Expert opinion: Although conventional in vitro methods and theories are used as basic guidelines to predict drug absorption, critical evaluations have identified some shortcomings. Advancements in technology have made it possible to investigate and understand the role of physiological and physico-chemical factors in drug delivery more clearly, which can be used to improve and refine the techniques to more closely mimic the in vivo environment.

Developments in Methods for Measuring the Intestinal Absorption of Nanoparticle-Bound Drugs

With the rapid development of nanotechnology, novel drug delivery systems comprising orally administered nanoparticles (NPs) have been paid increasing attention in recent years. The bioavailability of orally administered drugs has significant influence on drug efficacy and therapeutic dosage, and it is therefore imperative that the intestinal absorption of oral NPs be investigated. This review examines the various literature on the oral absorption of polymeric NPs, and provides an overview of the intestinal absorption models that have been developed for the study of oral nanoparticles. Three major categories of models including a total of eight measurement methods are described in detail (in vitro: dialysis bag, rat gut sac, Ussing chamber, cell culture model; in situ: intestinal perfusion, intestinal loops, intestinal vascular cannulation; in vivo: the blood/urine drug concentration method), and the advantages and disadvantages of each method are contrasted and elucidated. In general, in vitro and in situ methods are relatively convenient but lack accuracy, while the in vivo method is troublesome but can provide a true reflection of drug absorption in vivo. This review summarizes the development of intestinal absorption experiments in recent years and provides a reference for the systematic study of the intestinal absorption of nanoparticle-bound drugs.

Intestinal absorption characteristics of imperialine: in vitro and in situ assessments

AIM

Imperialine is an effective compound in the traditional Chinese medicine chuanbeimu (Bulbus Fritillariae Cirrhosae) that has been used as antitussive/expectorant in a clinical setting. In this study we investigated the absorption characteristics of imperialine in intestinal segments based on an evaluation of its physicochemical properties.

METHODS

Caco-2 cells were used to examine uptake and transport of imperialine in vitro, and a rat in situ intestinal perfusion model was used to characterize the absorption of imperialine. The amount of imperialine in the samples was quantified using LC-MS/MS.

RESULTS

The aqueous solubility and oil/water partition coefficient of imperialine were determined. This compound demonstrated a relatively weak alkalinity with a pKa of 8.467±0.028. In Caco-2 cells, the uptake of imperialine was increased with increasing pH in medium, but not affected by temperature. The apparent absorptive and secretive coefficient was (8.39±0.12)×10(-6) cm/s and (7.78±0.09)×10(-6) cm/s, respectively. Furthermore, neither the P-glycoprotein inhibitor verapamil nor Niemann-Pick C1-Like 1 transporter inhibitor ezetimibe affected the absorption and secretion of imperialine in vitro. The in situ intestinal perfusion study showed that the absorption parameters of imperialine varied in 4 intestinal segments (duodenum, jejunum, ileum and colon) with the highest ones in the colon, where a greater number of non-ionized form of imperialine was present.

CONCLUSION

The intestinal absorptive characteristics of imperialine are closely related to its physicochemical properties. The passive membrane diffusion dominates the intestinal absorption of imperialine.

In vitro micro-physiological models for translational immunology

The immune system is a source of regulation of the human body and is key for its stable functioning. Animal models have been successfully used for many years to study human immunity and diseases and provided significant contributions to the development of powerful new therapies. However, such models inevitably display differences from the human metabolism and disease state and therefore may correlate poorly with the human conditions. This explains the interest for the use of in vitro models of human cells, which have better potential to assist in understanding the physiological events that characterize the immune response in humans. Microfluidic technologies offer great capabilities to create miniaturized in vivo-like physiological models that mimic tissue-tissue interactions and simulate the body metabolism in both the healthy and diseased states. The micro-scale features of these microfluidic systems allow positioning heterogeneous cellular cultures in close proximity to each other in a dynamic fluidic environment, thereby allowing efficient cell-cell interactions and effectively narrowing the gap between in vivo and in vitro conditions. Due to the relative simplicity of these systems, compared to animal models, it becomes possible to investigate cell signaling by monitoring the metabolites transported from one tissue to another in real time. This allows studying detailed physiological events and in consequence understanding the influence of metabolites on a specific tissue/organ function as well as on the healthy/diseased state modulation. Numerous in vitro models of human organs have been developed during the last few years, aiming to mimic as closely as possible the in vivo characteristics of such organs. This technology is still in its infancy, but is promised a bright future in industrial and medical applications. Here we review the recent literature, in which functional microphysiological models have been developed to mimic tissues and to explore multi-tissue interactions, focusing in particular on the study of immune reactions, inflammation and the development of diseases. Also, an outlook on the opportunities and issues for further translational development of functional in vitro models in immunology will be presented.

Synthesis and controlled curcumin supramolecular complex release from pH-sensitive modified gum-arabic-based hydrogels

Delivery of a curcumin supramolecular complex from pH-responsive gum arabic-based hydrogels.

Synthesis and Caco-2 cell permeability of N-substituted anthranilamide esters as ADP inhibitor in platelets

Twelve N-substituted anthranilamide esters (1-5, 8, 9, 12, 13, and 15-17) were synthesized and evaluated for their ability to inhibit the in vitro aggregation by washed human platelets induced by adenosine 5'-diphosphate (10 μM). The antiplatelet activity of DL-n-butyl 5-hydroxy-N-(2-phenoxypropionyl)anthranilate (9, IC50 = 10.5 μM) was most active among the tested compounds and ethyl ester 8 (IC50 = 11.2 μM) showed the second most activity. DL-Ethyl and DL-n-butyl 5-(p-toluenesulfonyloxy)-N-(2-phenoxypropionyl)anthranilate (12, IC50 = 13.1 μM and 13, IC50 = 14.0 μM), DL-methyl N-(2-phenoxybutyryl)anthranilate (2, IC50 = 12.7 μM), DL-N-(2-phenoxypropionyl)anthranilic acid (5, IC50 = 13.7 μM) displayed lower antiplatelet activity than 8 and 9. Compound 5 was more active than methyl ester prodrug 1. n-Butyl 5-hydroxy-N-(4'-acetoxybenzoyl)anthranilate (15, IC50 = 28.3 μM) showed moderate activity. Compounds 1 (IC50 = 42.8 μM), 4 (IC50 = 56.7 μM), 16 (IC50 = 51.0 μM), and 17 (IC50 = 49.8 μM) exhibited low antiplatelet activity. Methyl N-phenoxyacetylanthranilate (3, IC50 = 78.0 μM) showed the lowest antiplatelet activity. The compounds with branched alkyl chain (2 and 5) were more active than compounds with straight chain (3 and 4). The apparent permeability coefficient (Papp, cm/s) values of compounds 2 and 9 were determined as 45.34 ± 4.67 and 33.17 ± 5.15 × 10(-6) cm/s by Caco-2 cell permeability assay.

Black rice and anthocyanins induce inhibition of cholesterol absorption in vitro

Black rice (Oryza sativa L.) is often associated with blood lipid control. This study systematically assessed the inhibition of cholesterol absorption in vitro by black rice and explored cholesterol-lowering compounds present in this rice. Our results indicated that black rice extracts (BRE), which were aqueous, ethanol extracts and a fraction of macroporous resin caused the reduction of cholesterol absorption by inhibiting pancreatic lipase, decreasing the micellar cholesterol solubility and suppressing cholesterol uptake in Caco-2 cells. The inhibitory activity was positively associated with anthocyanin (cyanidin-3-glucoside (Cy-3-G) and peonidin-3-glucoside (Pn-3-G)) contents of the extracts. Therefore, the cholesterol absorption inhibiting properties of anthocyanins were further explored. The IC50 values of Cy-3-G and Pn-3-G against pancreatic lipase were 42.53 ± 4.45 and 18.13 ± 4.22 μg mL(-1), respectively. Kinetic analysis suggested that the enzymatic inhibitory mode of Cy-3-G and Pn-3-G belonged to the competitive type. In mixed micelles, Cy-3-G and Pn-3-G dose dependently reduced the solubility of cholesterol. Meanwhile, a potential mechanism of cholesterol reduction by anthocyanins was investigated. Results showed that anthocyanins led to precipitation of cholesterol from micellar solution, which may induce the reduction of cholesterol. In Caco-2 cells, Cy-3-G and Pn-3-G (40 μg mL(-1)) exhibited a significant reduction in cholesterol uptake, and the degree of this reduction was almost the same as that observed in the group treated with Ezetimibe at the same concentration. These findings provide important evidence that anthocyanins may partly contribute to the inhibitory effects of black rice on cholesterol absorption, and thus may be applied for the prevention and treatment of hypercholesterolaemia.

Esterification enhanced intestinal absorption of ginsenoside Rh2 in Caco-2 cells without impacts on its protective effects against H₂O₂-induced cell injury in human umbilical vein endothelial cells (HUVECs)

Ginsenoside Rh2 and its octyl ester derivative (Rh2-O) were investigated for their transcellular transport in the Caco-2 cell system and their protective effect against oxidative stress in human umbilical vein endothelial cells (HUVECs). Results showed that the transport rates for apical-to-basolateral (AP-BL) flux of Rh2 (0.21 × 10⁻⁶ cm/s) was enhanced by the synthesis of its esterified derivative Rh2-O (1.93 × 10⁻⁶ cm/s) over the concentrations of 10-50 μM. In addition, both Rh2 and its esterified derivative Rh2-O exhibited similar protective effects against oxidative damage induced by H₂O₂. Pretreatment of Rh2 and Rh2-O significantly decreased the activation of caspase-3 known to play a key role in H₂O₂-induced cell apoptosis. These results were consistent with that of a flow cytometry assay analyzing HUVECs apoptosis. The present study demonstrated that the absorption of ginsenoside Rh2 in vitro can be significantly enhanced by synthesis of its ester derivative. Meanwhile, no significant discrepancy between Rh2 and Rh2-O on their bioactivities against the oxidative damage induced by H₂O₂ was observed, which means that esterification of Rh2 might have a higher bioavailability than Rh2 in vitro without impacts on pharmaceutical actions.

Microfluidic chip for monitoring Ca2+transport through a confluent layer of intestinal cells

Microfluidic-based Caco-2 culture model provides a useful tool for investigating of metabolites transport and nutrikinetics studies.

Absorption mechanism of ginsenoside compound K and its butyl and octyl ester prodrugs in Caco-2 cells

Ginsenoside compound K (CK) is a bioactive compound with poor oral bioavailability due to its high polarity, while its novel ester prodrugs, the butyl and octyl ester (CK-B and CK-O), are more lipophilic than the original drug and have an excellent bioavailability. The aim of this study was to examine the transport mechanisms of CK, CK-B, and CK-O using human Caco-2 cells. Results showed that CK had a low permeability coefficient (8.65 × 10(-7) cm/s) for apical-to-basolated (AP-BL) transport at 10-50 μM, while the transport rate for AP to BL flux of CK-B (2.97 × 10(-6) cm/s) and CK-O (2.84 × 10(-6) cm/s) was significantly greater than that of CK. Furthermore, the major transport mechanism of CK was found as passive transcellular diffusion with active efflux mediated by P-glycoprotein (P-gp). In addition, it was found that CK-B and CK-O were not the substrate of efflux transporter since the selective inhibitors (verapamil and MK-571) of efflux transporter had little effects on the transport of CK-B and CK-O in the Caco-2 cells. These results suggest that improving the lipophilicity of CK by acylation can significantly improve the transport across Caco-2 cells.

Forms of selenium affect its transport, uptake and glutathione peroxidase activity in the Caco-2 cell model

The experiment was designed to investigate the effect of selenium (Se) chemical forms (sodium selenite, selenium nanoparticle [nano-Se] and selenomethionine) on the transport, uptake and glutathione peroxidase (GSH-Px) activity in the Caco-2 cell model. The transport and uptake of different forms of Se (0.1 μmol l(-1)) across the Caco-2 cell monolayer were carried out in two directions (apical [AP] to basolateral [BL] and BL to AP) for 2 h, respectively, and the apparent permeability coefficient (P(app)), transport efficiency and uptake efficiency were all calculated. In the present study, the transport and uptake of three forms of Se were time-dependent both in AP to BL and BL to AP directions. By the end of 2 h, the transport efficiencies of selenomethionine and nano-Se were higher than that of sodium selenite (P<0.05). The highest uptake efficiency (P<0.05) was observed in cells treated with nano-Se and significant difference (P<0.05) was also observed between the cells incubated with sodium selenite and selenomethionine. As for the P(app), sodium selenite (P<0.05) had the lowest values compared with that of selenomethionine and nano-Se, in both AP-BL and BL-AP. However, no significant differences were observed in GSH-Px activities. These results indicated that the efficiency of Se in the Caco-2 cells varied with its chemical forms, which might be associated with the differences in Se transport and uptake.

Microfabrication technologies for oral drug delivery

Micro-/nanoscale technologies such as lithographic techniques and microfluidics offer promising avenues to revolutionalize the fields of tissue engineering, drug discovery, diagnostics and personalized medicine. Microfabrication techniques are being explored for drug delivery applications due to their ability to combine several features such as precise shape and size into a single drug delivery vehicle. They also offer to create unique asymmetrical features incorporated into single or multiple reservoir systems maximizing contact area with the intestinal lining. Combined with intelligent materials, such microfabricated platforms can be designed to be bioadhesive and stimuli-responsive. Apart from drug delivery devices, microfabrication technologies offer exciting opportunities to create biomimetic gastrointestinal tract models incorporating physiological cell types, flow patterns and brush-border like structures. Here we review the recent developments in this field with a focus on the applications of microfabrication in the development of oral drug delivery devices and biomimetic gastrointestinal tract models that can be used to evaluate the drug delivery efficacy.

In vitro 3D human small intestinal villous model for drug permeability determination

We present a novel method for testing drug permeability that features human cells cultured on hydrogel scaffolds made to accurately replicate the shape and size of human small intestinal villi. We compared villous scaffolds to more conventional 2D cultures in paracellular drug absorption and cell growth experiments. Our results suggest that 3D villous platforms facilitate cellular differentiation and absorption more similar to mammalian intestines than can be achieved using conventional culture. To the best of our knowledge, this is the first accurate 3D villus model offering a well-controlled microenvironment that has strong physiological relevance to the in vivo system.

Estimating intestinal mucosal permeation of compounds using Caco-2 cell monolayers

Step-by-step protocols are provided in this unit for the measurement of apparent permeability coefficients of compounds using Caco-2 cell monolayers as an in vitro model of the intestinal mucosa. Procedures for culturing the cells and transmonolayer transport studies are also included. Critical issues for successfully estimating intestinal mucosal permeation of drugs are discussed. Step-by-step protocols are provided in this unit for the measurement of apparent permeability coefficients of compounds using.

In vitro testing of commercial and potential probiotic lactic acid bacteria

Probiotics are defined as live microorganisms which when administered in adequate amounts confer a health benefit on the host. The objective of this study was to investigate the diversity of selected commercial and potential probiotic lactic acid bacteria using common in vitro screening assays such as transit tolerance in the upper human gastrointestinal tract, adhesion capacity to human intestinal cell lines and effect on epithelial barrier function. The selected bacteria include strains of Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus farciminis, Lactobacillus sakei, Lactobacillus gasseri, Lactobacillus rhamnosus, Lactobacillus reuteri and Pediococcus pentosaceus. Viable counts after simulated gastric transit tolerance showed that L. reuteri strains and P. pentosaceus tolerate gastric juice well, with no reduction of viability, whereas L. pentosus, L. farciminis and L. sakei strains lost viability over 180min. All strains tested tolerate the simulated small intestinal juice well. The bacterial adhesion capacity to human intestinal cells revealed major species and strain differences. Overall, L. plantarum MF1298 and three L. reuteri strains had a significant higher adhesion capacity compared to the other strains tested. All strains, both living and UV-inactivated, had little effect on the epithelial barrier function. However, living L. reuteri strains revealed a tendency to increase the transepithelial electrical resistance (TER) from 6 to 24h. This work demonstrates the diversity of 18 potential probiotic bacteria, with major species and strain specific effects in the in vitro screening assays applied. Overall, L. reuteri strains reveal some interesting characteristics compared to the other strains investigated.

Kinetic modelling of in vitro cell-based assays to characterize non-specific bindings and ADME processes in a static and a perfused fluidic system

Recently, physiologically based perfusion in vitro systems have been developed to provide cell culture environment close to in vivo cell environment (e.g., fluidic conditions, organ interactions). In this work, we model and compare the fate of a chemical, benzo[a]pyrene (B[a]P), in a perfusion and a standard (static well-plate) system. These in vitro systems are composed of Caco-2 and HepG2 cells so as to mimic absorption across the small intestine and intestinal and hepatic metabolism. Compartmental models were developed and calibrated with B[a]P kinetics data in the culture medium to estimate the apparent permeability of Caco-2 cells, the in vitro biotransformation of B[a]P, as well as the different routes of loss by non-specific adsorption. Our results show that non-specific binding is the main process responsible for the depletion of B[a]P in the culture media: at steady state, only 40% and 24% of the total concentration of B[a]P are bioavailable in the static and perfused systems, respectively. We also showed that Caco-2 permeability in the perfused culture system is closer to in vivo conditions than the one obtained in the static system and that higher cellular metabolic activities are observed in static conditions. Perfused in vitro systems combined with kinetic modelling are promising tools for studying in vitro the different processes involved in the toxicokinetics of xenobiotics.

Enniatin B1 is a substrate of intestinal P-glycoprotein, multidrug resistance-associated protein 2 and breast cancer resistance protein

Enniatins are cyclic hexadepsipeptides produced by various fungi, known to have ionophoric, antibiotic and insecticidal activity. The aim of the present study was to evaluate the intestinal absorption characteristics of enniatin B1 (ENN-B1). Using the human intestinal Caco-2 cell line, we found that the permeability of ENN-B1 in the basolateral to apical direction was 6.7× higher as compared to the permeability in the opposite direction, indicating involvement of apically located transporters. Transport of ENN-B1 in the apical to basolateral direction was increased significantly upon treatment of Caco-2 cells with the P-glycoprotein (Pgp) inhibitor verapamil and the multidrug resistance-associated protein 2 (MRP2) inhibitor MK571, but only weakly and not significantly after treatment with the breast cancer resistance protein (BCRP) inhibitor fumitremorgin C. Additionally, MDCK II cells over-expressing Pgp, MRP2 or BCRP, showed reduced sensitivity towards ENN-B1. These data demonstrate for the first time that ENN-B1 is a substrate of MRP2 and suggests that Pgp, MRP2 and possibly BCRP are involved in transport of ENN-B1 across the intestine.

Transport and metabolism of the antitumour drug candidate 2'-benzoyloxycinnamaldehyde in Caco-2 cells

The transport and metabolism of the antitumour drug candidate 2'-benzoyloxycinnamaldehyde (BCA) was characterized in Caco-2 cells. BCA disappeared rapidly from the donor side without being transported to the receiver side during its absorptive transport across Caco-2 cells. Its metabolites 2'-hydroxycinnamaldehyde (HCA) and o-coumaric acid (OCA) were formed in both the donor and the receiver sides. HCA, in a separate study, also disappeared rapidly from the donor side, mostly being converted to its oxidative metabolite OCA during its absorptive transport across Caco-2 cells. OCA was transported rapidly in the absorptive direction across Caco-2 cells with a P(app) of 25.4 +/- 1.0 x 10(-6) cm s(-1) (mean +/- standard deviation (SD), n = 3). OCA was fully recovered from both the donor and the receiver side throughout the time-course of this study. Formation of HCA from BCA was inhibited almost completely by bis(p-nitrophenyl)phosphate (BNPP), a selective inhibitor of carboxylesterases (CES), and phenylmethylsulfonyl fluoride (PMSF), a broad specificity inhibitor of esterases in Caco-2 cells, suggesting that this hydrolytic biotransformation was likely mediated predominantly by CES. Conversion of HCA to OCA was inhibited significantly by isovanillin, a selective inhibitor of aldehyde oxidase (AO). Inhibitors for xanthine oxidase (XO) and aldehyde dehydrogenase (ALDH), which are known to be involved in the oxidation of aldehydes to carboxylic acids, did not have a significant effect on the biotransformation of HCA to OCA in Caco-2 cells. In summary, the present work demonstrates that BCA is hydrolysed rapidly to HCA, followed by subsequent oxidation to OCA, in Caco-2 cells. The results provide a mechanistic understanding of the poor absorption and low bioavailability of BCA after oral administration.

Transport and metabolism of MitoQ10, a mitochondria-targeted antioxidant, in Caco-2 cell monolayers

Mitoquinone (MitoQ10 mesylate) is a mitochondria-targeted antioxidant formulated for oral administration in the treatment of neurodegenerative diseases. We have investigated the absorption and metabolism of MitoQ10 in Caco-2 cell monolayers. The intracellular accumulation of MitoQ10 was 18–41% of the total amount of MitoQ10 added. Some of the intracellular MitoQ10 was reduced to mitoquinol and subsequently metabolized to glucuronide and sulfate conjugates. Transport of MitoQ10 was polarized with the apparent permeability (Papp) from basolateral (BL) to apical (AP) (PappBL→AP) being &gt;2.5-fold the Papp from apical to basolateral (PappAP→BL). In the presence of 4% bovine serum albumin on the basolateral side, the PappAP→BL value increased 7-fold compared with control. The PappBL→AP value decreased by 26, 31 and 61% in the presence of verapamil 100 μM, ciclosporin 10 and 30 μM, respectively, whereas the PappAP→BL value increased 71% in the presence of ciclosporin 30 μM. Apical efflux of mitoquinol sulfate and mitoquinol glucuronide conjugates was significantly decreased by ciclosporin 30 μM and the breast cancer receptor protein (BCRP) inhibitor, reserpine 25 μM, respectively. These results suggested that the bioavailability of MitoQ10 may be limited by intracellular metabolism and the action of P-glycoprotein and BCRP. However, the dramatic increase in absorptive Papp in the presence of bovine serum albumin on the receiver side suggests these barrier functions may be less significant in-vivo.

In-vitro mutagenic potential and effect on permeability of co-administered drugs across Caco-2 cell monolayers of Rubus idaeus and its fortified fractions

This study investigated the mutagenic, anti-mutagenic and cytotoxic effects of acetone extract of raspberry, Rubus idaeus L. (v. Ottawa) Rosaceae, and the isolated and characterized ellagitannin and anthocyanin fractions thereof, suitable for food applications. The studied raspberry extract and fractions did not show any mutagenic effects determined in the miniaturized Ames test and were not cytotoxic to Caco-2 cells at the used concentrations. However, the anti-mutagenic properties were changed (i.e. decreased mutagenicity of 2-nitrofluorene in strain TA98, and slightly increased mutagenicity of 2-aminoanthracene in strain TA100) with metabolic activation. Further, their influence on the permeability of co-administered common drugs (ketoprofen, paracetamol, metoprolol and verapamil) across Caco-2 monolayers was evaluated. The apical-to-basolateral permeability of highly permeable verapamil was mostly affected (decreased) during co-administration of the raspberry extract or the ellagitannin fraction. Ketoprofen permeability was decreased by the ellagitannin fraction. Consumption of food rich in phytochemicals, as demonstrated here with chemically characterized raspberry extract and fractions, with well-absorbing drugs would seem to affect the permeability of some of these drugs depending on the components. Thus their effects on the absorption of drugs in-vivo cannot be excluded.

Coumarins permeability in Caco-2 cell model

Objectives

The presence of coumarins in human diet, their multiple pharma***ćological properties and occurrence in various herbal remedies represent significant reasons to explore their membrane permeability, as a first event contributing to coumarins oral bioavailability. Thus, we evaluated the permeability and cytotoxicity of 18 coumarins, with different substitution patterns involving OH, OCH3 and CH3 groups.

Methods

A modified Caco-2 permeability model was used, in which the permeability test is performed with a robotic workstation and cells are grown on 96-well plates for 7 days.

Key findings

All studied coumarins were highly permeable, with calculated Papp values that varied within 4.1 times 10−5 to 2.1 times 10−4 in apical to basolateral studies and within 1.8 times 10−5 to 7.0 times 10−5 in basolateral to apical studies. The efflux ratio remained in all cases below 1. It was demonstrated that the type and position of substituents contributed more to the permeability than the number of substituents.

Conclusions

The results allowed us to predict that these coumarins are well absorbed in the gut lumen and efflux is not limiting the absorption. Five coumarins had an influence on the mitochondrial function of Caco-2 cells (1 &lt; 80%, 4 &gt; 120%), according to the WST-1 cytotoxicity test, but this does not seem to affect the permeability of the compounds.

Regulation of tight junction permeability by sodium caprate in human keratinocytes and reconstructed epidermis

Tight junctions (TJs) restrict paracellular flux of water and solutes in epithelia and endothelia. In epidermis, the physiological role of TJs is not fully understood. In this study, sodium caprate (C10), which dilates intestinal TJs, was applied to cultured human epidermal keratinocytes and reconstructed human epidermis to investigate the effects of C10 on epidermal TJs. C10 treatment decreased transepithelial electrical resistance and increased paracellular permeability, although Western blots showed that the expression of TJ-related transmembrane proteins was not decreased. The effects of C10 were reversible. Immunofluorescence microscopy and immuno-replica electron microscopy showed that the localization of TJ strands were disintegrated, concomitant with the dispersion and/or disappearance of TJ-related molecules from the cell surface. These findings suggest that C10 impairs barrier function by physically disrupting TJ conformation in the epidermis. Furthermore, these results also show that proper localization of the molecules on the cellular membrane is important for TJ barrier function.

Pomegranate juice inhibits sulfoconjugation in Caco-2 human colon carcinoma cells

Several fruit juices have been reported to cause food-drug interactions, mainly affecting cytochrome P450 activity; however, little is known about the effects of fruit juices on conjugation reactions. Among several fruit juices tested (apple, peach, orange, pineapple, grapefruit, and pomegranate), pomegranate juice potently inhibited the sulfoconjugation of 1-naphthol in Caco-2 cells. This inhibition was both dose- and culture time-dependent, with a 50% inhibitory concentration (IC(50)) value calculated at 2.7% (vol/vol). In contrast, no obvious inhibition of glucuronidation of 1-naphthol in Caco-2 cells was observed by any of the juices examined. Punicalagin, the most abundant antioxidant polyphenol in pomegranate juice, was also found to strongly inhibit sulfoconjugation in Caco-2 cells with an IC(50) of 45 microM, which is consistent with that of pomegranate juice. These data suggest that punicalagin is mainly responsible for the inhibition of sulfoconjugation by pomegranate juice. We additionally demonstrated that pomegranate juice and punicalagin both inhibit phenol sulfotransferase activity in Caco-2 cells in vitro, at concentrations that are almost equivalent to those used in the Caco-2 cells. Pomegranate juice, however, shows no effects on the expression of the sulfotransferase SULT1A family of genes (SULT1A1 and SULT1A3) in Caco-2 cells. These results indicate that the inhibition of sulfotransferase activity by punicalagin in Caco-2 cells is responsible for the reductions seen in 1-naphthyl sulfate accumulation. Our data also suggest that constituents of pomegranate juice, most probably punicalagin, impair the enteric functions of sulfoconjugation and that this might have effects upon the bioavailability of drugs and other compounds present in food and in the environment. These effects might be related to the anticarcinogenic properties of pomegranate juice.

Availability and toxicity of Fe(II) and Fe(III) in Caco-2 cells

The objective of the present study was to compare the toxicity and availability of Fe(II) and Fe(III) to Caco-2 cells. Cellular damage was studied by measuring cell proliferation and lactate dehydrogenase (LDH) release. The activities of two major antioxidative enzymes [superoxide dismutase (SOD) and glutathione peroxidase (GPx)] and differentiation marker (alkaline phosphatase) were determined after the cells were exposed to different levels of iron salts. The cellular iron concentration was investigated to evaluate iron bioavailability. The results show that iron uptake of the cells treated with Fe(II) is significantly higher than that of the cells treated with Fe(III) (P<0.05). Fe(II) at a concentration >1.5 mmol/L was found to be more effective in reducing cellular viability than Fe(III). LDH release investigation suggests that Fe(II) can reduce stability of the cell membrane. The activities of SOD and GPx of the cells treated with Fe(II) were higher than those of the cells treated with Fe(III), although both of them increased with raising iron supply levels. The results indicate that both Fe(II) and Fe(III) could reduce the cellular antioxidase gene expression at high levels.