Caco-2/TC7 cell line characterization for intestinal absorption: how reliable is this in vitro model for the prediction of the oral dose fraction absorbed in human?

Individualized Pharmacotherapy Utilizing Genetic Biomarkers and Novel In Vitro Systems As Predictive Tools for Optimal Drug Development and Treatment

In the area of drug development and clinical pharmacotherapy, a profound understanding of the pharmacokinetics and potential adverse reactions associated with the drug under investigation is paramount. Essential to this endeavor is a comprehensive understanding about interindividual variations in absorption, distribution, metabolism, and excretion (ADME) genetics and the predictive capabilities of in vitro systems, shedding light on metabolite formation and the risk of adverse drug reactions (ADRs). Both the domains of pharmacogenomics and the advancement of in vitro systems are experiencing rapid expansion. Here we present an update on these burgeoning fields, providing an overview of their current status and illuminating potential future directions. SIGNIFICANCE STATEMENT: There is very rapid development in the area of pharmacogenomics and in vitro systems for predicting drug pharmacokinetics and risk for adverse drug reactions. We provide an update of the current status of pharmacogenomics and developed in vitro systems on these aspects aimed to achieve a better personalized pharmacotherapy.

Human in vitro blood barrier models: architectures and applications

Blood barriers serve as key points of transport for essential molecules as well as lines of defense to protect against toxins. In vitro modeling of these barriers is common practice in the study of their physiology and related diseases. This review describes a common method of using an adaptable, low cost, semipermeable, suspended membrane to experimentally model three blood barriers in the human body: the blood-brain barrier (BBB), the gut-blood barrier (GBB), and the air-blood barrier (ABB). The GBB and ABB both protect from the outside environment, while the BBB protects the central nervous system from potential neurotoxic agents in the blood. These barriers share several commonalities, including the formation of tight junctions, polarized cellular monolayers, and circulatory system contact. Cell architectures used to mimic barrier anatomy as well as applications to study function, dysfunction, and response provide an overview of the versatility enabled by these cultural systems.

Bioavailability of Korean mint (Agastache rugosa) polyphenols in humans and a Caco-2 cell model: a preliminary study exploring the efficacy

Agastache rugosa, commonly known as Korean mint (KM), is a medicinal plant renowned for its potential health-promoting properties. However, the lack of bioavailability studies has hindered the acquisition of conclusive evidence. In this study, we investigated the bioavailability of six key polyphenols present in KM, including rosmarinic acid (RA), acacetin (AC), and four glycosides of AC. Utilizing UPLC-MS/MS, we analyzed their presence in human plasma and Caco-2 monolayers grown in permeable filter supports. Following single ingestion, we were able to detect RA, AC, and tilianin (TA) in the plasma. Consistent results were obtained for AC and TA but no transport was found for RA in a highly tight Caco-2 cell monolayer, indicating transport through the intercellular space for RA and transepithelial transport for AC and TA. Other AC glucosides with acetyl and/or malonyl groups were rarely found in the plasma. Interestingly, AC glucosides with only an acetyl group appeared at the basolateral side in Caco-2 monolayers, suggesting exclusive hydrolysis of malonyl glucosides in the colon. These findings highlight the high potential of RA, AC, and TA as bioactive compounds that may confer health benefits.

Challenges and Opportunities in the Oral Delivery of Recombinant Biologics

Recombinant biological molecules are at the cutting-edge of biomedical research thanks to the significant progress made in biotechnology and a better understanding of subcellular processes implicated in several diseases. Given their ability to induce a potent response, these molecules are becoming the drugs of choice for multiple pathologies. However, unlike conventional drugs which are mostly ingested, the majority of biologics are currently administered parenterally. Therefore, to improve their limited bioavailability when delivered orally, the scientific community has devoted tremendous efforts to develop accurate cell- and tissue-based models that allow for the determination of their capacity to cross the intestinal mucosa. Furthermore, several promising approaches have been imagined to enhance the intestinal permeability and stability of recombinant biological molecules. This review summarizes the main physiological barriers to the oral delivery of biologics. Several preclinical in vitro and ex vivo models currently used to assess permeability are also presented. Finally, the multiple strategies explored to address the challenges of administering biotherapeutics orally are described.

Complexification of In Vitro Models of Intestinal Barriers, A True Challenge for a More Accurate Alternative Approach

The use of cell models is common to mimic cellular and molecular events in interaction with their environment. In the case of the gut, the existing models are of particular interest to evaluate food, toxicants, or drug effects on the mucosa. To have the most accurate model, cell diversity and the complexity of the interactions must be considered. Existing models range from single-cell cultures of absorptive cells to more complex combinations of two or more cell types. This work describes the existing solutions and the challenges that remain to be solved.

Intestinal protein uptake and IgE-mediated food allergy

Food allergy is affecting 5-8% of young children and 2-4% of adults and seems to be increasing in prevalence. The cause of the increase in food allergy is largely unknown but proposed to be influenced by both environmental and lifestyle factors. Changes in intestinal barrier functions and increased uptake of dietary proteins have been suggested to have a great impact on food allergy. In this review, we aim to give an overview of the gastrointestinal digestion and intestinal barrier function and provide a more detailed description of intestinal protein uptake, including the various routes of epithelial transport, how it may be affected by both intrinsic and extrinsic factors, and the relation to food allergy. Further, we give an overview of in vitro, ex vivo and in vivo techniques available for evaluation of intestinal protein uptake and gut permeability in general. Proteins are digested by gastric, pancreatic and integral brush border enzymes in order to allow for sufficient nutritional uptake. Absorption and transport of dietary proteins across the epithelial layer is known to be dependent on the physicochemical properties of the proteins and their digestion fragments themselves, such as size, solubility and aggregation status. It is believed, that the greater an amount of intact protein or larger peptide fragments that is transported through the epithelial layer, and thus encountered by the mucosal immune system in the gut, the greater is the risk of inducing an adverse allergic response. Proteins may be absorbed across the epithelial barrier by means of various mechanisms, and studies have shown that a transcellular facilitated transport route unique for food allergic individuals are at play for transport of allergens, and that upon mediator release from mast cells an enhanced allergen transport via the paracellular route occurs. This is in contrast to healthy individuals where transcytosis through the enterocytes is the main route of protein uptake. Thus, knowledge on factors affecting intestinal barrier functions and methods for the determination of their impact on protein uptake may be useful in future allergenicity assessments and for development of future preventive and treatment strategies.

Beyond the Michaelis-Menten: Accurate Prediction of Drug Interactions through Cytochrome P450 3A4 Induction

The US Food and Drug Administration (FDA) guidance has recommended several model-based predictions to determine potential drug-drug interactions (DDIs) mediated by cytochrome P450 (CYP) induction. In particular, the ratio of substrate area under the plasma concentration-time curve (AUCR) under and not under the effect of inducers is predicted by the Michaelis-Menten (MM) model, where the MM constant ( K m $$ {K}_{\mathrm{m}} $$ ) of a drug is implicitly assumed to be sufficiently higher than the concentration of CYP enzymes that metabolize the drug ( E T $$ {E}_{\mathrm{T}} $$ ) in both the liver and small intestine. Furthermore, the fraction absorbed from gut lumen ( F a $$ {F}_{\mathrm{a}} $$ ) is also assumed to be one because F a $$ {F}_{\mathrm{a}} $$ is usually unknown. Here, we found that such assumptions lead to serious errors in predictions of AUCR. To resolve this, we propose a new framework to predict AUCR. Specifically, F a $$ {F}_{\mathrm{a}} $$ was re-estimated from experimental permeability values rather than assuming it to be one. Importantly, we used the total quasi-steady-state approximation to derive a new equation, which is valid regardless of the relationship between K m $$ {K}_{\mathrm{m}} $$ and E T $$ {E}_{\mathrm{T}} $$ , unlike the MM model. Thus, our framework becomes much more accurate than the original FDA equation, especially for drugs with high affinities, such as midazolam or strong inducers, such as rifampicin, so that the ratio between K m $$ {K}_{\mathrm{m}} $$ and E T $$ {E}_{\mathrm{T}} $$ becomes low (i.e., the MM model is invalid). Our work greatly improves the prediction of clinical DDIs, which is critical to preventing drug toxicity and failure.

The Caco-2 Model: Modifications and enhancements to improve efficiency and predictive performance

The Caco-2 cell model has been widely used to assess the permeability of drug candidates. It has provided a high throughput in vitro platform, functionally resembling the enterocytes. Since the oral route is the most preferred for drug administration, the Caco-2 cell model acts as a very important tool to elucidate the oral "druggability" of a molecule by providing a fairly reliable estimate of its permeability through the intestinal membrane. Despite its shortcomings (the lack of a mucus layer, long cultivation period, inter-lab variability, and differences in expression of enzymes, transporters, and tight junction complexes) it remains heavily used due to its reliability, predictive performance, and wide acceptance. Various modifications have been made: co-culturing with other intestinal cells, applying biosimilar mucus, reducing culturing time, combining Caco-2 monolayer with the dissolution apparatus, enhancing protein expression, and redesigning the sampling apparatus. These modifications are intended to overcome some of the shortcomings of the Caco-2 model in order to make its use easier, quicker, economical, and more representative of the intestine. The aim of this review is to discuss such modifications to enhance this model's utility, predictive performance, and reproducibility.

Investigation of the Uptake and Transport of Aspirin Eugenol Ester in the Caco-2 Cell Model

Background: Aspirin eugenol ester (AEE) is a novel medicinal compound synthesized by esterification of aspirin with eugenol using the prodrug principle. AEE has the pharmacological activities of being anti-inflammatory, antipyretic, analgesic, anti-cardiovascular diseases, and anti-oxidative stress However, its oral bioavailability is poor, and its intestinal absorption and transport characteristics are still unknown.

Objective: The purpose of this study was to investigate the uptake and transport mechanisms of AEE in Caco-2 cells.

Methods: The effects of time, concentration, and temperature on the transport and uptake of AEE were studied.

Results: The results showed that a higher concentration of salicylic acid (SA) was detected in the supernatant of cell lysates and cell culture medium, while AEE was not detected. Therefore, the content change of AEE was expressed as the content change of its metabolite SA. In the uptake experiment, when the factors of time, concentration, and temperature were examined, the uptake of SA reached the maximum level within 30 min, and there was concentration dependence. In addition, low temperature (4°C) could significantly reduce the uptake of SA in Caco-2 cells. In the transport experiment, under the consideration of time, concentration, and temperature, the transepithelial transport of SA from AP-BL and BL-AP sides was time-dependent. The amount of SA transported in Caco-2 cells increased with the increase of concentration, but the transmembrane transport rate had no correlation with the concentration. This phenomenon may be due to the saturation phenomenon of high concentration. The efflux ratio (ER) was less than 1, which indicated that their intestinal transport mechanism was passive transport. Moreover, the temperature had a significant effect on the transport of AEE.

Conclusion: In summary, intestinal absorption of AEE through Caco-2 cell monolayers was related to passive transport. The uptake and transport of AEE were concentration-dependent, and temperature significantly affected their uptake and transport. The absorption and transport characteristics of AEE may contribute to the exploration of mechanisms of absorption and transport of chemosynthetic drugs in vitro.

Inhibitory activity of flavonoids against human sucrase-isomaltase (α-glucosidase) activity in a Caco-2/TC7 cellular model

Type 2 diabetes (T2D) is the most common form of diabetes, and the number of people with this metabolic disease is steadily increasing worldwide. Among the available antidiabetic agents, α-glucosidase inhibitors are the most effective at reducing postprandial hyperglycaemia (PPHG), one of the main characteristics of T2D. However, most of the studies that have been performed have used the more readily available rat intestinal preparations or yeast α-glucosidase as the enzyme source, which despite being useful and cost effective, have a questionable physiological value. The present study evaluates the inhibitory activity of a selected group of flavonoids against human sucrase-isomaltase (SI), the α-glucosidase found in Caco-2/TC7 cells. A microassay using the physiological substrates sucrose and maltose, and a synthetic substrate, p-nitrophenyl-α-D-glucopyranoside (pNPG) was performed. The most active flavonoid was compound 4 (melanoxetin), presenting an IC₅₀ value similar using the two natural substrates. In contrast, the tested flavonoids were not effective at inhibiting SI, when pNPG was used as a substrate. Hydroxylation of flavonoids at C-3 of the C ring, at C-3' and C-4' of the B ring, and at C-7 and C-8 of the A ring were the features that improved the inhibitory activity of flavonoids against human SI. These phenolic compounds deserve further exploration as alternatives to the currently available α-glucosidase inhibitors. The present study also demonstrates that the non-clinical in vitro studies conducted for the evaluation of α-glucosidase activity should use the human source rather than surrogate sources of α-glucosidase.

Peptides derived from the gastrointestinal digestion of amaranth 11S globulin: Structure and antioxidant functionality

The relationship between structural and physicochemical properties and antioxidant activity of peptides from amaranth 11S-globulin was studied. Peptides AWEEREQGSR, TEVWDSNEQ, IYIEQGNGITGM and YLAGKPQQEH had the greatest in vitro activity (ORAC, HORAC). GDRFQDQHQ, HVIKPPSRA and KFNRPETT were the most active ones against Cu⁺²/H₂O₂-induced-LDL oxidation. In a cellular system (H₂O₂-induced-Caco2-TC7), TEVWDSNEQ, IYIEQGNGITGM, GDRFQDQHQ, LAGKPQQEHSGEHQ and KFNRPETT were the most effective in decreasing ROS, while the effects on SOD, GPx, and GSH were variable. To understand the structure-antioxidant activity relationships, the content of aromatic and acidic amino acids, the degree of hydrophobicity and the charge distribution on the accessible surface of peptides structures obtained by molecular dynamics were analysed. The low correlation between in vitro, ex vivo and cellular activities could be explained by the influence of physicochemical and structural properties on the interaction with complex systems (LDL/cells), peptide modifications and/or mechanisms other than direct ROS inhibition in the cells.

Flavonoids as Human Intestinal α-Glucosidase Inhibitors

Certain flavonoids can influence glucose metabolism by inhibiting enzymes involved in carbohydrate digestion and suppressing intestinal glucose absorption. In this study, four structurally-related flavonols (quercetin, kaempferol, quercetagetin and galangin) were evaluated individually for their ability to inhibit human α-glucosidases (sucrase, maltase and isomaltase), and were compared with the antidiabetic drug acarbose and the flavan-3-ol(−)-epigallocatechin-3-gallate (EGCG). Cell-free extracts from human intestinal Caco-2/TC7 cells were used as the enzyme source and products were quantified chromatographically with high accuracy, precision and sensitivity. Acarbose inhibited sucrase, maltase and isomaltase with IC₅₀ values of 1.65, 13.9 and 39.1 µM, respectively. A similar inhibition pattern, but with comparatively higher values, was observed with EGCG. Of the flavonols, quercetagetin was the strongest inhibitor of α-glucosidases, with inhibition constants approaching those of acarbose, followed by galangin and kaempferol, while the weakest were quercetin and EGCG. The varied inhibitory effects of flavonols against human α-glucosidases depend on their structures, the enzyme source and substrates employed. The flavonols were more effective than EGCG, but less so than acarbose, and so may be useful in regulating sugar digestion and postprandial glycaemia without the side effects associated with acarbose treatment.

An overview of in vitro, ex vivo and in vivo models for studying the transport of drugs across intestinal barriers

Oral administration is the most commonly used route for drug delivery owing to its cost-effectiveness, ease of administration, and high patient compliance. However, the absorption of orally delivered compounds is a complex process that greatly depends on the interplay between the characteristics of the drug/formulation and the gastrointestinal tract. In this contribution, we review the different preclinical models (in vitro, ex vivo and in vivo) from their development to application for studying the transport of drugs across intestinal barriers. This review also discusses the advantages and disadvantages of each model. Furthermore, the authors have reviewed the selection and validation of these models and how the limitations of the models can be addressed in future investigations. The correlation and predictability of the intestinal transport data from the preclinical models and human data are also explored. With the increasing popularity and prevalence of orally delivered drugs/formulations, sophisticated preclinical models with higher predictive capacity for absorption of oral formulations used in clinical studies will be needed.

Cytoprotective Effects of Fish Protein Hydrolysates against H2O2-Induced Oxidative Stress and Mycotoxins in Caco-2/TC7 Cells

Many studies report the potent antioxidant capacity for fish protein hydrolysates, including radical scavenging activity and inhibition ability on lipid peroxidation (LPO). In this study, the in vitro cytotoxicity of protein hydrolysates from different salmon, mackerel, and herring side streams fractions was evaluated in the concentration range from 1 to 1:32 dilution, using cloned human colon adenocarcinoma cells TC7 (Caco-2/TC7) by MTT and PT assays. The protein hydrolysates' antioxidant capacity and oxidative stress effects were evaluated by LPO and reactive oxygen species (ROS) generation, respectively. The antioxidant capacity for pure and bioavailable hydrolysate fraction was also evaluated and compared. Additionally, mycotoxin levels were determined in the fish protein hydrolysates, and their cytoprotective effect against T-2 toxin was evaluated. Both hydrolysates and their bioavailable fraction induced similar cell viability rates. The highest cytoprotective effect was obtained for the salmon viscera protein hydrolysate (HSV), which increased the cell viability by 51.2%. ROS accumulation induced by H₂O₂ and LPO was suppressed by all pure hydrolysates. The cytoprotective effect of hydrolysates was observed against T-2. Moreover, the different fish fraction protein hydrolysates contain variable nutrients and unique bioactive peptide composition showing variable bioactivity, which could be a useful tool in developing dietary supplements with different target functional properties.

Food Contaminants Effects on an In Vitro Model of Human Intestinal Epithelium

Pesticide residues represent an important category of food contaminants. Furthermore, during food processing, some advanced glycation end-products resulting from the Maillard reaction can be formed. They may have adverse health effects, in particular on the digestive tract function, alone and combined. We sought to validate an in vitro model of the human intestinal barrier to mimic the effects of these food contaminants on the epithelium. A co-culture of Caco-2/TC7 cells and HT29-MTX was stimulated for 6 h with chlorpyrifos (300 μM), acrylamide (5 mM), N^ε-Carboxymethyllysine (300 μM) alone or in cocktail with a mix of pro-inflammatory cytokines. The effects of those contaminants on the integrity of the gut barrier and the inflammatory response were analyzed. Since the co-culture responded to inflammatory stimulation, we investigated whether this model could be used to evaluate the effects of food contaminants on the human intestinal epithelium. CPF alone affected tight junctions’ gene expression, without inducing any inflammation or alteration of intestinal permeability. CML and acrylamide decreased mucins gene expression in the intestinal mucosa, but did not affect paracellular intestinal permeability. CML exposure activated the gene expression of MAPK pathways. The co-culture response was stable over time. This cocktail of food contaminants may thus alter the gut barrier function.

In vitro models replicating the human intestinal epithelium for absorption and metabolism studies: A systematic review

Absorption, distribution, metabolism and excretion (ADME) studies represent a fundamental step in the early stages of drug discovery. In particular, the absorption of orally administered drugs, which occurs at the intestinal level, has gained attention since poor oral bioavailability often led to failures for new drug approval. In this context, several in vitro preclinical models have been recently developed and optimized to better resemble human physiology in the lab and serve as an animal alternative to accomplish the 3Rs principles. However, numerous models are ineffective in recapitulating the key features of the human small intestine epithelium and lack of prediction potential for drug absorption and metabolism during the preclinical stage. In this review, we provide an overview of in vitro models aimed at mimicking the intestinal barrier for pharmaceutical screening. After briefly describing how the human small intestine works, we present i) conventional 2D synthetic and cell-based systems, ii) 3D models replicating the main features of the intestinal architecture, iii) micro-physiological systems (MPSs) reproducing the dynamic stimuli to which cells are exposed in the native microenvironment. In this review, we will highlight the benefits and drawbacks of the leading intestinal models used for drug absorption and metabolism studies.

Oral absorption mechanism of the polysaccharides from Gastrodia elata Blume base on fluorescence labeling

The mechanisms of action of polysaccharides in vivo have been widely elucidated. However, the systematic research of its absorption and transport mechanisms remains unclear. Herein, we extracted a polysaccharide fraction (GEP) from Gastrodia elata by water extraction and alcohol precipitation and aimed to reveal its oral absorption processes through animal models and Caco-2 cells monolayer models. Our research data showed that GEP-Cy5.5 could be absorbed through the small intestine and the main absorption intestinal segment was the ileum (the absorption rate constant [Ka]: (3.64 ± 0.70) × 10^-4 cm/s; the effective apparent permeability [Papp value]: (4.88 ± 1.02) × 10^-5 cm/s). The ligated intestinal loops also revealed that GEP-Cy5.5 could pass through the villi of the small intestine and the mucosal barrier into the submucosa. Furthermore, GEP-Cy5.5 was readily absorbed into the blood through the gastrointestinal tract, then distributed in the liver and the kidney. The Papp value of in vitro transport study was (1.29 ± 0.08) × 10^-6 cm/s, which was a time-dependent process. Notably, GEP-Cy5.5 was transported through the endocytosis process mediated by clathrin and macropinocytosis. The underlying absorptive mechanisms of GEP in vivo and in vitro were clarified, which provided the guidance for clinical medicine administration and could deepen the biological understanding of oral polysaccharides.

A quantitative model for metabolic intervention using gut microbes

As medicine shifts toward precision-based and personalized therapeutics, utilizing more complex biomolecules to treat increasingly difficult and rare conditions, microorganisms provide an avenue for realizing the production and processing necessary for novel drug pipelines. More so, probiotic microbes can be co-opted to deliver therapeutics by oral administration as living drugs, able to survive and safely transit the digestive tract. As living therapeutics are in their nascency, traditional pharmacokinetic-pharmacodynamic (PK-PD) models for evaluating drug candidates are not appropriate for this novel platform. Using a living therapeutic in late-stage clinical development for phenylketonuria (PKU) as a case study, we adapt traditional oral drug delivery models to properly evaluate and inform the engineering of living therapeutics. We develop the adapted for living therapeutics compartmental absorption and transit (ALT-CAT) model to provide metrics for drug efficacy across nine age groups of PKU patients and evaluate model parameters that are influenced by patient physiology, microbe selection and therapeutic production, and dosing formulations. In particular, the ALT-CAT model describes the mathematical framework to model the behavior of orally delivered engineered bacteria that act as living therapeutics by adapting similar methods that have been developed and widely-used for small molecular drug delivery and absorption.

Development of an Improved 3D in vitro Intestinal Model to Perform Permeability Studies of Paracellular Compounds

The small intestine is the primary site of drug absorption following oral administration, making paramount the proper monitoring of the absorption process. In vitro tools to predict intestinal absorption are particularly important in preclinical drug development since they are less laborious and cost-intensive and raise less ethical considerations compared to in vivo studies. The Caco-2 model is considered the gold standard of in vitro intestinal models regarding the prediction of absorption of orally delivered compounds. However, this model presents several drawbacks, such as the expression of tighter tight junctions, not being suitable to perform permeability of paracellular compounds. Besides, cells are representative of only one intestinal cell type, without considering the role of non-absorptive cells on the absorption pathway of drugs. In the present study, we developed a new three-dimensional (3D) intestinal model that aims to bridge the gap between in vitro tools and animal studies. Our 3D model comprises a collagen layer with human intestinal fibroblasts (HIFs) embedded, mimicking the intestinal lamina propria and providing 3D support for the epithelium, composed of Caco-2 cells and mucus-producing HT29-MTX cells, creating a model that can better resemble, both in terms of composition and regarding the outcomes of drug permeability when testing paracellular compounds, the human small intestine. The optimization of the collagen layer with HIFs was performed, testing different collagen concentrations and HIF seeding densities in order to avoid collagen contraction before day 14, maintaining HIF metabolically active inside the collagen disks during time in culture. HIF morphology and extracellular matrix (ECM) deposition were assessed, confirming that fibroblasts presented a normal and healthy elongated shape and secreted fibronectin and laminin, remodeling the collagen matrix. Regarding the epithelial layer, transepithelial electrical resistance (TEER) values decreased when cells were in the 3D configuration, comparing with the 2D analogs (Caco-2 and coculture of Caco-2+HT29-MTX models), becoming more similar with in vivo values. The permeability assay with fluorescein isothiocyanate (FITC)–Dextran 4 kDa showed that absorption in the 3D models is significantly higher than that in the 2D models, confirming the importance of using a more biorelevant model when testing the paracellular permeability of compounds.

The Past, Present and Future of Intestinal In Vitro Cell Systems for Drug Absorption Studies

The intestinal epithelium acts as a selective barrier for the absorption of water, nutrients and orally administered drugs. To evaluate the gastrointestinal permeability of a candidate molecule, scientists and drug developers have a multitude of cell culture models at their disposal. Static transwell cultures constitute the most extensively characterized intestinal in vitro system and can accurately categorize molecules into low, intermediate and high permeability compounds. However, they lack key aspects of intestinal physiology, including the cellular complexity of the intestinal epithelium, flow, mechanical strain, or interactions with intestinal mucus and microbes. To emulate these features, a variety of different culture paradigms, including microfluidic chips, organoids and intestinal slice cultures have been developed. Here, we provide an updated overview of intestinal in vitro cell culture systems and critically review their suitability for drug absorption studies. The available data show that these advanced culture models offer impressive possibilities for emulating intestinal complexity. However, there is a paucity of systematic absorption studies and benchmarking data and it remains unclear whether the increase in model complexity and costs translates into improved drug permeability predictions. In the absence of such data, conventional static transwell cultures remain the current gold-standard paradigm for drug absorption studies.

Molecular modeling approaches of selective adenosine receptor type 2A agonists as potential anti-inflammatory drugs

Adenosine A_2A receptor (A_2AR) is the predominant receptor in immune cells, where its activation triggers cAMP-mediated immunosuppressive signaling and the underlying inhibition of T cells activation and T cells-induced effects mediated by cAMP-dependent kinase proteins mechanisms. In this study, were used ADME/Tox, molecular docking and molecular dynamics simulations to investigate selective adenosine A_2AR agonists as potential anti-inflammatory drugs. As a result, we obtained two promising compounds (A and B) that have satisfactory pharmacokinetic and toxicological properties and were able to interact with important residues of the A_2AR binding cavity and during the molecular dynamics simulations were able to keep the enzyme complexed.Communicated by Ramaswamy H. Sarma.

Investigation of the uptake and transport of polysaccharide from Se-enriched Grifola frondosa in Caco-2 cells model

A variety of beneficial pharmacological activities have been reported for Se-enriched Grifola frondosa polysaccharides. However, little has been reported on its absorption, and its intestinal uptake and transport profiles remain unknown. Based on our previous research, the aim of this study was to investigate its absorption from two aspects - the polysaccharides and selenium of Se-enriched Grifola frondosa polysaccharides (Se-GFP-22) across Caco-2 cells in vitro. The Caco-2 cells monolayer culture model was successfully constructed to study the transport and uptake of Se-GFP-22. The results revealed that the uptake and transport of Se-GFP-22 were time- and concentration- dependent. Transport studies illustrated that Se-GFP-22 could penetrate Caco-2 cells, mainly mediated through the same routes as endocytosis and selenium in the organic selenium (Se-GFP-22) was more easily absorbed than that in the inorganic selenium control group (sodium selenite). The uptake of Se-GFP-22 may be a macropinocytosis pathway, which was an accumulation from cytoplasm to nucleus process. Se-GFP-22 was a moderately absorbed biological macromolecule testified by the apparent permeability coefficients (Papp) value and transport rates. This work illustrates the characteristics on uptake and transport of Se-GFP-22 and all these results may help to explore the mechanism of polysaccharide absorption in vitro.

Dynamic in vitro intestinal barrier model coupled to chip-based liquid chromatography mass spectrometry for oral bioavailability studies

In oral bioavailability studies, evaluation of the absorption and transport of drugs and food components across the intestinal barrier is crucial. Advances in the field of organ-on-a-chip technology have resulted in a dynamic gut-on-a-chip model that better mimics the in vivo microenvironment of the intestine. Despite a few recent integration attempts, ensuring a biologically relevant microenvironment while coupling with a fully online detection system still represents a major challenge. Herein, we designed an online technique to measure drug permeability and analyse unknown product formation across an intestinal epithelial layer of Caco-2 and HT29-MTX cells cultured on a flow-through Transwell system, while ensuring the quality and relevance of the biological model. Chip-based ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was coupled to the dynamic Transwell system via a series of switching valves, thus allowing alternating measurements of the apical and basolateral sides of the in vitro model. Two trap columns were integrated for online sample pre-treatment and compatibility enhancement. Temporal analysis of the intestinal permeability was successfully demonstrated using verapamil as a model drug and ergotamine epimers as a model for natural toxins present in foods. Evidence was obtained that our newly developed dynamic system provided reliable results versus classical static in vitro models, and moreover, for the first time, epimer-specific transport is shown for ergotamine. Finally, initial experiments with the drug granisetron suggest that metabolic activity can be studied as well, thus highlighting the versatility of the bio-integrated online analysis system developed. Graphical abstract.

The Grouping and Assessment Strategy for Organic Pigments (GRAPE): Scientific evidence to facilitate regulatory decision-making

This article presents the Grouping and Assessment Strategy for Organic Pigments (GRAPE). GRAPE is driven by the hypotheses that low (bio)dissolution and low permeability indicate absence of systemic bioavailability and hence no systemic toxicity potential upon oral exposure, and, for inhalation exposure, that low (bio)dissolution (and absence of surface reactivity, dispersibility and in vitro effects) indicate that the organic pigment is a 'poorly soluble particle without intrinsic toxicity potential'. In GRAPE Tier 1, (bio)solubility and (bio)dissolution are assessed, and in Tier 2, in vitro Caco-2 permeability and in vitro alveolar macrophage activation. Thereafter, organic pigments are grouped by common properties (further considering structural similarity depending on the regulatory requirements). In Tier 3, absence of systemic bioavailability is verified by limited in vivo screening (rat 28-day oral and 5-day inhalation toxicity studies). If Tier 3 confirms no (or only very low) systemic bioavailability, all higher-tier endpoint-specific animal testing is scientifically not-relevant. Application of the GRAPE can serve to reduce animal testing needs for all but few representative organic pigments within a group. GRAPE stands in line with the EU REACH Regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals). An ongoing research project aims at establishing a proof-of-concept of the GRAPE.

Investigating the Bioaccessibility and Bioavailability of Cadmium in a Cooked Rice Food Matrix by Using an 11-Day Rapid Caco-2/HT-29 Co-culture Cell Model Combined with an In Vitro Digestion Model

Investigating the bioaccessibility and bioavailability of Cd based on real contaminated cooked rice matrixes helps establish an accurate risk assessment method and effectively reduce the digestion and absorption of Cd. An 11-day in vitro rapid Caco-2/HT-29 co-culture cell model was used to establish and evaluate the simulation of the absorption and transport of Cd in the small intestine with a 70:30 Caco-2/HT-29 co-culture ratio and 1.0 mmol L^-1 butyric acid as a differentiation inducer. The bioaccessibility and bioavailability of Cd in cooked rice were studied using the cell model combined with an in vitro digestion model. The bioaccessibility of Cd of each of the three cooked rice samples was significantly higher in the gastric phase (59.04-80.23%) than in the gastrointestinal phase (37.14-52.93%). Despite the extension of the digestion time of the gastrointestinal phase, no significant difference was found among the time points. Results demonstrated that the amount of undigested residue, not the level of Cd contamination, significantly contributed to the bioaccessibility of Cd, which was affected by pH or ion. The absorption rate of Cd (25.08% ± 3.05%) was greater than the values obtained using the pure Caco-2 cell models. The bioavailability of Cd (8.29% ± 1.95%) was almost similar to that of Zn²⁺ (6.66% ± 1.41%) in the cooked rice matrix, indicating that the intestinal epithelium expressed a strong absorptive capacity of Cd during the absorption of essential metallic elements. The 11-day rapid Caco-2/HT-29 co-culture cell model combined with the in vitro digestion model was an efficient tool for studying the bioaccessibility and bioavailability of Cd or other substances in a food matrix to further investigate mechanistic steps and screen a broad set of food matrix factors.

Successful oral delivery of poorly water-soluble drugs both depends on the intraluminal behavior of drugs and of appropriate advanced drug delivery systems

Poorly water-soluble drugs continue to be a problematic, yet important class of pharmaceutical compounds for treatment of a wide range of diseases. Their prevalence in discovery is still high, and their development is usually limited by our lack of a complete understanding of how the complex chemical, physiological and biochemical processes that occur between administration and absorption individually and together impact on bioavailability. This review defines the challenge presented by these drugs, outlines contemporary strategies to solve this challenge, and consequent in silico and in vitro evaluation of the delivery technologies for poorly water-soluble drugs. The next steps and unmet needs are proposed to present a roadmap for future studies for the field to consider enabling progress in delivery of poorly water-soluble compounds.

Mathematical modeling of the relocation of the divalent metal transporter DMT1 in the intestinal iron absorption process

Iron is essential for the normal development of cellular processes. This metal has a high redox potential that can damage cells and its overload or deficiency is related to several diseases, therefore it is crucial for its absorption to be highly regulated. A fast-response regulatory mechanism has been reported known as mucosal block, which allows to regulate iron absorption after an initial iron challenge. In this mechanism, the internalization of the DMT1 transporters in enterocytes would be a key factor. Two phenomenological models are proposed for the iron absorption process: DMT1’s binary switching mechanism model and DMT1’s swinging-mechanism model, which represent the absorption mechanism for iron uptake in intestinal cells. The first model considers mutually excluding processes for endocytosis and exocytosis of DMT1. The second model considers a Ball’s oscillator to represent the oscillatory behavior of DMT1’s internalization. Both models are capable of capturing the kinetics of iron absorption and represent empirical observations, but the DMT1’s swinging-mechanism model exhibits a better correlation with experimental data and is able to capture the regulatory phenomenon of mucosal block. The DMT1 swinging-mechanism model is the first phenomenological model reported to effectively represent the complexity of the iron absorption process, as it can predict the behavior of iron absorption fluxes after challenging cells with an initial dose of iron, and the reduction in iron uptake observed as a result of mucosal block after a second iron dose.

Membrane transporter data to support kinetically-informed chemical risk assessment using non-animal methods: Scientific and regulatory perspectives

Humans are continuously exposed to low levels of thousands of industrial chemicals, most of which are poorly characterised in terms of their potential toxicity. The new paradigm in chemical risk assessment (CRA) aims to rely on animal-free testing, with kinetics being a key determinant of toxicity when moving from traditional animal studies to integrated in vitro-in silico approaches. In a kinetically informed CRA, membrane transporters, which have been intensively studied during drug development, are an essential piece of information. However, how existing knowledge on transporters gained in the drug field can be applied to CRA is not yet fully understood. This review outlines the opportunities, challenges and existing tools for investigating chemical-transporter interactions in kinetically informed CRA without animal studies. Various environmental chemicals acting as substrates, inhibitors or modulators of transporter activity or expression have been shown to impact TK, just as drugs do. However, because pollutant concentrations are often lower in humans than drugs and because exposure levels and internal chemical doses are not usually known in contrast to drugs, new approaches are required to translate transporter data and reasoning from the drug sector to CRA. Here, the generation of in vitro chemical-transporter interaction data and the development of transporter databases and classification systems trained on chemical datasets (and not only drugs) are proposed. Furtheremore, improving the use of human biomonitoring data to evaluate the in vitro-in silico transporter-related predicted values and developing means to assess uncertainties could also lead to increase confidence of scientists and regulators in animal-free CRA. Finally, a systematic characterisation of the transportome (quantitative monitoring of transporter abundance, activity and maintenance over time) would reinforce confidence in the use of experimental transporter/barrier systems as well as in established cell-based toxicological assays currently used for CRA.

Transcriptome analysis revealed that aflatoxin M1 could cause cell cycle arrest in differentiated Caco-2 cells

Being a hydroxylated metabolite of aflatoxin B1 (AFB1) and the most threatening aspect of AFB1 contamination, aflatoxin M1 (AFM1) can lead to hepatotoxicity and hepato-carcinogenicity, and possess intestinal cytotoxicity. However, little is known about the potential mechanisms of the extrahepatic effect. The aim of this study was to investigate intestinal dysfunction induced by AFM1 via transcriptome analysis. Gene expression profiling was analyzed to comparatively characterize the differentially expressed genes (DEGs) after differentiated Caco-2 cells were exposed to different concentrations of AFM1 for 48 h. A total of 165 DEGs were significantly clustered into two down-regulated patterns. Protein-protein interaction (PPI) network analysis based on Search Tool for Retrieval of Interacting Genes (STRING)suggested that 23 key enzymes mainly participated in the regulation of the cell cycle. Q-PCR analysis was performed to validate that key 12 genes (BUB1, BUB1B, MAD2L1, CCNA2, RB1, CDK1, ANAPC4, ATM, KITLG, PRKAA2, SIRT1, and SOS1) were involved. This study firstly revealed that the toxicity of AFM1 to intestinal functions may be partly due to the occurrence of cell cycle arrest, which is linked to changes in CDK1, SOS1/Akt, and AMPK signaling molecules.

In Silico Assessment of ADME Properties: Advances in Caco-2 Cell Monolayer Permeability Modeling

One of the main goals of in silico Caco-2 cell permeability models is to identify those drug substances with high intestinal absorption in human (HIA). For more than a decade, several in silico Caco-2 models have been made, applying a wide range of modeling techniques; nevertheless, their capacity for intestinal absorption extrapolation is still doubtful. There are three main problems related to the modest capacity of obtained models, including the existence of inter- and/or intra-laboratory variability of recollected data, the influence of the metabolism mechanism, and the inconsistent in vitro-in vivo correlation (IVIVC) of Caco-2 cell permeability. This review paper intends to sum up the recent advances and limitations of current modeling approaches, and revealed some possible solutions to improve the applicability of in silico Caco-2 permeability models for absorption property profiling, taking into account the above-mentioned issues.

β-Cyclodextrin Does not Alter the Bioaccessibility and the Uptake by Caco-2 Cells of Olive By-Product Phenolic Compounds

Alperujo—a two-phase olive mill waste that is composed of olive vegetation water and solid skin, pulp, and seed fragments - is a highly valuable olive by-product due to its high content in phenolic compounds. In this study, we assessed whether β-cyclodextrin (β-CD), which is used to extract and protect alpejuro phenolic compounds (hydroxytyrosol-O-glucoside, tyrosol, caffeic, and p-coumaric acids) could impact on their bioaccessibility (i.e., the percentage of molecule found in the aqueous phase of the digesta) and uptake by intestinal cells, by using an in vitro digestion model and Caco-2 TC7 cells in culture, respectively. Our results showed that β-CD did not change the bioaccessibility of the selected phenols. Hydroxytyrosol-O-glucoside and caffeic did not cross Caco-2 cell monolayers. Conversely ferulic acid, identified as the main caffeic acid intestinal metabolite, was absorbed through intestinal cell monolayers (~20%). Interestingly, β-CD moderately but significantly improved the local absorption of tyrosol and p-coumaric acid (2.3 + 1.4% and 8.5 ± 4.2%, respectively, p < 0.05), even if their final bioavailability (expressed as bioaccessibility × absorption by Caco-2 cells) was not modified (16.2 ± 0.6% vs. 16.8 ± 0.5% for tyrosol and 32.0 ± 3.2% vs. 37.2 ± 3.2% for p-coumaric acid, from pure alperujo and alperujo complexed with β-CD, respectively). Overall, our results show that β-CD is an interesting extraction and storage agent for phenolic compounds that does not alter their in vitro bioavailability.

Food Chemicals Disrupt Human Gut Microbiota Activity And Impact Intestinal Homeostasis As Revealed By In Vitro Systems

Growing evidence indicates that the human gut microbiota interacts with xenobiotics, including persistent organic pollutants and foodborne chemicals. The toxicological relevance of the gut microbiota-pollutant interplay is of great concern since chemicals may disrupt gut microbiota functions, with a potential impairment of host homeostasis. Herein we report within batch fermentation systems the impact of food contaminants (polycyclic aromatic hydrocarbons, polychlorobiphenyls, brominated flame retardants, dioxins, pesticides and heterocyclic amines) on the human gut microbiota by metatranscriptome and volatolome i.e. “volatile organic compounds” analyses. Inflammatory host cell response caused by microbial metabolites following the pollutants-gut microbiota interaction, was evaluated on intestinal epithelial TC7 cells. Changes in the volatolome pattern analyzed via solid-phase microextraction coupled to gas chromatography-mass spectrometry mainly resulted in an imbalance in sulfur, phenolic and ester compounds. An increase in microbial gene expression related to lipid metabolism processes as well as the plasma membrane, periplasmic space, protein kinase activity and receptor activity was observed following dioxin, brominated flame retardant and heterocyclic amine exposure. Conversely, all food contaminants tested induced a decreased in microbial transcript levels related to ribosome, translation and nucleic acid binding. Finally, we demonstrated that gut microbiota metabolites resulting from pollutant disturbances may promote the establishment of a pro-inflammatory state in the gut, as stated with the release of cytokine IL-8 by intestinal epithelial cells.

Fatty acids modulate the expression levels of key proteins for cholesterol absorption in Caco-2 monolayer

BACKGROUND

Fatty acids have been shown to modulate intestinal cholesterol absorption in cells and animals, a process that is mediated by several transporter proteins. Of these proteins, Niemann-Pick C1-Like 1 (NPC1L1) is a major contributor to this process. The current study investigates the unknown mechanism by which fatty acids modulate cholesterol absorption.

METHODS

We evaluated the effects of six fatty acids palmitic acid (PAM), oleic acid (OLA), linoleic acid (LNA), arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on cholesterol uptake and transport in human enterocytes Caco-2 cells, and on the mRNA expression levels of NPC1L1, others proteins (ABCG5, ABCG8, ABCA1, ACAT2, MTP, Caveolin 1, Annexin-2) involved in cholesterol absorption, and SREBP-1 and SREBP-2 that are responsible for lipid metabolism.

RESULTS

The polyunsaturated fatty acids (PUFAs), especially for EPA and DHA, dose-dependently inhibited cholesterol uptake and transport in Caco-2 monolayer, while saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) had no inhibitory effects. EPA and DHA inhibited cholesterol absorption in Caco-2 monolayer might be caused by down-regulating NPC1L1 mRNA and protein levels, which were associated with inhibition of SREBP-1/- 2 mRNA expression levels.

CONCLUSION

Results from this study indicate that functional food containing high PUFAs may have potential therapeutic benefit to reduce cholesterol absorption. Further studies on this topic may provide approaches to control lipid metabolism and to promote health.

Drug-transporter mediated interactions between anthelminthic and antiretroviral drugs across the Caco-2 cell monolayers

BACKGROUND

Drug interactions between antiretroviral drugs (ARVs) and anthelminthic drugs, ivermectin (IVM) and praziquantel (PZQ) were assessed by investigating their permeation through the Caco-2 cell monolayers in a transwell. The impact of anthelminthics on the transport of ARVs was determined by assessing the apical to basolateral (AP → BL) [passive] and basolateral to apical (BL → AP) [efflux] directions alone, and in presence of an anthelminthic. The reverse was conducted for the assessment of the influence of ARVs on anthelminthics.

METHODS

Samples from the AP and BL compartments were taken at 60, 120, 180 and 240 min and quantified either by HPLC or radiolabeled assay using a liquid scintillating counter for the respective drugs. Transepithelial resistance (TEER) was used to assess the integrity of the monolayers. The amount of compound transported per second (apparent permeability, Papp) was calculated for both AP to BL (PappAtoB), and BL to AP (PappBtoA) movements. Samples collected after 60 min were used to determine the efflux ratio (ER), quotient of secretory permeability and absorptive permeability (PappBL-AP/PappAP-BL). The reverse, (PappAP-BL/PappBL-AP) constituted the uptake ratio. The impact of SQV, EFV and NVP on the transport of both IVM and PZQ were investigated. The effect of LPV on the transport of IVM was also determined. The influence of IVM on the transport of SQV, NVP, LPV and EFV; as well as the effect PZQ on the transport of SQV of was also investigated, and a two-tailed p value of <0.05 was considered significant.

RESULTS

IVM significantly inhibited the efflux transport (BL → AP movement) of LPV (ER; 6.7 vs. 0.8, p = 0.0038) and SQV (ER; 3.1 vs. 1.2 p = 0.00328); and increased the efflux transport of EFV (ER; 0.7 vs. 0.9, p = 0.031) suggesting the possibility of drug transporter mediated interactions between the two drugs. NVP increased the efflux transport of IVM (ER; 0.8 vs. 1.8, p = 0.0094).

CONCLUSIONS

The study provides in vitro evidence of potential interactions between IVM, an anthelminthic drug with antiretroviral drugs; LPV, SQV, NVP and EFV. Further investigations should be conducted to investigate the possibility of in vivo interactions.

Models for drug absorption from the small intestine: where are we and where are we going?

The small intestine is a complex organ with movements, flora, mucus and flows. Despite this, the most widely used absorption models consider the organ a cylindrical monoepithelial tube. This review presents the recent evolution of models to take into consideration the complex nature of gut physiology. The most commonly encountered issues are ethical (in vivo models) and differences in drug transport as a result of a modified expression of drug transporters or metabolic enzymes compared with human (in vitro and in vivo models). Finally, this review discusses the way forward to reach an ideal equilibrium between reproducibility, predictability and efficiency for predicting permeability. The features of an ideal model are listed as a guideline for future development.

Toxicokinetics of Polar Chemicals in Zebrafish Embryo (Danio rerio): Influence of Physicochemical Properties and of Biological Processes

The time-resolved uptake of 17 nonionic and ionic polar compounds (logD ≤ 2) with a diversity of functional groups into zebrafish embryos (ZFE) was studied over 96 h of exposure. Among them were pharmaceuticals, pesticides and plant active ingredients. Uptake rates for the diffusion controlled passive uptake through the ZFE membrane ranged from 0.02 to 24 h(-1) for the nonionic compounds and were slower for ionic compounds (<0.008-0.08 h(-1)). The study compounds did not enrich much in the ZFE (median bioconcentration factor of 1, max. 7). Biotransformation significantly influenced the internal concentration of some of the test compounds over time (benzocaine, phenacetin, metribuzin, phenytoin, thiacloprid, valproic acid). For benzocaine, valproic acid and phenacetin several transformation products (TPs) were observed by LC-MS already at early life-stages (before 28 hpf); for benzocaine the TPs comprised >90% of the initial amount taken up into the ZFE. For six compounds internal concentrations remained very low (rel. int. conc. < 0.2). Besides biotransformation (sulfamethoxazole), poor membrane permeability (cimetidine, colchicine) and also affinity to efflux transporters (atropine and chloramphenicol) are the likely reasons for these low internal concentrations. This study outlines that the uptake of polar compounds into ZFE is influenced by their physicochemical properties. However, biological processes, biotransformation and, likely, efflux can strongly affect the internal concentrations already in early developmental stages of the ZFE. This should be considered in future toxicokinetic modeling. The evaluation of the toxicity of chemicals by ZFE requires toxicokinetic studies of the test compounds and their TPs to increase comparability to effects in fish.

Intracellular accumulation of Praziquantel in T lymphoblastoid cell lines, CEM (parental) and CEMVBL(P-gp-overexpressing)

Background

Praziquantel (PZQ) is an antihelminthic drug whose P-glycoprotein (P-gp) substrate specificity has not been conclusively characterized. We investigated its specificity by comparing its in vitro intracellular accumulation in CEM (parental), and CEMvbl cells which over express P-gp, a drug efflux transporter. Saquinavir (SQV), a known substrate of efflux transporters was used as control.

Methods

A reversed phase liquid chromatography method was developed to simultaneously quantify PZQ and SQV in cell culture media involving involved a liquid - liquid extraction followed by ultra-high performance liquid chromatography using a Hypurity C₁₈ column and ultraviolet detection set at a wavelength of 215 nm. The mobile phase consisted of ammonium formate, acetonitrile and methanol (57:38:5 v/v). Separation was facilitated via isocratic elution at a flow rate of 1.5 ml/min, with clozapine (CLZ) as internal standard. This was validated over the concentration range of 1.6 to 25.6 μM for all analytes. Intracellular accumulation of SQV in CEMvbl was significantly lower compared to that in CEM cells (0.1 ± 0.031 versus 0.52 ± 0.046, p = 0.03 [p <0.05]).

Results

Accumulation of PZQ in both cell lines cells were similar (0.05 ± 0.005 versus 0.04 ± 0.009, p = 0.4) suggesting that it is not a substrate of P-gp in CEM cells. In presence tariquidar, a known inhibitor of P-gp, the intracellular accumulation of SQV in CEMvbl cells increased (0.52 ± 0.068 versus 0.61 ± 0.102, p = 0.34 in CEM cells and 0.09 ± 0.015 versus 0.56 ± 0.089, p = 0.029 [p < 0.05] in CEMvbl cells). PZQ did not significantly affect the accumulation of SQV in either CEM (0.52 ± 0.068 versus 0.54 ± 0.061, p = 0.77), or in CEMvbl cells (0.09 ± 0.015 versus 0.1 ± 0.031, p = 0.89) cells compared to tariquidar, implying that PZQ is not an inhibitor of P-gp in CEMvbl cells.

Conclusions

PZQ is neither a substrate nor an inhibitor of the efflux drug transporter P-gp in T-lymphoblastoid cells, CEM and CEMvbl. We also report a simple, accurate and precise method for simultaneous quantification of PZQ and SQV.

Functionalized Mesoporous Silica Nanoparticle with Antioxidants as a New Carrier That Generates Lower Oxidative Stress Impact on Cells

Mesoporous silica nanoparticles (MSNs) were covalently coated with antioxidant molecules, namely, caffeic acid (MSN-CAF) or rutin (MSN-RUT), in order to diminish the impact of oxidative stress induced after transfection into cells, thus generating safer carriers used for either drug delivery or other applications. Two cellular models involved in the entry of NPs in the body were used for this purpose: the intestinal Caco-2 and the epidermal HaCaT cell lines. Rutin gave the best results in terms of antioxidant capacities preservation during coupling procedures, cellular toxicity alleviation, and decrease of ROS level after 24 h incubation of cells with grafted nanoparticles. These protective effects of rutin were found more pronounced in HaCaT than in Caco-2 cells, indicating some cellular specificity toward defense against oxidative stress. In order to gain more insight about the Nrf2 response, a stable transfected HaCaT cell line bearing repeats of the antioxidant response element (ARE) in front of a luciferase reporter gene was generated. In this cell line, both tBHQ and quercetin (Nrf2 agonists), but not rutin, were able to induce, in a dose-dependent fashion, the luciferase response. Interestingly, at high concentration, MSN-RUT was able to induce a strong Nrf2 protective response in HaCaT cells, accompanied by a comparable induction of HO-1 mRNA. The level of these responses was again less important in Caco-2 cells. To conclude, in keratinocyte cell line, the coupling of rutin to silica nanoparticles was beneficial in term of ROS reduction, cellular viability, and protective effects mediated through the activation of the Nrf2 antioxidant pathway.

Influence of Chitosan Nanoparticles as the Absorption Enhancers on Salvianolic acid B In vitro and In vivo Evaluation

Background:

Salvianolic acid B (SalB) represents the most abundant and bio-active phenolic constituent among the water-soluble compounds of Salvia miltiorrhiza. But the therapeutic potential of SalB has been significantly restricted by its poor absorption.

Methods:

In this study, chitosans (CS) and CS nanoparticles (NPs) with different molecular weights (MWs), which have influence on the absorption of SalB, was also investigated.

Results:

As a preliminary study, water-soluble CS with various MWs (3, 30, 50, and 100 kDa) was chosen. We investigated the MW-dependent Caco-2 cell layer transport phenomena in vitro of CS and NPs at concentrations (4 μg/ml, w/v). SalB, in presence CS or NPs has no significant toxic effect on Caco-2 cell. As the MW increases, the absorption enhancing effect of CS increases. However, as the MW decreases, the absorption enhancing effect of NPs increases. The AUC_0–∞ of the SalB-100 kDa CS was 4.25 times greater than that of free SalB. And the AUC_0–∞ of the SalB-3 kDa NPs was 16.03 times greater than that of free SalB.

Conclusion:

CS and NPs with different MWs as the absorption enhancers can promote the absorption of SalB. And the effect on NPs is better than CS.

SUMMARY

Formation mechanism for NPs

Multiparametric temporal analysis of the Caco-2/TC7 demonstrated functional and differentiated monolayers as early as 14 days of culture

Reducing the differentiation period for obtaining an in vitro intestinal barrier model is required to reduce the duration and cost for drug screening assays. In this frame, the Caco-2/TC7 subclone differentiation state was investigated from day 0 (D0) to day 32 (D32). As such, the expression of 45 genes (including cell junction, cell polarization, cell functionality, drug transport and metabolism genes) was followed throughout the 32 days. In parallel, the monolayer polarization and the formation of the cellular junctions were characterized by the immuno-staining of occludin, claudin-1 and actin proteins. The cell monolayer permeability was analyzed via transepithelial electric resistance measurements and paracellular transport of Lucifer Yellow. The P-gp efflux efficiency was assessed by rhodamine 123 transport. Alkaline phosphate activity was quantified to assess the cell differentiation. Three stages of differentiation were observed using the clustering of principal component analysis of the RTqPCR data and the overall assays. From D0 to D10, cells were in a proliferation stage and under-differentiated; from D14 to D21 a stable differentiation stage was reached; from D25 to D32 the epithelium seemed to enter into a post-differentiated stage. This study demonstrates that Caco-2/TC7 cells are functional and ready for use in drug screening permeability assays from 14 days in culture when compared with conventional 21 days for Caco-2 cells. In addition, this study provides a refined set of data allowing temporal and multi scale investigations, due to the intracellular kinetics and mRNA levels that can be correlated with membrane protein kinetics and functional extracellular activities. Therefore, shorter time in culture combined with a better knowledge of the cells during the time in culture will in turn help to improve the quality and cost of Caco-2/TC7 assays for drug development.

Biotransformation in vitro: An essential consideration in the quantitative in vitro-to-in vivo extrapolation (QIVIVE) of toxicity data

Early consideration of the multiplicity of factors that govern the biological fate of foreign compounds in living systems is a necessary prerequisite for the quantitative in vitro-in vivo extrapolation (QIVIVE) of toxicity data. Substantial technological advances in in vitro methodologies have facilitated the study of in vitro metabolism and the further use of such data for in vivo prediction. However, extrapolation to in vivo with a comfortable degree of confidence, requires continuous progress in the field to address challenges such as e.g., in vitro evaluation of chemical-chemical interactions, accounting for individual variability but also analytical challenges for ensuring sensitive measurement technologies. This paper discusses the current status of in vitro metabolism studies for QIVIVE extrapolation, serving today's hazard and risk assessment needs. A short overview of the methodologies for in vitro metabolism studies is given. Furthermore, recommendations for priority research and other activities are provided to ensure further widespread uptake of in vitro metabolism methods in 21st century toxicology. The need for more streamlined and explicitly described integrated approaches to reflect the physiology and the related dynamic and kinetic processes of the human body is highlighted i.e., using in vitro data in combination with in silico approaches.