Current methodologies used for evaluation of intestinal permeability and absorption

Application of Lipophilic Prodrug Charge Masking Strategy to Obtain Novel, Potential Oxytocin Prodrugs

A Lipophilic Prodrug Charge Masking (LPCM) strategy involves masking of hydrophilic peptide charges with alkoxycarbonyl groups, which are cleaved by esterases after intestinal absorption. This study investigates the LPCM strategy's applicability to oxytocin (OT), a peptide with well-defined biological activity. A series of OT prodrugs with varying alkoxycarbonyl chain lengths (2 to 12 carbon atoms) were synthesized, and their permeability was assessed using parallel artificial membrane permeability assay (PAMPA) and Caco-2 cell culture models. The PAMPA results indicated that OT demonstrated poor permeability (Papp = 2.2 × 10-6 cm/s), while its prodrugs Hoc-OT, Oct-OT, and Dec-OT were characterized by significantly better permeability, with Dec-OT achieving a four-fold increase over OT. The prodrug with a 12-carbon chain (Dod-OT) exhibited poor permeability; however, its high mass retention suggests strong membrane affinity. Further evaluation, using the Caco-2 cell model, revealed a 1.8-fold higher Papp of Oct-OT compared to OT, indicating possible higher oral availability. Conversely, Hoc-OT exhibited lower permeability than OT. Our findings indicate that the LPCM strategy can effectively boost the oral bioavailability of certain peptides, paving the way for their transformation into bioavailable drugs.

Comparative analysis of Caco-2 cells and human jejunal and duodenal enteroid-derived cells in gel- and membrane-based barrier models of intestinal permeability

Intestinal absorption is a key toxicokinetics parameter. Although the colon carcinoma cell line Caco-2 is the most used in vitro model to estimate human drug absorption, models representing other intestinal segments are available. We characterized the morphology, tissue-specific markers, and functionality of 3 human intestinal cell types: Caco-2, primary human enteroid-derived cells from jejunum (J2), and duodenum (D109) when cultured in the OrganoPlate 3-lane 40 microphysiological system (MPS) or static 24-well Transwells. In both conditions, J2 and D109 formed dome-like structures; Caco-2 formed uniform monolayers. In MPS, only Caco-2 formed tubules. Cells grown on Transwells formed a thicker monolayer. All cells and conditions exhibited expression of ZO-1 (tight junctions). Polarization markers Ezrin and Villin were highest in J2 and D109 in MPS, highest expression of Mucin was observed with J2. However, J2 and D109 exhibited poor barrier (70 kDa TRITC-dextran) in MPS, whereas robust barrier was recorded in Transwells. Barrier function and drug transport were evaluated using caffeine, indomethacin, and propranolol. The gel lane in MPS acted as a blockade; only a small fraction crossed, even without cells. The permeability ratios were used to parameterize the probabilistic compartmental absorption model to determine whether in vitro data could reduce uncertainty. The most accurate prediction of the fraction absorbed was achieved with Transwell-derived data from Caco-2, combined with the experimentally derived segment-specific absorption ratios. The impact of this study includes demonstration that enteroid-derived cells cultured in MPS show most physiological morphology, but that studies of drug permeability in this MPS are challenging.

Permeability Benchmarking: Guidelines for Comparing in Silico, in Vitro, and in Vivo Measurements

Permeability is a measure of the degree to which cells can transport molecules across biological barriers. Units of permeability are distance per unit time (typically cm/s), where accurate measurements are needed to define drug delivery in homeostasis and to model dysfunction occurring during disease. This perspective offers a set of community-led guidelines to benchmark permeability data across multidisciplinary approaches and different biological contexts. First, we lay out the analytical framework for three methodologies to calculate permeability: in silico assays using either transition-based counting or the inhomogeneous-solubility diffusion approaches, in vitro permeability assays using cells cultured in 2D or 3D geometries, and in vivo assays utilizing in situ brain perfusion or multiple time-point regression analysis. Then, we demonstrate a systematic benchmarking of in silico to both in vitro and in vivo, depicting the ways in which each benchmarking is sensitive to the choices of assay design. Finally, we outline seven recommendations for best practices in permeability benchmarking and underscore the significance of tailored permeability assays in driving advancements in drug delivery research and development. Our exploration encompasses a discussion of "generic" and tissue-specific biological barriers, including the blood-brain barrier (BBB), which is a major hurdle for the delivery of therapeutic agents into the brain. By addressing challenges in reconciling simulated data with experimental assays, we aim to provide insights essential for optimizing accuracy and reliability in permeability modeling.

Bioaccessibility and bioavailability assessment of cadmium in rice: In vitro simulators with/without gut microbiota and validation through in vivo mouse and human data

Assessing the bioaccessibility and bioavailability of cadmium (Cd) is crucial for effective evaluation of the exposure risk associated with intake of Cd-contaminated rice. However, limited studies have investigated the influence of gut microbiota on these two significant factors. In this study, we utilized in vitro gastrointestinal simulators, specifically the RIVM-M (with human gut microbial communities) and the RIVM model (without gut microbial communities), to determine the bioaccessibility of Cd in rice. Additionally, we employed the Caco-2 cell model to assess bioavailability. Our findings provide compelling evidence that gut microbiota significantly reduces Cd bioaccessibility and bioavailability (p<0.05). Notably, strong in vivo-in vitro correlations (IVIVC) were observed between the in vitro bioaccessibilities and bioavailabilities, as compared to the results obtained from an in vivo mouse bioassay (R2 = 0.63-0.65 and 0.45-0.70, respectively). Minerals such as copper (Cu) and iron (Fe) in the food matrix were found to be negatively correlated with Cd bioaccessibility in rice. Furthermore, the results obtained from the toxicokinetic (TK) model revealed that the predicted urinary Cd levels in the Chinese population, based on dietary Cd intake adjusted by in vitro bioaccessibility from the RIVM-M model, were consistent with the actual measured levels (p > 0.05). These results indicated that the RIVM-M model represents a potent approach for measuring Cd bioaccessibility and underscore the crucial role of gut microbiota in the digestion and absorption process of Cd. The implementation of these in vitro methods holds promise for reducing uncertainties in dietary exposure assessment.

Comparison of in vitro screening methods for evaluating the effects of pharmaceutical excipients on membrane permeability

The effects of pharmaceutical excipients on intestinal drug absorption have been highlighted and careful excipient selection is required to develop biologically equivalent formulations. This study aimed to evaluate the effects of excipients on drug permeability and compare the characteristics of in vitro screening methods. Three in vitro models, the commercial precoated parallel artificial membrane permeability assay (PAMPA), PermeaPadTM, and Caco-2 monolayer, were used to evaluate the effects of 14 excipients on the permeability of several drugs with different biopharmaceutical classification system classes. Concentration-dependent effects were analyzed to distinguish non-specific effects. The permeability of low-permeability drugs was increased by excipients such as hydroxypropyl cellulose and povidone K30 in the precoated PAMPA model, whereas PermeaPadTM maintained membrane integrity at higher concentrations. Conversely, croscarmellose sodium and sodium lauryl sulfate (SLS) decreased the permeability of highly permeable drugs in both precoated PAMPA and PermeaPadTM assays in a concentration-dependent manner. In Caco-2 monolayer assays, most excipients showed minimal effects on drug permeability. However, SLS significantly reduces the permeability of highly permeable drugs at concentrations above the critical micelle concentration, thereby compromising the integrity of the cell monolayer. Our results suggested that most of excipients, except SLS, did not affect the membrane permeation of drugs at clinically used concentrations. The pre-coated PAMPA model demonstrated high sensitivity to excipient effects, making it suitable for conservative evaluation. The PermeaPadTM and Caco-2 models allowed assessment at higher excipient concentrations, with PermeaPadTM being particularly useful for excipients that cause toxicity in Caco-2 cells.

Lipid nanoparticles for enhancing oral bioavailability

In recent studies, lipid nanoparticles have attracted attention as drug delivery systems owing to their preeminent potential in achieving the desired bioavailability of biopharmaceutics (BCS) class II and class IV drugs. The current debate concerns the bioavailability of these poorly absorbed drugs with their simultaneous oral degradation. Lipid nanoparticles, including solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), are lipid-based carrier systems that can effectively encapsulate both lipophilic and hydrophilic drugs, offering versatile drug delivery systems. The unique properties of lipids (biodegradability and biocompatibility) and their transportation pathways enhance the biological availability of drugs. These particles can increase the gastrointestinal absorption and solubilization of minimally bioavailable drugs via a selective lymphatic pathway. This review mainly focuses on providing a brief update on lipid nanoparticles (LNPs) that synergistically increase the bioavailability of limited permeable drugs and highlight the transversal mechanisms of LNPs across the gastrointestinal hurdles, transmembrane absorption, transport kinetics, and computational tools. Finally, the present hurdles and future perspectives of LNPs for oral drug delivery systems are discussed.

Designing an effective dissolution test for bilayer tablets tailored for optimal melatonin release in sleep disorder management

This project aims to investigate the release performance of bilayer tablet (BL-Tablet) designed with both fast and slow-release technology, targeting sleep disorders. The tablet incorporates Melatonin, extracts of Eschscholzia californica and Melissa officinalis. In order to validate the effectiveness of the extended-release profile, an advanced dissolution test was herein proposed. This new method utilizes biorelevant intestinal fluid media and incorporates a stomach-to-intestine fluid changing (SIFC) system. To demonstrate the advantages of employing this method for assessing the controlled release profile of active ingredients, the dissolution results were compared with those obtained using the conventional EU Pharmacopoeia approach. Furthermore, the comparative analysis was extended to include a monolayer tablet version (ML-Tablet) lacking the slow-release technology. Technological characterization and bioaccessibility studies, including intestinal permeability test, were conducted as well to assess the pharmacological performance and bioavailability of active ingredients. The dissolution data recovered revealed that the two dissolution methods did not exhibit any significant differences in the release of ML-Tablet's. However, the dissolution profile of the BL-Tablet exhibited notable differences between the two methods particularly when assessing the behavior of the slow-release layer. In this scenario, both methods initially exhibited a similar release pattern within the first approximately 0.5 h, driven by the fast-release layer of the tablet. Following this, distinct gradual and sustained releases were observed, spanning 2.5 h for the EU Pharmacopoeia method and 8 h for the new SIFC-biorelevant dissolution method, respectively. Overall, the novel method demonstrated a substantial improvement compared to conventional EU Pharmacopoeia test in evaluating the performance of a controlled slow-release technology. Remarkably, the prolonged release technology did not have an adverse impact on melatonin intestinal absorption, and, consequently, maintaining its potential bioavailability of around 78%. Concluding, this research provides valuable insights into how the innovative dissolution test can assist formulators in developing controlled release formulations.

Anti-leishmanial activity of Eleutherine plicata Herb. and predictions of isoeleutherin and its analogues

Introduction: Leishmaniasis is caused by protozoa of the genus Leishmania, classified as tegumentary and visceral. The disease treatment is still a serious problem, due to the toxic effects of available drugs, the costly treatment and reports of parasitic resistance, making the search for therapeutic alternatives urgent. This study assessed the in vitro anti-leishmanial potential of the extract, fractions, and isoeleutherin from Eleutherine plicata, as well as the in silico interactions of isoeleutherin and its analogs with Trypanothione Reductase (TR), in addition to predicting pharmacokinetic parameters. Methods: From the ethanolic extract of E. plicata (EEEp) the dichloromethane fraction (FDEp) was obtained, and isoeleutherin isolated. All samples were tested against promastigotes, and parasite viability was evaluated. Isoeleutherin analogues were selected based on similarity in databases (ZINK and eMolecules) to verify the impact on structural change. Results and Discussion: The extract and its fractions were not active against the promastigote form (IC50 > 200 μg/mL), while isoeleutherin was active (IC50 = 25 μg/mL). All analogues have high intestinal absorption (HIA), cell permeability was moderate in Caco2 and low to moderate in MDCK. Structural changes interfered with plasma protein binding and blood-brain barrier permeability. Regarding metabolism, all molecules appear to be CYP3A4 metabolized and inhibited 2-3 CYPs. Molecular docking and molecular dynamics assessed the interactions between the most stable configurations of isoeleutherin, analogue compound 17, and quinacrine (control drug). Molecular dynamics simulations demonstrated stability and favorable interactions with TR. In summary, fractionation contributed to antileishmanial activity and isoleutherin seems to be promising. Structural alterations did not contribute to improve pharmacokinetic aspects and analogue 17 proved to be more promising than isoeleutherin, presenting better stabilization in TR.

Model-Informed Drug Development: In Silico Assessment of Drug Bioperformance following Oral and Percutaneous Administration

The pharmaceutical industry has faced significant changes in recent years, primarily influenced by regulatory standards, market competition, and the need to accelerate drug development. Model-informed drug development (MIDD) leverages quantitative computational models to facilitate decision-making processes. This approach sheds light on the complex interplay between the influence of a drug's performance and the resulting clinical outcomes. This comprehensive review aims to explain the mechanisms that control the dissolution and/or release of drugs and their subsequent permeation through biological membranes. Furthermore, the importance of simulating these processes through a variety of in silico models is emphasized. Advanced compartmental absorption models provide an analytical framework to understand the kinetics of transit, dissolution, and absorption associated with orally administered drugs. In contrast, for topical and transdermal drug delivery systems, the prediction of drug permeation is predominantly based on quantitative structure-permeation relationships and molecular dynamics simulations. This review describes a variety of modeling strategies, ranging from mechanistic to empirical equations, and highlights the growing importance of state-of-the-art tools such as artificial intelligence, as well as advanced imaging and spectroscopic techniques.

Magnetic and/or Radiopaque Functionalization of Self-Unfolding Foils for Improved Applicability within Oral Drug Delivery

Various types of microfabricated devices have been proposed for overcoming the gastrointestinal (GI) challenges associated with oral administration of pharmaceutical compounds. However, unidirectional drug release in very close forced proximity to the intestinal wall still appears to be an unresolved issue for many of these microdevices, which typically show low drug absorption and thereby low bioavailabilities. This work explores how recently developed and promising self-unfolding foils (SUFs) can be magnetically and/or radiopaquely (M/R-) functionalized, by the addition of BaSO4 or Fe3O4 nanoparticles, for improving their applicability within oral drug delivery. Through surface characterization, mechanical testing, and X-ray imaging, the (M/R-)SUFs are generally inspected and their overall properties compared. Furthermore, R-SUFs are being used in an in vivo rat X-ray imaging study, whereas in situ rat testing of MR-SUFs are attempted together with an investigation of their general magnetic properties. Unfolding of the R-SUF, and its very close forced proximity to the small intestine, is very easily observed 2 h post-administration by applying both computed tomography scanning and planar X-ray imaging. In addition, MR-SUFs show a great magnetic response in water, which suggests the possibility for controlled motion and retention in the GI tract. However, the magnetic response does not seem strong enough for in situ rat testing, but most likely a strong magnetization of the MR-SUFs using for example an impulse magnetizer can be made for increasing the magnetic response. All of the results presented herein are highly relevant and applicable for future usage of (M/R-)SUFs, as well as similar devices, in pre-clinical studies and potential clinical trials.

Optimization and evaluation of Lisinopril mucoadhesive sustained release matrix pellets: In-vitro and ex-vivo studies

Lisinopril (LIS) is antihypertensive drug, classified as a class III drug with high water solubility and low permeability. To overcome the low permeability, 3² factorial designs aimed to formulate LIS as a sustained-release (LIS-SR) matrix pellet by extrusion/spheronization. Matrix pellets were composed of wet mass containing Avicel® and polymeric matrix polymers (sodium alginate (SA) and chitosan (CS)). Evaluation of the effect of two independent variables, matrix-forming units (SA and CS) on mean line torque, on pellet size, dissolution rate after 6 h, and mucoadhesion strength of the pellets were assessed using Statgraphics software. The tested formulations (F1-F9) showed that mean line torque ranged from 1.583 to 0.461 Nm, with LIS content in the LIS-SR pellets ranged from 87.9 to 103%, sizes varied from 1906 to 1404 µm and high percentages of drug released from pellets formulations (68.48 to 74.18 %), while the mean zeta potential value of mucoadhesive range from -17.5 to -22.9 mV. The selection of optimized formulation must have the following desirability: maximum peak torque, maximum pellets' particle size, and minimum % LIS release after 6hr. LIS optimized sustained release pellet formula composed of 2,159 % SA and 0.357 % CS was chosen as optimized formula. It's showed a 1.055 Nm mean line torque was responsible for the increased pellet size to 1830.8 μm with decreased release rate 56.2 % after 6 hr, and -20.33 mV average mucin zeta potential. Ex-vivo mucoadhesion studies revealed that that the optimize formulation, exhibited excellent mucoadhesive properties, after 1 h, about 73% of the pellets were still attached to the mucus membrane. Additionally, ex-vivo permeation determination of LIS from the optimized LIS-SR formulation was found to be significantly higher (1.7-folds) as compared to free LIS. In conclusion: LIS-SR matrix pellets, prepared with an extrusion/spheronization have desirable excellent characteristics in-vitro and ex-vivo sustained-release pellet formulation of LIS-SR was able to sustain the release of LIS for up to 8 h.

Effect of the combination of Lactobacillus acidophilus (probiotic) with vitamin K3 and vitamin E on Escherichia coli and Staphylococcus aureus: An in vitro pathogen model

The gut microbiota plays a key role in maintaining health and regulating the host's immune response. The use of probiotics and concomitant vitamins can increase mucus secretion by improving the intestinal microbial population and prevent the breakdown of tight junction proteins by reducing lipopolysaccharide concentration. Changes in the intestinal microbiome mass affect multiple metabolic and physiological functions. Studies on how this microbiome mass and the regulation in the gastrointestinal tract are affected by probiotic supplements and vitamin combinations have attracted attention. The current study evaluated vitamins K and E and probiotic combinations effects on Escherichia coli and Staphylococcus aureus. Minimal inhibition concentrations of vitamins and probiotics were determined. In addition, inhibition zone diameters, antioxidant activities and immunohistochemical evaluation of the cell for DNA damage were performed to evaluate the effects of vitamins and probiotics. At the specified dose intervals, L. acidophilus and vitamin combinations inhibit the growth of Escherichia coli and Staphylococcus aureus. It could thus contribute positively to biological functions by exerting immune system‑strengthening activities.

Pharmacokinetic assessment of cefpodoxime proxetil in diabetic rats

Purpose

In diabetes, multi-organ level dysfunction arising from metabolic complications is reported to influence the pharmacokinetics (PK) profile of many drugs. Hence, the present study was planned in rats to evaluate the effect of diabetes on the PK profile of cefpodoxime, a widely prescribed oral antibiotic.

Method

PK profile of cefpodoxime was assessed after oral administration of cefpodoxime proxetil (10 and 20 mg/kg) and intravenous (i.v) administration of cefpodoxime sodium (10 mg/kg) in normal and streptozotocin induced diabetic rats. To evaluate the impact of diabetes on oral absorption and serum protein binding, in situ intestinal permeability and in vitro serum protein binding studies were performed for cefpodoxime using Single Pass Intestinal Perfusion model (SPIP) and ultracentrifugation technique, respectively.

Result

In diabetic rats, there was significant (p < 0.01) decrease in maximum concentration (Cmax) and area under the curve (AUC) of cefpodoxime by both oral and intravenous route, which was attributed to augmented clearance of cefpodoxime. There was no change in the time to achieve Cmax (Tmax) suggesting no alteration in oral absorption which was further confirmed through unaltered intestinal permeability in diabetic rats. The protein binding in diabetic rats also remained unchanged, indicating no influence of protein binding on elevated clearance.

Conclusion

The plasma exposure of cefpodoxime, a renally eliminated drug was significantly lowered in diabetic rats due to enhanced glomerular filtration. However, this observation needs to be confirmed through well controlled clinical trials.

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.

Experimental and computational models to investigate intestinal drug permeability and metabolism

Oral administration is the preferred route for drug administration that leads to better therapy compliance. The intestine plays a key role in the absorption and metabolism of oral drugs, therefore, new intestinal models are being continuously proposed, which contribute to the study of intestinal physiology, drug screening, drug side effects, and drug-drug interactions.Advances in pharmaceutical processes have produced more drug formulations, causing challenges for intestinal models. To adapt to the rapid evolution of pharmaceuticals, more intestinal models have been created. However, because of the complexity of the intestine, few models can take all aspects of the intestine into account, and some functions must be sacrificed to investigate other areas. Therefore, investigators need to choose appropriate models according to the experimental stage and other requirements to obtain the desired results.To help researchers achieve this goal, this review summarised the advantages and disadvantages of current commonly used intestinal models and discusses possible future directions, providing a better understanding of intestinal models.

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.

PAMAM Dendrimers: A Review of Methodologies Employed in Biopharmaceutical Classification

The oral route is the preferred way of drug administration for most drugs, whose treatment success is directly related to the compound intestinal absorption. This absorption process, in its turn, is influenced by several factors impacting the drug bioavailability, which is extremely dependent on the maximum solubility and permeability. However, optimizing these last two factors, without chemical structural modification, is challenging. Although poly(amidoamine) dendrimers (PAMAM) are an innovative and promising strategy as drug delivery compounds, there are few studies that determine the permeability and solubility of PAMAM-drugs derivatives. Considering this scenario, this paper aimed to carry out a literature review of the last five years concerning biopharmaceutical characterizations of dendrimer delivery systems. In vitro methodologies, such as the Parallel artificial membrane permeability assay (PAMPA) (non-cellular based model) and Caco-2 cells (cellular based model), used for the permeability evaluation in the early stages of drug discovery proved to be the most promising methodologies. As a result, we discussed, for instance, that through the usage of PAMPA it was possible to evaluate the higher capacity for transdermal delivery of DNA of TAT-conjugated PAMAM, when in comparison with unmodified PAMAM dendrimer with a P<0.05. We also presented the importance of choosing the best methods of biopharmaceutical characterization, which will be essential to guarantee the efficacy and safety of the drug candidate.

Elucidating the Role of Innate and Adaptive Immune Responses in the Pathogenesis of Canine Chronic Inflammatory Enteropathy-A Search for Potential Biomarkers

Simple Summary

Canine chronic inflammatory enteropathy (CIE) is a chronic disease affecting the small or large intestine and, in some cases, the stomach of dogs. This gastrointestinal disorder is common and is characterized by recurrent vomiting, diarrhea, and weight loss in affected dogs. The pathogenesis of IBD is not completely understood. Similar to human IBD, potential disease factors include genetics, environmental exposures, and dysregulation of the microbiota and the immune response. Some important components of the innate and adaptive immune response involved in CIE pathogenesis have been described. However, the immunopathogenesis of the disease has not been fully elucidated. In this review, we summarized the literature associated with the different cell types and molecules involved in the immunopathogenesis of CIE, with the aim of advancing the search for biomarkers with possible diagnostic, prognostic, or therapeutic utility.

Abstract

Canine chronic inflammatory enteropathy (CIE) is one of the most common chronic gastrointestinal diseases affecting dogs worldwide. Genetic and environmental factors, as well as intestinal microbiota and dysregulated host immune responses, participate in this multifactorial disease. Despite advances explaining the immunological and molecular mechanisms involved in CIE development, the exact pathogenesis is still unknown. This review compiles the latest reports and advances that describe the main molecular and cellular mechanisms of both the innate and adaptive immune responses involved in canine CIE pathogenesis. Future studies should focus research on the characterization of the immunopathogenesis of canine CIE in order to advance the establishment of biomarkers and molecular targets of diagnostic, prognostic, or therapeutic utility.

Luciferase assay system to monitor fibroblast growth factor signal disruption in human iPSCs

We describe a protocol for a live-cell luciferase assay system for continuously monitoring fibroblast growth factor (FGF) signal disruption in human-induced pluripotent stem cells (iPSCs). Signal disrupting effects of chemicals are used as an indicator to evaluate toxicity. The assay is reliably predictive of the effects of limb malformation chemicals (AUC = 0.93). The current approach is limited to FGF signal disruption, and combinations with other types of signaling will be required to detect the effects of different toxicants. For complete details on the use and execution of this protocol, please refer to Kanno et al. (2022a).

Novel bioavailability-based risk assessment of Cd in earthworms and leeches utilizing in vitro digestion/Caco-2 and MDCK cells

In the present study, the oral bioavailability of cadmium (Cd) in earthworms and leeches was investigated through in vitro physiologically based extraction test (PBET) digestion/Caco2 and MDKC cell models. We are the first to create an innovative assessment strategy which has capacity to offer a more precise evaluation of Cd-associated health risks in traditional animal medicines (TAMs), by combinational usage of bioavailable Cd levels, the duration and frequency of the exposure to TAMs obtained by questionnaire data, as well as safety factor of TAMs. Our data showed that the percentage of bioavailability for Caco-2 cells in earthworms and leeches ranged from 3.29 to 14.17% and 4.32 to 12.61%, respectively. The percentage of bioavailability of MDCK cells in earthworms and leeches ranged from 4.83 to 15.74% and 6.53 to 15.04%, respectively. After adjusting by the bioavailability of Cd to target hazard quotient (THQ), excitingly, our findings manifested that the health risks induced by the ingestion of earthworms and leeches were acceptable in the clinic. Our key findings suggest that bioavailability characterization cannot be ruled out and health risks should be assessed on the basis of the bioavailable Cd levels rather than total levels. Our novel strategy provides insight into the bio-accumulation of Cd in organisms as well as a more realistic and accurate assessment of Cd-associated health risks in TAMs, with the main purpose of improving public health by scientifically using TAMs.

Recent advance of <i>in vitro</i> models in natural phytochemicals absorption and metabolism

Natural phytochemicals absorption and metabolic process are mainly in the human gut. Simulating the absorption and metabolism of natural phytochemicals in vitro to predict the rate and degree of absorption of natural phytochemicals provides convenience for many researchers. However, in this process, many physiological factors <i>in vitro</i> are affected, such as stomach and intestinal juice composition, pH, intestinal transmission rate and so on. In recent years, the research methods have gradually improved to make these models more suitable for the natural phytochemicals absorption process, <i>in vitro</i> simulation models have become an essential means to study natural phytochemicals absorption. Therefore, this paper introduces the advantages and disadvantages of commonly used <i>in vitro</i> simulation models of natural phytochemicals absorption and metabolism, as well as briefly introduces the working principle of each model. To provide a theoretical basis for simulating natural phytochemicals absorption <i>in vitro</i> and development and utilization of natural phytochemicals.

The Study of the Transport Mechanism of Isorhynchophylline in Liver

To investigate the transport mechanism of isorhynchophylline (IRN) by using the specific inhibitors of organic cation transporters (OCTs) and organic anion transporting polypeptides (OATPs) and attempt illustrate the metabolic mechanism of IRN in the liver. All animals were randomly divided into three groups: control group (only inject IRN), RIF group (inject IRN and rifampicin), and ADR group (inject IRN and adrenalone). The control group was injected with IRN via the caudal vein. The RIF group was injected with rifampicin (RIF) by gavage, and after 1 h, IRN was injected into the caudal vein. Similarly, the ADR group received adrenalone by the caudal vein, and after 0.5 h, IRN was injected into the caudal vein. Thereafter, blood samples were obtained by the heart punctures at 90 min, 180 min, and 300 min following drug administration. Rats were sacrificed at 300 min after drug administration; then, the liver tissue was harvested. The level of IRN was measured by using high-performance liquid chromatography (HPLC), and the Kp values were calculated. After RIF administration (OATPs inhibitors), the Kp value of IRN was slightly decreased when compared with that of the control group. Meanwhile, the Kp value of IRN was dramatically reduced compared to that of the control group following ADR administration (OCTs inhibitors). The results suggested that OCTs have mainly participated in the hepatic uptake process of IRN.

Bioaccessibility and bioavailability adjusted dietary exposure of cadmium for local residents from a high-level environmental cadmium region

The critical health risks caused by cadmium (Cd) via dietary exposure are commonly assessed by detecting Cd concentrations in foods. Differently, in this study, the bioaccessibility and bioavailability of Cd in major local harvests were introduced to assess the dietary exposure of local residents from a high-level environmental Cd region. The results indicated that certain Cd was released into the digestive juice after in vitro digestion with a bioaccessibility of 20-63% for rice and 3-32% for leafy vegetables, and the released portion was partially absorbed by Caco-2 cells with a bioavailability of 2-21% for rice and 0.2-13% for leafy vegetables. The results obtained from the toxicokinetic model revealed that the predicted urinary Cd values from the estimated daily intake (EDI) of Cd, which accounted for bioaccessibility and bioavailability, were consistent with the actual measured values, and the EDIs were considerably lower than the acceptable daily intake. This suggests that the bioaccessibility and bioavailability adjusted dietary Cd exposure should be more precise. The key issues addressed in our study implores that a potential health risk cannot be neglected in people with high consumption of rice from high-level zone.

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.

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.

Bovine plasma hydrolysates' iron chelating capacity and its potentiating effect on ferritin synthesis in Caco-2 cells

The low bioavailability of iron is one factor that contributes to its deficiency in the human diet. For this reason, it is necessary to find compounds that can form iron chelates so that these can be added to foods that contain iron to improve its bioavailability at the intracellular level. In this study, we assessed the relationship between bovine plasma hydrolysates' iron chelating ability and their degree of hydrolysis. The hydrolysate with the highest chelating capacity was fractionated and each fraction's chelating capacity was subsequently assessed. Each fraction's effect on ferritin synthesis in Caco-2 cells was also determined. The results showed that bovine plasma hydrolysates with a degree of hydrolysis of 19.1% have an iron chelating capacity of 38.5 ± 0.4% and increase the synthesis of ferritin in Caco-2 cells five-fold compared to the control. This may be due to the fact that these hydrolysates contain amino acids such as Leu, Lys, Glu, Ala, Asp, Val, Thr, Cys and Phe, which may be responsible for binding iron to the hydrolysate, increasing its solubility and the consequent uptake by Caco-2 cells.

Synthesis and Evaluation of PEG-PR for Water Flux Correction in an In Situ Rat Perfusion Model

Phenol red (PR) is a widely used marker for water flux correction in studies of in situ perfusion, in which intestinal absorption usually leads to the underestimation of results. In this paper, we propose a novel marker polyethylene glycol (PEG)-PR (i.e., PR modified by PEGylation) with less permeability and evaluate its application in an in situ perfusion model in rats. PEG-PR was synthesized by the chemical conjunction of polyethylene glycol-4k/5k (PEG-4k/5k) and PR. The synthesized PEG-PR was then characterized using ¹H-NMR, ¹³C-NMR, ultraviolet (UV), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analyses. The low permeability of PEG-PR was assessed using everted gut sac (EGS) methods. The apparent permeability coefficients (P_app, 3–8 × 10⁻⁷ cm/s) of PEG4k/5k-PR exhibited a nearly 15-fold reduction compared to that of PR. The different concentrations of PEG4k/5k-PR did not contribute to the P_app value or cumulative permeable percentage (about 0.02–0.06%). Furthermore, the larger molecular weight due to PEGylation (PEG5k-PR) enhanced the nonabsorbable effect. To evaluate the potential application of the novel marker, atenolol, ketoprofen, and metoprolol, which represent various biopharmaceutics classification system (BCS) classes, were selected as model drugs for the recirculation perfusion method. The water flux corrected by PEG4k/5k-PR reflected the accuracy due to the nonabsorbable effect, while the effective intestinal membrane permeability (P_eff) of atenolol corrected by PEG4k/5k-PR showed a statistically significant increase (p < 0.05) in different intestinal segments. In conclusion, PEG-PR is a promising marker for the permeability estimation when using the in situ perfusion model in rats.

Hop bioactive compounds in prevention of nutrition-related noncommunicable diseases

Nutrition-related noncommunicable diseases (NR-NCDs) such as cardiovascular disease and type 2 diabetes both negatively impact the quality of life of many individuals and generate a substantial burden on society, demonstrating a need for intervention. Phytochemicals are investigated as a potential approach for combating NR-NCDs, and those found in hops have gained increased attention in recent decades. Hops, the strobile of the plant Humulus lupulus, are grown primarily for the brewing industry as they confer taste and increased shelf-life. The bitter acids represent the main compounds of interest for improving beer quality. Additionally, bitter acids as well as the prenylated chalcone xanthohumol, exhibit a wide range of health beneficial properties. This review summarizes those beneficial effects of bitter acids and xanthohumol on NR-NCDs, including inflammatory and immune diseases, obesity and metabolic disorders, as well as cancer prevention.

In Silico Prediction of Intestinal Permeability by Hierarchical Support Vector Regression

The vast majority of marketed drugs are orally administrated. As such, drug absorption is one of the important drug metabolism and pharmacokinetics parameters that should be assessed in the process of drug discovery and development. A nonlinear quantitative structure-activity relationship (QSAR) model was constructed in this investigation using the novel machine learning-based hierarchical support vector regression (HSVR) scheme to render the extremely complicated relationships between descriptors and intestinal permeability that can take place through various passive diffusion and carrier-mediated active transport routes. The predictions by HSVR were found to be in good agreement with the observed values for the molecules in the training set (n = 53, r² = 0.93, q CV 2 = 0.84, RMSE = 0.17, s = 0.08), test set (n = 13, q² = 0.75-0.89, RMSE = 0.26, s = 0.14), and even outlier set (n = 8, q² = 0.78-0.92, RMSE = 0.19, s = 0.09). The built HSVR model consistently met the most stringent criteria when subjected to various statistical assessments. A mock test also assured the predictivity of HSVR. Consequently, this HSVR model can be adopted to facilitate drug discovery and development.

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.

The Evaluation of Valsartan Biopharmaceutics Properties

BACKGROUND

Solubility, intestinal permeability and dissolution are the main factors that govern the rate and extent of drugs absorption and are directly related to bioavailability. Biopharmaceutics Classification System (BCS) is an important tool which uses in vitro results for comparison with bioavailability in vivo (biowaiver). Valsartan is widely used in the treatment of hypertension and shows different BCS classification in the literature (BCS class II or III).

OBJECTIVE

This work proposes the study of valsartan biopharmaceutics properties and its BCS classification.

METHODS

High Performance Liquid Chromatography (HPLC) method was developed and validated to quantify the drug in buffers pH 1.2, 4.5 and 6.8 respectively. Valsartan solubility was determined in these three different media using shake flask method and intrinsic dissolution rate. Evaluation of dissolution profile from coated tablets was conducted.

RESULTS

The low solubility (pH 1.2 and 4.5) and high solubility (pH 6.8) were observed for both solubility methods. Permeability data reported from the literature showed that valsartan is a low permeability drug. Valsartan presented the rapid release profile only in pH 6.8.

CONCLUSION

We defined that valsartan is a class IV drug, in disagreement with what has been published so far. It is important to emphasize that the conditions considered here are indicated to define the biopharmaceutics classification by regulatory agencies.

The fate of dietary advanced glycation end products in the body: from oral intake to excretion

Advanced glycation end products (AGEs), which are closely associated with various chronic diseases, are formed through the Maillard reaction when aldehydes react with amines in heated foods or in living organisms. The fate of dietary AGEs after oral intake plays a crucial role in regulating the association between dietary AGEs and their biological effects. However, the complexity and diversity of dietary AGEs make their fate ambiguous. Glycated modifications can impair the digestion, transport and uptake of dietary AGEs. High and low molecular weight AGEs may exhibit individual differences in their distribution, metabolism and excretion. Approximately 50-60% of free AGEs are excreted after dietary intake, whereas protein-bound AGEs exhibit a limited excretion rate. In this article, we summarize several AGE classification criteria and their abundance in foods, and in the body. A standardized static in vitro digestion method is strongly recommended to obtain comparable results of AGE digestibility. Sophisticated hypotheses regarding the intestinal transportation and absorption of drugs, as well as calculated physicochemical parameters, are expected to alleviate the difficulties determining the digestion, transport and uptake of dietary AGEs. Orally supplied AGEs with low or high molecular weights must be supported by well-defined amounts in investigations of excretion. Furthermore, unequivocal evidence should be obtained regarding the degradation and metabolism products of dietary AGEs.

Repaglinide-loaded nanostructured lipid carriers with different particle sizes for improving oral absorption: preparation, characterization, pharmacokinetics, and in situ intestinal perfusion

Repaglinide-loaded nanostructured lipid carriers (REP-NLCs) with different particle sizes were successfully designed and prepared to investigate the permeation and absorption ability by in situ single-pass intestinal perfusion (SPIP) study and pharmacokinetics. Both of the formulations prepared by solvent diffusion method exhibited a spherical shape under transmission electron microscopy (TEM) and similar zeta potential value of –11 mV. The particles size, encapsulation efficiency (EE), drug loading (DL) of REP-NLCs-Small and REP-NLCs-Large size preparations were about 79 nm and 325 nm, 96.83% and 98.60%, 4.41% and 3.05%, respectively. Besides, both REP-NLCs showed good colloidal stability and had no burst release phenomenon compared with REP-Sol. SPIP demonstrated the improved membrane permeability for NLCs compared with REP-Sol, especially NLCs-Small size preparation. The bioavailability increased sequentially in REP-Sol, REP-NLCs-Large, and REP-NLCs-Small, and the difference between each other was statistical significant. Our investigations demonstrate that NLCs with small particles size of 50–100 nm, such as 79 nm, are able to enhance absorption performance of a poorly soluble repaglinide compared with large particles size, such as 325 nm, by significantly improving the absorption in jejunum, and colon of rats and thus well improving oral bioavailability.

Effectiveness of absorption and passage through the small intestine, as a model of oral prolactin administration

The process of absorption and permeation of PRL through the small intestine of 1-day-old piglet from the different compositions of solutions prepared for oral administration was investigated. This was achieved by determining the effect of hormone concentration (0.25 mg / ml or 0.5 mg / ml or 0.75 mg / ml), the concentration of stabilizing substances - trehalose (6 mg / ml or 12 mg / ml or 18 mg / ml) and mannitol (6 mg / ml or 12 mg / ml or 18 mg / ml) and the pH of the solution (2.5 or 3.0 or 3.5) on the degree of absorption and permeation of the PRL. The conditions for the absorption and penetration of PRL from solutions of various compositions for oral administration through the natural membrane (small intestine of the 1-day-old sucking piglet) in the in vivo conditions were simulated. The studies used an in vivo model in which the enzymatic profile in the body is not yet fully developed (no pepsin). It was found that in the studied range the absorption of PRL in the small intestine of the 1-day-old sucking piglet is significantly related to the concentration of the hormone and trehalose in the solution from which it is absorbed. In contrast, all factors studied (hormone concentration, trehalose and mannitol concentration, pH value of the solution) influence the process of penetration of the PRL in the studied range. It was also found that the hormone concentration significantly influences the rate of its absorption and permeation (the fastest occurs at a concentration of 0.5 mg/mL). The results suggest possibility of oral prolactin administration in order to ensure proper growth, development and increase the resistance and survival of sucking piglets.

Reviewing the mechanisms of natural product-drug interactions involving efflux transporters and metabolic enzymes

The World Health Organization (WHO) and other worldwide health agencies have recently taken initiatives to encourage the use of traditional medicine and/or complementary/alternative medicine in order to promote well-being and public health. In this way, one of the WHO's concerns is the safe use of these therapies. Phytotherapy is a strategy consisting of the use of medicinal plants (MP) and/or herbal medicinal products (HMP) for medicinal purposes. The use of phytotherapy concomitantly with drugs may cause interactions compromising the expected pharmacological action or generating toxic effects. These interactions are complex processes that may occur with multiple medications targeting different metabolic pathways, and involving different compounds present in MP and HMP. Thus, the aim of this review was to summarize the main MP- and HMP-drug interactions that involve specific transporters (P-glycoprotein and BCRP) and CYP450 enzymes (CYP3A4 and CYP2D6), which play relevant roles in the mechanisms of interactions. Firstly, multiple databases were used to search studies describing in vitro or in vivo MP and HMP-drug interactions and, after that, a systematic note-taking and appraisal of the literature was conducted. It was observed that several MP and HMP, metabolic pathways and transcription factors are involved in the transporters and enzymes expression or in the modulation of their activity having the potential to provide such interactions. Thus, the knowledge of MP- and HMP-drug interaction mechanisms could contribute to prevent harmful interactions and can ensure the safe use of these products to help the establishment of the therapeutic planning in order to certify the best treatment strategy to be used.

Nanofibrous Scaffolds Support a 3D in vitro Permeability Model of the Human Intestinal Epithelium

Advances in drug research not only depend on high throughput screening to evaluate large numbers of lead compounds but also on the development of in vitro models which can simulate human tissues in terms of drug permeability and functions. Potential failures, such as poor permeability or interaction with efflux drug transporters, can be identified in epithelial Caco-2 monolayer models and can impact a drug candidate's progression onto the next stages of the drug development process. Whilst monolayer models demonstrate reasonably good prediction of in vivo permeability for some compounds, more developed in vitro tools are needed to assess new entities that enable closer in vivo in vitro correlation. In this study, an in vitro model of the human intestinal epithelium was developed by utilizing nanofibers, fabricated using electrospinning, to mimic the structure of the basement membrane. We assessed Caco-2 cell response to these materials and investigated the physiological properties of these cells cultured on the fibrous supports, focusing on barrier integrity and drug-permeability properties. The obtained data illustrate that 2D Caco-2 Transwell® cultures exhibit artificially high trans-epithelial electrical resistance (TEER) compared to cells cultured on the 3D nanofibrous scaffolds which show TEER values similar to ex vivo porcine tissue (also measured in this study). Furthermore, our results demonstrate that the 3D nanofibrous scaffolds influence the barrier integrity of the Caco-2 monolayer to confer drug-absorption properties that more closely mimic native gut tissue particularly for studying passive epithelial transport. We propose that this 3D model is a suitable in vitro model for investigating drug absorption and intestinal metabolism.