Rat, ovine and bovine Peyer's patches mounted in horizontal diffusion chambers display sampling function

Evaluation of Selenomethionine Entrapped in Nanoparticles for Oral Supplementation Using In Vitro, Ex Vivo and In Vivo Models

Selenium methionine (SeMet) is an essential micronutrient required for normal body function and is associated with additional health benefits. However, oral administration of SeMet can be challenging due to its purported narrow therapeutic index, low oral bioavailability, and high susceptibility to oxidation. To address these issues, SeMet was entrapped in zein-coated nanoparticles made from chitosan using an ionic gelation formulation. The high stability of both the SeMet and selenomethionine nanoparticles (SeMet-NPs) was established using cultured human intestinal and liver epithelial cells, rat liver homogenates, and rat intestinal homogenates and lumen washes. Minimal cytotoxicity to Caco-2 and HepG2 cells was observed for SeMet and SeMet-NPs. Antioxidant properties of SeMet were revealed using a Reactive Oxygen Species (ROS) assay, based on the observation of a concentration-dependent reduction in the build-up of peroxides, hydroxides and hydroxyl radicals in Caco-2 cells exposed to SeMet (6.25–100 μM). The basal apparent permeability coefficient (Papp) of SeMet across isolated rat jejunal mucosae mounted in Ussing chambers was low, but the Papp was increased when presented in NP. SeMet had minimal effects on the electrogenic ion secretion of rat jejunal and colonic mucosae in Ussing chambers. Intra-jejunal injections of SeMet-NPs to rats yielded increased plasma levels of SeMet after 3 h for the SeMet-NPs compared to free SeMet. Overall, there is potential to further develop SeMet-NPs for oral supplementation due to the increased intestinal permeability, versus free SeMet, and the low potential for toxicity.

Best practices in current models mimicking drug permeability in the gastrointestinal tract - an UNGAP review

The absorption of orally administered drug products is a complex, dynamic process, dependent on a range of biopharmaceutical properties; notably the aqueous solubility of a molecule, stability within the gastrointestinal tract (GIT) and permeability. From a regulatory perspective, the concept of high intestinal permeability is intrinsically linked to the fraction of the oral dose absorbed. The relationship between permeability and the extent of absorption means that experimental models of permeability have regularly been used as a surrogate measure to estimate the fraction absorbed. Accurate assessment of a molecule's intestinal permeability is of critical importance during the pharmaceutical development process of oral drug products, and the current review provides a critique of in vivo, in vitro and ex vivo approaches. The usefulness of in silico models to predict drug permeability is also discussed and an overview of solvent systems used in permeability assessments is provided. Studies of drug absorption in humans are an indirect indicator of intestinal permeability, but in vitro and ex vivo tools provide initial screening approaches are important tools for direct assessment of permeability in drug development. Continued refinement of the accuracy of in silico approaches and their validation with human in vivo data will facilitate more efficient characterisation of permeability earlier in the drug development process and will provide useful inputs for integrated, end-to-end absorption modelling.

Oral absorption of peptides and nanoparticles across the human intestine: Opportunities, limitations and studies in human tissues

In this contribution, we review the molecular and physiological barriers to oral delivery of peptides and nanoparticles. We discuss the opportunities and predictivity of various in vitro systems with special emphasis on human intestine in Ussing chambers. First, the molecular constraints to peptide absorption are discussed. Then the physiological barriers to peptide delivery are examined. These include the gastric and intestinal environment, the mucus barrier, tight junctions between epithelial cells, the enterocytes of the intestinal epithelium, and the subepithelial tissue. Recent data from human proteome studies are used to provide information about the protein expression profiles of the different physiological barriers to peptide and nanoparticle absorption. Strategies that have been employed to increase peptide absorption across each of the barriers are discussed. Special consideration is given to attempts at utilizing endogenous transcytotic pathways. To reliably translate in vitro data on peptide or nanoparticle permeability to the in vivo situation in a human subject, the in vitro experimental system needs to realistically capture the central aspects of the mentioned barriers. Therefore, characteristics of common in vitro cell culture systems are discussed and compared to those of human intestinal tissues. Attempts to use the cell and tissue models for in vitro-in vivo extrapolation are reviewed.

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

The epithelial barrier is the first innate defense of the gastrointestinal tract and selectively regulates transport from the lumen to the underlying tissue compartments, restricting the transport of smaller molecules across the epithelium and almost completely prohibiting epithelial macromolecular transport. This selectivity is determined by the mucous gel layer, which limits the transport of lipophilic molecules and both the apical receptors and tight junctional protein complexes of the epithelium. In vitro cell culture models of the epithelium are convenient, but as a model, they lack the complexity of interactions between the microbiota, mucous-gel, epithelium and immune system. On the other hand, in vivo assessment of intestinal absorption or permeability may be performed, but these assays measure overall gastrointestinal absorption, with no indication of site specificity. Ex vivo permeability assays using "intestinal sacs" are a rapid and sensitive method of measuring either overall intestinal integrity or comparative transport of a specific molecule, with the added advantage of intestinal site specificity. Here we describe the preparation of intestinal sacs for permeability studies and the calculation of the apparent permeability (Papp) of a molecule across the intestinal barrier. This technique may be used as a method of assessing drug absorption, or to examine regional epithelial barrier dysfunction in animal models of gastrointestinal disease.

Ingested (oral) anti-IL-12/23 inhibits EAE

BACKGROUND

Blocking the activity of IL-12/23 can inhibit autoimmune diseases such as psoriasis.

OBJECTIVE

We examined whether an antibody against IL-12/23, ustekinumab (UTZ) (Stelera®), used clinically in psoriasis would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with isotype IgG control or UTZ during ongoing disease. Splenocytes, CD4(+) T cells or macrophages/monocyte lineage cells (CD11b(+)) from control fed or UTZ fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease. Actively fed and recipient mice were examined for disease inhibition, inflammation, and cytokine responses.

RESULTS

Ingested (oral) UTZ inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from UTZ fed donors protected against actively induced disease and decreased inflammation. Oral UTZ decreased pro-inflammatory cytokines Th1-like cytokines IL-2, IL-12, IFN-γ, IL-17 (Teff) and TNF-α in UTZ fed mice and increased counter-regulatory cytokines IL-4, IL-10 and IL-13 in recipients of donor cells from UTZ fed mice.

CONCLUSIONS

Ingested (orally administered) UTZ can inhibit disease, CNS inflammation, decrease pro-inflammatory Th1-like and Th17 cytokines and increase Th2-like anti-inflammatory cytokines.

Development of a versatile in vitro method for understanding the migration of Fasciola hepatica newly excysted juveniles

Fasciola hepatica is a parasitic trematode that causes serious losses to livestock producers, and also zoonotic disease. The limitations of chemotherapy for the control of fasciolosis have led to significant interest in the development of vaccines to protect cattle and sheep from infection. However, relatively few studies have concentrated on the mechanisms of invasion of the gut by newly excysted juvenile liver flukes (NEJ) and the host response triggered by this event. The aim of this work was to develop an in vitro model to study invasion by NEJ, while also reducing the requirement for challenge infections of experimental animals. Fasciola hepatica metacercariae were excysted in vitro and placed into compartments containing rat distal jejunal sheets. Variations in incubation medium, chamber size and incubation temperature were used to identify optimal conditions for NEJ migration across the gut. Histological examination showed increased migration until 120 min post-incubation. The use of RPMI, without gassing at 39 °C, as the incubation medium was found to be optimal, with 40·5% of NEJ migrating after 150 min. This study describes a readily-reproducible method for studying the migration of F. hepatica NEJ within the definitive host. It will be useful for identifying potential drug and vaccine targets.

Gnotobiotic Human Colon Ex Vivo

Background

A novel emulsion with efficacy as an agent for eliminating biofilms was selected. The aim of this study was to examine efficacy and effect of a formulation of ML:8 against commensal bacteria harvested from ex vivo human colonic tissues.

Methods

Mucosal sheets, obtained at the time of surgery, were exposed for 2 minutes to one of four solutions: Krebs-Hensleit (KH) solution, saline (NaCl; 0.9%), povidone iodine (1%), or ML:8 (2%); n = 4. Lumenal surfaces were swabbed for culture under aerobic or anaerobic conditions. Following treatment, each sheet was mounted in Ussing chambers and voltage clamped. Tissues were challenged with carbachol. Permeability coefficient (Papp) was determined using mannitol fluxes. At the end of each experiment, tissues were examined histologically.

Results

Similar colony forming units grew in aerobic and anaerobic conditions in both control and NaCl treated tissues. Iodine reduced and ML:8 virtually abolished viable bacteria. Basal electrophysiological parameters were not different between treatments. Transepithelial electrical resistance values did not differ between groups. All tissues responded to carbachol, although this was attenuated in iodine treated tissue. Papp values were slightly elevated in all treated tissues but this did not reach significance. Histopathological assessment revealed no overt damage to tissues.

Conclusion

Brief exposure to ML:8 reduced culturable bacterial burden from human intestinal tissues harvested at the time of surgical resection. Such gnotobiotic tissues retain structural and functional integrity. This is a novel approach to reduce bacterial burden.

Ingested (oral) thyrotropin releasing factor (TRH) inhibits EAE

BACKGROUND

Ingested immunoactive proteins type I IFN, SIRS peptide 1-21, α-MSH, ACTH, SST inhibit clinical attacks and inflammation in acute EAE by decreasing Th1-like cytokines, increasing Th2-like cytokines or increasing T(reg) cell frequencies.

OBJECTIVE

We examined whether another protein, thyrotropin releasing factor (TRH), would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or TRH during ongoing disease. Splenocytes from mock fed or TRH fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease.

RESULTS

Ingested (oral) TRH inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from TRH fed donors protected against actively induced disease and decreased inflammation. In actively fed mice, oral TRH decreased IL-17 and TNF-α cytokines in both the spleen and the CNS. In recipients of donor cells from TRH fed mice there was a reduction of Th1 and Th17 and induction of Th2-like IL-13 cytokines in both the spleen and CNS. Oral TRH decreased clinical score and decreased inflammatory foci in both actively fed and recipients of actively fed mice. There was no significant increase in T(reg) cell frequencies in actively fed or recipients of TRH fed donor cells.

CONCLUSIONS

Ingested (orally administered) TRH can inhibit clinical disease, inhibit CNS inflammation by decreasing Th1-like, Th17 and TNF-α cytokines and increasing Th2-like cytokines (IL-13) in the CNS.

The mycotoxin patulin increases colonic epithelial permeability in vitro

The gastrointestinal lumen is directly exposed to dietary contaminants, including patulin, a mycotoxin produced by moulds. Patulin is known to increase permeability across intestinal Caco-2 monolayers. This study aimed to determine the effect of patulin on permeability, ion transport and morphology in isolated rat colonic mucosae. Mucosal sheets were mounted in Ussing chambers and voltage clamped. Apical addition of patulin (100-500 μM) rapidly reduced transepithelial electrical resistance (TEER) and increased permeability to [(14)C] mannitol (2.9-fold). Patulin also inhibited carbachol-induced electrogenic chloride secretion and histological evidence of mucosal damage was observed. To examine potential mechanisms of action of patulin on colonic epithelial cells, high-content analysis of Caco-2 cells was performed and this novel, quantitative fluorescence-based approach confirmed its cytotoxic effects. With regard to time course, the cytotoxicity determined by high content analysis took longer than the almost immediate reduction of electrical resistance in isolated mucosal sheets. These data indicate patulin is not only cytotoxic to enterocytes but also has the capacity to directly alter permeability and ion transport in intact intestinal mucosae. These data corroborate and extend findings in intestinal cell culture monolayers, and further suggest that safety limits on consumption of patulin may be warranted.

Drug delivery to inflamed colon by nanoparticles: comparison of different strategies

For inflammatory bowel disease (IBD) treatment, local delivery of molecules loaded in nanoparticles to the inflamed colon could be a promising strategy. The aim of this study was to investigate how drug-loaded polymeric nanoparticles target the site of inflammation and to analyse the influence of different colon-specific delivery strategies. Three different polymeric nanoparticles were formulated using ovalbumin (OVA) as a model drug. pH-sensitive nanoparticles were made with Eudragit(®) S100. Mucoadhesive nanoparticles were created with trimethylchitosan (TMC). A mix of polymers, PLGA, PEG-PLGA and PEG-PCL, were used to obtain a sustained drug delivery. Furthermore, ligands targeting immune cells (i.e. mannose) or the inflamed colon (i.e. a specific peptide) were grafted on the PEG chain of PCL. Interaction of nanoparticles with the intestinal epithelium was explored using Caco-2 monolayers designed to mimic an inflamed epithelium and then visualized using confocal laser microscopy. TMC nanoparticles had the highest apparent permeability for OVA in the untreated model. However, in the inflamed model, there were no difference between TMC, PLGA-based and Eudragit(®) nanoparticles. The uptake of nanoparticles in the inflamed mouse colon was assessed in a horizontal diffusion chamber. Mannose-grafted PLGA nanoparticles showed the highest accumulation of OVA in inflamed colon. Based on these results, active targeting of macrophages and dendritic cells may be a promising approach for targeting the colon in IBD.

Ingested (oral) neuropeptide Y inhibits EAE

BACKGROUND

Ingested immunoactive proteins, type I IFN, SIRS peptide 1-21, α-MSH, ACTH, and SST inhibit clinical attacks and inflammation in acute EAE by decreasing Th1-like cytokines, increasing Th2-like cytokines or increasing T(reg) cell frequencies.

OBJECTIVE

We examined whether another protein, neuropeptide Y, would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or NPY during ongoing disease. Splenocytes from mock fed or NPY fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease.

RESULTS

Ingested (oral) NPY inhibited ongoing disease, and decreased inflammation. Adoptively transferred cells from NPY fed donors protected against actively induced disease and decreased inflammation. In actively fed mice, oral NPY decreased Th1-like cytokines and increased Th2-like IL-13 cytokines in both the spleen and the CNS. In recipients of donor cells from NPY fed mice there was a reduction of Th1 and Th17 and induction of Th2-like IL-13 cytokines in both the spleen and CNS. Oral NPY decreased clinical score and decreased inflammatory foci in both actively fed and recipients of actively fed mice. There was no significant increase in T(reg) cell frequencies in actively fed or recipients of NPY fed donor cells.

CONCLUSIONS

Ingested (orally administered) NPY can inhibit clinical disease, inhibit CNS inflammation by decreasing Th17 and Th1-like cytokines and increasing Th2-like cytokines in the CNS.

Distribution of immune cells and expression of interleukin receptors in ileal Peyer's patches of calves

Newborn calves lack a mature immune system. The immune system develops with age, but the role of the expression of cytokine receptors in the development of immune cells of Peyer's patches (PPs) in the intestines of calves in the first 2 months has not yet been elucidated. In this study, the distribution of immune cells and the expression of interleukin (IL) receptors (R) in the ileal PPs of newborn and 2-month-old calves were investigated immunohistochemically with monoclonal antibodies against bovine CD4, CD8, IgM, γδTCR, T19, WC3, WC5, and WC6 antigens. The expression of ILRs was examined with antibodies against CD25 (IL-2Rα), IL-2Rγ, IL-4R, IL-6R, IL-10R, and IL-13R antigens. CD4(+), CD8(+), γδTCR(+), T19(+), and WC6(+) cells were found to be more widely distributed in the ileal PPs of 2-month-old calves than in those of newborn calves. Moreover, the expression of CD25 (IL-2Rα), IL-4R, and IL-13R in the ileal PPs of 2-month-old calves was more prominent than that in newborn calves. These data suggest that the immune system of calves at 2 months of age is developed by reactions to foreign antigens and aging.

Effects of Lactobacillus plant arum on genes expression pattern in mice jejunal Peyer's patches

Jejunal Peyer's patches contain specialized epithelial M cells that take up ingested microorganisms from the lumen of the gut by transcytosis. Using DNA-micro array, we analyzed the gene expression patterns of jejunal Peyer's patches in order to gain insight into the molecular mechanism by which Lp6 interacted with the host organism in a gnotobiotic environment v. in the gut normal microflora. The micro array data revealed that, among approximately 14,000 genes, 420 were expressed in Lp6 administration group at twofold or higher levels compared to the control group. These included genes involved in immune response, and cell differentiation, cell-cell signaling, cell adhesion, signal transcription, and transduction. Real-time PCR confirmed the reliability of the analysis. These data indicated that administration of Lactobacillus Lp6 was associated with a complex genetic response in the jejunal Peyer's patches.

Effects of Lactobacillus salivarius 433118 on intestinal inflammation, immunity status and in vitro colon function in two mouse models of inflammatory bowel disease

The probiotic, Lactobacillus salivarius subsp. salivarius 433118 (UCC118), was investigated for its potential to attenuate colitis, modulate immune responses and alter intestinal barrier dysfunction in two different mouse models of inflammatory bowel disease (IBD). Following oral treatment with UCC118, faecal microbial analysis indicated that viable intact bacteria reached the colons of interleukin (IL)-10(-/-) mice and dextran sodium sulphate (DSS)-treated mice. Neither prophylactic nor therapeutic UCC118 treatment significantly prevented or attenuated inflammation in either model. In all studies, the probiotic-treated mice had comparable cytokine responses as vehicle-treated animals. Mannitol permeability was increased across colonic mucosae mounted in Ussing chambers from DSS-treated mice, but not in IL-10(-/-) mice. However, colonic mucosae from UCC118-treated mice had unchanged transepithelial electrical resistance (TEER) values and mannitol fluxes compared to controls. In two different mouse colitis models examined under a range of histological and functional criteria, the data therefore suggest that this Lactobacillus subsp. has limited potential as a prophylactic or therapeutic treatment for inflammatory bowel disease. While several studies have shown therapeutic activity for this probiotic in mouse models of IBD, our data suggest that there are inter-study variables in formulation, study design, animal models and assessment criteria that may impact on interpretation of probiotic efficacy.

Myosin light chain kinase inhibition: correction of increased intestinal epithelial permeability in vitro

PURPOSE

To examine whether myosin light chain kinase (MLCK) inhibitors can reduce intestinal epithelial permeability increases in vitro.

MATERIALS AND METHODS

Isolated rat, mouse and human colonic tissue mucosae and Caco-2 monolayers were exposed to cytochalasin D (cD) and sodium caprate (C10), in the absence and presence of the MLCK inhibitors, ML-9 and D PIK. Transepithelial electrical resistance (TEER) and Papp of [14C]-mannitol or FITC-dextran 4000 (FD-4) were measured. Western blots were used to measure MLC phosphorylation.

RESULTS

Increases in Papp of [14C]-mannitol and decreases in TEER were induced by tight junction openers. These changes were attenuated by ML-9. D-PIK offset the FD-4 Papp increase induced by C10 in Caco-2 only, while ML-9 and PIK inhibited MLC directly, cD induced constriction of peri-junctional actin in Caco-2 monolayers, but this was prevented by ML-9. Although mannitol fluxes across colonic mucosae from dextran-sulphate (DSS)-treated mice were higher than control, they were not ameliorated by either ML-9 or PIK in vitro.

CONCLUSIONS

ML-9 inhibits paracellular permeability increases in several intestinal epithelial models. D-PIK reduced stimulated paracellular fluxes in Caco-2 monolayers, but not in tissue. Pre-established increases were not modified by two MLCK inhibitors in a mouse model of IBD.

Increased intestinal permeability in rats subjected to traumatic frontal lobe percussion brain injury

BACKGROUND

Dysfunction of the gastrointestinal tract is a common occurrence after traumatic brain injury (TBI). We hypothesized that increased intestinal permeability may result from a precisely controlled percussion injury to the exposed brains of anesthetized rats and that such an effect could be assessed in vitro using excised intestinal mucosae mounted in Ussing chambers.

METHODS

After craniotomy over the left medial prefrontal cortex on anesthetized rats, neurotrauma was produced using a pneumatically driven impactor on the exposed brain. Control rats were subjected to identical procedures but did not receive an impact. Muscle-stripped rat intestinal ileal and colonic segments were mounted in Ussing chambers within 30 minutes of death. Transepithelial electrical resistance (TEER) and the apparent permeability coefficient (Papp) of [C]-mannitol were recorded from intestinal tissue for 120 minutes. Histopathologic analysis was also performed to determine any gross morphologic changes in the intestine.

RESULTS

Ileal and colonic mucosae showed no differences in TEER in ileum or colon of TBI rats compared with controls. The Papp of mannitol was significantly increased in ilea from rats previously exposed to TBI compared with controls. Histologic analysis showed gross changes to 50% of the ileal but not the colonic sections from TBI rats.

CONCLUSION

TBI results in significantly reduced ileal barrier function, most likely mediated by open tight junctions. For patients with acute head injury, this may have implications for subsequent oral absorption of nutrients. Systemic delivery of luminal endotoxins may contribute to multiple organ failure.

In vitro Interactions Between the Oral Absorption Promoter, Sodium Caprate (C10) and S. typhimurium in Rat Intestinal Ileal Mucosae

PURPOSE

The medium chain fatty acid, sodium caprate (C(10)), is a promising oral drug delivery agent that may promote permeability of peptides through increasing paracellular permeability of the intestinal epithelium. One safety concern is that it may permit co-absorption of by-stander agents including pathogens. The purpose of this in vitro study was to examine the effects of C(10) on rat intestinal ileal mucosae in the presence of co-administered Salmonella typhimurium in a low volume vertical Ussing chamber.

METHODS

C(10) or S. typhimurium was added to rat ileal mucosae mounted in chambers and the flux of the paracellular flux of [(14)C]-mannitol examined. S. typhimurium adherence and uptake by ileal mucosae was also examined by counting. Bacterial growth curves were assessed in the presence of C(10). Minimum inhibitory- and bacteriocidal concentrations of C(10) were determined against a range of bacteria.

RESULTS

Apical addition of either C(10) or S. typhimurium to rat ileal mucosae mounted in modified diffusion chambers significantly increased the flux of [(14)C]-mannitol in a concentration-dependent fashion. Co-exposure with increasing concentrations of C(10) attenuated the Salmonella-induced increase in mannitol flux. Histological evaluation revealed that C(10) inhibited both adhesion and invasion of S. typhimurium to intestinal mucosae. Short term bacterial growth studies in the presence of C(10) showed evidence of concentration-dependent inhibition. C(10) was bacteriocidal in mM concentrations against S. typhimurium and selected gram positive and negative bacteria.

CONCLUSIONS

C(10) does not promote the permeation of a common bacterium across isolated intestinal tissue upon acute co-exposure. It prevents S. typhimurium attachment to epithelia and impedes growth of a range of different bacterial strains.