An improved everted gut sac as a simple and accurate technique to measure paracellular transport across the small intestine

Study on the transport and internalisation mechanism of dietary supplement nattokinase in the small intestine using animal and Caco-2 cell monolayer models

Maintaining proper blood flow is critical to promoting good health. Nattokinase is a serine protease from Bacillus subtilis that has significant in vitro thrombolytic activity, but its mechanism as a dietary supplement to prevent thrombosis through intestinal absorption and transport is still unclear.The purpose of this study is to study the transport and internalisation mechanism of NK in the small intestine using animal models and Caco-2 cell monolayer models.This study first evaluated the preventive effect of supplementing low dose (4000 FU (Fibrin Unit)/kg, n = 6), medium dose (8000 FU/kg, n = 6), and high dose (12000 FU/kg, n = 6) of nattokinase on carrageenan induced thrombosis in mice. Subsequently, we used the rat gut sac model, ligated intestinal loop model, and Caco-2 cell uptake model to study the intestinal transport mechanism of NK.Results indicate that NK is a moderately absorbed biomolecule whose transport through enterocytes is energy- and time-dependent. Chlorpromazine, nystatin and EIPA all inhibited the endocytosis of NK to varying degrees, indicating that the endocytosis of NK in Caco-2 cells involves macropinocytosis, clathrin-mediated and caveolae-mediated pathway. These findings offer a theoretical basis for investigating the mechanism of oral NK supplementation in greater depth.

A Study on Pharmacokinetic Functionalities and Safety Margins of an Optimized Simvastatin Nanoformulation

A pharmaceutical formulation with favorable pharmacokinetic parameters is more likely to be efficacious and safe to overcome the failures of the drug resulting from lack of efficacy, poor bioavailability, and toxicity. In this view, we aimed to evaluate the pharmacokinetic functionalities and safety margin of an optimized CS-SS nanoformulation (F40) by in vitro/in vivo methods. The everted sac technique was used to evaluate the improved absorption of a simvastatin formulation. In vitro protein binding in bovine serum and mice plasma was performed. The formulation’s liver and intestinal CYP3A4 activity and metabolic pathways were investigated by the qRT-PCR technique. The excretion of cholesterol and bile acids was measured to demonstrate the formulation’s cholesterol depletion effect. Safety margins were determined by histopathology as well as fiber typing studies. In vitro protein binding results revealed the existence of a high percentage of free drugs (22.31 ± 3.1%, 18.20 ± 1.9%, and 16.9 ± 2.2%, respectively) compared to the standard formulation. The controlled metabolism in the liver was demonstrated from CYP3A4 activity. The formulation showed enhanced PK parameters in rabbits such as a lower Cmax, clearance, and a higher Tmax, AUC, Vd, and t1/2. qRT-PCR screening further proved the different metabolic pathways followed by simvastatin (SREBP-2) and chitosan (PPAR-γ pathway) in the formulation. The results from qRT-PCR and histopathology confirmed the toxicity level. Hence, this pharmacokinetic profile of the nanoformulation proved it has a unique synergistic hypolipidemic modality.

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.

Absorption of methionine sources in animals-is there more to know?

This literature review evaluates the absorption of methionine (Met) sources such as 2-hydroxy-4-methylthiobutyric acid (HMTBa), its calcium salts (HMTBa-Ca), and DL-methionine (DL-Met) by focusing on the state of knowledge regarding the absorption mechanism, experimental methodology, and factors affecting their absorption. The 2 Met sources differ in mechanism and site of absorption due to differences in their chemical characteristics and enzymatic conversion. This review addresses diffusion- and transport-mediated absorption systems for amino acids and carboxylic compounds, best elucidated by in vitro, ex vivo, and in vivo experimental models. Opportunities and limitations in the use of radioisotopes to depict absorption sites as well as host and microbial metabolism are described. Physiological and environmental conditions that lead to changes in gut absorptive capacity and the impact of Met source absorption are also evaluated. This review concludes that any comparison between HMTBa and DL-Met should consider their different behaviors during the absorption phase. Hence, the chemical characteristics of these 2 molecules entail different absorption sites and mechanisms, from passive absorption in the case of HMTBa and HMTBa-Ca to active transporters for DL-Met, HMTBa, and HMTBa-Ca. In addition, the different conversion modes of these 2 molecules further differentiate their absorption modes. Considering these important differences, it is easier to understand the apparent divergence between the conclusions of existing publications. When comparing these 2 molecules, it is recommended to properly adapt to the conditions under which the absorption of Met sources is evaluated.

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 Progress of Intestinal Epithelial Models from Cell Lines to Gut-On-Chip

Over the past years, several preclinical in vitro and ex vivo models have been developed that helped to understand some of the critical aspects of intestinal functions in health and disease such as inflammatory bowel disease (IBD). However, the translation to the human in vivo situation remains problematic. The main reason for this is that these approaches fail to fully reflect the multifactorial and complex in vivo environment (e.g., including microbiota, nutrition, and immune response) in the gut system. Although conventional models such as cell lines, Ussing chamber, and the everted sac are still used, increasingly more sophisticated intestinal models have been developed over the past years including organoids, InTESTine™ and microfluidic gut-on-chip. In this review, we gathered the most recent insights on the setup, advantages, limitations, and future perspectives of most frequently used in vitro and ex vivo models to study intestinal physiology and functions in health and disease.

Comparison of the effects of the intestinal permeation enhancers, SNAC and sodium caprate (C10): Isolated rat intestinal mucosae and sacs

SNAC and C₁₀ are intestinal permeation enhancers (PEs) used in formulations of peptides for oral delivery in clinical trials. Our aims were to compare their: (i) mechanism of action in isolated rat intestinal mucosae mounted in Ussing chambers and in non-everted gut sacs, (ii) effects on mucosa integrity in those models and also in in situ intra-jejunal instillations and (iii) interactions with intestinal mucus. SNAC increased the apparent permeability coefficient (P_app) of the paracellular marker, FITC-dextran 4000 (FD4), across isolated rat gastric mucosae in concentration-dependent fashion, whereas C₁₀ did not, while both reduced the transepithelial electrical resistance (TEER). In isolated jejunal and colonic mucosae, both agents increased the P_app of [¹⁴C]-mannitol and FD4 whereas C₁₀ but not SNAC reduced TEER. 20 mM SNAC was required to achieve the efficacy of 10 mM C₁₀ in jejunal and colonic mucosae. In isolated non-everted jejunal and colonics sacs, FD4 flux increases were observed in the presence of both PEs. Histology of mucosae revealed that both PEs induced minor epithelial damage to the mucosa at concentrations that increased fluxes. Jejunal tissue withstood epithelial damage in the following order: intra jejunal in situ instillations > jejunal sacs > isolated jejunal mucosae. Both PEs modulated viscoelastic properties of porcine jejunal mucus without altering rheological properties. In conclusion, SNAC and C₁₀ are reasonably efficacious PEs in rat intestinal tissue with common overall mechanistic features. Their potency and toxic potential are low, in agreement with clinical trial data.

Oral Insulin Delivery Using Poly (Styrene Co-Maleic Acid) Micelles in a Diabetic Mouse Model

The oral delivery of insulin is a convenient and safe physiological route of administration for management of diabetes mellitus. In this study, we developed a poly-(styrene-co-maleic acid) (SMA) micellar system for oral insulin delivery to overcome the rapid degradation of insulin in the stomach, improve its absorption in the intestine, and provide a physiologically-relevant method of insulin to reach portal circulation. The insulin was encapsulated into SMA micelles in a pH-dependent process. The charge and size of the nanoparticles were determined by dynamic light scattering. The insulin loading of the nanoparticles was measured by HPLC. The transport of the SMA-insulin through biological membranes was assessed in vitro using Caco-2 cells, ex vivo rat intestinal section, and in vivo in a streptozotocin-induced diabetes mouse model. SMA-insulin micelles were negatively charged and had a mean diameter of 179.7 nm. SMA-insulin efficiently stimulated glucose uptake in HepG-2 hepatic cells and was transported across the Caco-2 epithelial cells in vitro by 46% and ex vivo across intestinal epithelium by 22%. The animal studies demonstrated that orally-administered SMA-insulin can produce a hypoglycemic effect up to 3 h after administration of one dose. Overall, our results indicate that SMA micelles are capable of the oral delivery of bioactive compounds like insulin and can be effective tools in the management of diabetes.

Hydrophobic ion pair loaded self-emulsifying drug delivery system (SEDDS): A novel oral drug delivery approach of cromolyn sodium for management of bronchial asthma

The aim of the present study is to develop a self-emulsifying drug delivery system (SEDDS) for the hydrophobic ion pair (HIP) complex of cromolyn sodium (CS), in order to enhance its intestinal absorption and biological activity. Two ion pairing agents (IPAs) were investigated: hexadecyl pyridininum chloride (HPC) and myristyl trimethyl ammonium bromide (MTAB). The optimum binding efficiency for complexation between investigated IPAs and CS was observed at a molar ratio of 1.5:1, where CS binding efficiency was found to be 76.10 ± 2.12 and 91.37 ± 1.73% for MTAB and HPC, respectively. The two prepared complexes exhibited a significant increase in partition coefficient indicating increased lipophilicity. The optimized CS-HIP complex was incorporated into SEDDS formulations. SEDDS formulations F2 (40% oleic acid, 40% Brij^TM98, 20% propylene glycol) and F3 (25% oleic acid, 50% Brij^TM98, 25% propylene glycol) exhibited nanometric droplet diameters with monodisperse distribution and nearly neutral zeta potential values. Ex vivo intestinal permeation study, using the non-everted gut sac technique, revealed a significantly higher cumulative amount of permeated drug, after 2 h, for F2 and F3 (53.836 and 77.617 µg/cm², respectively) compared to 8.649 µg/cm² for plain CS solution. The in vivo evaluation of plain CS solution compared to F2 and F3 was conducted in an ovalbumin sensitization-induced bronchial asthma rat model. Lung function parameters (tidal volume and peak expiratory flow), biochemical parameters (interleukin-5, immunoglobulin-E, myeloperoxidase and airway remodelling parameters) were assessed in addition to histopathological examination. The results indicated the superiority of F3 followed by F2 compared to plain CS solution for prophylaxis of bronchial asthma in rats.

Role of semi-purified andrographolide from Andrographis paniculata extract as nano-phytovesicular carrier for enhancing oral absorption and hypoglycemic activity

Objective

Andrographis paniculata is a well-known medicinal plant in Southeast Asia, India and China. The plant contains andrographolide (AN), a very important phytochemical used in various health problems. However, AN is low in oral absorption bioavailability of AN due to the rapid clearance and high protein binding capacity.

Methods

The present study was aimed to develop a nano-phytovesicular formulation of semi-purified AN extracts from a naturally occurring phospholipid (soya phosphatidylcholine) in order to increase the oral absorption and antihyperglycemic activity in rats.

Results

The nano-phyto vesicle of semi-purified AN extracts equivalent to 25 mg /kg AN significantly protected the hyperglycemic condition of rats. The in vitro and in vivo experiments results proved that the nano- phytovesicular system of plant extracts containing AN produced better oral absorption, bioavailability and improved antihyperglycemic activity compared with that of free AN at dose of 50 mg/kg.

Conclusion

Hence, the prepared semi-purified extract nano-phytovesicular system is helpful in solving the problem of rapid clearance of AN.

Pharmacokinetic incompatibility of the Huanglian-Gancao herb pair

Background

Pharmacokinetic interaction is one of the most important indices for the evaluation of the compatibility of herbal medicines. Both Gancao (Glycyrrhizae Radix et Rhizoma) and Huanglian (Coptidis Rhizoma) are commonly used traditional Chinese medicines (TCMs). In this study, the influence of Gancao on the pharmacokinetics of Huanglian was systematically studied by using berberine as a pharmacokinetic marker.

Methods

Extracts of the herbal pieces of Huanglian and the herb pair (Huanglian plus Gancao) were prepared with boiling water. The concentration of berberine in the samples was analyzed using liquid chromatography-mass spectrometry. The total amounts of berberine in all extract samples were compared. Comparative pharmacokinetic studies of Huanglian and the herb pair were conducted in ICR mice. In vitro berberine absorption and efflux were studied using mice gut sacs. The equilibrium solubility of berberine in the extracts was determined. The in vitro dissolution of berberine was comparatively studied using a rotating basket method.

Results

Gancao significantly reduced berberine exposure in the portal circulation (425.8 ng·h/mL vs. 270.4 ng·h/mL) and the liver (29,500.8 ng·h/mL vs. 15,422.4 ng·h/mL) of the mice. In addition, Gancao decreased the peak concentration (C_max) of berberine in the portal circulation (104.3 ng·h/mL vs. 76.5 ng·h/mL) and liver (4926.1 ng·h/mL vs. 2642.8 ng·h/mL) of mice. Significant influences of Gancao on the amount of berberine extracted (32% reduction), the solubility of berberine (34.7% compared with the control group), and dissolution (88.7% vs. 66.1% at 15 min in acid buffer and 68% vs. 51.8% at 15 min in phosphate buffer) were also revealed. Comparative pharmacokinetic studies in ICR mice indicated that the formation of sediment was unfavorable in terms of berberine absorption (345.3 ng·h/mL vs. 119.8 ng·h/mL).

Conclusions

Gancao was able to reduce intestinal absorption and in vivo exposure of berberine in Huanglian via the formation of sediment, which caused reductions in the extracted amount, solubility, and dissolution of berberine.

Risk assessment and QbD based optimization of an Eprosartan mesylate nanosuspension: In-vitro characterization, PAMPA and in-vivo assessment

Quality by design (QbD) principles were implemented to understand the product and process variables of sonoprecipitation technique, for preparation of eprosartan mesylate (EM) nanosuspension. Quality risk management approach was utilized to identify and assess high-risk attributes affecting critical quality attributes (CQA's), prioritizing the number of experiments. The effect of critical material attributes (CMA's) and critical process parameters (CPP's) (soluplus concentration, drug concentration ultrasonication amplitude) on z-average particle size and PDI were investigated using a central composite face-centered design (CCF). Further, design space with criteria set of CMA's and CPP's was established to offer assurance of quality. The optimal formulation, identified using numerical optimization method, was further lyophilized and evaluated for redispersibility, solubility saturation, dissolution kinetic and in-vitro dissolution behavior. The EM nanoparticles were in an amorphous state as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The stability study conducted for a span of 6 months attests physical and chemical stability of EM dry nanosuspension in an amorphous state when stored at 4 °C. The enhanced solubility and in-vitro dissolution of EM nanosuspension may be attributed to the reduced particle size and alteration of the physical state from a crystalline to an amorphous state. Further, the optimized formulation was subjected to in-vitro and ex-vivo transport study using parallel artificial membrane permeability assay (PAMPA) and rat everted gut sac model respectively. The transport studies revealed successful permeation enhancement of EM nanoparticle when compared with EM API and physical mixture (PM). The absolute bioavailability of EM API was 7.1% and improved to 39.9% for EM nanosuspension, suggesting that nanoformulation had overcome solubility and permeability limited bioavailability which was observed with EM API.

Physiology of the Gut: Experimental Models for Investigating Intestinal Fluid and Electrolyte Transport

Once thought to be exclusively an absorptive tissue, the intestine is now recognized as an important secretory tissue, playing a key role in body ion and fluid homeostasis. Given the intestine's role in fluid homeostasis, it is not surprising that important clinical pathologies arise from imbalances in fluid absorption and secretion. Perhaps the most important examples of this can be seen in enterotoxigenic secretory diarrheas with extreme fluid secretion, and Cystic Fibrosis with little or no fluid secretion. A mechanistic understanding of the cellular pathways regulating ion and fluid transport has been obtained from a variety of approaches and model systems. These have ranged from the intact intestine to a single intestinal epithelial cell type. Although for many years a reductionist approach has held sway for investigating intestinal transport, the growing realization that physiologic processes should really be examined within a physiological context has seen a marked increase in studies using models that are essentially mini-intestines in a dish. The aim of this chapter is to provide a historical context for our understanding of intestinal ion and fluid transport, and to highlight the model systems that have been used to acquire this knowledge.

Enhancement of gut permeation of amoxicillin with Nigella sativa seed extract and its phytochemical screening

The seeds of Nigella sativa Linn. (Ranunculaceae), commonly known as Black cumin, are predominantly used as carminative, antispasmodic, and stimulant. The main objective of the present study was to evaluate the effect of N. sativa seed extract on the permeation of co-infused amoxicillin across the gut wall. The methanolic extract of N. sativa improved intestinal permeability of amoxicillin in in-vitro experiments in a dose-dependent manner. Two new glycosides, decanyl nigelloic acid diglucoside [n-decanyl-3-aldehydic-4-methoxy-5-hydroxy benzoate-5-β-D-glucofuranosyl (2→1)-β-D-glucopyranosyl-(2→1)-β-D-glucopyranoside]] and nigelabdienoyl triglucoside [homo-labd-5, 9(11)-dien-16-onyl-β-D-glucopyranosyl (2→1)-β-D-glucopyranosyl (2→1)-β-D-glucopyranoside], along with seven known fatty acid glycerides/esters, were isolated from the gut permeation enhancing extract. The structures of these new glycosides were elucidated by detailed spectroscopic analyses.

Role of MAPKs in HSP70's Protection against Heat Stress-Induced Injury in Rat Small Intestine

Aim

To evaluate the role of heat shock protein 70 (HSP70) on the MAPK pathway activation with quercetin treatment and its protection against small intestine impairments of heat stressed rats.

Methods

Forty-eight male Sprague-Dawley rats aged 6 weeks were randomized to three groups (n=16/group), namely, control (CON), heat stress (HS), and heat stress + quercetin (HQ). The experiment lasted for 14 days with daily 50 min of heat stress treatment (43°C) for the HS and HQ groups. Rats of HQ group were intragastrically given 0.5 ml quercetin solution (50 mg/kg body weight) before the heat stress treatment. Half of the animals were sacrificed on day 7 and the rest on day 14 for tissue sampling. Intestinal morphology, small intestine morphology and permeability, protein expression of HSP70, phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and caspase-3 activity were examined.

Results

Heat stress caused morphological damage to the small intestine and increased intestinal permeability. HSP70 expression and MAPK activity in the small intestine were increased by heat stress. Inhibition of HSP70 by quercetin did not change intestinal permeability compared with the HS group but aggravated intestinal injury and affected the activation of MAPKs and caspase-3.

Conclusions

HSP70 may modulate stress-activated signaling and acts in a protective manner via MAPK signaling. Affecting HSP70 protective mechanisms could be useful for protection against heat stress-induced injury in rat small intestine.

Preclinical models for colonic absorption, application to controlled release formulation development

Oral controlled release (CR) formulations have many benefits and have become a valuable resource for the local and systemic administration of drugs. The most important characteristic of these pharmaceutical products is that drug absorption occurs mainly in the colon. Therefore, this review analyses the physiological and physicochemical features that may affect an orally administered CR product, as well as the different strategies to develop a CR dosage form and the methods used to evaluate the formulation efficacy. The models available to study the intestinal permeability and their applicability to colonic permeability determinations are also discussed.

Transporter Gene Expression and Transference of Fructose in Broiler Chick Intestine

Recent studies have suggested that a high-fructose diet leads to the development of metabolic syndrome in mammals. However, relatively little information is available regarding the absorption of fructose in the chicken intestine. We therefore investigated fructose absorption and its transporters in the chicken small intestine. The gene expression of three transporters (glucose transporter protein member 2 and 5 and sodium-dependent glucose transporter protein 1) in the jejunum of fasted chicks were lower than those in chicks fed ad libitum. The everted intestinal sacs (in vitro method for investigating intestinal absorption) showed that the concentration of fructose uptake rapidly increased within 15 min after incubation, and then gradually increased until 60 min. After 15 min of incubation, fructose uptake in the ad libitum chick intestine was approximately 2-fold that in the fasted intestine and was less than half of the glucose uptake in the ad libitum chick intestine. Our results suggest that fructose is absorbed in the small intestine of chicks and that uptake is decreased by fasting treatment with decreases in the mRNA expression of related transporters.

A critical courier role of volatile oils from Dalbergia odorifera for cardiac protection in vivo by QiShenYiQi

Component-based Chinese medicine (CCM) is derived from traditional Chinese medicine but produced with modern pharmaceutical standard and clearer clinical indications. However, it still faces challenges of defining individual component contribution in the complex formula. Using QiShenYiQi (QSYQ) as a model CCM, we investigated the role of Dalbergia odorifera (DO), an herbal component, in preventing myocardial damage. We showed that in vitro, QSYQ exerted considerable protective activities on cardiomyocytes from H₂O₂-induced mitochondrial dysfunction with or without DO. However, in isolated rat hearts, myocardial protection by QSYQ was significantly weakened without DO. In everted gut sac model, DO significantly enhanced absorption of the major QSYQ ingredients in different regions of rat intestine. Finally, in in vivo mouse model of doxorubicin (DOX)-induced myocardial damage, only QSYQ, but not QiShenYiQi without DO (QSYQ-DO), exerted a full protection. Taken together, our results showed that instead of directly contributing to the myocardial protection, Dalbergia odorifera facilitates the major active ingredients absorption and increases their efficacy, eventually enhancing the in vivo potency of QSYQ. These findings may shed new lights on our understanding of the prescription compatibility theory, as well as the impacts of “courier herbs” in component-based Chinese medicine.

The Next Generation Non-competitive Active Polyester Nanosystems for Transferrin Receptor-mediated Peroral Transport Utilizing Gambogic Acid as a Ligand

The current methods for targeted drug delivery utilize ligands that must out-compete endogenous ligands in order to bind to the active site facilitating the transport. To address this limitation, we present a non-competitive active transport strategy to overcome intestinal barriers in the form of tunable nanosystems (NS) for transferrin receptor (TfR) utilizing gambogic acid (GA), a xanthanoid, as its ligand. The NS made using GA conjugated poly(lactide-co-glycolide) (PLGA) have shown non-competitive affinity to TfR evaluated in cell/cell-free systems. The fluorescent PLGA-GA NS exhibited significant intestinal transport and altered distribution profile compared to PLGA NS in vivo. The PLGA-GA NS loaded with cyclosporine A (CsA), a model peptide, upon peroral dosing to rodents led to maximum plasma concentration of CsA at 6 h as opposed to 24 h with PLGA-NS with at least 2-fold higher levels in brain at 72 h. The proposed approach offers new prospects for peroral drug delivery and beyond.

Safety concerns over the use of intestinal permeation enhancers: A mini-review

Intestinal permeation enhancers (PEs) are key components in ∼12 oral peptide formulations in clinical trials for a range of molecules, primarily insulin and glucagon-like-peptide 1 (GLP-1) analogs. The main PEs comprise medium chain fatty acid-based systems (sodium caprate, sodium caprylate, and N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC)), bile salts, acyl carnitines, and EDTA. Their mechanism of action is complex with subtle differences between the different molecules. With the exception of SNAC and EDTA, most PEs fluidize the plasma membrane causing plasma membrane perturbation, as well as enzymatic and intracellular mediator changes that lead to alteration of intestinal epithelial tight junction protein expression. The question arises as to whether PEs can cause irreversible epithelial damage and tight junction openings sufficient to permit co-absorption of payloads with bystander pathogens, lipopolysaccharides and its fragment, or exo- and endotoxins that may be associated with sepsis, inflammation and autoimmune conditions. Most PEs seem to cause membrane perturbation to varying extents that is rapidly reversible, and overall evidence of pathogen co-absorption is generally lacking. It is unknown however, whether the intestinal epithelial damage-repair cycle is sustained during repeat-dosing regimens for chronic therapy.

A novel immune-tolerable and permeable lectin-like protein from mushroom Agaricus bisporus

A lectin like protein designated as LSMT is recently discovered in Agaricus bisporus. The protein adopts very similar structure to Ricin-B like lectin from Clitocybe nebularis (CNL) and HA-33 from Clostridium botulinum (HA-33), which both recognize sugar molecules that decorate the surface of the epithelial cells of the intestine. A preliminary study in silico pointed out potential capability of LSMT to perform such biological activity. Following that hypothesis, we demonstrated that LSMT is indeed capable of penetrating out from a dialysis tube of the mice intestine origin. Furthermore, the protein appeared not to evoke the immune response upon introduction into mice, unlike its structural homologs. This is the first report on the biological implication of LSMT that might lead to its application.

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.

Proteomic changes of the porcine small intestine in response to chronic heat stress

Acute heat stress (HS) negatively affects intestinal integrity and barrier function. In contrast, chronic mild HS poses a distinct challenge to animals. Therefore, this study integrates biochemical, histological and proteomic approaches to investigate the effects of chronic HS on the intestine in finishing pigs. Castrated male crossbreeds (79.00 ± 1.50 kg BW) were subjected to either thermal neutral (TN, 21 °C; 55% ± 5% humidity; n=8) or HS conditions (30 °C; 55% ± 5% humidity; n=8) for 3 weeks. The pigs were sacrificed after 3 weeks of high environmental exposure and the plasma hormones, the intestinal morphology, integrity, and protein profiles of the jejunum mucosa were determined. Chronic HS reduced the free triiodothyronine (FT3) and GH levels. HS damaged intestinal morphology, increased plasma d-lactate concentrations and decreased alkaline phosphatase activity of intestinal mucosa. Proteome analysis of the jejunum mucosa was conducted by 2D gel electrophoresis and mass spectrometry. Fifty-three intestinal proteins were found to be differentially abundant, 18 of which were related to cell structure and motility, and their changes in abundance could comprise intestinal integrity and function. The down-regulation of proteins involved in tricarboxylic acid cycle (TCA cycle), electron transport chain (ETC), and oxidative phosphorylation suggested that chronic HS impaired energy metabolism and thus induced oxidative stress. Moreover, the changes of ten proteins in abundance related to stress response and defense indicated pigs mediated long-term heat exposure and counteracted its negative effects of heat exposure. These findings have important implications for understanding the effect of chronic HS on intestines.

Styrene maleic acid micelles as a nanocarrier system for oral anticancer drug delivery - dual uptake through enterocytes and M-cells

Drug delivery systems could potentially overcome low bioavailability and gastrointestinal toxicity, which are the major challenges for the development of oral anticancer drugs. Herein, we demonstrate the ability of styrene maleic acid (SMA) nanomicelles encapsulating epirubicin to traverse in vitro and ex vivo models of the intestinal epithelium without affecting the tissue integrity. Further, SMA micelles encapsulating a fluorescent dye dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI) showed twofold higher accumulation in the liver and spleen, 15-fold higher accumulation in the tumor, and sixfold higher accumulation in the lung as compared with the free DiI, following oral administration in a mice xenograft breast cancer model. Additionally, SMA micelles showed colocalization with microfold (M)-cells and accumulation in Peyer’s patches, which together confirms the M-cell mediated uptake and transport of SMA micelles. Our results indicate that SMA micelles, showing dual uptake by enterocytes and M-cells, are a potential tool for safe oral anticancer drug delivery.

Intestinal absorption and biological effects of orally administered amorphous silica particles

Although amorphous silica nanoparticles are widely used in the production of food products (e.g., as anticaking agents), there is little information available about their absorption and biological effects after oral exposure. Here, we examined the in vitro intestinal absorption and in vivo biological effects in mice of orally administered amorphous silica particles with diameters of 70, 300, and 1,000 nm (nSP70, mSP300, and mSP1000, respectively) and of nSP70 that had been surface-modified with carboxyl or amine groups (nSP70-C and nSP70-N, respectively). Analysis of intestinal absorption by means of the everted gut sac method combined with an inductively coupled plasma optical emission spectrometer showed that the intestinal absorption of nSP70-C was significantly greater than that of nSP70. The absorption of nSP70-N tended to be greater than that of nSP70; however, the results were not statistically significant. Our results indicate that silica nanoparticles can be absorbed through the intestine and that particle diameter and surface properties are major determinants of the degree of absorption. We also examined the biological effects of the silica particles after 28-day oral exposure in mice. Hematological, histopathological, and biochemical analyses showed no significant differences between control mice and mice treated with the silica particles, suggesting that the silica nanoparticles evaluated in this study are safe for use in food production.

Cytokine and radical inhibition in septic intestinal barrier failure

BACKGROUND

Breakdown of the intestinal barrier is a driving force of sepsis and multiple organ failure. Radical scavengers or cytokine inhibitors may have a therapeutic impact on intestinal failure. Therapeutic effects on different sites of small intestine and colon have not been compared. Therefore, we investigated time-dependent intestinal permeability changes and their therapeutic inhibition in colon and small intestine with an ex vivo model.

METHODS

Male Sprague-Dawley rats were either pretreated for 24 h with lipopolysaccharide (LPS) intraperitoneally alone or in combination with a radical scavenger (pyruvate or Tempol) or a cytokine inhibitor (parecoxib or vasoactive intestinal peptide). The gastrointestinal permeability was measured by time-dependent fluorescein isothiocyanate inulin diffusion using washed and everted tube-like gut segments. Blood and tissue samples were taken to investigate the development of inflammatory cytokine level (interleukin 6) in the context of cytokine inhibition and reactive oxygen species level via nicotinamide adenine dinucleotide phosphate oxidase activity in radical scavenger groups.

RESULTS

After LPS treatment, mucosal permeability was enhanced up to 170% in small intestine and colon. In the small intestine the most significant reduction in permeability was found for pyruvate and parecoxib. Treatment with vasoactive intestinal peptide and parecoxib resulted in the most pronounced reduction of permeability in the colon.

CONCLUSIONS

Our data suggest that cytokine inhibitors and radical scavengers have pronounced effects in LPS-induced disrupted intestinal barrier of the colon and small intestine. Our novel model comparing different anatomic sites and different points in time after the onset of sepsis may contribute to gain new insight into mechanisms and treatment options of sepsis-related gut mucosal breakdown.

Safety evaluation of naringenin upon experimental exposure on rat gastrointestinal epithelium for novel optimal drug delivery

OBJECTIVE

To assess the effect of naringenin on the intestinal biochemical composition, function and histology for gastrointestinal toxicity since it has not yet been adequately exploited for safety through standard assays.

METHODS

Here, we describe naringenin (1 mM, 10 mM and 100 mM, respectively) or sodium deoxycholate (10 mM) effects on isolated brush border membrane from intestinal segments with single pass intestinal perfusion using lactate dehydrogenase, alkaline phosphatase and protein assays. MTT assay was used for cytotoxicity studies. Everted gut sac studies were used for evaluating the transport of nutrients across the intestinal segments. Lucifer yellow was used for paracellular permeability, followed by histological changes and surface characteristic studies of intestinal sacs.

RESULTS

The results indicated no significant alterations with naringenin, although significant (p < 0.01) changes were noticed with sodium deoxycholate in the activity of the rat intestinal brush border associated enzymes such as LDH, followed by intact cell viability with marked decrease in the villi height of the intestinal segments.

CONCLUSIONS

These observations indicate that naringenin was harmless upon exposure to rat gastrointestinal epithelium, clearly demonstrating the potential use of naturally occurring bioflavonoid as safe and novel pharmaceutical adjuvant in oral dosage forms as P-gp inhibitor.

Even an old technique is suitable in the molecular world of science: the everted sac preparation turns 60 years old

An old proverb states "necessity is the mother of invention." This certainly holds true in science as one pursues research questions. Experimental techniques have evolved as scientists have asked more specific research questions. Indeed, techniques such as the Ussing chamber, the perfused renal tubule preparation, patch-clamp, polymerase chain reaction, and site-directed mutagenesis have been developed over the past 60 years. However, sometimes, simple techniques may be useful and still very informative, and this certainly applies to intestinal physiology. Indeed, Gerald Wiseman and Thomas Hastings Wilson described the intestinal everted sac preparation some 60 years ago. Since then, this technique has been used for numerous research purposes including determining ion, amino acid, water and solute transport across the intestinal epithelium; and drug metabolism, absorption, and interactions in pharmaceutical/pharmacological research and even in education. This article provides a historical review of the development of the in vitro intestinal preparation that led to the everted sac preparation and its use in science.

Investigating permeability related hurdles in oral delivery of 11-keto-β-boswellic acid

11-Keto-β-boswellic acid (KBA) is an important and potent boswellic acids responsible for anti-inflammatory action of Boswellia extract. However, its pharmaceutical development has been severely limited by its poor oral bioavailability. The present work aims to investigate the permeability related hurdles in oral delivery of KBA. Gastrointestinal stability, gastrointestinal metabolism, adsorption-desorption kinetics and Caco-2 permeability studies have been carried out. KBA was found poorly permeable with Papp value of 2.85 ± 0.14 × 10(-6)cm/s. Higher absorptive transport indicated role of carrier mediated transport. Moreover, KBA transport across monolayer showed saturation kinetics at higher concentrations. KBA exposed to 1α,25-(OH)2 vitamin D3 treated cell monolayer showed the lowest Papp value of 2.01×10(-6) ± 0.02 × 10(-6)cm/s indicating role of CYP3A4 mediated metabolism during KBA transport. Metabolic stability experiments in jejunum S9 fractions further confirmed this. KBA was found unstable in simulated gastrointestinal fluids and also got accumulated in the enterocytes. Sorption and desorption kinetic studies using Caco-2 cells further confirmed accumulation of KBA inside the enterocytes. KBA also showed pH dependent permeability with higher flux at gradient pH condition of pH 6.5 at apical and 7.4 at basolateral. Taken as whole, the major permeability related hurdles that hampered oral bioavailability of KBA included its gastrointestinal instability, CYP3A4 mediated intestinal metabolism, accumulation within the enterocytes and saturable kinetics. The present investigation may help in designing novel drug delivery system for KBA.

Enhancement of absorption and hepatoprotective potential through soya-phosphatidylcholine-andrographolide vesicular system

Andrographis paniculata is a medicinal herb used extensively for various ailments and contains therapeutically active phytoconstituent, andrographolide (AN). Although hepatoprotective activity of AN is established, but their bioavailability is restricted due to its rapid clearance. The aim of this study, therefore, was to formulate AN herbosomes (ANH) through complexation with naturally occurring soya-phosphatidylcholine (SPC), in order to enhance absorption. Prepared andrographolide-soy phosphatidylcholine (AN-SPC) complex prepared was subjected for characterisation of complex and formation of vesicular system known as ANH using rotary evaporation techniques. This complex was subjected to in vitro study using everted small intestine sac technique which showed significantly increased absorption of AN from the ANH as compared to the plain AN. The hepatoprotective potential of ANH and plain AN was evaluated using carbon tetrachloride inducing hepatotoxicity rat model and compared, in which ANH equivalent to 50 mg/kg of plain AN significantly restore serum glutamate oxalacetate transaminase (112.4 ± 9.67 for AN whereas 90.2 ± 4.23 for ANH) and serum glutamate pyruvate transaminase (109.3 ± 7.89 for AN whereas 90.6 ± 4.34 for ANH) level as compared to control group. The ANH showed significantly better absorption than plain AN and this effect of ANH was also comparable to the standard drug (Silymarin). The findings of present study reveal that ANH has better bioavailability as shown by in vitro absorption study and hence improved hepatoprotection as compared to plain AN at equivalent dose.

Ex vivo systems to study host-microbiota interactions in the gastrointestinal tract

It is increasingly apparent that the microbial ecosystems in the mammalian gastrointestinal tract play an intricate role in health and disease. There is a growing interest in the development of targeted strategies for modulating health through the modification of these microbiota. Ecologists are faced with the challenge of understanding the structure and function of ecosystems, the component parts of which interact with each other in complex and diffuse ways. The human gut microbiota, with its high species richness and diversity (up to 1000 bacterial species per individual) including members of all three domains of life, situated in the dynamic environment of the gastrointestinal tract, is probably among the most complex ecosystems on this planet. In order to elucidate the mechanistic foundations, and physiological significance, of beneficial or pathogenic relationships between the gut microbiota and their hosts, researchers require tractable model ecosystems that allow to recapitulate and investigate host-microbe and microbe-microbe interactions. This review discusses ex vivo gastrointestinal models systems that can be used to gain mechanistic insights into the emergent properties of the host-microbial superorganism.

Formulation and in vitro absorption analysis of Rhizoma paridis steroidal saponins

Rhizoma paridis steroidal saponins (RPS) have been prepared and identified as the active compounds for antitumor activity in our previous study. However, the low oral bioavailability of the steroidal saponins restricted its using. In the present research, solid dispersion (SD) and phytosome (PHY) formulation of RPS were prepared, and the physicochemical parameters as well as the intestinal absorption in rat everted gut sac model were investigated. Seven agents were selected as the carriers of SD, and poloxamer 407 (P 407) was the most suitable one. SD reduced the particle size of saponins in the water solution, enhanced the solubility of the saponins by about 3.5 folds, and significantly improved the absorption transport of saponins from 48 to 104 μg in everted gut sac of the rat system. PHY significantly enhanced the hydrophilic of saponins but showed little effect on the absorption in small intestine. Jejunum and ileum part absorbed more absolute contents of total saponins than duodenum parts. Six saponins, the main contents of RPS, used as the index of comparing the three forms, were also further investigated in the physico-chemical properties and the absorption tests. n-Octanol/water partition coefficients of the six saponins ordered in RPS, SD and PHY were Chonglouoside H>Dioscin>Polyphyllin D>Gracillin>Paris-VII>Formosanin C. All the saponins possessed the higher absorptive characteristics in SD formulation. The absorption rate of diosgenyl saponins in intestine was more than the pennogenyl saponins.