Transport of Surface Engineered Polyamidoamine (PAMAM) Dendrimers Across IPEC-J2 Cell Monolayers

Allicin Improves Intestinal Epithelial Barrier Function and Prevents LPS-Induced Barrier Damages of Intestinal Epithelial Cell Monolayers

Gut barrier disruption is the initial pathogenesis of various diseases. We previously reported that dietary allicin improves tight junction proteins in the endoplasmic reticulum stressed jejunum. However, whether the allicin benefits the gut barrier within mycotoxin or endotoxin exposure is unknown. In the present study, IPEC-J2 cell monolayers within or without deoxynivalenol (DON) or lipopolysaccharide (LPS) challenges were employed to investigate the effects of allicin on intestinal barrier function and explore the potential mechanisms. Results clarified that allicin at 2 μg/mL increased the viability, whereas the allicin higher than 10 μg/mL lowered the viability of IPEC-J2 cells via inhibiting cell proliferation. Besides, allicin increased trans-epithelial electric resistance (TEER), decreased paracellular permeability, and enhanced ZO-1 integrity of the IPEC-J2 cell monolayers. Finally, allicin supplementation prevented the LPS-induced barrier damages via activating Nrf2/HO-1 pathway-dependent antioxidant system. In conclusion, the present study strongly confirmed allicin as an effective nutrient to improve intestinal barrier function and prevent bacterial endotoxin-induced barrier damages.

Mitigative effects of Eleutheroside E against the mechanical barrier dysfunction induced by soybean agglutinin in IPEC-J2 cell line

Soybean agglutinin (SBA) is an anti-nutritional factor which decreases the mechanical barrier function in intestinal porcine jejunum epithelial cells (IPEC-J2). Eleutheroside E (EE) is a key part of Acanthopanax senticosus to exert pharmacological effects. This study aims to investigate the effects of EE on the barrier function in IPEC-J2 cells and to determine the ability of EE to enhance the protective effect of barrier function against SBA exposure. The IPEC-J2 cells were cultured in mediums with concentration of 0.1 mg/ml EE, 0.5 ml/ml SBA and 0.1 mg/ml EE pre-treated then treated with 0.5 mg/ml SBA. Then, the transepithelial electric resistance (TEER) value, inflammatory cytokines mRNA expression, tight junction mRNA and protein expression were tested by epithelial Voltohm meter, q-PCR and Western blot method respectively. The results showed that cells treated with 0.1 mg/ml EE had lower permeability (p < 0.05) while 0.5 mg/ml SBA treatment had higher permeability through tested TEER, and higher tight junction proteins (Claudin-3 and ZO-1) expressions and genes (Claudin-3, Occludin and ZO-1) expressions (p < 0.05) in 0.1 mg/ml EE group. IPEC-J2 cells pre-treated with 0.1 mg/ml EE could significantly improve the inflammatory response caused by 0.5 mg/ml SBA by up-regulation for IL-10, TGF-β, and down-regulation gene expression of IL-6, TNF-α and IFN-γ (p < 0.05). In conclusion, 0.1 mg/ml EE can improve the mechanical barrier function and could protect the effects while 0.5 mg/ml of SBA-induced barrier dysfunction in IPEC-J2.

Betaine attenuates LPS-induced downregulation of Occludin and Claudin-1 and restores intestinal barrier function

BACKGROUND

The intestinal epithelial barrier, which works as the first line of defense between the luminal environment and the host, once destroyed, it will cause serious inflammation or other intestinal diseases. Tight junctions (TJs) play a vital role to maintain the integrity of the epithelial barrier. Lipopolysaccharide (LPS), one of the most important inflammatory factors will downregulate specific TJ proteins including Occludin and Claudin-1 and impair integrity of the epithelial barrier. Betaine has excellent anti-inflammatory activity but whether betaine has any effect on TJ proteins, particularly on LPS-induced dysfunction of epithelial barriers remains unknown. The purpose of this study is to explore the pharmacological effect of betaine on improving intestinal barrier function represented by TJ proteins. Intestinal porcine epithelial cells (IPEC-J2) were used as an in vitro model.

RESULTS

The results demonstrated that betaine enhanced the expression of TJ proteins while LPS (1 μg/mL) downregulates the expression of these proteins. Furthermore, betaine attenuates LPS-induced decreases of TJ proteins both shown by Western blot (WB) and Reverse transcription-polymerase chain reaction (RT-PCR). The immunofluorescent images consistently revealed that LPS induced the disruption of TJ protein Claudin-1 and reduced its expression while betaine could reverse these alterations. Similar protective role of betaine on intestinal barrier function was observed by transepithelial electrical resistance (TEER) approach.

CONCLUSION

In conclusion, our research demonstrated that betaine attenuated LPS-induced downregulation of Occludin and Claudin-1 and restored the intestinal barrier function.

Vitamin A inhibits the action of LPS on the intestinal epithelial barrier function and tight junction proteins

Inflammation caused by either intrinsic or extrinsic toxins results in intestinal barrier dysfunction, contributing to inflammatory bowel disease (IBD) and other diseases. Vitamin A is a widely used food supplement although its mechanistic effect on intestinal structures is largely unknown. The goal of this study was to explore the mechanism by investigating the influence of vitamin A on the intestinal barrier function, represented by tight junctions. IPEC-J2 cells were differentiated on transwell inserts and used as a model of intestinal barrier permeability. Transepithelial electrical resistance (TEER) was used as an indicator of monolayer integrity and paracellular permeability. Western blot and the reverse transcriptase-polymerase chain reaction were used to assess the protein and mRNA expression of tight junction proteins. Immunofluorescence microscopy was used to evaluate the localization and expression of tight junctions. Differentiated cells were treated with a vehicle control (Ctrl), inflammatory stimulus (1 μg mL-1 LPS), LPS co-treatment with 0.1 μmol L-1 Vitamin A (1 μg mL-1 LPS + 0.1 μmol L-1 VA) and 0.1 μmol L-1 Vitamin A. LPS significantly decreased TEER by 24 hours, continuing this effect to 48 hours after application. Vitamin A alleviated the LPS-induced decrease of TEER from 12 hours to 48 hours, while Vitamin A alone enhanced TEER, indicating that Vitamin A attenuated LPS-induced intestinal epithelium permeability. Mechanistically, different concentrations of Vitamin A (0-20 μmol L-1) enhanced tight junction protein markers including Zo-1, Occludin and Claudin-1 both at protein and mRNA levels with an optimized dose of 0.1 μmol L-1. Immunofluorescence results demonstrated that majority of Zo-1 and Claudin-1 is located at the tight junctions, as we expected. LPS reduced the expression of these proteins and Vitamin A reversed LPS-reduced expression of these proteins, consistent with the results of western blot. In conclusion, Vitamin A improves the intestinal barrier function and reverses LPS-induced intestinal barrier damage via enhancing the expression of tight junction proteins.

Eleutheroside B increase tight junction proteins and anti-inflammatory cytokines expression in intestinal porcine jejunum epithelial cells (IPEC-J2)

Eleutheroside B (EB) is a phenylpropanoid glycoside with anti-inflammatory properties, neuroprotective abilities, immunomodulatory effects, antinociceptive effects, and regulation of blood glucose. The aim of this study was to investigate the effects of EB on the barrier function in the intestinal porcine epithelial cells J2 (IPEC-J2). The IPEC-J2 cells were inoculated into 96-well plates at a density of 5 × 10³ cells per well for 100% confluence. The cells were cultured in the presence of EB at concentrations of 0, 0.05, 0.10, and 0.20 mg/ml for 48 hr. Then, 0.10 mg/ml was selected as the suitable concentration for the estimation of transepithelial electric resistance (TEER) value, alkaline phosphatase activity, proinflammatory cytokines mRNA expression, tight junction mRNA and protein expression. The results of this study indicated that the supplementation of EB in IPEC-J2 cells decreased cellular membrane permeability and mRNA expression of proinflammatory cytokines, including interleukin-6 (IL-6), interferon-γ (INF-γ), and tumour necrosis factor-α (TNF-α). The supplementation of EB in IPEC-J2 cells increased tight junction protein expression and anti-inflammatory cytokines, interleukin 10 (IL-10) and transforming growth factor beta (TGF-β). In addition, the western blotting and real-time quantitative polymerase chain reaction (RT-qPCR) results indicated that EB significantly (p < 0.05) increased the mRNA and protein expression of intestinal tight junction proteins, Claudin-3, Occludin, and Zonula Occludins protein-1 (ZO-1). Therefore, dietary supplementation of EB may increase intestinal barrier function, tight junction protein expression, anti-inflammatory cytokines, and decrease proinflammatory cytokines synthesis in IPEC-J2 cells.

In vivo pharmacokinetics, biodistribution and the anti-tumor effect of cyclic RGD-modified doxorubicin-loaded polymers in tumor-bearing mice

In our previous study, we successfully produced and characterized a multifunctional drug delivery system with doxorubicin (RC/GO/DOX), which was based on graphene oxide (GO) and cyclic RGD-modified chitosan (RC). Its characteristics include: pH-responsiveness, active targeting of hepatocarcinoma cells, and efficient loading with controlled drug release. Here, we report the pharmacokinetics, biodistribution, and anti-tumor efficacy of RC/GO/DOX polymers in tumor-bearing nude mice. The objective of this study is to assess its targeting potential for tumors. Pharmacokinetic and biodistribution profiles demonstrated that tumor accumulation of RC/GO/DOX polymers was almost three times higher than the others, highlighting the efficacy of the active targeting strategy. Furthermore, the tumor inhibition rate of RC/GO/DOX polymers was 56.64%, 2.09 and 2.93 times higher than that of CS/GO/DOX polymers (without modification) and the DOX solution, respectively. Anti-tumor efficacy results indicated that the tumor growth was better controlled by RC/GO/DOX polymers than the others. Hematoxylin and eosin (H&E) staining showed remarkable changes in tumor histology. Compared with the saline group, the tumor section from the RC/GO/DOX group revealed a marked increase in the quantity of apoptotic and necrotic cells, and a reduction in the quantity of the blood vessels. Together, these studies show that this new system could be regarded as a suitable form of DOX-based treatment of the hepatocellular carcinoma.

Poly(amido amine) dendrimers in oral delivery

Poly(amidoamine) (PAMAM) dendrimers have been extensively investigated for oral delivery applications due to their ability to translocate across the gastrointestinal epithelium. In this Review, we highlight recent advances in the evaluation of PAMAM dendrimers as oral drug delivery carriers. Specifically, toxicity, mechanisms of transepithelial transport, models of the intestinal epithelial barrier including isolated human intestinal tissue model, detection of dendrimers, and surface modification are discussed. We also highlight evaluation of various PAMAM dendrimer-drug conjugates for their ability to transport across gastrointestinal epithelium for improved oral bioavailability. In addition, current challenges and future trends for clinical translation of PAMAM dendrimers as carriers for oral delivery are discussed.

EGF-coated nano-dendriplexes for tumor-targeted nucleic acid delivery in vivo

The clinical success of therapeutic DNA is still hindered due to the lack of effective delivery carriers. Here, we designed a tumor-targeted gene nano delivery system based on EGFR targeting strategy. Epidermal growth factor (EGF) was introduced to nano-complexes of PAMAM dendrimer and DNA via electrostatic interactions to form self-assembled PAMAM/DNA/EGF nano-complexes. The properties of self-assembled complexes were characterized by gel retardation assay and particle size and zeta potential analysis. Meanwhile, the toxicity of EGF-dendriplexes was evaluated by the MTT assay, which indicated that the complexes exhibited decreased cytotoxicity with the incorporation of EGF. We labeled polyamidoamine (PAMAM) dendrimers with FITC or a near-infrared (NIR) dye Lss670 and tested the cellular uptake in vitro and biodistribution in xenograft mouse tumor models. As compared to dendriplexes, the ternary EGF-dendriplexes showed a significantly higher cellular uptake into HepG2 cells due to the specific binding between EGF and EGF receptor (EGFR) over expressed on HepG2 cells, which resulted in the enhanced gene transfection efficiency. The biodistribution of EGF-dendriplexes in vivo was monitored with in vivo imaging technique, which indicated that EGF-dendriplexes enhanced EGFR-positive tumor-targeted biodistribution. These findings indicate that this novel nano-vector realized efficiently tumor-targeting gene delivery and high efficient gene expression in vivo, and it may possess a potential targeting gene delivery system in cancer therapy.

Dendrimer nanocarriers for transport modulation across models of the pulmonary epithelium

The purpose of this study was to determine the effect of PEGylation on the interaction of poly(amidoamine) (PAMAM) dendrimer nanocarriers (DNCs) with in vitro and in vivo models of the pulmonary epithelium. Generation-3 PAMAM dendrimers with varying surface densities of PEG 1000 Da were synthesized and characterized. The results revealed that the apical to basolateral transport of DNCs across polarized Calu-3 monolayers increases with an increase in PEG surface density. DNC having the greatest number of PEG groups (n = 25) on their surface traversed at a rate 10-fold greater than its non-PEGylated counterpart, in spite of their larger size. This behavior was attributed to a significant reduction in charge density upon PEGylation. We also observed that PEGylation can be used to modulate cellular internalization. The total uptake of PEG-free DNC into polarized Calu-3 monolayers was 12% (w/w) vs 2% (w/w) for that with 25 PEGs. Polarization is also shown to be of great relevance in studying this in vitro model of the lung epithelium. The rate of absorption of DNCs administered to mice lungs increased dramatically when conjugated with 25 PEG groups, thus supporting the in vitro results. The exposure obtained for the DNC with 25PEG was determined to be very high, with peak plasma concentrations reaching 5 μg·mL^–1 within 3 h. The combined in vitro and in vivo results shown here demonstrate that PEGylation can be potentially used to modulate the internalization and transport of DNCs across the pulmonary epithelium. Modified dendrimers thereby may serve as a valuable platform that can be tailored to target the lung tissue for treating local diseases, or the circulation, using the lung as pathway to the bloodstream, for systemic delivery.

Nanoparticle toxicity by the gastrointestinal route: evidence and knowledge gaps

The increasing interest in nanoparticles for advanced technologies, consumer products, and biomedical applications has led to great excitement about potential benefits but also concern over the potential for adverse human health effects. The gastrointestinal tract represents a likely route of entry for many nanomaterials, both directly through intentional ingestion or indirectly via nanoparticle dissolution from food containers or by secondary ingestion of inhaled particles. Additionally, increased utilisation of nanoparticles may lead to increased environmental contamination and unintentional ingestion via water, food animals, or fish. The gastrointestinal tract is a site of complex, symbiotic interactions between host cells and the resident microbiome. Accordingly, evaluation of nanoparticles must take into consideration not only absorption and extraintestinal organ accumulation but also the potential for altered gut microbes and the effects of this perturbation on the host. The existing literature was evaluated for evidence of toxicity based on these considerations. Focus was placed on three categories of nanomaterials: nanometals and metal oxides, carbon-based nanoparticles, and polymer/dendrimers with emphasis on those particles of greatest relevance to gastrointestinal exposures.

Effects of zinc on epithelial barrier properties and viability in a human and a porcine intestinal cell culture model

Zinc is an essential trace element with a variety of physiological and biochemical functions. Piglets are commonly supplemented, during the weaning period, with doses of zinc above dietary requirements with positive effects on health and performance that might be attributed to anti-secretory and barrier-enhancing effects in the intestine. For a better understanding of these observations increasing zinc sulfate (ZnSO4; 0-200μM) concentrations were used in an in vitro culture model of porcine (IPEC-J2) and human (Caco-2) intestinal epithelial cells and effects on barrier function, viability, and the mRNA expression of one selected heat shock protein (Hsp) were assessed. When treated apically with zinc sulfate, the transepithelial electrical resistance (TEER) did not change significantly. In contrast, cell viability measured by lactate dehydrogenase (LDH) leakage, by ATP and by WST-1 conversion in postconfluent IPEC-J2 monolayers was affected after a 24-h treatment with 200μM ZnSO4. Caco-2 cells were more resistant to Zn. ZnSO4 did not induce any effect on viability, except when it was used at the highest concentration (200μM), and only in preconfluent cells. Furthermore, ZnSO4 induced Hsp70 mRNA expression at 200μM and was more pronounced in preconfluent cells. The observed dose-related effects of zinc are cell-line specific and depended on the differentiation status of the cells. The IPEC-J2 cell line appears to be a suitable in vitro model to characterize specific effects on porcine intestinal cells.

Arginine and citrulline protect intestinal cell monolayer tight junctions from hypoxia-induced injury in piglets

BACKGROUND

Arginine (Arg) is deficient in the serum of the preterm neonate and is lower in those developing intestinal ischemia. We investigated whether Arg or its precursor, citrulline (Cit), protects intestinal tight junctions (TJs) from hypoxia (HX) and determined whether inducible nitric oxide (NO) plays a role.

METHODS

Neonatal piglet jejunal IPEC-J2 cell monolayers were treated with Arg or Cit, reversible and irreversible NO synthetase (NOS) inhibitors, and were exposed to HX. TJs were assessed by serial measurements of transepithelial electrical resistance (TEER), flux of inulin-fluorescein isothiocyanate, and immunofluorescent staining of TJ proteins.

RESULTS

We found that Arg and Cit were protective against HX-related damage. At the final time point (14 h), the mean TEER ratio (TEER as compared with baseline) for Arg + HX and Cit + HX was significantly higher than that for HX alone. Both Arg and Cit were associated with decreased inulin flux across hypoxic monolayers and qualitatively preserved TJ proteins. Irreversible inhibition of NOS blocked this protective effect. Lipid peroxidation assay showed that our model did not produce oxidant injury.

CONCLUSION

Arg and Cit, via a mechanism dependent on NO donation, protected intestinal epithelial integrity.

Dendrimer pharmacokinetics: the effect of size, structure and surface characteristics on ADME properties

Dendrimers show increasing promise as drug-delivery vectors and can be generated with a wide range of scaffold structures, sizes and surface functionalities. To this point, the majority of studies of dendrimer-based drug-delivery systems have detailed pharmacodynamic outcomes, or have followed the pharmacokinetics of a solubilized or conjugated drug. By contrast, detailed commentary on the in vivo fate of the dendrimer carrier is less evident, even though the pharmacokinetics of the carrier will likely dictate both pharmacodynamic and toxicokinetic outcomes. In the current article, the influence of size, structure and surface functionality on the absorption, distribution, metabolism and elimination (ADME) properties of dendrimers have been examined and the implications of these findings for delivery system design are discussed.

Transepithelial transport and toxicity of PAMAM dendrimers: implications for oral drug delivery

This article summarizes efforts to evaluate poly(amido amine) (PAMAM) dendrimers as carriers for oral drug delivery. Specifically, the effect of PAMAM generation, surface charge and surface modification on toxicity, cellular uptake and transepithelial transport is discussed. Studies on Caco-2 monolayers, as models of intestinal epithelial barrier, show that by engineering surface chemistry of PAMAM dendrimers, it is possible to minimize toxicity while maximizing transepithelial transport. It has been demonstrated that PAMAM dendrimers are transported by a combination of paracellular and transcellular routes. Depending on surface chemistry, PAMAM dendrimers can open the tight junctions of epithelial barriers. This tight junction opening is in part mediated by internalization of the dendrimers. Transcellular transport of PAMAM dendrimers is mediated by a variety of endocytic mechanisms. Attachment or complexation of cytotoxic agents to PAMAM dendrimers enhances the transport of such drugs across epithelial barriers. A remaining challenge is the design and development of linker chemistries that are stable in the gastrointestinal tract (GIT) and the blood stream, but amenable to cleavage at the target site of action. Recent efforts have focused on the use of PAMAM dendrimers as penetration enhancers. Detailed in vivo oral bioavailability of PAMAM dendrimer-drug conjugates, as a function of physicochemical properties will further need to be assessed.