Effect of Hydrogen Peroxide on Interleukin-8 Synthesis and Death of Caco-2 Cells

Roles of airway and intestinal epithelia in responding to pathogens and maintaining tissue homeostasis

Epithelial cells form a resilient barrier and orchestrate defensive and reparative mechanisms to maintain tissue stability. This review focuses on gut and airway epithelia, which are positioned where the body interfaces with the outside world. We review the many signaling pathways and mechanisms by which epithelial cells at the interface respond to invading pathogens to mount an innate immune response and initiate adaptive immunity and communicate with other cells, including resident microbiota, to heal damaged tissue and maintain homeostasis. We compare and contrast how airway and gut epithelial cells detect pathogens, release antimicrobial effectors, collaborate with macrophages, Tregs and epithelial stem cells to mount an immune response and orchestrate tissue repair. We also describe advanced research models for studying epithelial communication and behaviors during inflammation, tissue injury and disease.

circGLI3 Inhibits Oxidative Stress by Regulating the miR-339-5p/VEGFA Axis in IPEC-J2 Cells

As a new type of noncoding RNA, circular RNA (circRNA) is stable in cells and not easily degraded. This type of RNA can also competitively bind miRNAs to regulate the expression of their target genes. The role of circRNA in the mechanism of intestinal oxidative stress (OS) in weaned piglets is still unclear. In our research, diquat (DQ) was used to induce OS in small intestinal epithelial cells (IPEC-J2) to construct an OS cell model. Mechanistically, dual luciferase reporter assays, fluorescence in situ hybridization (FISH), and western blotting were performed to confirm that circGLI3 directly sponged miR-339-5p and regulated the expression of VEGFA. Overexpression of circGLI3 promoted IPEC-J2 cell proliferation, increased the proportion of S-phase cells (P < 0.01), and reduced reactive oxygen species (ROS) generation when IPEC-J2 cells were subjected to OS. circGLI3 can increase the activity of glutathione peroxidase (GSH-Px) and the total antioxidant capacity (T-AOC) in IPEC-J2 cells and reduce the malondialdehyde (MDA) content and levels of inflammatory factors. Therefore, overexpression of circGLI3 reduced oxidative damage, whereas miR-339-5p mimic counteracted these effects. We identified a regulatory network composed of circGLI3, miR-339-5p, and VEGFA and verified that circGLI3 regulates VEGFA by directly binding miR-339-5p. The expression of VEGFA affects IPEC-J2 cell proliferation, cell cycle progression, and ROS content and changes the levels of antioxidant enzymes and inflammatory factors. This study reveals the molecular mechanism by which circGLI3 inhibits OS in the intestine of piglets and provides a theoretical basis for further research on the effect of OS on intestinal function.

Soluble silver ions from silver nanoparticles induce a polarised secretion of interleukin-8 in differentiated Caco-2 cells

Because of their antimicrobial properties, silver nanoparticles are increasingly incorporated in food-related and hygiene products, which thereby could lead to their ingestion. Although their cytotoxicity mediated by oxidative stress has been largely studied, their effects on inflammation remain controversial. Moreover, the involvement of silver ions (originating from Ag0 oxidation) in their mode of action is still unclear. In this context, the present study aims at assessing the impact of silver nanoparticles on the secretion of the pro-inflammatory chemokine interleukin-8 by Caco-2 cells forming an in vitro model of the intestinal mucosal barrier. Silver nanoparticles induced a vectorized secretion of interleukin-8 towards the apical compartment, which is found in the medium 21 h after the incubation. This secretion seems mediated by Nrf2 signalling pathway that orchestrates cellular defense against oxidative stress. The soluble silver fraction of silver nanoparticles suspensions led to a similar amount of secreted interleukin-8 than silver nanoparticles, suggesting an involvement of silver ions in this interleukin-8 secretion.

Lactobacillus plantarum 2142 prevents intestinal oxidative stress in optimized in vitro systems

Recently, there has been a growing interest to replace antibiotics' administration with the application of probiotics. The aim of our investigations was to reveal the influence of spent culture supernatant of Lactobacillus plantarum 2142 on the response of enterocytes to oxidative stress, and the spent culture supernatant's ability to protect them from oxidative injury. The experiments were performed on non-carcinogenic porcine epithelial cell line, IPEC-J2 isolated from a neonatal piglet and on human colon adenocarcinoma cell line, Caco-2. The cells cultured on membrane inserts were treated with millimolar hydrogen peroxide solution to provoke oxidative stress. The peroxide-triggered cell response profile was evaluated via determination of change in transepithelial electrical resistance, quantification of extent of cell death by 4',6-diamidino-2 phenylindole (DAPI) staining and via estimation of proinflammatory cytokine, IL-8 production using ELISA technique. Non-starter lactobacilli supernatant-mediated inhibition of peroxide-triggered upregulation of IL-8 production confirmed the antiinflammatory properties of active metabolites produced by Lactobacillus plantarum 2142 in acute oxidative stress.

Sensing of barrier tissue disruption with an organic electrochemical transistor

The gastrointestinal tract is an example of barrier tissue that provides a physical barrier against entry of pathogens and toxins, while allowing the passage of necessary ions and molecules. A breach in this barrier can be caused by a reduction in the extracellular calcium concentration. This reduction in calcium concentration causes a conformational change in proteins involved in the sealing of the barrier, leading to an increase of the paracellular flux. To mimic this effect the calcium chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra acetic acid (EGTA) was used on a monolayer of cells known to be representative of the gastrointestinal tract. Different methods to detect the disruption of the barrier tissue already exist, such as immunofluorescence and permeability assays. However, these methods are time-consuming and costly and not suited to dynamic or high-throughput measurements. Electronic methods for measuring barrier tissue integrity also exist for measurement of the transepithelial resistance (TER), however these are often costly and complex. The development of rapid, cheap, and sensitive methods is urgently needed as the integrity of barrier tissue is a key parameter in drug discovery and pathogen/toxin diagnostics. The organic electrochemical transistor (OECT) integrated with barrier tissue forming cells has been shown as a new device capable of dynamically monitoring barrier tissue integrity. The device is able to measure minute variations in ionic flux with unprecedented temporal resolution and sensitivity, in real time, as an indicator of barrier tissue integrity. This new method is based on a simple device that can be compatible with high throughput screening applications and fabricated at low cost.

Validation of the organic electrochemical transistor for in vitro toxicology

BACKGROUND

The gastrointestinal epithelium provides a physical and biochemical barrier to the passage of ions and small molecules; however this barrier may be breached by pathogens and toxins. The effect of individual pathogens/toxins on the intestinal epithelium has been well characterized: they disrupt barrier tissue in a variety of ways, such as by targeting tight junction proteins, or other elements of the junctions between adjacent cells. A variety of methods have been used to characterize disruption in barrier tissue, such as immunofluorescence, permeability assays and electrical measurements of epithelia resistance, but these methods remain time consuming, costly and ill-suited to diagnostics or high throughput toxicology.

METHODS

The advent of organic electronics has created a unique opportunity to interface the worlds of electronics and biology, using devices such as the organic electrochemical transistor (OECT), whose low cost materials and potential for easy fabrication in high throughput formats represent a novel solution for assessing epithelial tissue integrity.

RESULTS

In this study, OECTs were integrated with gastro-intestinal cell monolayers to study the integrity of the gastrointestinal epithelium, providing a very sensitive way to detect minute changes in ion flow across the cell layer due to inherent amplification by the transistor.

MAJOR CONCLUSIONS

We validate the OECT against traditional methods by monitoring the effect of toxic compounds on epithelial tissue. We show a systematic characterization of this novel method, alongside existing methods used to assess barrier tissue function.

GENERAL SIGNIFICANCE

The toxic compounds induce a dramatic disruption of barrier tissue, and the OECT measures this disruption with increased temporal resolution and greater or equal sensitivity when compared with existing methods. This article is part of a Special Issue entitled Organic Bioelectronics - Novel Applications in Biomedicine.

Measurement of barrier tissue integrity with an organic electrochemical transistor

The integration of an organic electrochemical transistor with human barrier tissue cells provides a novel method for assessing toxicology of compounds in vitro. Minute variations in paracellular ionic flux induced by toxic compounds are measured in real time, with unprecedented temporal resolution and extreme sensitivity.

Acute oxidative stress affects IL-8 and TNF-α expression in IPEC-J2 porcine epithelial cells

Reactive oxygen species are implicated in cell and tissue damage in a number of diseases including acute and chronic inflammation of the gut. Effects of H(2)O(2) exposure on non-carcinogenic porcine epithelial cell line, IPEC-J2 cells cultured on collagen-coated membrane inserts were monitored based on transepithelial electrical resistance (TER) change, extent of necrotic cell damage, gene expression of inflammatory cytokines IL-8 and TNF-α. Furthermore, the junction proteins claudin-1 and E-cadherin were also investigated by immunohistochemistry. Peroxide (1mM) increased IL-8 and TNF-α gene expression levels significantly allowing 1 h recovery time without affecting the cellular distribution of junction proteins, TER and cell survival rate. In conclusion, the IPEC-J2 cell line on membrane insert was introduced as a fast and reliable investigation tool for oxidative stimuli-triggered intestinal inflammation and in the future as a screening method for antioxidant and probiotic candidates.

Oxidative stress enhances IL-8 and inhibits CCL20 production from intestinal epithelial cells in response to bacterial flagellin

Intestinal epithelial cells act as innate immune sentinels, as the first cells that encounter diarrheal pathogens. They use pattern recognition molecules such as the Toll-like receptors (TLRs) to identify molecular signals found on microbes but not host cells or food components. TLRs cannot generally distinguish the molecular signals on pathogenic bacteria from those found in commensals, yet under healthy conditions epithelial immune responses are kept in check. We hypothesized that, in the setting of tissue damage or stress, intestinal epithelial cells would upregulate their responses to TLR ligands to reflect the greater need for immediate protection against pathogens. We treated Caco-2 cells with the TLR5 agonist flagellin in the presence or absence of H(2)O(2) and measured chemokine production and intracellular signaling pathways. H(2)O(2) increased flagellin-induced IL-8 (CXCL8) production in a dose-dependent manner. This was associated with synergistic phosphorylation of p38 MAP kinase and with prolonged I-kappaB degradation and NF-kappaB activation. The H(2)O(2)-mediated potentiation of IL-8 production required the activity of p38, tyrosine kinases, phospholipase Cgamma, and intracellular calcium, but not protein kinase C or protein kinase D. H(2)O(2) prolonged and augmented NF-kappaB activation by flagellin. In contrast to IL-8, CCL20 (MIP3alpha) production by flagellin was reduced by H(2)O(2), and this effect was not calcium dependent. Oxidative stress biases intestinal epithelial responses to flagellin, leading to increased production of IL-8 and decreased production of CCL20. This suggests that epithelial cells are capable of sensing the extracellular environment and adjusting their antimicrobial responses accordingly.

Molecular signatures of N-nitroso compounds in Caco-2 cells: implications for colon carcinogenesis

N-nitroso compounds (NOC) are genotoxic, carcinogenic to animals, and may play a role in human cancer development. Because the gastro-intestinal tract is an important route of exposure through endogenous nitrosation, we hypothesize that NOC exposure targets genetic processes relevant in colon carcinogenesis. To investigate these genomic responses, we analyzed the transcriptomic effects of genotoxic concentrations of two nitrosamides, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 1 microM) and N-methyl-N-nitrosurea (MNU, 1 mM), and four nitrosamines, N-nitrosodiethylamine (NDEA, 50mM), N-nitrosodimethylamine (NDMA, 100 mM), N-nitrosopiperidine (NPIP, 40 mM), and N-nitrosopyrrolidine (NPYR, 100mM), in the human colon carcinoma cell line Caco-2. Gene Ontology gene group, consensus motif gene group and biological pathway analysis revealed that nitrosamides had little effect on gene expression after 24 h of exposure, whereas nitrosamines had a strong impact on the transcriptomic profile. Analyses showed modifications of cell cycle regulation and apoptosis pathways for nitrosamines which was supported by flow cytometric analysis. We found additional modifications in gene groups and pathways of oxidative stress and inflammation, which suggest an increase in oxidative stress and proinflammatory immune response upon nitrosamine exposure, although less distinct for NDMA. Furthermore, NDEA, NPIP, and NPYR most strongly affected several developmental motif gene groups and pathways, which may influence developmental processes. Many of these pathways and gene groups are implicated in the carcinogenic process and their modulation by nitrosamine exposure may therefore influence the development of colon cancer. In summary, our study has identified pathway modifications in human colon cells which may be associated with cancer risk of nitrosamine exposure in the human colon.

Free radicals and antioxidants in inflammatory processes and ischemia-reperfusion injury

This article discusses the current understanding of the role of free radicals and antioxidants in inflammatory processes and in ischemia reperfusion injury. It begins by describing the manifestations of acute inflammation and outlining the cellular events that occur during inflammation. It then describes the biochemical mediators of inflammation with special attention to nitric oxide. It details the process of hypoxia reperfusion injury, the enzymes involved, its treatment, and studies involving specific hypoxia reperfusion injuries in various animal species.