Lignosulfonic acid attenuates NF-κB activation and intestinal epithelial barrier dysfunction induced by TNF-α/IFN-γ in Caco-2 cells

The in vitro intestinal cell model: different co-cultured cells create different applications

As a vitro absorption model, the Caco-2 cells originate from a human colon adenocarcinomas and can differentiate into a cell layer with enterocyte-like features. The Caco-2 cell model is popularly applied to explore drug transport mechanisms, to evaluate the permeability of drug and to predict the absorption of drugs or bioactive substances in the gut. However, there are limitations to the application of Caco-2 cell model due to lack of a mucus layer, the long culture period and the inability to accurately simulate the intestinal environment. The most frequent way to expand the Caco-2 cell model and address its limitations is by co-culturing it with other cells or substances. This article reviews the culture methods and applications of 3D and 2D co-culture cell models established around Caco-2 cells. It also concludes with a summary of model strengths and weaknesses.

Targeting staphylococcal enterotoxin B binding to CD28 as a new strategy for dampening superantigen-mediated intestinal epithelial barrier dysfunctions

Staphylococcus aureus is a gram-positive bacterium that may cause intestinal inflammation by secreting enterotoxins, which commonly cause food-poisoning and gastrointestinal injuries. Staphylococcal enterotoxin B (SEB) acts as a superantigen (SAg) by binding in a bivalent manner the T-cell receptor (TCR) and the costimulatory receptor CD28, thus stimulating T cells to produce large amounts of inflammatory cytokines, which may affect intestinal epithelial barrier integrity and functions. However, the role of T cell-mediated SEB inflammatory activity remains unknown. Here we show that inflammatory cytokines produced by T cells following SEB stimulation induce dysfunctions in Caco-2 intestinal epithelial cells by promoting actin cytoskeleton remodelling and epithelial cell-cell junction down-regulation. We also found that SEB-activated inflammatory T cells promote the up-regulation of epithelial-mesenchymal transition transcription factors (EMT-TFs) in a nuclear factor-κB (NF-κB)- and STAT3-dependent manner. Finally, by using a structure-based design approach, we identified a SEB mimetic peptide (pSEB116-132) that, by blocking the binding of SEB to CD28, dampens inflammatory-mediated dysregulation of intestinal epithelial barrier.

Fermentation enhances the amelioration effect of bee pollen on Caco-2 monolayer epithelial barrier dysfunction based on NF-κB-mediated MLCK-MLC signaling pathway

Intestinal barrier integrity is essential for normal nutrient digestion and absorption and disease resistance. This study aims to investigate how fermentation affects the ameliorative effect of bee pollen on the intestinal barrier dysfunction stimulated by interferon-γ and tumor necrosis factor (IFN-γ/TNF-α) cytokines. The results indicated that fermentation enhances the alleviating effect of bee pollen on intestinal barrier dysfunction (including elevated trans epithelial electrical resistance and decreased paracellular permeability). In addition, fermented bee pollen (FBP) significantly decreased (p < 0.05) the secretion levels of interleukin (IL)-6, IL-8, and IL-1β and expression of cyclooxygenase (COX)-2 protein in intestinal barrier cells. Furthermore, fermentation improved the ability of bee pollen to up-regulate the expression of tight junction proteins including zonula occludens (ZO)-1, occluding, and claudin-1. Notably, FBP showed stronger ability to inhibit the expression of nuclear factor kappa-B (NF-κB) mediated myosin light chain kinase (MLCK) and myosin light chain (MLC) signaling pathway associated with phosphorylated proteins. Overall, our results indicated that fermentation enhances the protective effect of bee pollen on the intestinal barrier, and FBP has promising potential to be used as a novel functional food to protect the intestinal barrier.

Shikimic Acid Regulates the NF-κB/MAPK Signaling Pathway and Gut Microbiota to Ameliorate DSS-Induced Ulcerative Colitis

Shikimic acid (SA) is a compound extracted from the plant anise and has anti-inflammatory effects. However, any impact on intestinal inflammation or mechanisms involved has not been investigated. The present study used a dextran sulfate sodium (DSS)-induced mouse colitis model to investigate the effects of SA on intestinal inflammation. Intragastric administration of SA slowed DSS-induced weight loss, reduced disease activity index (DAI) score, enhanced the intestinal barrier, reduced the destruction of the colonic structure, inhibited the phosphorylation of key proteins in MAPK and NF-κB signaling pathways, inhibited the expression of inflammatory factors TNF-α, IL-1β, and MPO (P < 0.05), decreased IFN-γ expression (P < 0.05), and increased immunoglobulin IgG content (P < 0.05). After 50 mg/kg SA treatment, the content of Bacteroidetes increased and Proteobacteria decreased in the cecal feces of mice with colitis (P < 0.05) and the richness of gut species increased. In conclusion, SA could improve intestinal inflammation and enhance intestinal immunity, indicating its suitability as a therapeutic candidate.

Lignosulfonate Rapidly Inactivates Human Immunodeficiency and Herpes Simplex Viruses

Background: Very few studies of the antiviral potential of lignosulfonates have been published. With the aim of oral application, among various groups of natural products, the relative antiviral potency of lignosulfonate and its ability to rapidly inactivate viruses were investigated. Methods: As target cells, MT-4 cells in suspension and attached Vero cells were used for infections with human immunodeficiency virus (HIV) and human herpes simplex type-1 virus (HSV). Mock- or virus-infected cells were incubated for 3–5 days with various concentrations of test samples, and the viable cell number was determined with the MTT method. For the shorter exposure experiments, higher titers of HIV or HSV were exposed to test samples for 10 or 3 min, diluted to a normal multiplicity of infection (MOI), and applied to the cells. Antiviral activity was quantified by using the chemotherapy index. Results: In the long-exposure system, lignosulfonates showed comparable anti-HIV activity with those of AZT, ddC, and sulfated polysaccharides, and it exceeded those of hundreds of tannins and flavonoids. When the exposure time was shortened, the chemotherapeutic index of the lignosulfonates for HIV was increased 27-fold. At a physiological pH, lignosulfonate showed higher anti-HIV activity than commercial alkali-lignin, dealkali-lignin, and humic acid, possibly due to the higher solubility and purity. Conclusions: With their rapid virus-inactivation capabilities, lignosulfonates may be useful for the prevention or treatment of virally induced oral diseases.

Integrated analysis of circRNAs and mRNAs expression profile revealed the involvement of hsa_circ_0007919 in the pathogenesis of ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) is characterized by chronic inflammation in the colon and epigenetic factors underlying the occurrence. Circular RNAs (circRNAs) have been under intensive focus due to the circular construct and gene-regulating functions. However, the changes and roles of circRNAs in UC remain unknown.

METHODS

Microarrays were used to detect the differentially expressed genes, and quantitative real-time PCR was used to identify the changes in UC. In silico analyses were performed to predict the functions of circRNAs and mRNAs. In vitro, epithelial cell lines were stimulated by pro-inflammation effectors to test the alterations in circRNAs. CircRNAs-microRNAs-mRNAs network clarified the potential mechanisms underlying circRNAs in UC. The binding site between hsa_circ_0007919 and miR-138 or let-7a was verified using dual-luciferase assay.

RESULTS

A total of 264 significantly dysregulated circRNAs and 1869 differentially expressed mRNAs in inflamed mucosa were compared with the non-inflamed mucosa in UC. Hsa_circ_0004662 and hsa_circ_0007919 were altered largely in UC tissues. Hsa_circ_0007919 was reduced persistently after inflammatory treatments, and it was relevant to Mayo endoscopic subscores and the expression of tight junction molecules. Finally, hsa_circ_0007919 could harbor miR-138, and let-7a to regulate the targeted mRNAs EPC1 and VIPR1.

CONCLUSIONS

Several circRNAs were differentially expressed in UC. Hsa_circ_0007919 is related to clinical characteristics and epithelial integrity by binding to hsa-let-7a, hsa-miR-138 to regulate the target genes. CircRNAs, especially hsa_circ_0007919, are associated with the pathogenesis and development of UC, with potential diagnostic and therapeutic implications.

Lignins isolated from Prickly pear cladodes of the species Opuntia fícus-indica (Linnaeus) Miller and Opuntia cochenillifera (Linnaeus) Miller induces mice splenocytes activation, proliferation and cytokines production

Opuntia fícus-indica and Opuntia cochenillifera are species of Cactaceae, found in the arid regions of the planet. They present water, cellulose, hemicellulose, pectins, extractives, ashes and lignins. Here we aimed to study the immunomodulatory action of lignins from these two species against mice splenocytes, since no study for this purpose has yet been reported. The antioxidant activities of these lignins were evaluated by the DPPH, ABTS, NO assays and total antioxidant activity. Cytotoxicity was evaluated through Annexin V-FITC and propidium iodide-PE probs and cell proliferation was determined by CFSE. Immunomodulation studies with Opuntia lignins obtained were performed through investigation of ROS levels, cytosolic calcium release, changes on mitochondrial membrane potential, cytokine production and NO release. Results showed that Opuntia cochenillifera lignin presented more phenolic amount and antioxidant activities than Opuntia ficius-indica. Both lignins showed high cell viability (>96%) and cell proliferation. Activation signal was observed for both lignins with increase of ROS and cytosolic calcium levels, and changes in mitochondrial membrane potential. In addition, lignins induced high TNF-α, IL-6 and IL-10 production and reduced NO release. Therefore, these lignins present great potential to be used as molecules with a proinflammatory profile, being shown as a promising therapeutic agent.

Systems pharmacology approach reveals the antiinflammatory effects of Ampelopsis grossedentata on dextran sodium sulfate-induced colitis

AIM

To investigate the protective effects of Ampelopsis grossedentata (AMP) on dextran sulfate sodium (DSS)-induced colitis in mice based on systems pharmacology approach.

METHODS

Systems pharmacology approach was used to predict the active ingredients, candidate targets and the efficacy of AMP on ulcerative colitis (UC) using a holistic process of active compound screening, target fishing, network construction and analysis. A DSS-induced colitis model in C57BL/6 mice (n = 10/group) was constructed and treated with 5-aminosalicylic acid (100 mg/kg/d) and AMP (400 mg/kg/d) to confirm the underlying mechanisms and effects of AMP on UC with western blot analyses, polymerase chain reaction, histological staining and immunohistochemistry.

RESULTS

The therapeutic effects of AMP against DSS-induced colitis were determined in the beginning, and the results showed that AMP significantly improved the disease in general observations and histopathology analysis. Subsequent systems pharmacology predicted 89 corresponding targets for the four candidate compounds of AMP, as well as 123 candidate targets of UC, and protein-protein interaction networks were constructed for the interaction of putative targets of AMP against UC. Enrichment analyses on TNF-α and RANKL/RANK, a receptor activator of NF-κB signaling pathways, were then carried out. Experimental validation revealed that inflammation-related signaling pathways were activated in the DSS group, and AMP significantly suppressed DSS-induced high expression of IRAK1, TRAF6, IκB and NF-κB, and inhibited the elevated expression levels of TNF-α, IL-1β, IL-6 and IL-8.

CONCLUSION

AMP could exert protective effects on UC via suppressing the IRAK1/TRAF6/NF-κB-mediated inflammatory signaling pathways.