NF-κB In Intestinal Epithelial Cells Research Articles

Fusobacterium nucleatum promotes inflammatory and anti-apoptotic responses in colorectal cancer cells via ADP-heptose release and ALPK1/TIFA axis activation

ABSTRACT The anaerobic bacterium Fusobacterium nucleatum is significantly associated with human colorectal cancer (CRC) and is considered a significant contributor to the disease. The mechanisms underlying the promotion of intestinal tumor formation by F. nucleatum have only been partially uncovered. Here, we showed that F. nucleatum releases a metabolite into the microenvironment that strongly activates NF-κB in intestinal epithelial cells via the ALPK1/TIFA/TRAF6 pathway. Furthermore, we showed that the released molecule had the biological characteristics of ADP-heptose. We observed that F. nucleatum induction of this pathway increased the expression of the inflammatory cytokine IL-8 and two anti-apoptotic genes known to be implicated in CRC, BIRC3 and TNFAIP3. Finally, it promoted the survival of CRC cells and reduced 5-fluorouracil chemosensitivity in vitro. Taken together, our results emphasize the importance of the ALPK1/TIFA pathway in Fusobacterium induced-CRC pathogenesis, and identify the role of ADP-H in this process.

Akkermansia muciniphila upregulates genes involved in maintaining the intestinal barrier function via ADP-heptose-dependent activation of the ALPK1/TIFA pathway

ABSTRACT The commensal bacteria that make up the gut microbiota impact the health of their host on multiple levels. In particular, the interactions taking place between the microbe-associated molecule patterns (MAMPs) and pattern recognition receptors (PRRs), expressed by intestinal epithelial cells (IECs), are crucial for maintaining intestinal homeostasis. While numerous studies showed that TLRs and NLRs are involved in the control of gut homeostasis by commensal bacteria, the role of additional innate immune receptors remains unclear. Here, we seek for novel MAMP-PRR interactions involved in the beneficial effect of the commensal bacterium Akkermansia muciniphila on intestinal homeostasis. We show that A. muciniphila strongly activates NF-κB in IECs by releasing one or more potent activating metabolites into the microenvironment. By using drugs, chemical and gene-editing tools, we found that the released metabolite(s) enter(s) epithelial cells and activate(s) NF-κB via an ALPK1, TIFA and TRAF6-dependent pathway. Furthermore, we show that the released molecule has the biological characteristics of the ALPK1 ligand ADP-heptose. Finally, we show that A. muciniphila induces the expression of the MUC2, BIRC3 and TNFAIP3 genes involved in the maintenance of the intestinal barrier function and that this process is dependent on TIFA. Altogether, our data strongly suggest that the commensal A. muciniphila promotes intestinal homeostasis by activating the ALPK1/TIFA/TRAF6 axis, an innate immune pathway exclusively described so far in the context of Gram-negative bacterial infections.

Phytoglycoprotein isolated from Dioscorea batatas Decne promotes intestinal epithelial wound healing.

Dioscorea batatas Decne (DBD) has been used to heal various illnesses of the kidney and intestine as an herbal medicine in Asia. As a source of therapeutic agents, many glycoproteins have been isolated from mushrooms and plants, but the functional role of glycoprotein in intestinal epithelial wound healing has not been understood yet. In the present study, we investigated the wound healing potentials of the 30 kDa glycoprotein (DBD glycoprotein) isolated from DBD in human intestinal epithelial (INT-407) cells. We found that DBD glycoprotein (100 μg·mL-1) significantly increased the motility of INT-407 cells for 24 h by activating protein kinase C (PKC). DBD glycoprotein stimulated the activation of p38 mitogen-activated protein kinase (MAPK), which is responsible for the phosphorylation of NF-κB inhibitor α (IκBα). DBD glycoprotein increased the level of profilin-1 (PFN1), α-actinin and F-actin expression via activation of transcription factor, nuclear factor-kappa B (NF-κB) during its promotion of cell migration. Experimental mouse colitis was induced by adding dextran sulfate sodium (DSS) to the drinking water at a concentration of 4% (W/V) for 7 days. We figured out that administration of DBD glycoprotein (10 and 20 mg·kg-1) lowers the levels of disease activity index and histological inflammation in DSS-treated ICR mice. In this regard, we suggest that DBD glycoprotein has ability to promote the F-actin-related migration signaling events via activation of PKC and NF-κB in intestinal epithelial cells and prevent inflammatory bowel disease.

Deficiency in IκBα in the intestinal epithelium leads to spontaneous inflammation and mediates apoptosis in the gut.

The IκB kinase (IKK)-NF-κB signaling pathway plays a multifaceted role in inflammatory bowel disease (IBD): on the one hand, it protects from apoptosis; on the other, it activates transcription of numerous inflammatory cytokines and chemokines. Although several murine models of IBD rely on disruption of IKK-NF-κB signaling, these involve either knockouts of a single family member of NF-κB or of upstream kinases that are known to have additional, NF-κB-independent, functions. This has made the distinct contribution of NF-κB to homeostasis in intestinal epithelium cells difficult to assess. To examine the role of constitutive NF-κB activation in intestinal epithelial cells, we generated a mouse model with a tissue-specific knockout of the direct inhibitor of NF-κB, Nfkbia/IκBα. We demonstrate that constitutive activation of NF-κB in intestinal epithelial cells induces several hallmarks of IBD including increased apoptosis, mucosal inflammation in both the small intestine and the colon, crypt hyperplasia, and depletion of Paneth cells, concomitant with aberrant Wnt signaling. To determine which NF-κB-driven phenotypes are cell-intrinsic, and which are extrinsic and thus require the immune compartment, we established a long-term organoid culture. Constitutive NF-κB promoted stem-cell proliferation, mis-localization of Paneth cells, and sensitization of intestinal epithelial cells to apoptosis in a cell-intrinsic manner. Increased number of stem cells was accompanied by a net increase in Wnt activity in organoids. Because aberrant Wnt signaling is associated with increased risk of cancer in IBD patients and because NFKBIA has recently emerged as a risk locus for IBD, our findings have critical implications for the clinic. In a context of constitutive NF-κB, our findings imply that general anti-inflammatory or immunosuppressive therapies should be supplemented with direct targeting of NF-κB within the epithelial compartment in order to attenuate apoptosis, inflammation, and hyperproliferation. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Attenuation of NF-κB in Intestinal Epithelial Cells Is Sufficient to Mitigate the Bone Loss Comorbidity of Experimental Mouse Colitis.

Skeletal abnormalities are common comorbidities of inflammatory bowel disease (IBD). Patients suffering from IBD, including ulcerative colitis and Crohn's disease, present with skeletal complications. However, the mechanism underpinning IBD-associated bone loss remains vague. Intestinal inflammation generates an inflammatory milieu at the intestinal epithelium that leads to dysregulation of mucosal immunity through gut-residing innate lymphoid cells (ILCs) and other cell types. ILCs are recently identified mucosal cells considered as the gatekeeper of gut immunity and their function is regulated by intestinal epithelial cell (IEC)-secreted cytokines in response to the inflammatory microenvironment. We first demonstrate that serum as well as IECs collected from the intestine of dextran sulfate sodium (DSS)-induced colitis mice contain high levels of inflammatory and osteoclastogenic cytokines. Mechanistically, heightened inflammatory response of IECs was associated with significant intrinsic activation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) in IECs and increased frequency of ILC1, ILC3, and myeloid osteoclast progenitors. Validating the central role of IEC-specific NF-κB activation in this phenomenon, conditional expression of constitutively active inhibitor kappa B kinase 2 (IKK2) in IECs in mice recapitulates the majority of the cellular, inflammatory, and osteolytic phenotypes observed in the chemically induced colitis. Furthermore, conditional deletion of IKK2 from IECs significantly attenuated inflammation and bone loss in DSS-induced colitis. Finally, using the DSS-induced colitis model, pharmacologic inhibition of IKK2 was effective in reducing frequency of ILC1 and ILC3 cells, attenuated circulating levels of inflammatory cytokines, and halted colitis-associated bone loss. Our findings identify IKK2 in IECs as viable therapeutic target for colitis-associated osteopenia.

Bacteroides fragilis Enterotoxin Upregulates Heme Oxygenase-1 in Intestinal Epithelial Cells via a Mitogen-Activated Protein Kinase- and NF-κB-Dependent Pathway, Leading to Modulation of Apoptosis.

The Bacteroides fragilis enterotoxin (BFT), a virulence factor of enterotoxigenic B. fragilis (ETBF), interacts with intestinal epithelial cells and can provoke signals that induce mucosal inflammation. Although expression of heme oxygenase-1 (HO-1) is associated with regulation of inflammatory responses, little is known about HO-1 induction in ETBF infection. This study was conducted to investigate the effect of BFT on HO-1 expression in intestinal epithelial cells. Stimulation of intestinal epithelial cells with BFT resulted in upregulated expression of HO-1. BFT activated transcription factors such as NF-κB, AP-1, and Nrf2 in intestinal epithelial cells. Upregulation of HO-1 in intestinal epithelial cells was dependent on activated IκB kinase (IKK)-NF-κB signals. However, suppression of Nrf2 or AP-1 signals in intestinal epithelial cells did not result in significant attenuation of BFT-induced HO-1 expression. HO-1 induction via IKK-NF-κB in intestinal epithelial cells was regulated by p38 mitogen-activated protein kinases (MAPKs). Furthermore, suppression of HO-1 activity led to increased apoptosis in BFT-stimulated epithelial cells. These results suggest that a signaling pathway involving p38 MAPK-IKK-NF-κB in intestinal epithelial cells is required for HO-1 induction during exposure to BFT. Following this induction, increased HO-1 expression may regulate the apoptotic process in responses to BFT stimulation.

Nimbolide Inhibits Nuclear Factor-КB Pathway in Intestinal Epithelial Cells and Macrophages and Alleviates Experimental Colitis in Mice.

Nimbolide is a limonoid extracted from neem tree (Azadirachta indica) that has antiinflammatory properties. The effect of nimbolide on the nuclear factor-kappa B (NF-κB) pathway in intestinal epithelial cells (IECs), macrophages and in murine colitis models was investigated. The IEC COLO 205, the murine macrophage cell line RAW 264.7, and peritoneal macrophages from interleukin-10-deficient (IL-10-/- ) mice were preconditioned with nimbolide and then stimulated with tumor necrosis factor-α (TNF-α) or lipopolysaccharide. Dextran sulfate sodium-induced acute colitis model and chronic colitis model in IL-10-/- mice were used for in vivo experiments. Nimbolide significantly suppressed the expression of inflammatory cytokines (IL-6, IL-8, IL-12, and TNF-α) and inhibited the phosphorylation of IκBα and the DNA-binding affinity of NF-κB in IECs and macrophages. Nimbolide ameliorated weight loss, colon shortening, disease activity index score, and histologic scores in dextran sulfate sodium colitis. It also improved histopathologic scores in the chronic colitis of IL-10-/- mice. Staining for phosphorylated IκBα was significantly decreased in the colon tissue after treatment with nimbolide in both models. Nimbolide inhibits NF-κB signaling in IECs and macrophages and ameliorates experimental colitis in mice. These results suggest nimbolide could be a potentially new treatment for inflammatory bowel disease. Copyright © 2016 John Wiley & Sons, Ltd.

Par-complex aPKC and Par3 cross-talk with innate immunity NF-κB pathway in epithelial cells

Components of the Par-complex, atypical PKC and Par3, have been found to be downregulated upon activation of NF-κB in intestinal epithelial cells. To determine their possible role in pro-inflammatory responses we transduced Caco-2 human colon carcinoma cells with constitutively active (ca) PKCι or anti-Par3 shRNA-expressing lentiviral particles. Contrary to previous reports in other cell types, ca-PKCι did not activate, but rather decreased, baseline NF-κB activity in a luminiscence reporter assay. An identical observation applied to a PB1 domain deletion PKCι, which fails to localize to the tight-junction. Conversely, as expected, the same ca-PKCι activated NF-κB in non-polarized HEK293 cells. Likewise, knockdown of Par3 increased NF-κB activity and, surprisingly, greatly enhanced its response to TNFα, as shown by transcription of IL-8, GRO-1, GRO-2 and GRO-3. We conclude that aPKC and Par3 are inhibitors of the canonical NF-κB activation pathway, although perhaps acting through independent pathways, and may be involved in pro-inflammatory responses.

Par-complex aPKC and Par3 cross-talk with innate immunity NF-κB pathway in epithelial cells

SummaryComponents of the Par-complex, atypical PKC and Par3, have been found to be downregulated upon activation of NF-κB in intestinal epithelial cells. To determine their possible role in pro-inflammatory responses we transduced Caco-2 human colon carcinoma cells with constitutively active (ca) PKCι or anti-Par3 shRNA-expressing lentiviral particles. Contrary to previous reports in other cell types, ca-PKCι did not activate, but rather decreased, baseline NF-κB activity in a luminiscence reporter assay. An identical observation applied to a PB1 domain deletion PKCι, which fails to localize to the tight-junction. Conversely, as expected, the same ca-PKCι activated NF-κB in non-polarized HEK293 cells. Likewise, knockdown of Par3 increased NF-κB activity and, surprisingly, greatly enhanced its response to TNFα, as shown by transcription of IL-8, GRO-1, GRO-2 and GRO-3. We conclude that aPKC and Par3 are inhibitors of the canonical NF-κB activation pathway, although perhaps acting through independent pathways, and may be involved in pro-inflammatory responses.

Effect of different immunosuppressive agents on defensin expression of intestinal epithelial cells via nuclear factor-κB signaling pathways

Objective To investigate the effect of tacrolimus (FK506),cyclosporin A (CsA),rapamycin (Rapa) and Glucosida Tripterygii TOTA (GTT) on human β-defensin (hBD-1 and hBD-2) expression in intestinal epithelial cells (Caco-2 and HT-29 cells).Methods Quantitative real-time quantitative polymerase chain reaction (Real-time PCR) and Western blotting were used to detect the effects of the final concentration of 10 μmol/L of FK506,CsA,Rapa and GTT on hBD-1 and hBD-2 expression in human intestinal epithelial cells stimulated by interleukin (IL)-1 β (20 μg/L).Nuclear factor-κB (NF-κB)binding activity in the Caco-2 cells was examined by using electrophoretic mobility shift assay (EMSA) and an enzyme linked immunosorbent assay (ELISA)-based assay with immobilized oligonucleotide.Results As compared with the IL-1β alone,the addition of FK506,CsA or Rapa in the culture medium in Caco-2 cells significantly increased the mRNA level of hBD-2 by (20.58 ± 1.02)％,(139.49 ± 6.97)％ and (425.97 ± 21.29)％ respectively (P ＜0.05).Meanwhile,the mRNA level of hBD-2 was decreased by (48.59 ± 2.42)％ in Caco-2 cells cultured with GTT (P＜ 0.05).In HT-29 cells,the value was (62.52±3.25)％,(20.56±1.10)％,(46.79 ±2.28)％ and (82.73 ±7.88)％ respectively (P＜0.05).Western blotting analysis revealed that the same results.However,GTT attenuated the expression of hBD-2.As compared with the control group,either FK506,CsA and rapamycin promnoted the activation of NF-κB,but GTr decreased the activation of NF-κB (P ＜ 0.05),which was related to the phosphorylation of Ser276.Conclusion The results presented in this paper show that FK506,CsA and Rapa activate NF-κB in intestinal epithelial cells,resulting in efficient induction of hBD-2 production in vitro. Key words: Intestinal epithelial cells; Defensin; Immunosuppressant; Nuclear factor-κB

Bifidobacterium lactis inhibits NF-κB in intestinal epithelial cells and prevents acute colitis and colitis-associated colon cancer in mice

The aim of this study was to investigate the antiinflammatory effects of Bifidobacterium lactis on intestinal epithelial cells (IECs) and on experimental acute murine colitis and its tumor prevention effects on colitis-associated cancer (CAC) in mice. Human HT-29 cells were stimulated with IL-1beta, lipopolysaccharides, or tumor necrosis factor-alpha with and without B. lactis, and the effects of B. lactis on nuclear factor kappa B (NF-kappaB) signaling in IEC were examined. For in vivo study, dextran sulfate sodium (DSS)-treated mice were fed with and without B. lactis. Finally, we induced colonic tumors in mice by azoxymethane (AOM) and DSS and evaluated the effects of B. lactis on tumor growth. B. lactis significantly suppressed NF-kappaB activation, including NF-kappaB-binding activity and NF-kappaB-dependent reporter gene expression in a dose-dependent manner, and suppressed IkappaB-alpha degradation, which correlated with the downregulation of NF-kappaB-dependent gene products. Moreover, B. lactis suppressed the development of acute colitis in mice. Compared with the DSS group, the severity of DSS-induced colitis as assessed by disease activity index, colon length, and histological score was reduced in the B. lactis-treated group. In the CAC model, the mean number and size of tumors in the B. lactis-treated group were significantly lower than those in the AOM group. Our data demonstrate that B. lactis inhibits NF-kappaB and NF-kappaB-regulated genes in IEC and prevents acute colitis and CAC in mice. These results suggest that B. lactis could be a potential preventive agent for CAC as well as a therapeutic agent for inflammatory bowel disease.

Comment on “The Bacterial Fermentation Product Butyrate Influences Epithelial Signaling via Reactive Oxygen Species-Mediated Changes in Cullin-1 Neddylation”

We refer to the important article by Kumar et al. ([1][1]) This report links the inhibition of ubiquitin ligase and the suppression of NF-κB in intestinal epithelial cells to fatty acid (FA)/reactive oxygen species (ROS) production, but it is unclear whether this process is sufficient to cause

Epithelial Cell IκB-Kinase β Has an Important Protective Role inClostridium difficileToxin A-Induced Mucosal Injury

Toxin A released by Clostridium difficile interacts with the single layer of intestinal epithelial cells that lines the host's intestinal tract and leads to mucosal damage and inflammation that manifests clinically as antibiotic-associated diarrhea and pseudomembranous colitis. Activation of the transcription factor NF-kappaB in intestinal epithelial cells is important for regulating the expression of epithelial cell proinflammatory genes and cell survival. However, the role of NF-kappaB activation in the pathogenesis of C. difficile toxin A-induced colitis is unknown. To determine the functional importance in vivo of NF-kappaB activation in intestinal epithelium in the pathogenesis of C. difficile-induced colitis, we used mutant mice that do not activate the classical NF-kappaB signaling pathway in intestinal epithelial cells due to a conditional deficiency in those cells of the IkappaB-kinase beta (IKKbeta) subunit of IKK. C. difficile toxin A challenge of intestinal loops in intestinal epithelial cell IKKbeta-deficient mice induced a rapid and significant increase in intestinal epithelial apoptosis compared with littermate controls. This was accompanied by a significant increase in acute mucosal inflammation, mucosal injury, luminal fluid secretion, and bacterial translocation. We conclude that activation of intestinal epithelial cell NF-kappaB by toxin A plays an important host mucosal protective role after C. difficile toxin A exposure that is mediated, at least in part, through promoting epithelial cell survival by abrogating epithelial cell apoptosis.

A new twist on trefoils. Focus on “TFF3 modulates NF-κB and a novel regulatory molecule of NF-κB in intestinal epithelial cells via a mechanism distinct from TNF-α”

THE INTESTINAL EPITHELIUM, particularly in the colon, faces unique challenges in maintaining cell and tissue homeostasis. Unlike most other epithelia in the body, it is constantly barraged with a soup of microbes and their products. These have the potential to activate inflammation and immune responses. Indeed, the normal physiological state of the intestine appears to be one of controlled inflammation, with a variety of immune and inflammatory effector cells located in the lamina propria immediately adjacent to the epithelium, even in health. This may reflect a state of readiness, where sufficient numbers of phagocytes and other antimicrobial effectors are present to deal quickly with any possible microbial invasion before it becomes systemic. However, in susceptible individuals, the regulatory controls on this “physiological” inflammation break down, likely due to either immune defects and/or defects in the barrier properties of the epithelium itself, and chronic, pathological inflammation ensues (15). This chronic inflammation, which is driven by immune responses to the enteric flora, establishes a vicious cycle because tissue injury, particularly to the epithelium, further compromises the ability of the gut to exclude immunostimulatory molecules (3, 11, 12). There is now substantial evidence that this type of cycle is centrally involved in the pathogenesis of important digestive diseases such as ulcerative colitis and Crohn’s disease, which may also predispose sufferers to subsequent development of colon cancer (7). However, the mechanisms that normally allow individuals to restrain immune responses to the enteric flora, and thus limit inflammation, are still poorly understood. Inflammatory responses in the gut (as in other tissue sites) as well as progression to malignancy, are pivotally controlled by the transcription factor NF-B (8). This factor is normally held in an inactive state in the cell cytosol as a complex with its inhibitor, IB. In response to a variety of extracellular signals, including those delivered by microbial products or inflammatory cytokines, IB is phosphorylated, and thereby targeted for ubiquitination and subsequent degradation by the proteosome. This frees NF-B to translocate to the nucleus, where it binds to the promoter regions and evokes expression of a series of target genes that perpetuate the inflammatory response, including chemokines such as IL-8 that stimulate the influx of inflammatory cell types. In addition, NF-B can trigger the production of signals that limit epithelial apoptosis, and may be involved in the predisposition to malignancy that accompanies chronic intestinal inflammation (6). Thus NF-B can be considered a master regulator that can both initiate and

TFF3 modulates NF-κB and a novel negative regulatory molecule of NF-κB in intestinal epithelial cells via a mechanism distinct from TNF-α

Trefoil factor 3 (intestinal trefoil factor) is a cytoprotective factor in the gut. Herein we compared the effect of trefoil factor 3 with tumor necrosis factor-α on 1) activation of NF-κB in intestinal epithelial cells; 2) expression of Twist protein (a molecule essential for downregulation of nuclear factor-κB activity in vivo); and 3) production of interleukin-8. We showed that Twist protein is constitutively expressed in intestinal epithelial cells. Tumor necrosis factor-α induced persistent degradation of Twist protein in intestinal epithelial cells via a signaling pathway linked to proteasome, which was associated with prolonged activation of NF-κB. In contrast to tumor necrosis factor, trefoil factor 3 triggered transient activation of NF-κB and prolonged upregulation of Twist protein in intestinal epithelial cells via an ERK kinase-mediated pathway. Unlike tumor necrosis factor-α, transient activation of NF-κB by trefoil factor 3 is not associated with induction of IL-8 in cells. To examine the role of Twist protein in intestinal epithelial cells, we silenced the Twist expression by siRNA. Our data showed that trefoil factor 3 induced interleukin-8 production after silencing Twist in intestinal epithelial cells. Together, these observations indicated that 1) trefoil factor 3 triggers a diverse signal from tumor necrosis factor-α on the activation of NF-κB and its associated molecules in intestinal epithelial cells; and 2) trefoil factor 3-induced Twist protein plays an important role in the modulation of inflammatory cytokine production in intestinal epithelial cells.