Endotoxin, but not platelet‐activating factor, activates nuclear factor‐κB and increases IκBα and IκBβ turnover in enterocytes

Plaen, Isabelle G. De; Qu, Xiao Wu; Wang, Hao; Tan, Xiao Di; Wang, Liya; Han, Xin; Rozenfeld, Ranna A.; Hsueh, Wei

doi:10.1046/j.1365-2567.2002.01453.x

Cited by 27 publications

(27 citation statements)

References 36 publications

(83 reference statements)

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“…NF-jB was identified by EMSA using a kit from Promega (Madison, WI), as previously described 21 after gel loading of equivalent amounts of nuclear extracts. Supershift experiments for p50 and p65, the two subunits identified in our previous studies 5 were performed with anti-p50 (sc-114X) and anti-p65 (sc-109X) antibodies from Santa Cruz Biothechnology.…”

Section: Methodsmentioning

confidence: 99%

“…We previously found that both LPS and tumour necrosis factor-a (TNF-a) activate NF-jB in IEC-6 cells, a non-transformed small intestinal crypt cell line 5 and the effect of TNF is more rapid than that of LPS, already strong at 10 min following incubation. 5 In mice with colitis, treatment with antisense phosphorothioate oligonucleotides to the p65 subunit of NF-jB has been shown to reduce the severity of the inflammation.…”

Section: M M U N O L O G Y O R I G I N a L A R T I C L Ementioning

confidence: 99%

“…5 In mice with colitis, treatment with antisense phosphorothioate oligonucleotides to the p65 subunit of NF-jB has been shown to reduce the severity of the inflammation. 6 A major role of the epithelial cells in regulating the inflammatory response by NF-jB was further confirmed by experiments on transgenic mice with specific ablation of IKKb in their intestinal epithelial cells, preventing the activation of the canonical NF-jB pathway in the enterocytes.…”

Section: M M U N O L O G Y O R I G I N a L A R T I C L Ementioning

confidence: 99%

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Lipopolysaccharide induces CXCL2/macrophage inflammatory protein‐2 gene expression in enterocytes via NF‐κB activation: independence from endogenous TNF‐α and platelet‐activating factor

Plaen¹,

Han²,

Liu³

et al. 2006

Immunology

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SummaryCXCL2 (macrophage inflammatory protein-2 (MIP-2)), a critical chemokine for neutrophils, has been shown to be produced in the rat intestine in response to platelet-activating factor (PAF) and to mediate intestinal inflammation and injury. The intestinal epithelium, constantly exposed to bacterial products, is the first line of defence against micro-organisms. It has been reported that enterocytes produce proinflammatory mediators, including tumour necrosis factor (TNF) and PAF, and we showed that lipopolysaccharide (LPS) and TNF activate nuclear factor (NF)-jB in enterocytes. However, it remains elusive whether enterocytes release CXCL2 in response to LPS and TNF via a NF-jB-dependent pathway and whether this involves the endogenous production of TNF and PAF. In this study, we found that TNF and LPS markedly induced CXCL2 gene expression in IEC-6 cells, TNF within 30 min, peaking at 45 min, while LPS more slowly, peaking after 2 hr. TNF-and LPS-induced CXCL2 gene expression and protein release were completely blocked by pyrrolidine dithiocarbamate (PDTC) and helenalin, two potent NF-jB inhibitors. NEMO-binding domain peptide, a specific inhibitor of inhibitor protein jB kinase (IKK) activation, a major upstream kinase mediating NF-jB activation, significantly blocked CXCL2 gene expression and protein release induced by LPS. WEB2170 (PAF antagonist) and anti-TNF antibodies had no effect on LPS-induced CXCL2 expression. In conclusion, CXCL2 gene is expressed in enterocytes in response to both TNF and LPS. LPS-induced CXCL2 expression is dependent on NF-jB activation via the IKK pathway. The effect of LPS is independent of endogenous TNF and PAF.

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Section: Methodsmentioning

confidence: 99%

Section: M M U N O L O G Y O R I G I N a L A R T I C L Ementioning

confidence: 99%

Section: M M U N O L O G Y O R I G I N a L A R T I C L Ementioning

confidence: 99%

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Lipopolysaccharide induces CXCL2/macrophage inflammatory protein‐2 gene expression in enterocytes via NF‐κB activation: independence from endogenous TNF‐α and platelet‐activating factor

Plaen¹,

Han²,

Liu³

et al. 2006

Immunology

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“…Although evidence exists to support this latter possibility, the expression of various TLRs in enterocytes (Table 3) suggests the possibility that direct interaction of intestinal TLRs with cognate ligands (see Table 1) may occur. Enteric bacteria in general, and LPS in particular, have been shown to play a critical role in the development of many diseases of intestinal inflammation (69)(70)(71)(72), further suggesting the possibility that enterocyte TLR signaling may contribute directly to the development of these diseases.…”

Section: Tlr-dependent Signaling In the Intestinal Mucosa: A Role In mentioning

confidence: 99%

No Longer an Innocent Bystander: Epithelial Toll-Like Receptor Signaling in the Development of Mucosal Inflammation

Gribar

Richardson

Sodhi

et al. 2008

Mol Med

140

109

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Diseases of mucosal inflammation represent important causes of morbidity and mortality, and have led to intense research efforts to understand the factors that lead to their development. It is well accepted that a breakdown of the normally impermeant epithelial barrier of the intestine, the lung, and the kidney is associated with the development of inflammatory disease in these organs, yet significant controversy exists as to how this breakdown actually occurs, and how such a breakdown may lead to inflammation. In this regard, much work has focused upon the role of the epithelium as an "innocent bystander," a target of a leukocyte-mediated inflammatory cascade that leads to its destruction in the mucosal inflammatory process. However, recent evidence from a variety of laboratories indicates that the epithelium is not merely a passive component in the steps that lead to mucosal inflammation, but is a central participant in the process. In addressing this controversy, we and others have determined that epithelial cells express Toll-like receptors (TLRs) of the innate immune system, and that activation of TLRs by endogenous and exogenous ligands may play a central role in determining the balance between a state of "mucosal homeostasis," as is required for optimal organ function, and "mucosal injury," leading to mucosal inflammation and barrier breakdown. In particular, activation of TLRs within intestinal epithelial cells leads to the development of cellular injury and impairment in mucosal repair in the pathogenesis of intestinal inflammation, while activation of TLRs in the lung and kidney may participate in the development of pneumonitis and nephritis respectively. Recent work in support of these concepts is extensively reviewed, while essential areas of further study that are required to determine the significance of epithelial TLR signaling during states of health and disease are outlined.

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“…LPS is one of the most abundant proinflammatory stimuli in the gastrointestinal tract, and a break in the mucosal barrier leads to translocation of LPS and a sustained LPS challenge (19,20). This has direct local effects on the mucosal cells, including activation of the enterocytes (21)(22)(23)(24), as well as systemic effects with activation of immune cells (25,26). Sustained inhibition of epithelial restitution by LPS would lead to further bacterial translocation, potentiation of the inflammatory response, and further epithelial injury.…”

mentioning

confidence: 99%

Endotoxin Inhibits Intestinal Epithelial Restitution through Activation of Rho-GTPase and Increased Focal Adhesions

Çetin

Ford

Sysko

et al. 2004

Journal of Biological Chemistry

130

145

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Diseases of gut inflammation such as neonatal necrotizing enterocolitis (NEC) result after an injury to the mucosal lining of the intestine, leading to translocation of bacteria and endotoxin (lipopolysaccharide). Intestinal mucosal defects are repaired by the process of intestinal restitution, during which enterocytes migrate from healthy areas to sites of injury. In an animal model of NEC, we determined that intestinal restitution was significantly impaired compared with control animals. We therefore sought to determine the mechanisms governing enterocyte migration under basal conditions and after an endotoxin challenge. Here we show that the cytoskeletal reorganization and stress fiber formation required for migration in IEC-6 enterocytes requires RhoA. Enterocytes were found to express the endotoxin receptor Toll-like receptor 4, which served to bind and internalize lipopolysaccharide. Strikingly, endotoxin treatment significantly inhibited intestinal restitution, as measured by impaired IEC-6 cell migration across a scraped wound. Lipopolysaccharide was found to increase RhoA activity in a phosphatidylinositol 3-kinasedependent manner, leading to an increase in phosphorylation of focal adhesion kinase and an enhanced number of focal adhesions. Importantly, endotoxin caused a progressive, RhoA-dependent increase in cell matrix tension/contractility, which correlated with the observed impairment in enterocyte migration. We therefore conclude that endotoxin inhibits enterocyte migration through a RhoA-dependent increase in focal adhesions and enhanced cell adhesiveness, which may participate in the impaired restitution observed in experimental NEC.Necrotizing enterocolitis (NEC) 1 is the leading cause of death from gastrointestinal disease in neonates and is second to respiratory disease as the overall leading cause of morbidity and mortality in this population (1-3). Clinical manifestations of NEC include abdominal distention, feeding intolerance, and systemic sepsis, which result from the destruction of the intestinal barrier (4, 5). Mucosal breakdown may occur as a result of a perinatal insult, such as hypoxia, which allows bacteria and bacterial by-products to breach the normally impermeable mucosal barrier and initiate a local and systemic inflammatory response (4,6,7,9). This causes the release of proinflammatory cytokines, including tumor necrosis factor, platelet-activating factor, nitric oxide, and endotoxin, which lead to further epithelial injury (10 -13). Following mucosal damage, healing occurs initially through the process of epithelial restitution, in which healthy enterocytes adjacent to the sites of injury migrate toward the denuded mucosa to bridge the defect (14 -18). We hypothesize that the intestinal barrier defect in NEC does not result from epithelial injury alone but also from impaired restitution. This paper focuses specifically on the process of enterocyte migration, which is the sine qua non of epithelial restitution and mucosal healing.Although a variety of cytokines may be importan...

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Endotoxin, but not platelet‐activating factor, activates nuclear factor‐κB and increases IκBα and IκBβ turnover in enterocytes

Cited by 27 publications

References 36 publications

Lipopolysaccharide induces CXCL2/macrophage inflammatory protein‐2 gene expression in enterocytes via NF‐κB activation: independence from endogenous TNF‐α and platelet‐activating factor

Lipopolysaccharide induces CXCL2/macrophage inflammatory protein‐2 gene expression in enterocytes via NF‐κB activation: independence from endogenous TNF‐α and platelet‐activating factor

No Longer an Innocent Bystander: Epithelial Toll-Like Receptor Signaling in the Development of Mucosal Inflammation

Endotoxin Inhibits Intestinal Epithelial Restitution through Activation of Rho-GTPase and Increased Focal Adhesions

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