Hypoxia-Inducible Factor Augments Experimental Colitis Through an MIF–Dependent Inflammatory Signaling Cascade

Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Gastroenterology (Impact Factor: 16.72). 07/2008; 134(7):2036-48, 2048.e1-3. DOI: 10.1053/j.gastro.2008.03.009
Source: PubMed


Colon epithelial cells are critical for barrier function and contain a highly developed immune response. A previous study has shown hypoxia-inducible factor (HIF) as a critical regulator of barrier protection during colon epithelial injury. However, the role of HIF signaling in colon mucosal immunity is not known.
With the use of cre/loxP technology, intestinal-specific disruption of von Hippel-Lindau tumor suppressor protein (Vhl), hypoxia-inducible factor (Hif)-1alpha, and aryl hydrocarbon nuclear translocator (Arnt) was generated. Colon inflammation was induced using a dextran sulfate sodium (DSS)-induced colitis model, and the mice were analyzed by histologic analysis, Western blot analysis, and quantitative polymerase chain reaction.
In mice, colonic epithelium disruption of Vhl resulted in constitutive expression of HIF, which initiated an increase in inflammatory infiltrates and edema in the colon. These effects were ameliorated in mice by disruption of both Vhl and Arnt/Hif1beta (which inactivates HIF). In a DSS-induced colitis model, increased HIF expression correlated with more severe clinical symptoms and an increase in histologic damage, while disruption of both Vhl and Arnt in the colon epithelium inhibited these effects. Furthermore, colons with constitutive activation of HIF displayed increased expression of proinflammatory mediators that were synergistically potentiated following DSS administration and reduced by inhibition of the proinflammatory and direct HIF target gene macrophage migration inhibitory factor.
The present study shows that a chronic increase in HIF signaling in the colon epithelial cells initiates a hyperinflammatory reaction that may have important implications in developing therapeutic strategies for inflammatory bowel disease.

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Available from: Volker H Haase
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    • "Sulindactreated Hif1α ΔIEC mice showed significantly lower expression of MIF expression in the colon compared with Hif1α F/F mice (Fig. 3G). These results are consistent with the previously reported MIF-dependent, pro-inflammatory role of HIF, although in that study the effect was primarily attributed to HIF2α (Shah et al., 2008). Expression of the macrophage-specific marker F4/80 tended to increase with the sulindac diet, but there were no significant differences between the two genotypes (Fig. 3H). "
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    ABSTRACT: Hypoxia inducible factor 1α (HIF1α) is a transcription factor that regulates adaptation of cells to hypoxic microenvironments, for example inside solid tumors. Stabilization of HIF1α can also occur in normoxic conditions in inflamed tissue or as a result of inactivating mutations in negative regulators of HIF1α. Aberrant overexpression of HIF1α in many different cancers has led to intensive efforts to develop HIF1α targeted therapies. However, the role of HIF1α is still poorly understood in chronic inflammation that predisposes the colon to carcinogenesis. We have previously reported that Hif1α transcription is upregulated and the protein is stabilised in inflammatory lesions which are caused by the non-steroidal anti-inflammatory drug (NSAID) sulindac in the mouse proximal colon. Here we exploited this side effect of long-term sulindac administration to analyse the role of Hif1α in colon inflammation using mice with a Villin cre-induced deletion of Hif1α exon 2 in the intestinal epithelium (Hif1α(ΔIEC) ). We also analysed the effect of sulindac sulfide on the Aryl Hydrocarbon Receptor (AHR) pathway in vitro in colon cancer cells. Most sulindac-treated mice developed visible lesions, resembling the appearance of flat or depressed adenomas in the human colon, surrounded by macroscopically normal mucosa. Hif1α(ΔIEC) mice still developed lesions but they were smaller than in the Hif1α-floxed siblings (Hif1α(F/F)). Microscopically, Hif1α(ΔIEC) mice had significantly less severe colon inflammation than Hif1α(F/F) mice. Molecular analysis showed reduced MIF and increased E-cadherin mRNA expression in the colon of sulindac-treated Hif1α(ΔIEC) mice. However, immunohistochemistry analysis revealed a defect of E-cadherin protein expression in sulindac-treated Hif1α(ΔIEC) mice. Sulindac sulfide treatment in vitro upregulated Hif1α, c-JUN and IL8 expression through the AHR pathway. Taken together, Hif1α expression augments inflammation in the proximal colon of sulindac-treated mice and AHR activation by sulindac may lead to the reduction of E-cadherin protein levels through the MAPK pathway. © 2015. Published by The Company of Biologists Ltd.
    Full-text · Article · Jul 2015 · Disease Models and Mechanisms
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    • "One of the best characterized and also most well-known MIF inhibitors is (S,R)-3-(4-hydroxyphenyl)- 4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) (reviewed in Al-Abed et al., 2011). It was shown that ISO-1 has beneficial effects in experimental colitis (Shah et al., 2008), experimental allergic neuritis (Nicoletti et al., 2005) and in endotoxemia (Al-Abed et al., 2005). In MIF's homotrimeric structure a hydrophobic pocket region formed between each adjacent subunit plays an important role in its biological function, as evidenced by the fact that ISO-1 binding of this region decreases downstream MIF signaling, MIF biological activities and clinical outcomes that are associated with MIF (Al-Abed et al., 2011). "
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    ABSTRACT: Macrophage migration inhibitory factor is a multifunctional cytokine involved in the regulation of immune processes and also in apoptosis induction. Elevated MIF expression is detrimental for insulin-producing beta cells and MIF inhibition protected beta cells from several cytotoxic insults such as inflammatory cytokines, high fatty acids or high glucose concentrations. Therefore, the aim of this study was to investigate two newly synthesized small molecule MIF inhibitors (K664-1 and K647-1) and to compare them with previously established effects of the prototypical MIF inhibitor, ISO-1. Our results indicate that K664-1 and K647-1 are 160- and 40-fold more effective in inhibition of MIF's tautomerase activity than ISO-1. Also, new inhibitors confer beta cell protection from cytokine-triggered apoptosis at significantly lower concentrations than ISO-1. Although all three MIF inhibitors inhibit caspase 3 activity, K664-1 and K647-1 suppress pro-apoptotic BAX protein expression and up-regulate anti-apoptotic Bcl-2 mRNA. Finally, all three MIF inhibitors operate through blockade of nitric oxide production stimulated by cytokines. In conclusion, two novel MIF inhibitors are more potent than ISO-1 and operate through inhibition of the mitochondria-related apoptotic pathway. We propose that these compounds represent a unique class of anti-MIF antagonists that should be further tested for therapeutic use.
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    • "Chronic hypoxia regularly occurs in solid tumors, including CRC and CAC; in addition, increases in HIF-dependent signaling can also ensue from activation of oncogenic pathways, including the Wnt/β-catenin, Ras/Raf/MAPK and PI3K/Akt/mTOR pathways, as well as from tumor suppressor gene silencing (66,67). On the other hand, a chronic increase in HIF signaling in colon epithelial cells has been reported to trigger an inflammatory response through direct activation of genes encoding pro-inflammatory cytokines (68,69) and through extensive cross-talk with inflammatory transcription factors, such as STAT3 and NFκB (70). Conversely, an inflammatory microenvironment can sustain high levels of HIF signaling through both oxygen-dependent and -independent mechanisms (71–74). "
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    ABSTRACT: The observation that cancer often arises at sites of chronic inflammation has prompted the idea that carcinogenesis and inflammation are deeply interwoven. In fact, the current literature highlights a role for chronic inflammation in virtually all the steps of carcinogenesis, including tumor initiation, promotion and progression. The aim of the present article is to review the current literature on the involvement of chronic inflammation in the initiation step and in the very early phases of tumorigenesis, in a type of cancer where adult stem cells are assumed to be the cells of origin of neoplasia. Since the gastrointestinal tract is regarded as the best-established model system to address the liaison between chronic inflammation and neoplasia, the focus of this article will be on intestinal cancer. In fact, the anatomy of the intestinal epithelial lining is uniquely suited to study adult stem cells in their niche, and the bowel crypt is an ideal developmental biology system, as proliferation, differentiation and cell migration are all distributed linearly along the long axis of the crypt. Moreover, crypt stem cells are regarded today as the most likely targets of neoplastic transformation in bowel cancer. More specifically, the present review addresses the molecular mechanisms whereby a state of chronic inflammation could trigger the neoplastic process in the intestine, focusing on the generation of inflammatory cues evoking enhanced proliferation in cells not initiated but at risk of neoplastic transformation because of their stemness. Novel experimental approaches, based on triggering an inflammatory stimulus in the neighbourhood of adult intestinal stem cells, are warranted to address some as yet unanswered questions. A possible approach, the targeted transgenesis of Paneth cells, may be aimed at 'hijacking' the crypt stem cell niche from a status characterized by the maintenance of homeostasis to local chronic inflammation, with the prospect of initiating neoplastic transformation in that site.
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