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Activation of HIF-1? does not increase intestinal tumorigenesis.

ABSTRACT: The hypoxic response is mediated by two transcription factors, hypoxia-inducible factor (HIF)-1? and HIF-2?. These highly homologous transcription factors are induced in hypoxic foci and regulate cell metabolism, angiogenesis, cell proliferation, and cell survival. HIF-1? and HIF-2? are activated early in cancer progression and are important in several aspects of tumor biology. HIF-1? and HIF-2? have overlapping and distinct functions. In the intestine, activation of HIF-2? increases inflammation and colon carcinogenesis in mouse models. Interestingly, in ischemic and inflammatory diseases of the intestine, activation of HIF-1? is beneficial and can reduce intestinal inflammation. HIF-1? is a critical transcription factor regulating epithelial barrier function following inflammation. The beneficial value of pharmacological agents that chronically activate HIF-1? is decreased due to the tumorigenic potential of HIFs. The present study tested the hypothesis that chronic activation of HIF-1? may enhance colon tumorigenesis. Two models of colon cancer were assessed, a sporadic and a colitis-associated colon cancer model. Activation of HIF-1? in intestinal epithelial cells does not increase carcinogenesis or progression of colon cancer. Together, the data provide proof of principle that pharmacological activation of HIF-1? could be a safe therapeutic strategy for inflammatory bowel disease.

SUBMITTER: Xue X

PROVIDER: S-EPMC4101679 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Activation of HIF-1α does not increase intestinal tumorigenesis.

Xue Xiang X Ramakrishnan Sadeesh K SK Shah Yatrik M YM

American journal of physiology. Gastrointestinal and liver physiology 20140529 2

The hypoxic response is mediated by two transcription factors, hypoxia-inducible factor (HIF)-1α and HIF-2α. These highly homologous transcription factors are induced in hypoxic foci and regulate cell metabolism, angiogenesis, cell proliferation, and cell survival. HIF-1α and HIF-2α are activated early in cancer progression and are important in several aspects of tumor biology. HIF-1α and HIF-2α have overlapping and distinct functions. In the intestine, activation of HIF-2α increases inflammatio ...[more]

PMID: 24875099

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Project description:Background & aimsAlcoholic liver disease (ALD) is characterized by gut dysbiosis and increased gut permeability. Hypoxia inducible factor 1α (HIF-1α) has been implicated in transcriptional regulation of intestinal barrier integrity and inflammation. We aimed to test the hypothesis that HIF-1α plays a critical role in gut microbiota homeostasis and the maintenance of intestinal barrier integrity in a mouse model of ALD.MethodsWild-type (WT) and intestinal epithelial-specific Hif1a knockout mice (IEhif1α-/-) were pair-fed modified Lieber-DeCarli liquid diet containing 5% (w/v) alcohol or isocaloric maltose dextrin for 24 days. Serum levels of alanine aminotransferase and endotoxin were determined. Fecal microbiota were assessed. Liver steatosis and injury, and intestinal barrier integrity were evaluated.ResultsAlcohol feeding increased serum levels of alanine aminotransferase and lipopolysaccharide, hepatic triglyceride concentration, and liver injury in the WT mice. These deleterious effects were exaggerated in IEhif1α-/- mice. Alcohol exposure resulted in greater reduction of the expression of intestinal epithelial tight junction proteins, claudin-1 and occludin, in IEhif1α-/- mice. In addition, cathelicidin-related antimicrobial peptide and intestinal trefoil factor were further decreased by alcohol in IEhif1α-/- mice. Metagenomic analysis showed increased gut dysbiosis and significantly decreased Firmicutes/Bacteroidetes ratio in IEhif1α-/- mice compared to the WT mice exposed to alcohol. An increased abundance of Akkermansia and a decreased level of Lactobacillus in IEhif1α-/- mice were also observed. Non-absorbable antibiotic treatment reversed the liver steatosis in both WT and IEhif1α-/- mice.ConclusionIntestinal HIF-1α is essential for the adaptative response to alcohol-induced changes in intestinal microbiota and barrier function associated with elevated endotoxemia and hepatic steatosis and injury.Lay summaryAlcohol consumption alters gut microbiota and multiple intestinal barrier protecting factors that are regulated by intestinal hypoxia-inducible factor 1α (HIF-1α). Absence of intestinal HIF-1α exacerbates gut leakiness leading to an increased translocation of bacteria and bacterial products to the liver, consequently causing alcoholic liver disease. Intestinal specific upregulation of HIF-1α could be developed as a novel approach for the treatment of alcoholic liver disease.

Project description:BackgroundEpithelial-mesenchymal transition (EMT) of mesothelial cells is a key step in the peritoneal fibrosis (PF). Recent evidence indicates that signal transducer and activator of transcription 3 (STAT3) might mediate the process of renal fibrosis, which could induce the expression of hypoxia-inducible factor-1α (HIF-1α). Here, we investigated the effect of STAT3 activation on HIF-1α expression and the EMT of mesothelial cells, furthermore the role of pharmacological blockade of STAT3 in the process of PF during peritoneal dialysis (PD) treatment.MethodsFirstly, we investigated the STAT3 signaling in human peritoneal mesothelial cells (HPMCs) from drained PD effluent. Secondly, we explored the effect of STAT3 signaling activation on the EMT and the expression of HIF-1α in human mesothelial cells (Met-5A) induced by high glucose. Finally, peritoneal fibrosis was induced by daily intraperitoneal injection with peritoneal dialysis fluid (PDF) so as to explore the role of pharmacological blockade of STAT3 in this process.ResultsCompared with the new PD patient, the level of phosphorylated STAT3 was up-regulated in peritoneal mesothelial cells from long-term PD patients. High glucose (60 mmol/L) induced over-expression of Collagen I, Fibronectin, α-SMA and reduced the expression of E-cadherin in Met-5A cells, which could be abrogated by STAT3 inhibitor S3I-201 pretreatment as well as by siRNA for STAT3. Furthermore, high glucose-mediated STAT3 activation in mesothelial cells induced the expression of HIF-1α and the profibrotic effect of STAT3 signaling was alleviated by siRNA for HIF-1α. Daily intraperitoneal injection of high-glucose based dialysis fluid (HG-PDF) induced peritoneal fibrosis in the mice, accompanied by the phosphorylation of STAT3. Immunostaining showed that phosphorylated STAT3 was expressed mostly in α-SMA positive cells in the peritoneal membrane induced by HG-PDF. Administration of S3I-201 prevented the progression of peritoneal fibrosis, angiogenesis, macrophage infiltration as well as the expression of HIF-1α in the peritoneal membrane induced by high glucose.ConclusionsTaken together, these findings identified a novel mechanism linking STAT3/HIF-1α signaling to peritoneal fibrosis during long-term PD treatment. It provided the first evidence that pharmacological inhibition of STAT3 signaling attenuated high glucose-mediated mesothelial cells EMT as well as peritoneal fibrosis.

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Activation of HIF-1? does not increase intestinal tumorigenesis.

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Activation of HIF-1α does not increase intestinal tumorigenesis.

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