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Raf protects against colitis by promoting mouse colon epithelial cell survival through NF-kappaB.

ABSTRACT: BACKGROUND & AIMS:Raf-1 kinase is a key regulator of a number of cellular processes, which promote the maintenance of a healthy colon epithelium. This study addresses the role of Raf in epithelial cell survival in response to dextran sulfate sodium (DSS)-induced injury and inflammation. METHODS:Inducible intestinal epithelium-specific Raf knockout mice were generated and subjected to acute colitis followed by a short recovery period. Colon sections were analyzed by in situ oligo ligation or immunostaining for Ki67, phospho-extracellular signal regulated kinase, and nuclear factor-kappaB p65. Western blot analysis and terminal deoxynucleotidyl transferase nick-end labeling assays were performed on Raf small interfering RNA-transfected young adult mouse colon cells following DSS treatment. RESULTS:We report that Raf protects against epithelial injury and inflammation and promotes recovery from acute DSS-induced colitis by both MAPK/ERK kinase (MEK)-dependent and -independent pathways. Furthermore, we demonstrate that Raf induces novel cell survival responses through activating nuclear factor-kappaB in a MEK-independent manner. CONCLUSIONS:These novel findings indicate a protective role for Raf in colon epithelium following ulcerative damage through inhibiting cell apoptosis and promoting proliferation with important implications for responses such as inflammation-associated carcinogenesis.

SUBMITTER: Edelblum KL

PROVIDER: S-EPMC2640938 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Raf protects against colitis by promoting mouse colon epithelial cell survival through NF-kappaB.

Edelblum Karen L KL Washington M Kay MK Koyama Tatsuki T Robine Sylvie S Baccarini Manuela M Polk D Brent DB

Gastroenterology 20080430 2

<h4>Background & aims</h4>Raf-1 kinase is a key regulator of a number of cellular processes, which promote the maintenance of a healthy colon epithelium. This study addresses the role of Raf in epithelial cell survival in response to dextran sulfate sodium (DSS)-induced injury and inflammation.<h4>Methods</h4>Inducible intestinal epithelium-specific Raf knockout mice were generated and subjected to acute colitis followed by a short recovery period. Colon sections were analyzed by in situ oligo l ...[more]

PMID: 18598699

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Project description:BackgroundSilicosis is a complex lung disease for which no successful treatment is available and therefore lung transplantation is a potential alternative. Tumor necrosis factor alpha (TNFalpha) plays a central role in the pathogenesis of silicosis. TNFalpha signaling is mediated by the transcription factor, Nuclear Factor (NF)-kappaB, which regulates genes controlling several physiological processes including the innate immune responses, cell death, and inflammation. Therefore, inhibition of NF-kappaB activation represents a potential therapeutic strategy for silicosis.Methods/findingsIn the present work we evaluated the lung transplant database (May 1986-July 2007) at the University of Pittsburgh to study the efficacy of lung transplantation in patients with silicosis (n = 11). We contrasted the overall survival and rate of graft rejection in these patients to that of patients with idiopathic pulmonary fibrosis (IPF, n = 79) that was selected as a control group because survival benefit of lung transplantation has been identified for these patients. At the time of lung transplantation, we found the lungs of silica-exposed subjects to contain multiple foci of inflammatory cells and silicotic nodules with proximal TNFalpha expressing macrophage and NF-kappaB activation in epithelial cells. Patients with silicosis had poor survival (median survival 2.4 yr; confidence interval (CI): 0.16-7.88 yr) compared to IPF patients (5.3 yr; CI: 2.8-15 yr; p = 0.07), and experienced early rejection of their lung grafts (0.9 yr; CI: 0.22-0.9 yr) following lung transplantation (2.4 yr; CI:1.5-3.6 yr; p<0.05). Using a mouse experimental model in which the endotracheal instillation of silica reproduces the silica-induced lung injury observed in humans we found that systemic inhibition of NF-kappaB activation with a pharmacologic inhibitor (BAY 11-7085) of IkappaB alpha phosphorylation decreased silica-induced inflammation and collagen deposition. In contrast, transgenic mice expressing a dominant negative IkappaB alpha mutant protein under the control of epithelial cell specific promoters demonstrate enhanced apoptosis and collagen deposition in their lungs in response to silica.ConclusionsAlthough limited by its size, our data support that patients with silicosis appear to have poor outcome following lung transplantation. Experimental data indicate that while the systemic inhibition of NF-kappaB protects from silica-induced lung injury, epithelial cell specific NF-kappaB inhibition appears to aggravate the outcome of experimental silicosis.

Project description:Short-term fasting protects mice from lethal doses of chemotherapy through undetermined mechanisms. Herein, we demonstrate that fasting preserves small intestinal (SI) architecture by maintaining SI stem cell viability and SI barrier function following exposure to high-dose etoposide. Nearly all SI stem cells were lost in fed mice, whereas fasting promoted sufficient SI stem cell survival to preserve SI integrity after etoposide treatment. Lineage tracing identified multiple SI stem cell populations, marked by Lgr5, Bmi1 or HopX expression, that contributed to fasting-induced survival. DNA repair and DNA damage response genes were elevated in SI stem/progenitor cells of fasted etoposide-treated mice, which importantly correlated with faster resolution of DNA double strand breaks and less apoptosis. Thus, fasting preserved SI stem cell viability as well as SI architecture and barrier function suggesting that fasting may reduce host toxicity in patients undergoing dose intensive chemotherapy. Intestines were harvested 3 h post-etoposide injection, flushed with PBS, and then flushed with ice-cold Methacarn (60% methanol, 30% chloroform, 10% acetic acid) to fix the tissue while preserving RNA integrity. Fixed intestines were rinsed with 70% ethanol, embedded in 2% agar followed by paraffin embedding. Sections were deparrafinized and dehydrated through xylene and an increasing gradient of ethanol. Laser capture microdissection was performed using the Acturus PixCell IIe, with the following settings: spot size power 80, duration 1 ms, repeat 0.2 s, target 0.150 V, current 1.82 mA. RNA was isolated from the CapSure HS LCM Caps (Applied Biosystem) using the PicoPure RNA Isolation kit (Applied Biosystems). All RNA samples were treated with DNaseI (Qiagen). Four biological replicates were used for each of the following treatments: Fasted Etoposide, Fed Etoposide. Each group had 2 male and 2 females samples. 4-6 week old Lgr5EGFP-IRES-CreERT2/+ mice were dosed with 80mg/kg etoposide (i.v.).

Dataset Information

Raf protects against colitis by promoting mouse colon epithelial cell survival through NF-kappaB.

Publications

Raf protects against colitis by promoting mouse colon epithelial cell survival through NF-kappaB.

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