Tumor suppressor FOXO3 participates in the regulation of intestinal inflammation

Abstract

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is characterized by chronic mucosal injury and the infiltration of inflammatory cells. Tumor suppressor FOXO3 regulates gene expression and its translocation to the cytosol leads to the abrogation of its transcriptional function. We have previously shown that bacterial infection regulates FOXO3 in intestinal epithelial cells and increases cytokine levels. As TNFa is a major contributor in intestinal inflammation, the aim of this study was to assess its effect on FOXO3 and FOXO3's contribution to intestinal inflammation in vitro and in vivo. TNFa induces the translocation of nuclear FOXO3 into the cytosol where it undergoes proteasomal degradation in human intestinal HT-29 cells. Proximally, the PI3K and IKK pathways mediate TNFa-induced FOXO3 phosphorylation. In FOXO3-silenced HT-29 cells, TNFa-induced IL-8 expression is increased B83%. In vivo, Foxo3 is present in the nuclei and cytosol of colonic crypt epithelia. In DSS-induced colonic inflammation, Foxo3's nuclear localization is lost and it is only found in the cytosol. Consistent with a role for Foxo3 in colitis, Foxo3-deficient mice treated with DSS developed more severe colonic inflammation with an increased number of intraepithelial lymphocytes and PMNs infiltrated in the epithelia, than wild-type mice. In summary, TNFa inactivates FOXO3 in intestinal epithelia through the PI3K and IKK pathways and FOXO3 inactivation leads to the upregulation of IL-8 in vitro; in vivo Foxo3 is in the cytosol of inflamed colonic epithelia and Foxo3 deficiency leads to severe intestinal inflammation.

FOXO3 Growth Inhibition of Colonic Cells Is Dependent on Intraepithelial Lipid Droplet Density

“…Immunofluorescent Staining-Experimental monolayers grown on coverslips were washed, fixed with paraformaldehyde, and immunofluorescently stained for FOXO3 and vimentin as described previously (4,30).…”

“…Protein Extraction and Immunoblot-Experimental monolayers and tissue were washed with serum-free media, then total and fractionated protein was extracted as previously described (4,30). Equal amounts of protein, after the concentration was determined by the Bradford assay (Bio-Rad), were loaded on SDS-PAGE and transferred to nitrocellulose membranes (Bio-Rad).…”

Blunting Autoantigen-induced FOXO3a Protein Phosphorylation and Degradation Is a Novel Pathway of Glucocorticoids for the Treatment of Systemic Lupus Erythematosus

“…For example, FOXO1 has often been showed to activate NF-B (19,20); however, evidence indicates that FOXO3a and FOXO4 may play an inhibitory role in autoimmune and inflammatory diseases by repressing NF-B activity (21,22). Mice with a defect in FOXO3a were found to predispose to a spontaneous multisystemic inflammatory syndrome, accompanied by an up-regulated production of pro-inflammatory cytokines (21,23). Accumulating evidence also indicates the expression of FOXO3a may be associated with diverse inflammatory diseases, such as asthma, ulcerative colitis Crohn's disease, and rheumatoid arthritis in clinical patients (24 -26).…”

“…It was found that FOXO3a, a potential inflammation repressor (21,23), was one of the molecules that was down-regulated in response to ALD-DNA stimulation, although GC treatment significantly rescued FOXO3a expression (supplemental Table 1). Further Western blotting analysis confirmed that ALD-DNA stimulation significantly down-regulated FOXO3a protein level in RAW264.7 cells and mouse peritoneal macrophages, although GCtreatmentcouldrescuetheexpressionofFOXO3ainadose-dependent manner (Fig.…”

RUNX3 is multifunctional in carcinogenesis of multiple solid tumors

“…The fact that RUNX3 physically interacts with Forkhead box O3a (FOXO3a) tumor suppressor protein at the proapoptotic gene Bim promoter to promote transcription and apoptosis (Yamamura et al, 2006) prompts speculation of functions for RUNX3 in other Foxo3A-related activities, and these include regulation of intestinal inflammation (Snoeks et al, 2009), AKT oncogenic signaling pathway, response to oxidative stress (Brunet et al, 2004), as well as activation of ATM during DNA damage . Interestingly, FOXOs protects hematopoietic stem cells from oxidative stress and is thus necessary for long-term maintenance of hematopoietic stem cells in the progenitor compartment (Tothova and Gilliland, 2007;.…”