Post-transcriptional Regulation of Smad7 in the Gut of Patients With Inflammatory Bowel Disease

doi:10.1053/j.gastro.2005.09.005

Gastroenterology

Volume 129, Issue 5, November 2005, Pages 1420-1429

https://doi.org/10.1053/j.gastro.2005.09.005 Get rights and content

Background & Aims: Transforming growth factor (TGF)-β1 is one of the most powerful endogenous negative regulators of inflammation. In patients with inflammatory bowel disease, despite abundant local TGF-β1, there is a failure of TGF-β–mediated negative regulation of nuclear factor κB activation and proinflammatory cytokine production because of increased intracellular expression of the endogenous inhibitor of TGF-β1 signaling, Smad7. In this study, we examined the molecular mechanism underlying the induction of Smad7 in the human gut. Methods: Whole intestinal mucosal and lamina propria mononuclear cell samples were analyzed for Smad7 by real-time polymerase chain reaction and Western blotting. Smad7 ubiquitination and acetylation, and interaction of Smad7 with the intrinsic histone acetyltransferase, p300, were examined by immunoprecipitation and Western blotting. The effect of p300 silencing on Smad7 expression was determined in Crohn’s disease lamina propria mononuclear cells. Results: We showed that Smad7 is not transcriptionally regulated in human gut but that its increase in patients with inflammatory bowel disease is due to posttranscriptional acetylation and stabilization by p300, which prevents Smad7 ubiquitination and degradation in the proteasome. Hence, Smad7 protein in cells from normal gut is ubiquitinated and rapidly degraded. In contrast, in inflamed gut, Smad7 is acetylated and not ubiquitinated, is not degraded, and can be decreased by short interfering RNA to p300. Conclusions: These results identify posttranslational protein modification as of importance in chronic gut inflammation in humans.

Section snippets

Patients and Samples

Mucosal samples were taken from fresh intestinal resection specimens of 27 patients with active CD unresponsive to therapy. In 14 patients, the primary site of disease was the terminal ileum; in 13, the disease was present in both the ileum and the colon. Eighteen patients were taking corticosteroids, 6 were taking corticosteroids plus azathioprine, and 3 were taking mesalazine plus antibiotics. Twenty patients with CD had fibrostenosing disease. Additional mucosal samples were taken during

Smad7 Protein but not Messenger RNA Is Enhanced in IBD

Studies performed in cell lines have previously shown that intracellular levels of Smad7 can be regulated by external stimuli that enhance gene transcription.7, 10 Therefore, to examine if Smad7 is regulated at the transcriptional level in IBD, total RNA was extracted from intestinal samples of patients with CD, patients with UC, and healthy controls and analyzed for Smad7 by real-time PCR. No difference in terms of Smad7 RNA transcripts was seen between patients with IBD and healthy controls (

Discussion

In this study, we attempted to identify the molecular mechanisms that control Smad7 during chronic intestinal inflammation in humans. These studies are technically demanding, limited as they are by cell yields from human gut, in contrast to studies with cell lines; however, they are crucial if basic mechanisms elucidated in vitro are to be extended to humans. We provide evidence that Smad7 RNA is not up-regulated in CD and UC tissue, although intestinal samples taken from the same patients

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Smad7 as a positive regulator of intestinal inflammatory diseases
2023, Current Research in Immunology
In physiological conditions, the human gut contains more immune cells than the rest of the body, but no overt tissue damage occurs, because several regulatory mechanisms control the activity of such cells thus preventing excessive and detrimental responses. One such mechanism relies on the action of transforming growth factor (TGF)-β1, a cytokine that targets both epithelial cells and many immune cell types. Loss of TGF-β1 function leads to intestinal pathology in both mice and humans. For instance, disruption of TGF-β1 signaling characterizes the destructive immune-inflammatory response in patients with Crohn’s disease and patients with ulcerative colitis, the major human inflammatory bowel disease (IBD) entities. In these pathologies, the defective TGF-β1-mediated anti-inflammatory response is associated with elevated intestinal levels of Smad7, an antagonist of TGF-β1 signaling. Consistently, knockdown of Smad7 restores TGF-β1 function thereby attenuating intestinal inflammation in patients with IBD as well as in mice with IBD-like colitis. Up-regulation of Smad7 and reduced TGF-β1 signaling occurs also in necrotizing enterocolitis, environmental enteropathy, refractory celiac disease, and cytomegalovirus-induced colitis. In this article, we review the available data supporting the pathogenic role of Smad7 in the gastrointestinal tract and discuss whether and how targeting Smad7 can help attenuate detrimental immuno-inflammatory responses in the gut.
TGF-β activity restoration and phosphodiesterase 4 inhibition as therapeutic options for inflammatory bowel diseases
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Citation Excerpt :
In particular, Smad7 deficiency restored TGF-β responsiveness and the co-inhibitory expression of programmed death ligand (PDL) on DC [42]. In IBD, Smad7 is regulated at post-transcriptional levels by a mechanism that prevents its ubiquitination and degradation by the proteasome [43]. Other factors may be involved in the regulation of Smad7 in IBD.
In the last decades, the better understanding of inflammatory bowel diseases (IBD) pathogenesis has contributed to the identification of new therapeutic targets that can be modulated to induce and maintain disease remission. Monoclonal antibodies against tumor necrosis factor, interleukin (IL)-12/IL-23p40, and the integrin α4β7 and inhibitors of Janus kinase molecules are valid compounds to limit the function of molecules implicated in the control of IBD-related inflammation. However, not all patients respond to treatment with such drugs, some of them lose response over time and others develop serious side effects, such as infections or malignancies, which lead to the discontinuation of the therapy. Thus, an intensive research is ongoing with the goal to identify new targets and develop novel therapeutic options. In this context, restoration of TGF-β activity and inhibition of phosphodiesterase 4 (PD4) represent two relevant strategies. TGF-β is an immunesuppressive cytokine, whose activity is severely impaired in IBD due to the abundance of the intracellular inhibitor Smad7. Knockdown of Smad7 with a specific antisense oligonucleotide restores TGF-β signalling and dampens effector immune responses in pre-clinical studies and initial clinical trials in Crohn’s disease patients, even though a recent phase 3 trial was discontinued due to an apparent inefficacy. PD4 inhibition determines the increase of intracellular levels of cyclic adenosine monophosphate, a mechanism that decreases pro-inflammatory cytokine production. A recent phase 2 study has shown that oral administration of PD4 associates with clinical benefit in patients with ulcerative colitis. In this article, we review the rationale and the available data relative to the use of these two agents in IBD.
Smad7 Controls Immunoregulatory PDL2/1-PD1 Signaling in Intestinal Inflammation and Autoimmunity
2019, Cell Reports
Smad7, a negative regulator of TGF-β signaling, has been implicated in the pathogenesis and treatment of inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC). Here, we found that Smad7 mediates intestinal inflammation by limiting the PDL2/1-PD1 axis in dendritic cells (DCs) and CD4⁺T cells. Smad7 deficiency in DCs promotes TGF-β responsiveness and the co-inhibitory molecules PDL2/1 on DCs, and it further imprints T cell-PD1 signaling to promote Treg differentiation. DC-specific Smad7 deletion mitigates DSS-induced colitis by inducing CD103⁺PDL2/1⁺DCs and Tregs. In addition, Smad7 deficiency in CD4⁺T cells promotes PD1 and PD1-induced Tregs in vitro. The transfer of Smad7-deficient CD4⁺T cells enhances Tregs in vivo and protects against T cell-mediated colitis. Furthermore, Smad7 antisense ameliorates DSS-induced UC, increasing TGF-β and PDL2/1-PD1 signaling. Enhancing PD1 signaling directly via Fc-fused PDL2/1 is also beneficial. Our results identify how Smad7 mediates intestinal inflammation and leverages these pathways therapeutically, providing additional strategies for IBD intervention.
Effects of Mongersen (GED-0301) on Endoscopic and Clinical Outcomes in Patients With Active Crohn's Disease
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GED-0301 is an antisense oligodeoxynucleotide with a sequence complementary to the Smad7 mRNA transcript. Smad7 is a negative regulator of transforming growth factor-β, which is increased in the intestinal mucosa of patients with active Crohn’s disease (CD). We randomly assigned 63 CD patients to 4-, 8-, or 12-week treatment groups receiving oral GED-0301 (160 mg/day). The primary objective was to determine GED-0301’s effect on endoscopic CD measures; secondary objectives included effects on clinical activity. Endoscopic improvement was observed in 37% of participants with evaluable endoscopy results at week 12. At week 12, 32% (4 weeks), 35% (8 weeks), and 48% (12 weeks) of patients receiving GED-0301 were in remission (CD activity index score <150); corresponding reductions from baseline in mean CD activity index scores were −124, −112, and −133 points. No new safety signals were observed. These findings support a GED-0301 benefit in active CD. ClinicalTrials.gov no: NCT02367183.
TGF-β1 signaling and Smad7 control T-cell responses in health and immune-mediated disorders
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N-Acetylglucosamine and its dimer ameliorate inflammation in murine colitis by strengthening the gut barrier function
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: Supported by the “Fondazione Umberto Di Mario” (Rome, Italy), the Broad Medical Research Program Foundation (grant no. IBD-00200R), and Giuliani SpA, Milan, Italy.

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Clinical–alimentary tractPost-transcriptional Regulation of Smad7 in the Gut of Patients With Inflammatory Bowel Disease

Section snippets

Patients and Samples

Smad7 Protein but not Messenger RNA Is Enhanced in IBD

Discussion

J Biol Chem

Cell

J Biol Chem

Mol Cell

Trends Immunol

Mol Cell

Biochem Pharmacol

J Biol Chem

Curr Biol

Gastroenterology

Gastroenterology

Transforming growth factor beta signal transduction

J Leukoc Biol

Effector and regulatory lymphoid cells and cytokines in mucosal sites

Curr Top Microbiol Immunol

Clinical–alimentary tract
Post-transcriptional Regulation of Smad7 in the Gut of Patients With Inflammatory Bowel Disease