Blocking Smad7 restores TGF-β1 signaling in chronic inflammatory bowel disease
Giovanni Monteleone, … , Howard W. Steer, Thomas T. MacDonald
Giovanni Monteleone, … , Howard W. Steer, Thomas T. MacDonald
Published August 15, 2001
Citation Information: J Clin Invest. 2001;108(4):601-609. https://doi.org/10.1172/JCI12821.
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Article

Blocking Smad7 restores TGF-β1 signaling in chronic inflammatory bowel disease

Abstract

TGF-β1 functions as a negative regulator of T cell immune responses, signaling to target cells using the Smad family of proteins. We show here that Smad7, an inhibitor of TGF-β1 signaling, is overexpressed in inflammatory bowel disease (IBD) mucosa and purified mucosal T cells. Both whole tissue and isolated cells exhibit defective signaling through this pathway, as measured by phospho-Smad3 immunoreactivity. Specific antisense oligonucleotides for Smad7 reduce Smad7 protein expression in cells isolated from patients with IBD, permitting the cells to respond to exogenous TGF-β1. TGF-β1 cannot inhibit proinflammatory cytokine production in isolated lamina propria mononuclear cells from patients with Crohn disease (CD), but inhibition of Smad7 restores TGF-β1 signaling and enables TGF-β1 to inhibit cytokine production. In inflamed mucosal tissue explants from patients with CD, inhibition of Smad7 also restores p-Smad3 and decreases proinflammatory cytokine production, an effect that is partially blocked by anti–TGF-β1. These results show that Smad7 blockade of TGF-β1 signaling helps maintain the chronic production of proinflammatory cytokines that drives the inflammatory process in IBD and that inhibition of Smad7 enables endogenous TGF-β to downregulate this response.

Authors

Giovanni Monteleone, Andrea Kumberova, Nicholas M. Croft, Catriona McKenzie, Howard W. Steer, Thomas T. MacDonald

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Figure 3

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Stimulation of CD and UC LPMCs with TGF-β1 does not result in enhanced p...
Stimulation of CD and UC LPMCs with TGF-β1 does not result in enhanced p-Smad3. LPMCs isolated from the colon of one normal control, one CD patient, or one UC patient were cultured in the presence or absence of TGF-β1 (1 ng/ml) for 1 hour. Phosphorylated (top blot, p-Smad3) and total (bottom blot) Smad3 were analyzed in proteins extracted from LPMCs as indicated in Figure 2. The example is representative of four separate experiments, in each of which, LPMCs from one normal control, one patient with CD, and one patient with UC were analyzed. In all cases, LPMCs from normal patients showed endogenous p-Smad3 that was enhanced by TGF-β1, whereas in all IBD patients, endogenous p-Smad3 was barely detectable after TGF-β1 stimulation. The bottom panel shows quantitative analysis of active/inactive Smad3 ratio in TGF-β1–stimulated LPMCs from four controls, four patients with CD, and four with UC, as measured by densitometry scanning of Western blots. Values are expressed in arbitrary units (a.u.). Each point represents the value (a.u.) of active/inactive Smad3 ratio in LPMC samples taken from a single subject. Horizontal bars indicate the mean.