Blocking Smad7 restores TGF-β1 signaling in chronic inflammatory bowel disease
Giovanni Monteleone, Andrea Kumberova, Nicholas M. Croft, Catriona McKenzie, Howard W. Steer, Thomas T. MacDonald
Giovanni Monteleone, Andrea Kumberova, Nicholas M. Croft, Catriona McKenzie, Howard W. Steer, Thomas T. MacDonald
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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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Antisense to Smad7 restores TGF-β1 signaling in both CD and UC LPMCs. (a...
Antisense to Smad7 restores TGF-β1 signaling in both CD and UC LPMCs. (a) Treatment of CD and UC LPMCs with a specific Smad7 antisense but not a sense oligonucleotide inhibits Smad7 expression. CD and UC LPMCs were cultured in the absence (U, unstimulated) or presence of a specific Smad7 antisense (AS) or control sense (S) oligonucleotide for 24 hours. Arrows indicate Smad7 detected by a specific polyclonal antibody. The example is representative of three separate experiments analyzing in total LPMCs from five CD or five UC patients. Quantitative data are shown in the right panel as measured by densitometry scanning of Western blots. Values are expressed in arbitrary units (a.u.). Each point represents the value (a.u.) of Smad7 in LPMCs taken from a single subject. Horizontal bars indicate the median value. (b) Inhibition of Smad7 restores the TGF-β1–induced Smad3 phosphorylation in both CD and UC LPMCs. LPMCs were cultured in the absence (U, unstimulated) or presence of a specific Smad7 antisense (AS) or control sense (S) oligonucleotide, and then stimulated with 1 ng/ml TGF-β1 for 1 hour. The right panel shows quantitative analysis of active/inactive Smad3 ratio in LPMC from five patients with CD and five 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 LPMCs taken from a single subject. Horizontal bars indicate the mean.