Orally administered TGF-β is biologically active in the intestinal mucosa and enhances oral tolerance

doi:10.1016/j.jaci.2007.05.023

Journal of Allergy and Clinical Immunology

Volume 120, Issue 4, October 2007, Pages 916-923

https://doi.org/10.1016/j.jaci.2007.05.023 Get rights and content

Background

Epidemiologic studies suggest that TGF-β in breast milk provides protection against allergic disease during infancy. However, it is unclear whether orally administered TGF-β, such as TGF-β in human milk, retains and exerts its activity in the intestinal mucosa and can affect immune response (tolerance) to dietary antigens.

Objective

We sought to determine whether orally administered TGF-β is biologically active in intestinal mucosa and affects oral tolerance.

Methods

Activity of orally administered TGF-β in the intestinal mucosa was evaluated by means of in vivo imaging with transgenic mice expressing a Smad-responsive reporter construct (SBE-luc mice), by means of immunohistochemical staining with anti-phosphorylated Smad2 antibody, and by means of real-time RT-PCR analysis of TGF-β and Smad7 mRNA expression. The effects of orally administered TGF-β on oral tolerance induction were assessed in mice tolerized by means of high-dose ovalbumin (OVA) feeding.

Results

The oral administration of TGF-β increased Smad-responsive reporter activity in the intestines of SBE-luc mice and induced Smad2 phosphorylation and TGF-β and Smad7 mRNA expression in the intestines of BALB/c mice. Serum TGF-β levels were also increased after oral administration of TGF-β. BALB/c mice treated orally with OVA and TGF-β showed augmented reduction of OVA-specific IgE and IgG1 antibodies, T-cell reactivity, and immediate-type skin reactions when compared with the mice treated orally with OVA alone.

Conclusions

Orally administered TGF-β retains sufficient biologic activity in intestinal mucosa and enhances oral tolerance.

Clinical implications

Oral administration of TGF-β might become a potential strategy to prevent allergic diseases, such as food allergy.

Section snippets

Reagents

Recombinant human latent TGF-β1 was purchased from R&D, Inc (Minneapolis, Minn). The latent form of TGF-β1 was activated through acidification in 1 mmol/L HCl containing 0.01% BSA, and then it was dissolved in saline before use. The mature (active) human TGF-β1 shows 99% amino acid identity with mature mouse TGF-β1 and is considered to have the same effects as mouse TGF-β1.¹ Chicken OVA was purchased from the Sigma Chemical Co (St Louis, Mo).

Mice

Female 4- to 6-week-old BALB/c mice were purchased

Orally administered TGF-β increases Smad-responsive reporter activity in the intestines of SBE-luc transgenic mice

SBE-luc reporter transgenic mice were used to determine whether orally administered TGF-β retains and exerts its activity in the intestine. These mice allowed the visualization of Smad-dependent TGF-β signaling noninvasively in a temporal and spatial manner that reflects biochemical tissue reporter gene activity.¹²

Untreated SBE-luc mice showed low photon emissions detected in the nose, lower jaw, paws, and tail (Fig 1), thus indicating the constitutively weak activation of Smad signaling in

Discussion

This study shows that TGF-β administered through the oral route retains sufficient biologic activity in the intestinal mucosa and enhances the induction of oral tolerance. Orally administered TGF-β, such as TGF-β in human milk, has not yet been demonstrated to indeed be biologically active in the gastrointestinal mucosal surfaces, where acid inactivation and protease digestion occur. In addition, the ability of orally administered TGF-β to affect oral tolerance has never been demonstrated

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: Supported in part by grants from the Ministry of Education, Culture, Sports, Science, and Technology, Japan, and from the Ministry of Health, Labor, and Welfare, Japan.

: Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.

View full text

Basic and clinical immunologyOrally administered TGF-β is biologically active in the intestinal mucosa and enhances oral tolerance

Background

Objective

Methods

Results

Conclusions

Clinical implications

Section snippets

Reagents

Mice

Orally administered TGF-β increases Smad-responsive reporter activity in the intestines of SBE-luc transgenic mice

Discussion

J Allergy Clin Immunol

J Allergy Clin Immunol

J Biol Chem

J Allergy Clin Immunol

Cytokine

The transforming growth factor-β family

Annu Rev Cell Biol

TGF-β signaling from cell membrane to nucleus through SMAD proteins

Nature

TGF-β signaling in tumor suppression and cancer progression

Nat Genet

Signal transduction by the TGF-β superfamily

Science

Transforming growth factor-β (TGF-β) in human milk

Clin Exp Immunol

Cytokines (IL-1β, IL-6, TNF-α, TGF-β1, and TGF-β2) and prostaglandin E2 in human milk during the first three months postpartum

Pediatr Res

Bioactive molecules in milk and their role in health and disease: the role of transforming growth factor-β

Immunol Cell Biol

Basic and clinical immunology
Orally administered TGF-β is biologically active in the intestinal mucosa and enhances oral tolerance