Peng-Yuan Zheng

Disruption of T-cell immunoglobulin and mucin domain molecule (TIM)–1/TIM4 interaction as a therapeutic strategy in a dendritic cell–induced peanut allergy model

BACKGROUND Recent reports indicate that dendritic cell (DC)-derived T-cell immunoglobulin and mucin domain molecule (TIM)-4 plays an important role in the initiation of T(H)2 polarization. This study aims to elucidate the mechanisms of peanut allergy mediated by microbial products and DCs and the relationship between peanut allergy and TIM4. METHODS Mouse bone marrow-derived DCs (BMDCs) were generated and exposed to cholera toxin (CT) or/and peanut extract (PE) for 24 hours and then adoptively transferred to naive mice. After re-exposure to specific antigen PE, the mice were killed; intestinal allergic status was determined. RESULTS Increased expression of TIM4 and costimulatory molecules was detected in BMDCs after concurrent exposure to CT and PE. Adoptively transferred CT/PE-conditioned BMDCs resulted in the increases in serum PE-specific IgE and skewed T(H)2 polarization in the intestine. Oral challenge with specific antigen PE induced mast cell activation in the intestine. Treating with Toll-like receptor 4 small interfering RNA abolished increased expression of TIM4 and costimulatory molecules by BMDCs. Pretreatment with anti-TIM1 or anti-TIM4 antibody abolished PE-specific T(H)2 polarization and allergy in the intestine. CONCLUSION Concurrent exposure to microbial product CT and food antigen PE increases TIM4 expression in DCs and promotes DC maturation, which plays an important role in the initiation of PE-specific T(H)2 polarization and allergy in the intestine. Modulation of TIM4 production in DCs represents a novel therapeutic approach for the treatment of peanut allergy.

Psychological stress induces eosinophils to produce corticotrophin releasing hormone in the intestine

Background and aims: Psychological stress plays an important role in an array of intestinal disorders. Corticotrophin releasing hormone (CRH) is involved in the pathogenic process induced by psychological stress. The peripheral sources of CRH remain to be further understood. This paper aims to identify the sources of CRH in the intestine. Methods and results: Mice were treated with chronic restraint stress. A double-labelling approach was taken to localise CRH expression in immune cells (including dendritic cells, mast cells, lymphocytes, enterochromaffin cells and eosinophils) in the intestine by confocal microscopy and flow cytometry. As CRH was identified in eosinophils, a cell line of eosinophil, EoL-1 cells were treated with an array of putative stress mediators. The results showed that substance P (SP) induced the expression/release of CRH in eosinophils via neurokinin receptor 1 and 2. Co-culturing SP-primed eosinophils with the mast cell line, HMC-1 cells, we found that HMC-1 cells were activated by eosinophil-derived CRH that further induced T84 monolayer barrier dysfunction, which was further confirmed by a mouse model study. Conclusion: Eosinophils express CRH in the jejunum in response to psychological stress. SP and its receptors mediate the effect of stress in the CRH expression in eosinophils. Eosinophil-derived CRH activates mast cells to induce the jejunum epithelial barrier dysfunction.

Bacterial peptidoglycan breaks down intestinal tolerance via mast cell activation: The role of TLR2 and NOD2

Intestinal microbes are believed to be involved in the pathogenesis of inflammatory bowel disease. Microbes and their products are generally well tolerated by intestinal epithelial cells in the intestinal tract of healthy individuals. It is of significance to understand what breaks down the established tolerance leading to intestinal barrier dysfunction and intestinal inflammation. T84 monolayer transported peptidoglycan (PGN) was determined by enzyme‐linked immune assay. Mast cell line HMC‐1 cell activation in response to PGN stimulation was observed with electron microscopy and measurement of histamine release. T84 monolayer barrier function was determined by recording the transepithelial electric resistance (TER) and measuring the permeability in response to PGN‐induced HMC‐1 cell activation. Expression of Toll‐like receptor (TLR) 2 and nucleotide‐binding oligomerization domain (NOD) 2 were determined by immunocytochemistry, real‐time reverse transcription (RT)‐PCR and Western blot. Exposure to PGN alone did not alter TER and permeability of T84 monolayers. T84 monolayers transported PGN from the apical chamber to the basal chamber of transwell system. TLR2 expressed on the surface of HMC‐1 cells. HMC‐1 cells absorbed PGN. HMC‐1 cells released histamine in response to the PGN stimulation, which was blocked by pretreatment with antibodies or small interfering RNA against TLR2 or NOD2. In a co‐culture system, T84 monolayer transported PGN activated HMC‐1 cells and increased the horseradish peroxidase flux. TLR2 mediated the PGN‐absorption in HMC‐1 cells. Blockade of TLR2 or NOD2 abolished PGN‐induced HMC‐1 cell activation and T84 monolayer barrier dysfunction. T84 monolayer transported PGN activates HMC‐1 cells to release chemical mediators to induce T84 monolayer dysfunction that are mediated by TLR2 and NOD2.

Oral Bifidobacterium modulates intestinal immune inflammation in mice with food allergy.

Background and Aims:  It is proposed that probiotics have a therapeutic effect on the treatment of immune disorders. However, the underlying mechanisms require clarification. The present study aimed to evaluate the effect of gavage‐feeding Bifidobacteria on suppression of T helper 2 (Th2) pattern inflammation in the intestines of mice with food allergy.

Investigation into the signal transduction pathway via which heat stress impairs intestinal epithelial barrier function

Background and Aims:  Intact protein absorption is thought to be a causative factor in several intestinal diseases, such as food allergy, celiac disease and inflammatory bowel disease. However, the mechanism remains unclear. The aim of this study was to characterize a novel signal transduction pathway via which heat stress compromises intestinal epithelial barrier function.

Tolerogenic CX3CR1+ B cells suppress food allergy-induced intestinal inflammation in mice.

B lymphocytes are an important cell population of the immune regulation; their role in the regulation of food allergy has not been fully understood yet.

Intestinal epithelial cells express galectin-9 in patients with food allergy that plays a critical role in sustaining allergic status in mouse intestine.

To cite this article: Chen X, Song C‐H, Liu Z‐Q, Feng B‐S, Zheng P‐Y, Li P, In SH, Tang S‐G, Yang P‐C. Intestinal epithelial cells express galectin‐9 in patients with food allergy that plays a critical role in sustaining allergic status in mouse intestine. Allergy 2011; 66: 1038–1046.

Investigation of the Role of Cholera Toxin in Assisting the Initiation of the Antigen-Specific Th2 Response

Skewed Th2 polarization and tissue mastocytosis are the main features of allergy; but how the antigen-specific Th2 polarization initiated remains unclear. The present study shows that cholera toxin (CT) activates mouse bone marrow mast cells (BMMC) to release interleukin (IL)-4. The activation process involved in Toll-like receptor 4, nucleotide oligomerisation domain 1, activate signal transducer and activator of transcription 6 (STAT6), and IL-4. Activated mast cell-derived IL-4 in synergy with co-existing antigen information provided by dendritic cells drives naïve CD4+ T cells to differentiate into antigen-specific Th2 cells. The finding demonstrates that concurrent exposure to microbial products, such as CT, and antigen-loaded dendritic cells plays a critical role in the initiation of antigen-specific Th2 response in the body; this notion is supported by the concurrent adoptive transfer with CT-pulsed BMMCs and antigen-loaded BMDCs that induced antigen-specific Th2 response and hypersensitivity reaction in the intestine.

Probiotics promote endocytic allergen degradation in gut epithelial cells.

BACKGROUND AND AIMS Epithelial barrier dysfunction plays a critical role in the pathogenesis of allergic diseases; the mechanism is to be further understood. The ubiquitin E3 ligase A20 (A20) plays a role in the endocytic protein degradation in the cells. This study aims to elucidate the role of A20 in the maintenance of gut epithelial barrier function. METHODS Gut epithelial cell line, HT-29 cell, was cultured into monolayers to evaluate the barrier function in transwells. RNA interference was employed to knock down the A20 gene in HT-29 cells to test the role of A20 in the maintenance of epithelial barrier function. Probiotic derived proteins were extracted from the culture supernatants using to enhance the expression of A20 in HT-29 cells. RESULTS The results showed that the knockdown of A20 compromised the epithelial barrier function in HT-29 monolayers, mainly increased the intracellular permeability. The fusion of endosome/lysosome was disturbed in the A20-deficient HT-29 cells. Allergens collected from the transwell basal chambers of A20-deficient HT-29 monolayers still conserved functional antigenicity. Treating with probiotic derived proteins increased the expression of A20 in HT-29 cells and promote the barrier function. CONCLUSION A20 plays an important role in the maintenance of epithelial barrier function as shown by HT-29 monolayer. Probiotic derived protein increases the expression of A20 and promote the HT-29 monolayer barrier function.

Stress-Derived Corticotropin Releasing Factor Breaches Epithelial Endotoxin Tolerance.

Background and aims Loss of the endotoxin tolerance of intestinal epithelium contributes to a number of intestinal diseases. The etiology is not clear. Psychological stress is proposed to compromise the intestinal barrier function. The present study aims to elucidate the role of the stress-derived corticotropin releasing factor (CRF) in breaching the established intestinal epithelial endotoxin tolerance. Methods Epithelial cells of HT-29, T84 and MDCK were exposed to lipopolysaccharide to induce the endotoxin tolerance; the cells were then stimulated with CRF. The epithelial barrier function was determined using as indicators of the endotoxin tolerant status. A water-avoid stress mouse model was employed to test the role of CRF in breaching the established endotoxin tolerance in the intestine. Results The established endotoxin tolerance in the epithelial cell monolayers was broken down by a sequent exposure to CRF and LPS manifesting a marked drop of the transepithelial resistance (TER) and an increase in the permeability to a macromolecular tracer, horseradish peroxidase (HRP). The exposure to CRF also increased the expression of Cldn2 in the epithelial cells, which could be mimicked by over expression of TLR4 in epithelial cells. Over expression of Cldn2 resulted in low TER in epithelial monolayers and high permeability to HRP. After treating mice with the 10-day chronic stress, the intestinal epithelial barrier function was markedly compromised, which could be prevented by blocking either CRF, or TLR4, or Cldn2. Conclusions Psychological stress-derived CRF can breach the established endotoxin tolerance in the intestinal mucosa.