Role of defective autophagia and the intestinal flora in Crohn disease

The In Vitro Effects of Enzymatic Digested Gliadin on the Functionality of the Autophagy Process

Gliadin, the alcohol-soluble protein fraction of wheat, contains the factor toxic for celiac disease (CD), and its toxicity is not reduced by digestion with gastro-pancreatic enzymes. Importantly, it is proved that an innate immunity to gliadin plays a key role in the development of CD. The immune response induces epithelial stress and reprograms intraepithelial lymphocytes into natural killer (NK)-like cells, leading to enterocyte apoptosis and an increase in epithelium permeability. In this contribution, we have reported that in Caco-2 cells the administration of enzymatically digested gliadin (PT-gliadin) reduced significantly the expression of the autophagy-related marker LC3-II. Furthermore, electron and fluorescent microscope analysis suggested a compromised functionality of the autophagosome apparatus. The rescue of the dysregulated autophagy process, along with a reduction of PT-gliadin toxicity, was obtained with a starvation induction protocol and by 3-methyladenine administration, while rapamycin, a well-known autophagy inducer, did not produce a significant improvement in the clearance of extra- and intra-cellular fluorescent PT-gliadin amount. Altogether, our results highlighted the possible contribution of the autophagy process in the degradation and in the reduction of extra-cellular release of gliadin peptides and suggest novel molecular targets to counteract gliadin-induced toxicity in CD.

Association between physical activity and inflammatory bowel disease risk: A meta-analysis

BACKGROUND

Previous studies of an association between physical activity and inflammatory bowel disease have yielded conflicting results.

AIM

This meta-analysis was conducted to clarify whether there is an association between physical activity and inflammatory bowel disease.

METHODS

The PubMed and Web of Science databases were searched for relevant studies published up to October 2015. Data were extracted and the summary relative risks (RRs) were calculated using a random effects or a fixed-effects model, according to heterogeneity.

RESULTS

Seven studies were included in the analysis. Relative to individuals with low physical activity, those who participated in high physical activity had an RR of 0.63 (95% CI, 0.50-0.79) for developing Crohn's disease. In stratified analyses, a significantly lower risk for Crohn's disease was associated with high physical activity in Europeans only (RR, 0.62; 95% CI, 0.43-0.91); population-based control studies (RR, 0.56; 95% CI, 0.41-0.76); and case-control studies (RR, 0.56; 95% CI, 0.41-0.75). The data of 6 studies were pooled to analyze the effect of physical activity on the risk of ulcerative colitis, and no significant association was found (RR, 0.82; 95% CI, 0.68-1.00).

CONCLUSIONS

The pooled results of observational studies support that physical activity has a protective effect against Crohn's disease.

big bang gene modulates gut immune tolerance in Drosophila

Chronic inflammation of the intestine is detrimental to mammals. Similarly, constant activation of the immune response in the gut by the endogenous flora is suspected to be harmful to Drosophila. Therefore, the innate immune response in the gut of Drosophila melanogaster is tightly balanced to simultaneously prevent infections by pathogenic microorganisms and tolerate the endogenous flora. Here we describe the role of the big bang (bbg) gene, encoding multiple membrane-associated PDZ (PSD-95, Discs-large, ZO-1) domain-containing protein isoforms, in the modulation of the gut immune response. We show that in the adult Drosophila midgut, BBG is present at the level of the septate junctions, on the apical side of the enterocytes. In the absence of BBG, these junctions become loose, enabling the intestinal flora to trigger a constitutive activation of the anterior midgut immune response. This chronic epithelial inflammation leads to a reduced lifespan of bbg mutant flies. Clearing the commensal flora by antibiotics prevents the abnormal activation of the gut immune response and restores a normal lifespan. We now provide genetic evidence that Drosophila septate junctions are part of the gut immune barrier, a function that is evolutionarily conserved in mammals. Collectively, our data suggest that septate junctions are required to maintain the subtle balance between immune tolerance and immune response in the Drosophila gut, which represents a powerful model to study inflammatory bowel diseases.