Disruption of the pro-inflammatory, anti-inflammatory cytokines and tight junction proteins expression, associated with changes of the composition of the gut microbiota in patients with irritable bowel syndrome

Abstract

Background: Irritable bowel syndrome (IBS) is a pathologic condition characterized by changes in gut microbiome composition, low-grade inflammation, and disruption of intestinal wall permeability. The interaction between the gut microbiome and the disease manifestation remains unclear. The changing of tight junction proteins and cytokines expression throughout the gastrointestinal tract in IBS patients has not been studied yet.

Aim of the study: To assess the changes of gut microbiome composition, tight junction proteins, and cytokines expression of intestinal mucosa from the duodenum to the distal part of the colon in IBS patients and healthy volunteers.

Methods: In 31 IBS patients (16 patients with IBS-D; 15 patients with IBS-C) and 10 healthy volunteers the expression of CLD-2, CLD-3, CLD-5, IL-2, IL-10, and TNF-α in mucosal biopsy specimens was determined by morphological and immune-histochemical methods. The qualitative and quantitative composition of the intestinal microbiota was assessed based on 16S rRNA gene sequencing in both groups of patients.

Results: The expression of IL-2 and TNF-α was significantly increased in IBS patients compared with the controls (p<0.001), with a gradual increase from the duodenum to the sigmoid colon. The expression of IL-10, CLD-3, and CLD-5 in mucosal biopsy specimens of these patients was lower than in the control group (p<0.001). Increased ratios of Bacteroidetes and decreased ratios of Firmicutes were noted in IBS patients compared to healthy volunteers (p<0.05).

Conclusion: IBS patients have impaired gut permeability and persisting low-grade inflammation throughout the gastrointestinal tract. Changes in the gut microbiota may support or exacerbate these changes.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. The expression of TNF-α in the mucosal biopsy of IBS patients and healthy control in different parts of the gastrointestinal tract.

The expression of TNF-α gradually increased from duodenum to sigmoid colon compared to the control group. Mean values ± SD are shown. The statistical significance of the observed differences between IBS patients and healthy individuals was evaluated using Mann-Whitney U test (p-value

Fig 2. The expression of IL-2 in the mucosal biopsy of IBS patients and healthy control in different parts of the gastrointestinal tract.

The expression of IL-2 gradually increased from duodenum to sigmoid colon compared to the control group. Mean values ± SD are shown. The statistical significance of the observed differences between IBS patients and healthy individuals was evaluated using Mann-Whitney U test (p-value The expression of anti-inflammatory cytokines in the mucosal biopsy specimens of IBS patients was significantly lower than in the control group.

Fig 3. The expression of IL-10 in the mucosal biopsy of IBS patients and healthy control in different parts of the gastrointestinal tract.

The expression of IL-10 was significantly lower in IBS group compared to the control group throughout the gastrointestinal tract. Mean values ± SD are shown. The statistical significance of the observed differences between IBS patients and healthy individuals was evaluated using Mann-Whitney U test (p-value

Fig 4. The expression of CLD-3 in mucosal biopsy of IBS patients and healthy control in different parts of the gastrointestinal tract.

The expression of CLD-3 was significantly lower in IBS group compared to the control group throughout the gastrointestinal tract. Mean values ± SD are shown. The statistical significance of the observed differences between IBS patients and healthy individuals was evaluated using Mann-Whitney U test (p-value

Fig 5. The expression of CLD-5 in the mucosal biopsy of IBS patients and healthy control in different parts of the gastrointestinal tract.

The expression of CLD-5 was significantly lower in IBS group compared to the control group throughout the intestine. Mean value ± SD are shown. The statistical significance of the observed differences between IBS patients and healthy individuals was evaluated using Mann-Whitney U test (p-value

Fig 6. The gradient of cytokines and tight junction proteins expression in IBS patients and in control group.

Positive gradient of expression of TNF- α and IL-2 in IBS group. *stands for TNF-α data, where p

Fig 7. Relative abundance of bacterial phyla in the cohorts of IBS patients and healthy individuals.

Solid bars correspond to median values; semi-transparent rectangles correspond to 95% confidence interval. The vertical axis is log-transformed. Asterisks (*) indicate cases for which p

Fig 8. Relative abundance of bacterial families, for which statistically significant differences between the cohorts of IBS patients and healthy individuals (GreenGenes nomenclature).

The degree of statistical significance is indicated with asterisks (*p Firmicute families that increase their abundance in IBS patients, there are a general decrease in the proportion of Firmicutes in IBS patients, mainly due to a significant drop in the abundance of the dominant Lachnospiraceae family.

Fig 9. The relative abundance of bacterial genera in the cohorts of IBS patients and healthy individuals.

The degree of statistical significance is indicated with asterisks (*p

Fig 10. Relative abundance of bacterial genera, which may include butyrate producers, in the cohorts of IBS patients and healthy individuals.

The degree of statistical significance is indicated with asterisks (*p