Increased Expression of Toll-Like Receptors 4, 5, and 9 in Small Bowel Mucosa from Patients with Irritable Bowel Syndrome

The aim of our study was to compare patients with irritable bowel syndrome (IBS) and healthy controls regarding the expression of toll-like receptors 2, 4, 5, and 9 (TLR2, TLR4, TLR5, and TLR9), the primary mucosal receptors of bacterial components, in small and large bowel mucosa. Methods. We analysed biopsies from jejunum and sigmoid colon of 22 patients (17 females) with IBS aged 18-66 (median: 39) years and 14 healthy volunteers (12 females) aged 22-61 (median: 42) years. Eight patients had constipation-predominant IBS (C-IBS), 7 had diarrhoea-predominant IBS (D-IBS), and 7 had IBS without predominance of constipation or diarrhoea. We analysed mRNA levels for TLRs using quantitative PCR and distribution of TLRs in mucosa using immunohistochemistry. Results. We found increased mRNA expression of TLR4 (mean fold change 1.85 +/- 0.31 versus 1.0 +/- 0.20;p< 0.05), TLR5 (1.96 +/- 0.36 versus 1.0 +/- 0.20;p< 0.05) and TLR9 (2.00 +/- 0.24 versus 1.0 +/- 0.25;p< 0.01) but not of TLR2 in the small bowel mucosa from patients with IBS compared to the controls. There was no significant difference in mRNA levels for TLRs in colon mucosa between patients and controls. Conclusion. Upregulation of TLR4, TLR5, and TLR9 suggests the involvement of bacteria or dysregulation of the immune response to commensal flora in small bowel mucosa in IBS patients.