Differential expression of toll-like receptor 3 and 5 in ileal pouch mucosa of ulcerative colitis patients

Background and aims The pathogenesis of pouchitis, major complication after restorative proctocolectomy, and ileal J pouch- anal anastomosis (IPAA) in patients with ulcerative colitis (UC) is still unclear. Changes in intraluminal bacterial colonization and correlated changes of pouch mucosa are thought to play an important role. Toll-like receptors (TLRs) as part of the innate immune system are capable of recognizing bacterial antigens. Their activation can lead to secretion of proinflammatory mediators. In this study, TLR2, 3, 4, and 5 expression profiles in the pouch mucosa of patients with UC and IPAA were analyzed and correlated with pouchitis. Materials and methods Clinical symptoms, endoscopy, and histology were assessed in 35 patients using the Heidelberg Pouchitis Activity Score to classify patients as either having pouchitis or not. TLR mRNA expression in normal ileal mucosa and pouch mucosa was investigated by performing semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The results of RT-PCR were associated with the pouchitis score. Results In the analysis of all patients, TLR3 expression was decreased significantly whereas TLR5 expression was increased significantly in pouch mucosa compared to normal ileal mucosa (p-values 0.0076 and 0.016, respectively). A more detailed analysis upon dividing the patients into patients with and without pouchitis showed decreased TLR3 expression in the pouch mucosa only of patients without pouchitis (p-value= 0.0067). TLR5 expression was increased in the pouch mucosa only of patients with pouchitis (p-value= 0.023). No differences in TLR2 and 4 expression were found in either group. Conclusion Differential expression of TLR3 and 5 suggests bacterial involvement in the pathogenesis of pouchitis in patients with UC.