Objective: The etiology of ulcerative colitis (UC) remains uncertain. It has been said that in patients with an active phase of UC the levels of the proinflammatory cytokines increased. Paying particular attention to patients with inactive UC, we investigated several cytokines' m-RNA transcripts.
Methods: In 27 patients with UC, the mucosal cytokine expression of m-RNA including IL-8, TNF-alpha, IFN-gamma and IL-6 were examined using the reverse transcription-coupled polymerase chain reaction (RT-PCR) and oligonucleotide hybridization.
Results: 1) The expression ratios of m-RNA of IL-8, IFN-gamma and TNF-alpha in cases with UC (92.6%, 70.4% and 77.8%, respectively) were significantly higher than in normal controls (17.6%, 0.0% and 5.9%, respectively) (p < 0.01). Regarding IL-8 and IFN-gamma, those in UC cases were also significantly higher than in cases with other types of colitis (p < 0.05). 2) No significant difference was noted between active and inactive cases with UC in terms of the expression ratios of m-RNA of IL-8, TNF-alpha and IFN-gamma. 3) Only the expression ratio of IL-6 m-RNA correlated with the macroscopic score according to Matts. In addition, expression of IL-6 m-RNA in the colon tissue was observed in 9 out of 10 cases with other types of colitis (90.0%).
Conclusion: The expression of IL-8, TNF-alpha and IFN-gamma m-RNA increased even in inactive UC, suggesting that these three cytokines play an important role in the pathogenesis of repeated inflammation of UC.