The Bcl-2/Bax system and apoptosis in ulcerative colitis.

Background/aims: Ulcerative colitis (UC) constitutes a chronic inflammatory process of the colon of unknown etiology. Current data support a pivotal role of apoptosis in the evolution of pathogenesis of UC. We performed a prospective study in order to determine the role of Bcl-2, Bax and Bcl-x in the apoptotic pathway in UC.

Methodology: We included 23 patients with UC and 11 controls. Histological severity of the disease was assessed according to the Sidney classification system. Patients in the UC group were divided in 2 groups according to histological severity of the disease. The TUNEL method was used for the in situ evaluation of apoptosis. Immunohistochemical staining was used for the detection of Bax, Bcl-2, Bcl-x. For the assessment of cellular proliferation we used the monoclonal antibody Ki67. Appropriate statistical methods were applied.

Results: Overall 77 specimens were assessed; 57 from UC patients and 20 from controls. Bcl-2, Bax and Bcl-x were upregulated in the group of patients with UC compared to controls. Nevertheless, Bax in epithelial cells and Bcl-x in lymphocytes were downregulated in patients with moderate/severe disease (p = 0.029 and 0.04 respectively). A weak correlation between epithelial apoptosis and Bcl-x expression in lymphocytes (r = 0.31, p = 0.02) was found. An even weaker correlation was also noticed between the epithelial component apoptosis and Bax in lymphocytes (r = 0.02, p = 0.07).

Conclusions: Bcl-2/Bax system does not appear to be involved in the induction of apoptosis in UC. Activation of intraepithelial lymphocytes may be associated with epithelial apoptosis or simply represent epiphenomena related to the inflammatory process.