Abstract: Objective:To investigate the cellular localization, expression and activation of STAT3 in colonic mucosa of patients with UC and analyze the correlation between STAT3 expression and clinical and endoscopic activity. Methods: 47 UC patients and 13 normal controls were collected. The patients were divided into different groups according to endoscopic activity and clinical activity. Expression of STAT3 and phosphorylated STAT3 proteins were assayed by Western blotting while STAT3 mRNA was assayed by RT-PCR in extracts of endoscopic colonic biopsies. In addition, their cellular localization was determined by immunohistochemistry (IHC). Results: ⑴ IHC revealed that in the mucosa of UC patients, STAT3 was detected mainly in the cytoplasm of diffused distribution mononuclear cells in lamina propria and pSTAT3 was detected both in the nucleus and cytoplasm of lamina propria mononuclear cells while mainly in the nucleus. In patients with UC colonic inflammation, both STAT3 and pSTAT3 were expressed in a great quantity of infiltrative mononuclear cells with stronger staining density in comparison with controls. ⑵ Using western blotting, the expression of STAT3 and pSTAT3 proteins in UC patients was higer than normal controls and both their expression was increased gradually along with the aggravation of the disease. ⑶ RT-PCR showed that the expression of STAT3 mRNA in UC patients was significantly upregulated along with the aggravation of severity of the disease. Conclusions: In colonic mucosa of UC patients, both the expression and activation of STAT3 were gradually increased and well correlated to the clinical and endoscopic activity of the disease, which implicating that STAT3 may reflect the severity of UC in some extent.

Key words: ulcerative colitis, STAT3, p-STAT3