Kazuaki Takeuchi

Cytokine-stimulated release of decay-accelerating factor (DAF; CD55) from HT-29 human intestinal epithelial cells

Expression of DAF (CD55) is enhanced on colonic epithelial cells of patients with ulcerative colitis (UC), and stool DAF concentrations are increased in patients with active disease. Cytokines are known to modulate DAF expression in various human cells, and lesions of UC reveal altered profiles of cytokine production. In this study, we evaluate the effects of various cytokines, IL‐1β, IL‐2, IL‐4, IL‐6, IL‐8, IL‐10, and interferon‐gamma (IFN‐γ), on the synthesis and kinetics of DAF protein in HT‐29 human intestinal epithelial cells. Using flow cytometry and an ELISA, we found that HT‐29 cells constitutively express DAF on the cell surface and spontaneously release DAF into the culture supernatant under standard culture conditions. When the culture supernatant was centrifuged at 100 000 g, nearly a half of DAF was precipitated, indicating that one half of the released DAF was present as a membrane‐bound form and the other half as a soluble form. Analysis of the culture supernatant of biotin surface‐labelled HT‐29 cells suggested that the soluble form DAF was derived by secretion from within the cell or by cleavage from the cell surface. Among the cytokines, IL‐4 markedly, and IL‐1β moderately, enhanced the expression and the release of DAF. Actinomycin D, cycloheximide, and brefeldin A inhibited the increase in DAF release induced by IL‐4 and IL‐1β stimulation. These results suggest that DAF is released from intestinal epithelial cells in response to cytokine stimulation and that IL‐4 and IL‐1β are possible cytokines involved in DAF release into the colonic lumen of patients with UC.

Polymorphic expression of decay-accelerating factor in human colorectal cancer

Background: We have previously shown that expression of decay‐accelerating factor (DAF), a complement regulatory protein, is enhanced immunohistochemically on the luminal surface of cancer glands in human colorectal cancer and is detected in stool specimens of patients with colorectal cancer. The amount of DAF present in the stools might be influenced by the stability of DAF on the cell surface which is regulated by biochemical properties such as glycosylation of the protein. In the present study, to help elucidate the mechanism for the release of DAF from human colorectal cancers, we biochemically analyzed DAF expression by western and northern blotting by using surgically resected specimens of colorectal cancers.

Decay-accelerating factor (DAF) in stool specimens as a marker of disease activity in patients with ulcerative colitis (UC)

Colonic epithelial cells of patients with UC express DAF in relation to the severity of mucosal inflammation. The aim of this study was to determine whether this factor in stool could be used as a marker of disease activity in UC patients. Stool DAF was measured by use of an immunoassay in 181 stool specimens obtained from 55 patients with UC of various levels of disease activity. Stool DAF concentrations in patients whose UC was active (0.0–785.6 ng/g stool; median 47.1 ng/g; n = 115) were significantly higher than concentrations in patients whose disease was inactive (0.0–48.6 ng/g; median 0.0 ng/g; n = 66) (P < 0.0001). Values in active UC patients also were higher than those in control patients with diarrhoea (0.0–30.0 ng/g; median 0.0 ng/g; n = 26) (P < 0.0001) and in control subjects without apparent colorectal disease (0–20.4 ng/g; median 0.0 ng/g; n = 44) (P < 0.0001). The elevated levels of stool DAF obtained from UC patients in relapse declined markedly in specimens collected after the disease went into remission following medical therapy. Stool DAF levels correlated with the severity of endoscopic and histological findings and the degree of DAF expression on the colonic epithelia. Our results suggest that the measurement of stool DAF is useful as a non‐invasive means of monitoring intestinal disease activity in patients with UC.