Differential cytokine regulation of complement C3, C4, and factor B synthesis in human intestinal epithelial cell line, Caco-2.
In the intestinal tract, the local synthesis of C3 and components of both the classical (C4) and alternative (factor B) C activation pathway has previously been demonstrated in vivo. However, the cellular source of this local C synthesis has not been identified. In this study, we demonstrated the syntheses of C3, C4, and factor B in the human colonic adenocarcinoma cell line Caco-2, which is regarded as a good experimental model of normal human intestinal epithelial cells. The results of metabolic labeling experiments indicated that the intra- and extracellular molecular sizes and subunit structures of Caco-2-derived C3, C4, and factor B were compatible with previously reported values for these components in other cells. The functional activities of C3 and C4 in the supernatants were also demonstrated by hemolytic titration assay. Furthermore, C syntheses in this line were independently upregulated by several human cytokines: C3 synthesis was dose-dependently enhanced by the addition of IL-1 beta or TNF-alpha; C4 synthesis was enhanced by the addition of IL-6 or IFN-gamma in the same manner; and the addition of IL-1 beta or IL-6 also induced a dose-dependent increase in factor B synthesis. These enhancing effects were confirmed to be specific for individual cytokines by experiments using anti-human cytokine antibodies. It is likely that intestinal epithelial cells are local production sites of C3, C4, and factor B, and that local C syntheses in the intestine are independently regulated by several cytokines, derived from monocytes/macrophages and T cells resident in the mucosal microenvironment.
Andoh
A
A
Second Department of Internal Medicine, Shiga University of Medical Science, Otsu, Japan.
Fujiyama
Y
Y
Bamba
T
T
Hosoda
S
S
D000230:Adenocarcinoma / Q000276:immunology; D003110:Colonic Neoplasms / Q000276:immunology; D003176:Complement C3 / Q000096:biosynthesis*; D003181:Complement C4 / Q000096:biosynthesis*; D011415:Complement Factor B / Q000096:biosynthesis*; D016207:Cytokines / Q000494:pharmacology*; D004848:Epithelium / Q000276:immunology; D006461:Hemolysis; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007378:Interleukins / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000276:immunology*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D003176:Complement C3; D003181:Complement C4; D016207:Cytokines; D007378:Interleukins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D011415:Complement Factor B