Mechanism for regulation of mucin secretion from intestinal goblet cells in parasitic infection

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We examined methods of measuring mucin to study on the regulatory mechanism of mucin production or secretion from intestinal goblet cells. We developed a method to measure intestinal mucin using specific lectin binding to mucin. Amount of intestinal mucin in N.brasiliensis (Nb)-infected C57BL/6 mice was peaked on day 7 post-infection and then decreased to normal level on day 10. The change of intestinal mucin level corresponded well to change of intestinal goblet ceilnumber and worm expulsion. Although the intestinal mucin increased slowly in Nb infected-athymic nude mice, maximum amount of the mucin was almost similar to that of euthymic mice. In Nb-infected IL-4 gene knockout mice, intestinal mucin level was not changed from that in control mice. Intraperitoneal injection of Nb antigens, anti-CD4 antibodies or cyclophosphamide did not change intestinal mucin in Nb-infected mice. So far, no method have been found to change intestinal mucin level in Nb-infected mice in vivo. Separated intestinal cells from uninfected mice, when cultured in vitro with Con A, secreted more mucin in the culture medium. We failed to find a RT-PCR condition for detecting mRNA of mucin core protein in rat or mouse intestine. However, we could detected the mRNA of human mucin core protein (MUC2) by RT-PCR in the mucin producing human colon carcinoma cell line, LS174T.Addition of recombinant human TNF-alpha increased MUC2 mRNA expression in LS174T cells. Culture of LS174T cells with recombinant human IL-13 stimulated mucin production without increasing cell number. Furthermore, IL- 13 receptor was detected on LS 174T cells by RT-PCR.The experiment using LS 174T cells will facilitate the studies on regulation mechanism of mucin production.