Colon epithelial cellular protein induces oral tolerance in the experimental model of colitis by trinitrobenzene sulfonic acid.

Rectal administration of trinitrobenzene sulfonic acid (TNBS) produces chronic colitis in experimental animals. However, the role of epithelial cellular protein(s) in this model is unknown. We examined whether oral tolerance can be induced in this model with colon epithelial cell proteins and whether it is organ specific. Rats were fed five times with extracts of LS-180 human colon cancer cells or HT 1080 human fibroblast cells. Syngeneic normal rat colon or small intestinal extracts were fed to separate groups of rats. After oral feedings, each rat received TNBS by enema. Rats were killed 15 days later, and the following were measured: gross and histologic disease score, weight, thickness, and myeloperoxidase values of colon and serum interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta) levels. Rectal TNBS alone produced severe colitis with a 26% mortality rate. Rats fed LS-180 or rat colon extract before TNBS enema were protected, as evidenced by reductions in mortality rate, disease scores, and myeloperoxidase values. However, rats fed HT 1080 or small intestine extract lacked such protection. To examine the possible mechanism of the oral tolerance, T lymphocytes from mesenteric lymph nodes and spleen of LS-180 extract-fed rats were passively transferred to naive rats, and this was followed by TNBS enema. These rats showed clear protection. Protected animals had low IFN-gamma and high TGF-beta levels. This study demonstrates that cellular protein(s) from human colon epithelial cells, but not from human fibroblasts, can induce oral tolerance in experimental colitis. This oral tolerance is mediated by primed mesenteric and splenic T lymphocytes.

Oral administration of unmodified colonic but not small intestinal antigens protects rats from hapten-induced colitis.

Colonic administration of a hapten, 2,4,6-trinitrobenzene sulphonic acid (TNBS) has been shown to induce colitis in rats. We are using this model to investigate the role of colonic antigens in the immunopathology. In this study, we show that colitis can be suppressed by oral administration of haptenized colonic antigens prior to the TNBS enema. Moreover, our data suggest that haptenization of the colonic antigens is not essential because oral feeding of non haptenized colonic antigens too protects rats from TNBS-induced colitis. Thus, unmodified colonic antigens may be involved in the induction of oral tolerance, and possibly in the pathogenesis in this model of colitis. Further, we show that the protective immunity or oral tolerance induced by non haptenized colonic antigens can be passively transferred to naïve rats by mesenteric T lymphocytes. Interestingly, oral feeding of small intestinal antigens, haptenized and non haptenized, does not protect rats from colitis, suggesting a specific role for colonic antigens. These data underscore the usefulness of this rat model in the identification of pathogenic antigens in colitis and in the development of therapeutic strategies based on oral tolerance.

Effects of genistein and structurally related phytoestrogens on cell cycle kinetics and apoptosis in MDA-MB-468 human breast cancer cells.

We have studied the effects of phytoestrogens (genistein, quercetin, daidzein, biochanin A and kaempferol) on proliferation, cell cycle kinetics, and apoptosis of MDA-MB-468 breast cancer cells. Genistein and quercetin inhibited cell growth with IC50 values of 8.8 and 18.1 muM, respectively, while the other phytoestrogens were less effective. Flow cytometric analysis showed G2/M cell cycle arrest with 25 muM and higher concentrations of genistein. At 100 muM, genistein, quercetin and kaempferol caused accumulation of 70, 60 and 35% of cells, respectively, in G2/M phase by 24 h. In contrast, biochanin A and daidzein were ineffective. APO-BRDU analysis revealed apoptosis with 10 muM genistein (19.5%), reaching 86% at 100 muM. Apoptosis by genistein was confirmed by Hoechst 33342 staining and fluorescence microscopy. With 100 muM quercetin, 47% of the cells were apoptotic, while the other bioflavonoids had little effect. Genistein treatment resulted in a biphasic response on cyclin B1: 70% increase in cyclin B1 level at 25 muM, and 50 and 70% decrease at 50 and 100 muM, respectively. In contrast, the action of quercetin involved an increase in cyclin B1 level. Genistein had no effect on cdc2 level up to 50 muM concentration; however, there was a decrease in the phosphorylated form of the protein at 100 muM. Quercetin had no effect on cdc2 levels. Our results suggest that the action of genistein and quercetin involves G2/M arrest and apoptosis in MDA-MB-468 cells. Biochanin A and daidzein, although structurally related to genistein, did not share this mechanism. Thus, structurally related phytoestrogens have discrete target sites and mechanisms in their growth inhibitory action on breast cancer cells.

A small animal model study of perlite and fir bark dust on guinea pig lungs.

Fir bark (Abies) and perlite (noncrystalline silicate) dusts have been reported to cause pulmonary disease in humans. Guinea pigs were exposed to either fir bark or perlite dust in a special chamber. Severe pathologic changes occurred in the lungs, consisting of lymphoid aggregated and a perivascular inflammatory response. Both dusts caused similar changes although one was vegetable (fir bark) and the other mineral (perlite). Fir bark and perlite dust appeared to be more than just nuisance dusts.