Estrogen altered oral tolerance induction in type II collagen-induced murine arthritis.

BACKGROUND: Estrogen plays an important modulatory role in the immune system, and is concerned with the pathophysiology of autoimmune diseases such as rheumatoid arthritis (RA), although the mechanism has not yet been clarified. Oral tolerance, a form of specific peripheral tolerance, which is recognized as a new therapeutic strategy, is related to the function of gut-associated lymphoid tissue. METHODS: In this study, using collagen-induced arthritis as an animal model of RA, the effects of 17beta-estradiol (E2) on oral tolerance induction were investigated. For induction of oral tolerance, mice were fed 60 microg type II collagen (CII) for 10 consecutive days prior to each CII immunization. Mice in the E2 treatment groups were injected with 5 microg (low dose) or 500 microg (high dose) E2 three times during the induction of oral tolerance. RESULTS: Oral tolerance induction suppressed the occurrence of arthritis, the proliferative response of splenocytes to CII and the specific DTH response. However, E2 treatment abrogated the suppression, which might be connected with a change in function of Peyer's patch (PP) lymphocytes. CONCLUSION: These results suggest that oral tolerance induction might be affected by estrogen treatment through alteration of intestinal immune responses.

Effect of diet-induced obesity on ovalbumin-specific immune response in a murine asthma model.

Some epidemiologic surveys have demonstrated that asthma is more prevalent in obese children and adults. However, the mechanism of association between obesity and asthma has not been fully clarified. This report investigates a murine model for antigen-induced asthma and diet-induced obesity from an immunologic perspective. For the induction of obesity, C57BL/6J mice were fed a high-fat diet supplemented with lard or soybean oil. Mice were then sensitized and challenged with ovalbumin (OVA) to induce allergic lung inflammation. OVA-specific serum immunoglobulin levels were lower in obese mice compared with non-obese control mice. The decline of OVA-specific IgE in the soybean oil group was found to be especially pronounced. However, obese mice with OVA-induced asthma showed a higher sensitivity of antigen-induced T-cell responses, and increased gamma interferon (IFN-gamma) production of splenocytes with phytohemagglutinin (PHA) stimulation. Furthermore, mast cell numbers in the tracheal mucosa were increased in obese mice upon sensitization by OVA. These results suggest that obesity-induced changes in T-cell function may be partly involved in the pathophysiology of asthma in human obesity, rather than Ig E-mediated allergic responses.

Enhanced production of IL-18 in butyrate-treated intestinal epithelium by stimulation of the proximal promoter region.

Expression of IL-18 in intestinal epithelial cells (IEC) has been implicated in Th1 cell-mediated chronic intestinal inflammation and anti-tumor immunity. However, physiological regulatory factors have not been identified. Besides their effects on proliferation and restitution, immunomodulatory functions have been attributed to short chain fatty acids (SCFA). We investigated the effect of SCFA (butyrate, propionate, acetate) on expression of IL-18 in IEC in vitro and in vivo. Expression of IL-18 mRNA and protein in human carcinoma-derived HT-29 and Caco-2 cells was analyzed by reverse transcription-PCR and Western blot. Transcriptional regulation of IL-18 gene expression was determined by transient transfection of wild-type and mutated IL-18 promoter. Further, in vivo expression of IL-18 in the intestine from butyrate-treated and untreated mice was assessed by immunohistochemistry. IL-18 mRNA and the IL-18 protein were expressed in IEC, while IL-18 secretion was not observed. Butyrate and acetate increased intracellular IL-18 content in a time- and dose-dependent fashion. In contrast to proinflammatory stimuli butyrate potently activated the IL-18 promoter, indicating that IL-18 is regulated at the transcriptional level by SCFA. Furthermore, a 108-bp sequence in the proximal region was identified to be essential for IL-18 promoter activation by butyrate. As proof of principle butyrate effects were confirmed in vivo by demonstration of increased IL-18 protein expression in IEC from butyrate-treated mice. In conclusion, SCFA up-regulate IL-18 protein expression in IEC, suggesting a potential regulatory contribution of these luminal constituents to T cell mediated inflammatory and neoplastic intestinal conditions.