Intracolonic LPS treatment reduces Treg cell population. Treg cells (5�C10% citation of peripheral CD4+ T cells) are the key factor for peripheral tolerance; they actively inhibit inflammation and are involved in maintaining the immune balance in the normal gut by inhibiting T cell activation and proliferation against bacterial molecules (31). Since our data showed that intracolonic LPS elicited the inflammatory responses in the intestine and, furthermore, studies suggested that intestinal inflammatory diseases are directly associated with excessive T cell activation (6), we next investigated whether T cell activation would be involved in LPS-induced intestinal inflammation. We observed that spleens of mice treated with intracolonic LPS were enlarged compared with those of vehicle-treated mice (Fig.

3A). Given that enhanced LPS level in the colon evolves to intestinal inflammation with upregulated proinflammatory cytokine production and epithelial damage in the small intestine, an enlarged spleen appears to result from those inflammatory responses. Fig. 3. Regulatory T (Treg) cell population was reduced by intracolonic LPS treatment. A: photograph of enlarged spleen from C57BL/6 mice treated with vehicle or LPS for 2 days (left) and spleen weight (right). Values are means �� SD, n = 4/group. *P < ... From these spleens harvested from intracolonically LPS-treated mice, we isolated CD4+ T cells. Using flow cytometry, we found a substantial reduction in the population of immunosuppressive Treg cells (CD4+/CD25+ or CD4+/FoxP3+) in mice intracolonically treated with LPS compared with vehicle-treated mice: 6.

14% and 1.60% in vehicle- and LPS-treated mice, respectively, for CD4+/CD25+ and 6.28% and 1.80% in vehicle- and LPS-treated mice for CD4+/FoxP3+ (Fig. 3B). These data demonstrate that augmented LPS in the colon is able to reduce the population of Treg cells, which are critical for suppressing inflammatory responses, resulting in a predisposition to intestinal inflammation. Carfilzomib LPS-induced intestinal inflammation is dramatically enhanced in IL-10?/? mice. IL-10?/? mice are predisposed to develop spontaneous intestinal inflammation when housed in conventional conditions but do not show the inflammation in a germ-free environment. The inflammation in IL-10?/? mice is, therefore, considered to be commensal microflora-dependent (27), and microbial pattern molecules are able to trigger the development and progress of the intestinal inflammation. Moreover, our data show that intracolonic LPS treatment results in reduced IL-10 production in the small intestine (Fig. 2). Accordingly, we examined the impact of elevated colonic LPS in the absence of IL-10. We administered LPS intracolonically to normal IL-10?/? and IL-10+/+ mice.