Inflamed intestinal mucosa features a specific epithelial expression pattern of indoleamine 2,3-dioxygenase.

Indoleamine 2,3-dioxygenase (IDO) catalyzes the first step in the degradation of tryptophan, an essential amino acid. During inflammation IDO can be induced in different cell types resulting in local tryptophan depletion. This inhibits T cell proliferation and may induce apoptosis. High expression of IDO was previously found in inflammatory bowel disease and is thought to represent a mechanism for downregulation of the local immune response. Our aim is to investigate the expression pattern of IDO in normal and inflamed murine and human intestinal mucosa. Immunohistochemical staining for IDO was performed on paraffin sections of colon of two mouse models for colitis and their controls and on paraffin sections of human ileum and colon in normal and two different inflammatory conditions, namely inflammatory bowel disease and diverticulitis. IDO immunohistochemistry showed similar results in murine and human tissue. In normal, as well as in inflamed mucosa, some mononuclear cells, fibroblasts and endothelial cells were positive for IDO. In inflamed mucosa a specific expression pattern of epithelial IDO was found where epithelial cells flanking ulcers or bordering crypt abscesses showed high IDO expression. Moreover, in human intestinal inflammation, IDO was expressed in ulcer associated cell lineage. Since bacterial invasion is more pronounced in erosions and in crypt abscesses and since IDO activity and the resulting local tryptophan depletion can cause growth arrest of several tryptophan-dependent microorganisms, IDO expression in the vicinity of interruptions of the epithelial barrier may point to a role for IDO as a local anti-infectious agent. Furthermore, expression of IDO at the margin of ulcerations and in the reparative ulcer-associated cell lineage suggests involvement of IDO in repair processes.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Genetically Engineered Lactococcus lactis Secreting Murine IL-10 Modulates the Functions of Bone Marrow-Derived Dendritic Cells in the Presence of LPS

Oral delivery of IL-10 by genetically modified Lactococcus lactis (LL-pTmIL10) has been shown to efficiently reduce intestinal inflammation in mice with chronic colitis, but the mechanisms involved have not been elucidated. It has been suggested that IL-10 controls intestinal inflammation by inhibiting microbe-induced activation of dendritic cells. We therefore investigated whether LL-pTmIL10 can modulate the functions of bone marrow-derived dendritic cells (BM-DC) responding to LPS. Incubation of these cells with LL-pTmIL10 or with the control strain LL-pTREX reduced their ability to activate allogeneic T-cell proliferation. However, in contrast to LL-pTREX, LL-pTmIL10 inhibited the LPS-stimulated secretion of MCP-1 by BM-DC and reduced the synergistic up-regulation of IL-12/IL-23p40. In addition, LL-pTmIL10 treatment of LPS-stimulated BM-DC significantly inhibited their capacity to induce strong secretion of IL-17 by CD4+ T cells. Our data suggest that the beneficial effects of LL-pTmIL10 treatment during chronic colitis might involve inhibition of CD4+ Th17 cells and a reduced accumulation of these cells as well as other immune cells at the site of inflammation

Tumoral Environment Triggers Transcript Anomalies in Established Tumors: Induction of Altered Gene Expression and of Aberrant, Truncated and B2 Repeat-Containing Gene Transcripts

In addition to eugenetic changes, cancerous cells exhibit extensive modifications in the expression levels of a variety of genes. The phenotypic switch observed after inoculation of T lymphoma cells into syngenic mice illustrates the active participation of tumoral environment in the induction of an aberrant gene expression pattern. To further substantiate this contribution, we performed polymerase chain reaction (PCR)-based subtraction suppression hybridization (SSH) to identify genes that are differentially expressed in tumor-derived EL4/13.3 cells compared to the same cells isolated from cultures. Besides a number of unknown genes, the subtracted library contained several known genes that have been reported to be expressed at increased levels in tumors and/or to contribute to carcinogenesis. Apart from clones representing translated transcripts, the subtracted library also contained a high number of clones representing B2 repeat elements, viz. short interspersed repetitive elements that are transcribed by RNA polymerase III. Northern blotting confirmed the induction of B2 transcripts in tumor tissue and also revealed induction of chimeric, B2 repeat-containing mRNA. The appearance of chimeric transcripts was accompanied by aberrant, shorter-than-full-length transcripts, specifically from upregulated genes. Accordingly, in addition to altered gene expression, tumoral environmental triggers constitute a potent mechanism to create an epigenetic diversity in cancers by inducing extensive transcript anomalies