Primary sclerosing cholangitis (PSC), a chronic inflammatory liver disease characterized by progressive bile duct destruction, develops as an extra-intestinal complication of inflammatory bowel disease (IBD) (Chapman, R.W. 1991. Gut. 32:1433–1435). However, the liver and bowel inflammation are rarely concomitant, and PSC can develop in patients whose colons have been removed previously. We hypothesized that PSC is mediated by long-lived memory T cells originally activated in the gut, but able to mediate extra-intestinal inflammation in the absence of active IBD (Grant, A.J., P.F. Lalor, M. Salmi, S. Jalkanen, and D.H. Adams. 2002. Lancet. 359:150–157). In support of this, we show that liver-infiltrating lymphocytes in PSC include mucosal T cells recruited to the liver by aberrant expression of the gut-specific chemokine CCL25 that activates α4β7 binding to mucosal addressin cell adhesion molecule 1 on the hepatic endothelium. This is the first demonstration in humans that T cells activated in the gut can be recruited to an extra-intestinal site of disease and provides a paradigm to explain the pathogenesis of extra-intestinal complications of IBD.

Mucosal tissues require constant immune surveillance to clear harmful pathogens while maintaining tolerance to self Ags. Regulatory T cells (Tregs) play a central role in this process and expression of αEβ7 has been reported to define a subset of Tregs with tropism for inflamed tissues. However, the signals responsible for recruiting Tregs to epithelial surfaces are poorly understood. We have isolated a subset of CCR10-expressing CD25+CD4+Foxp3+ Tregs with potent anti-inflammatory properties from chronically inflamed human liver. The CCR10+ Tregs were detected around bile ducts that expressed increased levels of the CCR10 ligand CCL28. CCL28 was secreted by primary human cholangiocytes in vitro in response to LPS, IL-1β, or bile acids. Exposure of CCR10+ Tregs to CCL28 in vitro stimulated migration and adhesion to mucosal addressin cell adhesion molecule-1 and VCAM-1. Liver-derived CCR10+ Tregs expressed low levels of CCR7 but high levels of CXCR3, a chemokine receptor associated with infiltration into inflamed tissue and contained a subset of αEβ7+ cells. We propose that CXCR3 promotes the recruitment of Tregs to inflamed tissues and CCR10 allows them to respond to CCL28 secreted by epithelial cells resulting in the accumulation of CCR10+ Tregs at mucosal surfaces.

Purpose:We hypothesized that deregulated corepressor actions, with associated histone deacetylation activity, epigenetically suppressed vitamin D receptor (VDR) responsiveness and drives resistance towards 1a,25-dihydroxyvitamin D 3 . Experimental Design: Profiling, transcriptional, and proliferation assays were undertaken in 1a,25(OH) 2 D 3 -sensitive MCF-12A nonmalignant breast epithelial cells, a panel of breast cancer cell lines, and a cohort of primary breast cancer tumors (n = 21). Results: Elevated NCoR1 mRNA levels correlated with suppressed regulation of VDR target genes and the ability of cells to undergo arrest in G 1 of the cell cycle. A similar increased ratio of corepressor mRNA to VDR occurred in matched primary tumor and normal cells, noticeably in estrogen receptor a^negative (n = 7) tumors. 1a,25(OH) 2 D 3 resistance in cancer cell lines was targeted by cotreatments with either 1a,25(OH) 2 D 3 or a metabolically stable analogue (RO-26-2198) in combination with either trichostatin A (TSA; histone deacetylation inhibitor) or 5-aza-2V-deoxycytidine (DNA methyltransferase inhibitor). Combinations of vitamin D 3 compounds with TSA restored VDR antiproliferative signaling (target gene regulation, cell cycle arrest, and antiproliferative effects in liquid culture) to levels which were indistinguishable from MCF-12A cells. Conclusions: Increased NCoR1 mRNA is a novel molecular lesion in breast cancer cells, which acts to suppress responsiveness of VDR target genes, resulting in 1a,25(OH) 2 D 3 resistance and seems to be particularly associated with estrogen receptor negativity.This lesion provides a novel molecular diagnostic and can be targeted by combinations of vitamin D 3 compounds and low doses of TSA.The nuclear receptor superfamily regulates diverse signals that are central to the formation and homeostasis of the mammary gland. The postgenomic description of the superfamily conjoined with profiling approaches (1) reveals that breast myoepithelial and epithelial cells express a rich cohort of nuclear receptors, many of which display overt nutrient-sensing capacity for micronutrients and macronutrients alongside the estrogen receptors (ERa and ERh; refs. 2 -6).Several of the diet-sensing nuclear receptors, such as the VDR, preferentially form heterodimers with retinoid X receptors whereas the ERs preferentially heterodimerize with one another. For the nuclear receptors to regulate transcriptional programs, these dimers must be contained as subunits in either large gene coactivator or corepressor complexes. In the absence of ligand, receptors exist in an apo state as part of large complexes (f2.0 MDa; ref. 7), associated with corepressors (e.g., NCoR1, NCoR2/SMRT, and TRIP15/Alien), and bound to response element sequences. These complexes actively recruit a range of enzymes that posttranslationally modify histone tails (e.g., histone deacetylases and methyltransferases) and thereby maintain a locally closed chromatin structure around response element sequences (8). Ligand binding induces a...

Inflammatory bowel disease is characterized by the recruitment of lymphocytes to the gut via mucosal vessels. Chemokines are believed to trigger alpha(4)beta(1)- and alpha(4)beta(7)-integrin-mediated adhesion to vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) on mucosal vessels, although the contribution of each pathway and the chemokines involved are not well characterized. These interactions occur under conditions of hemodynamic shear, which is critical in determining how lymphocytes integrate chemokine signals to promote transmigration. To define the role of specific chemokines in mediating lymphocyte adhesion to VCAM-1 and MAdCAM-1, we studied the ability of immobilized chemokines to activate adhesion of human lymphocytes in a flow-based adhesion assay. Adhesion to immobilized MAdCAM-1 was alpha(4)beta(7) dependent, with no contribution from alpha(4)beta(1), whereas alpha(4)beta(1) mediated rolling and static adhesion on VCAM-1. Immobilized CC-chemokine ligand (CCL) 25 and CCL28 were both able to trigger alpha(4)beta(7)-dependent lymphocyte arrest on MAdCAM-1 under shear, highlighting a potential role for these chemokines in the arrest of lymphocytes on postcapillary venules in the gut. Neither had any effect on adhesion to VCAM-1, suggesting that they selectively trigger alpha(4)beta(7)-mediated adhesion. Immobilized CCL21, CCL25, CCL28, and CXC-chemokine ligand (CXCL) 12 all converted rolling adhesion to static arrest on MAdCAM-1 by activating lymphocyte integrins, but only CCL21 and CXCL12 also triggered a motile phenotype characterized by lamelipodia and uropod formation. Thus alpha(4)beta(1)/VCAM-1 and alpha(4)beta(7)/MAdCAM-1 operate independently to support lymphocyte adhesion from flow, and chemokines may act in concert with one chemokine triggering integrin-mediated arrest and a second chemokine promoting motility and transendothelial migration.

-Inflammatory bowel disease is associated with extra-intestinal manifestations which occur either at the same time as flares of bowel inflammation (skin and eye disease) or run a course that is independent to inflammation in the bowel (liver and some joint syndromes). It has been suggested that the skin and eye complications occur as a consequence of the recruitment of activated effector cells released from the gut into the circulation to extra-intestinal site where they cause acute damage. However, this does not explain how patients can develop primary sclerosing cholangitis many years after having their colon removed for colitis. We propose that longlived populations of memory lymphocytes arise as a consequence of bowel inflammation and that these cells express homing receptors that direct their subsequent migration not only to the gut but also to the liver. These long-lived cells may recirculate to the liver for many years and, in the absence of a local activating stimulus, will not cause damage. However, if they are subsequently activated in the liver this will lead to the development of inflammation and tissue damage which promotes the recruitment of more mucosal lymphocytes resulting in persistent inflammation and disease. The recent findings that MAdCAM-1 and CCL25, previously thought to be restricted to the gut, are up-regulated in the liver during inflammatory liver diseases that complicate IBD support the concept that common mechanisms control lymphocyte recruitment to the inflamed liver and gut.