(Gut 1999;45:856-863)

No abstract

Background and aim: Matrix metalloproteinases (MMPs) have been implicated in tissue remodelling and ulceration in inflammatory bowel disease and coeliac disease. Studies to date have concluded that stromelysin 1 is functionally involved in mucosal degradation. However, there are many other MMPs whose function in the gut is currently unknown. This work had two aims: firstly, to use gene array technology to measure changes in MMP and tissue inhibitor of metalloproteinase (TIMP) expression in a model of T cell mediated injury in the gut, and secondly, to correlate data from gene arrays with that generated by in situ hybridisation. Methods: T cells in explants of human fetal gut were activated with pokeweed mitogen or anti-CD3 plus interleukin 12. Gene array analysis and in situ hybridisation were performed to investigate changes in MMP gene expression. Results: Both gene array analysis and in situ hybridisation indicated marked upregulation of stromelysin 2 and macrophage metalloelastase expression in the explants associated with mucosal destruction. The arrays also confirmed our previous observation that interstitial collagenase (MMP-1), stromelysin 1 (MMP-3), and gelatinase B (MMP-9) are upregulated but there was no change in MMP-2, -7, -8, -9, -11, -13, -14-17, or -19. Following T cell activation, transcripts for TIMPs were reduced. Conclusions: These results show that there is differential upregulation of MMPs during T cell responses in the gut and suggest that further studies on the role of stromelysin 2 and macrophage metalloelastase may show that they have a functional role. In addition, the increase in MMPs and reduction in TIMPs suggest that the protease/antiprotease balance in the mucosa may determine the extent of mucosal degradation.

No abstract

Initially identified as an inhibitor of transforming growth factor (TGF)-β mainly owing to its ability to bind TGF-β receptor type I and abrogate TGF-β-driven signaling, Smad7 can interact with additional intracellular proteins and regulate TGF-β-independent pathways, thus having a key role in the control of neoplastic processes in various organs. Genome-wide association studies have shown that common alleles of Smad7 influence the risk of colorectal cancer (CRC), even though the contribution of Smad7 in colon carcinogenesis is not fully understood. In this study, we assessed the expression and role of Smad7 in human and mouse models of sporadic CRC. We document a significant increase of Smad7 in human CRC relative to the surrounding nontumor tissues and show that silencing of Smad7 inhibits the growth of CRC cell lines both in vitro and in vivo after transplantation into immunodeficient mice. Knockdown of Smad7 results in enhanced phosphorylation of the cyclin-dependent kinase (CDK)2, accumulation of CRC cells in S phase and enhanced cell death. Smad7-deficient CRC cells have lower levels of CDC25A, a phosphatase that dephosphorylates CDK2, and hyperphosphorylated eukaryotic initiation factor 2 (eIF2)α, a negative regulator of CDC25 protein translation. Consistently, knockdown of Smad7 associates with inactivation of eIF2α, lower CDC25A expression and diminished fraction of proliferating cells in human CRC explants, and reduces the number of intestinal tumors in Apcmin/+ mice. Altogether, these data support a role for Smad7 in sustaining colon tumorigenesis.

Innate lymphoid cells (ILCs) play an important role in regulating immune responses at mucosal surfaces. The transcription factor T-bet is crucial for the function of ILC1s and NCR + ILC3s and constitutive deletion of T-bet prevents the development of these subsets. Lack of T-bet in the absence of an adaptive immune system causes microbiota-dependent colitis to occur due to aberrant ILC3 responses. Thus, T-bet expression in the innate immune system has been considered to dampen pathogenic immune responses. Here, we show that T-bet plays an unexpected role in negatively regulating innate type 2 responses, in the context of an otherwise intact immune system. Selective loss of T-bet in ILCs leads to the expansion and increased activity of ILC2s, which has a functionally important impact on mucosal immunity, including enhanced protection from Trichinella spiralis infection and inflammatory colitis. Mechanistically, we show that T-bet controls the intestinal ILC pool through regulation of IL-7 receptor signalling. These data demonstrate that T-bet expression in ILCs acts as the key transcriptional checkpoint in regulating pathogenic vs. protective mucosal immune responses, which has significant implications for the understanding of the pathogenesis of inflammatory bowel diseases and intestinal infections.

SUMMARY Background: Recent studies have shown both interleukin 2 (IL‐2) and interferon gamma (IFN) to be elevated in patients with active Crohn's disease compared to ulcerative colitis or non‐inflammatory bowel disease controls. However the effect of treatment on these lymphokines has not been studied. Patients and methods: Using a reverse haemolytic plaque assay the percentage of lymphokine‐secreting cells was determined in the intestinal mucosa of children with Crohn's disease before and after 8 weeks of treatment with either enteral nutrition, cyclosporin or steroids. Results: Before treatment, a high percentage of cells isolated from mucosal biopsies secreted IL‐2 or interferon‐gamma. Eight weeks’treatment with the immunosuppressive agents cyclosporin, or with corticosteroids, produced a significant reduction in the percentage of IL‐2 secreting cells, although only for the former was there also a reduction in interferon‐gamma secreting cells. Enteral nutrition however, produced a reduction in lymphokine‐secreting cells equivalent to cyclosporin and produced the best histological and clinical improvement. Conclusion: Enteral nutrition and cyclosporin can down‐regulate lymphokine secretion in the gut in Crohn's disease.

SummaryCrohn's disease and ulcerative colitis are inflammatory bowel diseases (IBD) characterized by chronic relapsing mucosal inflammation. Tumour necrosis factor (TNF)-a, a known agonist of the mitogen-activated protein kinase (MAPK) pathway, is a key cytokine in this process. We aimed first to determine whether p38 MAPK is activated in IBD inflamed mucosa, and then studied the effect of four different p38a inhibitory compounds on MAPK phosphorylation and secretion of proinflammatory cytokines by IBD lamina propria mononuclear cells (LPMCs) and organ culture biopsies. In vivo phospho-p38a and p38a expression was evaluated by immunoblotting on intestinal biopsies from inflamed areas of patients affected by Crohn's disease and ulcerative colitis, and from normal mucosa of sex-and age-matched control subjects. Both mucosal biopsies and isolated LPMCs were incubated with four different p38a selective inhibitory drugs. TNF-a, interleukin (IL)-1b and IL-6 were measured in the organ and cell culture supernatants by enzyme-linked immunosorbent assay. We found higher levels of phosphop38a in the inflamed mucosa of IBD patients in comparison to controls. All the p38a inhibitory drugs inhibited p38a phosphorylation and secretion of TNF-a, IL-1b and IL-6 from IBD LPMCs and biopsies. Activated p38a MAPK is up-regulated in the inflamed mucosa of patients with IBD. Additionally, all the p38a selective inhibitory drugs significantly down-regulated the activation of the MAPK pathway and the secretion of proinflammatory cytokines.