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T T MacDonald

Publications and source records attributed to T T MacDonald.

At least 37 records · Page 2Linked to original sources
PubMed2001

Blocking Smad7 restores TGF-beta1 signaling in chronic inflammatory bowel disease.

TGF-beta1 functions as a negative regulator of T cell immune responses, signaling to target cells using the Smad family of proteins. We show here that Smad7, an inhibitor of TGF-beta1 signaling, is overexpressed in inflammatory bowel disease (IBD) mucosa and purified mucosal T cells. Both whole tissue and isolated cells exhibit defective signaling through this pathway, as measured by phospho-Smad3 immunoreactivity. Specific antisense oligonucleotides for Smad7 reduce Smad7 protein expression in cells isolated from patients with IBD, permitting the cells to respond to exogenous TGF-beta1. TGF-beta1 cannot inhibit proinflammatory cytokine production in isolated lamina propria mononuclear cells from patients with Crohn disease (CD), but inhibition of Smad7 restores TGF-beta1 signaling and enables TGF-beta1 to inhibit cytokine production. In inflamed mucosal tissue explants from patients with CD, inhibition of Smad7 also restores p-Smad3 and decreases proinflammatory cytokine production, an effect that is partially blocked by anti-TGF-beta1. These results show that Smad7 blockade of TGF-beta1 signaling helps maintain the chronic production of proinflammatory cytokines that drives the inflammatory process in IBD and that inhibition of Smad7 enables endogenous TGF-beta to downregulate this response.

Activin Receptors, Type I↗
PubMed2000

Human Peyer's patch T cells are sensitized to dietary antigen and display a Th cell type 1 cytokine profile.

Animal studies have demonstrated that feeding Ags induces regulatory (Th2, Th3) cells in Peyer's patches (PP), which migrate to the periphery and produce immunomodulatory cytokines such as IL-4, IL-10, or TGF-beta. In this work we have attempted to extend this paradigm to man by analyzing the response of human PP T cells to in vitro challenge with the common dietary Ag beta-lactoglobulin (betalg) of cow's milk. PP T cells stimulated with betalg showed enhanced proliferation compared with blood T cells from the same patient. Increased expression of CD25 and the Th1-associated chemokine receptor CCR5 was also seen on CD4(+) and CD8(+) PP T cells, but not blood T cells, stimulated with betalg. By enzyme-linked immunospot assay and RT-PCR, the PP T cell recall response to betalg and casein was dominated by IFN-gamma, with negligible IL-4, IL-5, IL-10, or TGF-beta. To help explain the PP T cell response to betalg, we examined IL-12 expression. Both IL-12p40 and -p35 transcripts were abundantly expressed in PP, but not in adjacent normal ileal mucosa. Immunoreactive IL-12p40-containing cells were present below the PP dome epithelium. Furthermore, in culture, PP, but not paired PBMC, spontaneously released IL-12p70. These results suggest that the human response to oral Ags in the gut may be different from that in rodents.

Adolescent↗
PubMed2000

Ligation of alpha4ss1 integrin on human intestinal mucosal mesenchymal cells selectively Up-regulates membrane type-1 matrix metalloproteinase and confers a migratory phenotype.

Human intestinal lamina propria mesenchymal cells show high surface expression of the alpha4ss1 integrin. Ligation of alpha4ss1 on mesenchymal cell lines with an activating monoclonal anti-alpha4 antibody or vascular cell adhesion molecule-immunoglobulin (VCAM-IgG) leads to the appearance of activated forms of gelatinase A in culture supernatants, and the de novo expression of activated membrane type-1-matrix metalloproteinase (MT1-MMP). In functional assays, signaling through alpha4ss1 results in an increased capacity of mesenchymal cells to migrate through an artificial extracellular matrix, an effect inhibitable by excess tissue inhibitor of metalloproteinase-2. In organ cultures of human intestine, VCAM-IgG also up-regulates MT1-MMP, and in mucosal ulcers of inflammatory bowel disease patients, MT1-MMP transcripts are abundant, coincident with expression of VCAM-1 on cells at the ulcer margin. Collectively these results suggest that alpha4ss1-induced up-regulation of MT1-MMP may be a crucial factor in the migration of mesenchymal cells into ulcer beds during restitution of diseased gut mucosa.

Antibodies↗
PubMed2000

Mucosal healing and a fall in mucosal pro-inflammatory cytokine mRNA induced by a specific oral polymeric diet in paediatric Crohn's disease.

BACKGROUND: Although enteral nutrition is a recognized form of treatment for intestinal Crohn's disease, there are persisting problems with feed palatability and only limited data as to its mode of action. AIM: To assess the effects of a specific oral polymeric diet (CT3211; Nestle, Vevey, Switzerland), which is rich in transforming growth factor beta2, on the mucosal inflammatory process. METHODS: Twenty-nine consecutive children with active intestinal Crohn's disease were treated with CT3211 as the sole source of nutrition for 8 weeks. Patients were assessed clinically, and endoscopically, whilst cytokine mRNA was measured in mucosal biopsies before and after treatment by quantitative reverse transcriptase polymerase chain reaction. RESULTS: After 8 weeks 79% of children were in complete clinical remission. Macroscopic and histological healing in the terminal ileum and colon was associated with a decline in ileal and colonic interleukin-1beta mRNA (pre-treatment to post-treatment ratio 0.008 and 0.06: P < 0.001, P = 0.006). In the ileum there was also a fall in interferon gamma mRNA (ratio 0.15, P < 0.001) with a rise in transforming growth factor beta1 mRNA (ratio 10, P = 0.04), whilst in the colon interleukin-8 mRNA fell with treatment (ratio 0.06, P < 0.05). CONCLUSIONS: The clinical response to oral polymeric diet CT3211 is associated with mucosal healing and a down regulation of mucosal pro-inflammatory cytokine mRNA in both the terminal ileum and colon. In the ileum there was also an increase in transforming growth factor beta1 mRNA.

Adolescent↗
PubMed2000

Recent developments in the immunology of inflammatory bowel disease.

Crohn's disease and ulcerative colitis are caused by excessive immune reactivity in the gut wall. Analysis of the type of immune responses ongoing in diseased gut has revealed important features which suggest that these conditions are different. In Crohn's disease tissue there is considerable evidence for an ongoing T helper cell type 1 response, with excess interleukin-12, interferon-gamma and TNF-alpha. There is circumstantial evidence in patients that this response is directed against the normal bacterial flora and definitive evidence in mouse models that T cell responses to the flora cause gut disease. In ulcerative colitis, the role of tissue damaging T cell responses in the gut mucosa is much less clear and there is more evidence that the lesion is owing to antibody-mediated hypersensitivity. Although different types of immune reactions initiate tissue injury in both Crohn's disease and ulcerative colitis, the downstream events which actually damage the tissue are the same in each condition. Elevated cytokine concentrations in the mucosa lead to the production of excess matrix degrading enzymes by gut fibroblasts, loss of mucosal integrity and ulceration. The same process also leads to an increased production of epithelial growth factors such as KGF Keratinocyte Growth Factor by gut fibroblasts and produces the crypt cell hyperplasia characteristic of all gut inflammatory conditions.

Animals↗
PubMed2000

Bacterial regulation of intestinal immune responses.

If we understand pathological processess within the alimentary tract, it is apparent that the fundamental aspects of microbe-host interactions need to be examined in greater detail. Pathogenic bacteria have evolved strategies to alter and subvert the function of T cels and phagocytes in the gut wall, and exploiting these molecules may lead to new treatments for chronic inflammatory bowel diseases. The adaptation of microbes to their host must involve microbe-mediated interference of the host innate immune response. The recent demonstration that nonpathogenic E. coli have a beneficial effect in ulcerative colitis further supports the notion that normal flora may alter the expression of the innate immune receptors or recognize alternative receptors compared with pathogenic variants. Such differences may conceivably lead to beneficial and protective alterations to the host through cytokine and antimicrobial peptide expression. Perhaps the contact point between microbes and host cells lies with the pattern-recognition receptors such as TLRs. However, although much light has been shed on the downstream consequences of TLR activation, many more questions remain unsolved. For example, little is known about the expression profiles of the different TLRs throughout the gastrointestinal tract. Additionally, ambiguities remain over the natural ligands for TLRs. The discovery that the Drosophila Toll receptor acts downstream of the pathogen recognition event suggests that there are many more twists and turns to be revealed in the story of host-microbe interactions in the gastrointestinal tract.

Adhesins, Bacterial↗
PubMed2000

Expression of intimin gamma from enterohemorrhagic Escherichia coli in Citrobacter rodentium.

The carboxy-terminal 280 amino acids (Int280) of the bacterial adhesion molecule intimin include the receptor-binding domain. At least five different types of Int280, designated alpha, beta, gamma, delta, and epsilon, have been described based on sequence variation in this region. Importantly, the intimin types are associated with different evolutionary branches and contribute to distinct tissue tropism of intimin-positive bacterial pathogens. In this study we engineered a strain of Citrobacter rodentium, which normally displays intimin beta, to express intimin gamma from enterohemorrhagic Escherichia coli. We show that intimin gamma binds to the translocated intimin receptor (Tir) from C. rodentium and has the ability to produce attaching and effacing lesions on HEp-2 cells. However, C. rodentium expressing intimin gamma could not colonize orally infected mice or induce mouse colonic hyperplasia. These results suggest that intimin may contribute to host specificity, possibly through its interaction with a receptor on the host cell surface.

ATP-Binding Cassette Transporters↗
PubMed2000

Imbalance of stromelysin-1 and TIMP-1 in the mucosal lesions of children with inflammatory bowel disease.

BACKGROUND: Degradation of the extracellular matrix and ulceration of the mucosa are major features of inflammatory bowel disease (IBD). One of the most important enzymes in degrading the matrix and produced in excess by cytokine activated stromal cells, is stromelysin-1. The activity of stromelysin-1 is controlled by tissue inhibitor of metalloproteinase (TIMP-1), its natural inhibitor. In model systems excess stromelysin-1 produces mucosal degradation. METHODS: Quantitative competitive RT-PCR was used to analyse stromelysin-1 and TIMP-1 transcripts; western blotting was used to measure the amount of stromelysin-1 and TIMP-1 protein in biopsy samples from children with IBD. RESULTS: In biopsies from patients with active Crohn's disease (n=24), ulcerative colitis (n=23), and controls (n=16), TIMP-1 transcripts and protein were abundant and unchanged. Stromelysin-1 transcripts and protein were markedly elevated in mucosal biopsies obtained from inflamed sites of patients with active IBD but were not elevated in adjacent endoscopically normal mucosa (n=10). Elevated levels of stromelysin-1 transcripts in active Crohn's disease (n=5) returned to normal levels following treatment with enteral nutrition. CONCLUSIONS: Stromelysin-1 is markedly overexpressed at inflamed sites in patients with IBD whereas TIMP-1 remains unaltered. Excess stromelysin-1 is likely to be responsible for loss of mucosal integrity in IBD.

Blotting, Western↗
PubMed2000

Butyrate upregulates stromelysin-1 production by intestinal mesenchymal cells.

Nutritional factors and resident bacteria participate in the pathogenesis of intestinal inflammation. However, the ways in which bacteria and complex diets might modulate matrix metalloproteinase (MMP) production are unknown. We hypothesized that butyrate might enhance production of MMPs, thus amplifying their response to signals in inflammatory conditions. Human mesenchymal cells were incubated with butyrate and then stimulated with cytokines. MMPs and inhibitors were studied by Western blotting and quantitative RT-PCR. Acetylation of histones was examined in Triton X acetic acid-urea gels by PAGE. We showed that butyrate selectively enhanced the protein production and mRNA expression of stromelysin-1 in tumor necrosis factor-alpha- or interleukin-1beta-stimulated mesenchymal cells. Butyrate alone did not induce any change in MMP production or mRNA expression. It increased the acetylation of histones in mesenchymal cells. Furthermore, acetylation of histones (induced by trichostatin A) reproduced the effects of butyrate. Although butyrate is a major source of nutrient for the colonic epithelial cells, it modulates intestinal inflammation through the secretion of stromelysin-1 in stimulated stromal cells via the inhibition of histone deacetylase.

Acetylation↗
PubMed2000

Characterisation of acute murine dextran sodium sulphate colitis: cytokine profile and dose dependency.

BACKGROUND/AIMS: In our experience with the acute murine dextran sodium sulphate (DSS) model of experimental colitis, we noted both interstrain and interanimal variations in daily water consumption. One might critically question whether observed differences in injuries are just a dose dependency phenomenon reflecting variations in DSS intake. To clarify this important topic, we performed a dose and concentration dependency study of DSS in Balb/c mice. We also determined Th1 and Th2 cytokine levels to compare the cytokine profile to that from inflammatory bowel disease (IBD). METHODS: In four groups (14 animals each group) different concentrations of DSS (0, 2.5, 5 and 7.5%) were given for 7 days ad libitum. Mucosal injury of the entire colon was histologically assessed and graded. Cytokine levels were determined by competitive quantitative RT-PCR. RESULTS: A linear increase in the crypt damage score was noted with increasing concentrations (0, 4.9 +/- 0.7, 11.9 +/- 0.5 and 18.9 +/- 1.3, respectively), but the total dose of DSS intake did not correlate with mucosal damage. Progressive upregulation in the transcripts for Th1 cytokines (IL-12, IFN-gamma, IL-1, TNF-alpha) was observed with increasing dosage of DSS. Interestingly, an increase in IL-10, but not IL-4 mRNA transcripts was also noted. DISCUSSION: Acute DSS-induced mucosal injury is dependent on the administered DSS water concentration but not on the consumed DSS dose. The cytokine profile is a classic Th1 response and is similar to that of various inflammatory conditions in the colon. CONCLUSIONS: Minor variations in fluid consumption do not affect the severity of DSS-induced injury in mice. The acute murine DSS colitis model is useful for studying the pathophysiological aspects of colonic inflammatory diseases as IBD and for evaluating new potential therapeutic agents

Animals↗
PubMed2000

Manipulation of cytokines in the management of patients with inflammatory bowel disease.

In recent years, new concepts have been formulated for the therapeutic management of the intractable forms of Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease. These advances are based largely on new insights into the immune-inflammatory events occurring in the gut of these patients. Analysis of the types of immune response ongoing in the inflamed intestine has revealed that in Crohn's disease there is predominantly a T-helper cell type 1 response, with exaggerated production of interleukin (IL)-12 and interferon (IFN)-gamma, whereas in ulcerative colitis the lesion seems more of an antibody-mediated hypersensitivity reaction. Despite these differences, downstream inflammatory events are the same in both conditions. In both Crohn's disease and ulcerative colitis mucosa, IL-1gamma, IL-6, IL-8 and tumour necrosis factor (TNF)-alpha are produced in excess, and the production of free radicals accompanying the influx of nonspecific inflammatory cells into the mucosa is above the normal range. Strategies aimed at inhibiting T-cell responses are therefore more relevant in Crohn's disease, whereas, in theory at least, inhibition of downstream inflammatory processes should be therapeutic in both Crohn's disease and ulcerative colitis. This review seeks to summarize studies in which anticytokine antibodies, cytokines or cytokine-modifying agents have been used in the treatment of either Crohn's disease or ulcerative colitis.

Cytokines↗
PubMed1999

Role of bacterial intimin in colonic hyperplasia and inflammation.

Enteropathogenic Escherichia coli (EPEC) cells adhere to gut epithelial cells through intimin alpha: the ligand for a bacterially derived epithelial transmembrane protein called the translocated intimin receptor. Citrobacter rodentium colonizes the mouse colon in a similar fashion and uses a different intimin: intimin beta. Intimin alpha was found to costimulate submitogenic signals through the T cell receptor. Dead intimin beta+ C. rodentium, intimin alpha-transfected C. rodentium or E. coli strain K12, and EPEC induced mucosal hyperplasia identical to that caused by C. rodentium live infection, as well as a massive T helper cell-type 1 immune response in the colonic mucosa. Mutation of cysteine-937 of intimin to alanine reduced costimulatory activity in vitro and prevented immunopathology in vivo. The mucosal changes elicited by C. rodentium were interferon-gamma-dependent. Immunopathology induced by intimin enables the bacteria to promote conditions that are favorable for increased microbial colonization.

Adhesins, Bacterial↗
PubMed1999

Regulation of T cell activation in vitro and in vivo by targeting the OX40-OX40 ligand interaction: amelioration of ongoing inflammatory bowel disease with an OX40-IgG fusion protein, but not with an OX40 ligand-IgG fusion protein.

OX40 is a member of the TNFR superfamily, and is found predominantly on activated CD4-positive T cells. In vitro an OX40-IgG fusion protein inhibits mitogen- and Ag-driven proliferation and cytokine release by splenocytes and lymph node T cells. In contrast, an OX40 ligand-IgG fusion protein enhanced proliferative responses. In normal mice, OX40-positive cells are observed only in lymphoid tissues, including Peyer's patches of the gut. In mice with hapten-induced colitis or IL-2 knockout mice with spontaneous colitis, OX40-positive cells are found infiltrating the lamina propria. Administration of the OX40-IgG fusion protein to mice with ongoing colitis (but not the OX40 ligand-IgG) ameliorated disease in both mouse models of inflammatory bowel disease. This was evidenced by a reduction in tissue myeloperoxidase; reduced transcripts for TNF-alpha, IL-1, IL-12, and IFN-gamma; and a reduction in the T cell infiltrate. Targeting OX40 therefore shows considerable promise as a new strategy to inhibit ongoing T cell reactions in the gut.

Animals↗
PubMed1999

Effector and regulatory lymphoid cells and cytokines in mucosal sites.

In this review, I hope to have highlighted that cytokines are of crucial importance in the normal homeostasis of the gut immune system, the interactions of the gut immune system with enteric antigens and also in tissue injury associated with IBD. There is evidence from a number of different systems that the response to nominal non-replicating antigens, administered nasally or orally, is skewed towards a non-Th1 type of response. To say that the response is Th2, Th3 or Tr is premature. IL-10 and TGF beta seem to be important in downregulating potentially tissue-damaging Th1 responses to the normal flora and possibly food antigens. However, it need to be seen whether the mouse results also apply to humans. A consistent pattern in disease states, whether it be human or mouse, is an exaggerated Th1 type response with excess local production of IFN-gamma and TNF alpha, and its association with tissue injury. An important question to address is whether this represents a switch from the Th2, Th3, or Tr pathway towards a Th1 pathway, or whether the Th1 pathway is in fact always present in the gut, but is kept in check and non-pathogenic by regulatory cells. Equally important is the need to discover where regulation occurs: is it in the PP or the lamina propria? Intriguing results from Kronenberg and colleagues have shown that SCID mice reconstituted with CD45RBhi or CD45RBlo cells show no difference in the re-population of the gut prior to disease (ARANDA et al. 1997). The reason for colitis developing in those mice reconstituted with CD45RBhi cells is therefore more complex than merely differential re-population kinetics. No matter what the outcome is, these and other related questions dealing with the induction and expression of mucosal T-cell responses are going to produce some surprises in the next few years.

Animals↗
PubMed1999

Enhancing Lamina propria Th1 cell responses with interleukin 12 produces severe tissue injury.

BACKGROUND & AIMS: Interleukin (IL)-12 is believed to modulate local T-cell response in human colitis. A direct functional relationship between IL-12 and tissue injury in human intestine has not been reported. The aim of this study was to examine changes that take place in explant cultures of human fetal gut after stimulation of T cells with anti-CD3 in the presence of exogenous IL-12/IL-18. METHODS: T cells in explants of fetal gut were activated with anti-CD3 antibody and/or IL-12 or IL-18. Mucosal pathology was determined by immunohistochemistry. Quantitative reverse-transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay were used to determine cytokine synthesis, and the production of matrix metalloproteinases was analyzed by RT-PCR and Western blotting. RESULTS: Activation of T cells in explants with anti-CD3 antibody elicited very little interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha production and no tissue injury. Addition of graded doses of IL-12 with anti-CD3 resulted in a significant increase in both IFN-gamma and TNF-alpha. This change was associated with a massive increase in stromelysin-1 expression and severe tissue injury, which was inhibitable by a stromelysin-1 inhibitor. Costimulation of explants with anti-CD3 and IL-18 induced only IFN-gamma and no tissue injury. CONCLUSIONS: IL-12 can convert a physiological T-cell signal into a strong signal with the downstream effect of elevating tissue stromelysin-1 concentration and mucosal degradation.

Antigens, CD↗
PubMed1999

Citrobacter rodentium infection in mice elicits a mucosal Th1 cytokine response and lesions similar to those in murine inflammatory bowel disease.

Citrobacter rodentium is a classically noninvasive pathogen of mice that is similar to enteropathogenic Escherichia coli (EPEC) in man. Following oral infection of young mice, the organism colonizes the distal colon, and within 1 week the colonic mucosa doubles in thickness and there is massive epithelial cell hyperplasia. Since T-cell responses in mouse models of inflammatory bowel disease (IBD) also cause epithelial hyperplasia, we have investigated the possibility that C. rodentium promotes similar T-cell responses in the mucosa, thereby increasing epithelial shedding, transmission, and replication of the organism. Beginning 6 days after infection, bacteria were observed to be in close association with the epithelial surface and were also visible scattered throughout the lamina propria and in the submucosa. There was a CD3(+)-cell infiltrate into the colonic lamina propria and epithelium as well as mucosal thickening and crypt hyperplasia. The majority of CD3(+) cells were CD4(+) and were not gammadelta+. Reverse transcription-PCR analysis of cytokines also revealed a highly polarized Th1 response (interleukin-12, gamma interferon, and tumor necrosis factor alpha) in the mucosa and a large increase in the epithelial cell mitogen keratinocyte growth factor. None of the changes were seen in mice inoculated with bacteria lacking intimin (which is necessary for colonization), but they were seen in mice inoculated with C. rodentium complemented with intimin from EPEC. This is the first example of a classically noninvasive bacterial pathogen which elicits a strong mucosal Th1 response and which produces pathology similar to that seen in mouse models of IBD, which is also characterized by a strong Th1 response. These results also suggest that the colonic mucosa responds in a stereotypic way to Th1 responses.

Adhesins, Bacterial↗