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R B Sartor

Publications and source records attributed to R B Sartor.

At least 19 recordsLinked to original sources
PubMed2006

Adoptive transfer of nontransgenic mesenteric lymph node cells induces colitis in athymic HLA-B27 transgenic nude rats.

HLA-B27 transgenic (TG) rats develop spontaneous colitis when colonized with intestinal bacteria, whereas athymic nude (rnu/rnu) HLA-B27 TG rats remain disease free. The present study was designed to determine whether or not HLA-B27 expression on T cells is required for development of colitis after transfer of mesenteric lymph node (MLN) cells into rnu/rnu HLA-B27 recipients. Athymic nontransgenic (non-TG) and HLA-B27 TG recipients received MLN cells from either TG or non-TG rnu/+ heterozygous donor rats that contain T cells. HLA-B27 TG rnu/rnu recipients receiving either non-TG or TG MLN cells developed severe colitis and had higher caecal MPO and IL-1beta levels, and their MLN cells produced more IFN-gamma and less IL-10 after in vitro stimulation with caecal bacterial lysate compared to rnu/rnu non-TG recipients that remained disease free after receiving either TG or non-TG cells. Interestingly, proliferating donor TG T cells were detectable one week after adoptive transfer into rnu/rnu TG recipients but not after transfer into non-TG recipients. T cells from either non-TG or TG donors induce colitis in rnu/rnu TG but not in non-TG rats, suggesting that activation of effector T cells by other cell types that express HLA-B27 is pivotal for the pathogenesis of colitis in this model.

Adoptive Transfer↗
PubMed2005

Regulatory CD4+CD25+ cells reverse imbalances in the T cell pool of bone marrow transplanted TGepsilon26 mice leading to the prevention of colitis.

BACKGROUND AND AIMS: Erroneous thymic selection of developing T lymphocytes may be responsible for the expansion of self reactive T cells or may contribute to the absence of regulatory T cells important in controlling peripheral inflammatory processes. Colitis in bone marrow (BM) transplanted Tgepsilon26 mice is induced by abnormally activated T cells developing in an aberrant thymic microenvironment. We investigated the protective role of regulatory CD4+CD25+ T cells in this model. METHODS: BM from (C57BL/6 x CBA/J) F1 mice was transplanted into specific pathogen free Tgepsilon26 mice (BM-->Tgepsilon26). Transplanted mice received no cells (control), sorted CD4+CD25+, or CD4+CD25- cells from mesenteric lymph nodes (MLN) of normal mice. MLN cell subsets were analysed using membrane markers. Cytokine secretion of MLN cells was measured using intracellular cytokine staining and cytokine secretion in anti-CD3 stimulated cell cultures. Colitis was measured by histological scores. RESULTS: CD4+CD25+ cells were reduced in the MLNs of BM-->Tgepsilon26 mice. Transfer of regulatory CD4CD4+CD25+ but not of CD4+CD25- cells reduced the number of MLN CD4+ T cells in BM-->Tgepsilon26 recipients and increased the number of MLN CD8+ cells, thereby normalising the CD4+/CD8+ ratio. CD4+CD25+ but not CD4+CD25- cell transfer into BM-->Tgepsilon26 mice reduced the number of tumour necrosis factor alpha+ CD4+ cells and increased the secretion of transforming growth factor beta by MLN cells. Transfer of 3 x 10(5) CD4+CD25+ cells after BM transplantation into Tgepsilon26 mice prevented colitis whereas CD4+CD25- cells had no protective effect. CONCLUSIONS: These results suggest that defective selection or induction of regulatory T cells in the abnormal thymus is responsible for the development of colitis in BM-->Tgepsilon26 mice. Transfer of CD4+CD25+ cells can control intestinal inflammation in BM-->Tgepsilon26 mice by normalising the number and function of the MLN T cell pool.

Animals↗
PubMed2004

Reduced ratio of protective versus proinflammatory cytokine responses to commensal bacteria in HLA-B27 transgenic rats.

Germ-free HLA-B27 transgenic (TG) rats do not develop colitis, but colonization with specific pathogen-free (SPF) bacteria induces colitis accompanied by immune activation. To study host-dependent immune responses to commensal caecal bacteria we investigated cytokine profiles in mesenteric lymph node (MLN) cells from HLA-B27 TG versus nontransgenic (non-TG) littermates after in vitro stimulation with caecal bacterial lysates (CBL). Supernatants from CBL-stimulated unseparated T- or B- cell-depleted MLN cells from HLA-B27 TG and non-TG littermates were analysed for IFN-gamma, IL-12, TNF, IL-10 and TGF-beta production. Our results show that unfractionated TG MLN cells stimulated with CBL produced more IFN-gamma, IL-12 and TNF than did non-TG MLN cells. In contrast, CBL-stimulated non-TG MLN cells produced more IL-10 and TGF-beta. T cell depletion abolished IFN-gamma and decreased IL-12 production, but did not affect IL-10 and TGF-beta production. Conversely, neither IL-10 nor TGF-beta was produced in cultures of B cell-depleted MLN. In addition, CD4(+) T cells enriched from MLN of HLA-B27 TG but not from non-TG rats produced IFN-gamma when cocultured with CBL-pulsed antigen presenting cells from non-TG rats. Interestingly, IL-10 and TGF-beta, but not IFN-gamma, IL-12 and TNF were produced by MLN cells from germ-free TG rats. These results indicate that the colitis that develops in SPF HLA-B27 TG rats is accompanied by activation of IFN-gamma-producing CD4(+) T cells that respond to commensal bacteria. However, B cell cytokine production in response to components of commensal intestinal microorganisms occurs in the absence of intestinal inflammation.

Animals↗
PubMed2004

Differential effect of immune cells on non-pathogenic Gram-negative bacteria-induced nuclear factor-kappaB activation and pro-inflammatory gene expression in intestinal epithelial cells.

We have previously shown that non-pathogenic Gram negative bacteria induce RelA phosphorylation, nuclear factor (NF)-kappaB transcriptional activity and pro-inflammatory gene expression in intestinal epithelial cells (IEC) in vivo and in vitro. In this study, we investigated the molecular mechanism of immune-epithelial cell cross-talk on Gram-negative enteric bacteria-induced NF-kappaB signalling and pro-inflammatory gene expression in IEC using HT-29/MTX as well as CaCO-2 transwell cultures Interestingly, while differentiated HT-29/MTX cells are unresponsive to non-pathogenic Gram negative bacterial stimulation, interleukin-8 (IL-8) mRNA accumulation is strongly induced in Escherichia coli- but not Bacteroides vulgatus-stimulated IEC cocultured with peripheral blood (PBMC) and lamina propria mononuclear cells (LPMC). The presence of PBMC triggered both E. coli- and B. vulgatus-induced mRNA expression of the Toll-like receptor-4 accessory protein MD-2 as well as endogenous IkappaBalpha phosphorylation, demonstrating similar capabilities of these bacteria to induce proximal NF-kappaB signalling. However, B. vulgatus failed to trigger IkappaBalpha degradation and NF-kappaB transcriptional activity in the presence of PBMC. Interestingly, B. vulgatus- and E. coli-derived lipopolysaccharide-induced similar IL-8 mRNA expression in epithelial cells after basolateral stimulation of HT-29/PBMC cocultures. Although luminal enteric bacteria have adjuvant and antigenic properties in chronic intestinal inflammation, PBMC from patients with active ulcerative colitis and Crohn's disease differentially trigger epithelial cell activation in response to E. coli and E. coli-derived LPS. In conclusion, this study provides evidence for a differential regulation of non-pathogenic Gram-negative bacteria-induced NF-kappaB signalling and IL-8 gene expression in IEC cocultured with immune cells and suggests the presence of mechanisms that assure hyporesponsiveness of the intestinal epithelium to certain commensally enteric bacteria.

Animals↗
PubMed2003

Butyrate modulates intestinal epithelial cell-mediated neutrophil migration.

Butyrate, a short-chain fatty acid released by colonic bacteria and administered therapeutically in inflammatory bowel diseases, exerts immunomodulatory properties. The aim of the study was to determine the functional consequences of butyrate exposure on the proinflammatory responsiveness of human intestinal epithelial cells (IEC). IL-8 promoter activity in IEC pretreated with butyrate then exposed to proinflammatory stimuli was assayed by transfection of luciferase constructs. IL-8 secretion was determined by ELISA and neutrophil migration by flow cytometry. Receptor mRNA was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Butyrate modulated proinflammatory IL-8 secretion differentially in Caco-2 and HT-29 cells on the transcriptional level. Pointing to the potentially underlying mechanism of increased IL-1 beta-stimulated IL-8 secretion in HT-29 cells, butyrate up-regulated IL-1RI mRNA but not IL-1RII. Butyrate pretreatment of IEC lines stimulated by IL-1 beta modulated neutrophil migration significantly: reduction towards Caco-2 and enhancement towards HT-29/p cells. Pharmacological inhibition of protein tyrosine phosphatases or treatment with mesalamine or sulphasalazine diminished IL-1 beta-stimulated IL-8 secretion by butyrate-exposed HT-29 cells substantially. Immunomodulatory effects of butyrate on IEC are functionally relevant for neutrophil migration. Pharmacological inhibition of enhanced IL-1 beta-mediated IL-8 secretion in a subpopulation of IEC may improve the clinical efficacy of butyrate.

Adjuvants, Immunologic↗
PubMed2003

Antibiotics with a selective aerobic or anaerobic spectrum have different therapeutic activities in various regions of the colon in interleukin 10 gene deficient mice.

BACKGROUND AND AIMS: Multiple rodent models implicate resident intestinal bacteria in the pathogenesis of chronic immune mediated intestinal inflammation. Specific pathogen free (SPF) interleukin 10 gene deficient (IL-10(-/-)) mice develop colitis, which does not occur in the germ free (GF) state. We investigated whether broad or narrow spectrum antibiotics affect onset and progression of disease in various regions of IL-10(-/-) mice. METHODS: Metronidazole, ciprofloxacin, vancomycin-imipenem (50 mg/kg/day), or water (control) was administered orally before (prevention) or two weeks after (treatment) colonisation of GF IL-10(-/-) mice with SPF bacteria. After four weeks, colonic histology scores and cytokine production by colonic explants were determined. Caecal and colonic contents were collected for quantitative bacterial analysis. RESULTS: In the prevention study, all antibiotics decreased inflammation in the caecum and colon. However, in the treatment study, ciprofloxacin and vancomycin-imipenem decreased caecal inflammation, and reduced Escherichia coli and Enterococcus faecalis concentrations, whereas only vancomycin-imipenem lowered direct microscopic bacterial counts. In contrast, metronidazole and vancomycin-imipenem reduced colonic injury and eliminated anaerobic bacteria, including Bacteroides spp. CONCLUSIONS: Both narrow and broad spectrum antibiotics can prevent disease but treatment of established colitis is more selective. Ciprofloxacin is most effective in the treatment of caecal inflammation, metronidazole preferentially treats the colon, whereas vancomycin-imipenem definitively treats both regions. These results suggest that subsets of aerobic or anaerobic bacteria show regional differences in their capacity to mediate experimental colitis in IL-10(-/-) mice.

Animals↗
PubMed2003

Lactobacillus GG prevents recurrence of colitis in HLA-B27 transgenic rats after antibiotic treatment.

BACKGROUND AND AIMS: Bacteroides vulgatus induces colitis in gnotobiotic HLA-B27 transgenic (TG) rats while broad spectrum antibiotics prevent and treat colitis in specific pathogen free (SPF) TG rats although disease recurs after treatment ends. Lactobacilli treat human pouchitis and experimental colitis. We investigated if Lactobacillus rhamnosus GG (L GG) can prevent colitis in TG rats monoassociated with B vulgatus and if L GG or Lactobacillus plantarum 299v (LP 299v) can treat established colitis in SPF TG rats and prevent recurrent disease after antibiotics were stopped. METHODS: Germfree B27 TG rats were monoassociated with B vulgatus for four weeks following two weeks of colonisation with L GG or no bacteria. SPF B27 TG rats received oral vancomycin and imipenem for two weeks, or water alone, followed by four weeks of treatment with oral L GG, LP 299v, or water only. Disease activity was quantified by blinded gross and histological scores, caecal myeloperoxidase (MPO) activity, and levels of interleukin (IL)-1 beta, tumour necrosis factor (TNF), transforming growth factor beta, and IL-10. RESULTS: L GG did not prevent colitis in B vulgatus co-associated TG rats or treat established disease in SPF rats. However, L GG but not LP 299v prevented colitis relapse in antibiotic treated rats with reduced gross and histological scores, caecal MPO, IL-1 beta, and TNF whereas caecal IL-10 was increased. CONCLUSIONS: L GG does not prevent colitis in gnotobiotic TG rats or treat established disease in SPF rats, but is superior to LP 299v in the prevention of recurrent colitis. These studies suggest that antibiotics and probiotic agents provide synergistic therapeutic effects, perhaps mediated by altered immunomodulation with selective activity of different lactobacillus species.

Animals↗
PubMed2001

Bradykinin receptor antagonists type 2 attenuate the inflammatory changes in peptidoglycan-induced acute arthritis in the Lewis rat.

OBJECTIVE AND DESIGN: We studied the ability of bradykinin (BK) receptor antagonists type 1 and 2 (B1-RA, B2-RA) to prevent acute inflammation. MATERIAL: A peptidoglycan-polysaccharide (PG-APS)-induced model of arthritis in the Lewis rat was analyzed. TREATMENT: Four groups of animals were studied for 5 days. Treatment was administered subcutaneously (s.c.) 1 mg/kg every 12 h. Group I received PG-APS and was treated with the B2-RA, CP-0597 (DArg-Arg-Pro-Hyp-Gly-Thi-Ser-DTic-NChg-Arg). Group II received PG-APS and was treated with a combined B1 and B2-RA, B9430 (DArg-Arg-Pro-Hyp-Gly-Igl-Ser-Dlgl-Oic-Arg). Group III received PG-APS and albumin control. Group IV received albumin control. METHODS: Joint diameter, liver weight, hematocrit, white blood count and plasma concentrations of prekallikrein, high molecular weight kininogen, HK and IL-beta were measured. Groups were compared by ANOVA. RESULTS: Acute arthritis and hepatomegaly were attenuated in the B2-RA-treated animals (p<0.05). Weight loss was more pronounced in the B1/B2-RA-treated animals. Anemia induced by PG-APS was prevented by B2-RA and B1/B2-RA treatment (p<0.001). A marked decrease in plasma HK to 64% of normal was found in the disease-untreated animals, which was completely normalized by B2-RA treatment and partially attenuated by the B1/B2-RA (78%). The decrease in plasma prekallikrein levels was prevented by combined B1/B2-RA treatment (p<0.05). Finally, elevated plasma IL-1beta levels were lowered by B1/B2-RA treatment and were below detection limits with the B2-RA treatment. CONCLUSIONS: These results indicate that the systemic inflammation is due in part to BK generation which can be blocked by B2-RA, while inhibiting the B1 receptor prevents an anti-inflammatory response.

Acute Disease↗
PubMed2001

Disrupted B-lymphocyte development and survival in interleukin-2-deficient mice.

Interleukin-2-deficient (IL-2-/-) mice develop a spontaneous, progressive, CD4+ T-cell-mediated colitis with an age-related decrease in the number of B lymphocytes. The aim of this study was to determine the mechanisms of B-cell loss in IL-2-/- mice. Serum immunoglobulin G1 (IgG1) levels in 8-week-old IL-2-/- mice were above normal but then decreased dramatically with advancing age. Between 8 and 11 weeks of age, the number of B-cell progenitors (B220+ IgM-) in the bone marrow of IL-2-/- mice was less than half of those in IL-2+/+ littermates. By 22 weeks of age, very few progenitor cells remained in the bone marrow of most mice, and spleens were almost devoid of B cells. Likewise, B1 cells were not present in the peritoneal cavity of aged IL-2-/- mice. Flow cytometry analysis of B-cell differentiation in the bone marrow suggested a progressive loss of B cells from the most mature to the least mature stages, which was not dependent on IL-2 receptor-alpha (IL-2Ralpha) expression. B cells transferred from normal animals had similar survival rates in IL-2-/- and wild-type mice. We conclude that conventional B cells in older IL-2-/- mice are lost by attrition owing to a derangement in B-cell development. Because B1 cells are less dependent on the bone marrow, a separate mechanism for their loss is suggested.

Animals↗
PubMed2001

Expression and localization of IL-1beta mRNA is interrelated with cytoskeletal rearrangement in monocytes stimulated by adherence: a light microscopy in situ hybridization study.

Differences in IL-1beta mRNA expression, stability and translation between non-adherent monocytes and those stimulated by adherence suggest that cytokine regulation is coupled to the function and assembly of cytoskeletal structures. In situ hybridization studies were performed to visualize expression and positioning of IL-1beta mRNA in adherently cultivated monocytes. IL-1beta mRNA expression was heterogeneous with high transcript levels found in spread or polarized cells. Transcripts were compartmentalized to the perinuclear region in spread cells, and partially redistributed with polarization. In contrast to mRNA distribution in other motile cell populations, IL-1beta mRNA did not localize to the distal or proximal actin cytoskeleton. Perinuclear confinement of transcripts required intact actin microfilaments. Treatment with cytoskeleton disruption and detergent extraction suggested that most non-translated IL-1beta mRNA was associated with intermediate filaments. In monocytes stimulated by LPS, IL-1beta, but not IL-1Ra transcripts were redistributed and partially associated, yet not bound to actin microfilaments. The present study demonstrates that IL-1beta mRNA expression and localization in adherent monocytes is interrelated with the cytoskeletal rearrangement upon adherence, spreading and polarization.

Actins↗
PubMed2001

Enhanced survival and mucosal repair after dextran sodium sulfate-induced colitis in transgenic mice that overexpress growth hormone.

BACKGROUND & AIMS: Growth hormone (GH) is used as therapy for inflammatory bowel disease (IBD), but the specific effects on intestine are unknown. Transgenic mice overexpressing GH (MT1-bGH-TG) were used to test whether increased plasma GH levels alter inflammation or crypt damage during dextran sodium sulfate (DSS)-induced colitis. METHODS: MT1-bGH-TG and wild-type (WT) littermates were given 3% DSS for 5 days followed by up to 10 days of recovery. Colitis and epithelial cell proliferation were evaluated histologically. Plasma insulin-like growth factor (IGF)-I and colonic IGF-I, interleukin (IL)-1beta, and intestinal trefoil factor (ITF) messenger RNAs (mRNAs) were measured. RESULTS: DSS induced similar disease onset in MT1-bGH-TG and WT. More MT1-bGH-TG survived than WT. By recovery day 7, MT1-bGH-TG had less inflammation and crypt damage, elevated plasma IGF-I, and increased colonic ITF expression relative to WT. Colonic IL-1beta was elevated in DSS-treated MT1-bGH-TG and WT, but IL-1beta mRNA abundance correlated with disease only in WT. MT1-bGH-TG showed earlier increases in epithelial cell proliferation than WT during recovery but only WT showed atypical repair. CONCLUSIONS: GH does not alter susceptibility to acute DSS-induced colitis but enhances survival, remission of inflammation, and mucosal repair during recovery. GH therapy may be beneficial during active IBD by improving mucosal repair.

Animals↗
PubMed2001

Continuous stimulation by normal luminal bacteria is essential for the development and perpetuation of colitis in Tg(epsilon26) mice.

BACKGROUND & AIMS: Normal resident bacteria are required for development of colitis in several rodent models. We determined whether bacterial stimulation is necessary for both induction and perpetuation of mucosal inflammation and T-cell activation in Tg(epsilon26) mice, in which transplantation of wild-type bone marrow (BM-->Tg(epsilon26)) causes colitis under specific pathogen-free (SPF) conditions. METHODS: BM from (C57BL/6 X CBA/J) F1 mice was transplanted into germfree (GF) or SPF Tg(epsilon26) mice. Mesenteric lymph node (MLN) cells from these mice were then transferred into SPF or GF recipients. Colitis and activation of MLN cells were measured by histologic scores, membrane marker analysis, and intracellular cytokine staining. Cytokine secretion by MLN cells stimulated by anti-CD3 or by luminal or epithelial antigens was measured by ELISA. RESULTS: Colitis did not develop when BM was transferred into GF recipient mice (BM-->GF Tg(epsilon26)). T lymphocytes that secreted interferon gamma upon activation were present in the MLN of BM-->GF Tg(epsilon26) mice, albeit in lower frequency than in control BM-->SPF Tg(epsilon26) mice. Furthermore, transfer of MLN cells from BM-->SPF Tg(epsilon26) mice into SPF Tg(epsilon26) recipients induced active colitis, but not if the same cells were transferred into GF Tg(epsilon26) recipients. Although CD4 T cells were detected in the colonic mucosa of GF recipients, no inflammation was observed for at least 31 weeks. In a reciprocal experiment, MLN cells from BM-->GF Tg(epsilon26) mice without colitis transferred disease to SPF Tg(epsilon26) recipients within 2-4 weeks. CONCLUSIONS: Activated T cells are present in the mucosa of BM-->GF Tg(epsilon26) mice but are incapable of inducing disease unless colonic bacteria are present. Moreover, pathogenic T cells require the continuous presence of colonic bacteria to sustain colitis.

Animals↗
PubMed2001

Intestinal microflora in human and experimental inflammatory bowel disease.

Commensal luminal bacteria stimulate protective or tolerogenic mucosal immune responses in normal (ie, resistant) hosts and detrimental responses, which result in chronic intestinal inflammation, in genetically susceptible hosts. Enteric pathogens appear to be important in the initiation and reactivation of human inflammatory bowel disease, and may be responsible for chronic inflammation in at least a subset of patients with inflammatory bowel diseases. Individual components of the commensal flora have variable abilities to induce inflammatory and protective immune responses; these preferential immune responses to individual bacterial species may be unique to each host's genetic background. Analogous to the balance between pro- and antiinflammatory cytokines and T-cell subsets, the ratio between protective (ie, probiotic) and aggressive commensal bacteria may determine whether there is mucosal homeostasis or chronic, relapsing intestinal inflammation. Therapeutic alteration of the luminal microenvironment by probiotic, prebiotic, and molecular strategies offers great promise for nontoxic treatment of inflammatory bowel disease.

Journal Article↗
PubMed2001

Induction of mucosal immune responses by bacteria and bacterial components.

Bacteria have well documented abilities to induce protective as well as pathogenic mucosal immune responses, with the type of response dependent on the genetically programmed balance of pro- and anti-inflammatory cytokines and T-lymphocyte subsets. Inflammatory bowel disease, especially Crohn disease and periodontal disease, appear to be overly aggressive cellular immune responses to some, but not all, normal resident bacteria. Recent evidence suggests that the balance of protective (probiotic) and aggressive commensal luminal bacterial species is an additional determinant of mucosal homeostasis (tolerance) versus pathogenic immune responses (loss of tolerance) and that this balance can be therapeutically manipulated. Mucosal pathogens elicit a characteristic profile of cytokines from epithelial cells, including chemokines that recruit effector cells to the site of invasion to clear the invading organism. The molecular mechanisms of epithelial attachment and invasion of bacterial pathogens (eg, Salmonella, Shigella, pathogenic Escherichia coli, and Yersinia) and the mechanisms of injury induced by Clostridium difficile toxins and Helicobacter pylori are beginning to be understood, as are the innate and cognate host immune responses to these organisms, leading to novel means to effectively block bacterial injury and induce protective immune responses through immunization.

Journal Article↗
PubMed2001

Different subsets of enteric bacteria induce and perpetuate experimental colitis in rats and mice.

Resident bacteria are incriminated in the pathogenesis of experimental colitis and inflammatory bowel diseases. We investigated the relative roles of various enteric bacteria populations in the induction and perpetuation of experimental colitis. HLA-B27 transgenic rats received antibiotics (ciprofloxacin, metronidazole, or vancomycin-imipenem) in drinking water or water alone in either prevention or treatment protocols. Mice were treated similarly with metronidazole or vancomycin-imipenem before or after receiving 5% dextran sodium sulfate (DSS). Germfree transgenic rats were colonized with specific-pathogen-free enteric bacteria grown overnight either in anaerobic or aerobic atmospheres. Nontransgenic rats colonized with anaerobic bacteria served as negative controls. Although preventive metronidazole significantly attenuated colitis in transgenic rats and DSS-treated mice, it had no therapeutic benefit once colitis was established. Ciprofloxacin also partially prevented but did not treat colitis in B27 transgenic rats. In both animal models vancomycin-imipenem most effectively prevented and treated colitis. Germfree transgenic rats reconstituted with enteric bacteria grown under anaerobic conditions had more aggressive colitis than those associated with aerobic bacteria. These results suggest that a subset of resident luminal bacteria induces colitis, but that a complex interaction of commensal aerobic and anaerobic bacteria provides the constant antigenic drive for chronic immune-mediated colonic inflammation.

Animals↗
PubMed2000

Cellular differentiation causes a selective down-regulation of interleukin (IL)-1beta-mediated NF-kappaB activation and IL-8 gene expression in intestinal epithelial cells.

Interleukin (IL)-1beta signals through various adapter proteins and kinases that lead to activation of numerous downstream targets, including the transcription factors including NF-kappaB. In this study, we analyzed and characterized the effect of the differentiation of intestinal epithelial cells on IL-1beta-mediated NF-kappaB activation and IL-8 gene expression. We report that IL-8 mRNA accumulation and protein secretion were down-regulated in IL-1beta- and lipopolysaccharide-stimulated differentiated HT-29 cells (HT-29/MTX, where MTX is methotrexate) compared with undifferentiated cells (HT-29/p), whereas no differential effects were found following tumor necrosis factor (TNF)-alpha or phorbol myristate acetate stimulation. Cross-linking and affinity binding studies reveal that IL-1beta exclusively binds the type I receptor (IL-1RI) and not IL-1RII in both HT-29/p and HT-29/MTX cells. IL-1beta-mediated IkappaB kinase and c-Jun N-terminal kinase (JNK) activity were both diminished in differentiated HT-29 cells. DNA binding activity in differentiated HT-29 cells relative to HT-29/p cells was strongly reduced following IL-1beta exposure but not after TNF-alpha stimulation. The proximal IL-1 signaling molecule IL-1 receptor-associated kinase was not degraded in IL-1beta-stimulated HT-29 cells, in contrast to Caco-2 cells. kappaB-luciferase reporter gene activity was 16-fold higher following TNF receptor-associated factor-6 transfection after IL-1beta stimulation in HT-29/MTX cells. We conclude that cellular differentiation of HT-29 cells selectively impairs the IL-1beta signaling pathway inhibiting both NF-kappaB and JNK activity in response to IL-1beta. This relative unresponsiveness to IL-1beta may represent an important regulatory mechanism of differentiated intestinal epithelial cells.

Cell Differentiation↗
PubMed2000

Probiotics and inflammatory bowel diseases.

The pathogenesis of inflammatory bowel diseases remains elusive. However, the resident luminal bacteria seem to be an important factor in their development and chronicity. There is evidence to suggest that inflammatory bowel diseases may represent an aggressive immunological response to the resident luminal flora, rather than an alteration in the normal flora. In prior research, probiotic bacteria were effective in managing certain acute diarrheal diseases, and investigators reported that certain Lactobacilli strains seem to have protective immunomodulating and bowel flora manipulating properties. We report the results of recent studies with probiotics in animal models, in which promising effects for the treatment of chronic inflammatory bowel disease, pouchitis, and ulcerative colitis were observed. Future research may clarify a precise role for probiotic bacteria in managing chronic inflammatory bowel diseases.

Animals↗