Ulcerative Colitis: Podolsky DK

Xavier RJ, Podolsky DK. · Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, and, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA. · Nature. · Pubmed #17653185 No free full text.

Abstract: Recently, substantial advances in the understanding of the molecular pathogenesis of inflammatory bowel disease (IBD) have been made owing to three related lines of investigation. First, IBD has been found to be the most tractable of complex disorders for discovering susceptibility genes, and these have shown the importance of epithelial barrier function, and innate and adaptive immunity in disease pathogenesis. Second, efforts directed towards the identification of environmental factors implicate commensal bacteria (or their products), rather than conventional pathogens, as drivers of dysregulated immunity and IBD. Third, murine models, which exhibit many of the features of ulcerative colitis and seem to be bacteria-driven, have helped unravel the pathogenesis/mucosal immunopathology of IBD.

Cario E, Podolsky DK. · Division of Gastroenterology & Hepatology, University Hospital of Essen, Institutsgruppe I, Virchowstrasse 171, D-45147 Essen, Germany. · Ann N Y Acad Sci. · Pubmed #17057213 No free full text.

Abstract: This review discusses the current progress in the understanding of how commensal-mediated activation of toll-like receptors (TLRs) may be involved in the regulation of physiological and pathophysiological processes of the intestinal mucosa including tissue regeneration and inflammation. While regulation of TLRs and their downstream signaling mediators might be used to prevent and treat inflammatory bowel diseases, paradoxically, at this time, it remains uncertain whether this would be more effectively accomplished by enhancing or inhibiting these pathways.

Podolsky DK. · Gastrointestinal Unit, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA. · J Gastroenterol. · Pubmed #12698875 No free full text.

Abstract: Throughout most of the past 50 years, treatment of Crohn's disease and ulcerative colitis has been dominated by the use of agents whose efficacy was defined on an empiric basis. Many of these, including most especially 5-amino salicylic acid (5-ASA)-based agents and corticosteroids, remain mainstays of current treatment even as research is catching up with clinical experience to define the mechanistic basis of their efficacy. Other agents, also of established utility in at least a subset of patients, were developed on the basis of general inferences about disease pathogenesis. These agents are exemplified by antibiotics (metronidazole) and immunosuppressive agents (azathioprine/6-mercaptopurine, methotrexate, and cyclosporine); attention was directed on the assumption of the general likely importance of microbial species and immunoactivation, respectively. However, the rapid progress, even if still incomplete in understanding of pathophysiological mechanisms that play a role in IBD, has transformed the development of new therapeutic agents, enabling the development of several agents now available or currently in advanced clinical development. It is notable that each of the major overall thrusts in development of new therapeutic strategies parallels, and may be reasonably viewed as the partial outgrowth of, dominant areas of progress in understanding of disease mechanisms relevant to IBD.

Podolsky DK. · Gastrointestinal Unit and the Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital and Harvard Medical School, Boston, USA. · N Engl J Med. · Pubmed #12167685 No free full text.

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Beck PL, Podolsky DK. · Department of Medicine, Massachusetts General Hospital 02114, USA. · Inflamm Bowel Dis. · Pubmed #10028449 No free full text.

Abstract: The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

Sands BE, Tremaine WJ, Sandborn WJ, Rutgeerts PJ, Hanauer SB, Mayer L, Targan SR, Podolsky DK. · Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Boston 02114, USA. · Inflamm Bowel Dis. · Pubmed #11383595 No free full text.

Abstract: We report the experience of 11 patients (of 60 planned patients) enrolled in a double-blind, placebo-controlled clinical trial of infliximab in patients with severe, active steroid-refractory ulcerative colitis. The study was terminated prematurely because of slow enrollment. Patients having active disease for at least 2 weeks and receiving at least 5 days of intravenous corticosteroids were eligible to receive a single intravenous infusion of infliximab at 5, 10, or 20 mg/kg body weight. The primary endpoint used in this study was treatment failure at 2 weeks after infusion. Treatment failure was defined as 1) unachieved clinical response as defined by a modified Truelove and Witts severity score, 2) increase in corticosteroid dosage, 3) addition of immunosuppressants, 4) colectomy, or 5) death. Safety evaluations included physical examination, clinical chemistry and hematology laboratory tests, and occurrence of adverse experiences. Four of 8 patients (50%) who received infliximab were considered treatment successes at 2 weeks, compared with none of 3 patients who received placebo. Improvement in erythrocyte sedimentation rates and serum concentrations of C-reactive protein and interleukin-6 correlated with the clinical response observed in patients receiving infliximab. Infusion with infliximab produced no significant adverse events. Infliximab was well tolerated and may provide clinical benefit for some patients with steroid-refractory ulcerative colitis.

Podolsky DK, Gerken G, Eyking A, Cario E. · Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas, USA. · Gastroenterology. · Pubmed #19303021 No free full text.

Abstract: BACKGROUND & AIMS: Goblet cells (GC) facilitate mucosal protection and epithelial barrier repair, yet the innate immune mechanisms that selectively drive GC functions have not been defined. The aim of this study was to determine whether Toll-like receptor (TLR) 2 and modulation of GC-derived trefoil factor (TFF) 3 are functionally linked in the intestine. METHODS: GC modulation was assessed using quantitative real-time polymerase chain reaction analysis (qRT-PCR), Western blotting, and confocal microscopy. Dextran sulfate sodium (DSS) colitis was induced in wild-type, TFF3(-/-), and TLR2(-/-) mice. Recombinant TLR2 ligand or TFF3 peptide were orally administered after DSS termination. Caco-2 cells overexpressing full-length TLR2 or mutant TLR2-R753Q were tested for TFF3 synthesis and functional-related effects in a wounding assay. RESULTS: Data from in vitro (Ls174T) and ex vivo models of murine and human GC reveal that TLR2 activation selectively induces synthesis of TFF3. In vivo studies using TFF3(-/-) or TLR2(-/-) mice demonstrate the ability for oral treatment with a TLR2 agonist to confer antiapoptotic protection of the intestinal mucosa against inflammatory stress-induced damage through TFF3. Recombinant TFF3 rescues TLR2-deficient mice from increased morbidity and mortality during acute colonic injury. Severe ulcerative colitis (UC) has recently been found to be associated with the R753Q polymorphism of the TLR2 gene. The relevance of the observed functional effect of TLR2 in regulating GC is confirmed by the finding that the UC-associated TLR2-R753Q variant is functionally deficient in the ability to induce TFF3 synthesis, thus leading to impaired wound healing. CONCLUSIONS: These data demonstrate a novel function of TLR2 in intestinal GC that links products of commensal bacteria to innate immune protection of the host via TFF3.

De Jager PL, Franchimont D, Waliszewska A, Bitton A, Cohen A, Langelier D, Belaiche J, Vermeire S, Farwell L, Goris A, Libioulle C, Jani N, Dassopoulos T, Bromfield GP, Dubois B, Cho JH, Brant SR, Duerr RH, Yang H, Rotter JI, Silverberg MS, Steinhart AH, Daly MJ, Podolsky DK, Louis E, Hafler DA, Rioux JD, Anonymous00242, Anonymous00243. · Department of Neurology, Center for Neurologic Diseases, Brigham & Women's Hospital and Harvard Medical School, Boston, MA, USA. · Genes Immun. · Pubmed #17538633 No free full text.

Abstract: The intestinal flora has long been thought to play a role either in initiating or in exacerbating the inflammatory bowel diseases (IBD). Host defenses, such as those mediated by the Toll-like receptors (TLR), are critical to the host/pathogen interaction and have been implicated in IBD pathophysiology. To explore the association of genetic variation in TLR pathways with susceptibility to IBD, we performed a replication study and pooled analyses of the putative IBD risk alleles in NFKB1 and TLR4, and we performed a haplotype-based screen for association to IBD in the TLR genes and a selection of their adaptor and signaling molecules. Our genotyping of 1539 cases of IBD and pooled analysis of 4805 cases of IBD validates the published association of a TLR4 allele with risk of IBD (odds ratio (OR): 1.30, 95% confidence interval (CI): 1.15-1.48; P=0.00017) and Crohn's disease (OR: 1.33, 95% CI: 1.16-1.54; P=0.000035) but not ulcerative colitis. We also describe novel suggestive evidence that TIRAP (OR: 1.16, 95% CI: 1.04-1.30; P=0.007) has a modest effect on risk of IBD. Our analysis, therefore, offers additional evidence that the TLR4 pathway - in this case, TLR4 and its signaling molecule TIRAP - plays a role in susceptibility to IBD.

Beck PL, Xavier R, Wong J, Ezedi I, Mashimo H, Mizoguchi A, Mizoguchi E, Bhan AK, Podolsky DK. · Gastrointestinal Research Group, University of Calgary, Calgary, Alberta, T2N 4N1 Canada. · Am J Physiol Gastrointest Liver Physiol. · Pubmed #14665440 links to  free full text

Abstract: Nitric oxide (NO) is a free radical that is largely produced by three isoforms of NO synthase (NOS): neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). NO regulates numerous processes in the gastrointestinal tract; however, the overall role that NO plays in intestinal inflammation is unclear. NO is upregulated in both ulcerative colitis and Crohn's disease as well as in animal models of colitis. There have been conflicting reports on whether NO protects or exacerbates injury in colitis or is simply a marker of inflammation. To determine whether the site, timing, and level of NO production modulate the effect on the inflammatory responses, the dextran sodium sulfate model of colitis was assessed in murine lines rendered deficient in iNOS, nNOS, eNOS, or e/nNOS by targeted gene disruption. The loss of nNOS resulted in more severe disease and increased mortality, whereas the loss of eNOS or iNOS was protective. Furthermore, concomitant loss of eNOS reversed the susceptibility found in nNOS-/- mice. Deficiencies in specific NOS isoforms led to distinctive alterations of inflammatory responses, including changes in leukocyte recruitment and alterations in colonic lymphocyte populations. The present studies indicate that NO produced by individual NOS isoforms plays different roles in modulating an inflammatory process.

Mizoguchi E, Mizoguchi A, Takedatsu H, Cario E, de Jong YP, Ooi CJ, Xavier RJ, Terhorst C, Podolsky DK, Bhan AK. · Center for the Study of Inflammatory Bowel Disease, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA. · Gastroenterology. · Pubmed #11781288 No free full text.

Abstract: BACKGROUND & AIMS: Tumor necrosis factor (TNF) induces multiple effects including cell proliferation and death by ligation with TNF receptor type II (TNFR2). We studied the role of TNFR2 in chronic inflammation-induced colonic epithelial alteration. METHODS: TNFR2 expression in colonic epithelial cells (CECs) was assessed by ribonuclease protection assay (RPA) and immunohistochemistry (IHC) in patients with inflammatory bowel disease (IBD) and murine colitis models. TNFR2 expression was also analyzed using COLO205 cells. The role of TNFR2 in colonic epithelial homeostasis was examined by generating interleukin 6-deficient TCR alpha KO (alpha IL-6DKO) or TNFR2-deficient TCR alpha (alpha TNFR2DKO) mice. RESULTS: TNFR2 expression was up-regulated in CEC in both human ulcerative colitis and Crohn's disease. In vitro studies showed that TNFR2 expression was up-regulated by a cooperative effect of key proinflammatory cytokines. By RPA, the increased expression of TNFR2 was detectable in TCR alpha KO mice with colitis compared with TCR alpha KO mice without colitis or wild-type mice. In alpha IL-6DKO mice, TNFR2 expression, proliferation, and nuclear factor kappa B activation of CECs were markedly reduced compared with TCR alpha KO mice. alpha TNFR2 mice also showed significantly less colonic epithelial proliferation compared with TCR alpha KO mice. CONCLUSIONS: Expression of TNFR2 is consistently increased on CECs in both murine colitis models as well as patients with IBD. TNFR2 may play an important role in colonic inflammation-associated alteration in the intestinal epithelium.

Cario E, Podolsky DK. · Gastrointestinal Unit, Massachusetts General Hospital, and Harvard Medical School, Center for the Study of Inflammatory Bowel Disease, Boston, Massachusetts 02114, USA. · Infect Immun. · Pubmed #11083826 links to  free full text

Abstract: Initiation and perpetuation of the inflammatory intestinal responses in inflammatory bowel disease (IBD) may result from an exaggerated host defense reaction of the intestinal epithelium to endogenous lumenal bacterial flora. Intestinal epithelial cell lines constitutively express several functional Toll-like receptors (TLRs) which appear to be key regulators of the innate response system. The aim of this study was to characterize the expression pattern of TLR2, TLR3, TLR4, and TLR5 in primary intestinal epithelial cells from patients with IBD. Small intestinal and colonic biopsy specimens were collected from patients with IBD (Crohn's disease [CD], ulcerative colitis [UC]) and controls. Non-IBD specimens were assessed by immunofluorescence histochemistry using polyclonal antibodies specific for TLR2, TLR3, TLR4, and TLR5. Primary intestinal epithelial cells (IEC) of normal mucosa constitutively expressed TLR3 and TLR5, while TLR2 and TLR4 were only barely detectable. In active IBD, the expression of TLR3 and TLR4 was differentially modulated in the intestinal epithelium. TLR3 was significantly downregulated in IEC in active CD but not in UC. In contrast, TLR4 was strongly upregulated in both UC and CD. TLR2 and TLR5 expression remained unchanged in IBD. These data suggest that IBD may be associated with distinctive changes in selective TLR expression in the intestinal epithelium, implying that alterations in the innate response system may contribute to the pathogenesis of these disorders.

Willett CG, Ooi CJ, Zietman AL, Menon V, Goldberg S, Sands BE, Podolsky DK. · Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA. · Int J Radiat Oncol Biol Phys. · Pubmed #10705022 No free full text.

Abstract: PURPOSE: Little data exists in the medical literature describing the response of patients with inflammatory bowel disease (IBD) to abdominal and pelvic irradiation. To clarify the use of this modality in this setting, this study assesses the short- and long-term tolerance of 28 patients with IBD to abdominal and pelvic irradiation. METHODS AND MATERIALS: From 1970 to 1999, 28 patients with IBD (10 patients-Crohn's disease, 18 patients-ulcerative colitis) were identified and underwent external beam abdominal or pelvic irradiation. Mean follow-up time after radiation therapy was 32 months. Patients were treated either by specialized techniques (16 patients) to minimize small and large bowel irradiation or by more conventional approaches (12 patients). Acute and late toxicity was scored. RESULTS: The overall incidence of severe toxicity was 46% (13/28 patients). Six of 28 patients (21%) experienced severe acute toxicity necessitating cessation of radiation therapy. Late toxicity requiring hospitalization or surgical intervention was observed in 8 of 28 patients (29%). One patient experienced both an acute as well as late toxicity. For patients undergoing radiation therapy by conventional approaches, the 5-year actuarial rate of late toxicity was 73%. This figure was 23% for patients treated by specialized techniques (p = 0.02). CONCLUSIONS: Because of the potentially severe toxicity experienced by patients with IBD undergoing abdominal and pelvic irradiation, judicious use of this modality must be employed. Definition of IBD location and activity as well as careful attention to irradiation technique may allow treatment of these patients with acceptable rates of morbidity.