F Bär

Universität zu Lübeck, Lübeck Hansestadt, Schleswig-Holstein, Germany

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Publications (13)46.38 Total impact

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    ABSTRACT: Enteroendocrine cells (EEC) produce neuropeptides, which are crucially involved in the maintenance of the intestinal barrier. Hence, EEC dysfunction is suggested to be involved in the complex pathophysiology of inflammatory bowel disease (IBD), which is characterized by decreased intestinal barrier function. However, the underlying mechanisms for EEC dysfunction are not clear and suitable models for a better understanding are lacking. Here, we demonstrate that Carboxypeptidase E (CPE) is specifically expressed in EEC of the murine colon and ileum and that its deficiency is associated with reduced intestinal levels of Neuropeptide Y (NPY) and Peptide YY (PYY), which are both produced by EEC. Moreover, cpe-/- mice exhibit an aggravated course of DSS-induced chronic colitis compared to wildtype littermates. In addition, we observed elevated mucosal IL-6 and KC transcript levels already at baseline conditions in cpe-/- mice. Moreover, supernatants obtained from isolated intestinal crypts of cpe-/- mice lead to increased IL-6 and KC expression in MODE-K cells in the presence of LPS. This effect was reversible by co-administration of recombinant NPY, suggesting a CPE mediated immunosuppressive effect in the intestines by influencing the processing of specific neuropeptides. In this context, the chemotaxis of bone marrow derived macrophages towards respective supernatants was enhanced. In conclusion, our data point to an anti-inflammatory role of CPE in the intestine by influencing local cytokine levels and thus regulating the migration of myeloid immune cells into the mucosa. These findings highlight the importance of EEC for intestinal homeostasis and propose EEC as potential therapeutic targets in IBD.
    PLoS ONE 07/2014; 9(7):e102347. · 3.53 Impact Factor
  • Journal of Crohn s and Colitis 02/2014; 8:S2. · 3.56 Impact Factor
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    ABSTRACT: Dysregulated energy homeostasis in the intestinal mucosa is frequently observed in patients with ulcerative colitis (UC). Intestinal tissues from these patients have reduced activity of the mitochondrial oxidative phosphorylation (OXPHOS) complex, so mitochondrial dysfunction could contribute to the pathogenesis of UC. However, little is known about the mechanisms by which OXPHOS activity could be altered. We used conplastic mice, which have identical nuclear but different mitochondrial genomes, to investigate activities of the OXPHOS complex. Colitis was induced in C57BL/6J wild-type (B6.B6) and 3 strains of conplastic mice (B6.NZB, B6.NOD, and B6.AKR) by administration of dextran sodium sulphate (DSS) or rectal application of trinitrobenzene sulfonate (TNBS). Colon tissues were collected and analyzed by histopathology, immunohistochemical, and immunoblot analyses; we also measured mucosal levels of ATP and reactive oxygen species, OXPHOS complex activity, and epithelial cell proliferation and apoptosis. We identified mice with increased mucosal OXPHOS complex activities and levels of ATP. These mice developed less-severe colitis following administration of DSS or TNBS than mice with lower mucosal levels of ATP. Colon tissues from these mice also had increased enterocyte proliferation and transcription factor NFκB activity, which have been shown to protect the mucosal barrier-defects in these processes have been associated with inflammatory bowel disease. Variants in mitochondrial DNA that increase mucosal levels of ATP protect mice from colitis. Increasing mitochondrial ATP synthesis in intestinal epithelial could be a therapeutic approach for UC.
    Gastroenterology 07/2013; · 12.82 Impact Factor
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    ABSTRACT: Antigen presentation by intestinal epithelial cells (IEC) is crucial for intestinal homeostasis. Disturbances of major histocompatibility complex class I (MHC I)- and II-related presentation pathways in IEC appear to be involved in an altered activation of CD4(+) and CD8(+) T cells in inflammatory bowel disease. However, a comprehensive analysis of MHC I- and II-enriched compartments in IEC of the small and large bowel in the healthy state as opposed to inflammatory bowel diseases is lacking. The aim of this study was to characterize the subcellular expression of MHC I and II in the endocytic pathway of IEC throughout all parts of the intestinal tract, and to identify differences between the healthy state and inflammatory bowel diseases. Biopsies were taken by endoscopy from the duodenum, jejunum, ileum and colon in healthy individuals (n = 20). In Crohn's disease (CD), biopsies were obtained from the ileum and colon and within the colon from ulcerative colitis (UC) patients (n = 15). Analysis of IEC was performed by immunoelectron microscopy. MHC I and II were identified in early endosomes and multi-vesicular, multi-lamellar, electrondense and vacuolar late endosomes. Both molecules were enriched in multi-vesicular bodies. No differences were found between the distinct parts of the gut axis. In CD and UC the expression of MHC I and II showed a shift from multi-vesicular bodies towards the basolateral membranes. Within the multi-vesicular bodies, MHC I and II moved from internal vesicles to the limiting membranes upon inflammation in CD and UC. MHC I- and II-enriched compartments in IEC were identical in all parts of the small and large bowel. CD and UC appear to modulate the MHC I- and II-related presentation pathways of exogenous antigens in IEC.
    Clinical & Experimental Immunology 05/2013; 172(2):280-9. · 3.28 Impact Factor
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    ABSTRACT: Although a great variety of new drugs have been introduced for the therapy of inflammatory bowel diseases so far, a definite cure of the disease is still out of scope. An anti-inflammatory approach to induce remission followed by maintenance therapy with immunosupressants is still the mainstay of therapy. Thiopurines comprising azathioprine and its active metabolite mercaptopurine as well as tioguanine, are widely used in the therapy of chronic active inflammatory bowel disease (IBD). Their steroid sparing potential and efficacy in remission maintenance are out of doubt. Unfortunately, untoward adverse events are frequently observed and may preclude further administration or be life threatening. This review will focus on new aspects of thiopurine therapy in IBD, its efficacy and safety.
    World Journal of Gastroenterology 03/2013; 19(11):1699-706. · 2.43 Impact Factor
  • Immunobiology 11/2012; 217(11):1147. · 2.81 Impact Factor
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    ABSTRACT: Aneurysms within the visceral arteries are rare. Among these, aneurysms of the splenic artery occur most frequently followed by aneurysms of the hepatic arteries. An early diagnosis is easily missed and almost all patients become symptomatic with an acute rupture associated with high mortality. Here we demonstrate the case of a 76-year-old patient who presented with acute upper abdominal pain accompanied by a single episode of vomiting and pyrexia of 39 °C. Laboratory results presented the picture of an obstructive jaundice without evidence for accompanying pancreatitis. Inflammatory markers were within normal limits at onset, but increased dramatically within the next few days. An acute calculous cholecystitis was diagnosed on abdominal ultrasound whereas gastroscopy revealed no relevant changes. Computed tomography was suspicious for pancreatitis of the head with obstruction of the bile duct. Choledocholithiasis was ruled out by ERCP, but symptoms persisted despite papillotomy. Due to raising inflammatory markers and an ongoing impairment of the patients condition, an abdominal CT scan was repeated which revealed the suspicion of a ruptured aneurysm of the common hepatic artery. At the time of transferral we were able to confirm the diagnosis by contrast-enhanced ultrasound and angiography. The patient was immediately forwarded to surgery due to lack of satisfactory endovascular procedures. In summary, the patient suffered from a ruptured spurial aneurysm of the right gastric artery thereby obstructing the common bile duct. Beside CT scans and angiography, this case documents a pivotal role for contrast-enhanced ultrasound in the work-up of visceral artery aneurysms.
    Zeitschrift für Gastroenterologie 05/2012; 50(5):449-52. · 1.41 Impact Factor
  • Florian Bär, Uwe Roblick, Hendrik Lehnert
    Clinical gastroenterology and hepatology: the official clinical practice journal of the American Gastroenterological Association 03/2011; 9(10):A22. · 5.64 Impact Factor
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    ABSTRACT: Myenteric ganglia are key-structures for the control of intestinal motility and their mRNA expression profiles might be altered under pathological conditions. A drawback of conventional RT-PCR from full-thickness specimens is that gene expression analysis is based on heterogeneously composed tissues. To overcome this problem, laser microdissection combined with real-time RT-PCR can be used to detect and quantify low levels of gene expression in isolated enteric ganglia. Fresh unfixed full-thickness specimens of sigmoid colon were obtained from patients (n = 8) with diseases unrelated to intestinal motility disorders. 10 microm cryo-sections were mounted on membrane-coated slides and ultra-rapidly stained with toluidine blue. Myenteric ganglia were isolated by laser microdissection and catapulting for mRNA isolation. Real-time RT-PCR was performed for selected growth factors, neurotransmitter receptors and specific cell type markers. Collection of 0.5 mm(2) of ganglionic tissue was sufficient to obtain positive RT-PCR results. Collection of 4 mm(2) resulted in ct-values allowing a reliable quantitative comparison of gene expression levels. mRNA analysis revealed that neurotrophic growth factor, neurotrophin-3, serotonin receptor 3A, PGP 9.5 and S100 beta are specifically expressed in myenteric ganglia of the human colon. Laser microdissection combined with real-time RT-PCR is a novel technique to reliably detect and quantify site-specific expression of low-abundance mRNAs (e.g. growth factors, neurotransmitter receptors) related to the human enteric nervous system. This technical approach expands the spectrum of available tools to characterize enteric neuropathologies underlying human gastrointestinal motility disorders at the molecular biological level.
    Neurogastroenterology and Motility 10/2009; 22(2):168-72, e52. · 2.94 Impact Factor
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    ABSTRACT: Abstract Clinical studies have shown that probiotics influence gastrointestinal motility, e.g. Escherichia coli Nissle 1917 (EcN) (Mutaflor) proved to be at least as efficacious as lactulose and more potent than placebo in constipated patients. As the underlying mechanisms are not clarified, the effects of EcN culture supernatants on human colonic motility were assessed in vitro. Human colonic circular smooth muscle strips (n = 94, 17 patients) were isometrically examined in an organ bath and exposed to different concentrations of EcN supernatants. Contractility responses were recorded under (i) native conditions, (ii) electrical field stimulation (EFS), (iii) non-adrenergic non-cholinergic conditions, and (iv) enteric nerve blockade by tetrodotoxin (TTX). As concentrations of acetic acid were increased in EcN supernatants, contractility responses to acetic acid were additionally tested. EcN supernatants significantly increased the maximal tension forces both at low and high concentrations. Neither blockade of both adrenergic and cholinergic nerves nor application of TTX abolished these effects. EFS-induced contractility responses were not altered after exposure to EcN supernatants. Acetic acid elicited effects comparable to EcN supernatants only under TTX conditions. EcN supernatants modulate in vitro contractility of the human colon. As neither partial nor TTX blockade of enteric nerves abolished these effects, EcN supernatants appear to enhance colonic contractility by direct stimulation of smooth muscle cells. Active metabolites may include other substances than acetic acid, as acetic acid only partially resembled the effects elicited by EcN supernatants. The data provide a rationale for therapeutical application of probiotics in gastrointestinal motility disorders.
    Neurogastroenterology and Motility 03/2009; 21(5):559-66, e16-7. · 2.94 Impact Factor
  • Zeitschrift für Gastroenterologie 08/2007; 45(08). · 1.67 Impact Factor
  • M Böttner, F Bär, T Wedel
    Zeitschrift für Gastroenterologie 07/2007; 45(6):575-8. · 1.67 Impact Factor
  • M Böttner, F Bär, T Wedel
    Zeitschrift für Gastroenterologie 06/2007; 45(6):575-578. · 1.67 Impact Factor

Publication Stats

50 Citations
46.38 Total Impact Points


  • 2009–2014
    • Universität zu Lübeck
      • • Institut für Anatomie
      • • Department of Internal Medicine I
      Lübeck Hansestadt, Schleswig-Holstein, Germany
  • 2011–2013
    • University Medical Center Schleswig-Holstein
      Kiel, Schleswig-Holstein, Germany
  • 2012
    • Universitätsklinikum Schleswig - Holstein
      Kiel, Schleswig-Holstein, Germany
  • 2007–2009
    • Christian-Albrechts-Universität zu Kiel
      • Anatomisches Institut
      Kiel, Schleswig-Holstein, Germany