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Role of pH-sensing receptors in colitis.
Hausmann, M, Seuwen, K, de Vallière, C, Busch, M, Ruiz, PA, Rogler, G
Pflugers Archiv : European journal of physiology. 2024;(4):611-622
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Abstract
Low pH in the gut is associated with severe inflammation, fibrosis, and colorectal cancer (CRC) and is a hallmark of active inflammatory bowel disease (IBD). Subsequently, pH-sensing mechanisms are of interest for the understanding of IBD pathophysiology. Tissue hypoxia and acidosis-two contributing factors to disease pathophysiology-are linked to IBD, and understanding their interplay is highly relevant for the development of new therapeutic options. One member of the proton-sensing G protein-coupled receptor (GPCR) family, GPR65 (T-cell death-associated gene 8, TDAG8), was identified as a susceptibility gene for IBD in a large genome-wide association study. In response to acidic extracellular pH, GPR65 induces an anti-inflammatory response, whereas the two other proton-sensing receptors, GPR4 and GPR68 (ovarian cancer G protein-coupled receptor 1, OGR1), mediate pro-inflammatory responses. Here, we review the current knowledge on the role of these proton-sensing receptors in IBD and IBD-associated fibrosis and cancer, as well as colitis-associated cancer (CAC). We also describe emerging small molecule modulators of these receptors as therapeutic opportunities for the treatment of IBD.
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[Weight loss and maintenance with a tailored healthy diet based on the energy density of food items].
Erdmann, J, Hausmann, M
MMW Fortschritte der Medizin. 2023;(10):42-44
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Iron Prevents Hypoxia-Associated Inflammation Through the Regulation of Nuclear Factor-κB in the Intestinal Epithelium.
Simmen, S, Cosin-Roger, J, Melhem, H, Maliachovas, N, Maane, M, Baebler, K, Weder, B, Maeyashiki, C, Spanaus, K, Scharl, M, et al
Cellular and molecular gastroenterology and hepatology. 2019;(2):339-355
Abstract
BACKGROUND & AIMS Hypoxia-associated pathways influence the development of inflammatory bowel disease. Adaptive responses to hypoxia are mediated through hypoxia-inducible factors, which are regulated by iron-dependent hydroxylases. Signals reflecting oxygen tension and iron levels in enterocytes regulate iron metabolism. Conversely, iron availability modulates responses to hypoxia. In the present study we sought to elucidate how iron influences the responses to hypoxia in the intestinal epithelium. METHODS Human subjects were exposed to hypoxia, and colonic biopsy specimens and serum samples were collected. HT-29, Caco-2, and T84 cells were subjected to normoxia or hypoxia in the presence of iron or the iron chelator deferoxamine. Changes in inflammatory gene expression and signaling were assessed by quantitative polymerase chain reaction and Western blot. Chromatin immunoprecipitation was performed using antibodies against nuclear factor (NF)-κB and primers for the promoter of tumor necrosis factor (TNF) and interleukin (IL)1β. RESULTS Human subjects presented reduced levels of ferritin in the intestinal epithelium after hypoxia. Hypoxia reduced iron deprivation-associated TNF and IL1β expression in HT-29 cells through the induction of autophagy. Contrarily, hypoxia triggered TNF and IL1β expression, and NF-κB activation in Caco-2 and T84 cells. Iron blocked autophagy in Caco-2 cells, while reducing hypoxia-associated TNF and IL1β expression through the inhibition of NF-κB binding to the promoter of TNF and IL1β. CONCLUSIONS Hypoxia promotes iron mobilization from the intestinal epithelium. Hypoxia-associated autophagy reduces inflammatory processes in HT-29 cells. In Caco-2 cells, iron uptake is essential to counteract hypoxia-induced inflammation. Iron mobilization into enterocytes may be a vital protective mechanism in the hypoxic inflamed mucosa.
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Clinical relevance of IgG antibodies against food antigens in Crohn's disease: a double-blind cross-over diet intervention study.
Bentz, S, Hausmann, M, Piberger, H, Kellermeier, S, Paul, S, Held, L, Falk, W, Obermeier, F, Fried, M, Schölmerich, J, et al
Digestion. 2010;81(4):252-64
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Plain language summary
Environmental factors are thought to play a part in the development of or exacerbation of symptoms in Crohn's disease (CD), and patients often implicate food as a contributing factor. Immunoglobulin E (IgE) food reactions can be rare in IBD and immunoglobulin G (IgG) testing can be controversial, this study set out to compare IgG antibody reactions in 79 CD patients and 20 healthy individuals. The pilot study measured IgG levels against 271 foods in the blood. It then went on to measure stool frequency, abdominal pain and general well-being following a 6 week specific elimination diet (based on foods identified by the IgG testing) or a 6 week sham diet. 23 participants were included in the follow on 12 week, cross-over double blinded study. Eosinophil-derived neurotoxin (EDN) in stool was also measured to evaluate disease activity. The pilot study showed a significantly higher IgG reaction in the CD patients. In the follow-up study there was a decrease in stool frequency, abdominal pain and general well-being during the specific diet compared to the sham diet. EDN was found to decrease in both the specific and sham diet. It was concluded that IgG antibodies may contribute to CD but the mechanism is still not clear.
Abstract
BACKGROUND Environmental factors are thought to play an important role in the development of Crohn's disease (CD). Immune responses against auto-antigens or food antigens may be a reason for the perpetuation of inflammation. METHODS In a pilot study, 79 CD patients and 20 healthy controls were examined for food immunoglobulin G (IgG). Thereafter, the clinical relevance of these food IgG antibodies was assessed in a double-blind cross-over study with 40 patients. Based on the IgG antibodies, a nutritional intervention was planned. The interferon (IFN)gamma secretion of T cells was measured. Eosinophil-derived neurotoxin was quantified in stool. RESULTS The pilot study resulted in a significant difference of IgG antibodies in serum between CD patients and healthy controls. In 84 and 83% of the patients, respectively, IgG antibodies against processed cheese and yeast were detected. The daily stool frequency significantly decreased by 11% during a specific diet compared with a sham diet. Abdominal pain reduced and general well-being improved. IFNgamma secretion of T cells increased. No difference for eosinophil-derived neurotoxin in stool was detected. CONCLUSION A nutritional intervention based on circulating IgG antibodies against food antigens showed effects with respect to stool frequency. The mechanisms by which IgG antibodies might contribute to disease activity remain to be elucidated.
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Spatial association of homologous pericentric regions in human lymphocyte nuclei during repair.
Monajembashi, S, Rapp, A, Schmitt, E, Dittmar, H, Greulich, KO, Hausmann, M
Biophysical journal. 2005;(3):2309-22
Abstract
Spatial positioning of pericentric chromosome regions in human lymphocyte cell nuclei was investigated during repair after H(2)O(2)/L-histidine treatment. Fifteen to three-hundred minutes after treatment, these regions of chromosomes 1, 15, and X were labeled by fluorescence in situ hybridization. The relative locus distances (LL-distances), the relative distances to the nuclear center (LC-distances), and the locus-nuclear center-locus angles (LCL-angles) were measured in approximately 5000 nuclei after two-dimensional microscopy. Experimental frequency histograms were compared to control data from untreated stimulated and quiescent (G(0)) nuclei and to a theoretical two-dimensional projection from random points. Based on the frequency distributions of the LL-distances and the LCL-angles, an increase of closely associated labeled regions was found shortly after repair activation. For longer repair times this effect decreased. After 300 min the frequency distribution of the LL-distances was found to be compatible with the random distance distribution again. The LL-distance frequency histograms for quiescent nuclei did not significantly differ from the theoretical random distribution, although this was the case for the stimulated control of chromosomes 15 and X. It may be inferred that, concerning the distances, homologous pericentric regions appear not to be randomly distributed during S-phase, and are subjected to dynamic processes during replication and repair.