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Fluck K.,University of Duisburg - Essen | Fluck K.,Physiologisches Institute | Breves G.,Physiologisches Institute | Fandrey J.,University of Duisburg - Essen | Winning S.,University of Duisburg - Essen
Mucosal Immunology | Year: 2016

Dendritic cells (DCs) serve as a bridge between innate and adaptive immunity and help to maintain intestinal homeostasis. Inflammatory bowel disease (IBD) is associated with dysregulation of the mucosal immune response. The concomitant hypoxic inflammation in IBD will activate the transcription factor hypoxia-inducible factor-1 (HIF-1) to also drive gene expression in DCs. Recent studies have described a protective role for epithelial HIF-1 in mouse models of IBD. We investigated the role of HIF-1 in DC function in a dextran sodium sulfate (DSS)-induced model of murine colitis. Wild-type and dendritic cell-specific HIF-1α knockout mice were treated with 3% DSS for 7 days. Knockout of HIF-1α in DCs led to a significantly larger loss of body weight in mice with DSS-induced colitis than in control mice. Knockout mice exhibited more severe intestinal inflammation with increased levels of proinflammatory cytokines and enhanced production of mucin. Induction of regulatory T cells (Tregs) was impaired, and the number of forkhead box P3 (Foxp3) Tregs was diminished by dendritic HIF-1α knockout. Our findings demonstrate that in DCs HIF-1α is necessary for the induction of sufficient numbers of Tregs to control intestinal inflammation.

Heger J.,Physiologisches Institute | Warga B.,Physiologisches Institute | Meyering B.,Physiologisches Institute | Abdallah Y.,Physiologisches Institute | And 3 more authors.
Journal of Cellular Physiology | Year: 2011

Transforming growth factor β (TGFβ) expression is induced in the myocardium during transition from compensated hypertrophy to heart failure. In cardiomyocytes, stimulation with TGFβ results in restricted contractile function and enhanced apoptosis. Nitric oxide (NO) also induces apoptosis and influences cardiac function. Therefore, we wanted to know whether NO is causally involved in TGFβ-induced apoptosis. In isolated ventricular cardiomyocytes of adult rat incubation with TGFβ 1 increased NO release which was inhibited by NOS inhibitor ETU but not with iNOS inhibitor (1400W) or nNOS inhibitor (TFA). In addition, TGFβ-induced apoptosis was blocked with ETU and ODQ, but not with 1400W or TFA. The consequent assumption that endothelial NOS is involved in TGFβ-induced NO formation and apoptosis was supported by increased phosphorylation of eNOS at serine 1177 and by the fact that TGFβ did not increase NO release in eNOS KO mice. Furthermore, TGFβ-induced apoptosis, NO formation, SMAD binding activity and SMAD2 phosphorylation were blocked by a TGFβ receptor antagonist, but only apoptosis and NO formation could be blocked with ETU. Expression of SMAD7 was increased after TGFβ stimulation and blocked with TGFβ receptor antagonist but not after blocking NO synthase with ETU. Conclusion: In cardiomyocytes TGFβ-induced apoptosis is mediated via TGFβ receptor activation that concomitantly activates SMAD transcription factors and the eNOS/NO/sGC pathway. Both of these pathways are needed for apoptosis induction by TGFβ. This reveals a new pathway of cardiac NO release and identifies NO as a possible contributor to heart failure progression mediated by TGFβ. © 2010 Wiley-Liss, Inc.

Huber K.,Physiologisches Institute | Zeller E.,University of Hohenheim | Rodehutscord M.,University of Hohenheim
Poultry Science | Year: 2015

Dietary phosphorus (P) is known as a main modulator of phosphate (Pi) transporter expression. The effect of supplemented mineral P with or without phytase on protein expression of two sodium-dependent Pi (NaPi) transporters and a calcium channel was studied in the small intestine of broilers. Thirty-six broilers were randomly assigned to six different diets at 15 days of age. Two levels of total P (tP, adjusted by monocalcium phosphate (MCP) supplementation), 0.39% (BD-) and 0.47% (BD+) were fed until day 25; and at each tP level, three levels of phytase were used with 0, 500, and 12,500 FTU/kg of an E. coli phytase. Mucosa samples from jejunum and ileum were taken and apical membranes were isolated by MgCl2 precipitation. Protein expression of NaPi IIb, NaPi type III (PiT1) and the calcium channel TRPV6 were semiquantitatively measured by Western blotting and jejunal mucosal phytase activity by measurement of Pi release. The jejunal NaPi IIb transporter was expressed with two distinct bands, which were modulated differently by diet. NaPi IIb Band1 increased (P < 0.05) and Band2 decreased (P < 0.05) with phytase supplementation but was not affected by MCP supplementation. This inverse modulation of Band1 and Band2 was significantly related to the amount of net absorbed P with higher expression of Band1 at higher amounts of net absorbed P. In addition, a second Pi transporter, PiT1, was detected in which ileal expression decreased (P < 0.05) in response to higher phytase supplementation. The expression of the calcium channel TRPV6 was increased in BD+ groups. A trend for an interaction between MCP and phytase supplementation on mucosal phytase activity was observed (P = 0.079) with a decrease in activity when BD+ with 12,500 FTU/kg phytase was fed. Chicken intestinal epithelial cells responded to dietary supplemented phytase and MCP by changing the Pi transporter expression in apical membranes. In conclusion, availability of Pi is most likely the key modulator of transporter protein expression. However, a contribution of lower inositol phosphates generated by phytases and other phosphatases may also be relevant. © 2015 Poultry Science Association Inc.

Schwab A.,University of Munster | Nechyporuk-Zloy V.,University of Glasgow | Gassner B.,Physiologisches Institute | Schulz C.,Ludwig Maximilians University of Munich | And 4 more authors.
Journal of Cellular Physiology | Year: 2012

Calcium-sensitive potassium channels (K Ca3.1) are expressed in virtually all migrating cells. Their activity is required for optimal cell migration so that their blockade leads to slowing down. K Ca3.1 channels must be inserted into the plasma membrane in order to elicit their physiological function. However, the plasma membrane of migrating cells is subject to rapid recycling by means of endo- and exocytosis. Here, we focussed on the endocytic internalization and the intracellular transport of the human isoform hK Ca3.1. A hK Ca3.1 channel construct with an HA-tag in the extracellularly located S3-S4 linker was transfected into migrating transformed renal epithelial MDCK-F cells. Channel internalization was visualized and quantified with immunofluorescence and a cell-based ELISA. Movement of hK Ca3.1 channel containing vesicles as well as migration of MDCK-F cells were monitored by means of time lapse video microscopy. hK Ca3.1 channels are endocytosed during migration. Most of the hK Ca3.1 channel containing vesicles are moving at a speed of up to 2μm/sec in a microtubule-dependent manner towards the front of MDCK-F cells. Our experiments indicate that endocytosis of hK Ca3.1 channels is clathrin-dependent since they colocalize with clathrin adaptor proteins and since it is impaired when a C-terminal dileucine motif is mutated. The C-terminal dileucine motif is also important for the subcellular localization of hK Ca3.1 channels in migrating cells. Mutated channels are no longer concentrated at the leading edge. We therefore propose that recycling of hK Ca3.1 channels contributes to their characteristic subcellular distribution in migrating cells. © 2011 Wiley Periodicals, Inc.

Grunberg W.,University Utrecht | Dobbelaar P.,University Utrecht | Breves G.,Physiologisches Institute
British Journal of Nutrition | Year: 2013

Hypophosphataemia is frequently encountered in dairy cows during early lactation. Although supplementation of P is generally recommended, controversy exists over the suitability of oral P supplementation in animals with decreased or absent rumen motility. Since the effects of transruminal P absorption and the reticular groove reflex on the absorption kinetics of P are not well understood, it is unclear in how far treatment efficacy of oral P supplementation is affected by decreased rumen motility. Phosphate absorption was studied in six phosphate-depleted dairy cows fitted with rumen cannulas and treated with test solutions containing either NaH2PO4 or CaHPO4 with acetaminophen. Each animal was treated orally, intraruminally and intra-abomasally in randomised order. Absorption kinetics of P were studied and compared with the absorption kinetics of acetaminophen, a marker substance only absorbed from the small intestine. Intra-abomasal treatment with NaH2PO4 resulted in the most rapid and highest peaks in plasma inorganic P (Pi) concentration. Oral and intraruminal administration of NaH2PO4 resulted in similar increases in plasma Pi concentration from 4 to 7Â h in both groups. Treatment with NaH2PO4 caused more pronounced peaks in plasma Pi concentration compared with CaHPO4. Neither transruminal P absorption nor the reticular groove reflex affected P absorption kinetics as determined by comparing plasma concentration-time curves of P and acetaminophen after administration of 1Â m-phosphate salt solutions. It is concluded that oral treatment with NaH2PO4 but not CaHPO4 is effective in supplementing P in hypophosphataemic cows with adequate rumen motility. Decreased rumen motility is likely to hamper the efficacy of oral phosphate treatment. Copyright © The Authors 2013.

Holtmann W.C.,Physiologisches Institute | Stumpp M.,Physiologisches Institute | Stumpp M.,Leibniz Institute of Marine Science | Stumpp M.,Gothenburg University | And 6 more authors.
Marine Biology | Year: 2013

Experimental ocean acidification leads to a shift in resource allocation and to an increased [HCO3 -] within the perivisceral coelomic fluid (PCF) in the Baltic green sea urchin Strongylocentrotus droebachiensis. We investigated putative mechanisms of this pH compensation reaction by evaluating epithelial barrier function and the magnitude of skeleton (stereom) dissolution. In addition, we measured ossicle growth and skeletal stability. Ussing chamber measurements revealed that the intestine formed a barrier for HCO3 - and was selective for cation diffusion. In contrast, the peritoneal epithelium was leaky and only formed a barrier for macromolecules. The ossicles of 6 week high CO2-acclimatised sea urchins revealed minor carbonate dissolution, reduced growth but unchanged stability. On the other hand, spines dissolved more severely and were more fragile following acclimatisation to high CO2. Our results indicate that epithelia lining the PCF space contribute to its acid-base regulation. The intestine prevents HCO3 - diffusion and thus buffer leakage. In contrast, the leaky peritoneal epithelium allows buffer generation via carbonate dissolution from the surrounding skeletal ossicles. Long-term extracellular acid-base balance must be mediated by active processes, as sea urchins can maintain relatively high extracellular [HCO3 -]. The intestinal epithelia are good candidate tissues for this active net import of HCO3 - into the PCF. Spines appear to be more vulnerable to ocean acidification which might significantly impact resistance to predation pressure and thus influence fitness of this keystone species. © 2013 Springer-Verlag Berlin Heidelberg.

Leonhard-Marek S.,Physiologisches Institute
Archiv fur Lebensmittelhygiene | Year: 2012

Stress as a physiological response to a changed environment serves as a short-term defence mechanism. In the long term, however, stress can severely impair health and production parameters. Within the udder, stress has an influence on all functions from milk synthesis to the processes of milk secretion and milk ejection. In addition, stress acts upon the defence mechanisms of the mammary gland. © M. & H. Schaper GmbH & Co.

Schluter K.-D.,Physiologisches Institute | Schulz R.,Physiologisches Institute | Schreckenberg R.,Physiologisches Institute
Frontiers in Physiology | Year: 2015

Induction and activation of arginase is among the fastest responses of the heart to ischemic events. Induction of arginase expression and enzyme activation under ischemic conditions shifts arginine consumption from nitric oxide formation (NO) to the formation of ornithine and urea. In the heart such a switch in substrate utilization reduces the impact of the NO/cGMP-pathway on cardiac function that requires intact electromechanical coupling but at the same time it induces ornithine-dependent pathways such as the polyamine metabolism. Both effects significantly reduce the recovery of heart function during reperfusion and thereby limits the success of reperfusion strategies. In this context, changes in arginine consumption trigger cardiac remodeling in an unfavorable way and increases the risk of arrhythmia, specifically in the initial post-ischemic period in which arginase activity is dominating. However, during the entire ischemic period arginase activation might be a meaningful adaptation that is specifically relevant for reperfusion following prolonged ischemic periods. Therefore, a precise understanding about the underlying mechanism that leads to arginase induction as well as of it's mechanistic impact on post-ischemic hearts is required for optimizing reperfusion strategies. In this review we will summarize our current understanding of these processes and give an outlook about possible treatment options for the future. © 2015 Schlüter, Schulz and Schreckenberg.

Suffrian K.,Physiologisches Institute | Schulz K.G.,Leibniz Institute of Marine Science | Gutowska M.A.,Physiologisches Institute | Riebesell U.,Leibniz Institute of Marine Science | Bleich M.,Physiologisches Institute
New Phytologist | Year: 2011

To understand the influence of changing surface ocean pH and carbonate chemistry on the coccolithophore Emiliania huxleyi, it is necessary to characterize mechanisms involved in pH homeostasis and ion transport. Here, we measured effects of changes in seawater carbonate chemistry on the fluorescence emission ratio of BCECF (2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein) as a measure of intracellular pH (pHi). Out of equilibrium solutions were used to differentiate between membrane permeation pathways for H+, CO2 and HCO3 -. Changes in fluorescence ratio were calibrated in single cells, resulting in a ratio change of 0.78 per pHi unit. pHi acutely followed the pH of seawater (pHe) in a linear fashion between pHe values of 6.5 and 9 with a slope of 0.44 per pHe unit. pHi was nearly insensitive to changes in seawater CO2 at constant pHe and HCO3 -. An increase in extracellular HCO3 - resulted in a slight intracellular acidification. In the presence of DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid), a broad-spectrum inhibitor of anion exchangers, E. huxleyi acidified irreversibly. DIDS slightly reduced the effect of pHe on pHi. The data for the first time show the occurrence of a proton permeation pathway in E. huxleyi plasma membrane. pHi homeostasis involves a DIDS-sensitive mechanism. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Klein A.,Physiologisches Institute | Skrandies W.,Physiologisches Institute
Brain Topography | Year: 2013

For data preprocessing and artefact removal in an ERP experiment we were confronted with the question how blink artefacts can be detected reliably, even in the absence of usable electrooculogram (EOG) data. We propose an objective and quantitative method for the automatic detection of eyeblink artefacts from raw data using extreme value statistics, with a p-value acting as a threshold parameter. For testing the method, we used 29 channel electroencephalogram recordings of 55 healthy subjects. A total 7,700 s of EEG were analysed. The proposed method was found to detect blink artefacts reliably, showing that extreme value statistics can be employed to detect blink artefacts, even in the absence of EOG recordings. © 2013 Springer Science+Business Media New York.

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