Recent data suggest that neurotrophic factors from the enteric nervous system are involved in intestinal epithelial barrier regulation. In this context the glial cell line-derived neurotrophic factor ...(GDNF) was shown to affect gut barrier properties in vivo directly or indirectly by largely undefined processes in a model of inflammatory bowel disease (IBD). We further investigated the potential role and mechanisms of GDNF in the regulation of intestinal barrier functions. Immunostaining of human gut specimen showed positive GDNF staining in enteric neuronal plexus and in enterocytes. In Western blots of the intestinal epithelial cell lines Caco2 and HT29B6, significant amounts of GDNF were detected, suggesting that enterocytes represent an additional source of GDNF. Application of recombinant GDNF on Caco2 and HT29B6 cells for 24 h resulted in significant epithelial barrier stabilization in monolayers with immature barrier functions. Wound-healing assays showed a significantly faster closure of the wounded areas after GDNF application. GDNF augmented cAMP levels and led to significant inactivation of p38 MAPK in immature cells. Activation of p38 MAPK signaling by SB-202190 mimicked GDNF-induced barrier maturation, whereas the p38 MAPK activator anisomycin blocked GDNF-induced effects. Increasing cAMP levels had adverse effects on barrier maturation, as revealed by permeability measurements. However, increased cAMP augmented the proliferation rate in Caco2 cells, and GDNF-induced proliferation of epithelial cells was abrogated by the PKA inhibitor H89. Our data show that enterocytes represent an additional source of GDNF synthesis. GDNF contributes to wound healing in a cAMP/PKA-dependent manner and promotes barrier maturation in immature enterocytes cells by inactivation of p38 MAPK signaling.
The behaviour of turbulent transport in the weak-wind, stably-stratified, boundary layer over land is examined in terms of the non-stationarity of the wind field using measurements from three field ...programs. These field programs include towers ranging from 12 to 20 m in height and an extensive horizontal network of sonic anemometers. The relationship of the friction velocity to the stratification and non-stationary submeso motions is investigated from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected partly due to enhancement of the turbulence by submeso motions. Cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases in the downward transport of momentum.
An impaired intestinal epithelial barrier (IEB) is a hallmark in the pathogenesis of inflammatory bowel diseases (IBD), including ulcerative colitis and Crohn’s disease. Most of the IBD patients are ...treated with anti‐inflammatory reagents including glucocorticoids, anti TNFα (tumor necrosis factor alpha) antibodies and mesasalazine. While the Immune‐modulating effects of those therapies are well documented, we hypothesized whether there are direct effects of those reagents on enterocytes and the IEB.
To address this hypothesis we used Caco2 cells as well as 2D and 3D murine organoids and performed analysis of intestinal epithelial barrier function. Inflammation‐induced alterations were mimicked using cytomix for 24h (TNFα, Interleukin 1 beta and Interferon gamma). The enterocytes were treated with 100ng/ml anti‐TNFα antibody Infliximab, 1mM prednisolone or 5mM mesasalazine, respectively following the challenge with cytomix. Epithelial permeability as revealed by measurements of 4kDa FITC Dextran flux and of transepithelial electric resistance showed that Infliximab and a pre‐incubation with prednisolone for 24h attenuated inflammation‐induced breakdown of the IEB. This was not the case after application of mesasalazine or a simultaneous incubation of prednisolone. The functional changes in intestinal epithelial barrier function following incubation with Cytomix were paralleled by alterations in the expression of “leaky” tight junction protein Claudin2, as revealed by Western blots. Furthermore, immunostainings demonstrated an altered distribution of barrier sealing proteins such as Claudin1, Desmoglein2 and E‐Cadherin. All of these effects were blocked by infliximab and prednisolone.
In summary, our data indicate that infliximab and prednisolone have direct effects on the IEB that may contribute to the efficacy in the treatment of IBD.
In the stable boundary layer, thermal submesofronts (TSFs) are detected during the Shallow Cold Pool experiment in the Colorado plains, Colorado, USA in 2012. The topography induces TSFs by forming ...two different air layers converging on the valley-side wall while being stacked vertically above the valley bottom. The warm-air layer is mechanically generated by lee turbulence that consistently elevates near-surface temperatures, while the cold-air layer is thermodynamically driven by radiative cooling and the corresponding cold-air drainage decreases near-surface temperatures. The semi-stationary TSFs can only be detected, tracked, and investigated in detail when using fibre-optic distributed sensing (FODS), as point observations miss TSFs most of the time. Neither the occurrence of TSFs nor the characteristics of each air layer are connected to a specific wind or thermal regime. However, each air layer is characterized by a specific relationship between the wind speed and the friction velocity. Accordingly, a single threshold separating different flow regimes within the boundary layer is an oversimplification, especially during the occurrence of TSFs. No local forcings or their combination could predict the occurrence of TSFs except that they are less likely to occur during stronger near-surface or synoptic-scale flow. While classical conceptualizations and techniques of the boundary layer fail in describing the formation of TSFs, the use of spatially continuous data obtained from FODS provide new insights. Future studies need to incorporate spatially continuous data in the horizontal and vertical planes, in addition to classic sensor networks of sonic anemometry and thermohygrometers to fully characterize and describe boundary-layer phenomena.
Submesoscale motions within the stable boundary layer were detected during the Shallow Cold Pool Experiment conducted in the Colorado plains, Colorado, U.S.A. in 2012. The submesoscale motion ...consisted of two air layers creating a well-defined front with a sharp temperature gradient, and further-on referred to as a thermal submesofront (TSF). The semi-stationary TSFs and their advective velocities are detected and determined by the fibre-optic distributed-sensing (FODS) technique. An objective detection algorithm utilizing FODS measurements is able to detect the TSF boundary, which enables a detailed investigation of its spatio–temporal statistics. The novel approach in data processing is to conditionally average any parameter depending on the distance between a TSF boundary and the measurement location. By doing this, a spatially-distributed feature like TSFs can be characterized by point observations and processes at the TSF boundary can be investigated. At the TSF boundary, the air layers converge, creating an updraft, strong static stability, and vigorous mixing. Further, the TSF advective velocity of TSFs is an order of magnitude lower than the mean wind speed. Despite being gentle, the topography plays an important role in TSF formation. Details on generating mechanisms and implications of TSFs on the stable boundary layer are discussed in Part 2.
Introduction
Major postoperative bleeding (mPOB) is the most common complication after bariatric surgery. Its intesity varies from self-limiting to life-threatening situations. Comprehensive ...decision-making and treatment strategies are mandatory but not established yet.
Methods
We retrospectively analyzied our prospectively collected database of our bariatric patients during 2012–2022. The primary study endpoint was major postoperative bleeding (mPOB) defined as hemoglobin drop > 2 g/dl or clinically relevant bleeding requiring intervention (transfusion, endoscopy or surgery). Secondary endpoints were overall complications according to Clavien-Dindo-Classification and comprehensive-complication-index (CCI).
Results
We identified 1017 patients, of whom 667 underwent gastric bypass (GB) and 350 sleeve gastrectomy (SG). Major postoperative bleeding occured in 39 patients (total 3.8%; 5.1% after GB and 2.3% after SG). Patients with mPOB were more often diagnosed with type 2 diabetes (
p
= 0.039), chronic kidney failure (
p
= 0.013) or received antiplatelet drug treatment (
p
= 0.003). The interval from detection to intervention within 24 h was 92.1% (35/39). Blood transfusions were necessary in 20/39 cases (total 51.3%; 45.2% after GB and 75% after SG;
p
= 0.046). Luminal bleeding only occured after GB (19/31; 61.3%), while all mPOB after SG were intraabdominal (
p
= 0.002). Reoperations were performed in 21/39 (total 53.8%; 48.4% after GB and 75% after SG;
p
= 0.067). CCI in patients with mPOB was 34.7 overall, with 31.2 after GB and 47.9 after SG (
p
= 0.005).
Conclusion
The clinical appearance of mPOB depends on the type of surgery with severe bleedings after SG. We suggest a surgery first approach for mPOB after SG and an endoscopy first approach after GB.
Graphical Abstract
Key points
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A specific therapy to treat capillary leakage in systemic inflammation and sepsis is not available at present.
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Recent studies demonstrated that reduced cAMP levels in endothelial ...cells contribute to inflammation‐induced breakdown of the endothelial barrier.
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The present study demonstrates that systemically applied phosphodiesterase‐4 inhibitors to increase endothelial cAMP are effective to prevent and to treat capillary leakage followed by improved microcirculation in a rodent model of systemic inflammation.
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These data suggest a highly clinically relevant and applicable approach to stabilize capillary leakage in sepsis and systemic inflammation.
In sepsis and systemic inflammation, increased microvascular permeability and consecutive breakdown of microcirculatory flow significantly contribute to organ failure and death. Evidence points to a critical role of cAMP levels in endothelial cells to maintain capillary endothelial barrier properties in acute inflammation. However, approaches to verify this observation in systemic models are rare. Therefore we tested here whether systemic application of the phosphodiesterase‐4‐inhibitors (PD‐4‐Is) rolipram or roflumilast to increase endothelial cAMP was effective to attenuate capillary leakage and breakdown of microcirculatory flow in severe lipopolysaccharide (LPS)‐induced systemic inflammation in rats. Measurements of cAMP in mesenteric microvessels demonstrated significant LPS‐induced loss of cAMP levels which was blocked by application of rolipram. Increased endothelial cAMP by application of either PD‐4‐I rolipram or roflumilast led to stabilization of endothelial barrier properties as revealed by measurements of extravasated FITC‐albumin in postcapillary mesenteric venules. Accordingly, microcirculatory flow in mesenteric venules was significantly increased following PD‐4‐I treatment and blood gas analyses indicated improved metabolism. Furthermore application of PD‐4‐I after manifestation of LPS‐induced systemic inflammation and capillary leakage therapeutically stabilized endothelial barrier properties as revealed by significantly reduced volume resuscitation for haemodynamic stabilization. Accordingly microcirculation was significantly improved following treatment with PD‐4‐Is. Our results demonstrate that inflammation‐derived loss of endothelial cAMP contributes to capillary leakage which was blocked by systemic PD‐4‐I treatment. Therefore these data suggest a highly clinically relevant and applicable approach to stabilize capillary leakage in sepsis and systemic inflammation.
Impaired intestinal epithelial barrier (IEB) function with loss of desmosomal junctional protein desmoglein 2 (DSG2) is a hallmark in the pathogenesis of inflammatory bowel disease (IBD). While ...previous studies have reported that glial cell line-derived neurotrophic factor (GDNF) promotes IEB function, the mechanisms are poorly understood. We hypothesized that GDNF is involved in the loss of DSG2, resulting in impaired IEB function as seen in IBD. In the inflamed intestine of patients with IBD, there was a decrease in GDNF concentrations accompanied by a loss of DSG2, changes of the intermediate filament system, and increased phosphorylation of p38 MAPK and cytokeratins. DSG2-deficient and RET-deficient Caco2 cells revealed that GDNF specifically recruits DSG2 to the cell borders, resulting in increased DSG2-mediated intercellular adhesion via the RET receptor. Challenge of Caco2 cells and enteroids with proinflammatory cytokines as well as dextran sulfate sodium-induced (DSS-induced) colitis in C57Bl/6 mice led to impaired IEB function with reduced DSG2 mediated by p38 MAPK-dependent phosphorylation of cytokeratins. GDNF blocked all inflammation-induced changes in the IEB. GDNF attenuates inflammation-induced impairment of IEB function caused by the loss of DSG2 through p38 MAPK-dependent phosphorylation of cytokeratin. The reduced GDNF in patients with IBD indicates a disease-relevant contribution to the development of IEB dysfunction.
Inflammation-induced reduction of intestinal desmosomal cadherin Desmoglein 2 (Dsg2) is linked to changes of tight junctions (TJ) leading to impaired intestinal epithelial barrier (IEB) function by ...undefined mechanisms. We characterized the interplay between loss of Dsg2 and upregulation of pore-forming TJ protein Claudin2. Intraperitoneal application of Dsg2-stablising Tandem peptide (TP) attenuated impaired IEB function, reduction of Dsg2 and increased Claudin2 in DSS-induced colitis in C57Bl/6 mice. TP blocked loss of Dsg2-mediated adhesion and upregulation of Claudin2 in Caco2 cells challenged with TNFα. In Dsg2-deficient Caco2 cells basal expression of Claudin2 was increased which was paralleled by reduced transepithelial electrical resistance and by augmented phosphorylation of AKT
under basal conditions. Inhibition of phosphoinositid-3-kinase proved that PI-3-kinase/AKT-signaling is critical to upregulate Claudin2. In immunostaining PI-3-kinase dissociated from Dsg2 under inflammatory conditions. Immunoprecipitations and proximity ligation assays confirmed a direct interaction of Dsg2 and PI-3-kinase which was abrogated following TNFα application. In summary, Dsg2 regulates Claudin2 expression by sequestering PI-3-kinase to the cell borders in intestinal epithelium.
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