Macromolecular Permeability Research Articles

Intestinal Epithelial AMPK Regulates Paracellular Electrolyte Flux and Electrogenic Ion Transport Responses in Mouse Colon

Ion transport within the colonic epithelium is crucial to maintain colonic homeostasis. During pathological states such as intestinal inflammation, alteration of ion transport processes contributes to the development of diarrhea and constipation. These pathways are tightly regulated by expression and localization to ensure fluid balance. AMP‐Activated Protein Kinase (AMPK) is a highly conserved energy‐sensing kinase that has previously been shown to regulate ion channels and transporters such as CFTR and NKCC1, in both intestinal epithelium and other epithelia. The aim of this study was to specifically test the impact of AMPK activity on ion flux across intestinal epithelia by utilizing a tissue‐specific knockout mouse model lacking both AMPK‐α catalytic isoforms.MethodsIntestinal epithelial cell‐specific knockout of AMPK activity (AMPKαΔIEC KO) was achieved by crossing Prkaa1 and Prkaa2 floxed mice (AMPKαfl/fl) with Villin‐Cre mice. For Ussing chamber experiments, large intestinal segments were stripped of the serosal layer and the mucosal layer was mounted in Ussing chambers containing Kreb's Ringer's buffer. Chloride secretion was stimulated using Forskolin (300μM) applied bilaterally, followed by Carbachol (10μM) applied basolaterally. For immunostaining, whole intestinal tissue was isolated and fixed in 4% paraformaldehyde overnight, washed with 1X PBS, and stored in 30% sucrose in 1X until OCT embedding. 5μm frozen sections of intestinal tissues were sliced and mounted onto glass slides.ResultsWe previously demonstrated AMPKαΔIEC KO mice do not have a barrier defect indicated by macromolecular intestinal permeability, histological analysis, and response to dextran sulfate sodium (DSS) compared to AMPKαfl/fl mice. We next determined if AMPK alters electrolye permeability in different regions of the large intestine. Indeed, loss of AMPK decreased transepithelial electrical resistance (TEER) in mouse proximal colon (35.21 ± 3.3 Ω·cm2, n = 6–7, p = 0.0007). Conversely, AMPKαΔIEC KO mice exhibited an increase in basal TEER in the distal colon (62.5 ± 4.5 Ω·cm2, n = 2–3, p = 0.2683), although this was not statistically significant. We next tested if AMPKαΔIEC KO mice exhibited changes in electrogenic ion transport by intestinal region. Preliminary evidence in the cecum indicated increased electrogenic ion transport responses to carbachol and Forskolin in AMPKαΔIEC KO mice (n = 1–3) while only forskolin‐dependent ion transport was increased in the distal colon (n = 2–3). In the proximal colon, Ca2+‐dependent ion transport was increased two‐fold (n = 6–7, p = 0.1131) while there was no alteration in cAMP‐dependent ion transport (n = 6–7). To determine if these region‐specific effects were associated with changes in transporter expression, colonic sections were stained for the Na+‐K+‐Cl− Cotransporter 1 (NKCC1) as a key contributor to electrogenic ion secretion. NKCC1 expression in AMPKαΔIEC KO mice was similar to that of AMPKαfl/fl mice (n = 2–3).ConclusionsAMP‐activated protein kinase mediates region‐specific maintenance of the intestinal barrier and regulation of electrogenic ion transport in mice.Support or Funding InformationNIH 2R01DK091281 (DFM)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The function and mechanism of preactivated thiomers in triggering epithelial tight junctions opening

As a unique macromolecular permeation enhancer, thiolated polymers (thiomers), especially the preactivated thiomers, have demonstrated great merits in oral delivery of protein/peptide drugs by triggering epithelial tight junctions (TJs) opening. However, the underlying molecular mechanism remains unclear. To clarify this issue, preactivated thiomers were synthesized and their TJs opening function as well as signaling pathways on MDCK and Caco-2 cell monolayers was investigated. The results showed that preactivated thiomers could reduce TEER and increase the permeation of Na-Flu and FITC-Insulin over 2-fold and 4-fold on MDCK monolayers, respectively, indicating their huge potential as macromolecular permeation enhancers. The signaling pathway study showed that intracellular PTK Src but not FAK, involved in the TJs opening by claudin-4 disruption. Src activation was based on interaction between thiol group of thiomers and cysteine-riched Src upstream membrane receptors, EGFR and IGFR. The deep comprehension of the thiomers-mediated TJs opening mechanisms provides goodness in application of protein/peptide drugs for the oral delivery.

Effects of Selenium in the Microcirculation of Fructose-Fed Hamsters

Background and Aims: Fructose intake is directly related to vascular dysfunction and it is a risk factor for the development of metabolic and cardiovascular diseases, such as obesity, diabetes, and hypertension. Selenium, a component of antioxidant enzymes, improves hyperglycemia and vascular function in diabetic animals. The aim of this study was to evaluate the effects of dietary selenium supplementation on microcirculatory and metabolic parameters of fructose-fed hamsters. Methods and Results: Male hamsters (Mesocricetus auratus) had their drinking water substituted or not by 10% fructose solution for 60 days, during which their microcirculatory function was evaluated in the cheek pouch preparation. Blood glucose and serum insulin levels were also tested. Microcirculatory responses to acetylcholine (an endothelium-dependent vasodilator) and to sodium nitroprusside (SNP, an endothelium-independent vasodilator), and macromolecular permeability increase induced by a 30-min ischemia/reperfusion (I/R) procedure, showed that endothelium-dependent and independent vasodilatation was significantly increased in animals that had high selenium supplementation, in both the control and fructose-fed groups. Selenium supplementation protected against plasma leakage induced by I/R in all control and fructose-fed groups. Conclusion: Our results indicate that dietary selenium supplementation reduces microvascular dysfunction by increasing endothelial-dependent and independent dilatation and reducing macromolecular permeability increase in fructose-fed animals.

Altered expression of TIAM1 in endotoxin-challenged airway epithelial cells and rodent septic models.

In sepsis, reorganization of the actin cytoskeleton in the epithelium during inflammation will lead to a breakdown of epithelial barrier integrity, and contribute to the pathogenesis of sepsis, but the exact changes of various components regulating the actin cytoskeleton pathway remain unclear. We used lipopolysaccharide (LPS) challenged primary epithelial cells cultured at the air-liquid interface (ALI) to mimic epithelial barrier dysfunction during sepsis. Then we detected differential expression of T-lymphoma invasion and metastasis 1 (TIAM1) gene in lung epithelial cells and septic models. LPS induced barrier dysfunction in human tracheobronchial epithelial cells (HTBEs) as measured by statistically significant changes in ionic and macromolecular permeability. We observed differential expression of TIAM1 gene. The protein expression of TIAM1 was decreased after LPS challenge, in human bronchial epithelial cells. Furthermore, the expression levels of both TIAM1 mRNA and protein were decreased in lungs of septic rodent models. Given that expression levels of TIAM1 have been associated with mortality among sepsis patients, our findings have the potential for the development of diagnostic and treatment strategies relevant for patient management.

Theoretical Insights into the Retinal Dynamics of Vascular Endothelial Growth Factor in Patients Treated with Ranibizumab, Based on an Ocular Pharmacokinetic/Pharmacodynamic Model.

Neovascular age-related macular degeneration (wet AMD) results from the pathological angiogenesis of choroidal capillaries, which leak fluid within or below the macular region of the retina. The current standard of care for treating wet AMD utilizes intravitreal injections of anti-VEGF antibodies or antibody fragments to suppress ocular vascular endothelial growth factor (VEGF) levels. While VEGF suppression has been demonstrated in wet AMD patients by serial measurements of free-VEGF concentrations in aqueous humor samples, it is presumed that anti-VEGF molecules also permeate across the inner limiting membrane (ILM) of the retina as well as the retinal pigmented epithelium (RPE) and suppress VEGF levels in the retina and/or choroidal regions. The latter effects are inferred from serial optical coherence tomography (OCT) measurements of fluid in the retinal and sub-retinal spaces. In order to gain theoretical insights to the dynamics of retinal levels of free-VEGF following intravitreal injection of anti-VEGF molecules, we have extended our previous two-compartment pharmacokinetic/pharmacodynamic (PK/PD) model of ranibizumab-VEGF suppression in vitreous and aqueous humors to a three-compartment model that includes the retinal compartment. In the new model, reference values for the macromolecular permeability coefficients between retina and vitreous ( pILM) and between retina and choroid ( pRPE) were estimated from PK data obtained in rabbit. With these values, the three-compartment model was used to re-analyze the aqueous humor levels of free-VEGF obtained in wet AMD patients treated with ranibizumab and to compare them to the simulated retinal levels of free-VEGF, including the observed variability in PK and PD. We have also used the model to explore the impact of varying pILM and pRPE to assess the case in which an anti-VEGF molecule is impermeable to the ILM and to assess the potential effects of AMD pathology on the RPE barrier. Our simulations show that, for the reference values of pILM and pRPE, the simulated duration of VEGF suppression in the retina is approximately 50% shorter than the observed duration of VEGF suppression in the aqueous humor, a finding that may explain the short duration of suppressed disease activity in the "high anti-VEGF demand" patients reported by Fauser and Muether ( Br. J. Ophthalmol. 2016, 100, 1494-1498 ). At 10-fold lower values of pRPE, the durations of VEGF suppression in the retina and aqueous humor are comparable. Lastly we have used the model to explore the impact of dose and binding parameters on the duration and depth of VEGF suppression in the aqueous and retinal compartments. Our simulations with the three-compartment PK/PD model provide new insights into inter-patient variability in response to anti-VEGF therapy and offer a mechanistic framework for developing treatment regimens and molecules that may prolong the duration of retinal VEGF suppression.

Marked differences in tight junction composition and macromolecular permeability among different intestinal cell types

Mammalian small intestinal (SI) tight junctions (TJ) link epithelial cells to one another and function as aperm selective barrier, strictly modulating the passage of ions and macromolecules through the “pore” and “leak” pathways, respectively, thereby preventing absorption of harmful compounds and microbes while allowing regulated transport of nutrients and electrolytes. SI epithelial permeability is ascribed primarily to properties of TJ between adjoiningenterocytes (ENT), because there is almost no information on TJ composition and paracellular permeability of non‐enterocyte cell types that constitute a small but significant fraction of the intestinal epithelia. In the current study we directed murine intestinal crypts to form specialized organoids highly enrichedin stem cells (ISC), absorptive ENTs, secretory goblet (GOB) or Paneth cells(PAN). Morphological and morphometriccharacteristics of these cells in organoids were similar to those in vivo. Expression of certain TJ genes varied with cell type. Occludin and tricellulin levels were high in both ISC and PAN organoids, while claudin‐1, junctional adhesion molecule‐1, and cingulin were greatest mainly in PAN. Claudin‐2 was greatest in ISC and claudin‐7 expression was greatest in ENT organoids. In contrast, claudin‐15, zonula occludens 1 (ZO‐1) and e‐cadherin distribution were relatively homogeneous among cell types. Immunofluorescent staining showed that e‐cadherin and claudin‐7 marked mainly the basolateral membrane, while claudin‐2, ZO‐1 and occludin resided apically. Remarkably, organoids enrichedin ENTs and GOBs, respectively were 3.7‐fold and 3.4‐fold more permeable to 4 kda dextran thanthose enriched in ISCs (P<0.05). Similarly, ENT and GOB were 2.9 and2.6‐fold more permeable to 10 kda dextran compared to ISC organoids. The trend was similar (>2‐fold)for ENT and GOB vs. PAN organoids for both 4 and 10 kda dextran flux (P<0.05). As was expected, for all cell types 10 kda dextran flux was significantly lower than 4 kda (P < 0.05). A time course of dextran flux in ENT and PAN organoids revealed that 4 kda dextran entered the lumen of ENT by 10 min and highest intensity was observed by 30 min (P<0.05). In contrast, dextran flux was nearly absent in PAN organoids, regardless of time point. Additionally, the TJ regulator larazotide prevented the ~10‐fold increases in dextran flux induced by the TJ disrupter AT1002 in both ISC and ENT organoids (P < 0.05), indicating that AT1002 non‐selectively increases permeability. Lastly, dedifferentiation of mature ENTs results inreacquisition of ISC‐like characteristics in TJ composition and dextranpermeability, suggesting that post‐differentiation properties of TJs are not hard wired. In conclusion, differentiation of adult intestinal stem cells into mature secretory and absorptive cell types causes marked, but potentially reversible, changes in TJ composition, resulting in enhanced macromolecular permeability of the TJ leak pathway between ENTs and between goblet cells. This work advances our understanding of how cell differentiation affects the paracellularpathway of epithelia.Support or Funding InformationSupported by NSF Grants No. IOS‐1121049 (RPF) and 1456673 (RPF) and by NIH Grant R01‐DK‐102934 (NG).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Marked differences in tight junction composition and macromolecular permeability among different intestinal cell types

BackgroundMammalian small intestinal tight junctions (TJ) link epithelial cells to one another and function as a permselective barrier, strictly modulating the passage of ions and macromolecules through the pore and leak pathways, respectively, thereby preventing the absorption of harmful compounds and microbes while allowing regulated transport of nutrients and electrolytes. Small intestinal epithelial permeability is ascribed primarily to the properties of TJs between adjoining enterocytes (ENTs), because there is almost no information on TJ composition and the paracellular permeability of nonenterocyte cell types that constitute a small but significant fraction of the intestinal epithelia.ResultsHere we directed murine intestinal crypts to form specialized organoids highly enriched in intestinal stem cells (ISCs), absorptive ENTs, secretory goblet cells, or Paneth cells. The morphological and morphometric characteristics of these cells in organoids were similar to those in vivo. The expression of certain TJ proteins varied with cell type: occludin and tricellulin levels were high in both ISCs and Paneth cells, while claudin-1, -2, and -7 expression was greatest in Paneth cells, ISCs, and ENTs, respectively. In contrast, the distribution of claudin-15, zonula occludens 1 (ZO-1), and E-cadherin was relatively homogeneous. E-cadherin and claudin-7 marked mainly the basolateral membrane, while claudin-2, ZO-1, and occludin resided in the apical membrane. Remarkably, organoids enriched in ENTs or goblet cells were over threefold more permeable to 4 and 10 kDa dextran compared to those containing stem and Paneth cells. The TJ-regulator larazotide prevented the approximately tenfold increases in dextran flux induced by the TJ-disrupter AT1002 into organoids of different cell types, indicating that this ZO toxin nonselectively increases permeability. Forced dedifferentiation of mature ENTs results in the reacquisition of ISC-like characteristics in TJ composition and dextran permeability, suggesting that the post-differentiation properties of TJs are not hardwired.ConclusionsDifferentiation of adult intestinal stem cells into mature secretory and absorptive cell types causes marked, but potentially reversible, changes in TJ composition, resulting in enhanced macromolecular permeability of the TJ leak pathway between ENTs and between goblet cells. This work advances our understanding of how cell differentiation affects the paracellular pathway of epithelia.

A high-throughput microtissue platform to probe endothelial function in vitro.

A critical role of vascular endothelium is as a semi-permeable barrier, dynamically regulating the flux of solutes between blood and the surrounding tissue. Existing platforms that quantify endothelial function in vitro are either significantly throughput limited or overlook physiologically relevant extracellular matrix (ECM) interactions and thus do not recapitulate in vivo function. Leveraging droplet microfluidics, we developed a scalable platform to measure endothelial function in nanoliter-volume, ECM-based microtissues. In this study, we describe our high-throughput method for fabricating endothelial-coated collagen microtissues that incorporate physiologically relevant cell-ECM interactions. We showed that the endothelial cells had characteristic morphology, expressed tight junction proteins, and remodeled the ECM via compaction and deposition of basement membrane. We also measured macromolecular permeability using two optical modalities, and found the cell layers: (1) had permeability values comparable to in vivo measurements and (2) were responsive to physiologically-relevant modulators of endothelial permeability (TNF-α and TGF-β). This is the first demonstration, to the authors' knowledge, of high-throughput assessment (n > 150) of endothelial permeability on natural ECM. Additionally, this technology is compatible with standard cell culture equipment (e.g. multi-well plates) and could be scaled up further to be integrated with automated liquid handling systems and automated imaging platforms. Overall, this platform recapitulates the functions of traditional transwell inserts, but extends application to high-throughput studies and introduces new possibilities for interrogating cell-cell and cell-matrix interactions.

Notch signaling is impaired during inflammation in a Lunatic Fringe-dependent manner

The blood-brain barrier (BBB) assures brain homeostasis through the specialized function of brain endothelial cells (BECs). Dysfunction of the BBB due to inflammatory processes is associated with several neurological disorders, including multiple sclerosis (MS). Understanding the mechanisms that underlie these processes may ultimately lead to new therapeutic strategies to restore BBB function, thereby fighting disease progression. In this study, we demonstrate for the first time a critical role of the Notch signaling pathway in the function of the BBB under resting and inflammatory conditions. Inhibition of the Notch signaling, either by a γ-secretase inhibitor or by genetic ablation of endothelial NOTCH, led to BBB dysfunction in vitro as evidenced by reduced transendothelial electrical resistance (TEER), altered localization and loss of endothelial junction molecules and enhanced macromolecular permeability. Inflamed BECs showed impaired Notch signaling as indicated by reduced level of the downstream targets HES-1 and HES-5. Notably, barrier function was further reduced when the Notch signaling was inhibited under inflammatory conditions, suggesting an additive effect of the Notch signaling and inflammation in BECs. In contrast, inducible overexpression of Notch-intracellular domain 1 (NICD1) rescued the detrimental effect caused by inflammation. Furthermore, we provide evidence that inflammation reduced the expression of the glycosyltransferase Lunatic Fringe (LFNG), a known positive regulator of Notch glycosylation and signaling, thereby leading to disrupted barrier function of BECs. Together, our data demonstrate the functional importance of the conserved Notch signaling pathway in control of the brain endothelial barrier and shed light on the role of LFNG in the regulation of Notch glycosylation and signaling in the adult brain vasculature in both health and disease.

Induction of precocious intestinal maturation in T-cell deficient athymic neonatal rats.

AIMTo investigate whether gut maturation could be induced precociously in an athymic T-cell deficient neonatal rat model.METHODSFourteen day-old athymic (nude) rats (NIH-Foxn1rnu) were gavaged with either phytohaemagglutinin - a lectin from red kidney beans (PHA); trypsin - a protease (Prot); or water - vehicle (control) as a single dose on one day or once a day for 3-day. The nude rats were either nurtured by their mothers or cross-fostered by conventional foster dams of the Sprague-Dawley strain from days 3-5 after birth. At 17 d of age, 72 h after administration of the first treatment, intestinal macromolecular permeability was tested in vivo, prior to euthanasia, after which blood and gut organs were sampled.RESULTSProvocation with both, PHA and protease, resulted in increased gut growth and maturation in nude rat pups independent of nursing. Foetal-type enterocytes were replaced by non-vacuolated adult-type enterocytes in the distal small intestine epithelium. Decreased intestinal macromolecular permeability (gut closure) was observed, with reduced permeability markers (BIgG and BSA, P < 0.001) in circulation. Increased pancreatic function, with an increased trypsin to protein ratio in pancreas homogenates, was observed independent of nursing in the nude pups. Immunostaining showed the presence of a few CD3+-cells in the intestinal mucosa of the nude pups. The number of CD3+-cells remained unaltered by provocation and no differences were observed between the nursing sets. Growth and vitality of the nude pups were dependent on nurturing, since cross-fostering by conventional dams increased their macromolecular absorptive capacity (BSA, P < 0.05), as well as their passive immunity (RIgG, P < 0.05).CONCLUSIONPrecocious gut maturation can be induced by enteral provocation in athymic rat pups, similarly to in euthymic pups, thus showing an independence from thymus-derived T-cells.

Stress induces more serious barrier dysfunction in follicle-associated epithelium than villus epithelium involving mast cells and protease-activated receptor-2

Psychological stress has been associated with intestinal epithelial hyperpermeability, the basic process in various functional and organic bowel diseases. In the present study, we aimed to clarify the differences and underlining mechanisms in stress-induced barrier disruption in functionally and structurally distinct epitheliums, including the villus epithelium (VE) and follicle-associated epithelium (FAE), a specialized epithelium overlaid the domes of Peyer’s lymphoid follicles. Employing an Ussing Chamber system, the epithelial permeability was assessed in rats following water avoidance stress (WAS) in vivo and in mucosa tissues exposed to corticotropin-releasing factor (CRF) ex vivo. Decreased transepithelial resistance (TER) and increased paracellular and transcellular macromolecular permeability in colon, ileal VE and FAE had been observed in WAS rats and in CRF-exposed mucosa. Especially, the barrier dysfunction was more serious in the FAE. Moreover, WAS upregulated the expression of mast cell tryptase and protease-activated receptor-2 (PAR2), which positively correlated with epithelial conductance. Mast cell stabilizer cromolyn sodium obviously alleviated the barrier disruption induced by WAS in vivo and CRF in vitro. Serine protease inhibitor aprotinin and FUT-175, and selective PAR2 antagonist ENMD-1068 effectively inhibited the CRF-induced FAE hyperpermeability. Altogether, it concluded that the FAE was more susceptible to stress, and the mast cells and PAR2 signaling played crucial roles in this process.

Stably engineered nanobubbles and ultrasound - An effective platform for enhanced macromolecular delivery to representative cells of the retina.

Herein we showcase the potential of ultrasound-responsive nanobubbles in enhancing macromolecular permeation through layers of the retina, ultimately leading to significant and direct intracellular delivery; this being effectively demonstrated across three relevant and distinct retinal cell lines. Stably engineered nanobubbles of a highly homogenous and echogenic nature were fully characterised using dynamic light scattering, B-scan ultrasound and transmission electron microscopy (TEM). The nanobubbles appeared as spherical liposome-like structures under TEM, accompanied by an opaque luminal core and darkened corona around their periphery, with both features indicative of efficient gas entrapment and adsorption, respectively. A nanobubble +/- ultrasound sweeping study was conducted next, which determined the maximum tolerated dose for each cell line. Detection of underlying cellular stress was verified using the biomarker heat shock protein 70, measured before and after treatment with optimised ultrasound. Next, with safety to nanobubbles and optimised ultrasound demonstrated, each human or mouse-derived cell population was incubated with biotinylated rabbit-IgG in the presence and absence of ultrasound +/- nanobubbles. Intracellular delivery of antibody in each cell type was then quantified using Cy3-streptavidin. Nanobubbles and optimised ultrasound were found to be negligibly toxic across all cell lines tested. Macromolecular internalisation was achieved to significant, yet varying degrees in all three cell lines. The results of this study pave the way towards better understanding mechanisms underlying cellular responsiveness to ultrasound-triggered drug delivery in future ex vivo and in vivo models of the posterior eye.

Contribution of muscarinic receptors to in vitro and in vivo effects of Ruscus extract

The objectives of this study were to evaluate, in vitro and in vivo, the contribution of muscarinic receptors to the effects of Ruscus extract.Ruscus extract was tested in competition binding experiments at recombinant human muscarinic receptors, heterologous expressed in Chinese Hamster Ovary (CHO) cells and in cellular assays measuring Ca2+ liberation and activator protein-1 (AP-1) reporter gene activation. The impact of muscarinic blockade on prolonged treatment outcome was evaluated using the hamster cheek pouch (HCP) microcirculation examining macromolecular permeability increase induced by histamine or ischemia/reperfusion (I/R), mean arteriolar and venular diameters, functional capillary density and I/R-induced leukocyte rolling and sticking.Ruscus extract exhibited affinities for muscarinic receptor subtypes at a range of 50–100μg/ml and behaved as partial agonist at human recombinant M1 and M3 receptors for Ca2+ liberation, confirmed in an AP-1 reporter gene assay. In the HCP model, topical application of atropine completely or partially blocked Ruscus extract-induced reductions of histamine- and I/R-induced increases of macromolecular permeability and leukocyte-endothelium interaction.Our results showed that Ruscus extract in vitro binds and activates different subtypes of muscarinic receptors and in vivo its anti-inflammatory effects are, at least partially, mediated via muscarinic receptors.

The low molecular weight fraction of commercial human serum albumin induces acetylation of α-tubulin and reduces transcytosis in retinal endothelial cells

It has long been appreciated that the microtubule network plays a critical role in endothelial cell function. Chemical inhibition of tubulin polymerization has been shown to drastically increases endothelial permeability via interactions with the actin cytoskeleton. Conversely, stabilization of microtubules significantly decreases vascular permeability. The purpose of this investigation was to determine if the low molecular weight fraction of commercial 5% human serum albumin (LMWF5A) alters endothelial cell cytoskeletal dynamics and function. To investigate this, human retinal endothelial cells (HREC) were treated with LMWF5A and the acetylation of α-tubulin was determined by immunofluorescent staining and immunoblotting. In addition, permeability assays were performed to evaluate functional changes. We found that HREC treated with LMWF5A exhibit a rapid increase in the amount and distribution of acetylated α-tubulin. This was accompanied by a reduction in macromolecular permeability. Calcium depletion and inhibition of PI3-kinase reduced LMWF5A-induced acetylation while p38 MAPK inhibition potentiated this effect. These findings suggest that LMWF5A mediates changes in the microtubule network and reduces transcytosis in HREC.

IL-1α mediates cellular cross-talk in the airway epithelial mesenchymal trophic unit

ABSTRACTThe bronchial epithelium and underlying fibroblasts form an epithelial mesenchymal trophic unit (EMTU) which controls the airway microenvironment. We hypothesized that cell-cell communication within the EMTU propagates and amplifies the innate immune response to respiratory viral infections.EMTU co-culture models incorporating polarized (16HBE14o-) or differentiated primary human bronchial epithelial cells (HBECs) and fibroblasts were challenged with double-stranded RNA (dsRNA) or rhinovirus.In the polarized EMTU model, dsRNA affected ionic but not macromolecular permeability or cell viability. Compared with epithelial monocultures, dsRNA-stimulated pro-inflammatory mediator release was synergistically enhanced in the basolateral compartment of the EMTU model, with the exception of IL-1α which was unaffected by the presence of fibroblasts. Blockade of IL-1 signaling with IL-1 receptor antagonist (IL-1Ra) completely abrogated dsRNA-induced basolateral release of mediators except CXCL10. Fibroblasts were the main responders to epithelial-derived IL-1 since exogenous IL-1α induced pro-inflammatory mediator release from fibroblast but not epithelial monocultures. Our findings were confirmed in a differentiated EMTU model where rhinovirus infection of primary HBECs and fibroblasts resulted in synergistic induction of basolateral IL-6 that was significantly abrogated by IL-1Ra. This study provides the first direct evidence of integrated IL-1 signaling within the EMTU to propagate inflammatory responses to viral infection.

High-mobility group box 1 impairs airway epithelial barrier function through the activation of the RAGE/ERK pathway.

Recent studies have indicated that high-mobility group box 1 protein (HMGB1) and the receptor for advanced glycation end-products (RAGE) contribute to the pathogenesis of asthma. However, whether the activation of the HMGB1/RAGE axis mediates airway epithelial barrier dysfunction remains unknown. Thus, the aim of this study was to examine the effects of HMGB1 and its synergistic action with interleukin (IL)-1β on airway epithelial barrier properties. We evaluated the effects of recombinant human HMGB1 alone or in combination with IL-1β on ionic and macromolecular barrier permeability, by culturing air-liquid interface 16HBE cells with HMGB1 to mimic the differentiated epithelium. Western blot analysis and immunofluorescence staining were utilized to examine the level and structure of major junction proteins, namely E-cadherin, β-catenin, occludin and claudin-1. Furthermore, we examined the effects of RAGE neutralizing antibodies and mitogen-activated protein kinase (MAPK) inhibitors on epithelial barrier properties in order to elucidate the mechanisms involved. HMGB1 increased FITC-dextran permeability, but suppressed epithelial resistance in a dose-and time-dependent manner. HMGB1-mediated barrier hyperpermeability was accompanied by a disruption of cell-cell contacts, the selective downregulation of occludin and claudin-1, and the redistribution of E-cadherin and β-catenin. HMGB1 in synergy with IL-1β induced a similar, but greater barrier hyperpermeability and induced the disruption of junction proteins. Furthermore, HMGB1 elicited the activation of the RAGE/extracellular signal-related kinase (ERK)1/2 signaling pathway, which correlated with barrier dysfunction in the 16HBE cells. Anti-RAGE antibody and the ERK1/2 inhibitor, U0126, attenuated the HMGB1-mediated changes in barrier permeability, restored the expression levels of occludin and claudin-1 and pevented the redistribution of E-cadherin and β-catenin. Taken together, the findings of our study demonstrate that HMGB1 is capable of inducing potent effects on epithelial barrier function and that RAGE/ERK1/2 is a key signaling pathway involved in the crosstalk between formations of junction proteins and epithelial barrier dysfunction.

In the absence of overt urothelial damage, chondroitinase ABC digestion of the GAG layer increases bladder permeability in ovariectomized female rats.

Loss of integrity of the protective impermeability barrier in the urothelium has been identified as significant in bladder dysfunction. In this study, we tested the theory that the luminal layer of glycosaminoglycans (GAG) serves as an important component of barrier function. The peptide polycation protamine sulfate (PS), 1 mg/ml, was instilled intravesically for 10 min into rat bladders. Chondroitinase ABC (ChABC), 63 IU/ml, was instilled into an additional six rats for 30 min to digest the GAG layer. Unmanipulated controls and sham-injected controls were also performed. After 24 h, the rats were euthanized, the bladders were removed, and permeability was assessed in the Ussing chamber and by diffusion of FITC-labeled dextran (4 kDa) to measure macromolecular permeability. The status of tight junctions was assessed by immunofluorescence and electron microscopy. In control and sham treated rat bladders, the transepithelial electrical resistance were means of 2.5 ± 1.1 vs. 2.6 ± 1.1 vs 1.2 ± 0.5 and 1.01 ± 0.7 kΩ·cm(2) in the PS-treated and ChABC-treated rat bladders (P = 0.0016 and P = 0.0039, respectively). Similar differences were seen in dextran permeability. Histopathology showed a mild inflammation following PS treatment, but the ChABC-treated bladders were indistinguishable from controls. Tight junctions generally remained intact. ChABC digestion alone induced bladder permeability, confirming the importance of the GAG layer to bladder barrier function and supports that loss of the GAG layer seen in bladder biopsies of interstitial cystitis patients could be a significant factor producing symptoms for at least some interstitial cystitis/painful bladder syndrome patients.

Microcirculatory effects of zinc on fructose-fed hamsters

Background and aimsFructose is a major dietary component directly related to vascular dysfunction and diseases such as obesity, diabetes, and hypertension. Zinc is considered a non-pharmacological alternative for treating diabetes due to its antioxidant and hyperglycemia-lowering effects in diabetic animals. Therefore, the aim of this study was to evaluate the effects of dietary zinc supplementation on the microcirculatory parameters of fructose-fed hamsters. Methods and ResultsMale hamsters (Mesocricetus auratus) were fed drinking water substituted by 10% fructose solution for 60 days, whereas control animals were fed drinking water alone. Their microcirculatory function was evaluated using cheek pouch preparation, as well as their blood glucose and serum insulin levels. Their microcirculatory responses to acetylcholine (ACh, an endothelium-dependent vasodilator) and to sodium nitroprusside (SNP, an endothelium-independent vasodilator) as well as the increase in macromolecular permeability induced by 30 min of ischemia/reperfusion (I/R) were noted. Endothelium-dependent vasodilation was significantly increased in control animals with high zinc supplementation compared to the groups without zinc supplementation. Zinc was able to protect against plasma leakage induced by I/R in all control and fructose-fed groups, although the microvascular permeability was higher in animals fed drinking water substituted by 10% fructose solution compared to those fed filtered drinking water alone. ConclusionOur results indicate that dietary zinc supplementation can improve microvascular dysfunction by increasing endothelial-dependent dilatation and reducing the increase in macromolecular permeability induced by I/R in fructose-fed animals.

α-Tocopherol Improves Microcirculatory Dysfunction on Fructose Fed Hamsters.

Fructose, an everyday component of western diet associated to chronic hyperglycemia and enhanced free radical production, impairs endothelial function and supplementation with antioxidants might improve it. In this study we investigated if vitamin E could reverse the microvascular damage elicited by fructose. Male Syrian golden hamsters drank either 10% fructose solution (F) or filtered water (C), combined with three concentrations of vitamin E in their chows [zero, normal (VE) or 5X (5XVE)] during 60 days. Microvascular reactivity in response to topical application of acetylcholine (Ach; endothelium-dependent vasodilator) or sodium nitroprusside (SNP; endothelium-independent vasodilator) and macromolecular permeability increase induced by either 30 min ischemia followed by reperfusion (I/R) or topical application of histamine (5 μM) were assessed using the cheek pouch preparation. Compared to controls (drinking filtered water), fructose-drinking animals showed decreased vasodilatation to acetylcholine in all concentrations tested (-56.2% for 10-9M, -53.9% for 10-7M and -43.7% for 10-5M). On the other hand, vitamin E supplementation resulted in increased responses for both water and fructose drinking groups (177.4% for F vs. F/5XVE and 241.6% for C vs. C/5XVE for 10-5M Ach). Endothelial-independent vasodilatation explored by topical application of SNP was restored and even enhanced with the supplementation of 5X vitamin E in both groups (80.1% for F vs. F/5XVE; 144.2% for C vs. C/5XVE; 3.4% of difference for C/5XVE vs. F/5XVE on 10-5M SNP). The number of leaky sites after I/R and histamine stimuli in vitamin E supplemented animals decreased (-25.1% and -15.3% for F vs. F/5XVE; and -21.7% and -16% of leaky sites comparing C vs. C/5XVE, respectively for I/R and histamine stimuli) pointing to tightening of the endothelial barrier for macromolecular permeability. Our results strongly suggest that vitamin E could improve the endothelial function and permeability barrier and also reverse impairments elicited by sugar overload.

MP81-01 A NOVEL ROLE OF EPITHELIAL PERMEABILITY IN VISCERAL ORGAN CROSS TALK

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Female Urology1 Apr 2015MP81-01 A NOVEL ROLE OF EPITHELIAL PERMEABILITY IN VISCERAL ORGAN CROSS TALK Alexander Parker, Ehsan Mohommadi, Karl Tyler, Robert E. Hurst, and Beverley Greenwood-Van Meerveld Alexander ParkerAlexander Parker More articles by this author , Ehsan MohommadiEhsan Mohommadi More articles by this author , Karl TylerKarl Tyler More articles by this author , Robert E. HurstRobert E. Hurst More articles by this author , and Beverley Greenwood-Van MeerveldBeverley Greenwood-Van Meerveld More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.2879AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Painful bladder syndrome (PBS) and irritable bowel syndrome (IBS) are often comorbid conditions thought to be due to visceral organ cross communication. It is our overall hypothesis that changes in epithelial permeability may represent a novel mechanism for visceral organ crosstalk. In support, we previously found that following acute bladder damage, there was a marked increase in the permeability of both the bladder and the undamaged colon. However, it is currently unknown whether damage to the colon will alter permeability in the undamaged bladder. The goal of the current study was to test the hypothesis that an acute colitis increases permeability in the undamaged bladder. METHODS Experiments were performed in fasted, ovariectomized (OVX) female Sprague Dawley rats (n=24). An acute colitis was produced by an enema of trinitrobenzene sulfonic acid (TNBS) (50 mg/kg) with saline-enema treated rats serving as controls. The severity of colonic damage was assessed using an in vivo disease activity index (DAI) score and via post mortem histology. Colon and bladder tissue were harvested after 1 day or 3 days. Bladder and colonic tissue was mounted into modified Ussing chambers and bathed in Kreb's solution at 37°C. After a stabilization period, permeability was assessed electrophysiologically via transepithelial resistance (TEER) and via the flux of a macromolecular marker (fluorescein isothiocynate-dextrin [FITC-4 KD). RESULTS Compared to saline-treated controls, TNBS-treated rats showed a significantly (P<0.05) higher DAI on days 1 and 3. Exposing the colon to TNBS induced marked colonic damage, but no bladder damage as defined histologically. We found that in response to acute colonic damage, bladder TEER significantly decreased after 1 day (P<0.0001) and after 3 days (P<0.0001), and bladder macromolecular permeability significantly increased after 1 day (P<0.05) and 3 days (P<0.01) when compared to saline-treated controls. In the colon from TNBS-treated rats there was a significant decrease in TEER, and a significant increase in macromolecular transport of FITC-dextrin after 1 day (P<0.005) and 3 days (P<0.0001) compared to saline-treated controls. CONCLUSIONS These data demonstrate that following acute colon damage there was a marked increase in the permeability of the bladder in the absence of any histological damage to the bladder. This new data reinforces the notion that changes in epithelial permeability may represent a novel mechanism for visceral organ crosstalk and may be important in the overlapping symptomology of PBS and IBS. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e1027-e1028 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Alexander Parker More articles by this author Ehsan Mohommadi More articles by this author Karl Tyler More articles by this author Robert E. Hurst More articles by this author Beverley Greenwood-Van Meerveld More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...