Catalytic antibodies in arrhythmogenic cardiomyopathy patients cleave desmoglein 2 and N-cadherin and impair cardiomyocyte cohesion.

AIMS: Arrhythmogenic cardiomyopathy (AC) is a severe heart disease predisposing to ventricular arrhythmias and sudden cardiac death caused by mutations affecting intercalated disc (ICD) proteins and aggravated by physical exercise. Recently, autoantibodies targeting ICD proteins, including the desmosomal cadherin desmoglein 2 (DSG2), were reported in AC patients and were considered relevant for disease development and progression, particularly in patients without underlying pathogenic mutations. However, it is unclear at present whether these autoantibodies are pathogenic and by which mechanisms show specificity for DSG2 and thus can be used as a diagnostic tool. METHODS AND RESULTS: IgG fractions were purified from 15 AC patients and 4 healthy controls. Immunostainings dissociation assays, atomic force microscopy (AFM), Western blot analysis and Triton X-100 assays were performed utilizing human heart left ventricle tissue, HL-1 cells and murine cardiac slices. Immunostainings revealed that autoantibodies against ICD proteins are prevalent in AC and most autoantibody fractions have catalytic properties and cleave the ICD adhesion molecules DSG2 and N-cadherin, thereby reducing cadherin interactions as revealed by AFM. Furthermore, most of the AC-IgG fractions causing loss of cardiomyocyte cohesion activated p38MAPK, which is known to contribute to a loss of desmosomal adhesion in different cell types, including cardiomyocytes. In addition, p38MAPK inhibition rescued the loss of cardiomyocyte cohesion induced by AC-IgGs. CONCLUSION: Our study demonstrates that catalytic autoantibodies play a pathogenic role by cleaving ICD cadherins and thereby reducing cardiomyocyte cohesion by a mechanism involving p38MAPK activation. Finally, we conclude that DSG2 cleavage by autoantibodies could be used as a diagnostic tool for AC.

cAMP: A master regulator of cadherin-mediated binding in endothelium, epithelium and myocardium.

Regulation of cadherin-mediated cell adhesion is crucial not only for maintaining tissue integrity and barrier function in the endothelium and epithelium but also for electromechanical coupling within the myocardium. Therefore, loss of cadherin-mediated adhesion causes various disorders, including vascular inflammation and desmosome-related diseases such as the autoimmune blistering skin dermatosis pemphigus and arrhythmogenic cardiomyopathy. Mechanisms regulating cadherin-mediated binding contribute to the pathogenesis of diseases and may also be used as therapeutic targets. Over the last 30 years, cyclic adenosine 3',5'-monophosphate (cAMP) has emerged as one of the master regulators of cell adhesion in endothelium and, more recently, also in epithelial cells as well as in cardiomyocytes. A broad spectrum of experimental models from vascular physiology and cell biology applied by different generations of researchers provided evidence that not only cadherins of endothelial adherens junctions (AJ) but also desmosomal contacts in keratinocytes and the cardiomyocyte intercalated discs are central targets in this scenario. The molecular mechanisms involve protein kinase A- and exchange protein directly activated by cAMP-mediated regulation of Rho family GTPases and S665 phosphorylation of the AJ and desmosome adaptor protein plakoglobin. In line with this, phosphodiesterase 4 inhibitors such as apremilast have been proposed as a therapeutic strategy to stabilize cadherin-mediated adhesion in pemphigus and may also be effective to treat other disorders where cadherin-mediated binding is compromised.

Cardiomyocyte cohesion is increased after ADAM17 inhibition.

A Disintegrin And Metalloprotease (ADAM) family proteins are involved in several cardiac diseases, and some ADAMs have been associated with cardiomyopathies. ADAM17 is known to cleave desmoglein 2 (DSG2), one of the proteins involved in the pathogenesis of arrhythmogenic cardiomyopathy (AC). Desmosomal stability is impaired in AC, an inheritable genetic disease, the underlying causes of which can be mutations in genes coding for proteins of the desmosome, such as DSG2, desmoplakin (DP), plakoglobin (PG), plakophilin 2 or desmocollin 2. Stabilizing desmosomal contacts can therefore be a treatment option. In the heart of the murine Jup -/- AC model, (Jup being the gene coding for PG) mice, elevated levels of p38MAPK, an activator of ADAM17, were found. However, ADAM17 levels were unaltered in Jup -/- mice hearts. Nonetheless, inhibition of ADAM17 led to enhanced cardiomyocyte cohesion in both Jup +/+ and Jup -/- mice, and in HL-1 cardiomyocytes. Further, enhanced cohesion in HL-1 cardiomyocytes after acute inhibition of ADAM17 was paralleled by enhanced localization of DSG2 and DP at the membrane, whereas no changes in desmosomal assembly or the desmosomal complex were observed. In conclusion, acute inhibition of ADAM17 might lead to reduced cleavage of DSG2, thereby stabilizing the desmosomal adhesion, evidenced by increased DSG2 and DP localization at cell borders and eventually cardiomyocyte cohesion. We believe that similar mechanisms exist in AC.

EGFR inhibition leads to enhanced desmosome assembly and cardiomyocyte cohesion via ROCK activation.

Arrhythmogenic cardiomyopathy (AC) is a familial heart disease partly caused by impaired desmosome turnover. Thus, stabilization of desmosome integrity may provide new treatment options. Desmosomes, apart from cellular cohesion, provide the structural framework of a signaling hub. Here, we investigated the role of the epidermal growth factor receptor (EGFR) in cardiomyocyte cohesion. We inhibited EGFR under physiological and pathophysiological conditions using the murine plakoglobin-KO AC model, in which EGFR was upregulated. EGFR inhibition enhanced cardiomyocyte cohesion. Immunoprecipitation showed an interaction of EGFR and desmoglein 2 (DSG2). Immunostaining and atomic force microscopy (AFM) revealed enhanced DSG2 localization and binding at cell borders upon EGFR inhibition. Enhanced area composita length and desmosome assembly were observed upon EGFR inhibition, confirmed by enhanced DSG2 and desmoplakin (DP) recruitment to cell borders. PamGene Kinase assay performed in HL-1 cardiomyocytes treated with erlotinib, an EGFR inhibitor, revealed upregulation of Rho-associated protein kinase (ROCK). Erlotinib-mediated desmosome assembly and cardiomyocyte cohesion were abolished upon ROCK inhibition. Thus, inhibiting EGFR and, thereby, stabilizing desmosome integrity via ROCK might provide treatment options for AC.

Apremilast prevents blistering in human epidermis and stabilizes keratinocyte adhesion in pemphigus.

Pemphigus vulgaris is a life-threatening blistering skin disease caused by autoantibodies destabilizing desmosomal adhesion. Current therapies focus on suppression of autoantibody formation and thus treatments directly stabilizing keratinocyte adhesion would fulfill an unmet medical need. We here demonstrate that apremilast, a phosphodiesterase 4 inhibitor used in psoriasis, prevents skin blistering in pemphigus vulgaris. Apremilast abrogates pemphigus autoantibody-induced loss of keratinocyte cohesion in ex-vivo human epidermis, cultured keratinocytes in vitro and in vivo in mice. In parallel, apremilast inhibits keratin retraction as well as desmosome splitting, induces phosphorylation of plakoglobin at serine 665 and desmoplakin assembly into desmosomal plaques. We established a plakoglobin phospho-deficient mouse model that reveals fragile epidermis with altered organization of keratin filaments and desmosomal cadherins. In keratinocytes derived from these mice, intercellular adhesion is impaired and not rescued by apremilast. These data identify an unreported mechanism of desmosome regulation and propose that apremilast stabilizes keratinocyte adhesion and is protective in pemphigus.

Structure and regulation of desmosomes in intercalated discs: Lessons from epithelia.

For electromechanical coupling of cardiomyocytes, intercalated discs (ICDs) are pivotal as highly specialized intercellular contact areas. ICD consists of adhesive contacts, such as desmosomes and adherens junctions (AJs) that are partially intermingled and thereby form an area composita to provide mechanical strength, as well as gap junctions (GJ) and sodium channels for excitation propagation. In contrast, in epithelia, mixed junctions with features of desmosomes and AJs are regarded as transitory primarily during the formation of desmosomes. The anatomy of desmosomes is defined by a typical ultrastructure with dense intracellular plaques anchoring the cadherin-type adhesion molecules to the intermediate filament cytoskeleton. Desmosomal diseases characterized by impaired adhesive and signalling functions of desmosomal contacts lead to arrhythmogenic cardiomyopathy when affecting cardiomyocytes and cause pemphigus when manifesting in keratinocytes or present as cardiocutaneous syndromes when both cell types are targeted by the disease, which underscores the high biomedical relevance of these cell contacts. Therefore, comparative analyses regarding the structure and regulation of desmosomal contacts in cardiomyocytes and epithelial cells are helpful to better understand disease pathogenesis. In this brief review, we describe the structural properties of ICD compared to epithelial desmosomes and suggest that mechanisms regulating adhesion may at least in part be comparable. Also, we discuss whether phenomena such as hyperadhesion or the bidirectional regulation of desmosomes to serve as signalling hubs in epithelial cells may also be relevant for ICD.

Cholinergic signaling impairs cardiomyocyte cohesion.

AIM: Cardiac autonomic nervous system (ANS) dysregulation is a hallmark of several cardiovascular diseases. Adrenergic signaling enhanced cardiomyocyte cohesion via PKA-mediated plakoglobin phosphorylation at serine 665, referred to as positive adhesiotropy. This study investigated cholinergic regulation of cardiomyocyte cohesion using muscarinic receptor agonist carbachol (CCH). METHODS: Dissociation assays, Western blot analysis, immunostaining, atomic force microscopy (AFM), immunoprecipitation, transmission electron microscopy (TEM), triton assays, and siRNA knockdown of genes were performed in either HL-1 cells or plakoglobin (PG) wild type (Jup+/+ ) and knockout (Jup-/- ) mice, which served as a model for arrhythmogenic cardiomyopathy. RESULTS: In HL-1 cells grown in norepinephrine (NE)-containing medium for baseline adrenergic stimulation, and murine cardiac slice cultures from Jup+/+ and Jup-/- mice CCH treatment impaired cardiomyocyte cohesion. Immunostainings and AFM experiments revealed that CCH reduced desmoglein 2 (DSG2) localization and binding at cell borders. Furthermore, CCH reduced intercalated disc plaque thickness in both Jup+/+ and Jup-/- mice, evidenced by TEM analysis. Immunoprecipitation experiments in HL-1 cells revealed no changes in DSG2 interaction with desmoplakin (DP), plakophilin 2 (PKP2), PG, and desmin (DES) after CCH treatment. However, knockdown of any of the above proteins abolished CCH-mediated loss of cardiomyocyte cohesion. Furthermore, in HL-1 cells, CCH inhibited adrenergic-stimulated ERK phosphorylation but not PG phosphorylation at serine 665. In addition, CCH activated the AKT/GSK-3ß axis in the presence of NE. CONCLUSION: Our results demonstrate that cholinergic signaling antagonizes the positive effect of adrenergic signaling on cardiomyocyte cohesion and thus causes negative adhesiotropy independent of PG phosphorylation.

Cardiomyocyte adhesion and hyperadhesion differentially require ERK1/2 and plakoglobin.

Arrhythmogenic cardiomyopathy (AC) is a heart disease often caused by mutations in genes coding for desmosomal proteins, including desmoglein-2 (DSG2), plakoglobin (PG), and desmoplakin (DP). Therapy is based on symptoms and limiting arrhythmia, because the mechanisms by which desmosomal components control cardiomyocyte function are largely unknown. A new paradigm could be to stabilize desmosomal cardiomyocyte adhesion and hyperadhesion, which renders desmosomal adhesion independent from Ca2+. Here, we further characterized the mechanisms behind enhanced cardiomyocyte adhesion and hyperadhesion. Dissociation assays performed in HL-1 cells and murine ventricular cardiac slice cultures allowed us to define a set of signaling pathways regulating cardiomyocyte adhesion under basal and hyperadhesive conditions. Adrenergic signaling, activation of PKC, and inhibition of p38MAPK enhanced cardiomyocyte adhesion, referred to as positive adhesiotropy, and induced hyperadhesion. Activation of ERK1/2 paralleled positive adhesiotropy, whereas adrenergic signaling induced PG phosphorylation at S665 under both basal and hyperadhesive conditions. Adrenergic signaling and p38MAPK inhibition recruited DSG2 to cell junctions. In PG-deficient mice with an AC phenotype, only PKC activation and p38MAPK inhibition enhanced cardiomyocyte adhesion. Our results demonstrate that cardiomyocyte adhesion can be stabilized by different signaling mechanisms, which are in part offset in PG-deficient AC.

Adrenergic Signaling-Induced Ultrastructural Strengthening of Intercalated Discs via Plakoglobin Is Crucial for Positive Adhesiotropy in Murine Cardiomyocytes.

Intercalated discs (ICDs), which connect adjacent cardiomyocytes, are composed of desmosomes, adherens junctions (AJs) and gap junctions (GJs). Previous data demonstrated that adrenergic signaling enhances cardiac myocyte cohesion, referred to as positive adhesiotropy, via PKA-mediated phosphorylation of plakoglobin (PG). However, it was unclear whether positive adhesiotropy caused ultrastructural modifications of ICDs. Therefore, we further investigated the role of PG in adrenergic signaling-mediated ultrastructural changes in the ICD of cardiomyocytes. Quantitative transmission electron microscopy (TEM) analysis of ICD demonstrated that cAMP elevation caused significant elongation of area composita and thickening of the ICD plaque, paralleled by enhanced cardiomyocyte cohesion, in WT but not PG-deficient cardiomyocytes. STED microscopy analysis supported that cAMP elevation ex vivo enhanced overlap of desmoglein-2 (Dsg2) and N-cadherin (N-cad) staining in ICDs of WT but not PG-deficient cardiomyocytes. For dynamic analyses, we utilized HL-1 cardiomyocytes, in which cAMP elevation induced translocation of Dsg2 and PG but not of N-cad to cell junctions. Nevertheless, depletion of N-cad but not of Dsg2 resulted in a decrease in basal cell cohesion whereas positive adhesiotropy was abrogated in monolayers depleted for either Dsg2 or N-cad. In the WT mice, ultrastrutural changes observed after cAMP elevation were paralleled by phosphorylation of PG at serine 665. Our data demonstrate that in murine hearts adrenergic signaling enhanced N-cad and Dsg2 in the ICD paralleled by ultrastrutural strengthening of ICDs and that effects induced by positive adhesiotropy were strictly dependent on Pg.

The inotropic agent digitoxin strengthens desmosomal adhesion in cardiac myocytes in an ERK1/2-dependent manner.

Desmosomal proteins are components of the intercalated disc and mediate cardiac myocyte adhesion. Enhancement of cardiac myocyte cohesion, referred to as "positive adhesiotropy", was demonstrated to be a function of sympathetic signaling and to be relevant for a sufficient inotropic response. We used the inotropic agent digitoxin to investigate the link between inotropy and adhesiotropy. In contrast to wild-type hearts, digitoxin failed to enhance pulse pressure in perfused mice hearts lacking the desmosomal protein plakoglobin which was paralleled with abrogation of plaque thickening indicating that positive inotropic response requires intact desmosomal adhesion. Atomic force microscopy revealed that digitoxin increased the binding force of the adhesion molecule desmoglein-2 at cell-cell contact areas. This was paralleled by enhanced cardiac myocyte cohesion in both HL-1 cardiac myocytes and murine cardiac slices as determined by dissociation assays as well as by accumulation of desmosomal proteins at cell-cell contact areas. However, total protein levels or cytoskeletal anchorage were not affected. siRNA-mediated depletion of desmosomal proteins abrogated increase of cell cohesion demonstrating that intact desmosomal adhesion is required for positive adhesiotropy. Mechanistically, digitoxin caused activation of ERK1/2. In line with this, inhibition of ERK1/2 signaling abrogated the effects of digitoxin on cell-cell adhesion and desmosomal reorganization. These results show that the positive inotropic agent digitoxin enhances cardiac myocyte cohesion with reorganization of desmosomal proteins in an ERK1/2-dependent manner. Desmosomal adhesion seems to be important for a sufficient positive inotropic response of digitoxin treatment, which can be of medical relevance for the treatment of heart failure.

Stabilization of desmoglein-2 binding rescues arrhythmia in arrhythmogenic cardiomyopathy.

Arrhythmogenic cardiomyopathy (AC) is a genetic disease causing arrhythmia and sudden cardiac death with only symptomatic therapy available at present. Mutations of desmosomal proteins, including desmoglein-2 (Dsg2) and plakoglobin (Pg), are the major cause of AC and have been shown to lead to impaired gap junction function. Recent data indicated the involvement of anti-Dsg2 autoantibodies in AC pathogenesis. We applied a peptide to stabilize Dsg2 binding similar to a translational approach to pemphigus, which is caused by anti-desmoglein autoantibodies. We provide evidence that stabilization of Dsg2 binding by a linking peptide (Dsg2-LP) is efficient to rescue arrhythmia in an AC mouse model immediately upon perfusion. Dsg2-LP, designed to cross-link Dsg2 molecules in proximity to the known binding pocket, stabilized Dsg2-mediated interactions on the surface of living cardiomyocytes as revealed by atomic force microscopy and induced Dsg2 oligomerization. Moreover, Dsg2-LP rescued disrupted cohesion induced by siRNA-mediated Pg or Dsg2 depletion or l-tryptophan, which was applied to impair overall cadherin binding. Dsg2-LP rescued connexin-43 mislocalization and conduction irregularities in response to impaired cardiomyocyte cohesion. These results demonstrate that stabilization of Dsg2 binding by Dsg2-LP can serve as a novel approach to treat arrhythmia in patients with AC.

Calcium-sensing receptor regulates intestinal dipeptide absorption via Ca2+ signaling and IKCa activation.

Although absorption of di- and tripeptides into intestinal epithelial cells occurs via the peptide transporter 1 (PEPT1, also called solute carrier family 15 member 1 (SLC15A1)), the detailed regulatory mechanisms are not fully understood. We examined: (a) whether dipeptide absorption in villous enterocytes is associated with a rise in cytosolic Ca2+ ([Ca2+ ]cyt ), (b) whether the calcium sensing receptor (CaSR) is involved in dipeptide-elicited [Ca2+ ]cyt signaling, and (c) what potential consequences of [Ca2+ ]cyt signaling may enhance enterocyte dipeptide absorption. Dipeptide Gly-Sar and CaSR agonist spermine markedly raised [Ca2+ ]cyt in villous enterocytes, which was abolished by NPS-2143, a selective CaSR antagonist and U73122, an phospholipase C (PLC) inhibitor. Apical application of Gly-Sar induced a jejunal short-circuit current (Isc), which was reduced by NPS-2143. CaSR expression was identified in the lamina propria and on the basal enterocyte membrane of mouse jejunal mucosa in both WT and Slc15a1-/- animals, but Gly-Sar-induced [Ca2+ ]cyt signaling was significantly decreased in Slc15a1-/- villi. Clotrimazole and TRM-34, two selective blockers of the intermediate conductance Ca2+ -activated K+ channel (IKCa ), but not iberiotoxin, a selective blocker of the large-conductance K+ channel (BKCa ) and apamin, a selective blocker of the small-conductance K+ channel (SKCa ), significantly inhibited Gly-Sar-induced Isc in native tissues. We reveal a novel CaSR-PLC-Ca2+ -IKCa pathway in the regulation of small intestinal dipeptide absorption, which may be exploited as a target for future drug development in human nutritional disorders.

Differential regulation of claudin-2 and claudin-15 expression in children and adults with malabsorptive disease.

Intestinal Na+-nutrient cotransport depends on claudin-2 and claudin-15 mediated Na+ recycling. Expression of these proteins is coordinately regulated during postnatal development. While expression of claudin-2 and claudin-15 has been studied in inflammatory bowel disease (IBD) and celiac disease (CD), it has not been assessed in other malabsorptive diseases, and no reports have compared expression in children and adults. We used quantitative immunofluorescence microscopy to assess claudin-2 and claudin-15 expression in duodenal biopsies from children and adults with malabsorptive disease and healthy controls. Consistent with previous work in rodents, claudin-2 expression in healthy children was markedly greater, and claudin-15 expression was less, than that in adults. Claudin-2 expression was increased in adults with CD and downregulated in children with graft-versus-host disease (GVHD). In contrast, claudin-15 expression was reduced in adults with GVHD and common variable immunodeficiency (CVID). These data show that one of the two Na+/water pore-forming claudins is upregulated in CD and downregulated in GVHD and CVID. The specific claudin whose expression changes, however, reflects the age of the patient (child or adult). We conclude that contributions of claudin-2 and claudin-15 to pathophysiology of and responses to diarrhea in children and adults with GVHD and CVID differ from those in CD and IBD.

Expression, Localization and Functional Activity of the Major Na⁺/H⁺ Exchange Isoforms Expressed in the Intestinal Cell Line Caco-2BBe.

BACKGROUND/AIMS: Enterocytes express a number of NHE isoforms with presumed localization in the apical (NHE2, 3 and 8) or basolateral (NHE1) membrane. Functional activity and localization of enterocyte NHE isoforms were assessed using fully differentiated Caco-2BBe cells, whose genetic expression profile closely resembles mature enterocytes. METHODS: The activity of the different NHEs was analyzed by fluorometric pHi-metry in a perfusion chamber with separate apical and basolateral perfusion, using specific inhibitors and shRNA knockdown of NHE2. The expression of the NHEs and of other relevant acid extrusion transporters was quantified by qPCR. RESULTS: Quantitative comparison of the mRNA expression levels of the different NHE isoforms in 14 day-differentiated Caco-2BBe cells showed the following order: NHE2>NHE8>NHE3>NHE1. Acid-activated NHE exchange rates in the basolateral membrane were >6-fold higher than in the apical membrane. 79 ± 3 % of the acid-activated basolateral Na⁺/H⁺ exchange rate displayed a NHE1-typical inhibitor profile, and no NHE2/3/8 typical activity could be observed. Analysis of the apical Na⁺/H⁺ exchange rates revealed that approximately 51 ± 3 % of the total apical activity displayed a NHE2/8-typical inhibitor profile and 31 ± 6 % a NHE3-typical inhibitor profile. Because no selective NHE2 inhibitor is available, a stable NHE2 knockdown cell line (C2NHE2KD) was generated. C2NHE2KD displayed a reduced NHE2-typical apical Na⁺/H⁺ exchange rate and maintained a lower steady-state pHi, despite high expression levels of other acid extruders, in particular NBCn1 (Slc4a7). CONCLUSION: Differentiated Caco-2BBe cells display particularly high mRNA expression levels of NHE2, which can be functionally identified in the apical membrane. Although at low intracellular pH, NHE2 transport rate was far lower than that of NHE1. NHE2 activity was nevertheless essential for the maintenance of the steady-state pHi of these cells.

Regulation of cardiac myocyte cohesion and gap junctions via desmosomal adhesion.

AIMS: Mutations in desmosomal proteins can induce arrhythmogenic cardiomyopathy with life-threatening arrhythmia. Previous data demonstrated adrenergic signalling to be important to regulate desmosomal cohesion in cardiac myocytes. Here, we investigated how signalling pathways including adrenergic signalling, PKC and SERCA regulate desmosomal adhesion and how this controls gap junctions (GJs) in cardiac myocytes. METHODS: Immunostaining, Western blot, dissociation assay and multi-electrode array were applied in HL-1 cardiac myocytes to evaluate localization, expression and function of desmosomal and GJ components. cAMP levels were determined by ELISA. RESULTS: Activation of PKC by PMA or adrenergic signalling increased cell cohesion and desmoglein-2 and desmoplakin localization at cell-cell junctions, whereas tryptophan (Trp) treatment to inhibit cadherin binding or inhibition of SERCA by thapsigargin reduced cell cohesion, while cAMP elevation rescued this effect. Despite no changes in protein expression, accumulation of GJ protein connexin-43 was detectable at cell-cell contacts in parallel to increased cohesion. Disruption of cell cohesion by Trp, PMA or thapsigargin impaired conduction of excitation comparable to GJ inhibition. cAMP elevation was effective to improve arrhythmia after Trp treatment. Weakened cell cohesion by Trp or depletion of desmoglein-2 or plakoglobin blocked signalling via the ß1-adrenergic receptor. Moreover, silencing of desmosomal proteins increased arrhythmia and reduced conduction velocity, which were rescued by cAMP elevation. CONCLUSION: These data demonstrate the interplay of GJs, desmosomes and the ß1-adrenergic receptor with regulation of their function by cell cohesion, adrenergic and PKC signalling or SERCA inhibition. These results support the identification of new targets to treat arrhythmogenic cardiomyopathy.

Environmental Enteropathy in Undernourished Pakistani Children: Clinical and Histomorphometric Analyses.

Despite nutrition interventions, stunting thought to be secondary to underlying environmental enteropathy (EE) remains pervasive among infants residing in resource-poor countries and remains poorly characterized. From a birth cohort of 380 children, 65 malnourished infants received 12 weeks of nutritional supplementation with ready-to-use therapeutic food (RUTF). Eleven children with insufficient response to RUTF underwent upper endoscopy with duodenal biopsies, which were compared with U.S., age-matched specimens for healthy, celiac disease, non-celiac villous atrophy, non-celiac intraepithelial lymphocytosis, and graft-versus-host disease patients. Of the 11 children biopsied, EE was found in 10 (91%) with one subject with celiac disease. Morphometry demonstrated decreased villus-to-crypt (V:C) ratios in EE relative to healthy and non-celiac lymphocytosis patients. Environmental enteropathy villus volumes were significantly decreased relative to healthy controls. In EE, average CD3+ cells per 100 epithelial cells and per 1,000 µm2 of lamina propria and the number of lamina propria CD20+ B-cell aggregates were increased relative to all other groups. Our results indicate that V:C ratios are reduced in EE but are less severe than in celiac disease. Environmental enteropathy intraepithelial and lamina propria T lymphocytosis is of greater magnitude than that in celiac disease. The increases in lamina propria B and T lymphocytes suggest that non-cytolytic lymphocytic activation may be a more prominent feature of EE relative to celiac disease. These results provide new insights into shared yet distinct histological and immunological features of EE and celiac disease in children.

Epithelial Organization: The Gut and Beyond.

Epithelial cells are essential to the survival and homeostasis of complex organisms. These cells cover the surfaces of all mucosae, the skin, and other compartmentalized structures essential to physiological function. In addition to maintenance of barriers that separate internal and external compartments, epithelia display a variety of organ-specific differentiated functions. Function is reflected in overall epithelial structure and organization, shape of individual cells, and proteins expressed by these cells. More than one epithelial cell type is often present within a single organ and, in many cases, individual cells differentiate to change their functional behaviors as part of normal development or in response to extracellular stimuli. This article discusses the diversity of epithelial structure and function in general terms and explores representative tissues in greater depth to highlight organ specific functions and their contributions to physiology and disease. © 2017 American Physiological Society. Compr Physiol 7:1497-1518, 2017.

Impaired Barrier Function and Autoantibody Generation in Malnutrition Enteropathy in Zambia.

Intestinal damage in malnutrition constitutes a threat to the survival of many thousands of children globally. We studied children in Lusaka, Zambia, with severe acute malnutrition (SAM) and persistent diarrhea using endoscopy, biopsy and analysis of markers and protective proteins in blood and intestinal secretions. We carried out parallel investigations in apparently healthy adults, and analyzed biomarkers only in apparently healthy children. Villus height and crypt depth did not differ in children with SAM and adult controls, but epithelial surface was reduced in children with SAM (median 445, interquartile range (IQR) 388, 562µm per 100µm muscularis mucosae) compared to adults (578, IQR 465,709; P=0.004). Histological lesions and disruptions of claudin-4 and E-cadherin were most pronounced in children with SAM. Circulating lipopolysaccharide, a marker of bacterial translocation, was higher in malnourished children (251, IQR 110,460EU/ml) than in healthy children (51, IQR 0,111; P=0.0001). Other translocation markers showed similar patterns. Anti-Deamidated Gliadin Peptide IgG concentrations, although within the normal range, were higher in children with SAM (median 2.7U/ml, IQR 1.5-8.6) than in adults (1.6, 1.4-2.1; P=0.005), and were inversely correlated with villus height (ρ=-0.79, n=13, P=0.001). Malnutrition enteropathy is associated with intestinal barrier failure and immune dysregulation.