BACKGROUND:Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac desmosome disease, as more than 50% of affected patients carry pathogenic variants in desmosome protein-coding genes. In this study, we focused on the role and mechanisms of pathogenic and non-pathogenic autoantibodies against intercalated disc (ICD) proteins such as desmoglein2 (DSG2) in ACM patients, healthy relatives (HR), and murine ACM models. MATERIALS AND METHODS:IgG fractions from ACM patients, HR, healthy controls, and murine ACM models were isolated. Besides ELISA and cleavage assay, dissociation assay, immunostaining, Triton-X-100 assay, Western blots, and atomic force microscopy were performed in murine cardiac slices, HL-1 cells, or induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs). RESULTS:IgG fractions from ACM patients and HR, but not murine ACM model-derived or grouped healthy controls IgG (G-HC), revealed positive ICD staining. Three out of six ACM patients derived IgGs that reduced cardiomyocyte cohesion. Pathogenic autoantibodies, bound to DSG2 in healthy and ACM hiPSC-CMs, cleaved and reduced DSG2 interaction at the molecular level. We investigated GSK-3β contribution to the cardiomyocyte cohesion loss and observed GSK-3β reduced baseline cohesion in cultured cardiomyocytes and cardiac slices. Among five ACM-IgGs, three HR-IgGs tested, three pathogenic ACM-IgGs activated GSK-3β upstream of p38MAPK, leading to phosphorylation and junctional loss of β-catenin. GSK-3β inhibition rescued the loss of cell cohesion in ACM hiPSC-CMs. CONCLUSION:Pathogenic autoantibodies targeting DSG2 are present in ACM patients and impair cardiomyocyte cohesion in a GSK-3β-dependent manner. In contrast, autoantibodies are absent in murine ACM models and are non-pathogenic in some patients and HR.

Arrhythmogenic cardiomyopathy (ACM) is a genetically inherited desmosome heart disease leading to life-threatening arrhythmias and sudden cardiac death. Currently, ACM treatment paradigms are merely symptom targeting. Recently, apremilast was shown to stabilize keratinocyte adhesion in the desmosomal disease pemphigus vulgaris. Therefore, this study investigated whether apremilast can be a therapeutic option for ACM. Human induced pluripotent stem cells from a healthy control (hiPSC) and an ACM index patient (ACM-hiPSC) carrying a heterozygous desmoplakin (DSP) gene mutation (c.2854G > T, p.Glu952Ter), confirmed by whole exome sequencing (WES), were established. Cyclic-AMP ELISA, dissociation assay, immunostaining, and Western blotting analyses were performed in human iPSC-derived cardiomyocytes (hiPSC-CMs), murine HL-1 cardiomyocytes, and cardiac slices derived from wild-type (WT) mice, plakoglobin (PG, Jup) knockout (Jup−/−) (murine ACM model) or PG Serine 665 phosphodeficient (JUP-S665A) mice. Microelectrode array (MEA) analyses in ventricular cardiac slices and Langendorff heart perfusion were performed to analyze heart rate variability and arrhythmia. ACM-hiPSC derived cardiomyocytes (ACM-hiPSC-CMs) revealed a significant loss of cohesion, which was rescued by apremilast. Further, treatment with apremilast strengthened basal cardiomyocyte cohesion in HL-1 cells and WT murine cardiac slices, paralleled by phosphorylation of PG at Serine 665 in human and murine models. In HL-1 cells, apremilast in addition activated ERK1/2, inhibition of which abolished apremilast-enhanced cardiomyocyte cohesion. Further, dissociation assays in slice cultures from JUP-S665A and Jup−/− mice revealed that PG is crucial for apremilast-enhanced cardiomyocyte cohesion. In parallel to enhanced cell adhesion, MEA and Langendorff measurements from WT and Jup−/− mice demonstrated decreased heart rate variability and arrhythmia after apremilast treatment. Apremilast improves loss of cardiomyocyte cohesion, enhances localization of DSG2, and reduces arrhythmia in human and/or murine models of ACM ex vivo and in vitro, providing a novel treatment strategy for ACM by preserving desmosome function.

Protozoan parasites cause a wide range of devastating diseases in various kinds of organisms, including humans. It may be lethal if untreated promptly. To detect specific disease-causingorganisms parasites, a wide range of immunological and molecular technologies are now widely available. However, all of this depends on the worker's expertise and are time-consuming, error-prone, and expensive. With the development of technology, compared to traditional biological techniques, convolutional neural networks have reached excellent achievements in image classification, cutting costs while attaining an overall higher accuracy and eliminating human error. Many models include numerous convolutional layers and offer an accuracy between 90 and 95 percent. In this study, 4740 microscopic images of protozoan parasites from six classes with a balanced dataset and an 80–20% split were classified using three convolutional layers with stochastic gradient descent as an optimizer. A 5-fold cross-validation approach is used to evaluate the proposed method. We also examine and evaluate with deep learning models namely VGG16, ResNet50, and InceptionV3. The performance evaluation of the proposed model shows an accuracy of 94% with a precision range (of 0.83-0.99) and a recall range (of 0.76-1.00), respectively. The retrained model was able to recognize and classify all 6 different parasites. Except for class Leishmania, where 24% of images are incorrectly classified as Plasmodium and Trichomonas, the model demonstrates that most cases are correctly identified.

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.

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.

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.

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.

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.

Research Article 1 EGFR inhibition stabilizes cardiomyocyte cohesion in a murine arrhythmogenic 2 cardiomyopathy model 3 4 Condensed title: Positive adhesiotropy by EGFR inhibition 5 Maria Shoykhet, Orsela Dervishi, Philipp Menauer, Matthias Hiermaier, Jens Waschke 6 and Sunil Yeruva 7 Faculty of Medicine, Ludwig-Maximilian-University (LMU) Munich, Munich, Germany 8 Corresponding author: 9 *Sunil Yeruva, Anatomical Institute, Department I – Vegetative Anatomy, Ludwig10 Maximilian-University, Pettenkoferstraße 11, 80336 Munich, Germany; Phone: +49-89-218011 72703; sunil.yeruva@med.uni-muenchen.de 12 13

Pemphigus vulgaris (PV) is a life-threatening blistering skin disease caused by autoantibodies (PV-IgG) 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 e.g. in psoriasis, prevents blistering in PV. Apremilast abrogated PV-IgG-induced loss of keratinocyte cohesion in ex-vivo epidermis and in vitro. This was paralleled by inhibition of keratin retraction and desmosome splitting but affected neither desmoglein (Dsg) depletion nor Dsg3 binding properties. Apremilast induced phosphorylation of plakoglobin at serine 665 – a mechanisms which is known to stabilize cardiomyocyte cohesion. Interestingly, keratinocytes phospho-deficient at this side showed altered organization of Dsg1, Dsg3 and keratin filaments and impaired adhesion, which was not rescued by apremilast. These data identified a new mechanism of desmosome regulation and propose that apremilast is protective in pemphigus by stabilizing keratinocyte cohesion.

Cardiac autonomic nervous system (ANS) dysregulation is a hallmark of cardiovascular diseases such as heart failure, arrhythmias and myocardial infarction. To understand the role of ANS in cardiomyocyte cohesion, we have previously identified that adrenergic signaling enhances cardiomyocyte cohesion via PKA-mediated plakoglobin phosphorylation at serine 665, which we termed as positive adhesiotropy. In this study, we investigated the role of parasympathetic nervous system in cardiomyocyte cohesion, using carbachol (CCH) as a cholinergic agonist that binds to the muscarinic receptors. Dissociation assays performed in HL-1 cells, grown in norepinephrine (NE) containing medium for baseline adrenergic stimulation, and in murine cardiac slice cultures from wild type (wt) and plakoglobin (Pg) knockout (Jup ) mice revealed an impaired cardiomyocyte cohesion after CCH treatment. Electron microscopy revealed that CCH reduced intercalated disc plaque thickness in both wt and Jup mice. Immunostaining and atomic force microscopy in HL-1 cells demonstrated that CCH reduced desmoglein 2 (Dsg2) localization and binding at cell borders. Immunoprecipitation showed no alterations in the interaction of Dsg2, desmoplakin, plakophilin 2 and Pg after CCH treatment. Nevertheless, knockdown of any of the above genes abrogated the loss of cardiomyocyte cohesion in response to CCH. In HL-1 cells, CCH inhibited ERK phosphorylation but not Pg phosphorylation at serine 665 induced by forskolin/rolipram (FR) combination used for adrenergic stimulation. In addition, CCH activated the AKT/GSK-3β axis in the presence of NE. In conclusion, our results demonstrate that cholinergic signaling antagonizes the positive effect of adrenergic signaling on cardiomyocyte cohesion and thus causes negative adhesiotropy, which is independent of Pg phosphorylation.

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.

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase ubiquitously expressed in different tissues, including the heart. EGFR is dysregulated in several kinds of cancer, as well as in heart diseases. Arrhythmogenic cardiomyopathy (ACM) is a familial heart disease and one of the underlying mechanisms is impaired desmosome turnover. The intercalated disc (ICD) not only provides cellular cohesion but can also provide the structural framework of a signaling hub. Thus, stabilizing desmosome integrity, thereby enhancing cardiomyocyte stability, may provide potential new treatment options. In this study, we investigated the role of EGFR inhibition on cardiomyocyte cohesion under physiological as well as under pathophysiological conditions using the cardiomyocyte‐specific plakoglobin knockout (Jup‐/‐) ACM model in which EGFR was upregulated. Dissociation assays in HL‐1 cells and murine cardiac slice cultures showed that EGFR inhibition by erlotinib similar to SRC inhibition enhanced cardiomyocyte cohesion. Immunoprecipitation showed an interaction of EGFR, desmoglein 2 (DSG2) and desmoplakin (DP), indicating that altered EGFR signaling might affect desmosomes. Immunostainings and atomic force microscopy (AFM) revealed enhanced DSG2 localization and binding at the cell borders upon EGFR inhibition. In addition, during desmosome assembly induced by a Ca2+‐switch, DSG2 and DP were augmented at the cell borders after EGFR or SRC inhibition. Our study shows that EGFR inhibition by erlotinib leads to increased DSG2 binding and desmosome assembly, which stabilizes cardiomyocyte cohesion in the ACM mouse model. Because EGFR inhibition by erlotinib is already used in cancer patients, these data reveal a potential new therapeutic strategy in ACM.

Arrhythmogenic cardiomyopathy (AC) is a familial heart disease partly caused by impaired desmosome turnover. Thus, stabilization of desmosome integrity may provide potential 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 knockout AC model, in which EGFR was upregulated. EGFR inhibition enhanced cardiomyocyte cohesion. Immunoprecipitation showed an interaction of EGFR and desmoglein 2 (DSG2). Immunostaining and 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. Erlotinib, an EGFR inhibitor, activated ROCK. Erlotinib mediated desmosome assembly and cardiomyocyte cohesion were abolished upon ROCK inhibition. Thus, inhibiting EGFR, thereby stabilizing desmosome integrity, might provide new treatment options for AC. Summary Shoykhet et al. show that EGFR inhibition led ROCK activation enhances cardiomyocyte cohesion via enhanced desmosomal assembly which is evidenced by enhanced DP/DSG2 localization at cell borders. It is the first step towards a novel therapeutic approach for 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.

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.