Barrier Defects Research Articles

Genomic, Epigenomic, Transcriptomic, Proteomic and Metabolomic Approaches in Atopic Dermatitis.

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a high prevalence in the developed countries. It is associated with atopic and non-atopic diseases, and its close correlation with atopic comorbidities has been genetically demonstrated. One of the main roles of genetic studies is to comprehend the defects of the cutaneous barrier due to filaggrin deficit and epidermal spongiosis. Recently, epigenetic studies started to analyze the influence of the environmental factors on gene expression. The epigenome is considered to be a superior second code that controls the genome, which includes alterations of the chromatin. The epigenetic changes do not alter the genetic code, however, changes in the chromatin structure could activate or inhibit the transcription process of certain genes and consequently, the translation process of the new mRNA into a polypeptide chain. In-depth analysis of the transcriptomic, metabolomic and proteomic studies allow to unravel detailed mechanisms that cause AD. The extracellular space and lipid metabolism are associated with AD that is independent of the filaggrin expression. On the other hand, around 45 proteins are considered as the principal components in the atopic skin. Moreover, genetic studies based on the disrupted cutaneous barrier can lead to the development of new treatments targeting the cutaneous barrier or cutaneous inflammation. Unfortunately, at present, there are no target therapies that focus on the epigenetic process of AD. However, in the future, miR-143 could be an important objective for new therapies, as it targets the miR-335:SOX axis, thereby restoring the miR-335 expression, and repairing the cutaneous barrier defects.

Loricrin and Cytokeratin Disorganisation in Severe Forms of Periodontitis

ObjectiveThe aim of this research was to investigate the role of the cornified epithelium, the outermost layer of the oral mucosa, engineered to prevent water loss and microorganism invasion, in severe forms of periodontitis (stage III or IV, grade C). MethodsPorphyromonas gingivalis, a major periodontal disease pathogen, can affect cornified epithelial protein expression through chronic activation of signal transducer and activator of transcription 6 (Stat6). We used a mouse model, Stat6VT, that mimics this to determine the effects of barrier defect on P gingivalis–induced inflammation, bone loss, and cornified epithelial protein expression, and compared histologic and immunohistologic findings with tissues obtained from human controls and patients with stage III and IV, grade C disease. Alveolar bone loss in mice was assessed using micro-computerised tomography, and soft tissue morphology was qualitatively and semi-quantitatively assessed by histologic examination for several proteins, including loricrin, filaggrin, cytokeratin 1, cytokeratin 14, a proliferation marker, a pan-leukocyte marker, as well as morphologic signs of inflammation. Relative cytokine levels were measured in mouse plasma by cytokine array. ResultsIn the tissues from patients with periodontal disease, there were greater signs of inflammation (rete pegs, clear cells, inflammatory infiltrates) and a decrease and broadening of expression of loricrin and cytokeratin 1. Cytokeratin 14 expression was also broader and decreased in stage IV. P gingivalis–infected Stat6VT mice showed greater alveolar bone loss in 9 out of 16 examined sites, and similar patterns of disruption to human patients in expression of loricrin and cytokeratins 1 and 14. There were also increased numbers of leukocytes, decreased proliferation, and greater signs of inflammation compared with P gingivalis–infected control mice. ConclusionsOur study provides evidence that changes in epithelial organisation can exacerbate the effects of P gingivalis infection, with similarities to the most severe forms of human periodontitis.

Ex Vivo Infection of Human Skin Models with Herpes Simplex Virus 1: Accessibility of the Receptor Nectin-1 during Formation or Impairment of Epidermal Barriers Is Restricted by Tight Junctions.

Herpes simplex virus 1 (HSV-1) must overcome epidermal barriers to reach its receptors on keratinocytes and initiate infection in human skin. The cell-adhesion molecule nectin-1, which is expressed in human epidermis, acts as an efficient receptor for HSV-1 but is not within reach of the virus upon exposure of human skin under nonpathological conditions. Atopic dermatitis skin, however, can provide an entry portal for HSV-1 emphasizing the role of impaired barrier functions. Here, we explored how epidermal barriers impact HSV-1 invasion in human epidermis and influence the accessibility of nectin-1 for the virus. Using human epidermal equivalents, we observed a correlation of the number of infected cells with tight-junction formation, suggesting that mature tight junctions prior to formation of the stratum corneum prevent viral access to nectin-1. Consequently, impaired epidermal barriers driven by Th2-inflammatory cytokines interleukin 4 (IL-4) and IL-13 as well as the genetic predisposition of nonlesional atopic dermatitis keratinocytes correlated with enhanced infection supporting the impact of functional tight junctions for preventing infection in human epidermis. Comparable to E-cadherin, nectin-1 was distributed throughout the epidermal layers and localized just underneath the tight-junctions. While nectin-1 was evenly distributed on primary human keratinocytes in culture, the receptor was enriched at lateral surfaces of basal and suprabasal cells during differentiation. Nectin-1 showed no major redistribution in the thickened atopic dermatitis and IL-4/IL-13-treated human epidermis in which HSV-1 can invade. However, nectin-1 localization toward tight junction components changed, suggesting that defective tight-junction barriers make nectin-1 accessible for HSV-1 which enables facilitated viral penetration. IMPORTANCE Herpes simplex virus 1 (HSV-1) is a widely distributed human pathogen which productively infects epithelia. The open question is which barriers of the highly protected epithelia must the virus overcome to reach its receptor nectin-1. Here, we used human epidermal equivalents to understand how physical barrier formation and nectin-1 distribution contribute to successful viral invasion. Inflammation-induced barrier defects led to facilitated viral penetration strengthening the role of functional tight-junctions in hindering viral access to nectin-1 that is localized just underneath tight junctions and distributed throughout all layers. We also found nectin-1 ubiquitously localized in the epidermis of atopic dermatitis and IL-4/IL-13-treated human skin implying that impaired tight-junctions in combination with a defective cornified layer allow the accessibility of nectin-1 to HSV-1. Our results support that successful invasion of HSV-1 in human skin relies on defective epidermal barriers, which not only include a dysfunctional cornified layer but also depend on impaired tight junctions.

Hyperglycemia-activated 11β-hydroxysteroid dehydrogenase type 1 increases endoplasmic reticulum stress and skin barrier dysfunction

The diabetes mellitus (DM) skin shows skin barrier dysfunction and skin lipid abnormality, similar to conditions induced by systemic or local glucocorticoid excess and aged skin. Inactive glucocorticoid (GC) is converted into active glucocorticoid by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Hyperglycemia in DM and excessive GC are known to increase endoplasmic reticulum (ER) stress. We hypothesized that hyperglycemia affects systemic GC homeostasis and that the action of skin 11β-HSD1 and GC contributes to increased ER stress and barrier defects in DM. We compared 11β-HSD1, active GC, and ER stress between hyperglycemic and normoglycemic conditions in normal human keratinocytes and db/db mice. 11β-HSD1 and cortisol increased with time in keratinocyte culture under hyperglycemic conditions. 11β-HSD1 siRNA-transfected cells did not induce cortisol elevation in hyperglycemic condition. The production of 11β-HSD1 and cortisol was suppressed in cell culture treated with an ER stress-inhibitor. The 14-week-old db/db mice showed higher stratum corneum (SC) corticosterone, and skin 11β-HSD1 levels than 8-week-old db/db mice. Topical 11β-HSD1 inhibitor application in db/db mice decreased SC corticosterone levels and improved skin barrier function. Hyperglycemia in DM may affect systemic GC homeostasis, activate skin 11β-HSD1, and induce local GC excess, which increases ER stress and adversely affects skin barrier function.

Spermidine protects intestinal mucosal barrier function in mice colitis via the AhR/Nrf2 and AhR/STAT3 signaling pathways

Aryl hydrocarbon receptor (AhR) activation promotes intestinal barrier repair and enhances the gut mucosal barrier function in inflammatory bowel diseases (IBD). Spermidine is beneficial in several murine models of IBD and may affect AhR activity. However, the precise effects of spermidine on the intestinal barrier and AhR remain unclear. This study was designed to investigate whether spermidine affects AhR and gut barrier function in IBD models as well as, its underlying mechanism. We used dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mice, as well as, Caco2 cells incubated with TNF-α and IFN-γ to establish multiple IBD models, followed by spermidine intervention. Alcian blue/Periodic acid-Schiff (AB/PAS) staining, Fluorescein isothiocyanate (FITC)-dextran permeability assay, transepithelial electrical resistance (TER), tight junction protein (TJs) expression, and 16S rRNA scope in situ hybridization were performed to assess intestinal barrier function. AhR expression and the associated pathways were measured. AhR-targeted adeno-associated virus (AAV) and siRNA were used to explore the related molecular mechanisms. Spermidine significantly attenuated the increased intestinal permeability, decreased TER, abnormal distribution of TJs in colitis, and bacterial translocation from the gut tract. Additionally, it significantly increased AhR and Nrf2 expression and inhibited STAT3 phosphorylation. However, the protective effects of spermidine and the related alterations in pathway proteins were largely abolished by the specific inhibition of AhR. Our study demonstrated that spermidine rescues intestinal barrier defects in mice with colitis via the AhR-Nrf2 and AhR-STAT3 pathways, providing a potential therapeutic agent for IBD and other conditions associated with dysregulated gut barrier function.

Enteric glia at center stage of inflammatory bowel disease

Although our understanding of the pathophysiology of inflammatory bowel disease (IBD) is increasing, the expanding body of knowledge does not simplify the equation but rather reveals diverse, interconnected, and complex mechanisms in IBD. In addition to immune overactivation, defects in intestinal epithelial barrier (IEB) functioning, dysbiosis, and structural and functional abnormalities of the enteric nervous system are emerging as new elements contributing to the development of IBD. In addition to molecular changes in IBD, enteric glia from patients with Crohn’s disease (CD) exhibits the inability to strengthen the IEB; these defects are not observed in patients with ulcerative colitis. In addition, there is a growing body of work describing that enteric glia interacts with not only enterocytes and enteric neurons but also other local cellular neighbours. Thus, because of their functions as connectors and regulators of immune cells, IEB, and microbiota, enteric glia could be the keystone of digestive homeostasis that is lacking in patients with CD.

The chicken or the egg of lymphopenia in atopic eczema.

Lymphopenia has been documented in atopic eczema (AE) patients mostly in the setting of an active infection.1, 2 However, the question is whether lymphopenia is a primary problem in AE leading to infection or it is a secondary problem due to infection. In the study by Hollestein et al.,3 the authors conducted a retrospective review of a large electronic database (UK primary care electronic health record from CPRD GOLD). They included 71,731 adults with AE and 126,349 adults without AE. Using the definition of lymphopenia as having two lymphocyte counts of <1 × 109/L in 3 months, they showed that 4.1% (n = 2909) of AE patients had lymphopenia as compared to 3.7% (n = 4700) of controls without AE. The adjusted OR for lymphopenia in AE patients as compared to those without AE was 1.16 and this increased to 1.89 in patients with severe AE. Their data were appropriately adjusted for age, sex, ethnicity, smoking, co-morbidities and immunosuppressive drug use. In their secondary analysis, they confirmed an increased risk of skin and systemic infections including cellulitis, varicella zoster, gastroenteritis and urinary tract infection in AE patients as compared to controls. The authors also replicated their findings of lymphopenia in AE patients based in a US database, NHANES. Their data support the hypothesis that lymphopenia may predispose to increased infections in AE patients. A possible mechanism of lymphopenia in AE patients is due to the homing of systemic lymphocytes to inflamed skin. Their finding of a higher risk of lymphopenia in more severe AE is also consistent with this mechanism. While Hollestein et al. have provided a robust and well-controlled study that lymphopenia may be a primary problem in AE patients, the findings can only be inferred as an association, rather than cause-and-effect, due to the retrospective nature of the study. In a real-life clinical situation, complete blood cell (CBC) profile is normally sent when a patient is symptomatic, that is, during an illness or an infection. Acute lymphopenia is common with viral respiratory infections.4 In AE patients, CBC may also be sent together with viral or bacterial identification testing during a skin infection, which may be associated with lymphopenia.1, 2 AE patients are not known to have a primary immunodeficiency that predisposes them to have increased infection. However, skin and soft tissue infections are more common in AE patients due skin barrier defects and suppression of cutaneous innate immunity by type 2 cytokines.5 The results of Hollestein et al. are nevertheless interesting, and will need to be confirmed with prospective studies. None to declare. P. Ong reports no conflict of interest relevant to this article. Data sharing not applicable.

Direct and indirect effects of alcohol and its toxic metabolite acetaldehyde on human esophageal myofibroblasts and epithelial cells.

Mechanisms by which alcohol increases the risk of esophageal squamous cell carcinoma remain undefined. Human esophageal myofibroblasts (HEMFs) subjacent to the squamous epithelium are exposed directly to these agents via epithelial barrier defects and indirectly via factors derived from the exposed epithelium. Our aim was to investigate the cellular biology of HEMFs and HEMF-esophageal epithelial cell interactions in response to alcohol and its toxic metabolite acetaldehyde. An immortalized HEMF and a human esophageal epithelial cell line (Epi) were treated with alcohol (0 to 200 mM) or acetaldehyde (0 to 100 μM) in a cyclic fashion or incubated with supernatants collected from treated cells. Healthy cell %, reactive oxygen species (ROS), and proliferation were assessed via flow cytometry, luminescence, scratch wound, and colorimetric assays, respectively. A 15-plex multiplex assay was performed on cell supernatants, followed by IL-6 and IL-8 qRT-PCR and ELISA. Healthy HEMF decreased to less than 80% at 30 mM alcohol and 70 μM acetaldehyde, with microscopic changes at 40 μM acetaldehyde. HEMF ROS was detected at 100 mM alcohol and 80 μM acetaldehyde. Supernatants from 30 mM alcohol- or 40 μM acetaldehyde-treated HEMFs increased Epi proliferation more than two-fold that of lower doses. In the complementary studies, healthy Epi cells decreased to less than 80% at 50 mM and 70 μM acetaldehyde, with microscopic changes at 40 μM. Supernatants from Epi treated with 50 mM alcohol or 40 μM acetaldehyde increased HEMF proliferation more than two-fold that of lower doses. A multiplex assay of supernatants showed the greatest increase in concentrations of IL-6 and IL-8 in HEMFs and in Epi treated with higher doses of alcohol or acetaldehyde. Neutralization of IL-6 and IL-8 in supernatants of HEMFS and esophageal epithelial cells inhibited the proliferation of Epi and HEMFs, respectively. Alcohol and acetaldehyde doses in which the majority of HEMFs and epithelial cells are healthy, elicit the production of paracrine mediators with pro-proliferative effects on neighboring cells. Understanding the effect of alcohol and acetaldehyde on HEMFs and HEMF-epithelial interactions could help to identify the molecular basis by which alcohol increases the risk for esophageal cancer.

Lack of IgA and IgA+ switched memory B cells are associated with bacterial translocation in CVID

BackgroundGut bacterial translocation (BT) is linked to immune activation and inflammatory manifestations in CVID, accompanied by evidence of intestinal barrier defect. Here, we investigated the demographic, immunologic and biochemical parameters associated with BT and gut barrier dysfunction in CVID. MethodsWe measured serum biomarkers of BT (bacterial 16S rDNA [bDNA], by qt-PCR) and intestinal barrier defects (intestinal fatty-acid binding protein [I-FABP], by ELISA) in 88 CVID and 17 healthy control (HC) subjects. B cell phenotypes (% class-switched memory B cells [SMB, CD19 +CD27+IgM-IgD-/CD19+] and % IgA+ SMB [CD19+CD27+IgA+/CD19+]) were enumerated by flow cytometry. Results88 CVID subjects aged 21–62 years were recruited (baseline median IgG 202 [IQR 105–357], IgA 7 [< 5–15], IgM 11 [5–28] mg/dL, and SMB 1% [0.15–2.36%]). Serum bDNA and I-FABP were significantly elevated in CVID vs. HC (P < 0.0001, P < 0.001, respectively). Amongst CVID subjects, serum bDNA correlated with I-FABP levels (Spearman r = 0.27, P = 0.029). Serum bDNA and I-FABP levels were not age-dependent in this adult cohort. There were no sex differences in bDNA levels, though higher I-FABP was observed in males (p = 0.02). Serum bDNA and I-FABP were significantly elevated regardless of overt clinical enteropathy, though those with enteropathy had higher median levels vs. those without.Regarding immunologic and biochemical parameters, high serum bDNA was inversely correlated with 1) %IgA+ SMB (Spearman r = –0.52, P = 0.019, n = 23), and 2) serum IgA (Spearman r = –0.34, P = 0.002). Additionally, bDNA was significantly higher in those with elevated LFTs (P = 0.03). A negative trend between bDNA and total SMB was also observed. Gut barrier defect, as probed by I-FABP, was significantly higher in CVID patients with 1) undetectable IgA (p = 0.03), 2) abnormal liver function tests (p = 0.03), and negatively correlated with 3) CD4+ T cell counts (R = –0.34, p = 0.015). Serum bDNA and I-FABP were not associated with baseline IgG, IgM, or other B/T subsets examined. ConclusionLack of IgA and IgA+SMB are main immunologic parameters associated with BT in CVID, while abnormal LFTs may be an indirect indicator for BT and gut barrier defects. Our data suggest a role of IgA+ B cells/IgA as biological determinants of BT, and a link between BT and liver pathologies in CVID.

Intestinal Epithelial Cell Intrinsic Zinc Homeostasis is Critical for Host-Microbiome Symbiosis

Abstract A robust intestinal barrier is essential for maintaining host-microbiome symbiosis. Defects in the intestinal barrier are associated with a broad range of inflammatory and metabolic diseases. Pharmacological doses of Zinc (Zn) are widely used to improve intestinal barrier function; however, the precise cellular role of Zn in regulating the intestinal barrier during health and disease is not known. A better understanding of how Zn regulates the gut barrier and intestinal epithelial cells (IEC) could enable the development of targeted Zn-based therapeutic approaches. To understand the impact of Zn homeostasis we developed a mouse model with the transcription factor MTF-1 specifically deleted in IECs (MTF ΔIEC). MTF-1 controls the expression of many different zinc importers and exporters. We find that MTF ΔIECmice had reduced expression of Zn homeostasis machinery, demonstrated a leaky barrier, and showed heightened neutrophil activation in the periphery. Additionally, MTF ΔIECmice had a higher bacterial load at the mucosa and were more susceptible to infection by Crohn’s disease associated adherent invasive E.coli. MTF ΔIECmice showed a striking loss of Paneth cells (PCs) from the small intestinal crypts. PCs are specialized antimicrobial-secreting cells with a unique requirement for Zn, but the exact role of Zn in PCs is not known. Based on our findings we conclude that Zn homeostasis is needed for regulating host-microbiome interaction via modulation of intestinal barrier permeability and maintenance of Paneth cells.Our work demonstrating the impact of zinc homeostasis on host-microbe interactions lays the groundwork for understanding zinc in the context of inflammatory bowel disease and dysbiosis in the mucosal microbiome. This work was supported by the NIH [R01DK113265] to Shipra Vaishnava

Intestinal Barrier Repair in Giardiasis

Abstract Giardiasis is a common diarrheal disease caused by the protozoan parasite Giardia duodenalis. Acute symptoms can include diarrhea, but infections are often sub-clinical. It is transmitted via ingesting infectious cysts in contaminated food or water. In developing countries, giardiasis is one of the leading causes of growth stunting in children under two years old. Changes in intestinal barrier integrity have been shown to contribute to impaired nutrient absorption, thereby leading to growth stunting. Although intestinal barrier defects have been linked to infection, there is little understanding of barrier repair dynamics post-infection. Previous studies have demonstrated that Giardia infection is associated with dysbiosis in humans and animals. Because Aryl hydrocarbon receptor (AHR) signaling has been shown to promote intestinal repair in other systems, we are exploring the role of AHR in barrier repair following a Giardia infection. We quantified specific microbiome-derived AHR ligands in the plasma of infected C57BL/6 mice and observed a reduction of indole-3-ethanol and indole-3-pyruvic acid 21 days post-infection. Since IL-22 signaling can also promote barrier repair, we quantified IL-22 transcripts by RT-PCR and found significantly increased levels of IL-22 mRNA in infected mice. These data suggest that Giardia can reduce barrier repair through altered production of AHR ligands by the microbiome, but that IL-22 can counter this effect in some situations. This study will give better insight into developing effective dietary interventions to prevent growth stunting in infected children. Supported by grant from NIH AI166467

Is Alzheimer's disease a manifestation of brain quantum decoherence resulting from mitochondrial and microtubular deterioration?

The etiology of Alzheimer's dementia is, at best multifactorial. Before the emergence of cognitive impairment, symptoms such as thinning of the cortex, accumulation of β-amyloid, and decreased hippocampal volume are common. Hence, the accumulation of β-amyloid and hyperphosphorylated tau fibrillary tangles are two pathological hallmarks in Alzheimer's disease brains, but antibody therapy aimed to decrease β-amyloid has been a failure and, in most optimistic opinions, may delay somewhat disease progression. However, 31-38 % of subjects develop cerebral micro-hemorrhages in aducanumab therapy, an antibody to the amyloid beta plaque by Biogen. Genetics such as Apo E3/E3 have demonstrated defects in the blood-brain barrier in early-onset dementia. Late Onset Alzheimer’s Dementia, has implicated microbe cerebral infections and numerous genetic single nucleotide polymorphisms. However, several cellular biological signatures of Alzheimer's disease have been identified, such as synaptic dysfunction, β-amyloid plaques, hyperphosphorylated tau, cofilin-actin rods, and Hirano bodies which are related to the actin cytoskeleton. Cofilin is one of the most affluent and common actin-binding proteins and plays a role in cell motility, migration, shape, and metabolism. They also play an important role in severing actin filament, nucleating, depolymerizing, and bundling activities. This review summarizes the structure of cofilins appearing after ATP interruptions and deficits in mitochondrial and microtubules and their functional and regulating roles, focusing on the synaptic dysfunction, β-amyloid plaques, hyperphosphorylated tau, cofilin-actin rods, and Hirano bodies of Alzheimer's disease. These findings strengthen our hypothesis that Alzheimer’s dementia is characterized by “Quantum Decoherence” resulting from mitochondrial and microtubular deterioration and responding to near-infrared transcranial photobiomodulation to support mitochondrial and microtubule repair, regrowth and neuronal synaptic renormalization.

The leaky gut and the gut microbiome in sepsis - targets in research and treatment.

Both a leaky gut (a barrier defect of the intestinal surface) and gut dysbiosis (a change in the intestinal microbial population) are intrinsic to sepsis. While sepsis itself can cause dysbiosis, dysbiosis can worsen sepsis. The leaky gut syndrome refers to a status with which there is an increased intestinal permeability allowing the translocation of microbial molecules from the gut into the blood circulation. It is not just a symptom of gastrointestinal involvement, but also an underlying cause that develops independently, and its presence could be recognized by the detection, in blood, of lipopolysaccharides and (1→3)-β-D-glucan (major components of gut microbiota). Gut-dysbiosis is the consequence of a reduction in some bacterial species in the gut microbiome, as a consequence of intestinal mucosal immunity defect, caused by intestinal hypoperfusion, immune cell apoptosis, and a variety of enteric neuro-humoral-immunity responses. A reduction in bacteria that produce short-chain fatty acids could change the intestinal barriers, leading to the translocation of pathogen molecules, into the circulation where it causes systemic inflammation. Even gut fungi might be increased in human patients with sepsis, even though this has not been consistently observed in murine models of sepsis, probably because of the longer duration of sepsis and also antibiotic use in patients. The gut virobiome that partly consists of bacteriophages is also detectable in gut contents that might be different between sepsis and normal hosts. These alterations of gut dysbiosis altogether could be an interesting target for sepsis adjuvant therapies, e.g., by faecal transplantation or probiotic therapy. Here, current information on leaky gut and gut dysbiosis along with the potential biomarkers, new treatment strategies, and future research topics are mentioned.

722 Reversine restores skin barrier defects and attenuates inflammatory responses in atopic dermatitis

722 Reversine restores skin barrier defects and attenuates inflammatory responses in atopic dermatitis

THROUGH A MICROSCOPIC LENS: SKIN MICROBIOME AS THE CONFEDERATE IN ATOPIC DERMATITIS

Reciprocity between skin microbiome and the host underlies the occurrence, exacerbation, and severity of atopic dermatitis (AD). However, the role of skin microbiome in the pathogenesis of AD is yet to be depicted. This review highlights the host–microbiome interactions which relies on barrier status, microbiome composition, and microbe–microbe interactions. A microbiome shift, with abundance of S. aureus and lower microbial diversity, compromises the skin barrier function. It goes to show that epidermal barrier defect depletes the protective commensal skin bacteria and demonstrate how dysbiosis of the skin microbiome can lead to AD.

SDR9C7 missense variant in a Chihuahua with non-epidermolytic ichthyosis.

Ichthyoses represent a heterogeneous group of cornification disorders that are associated with skin barrier defects. We investigated a 9-month-old Chihuahua showing excessive scale formation. Clinical and histopathological examinations revealed non-epidermolytic ichthyosis and a genetic defect was suspected. We therefore sequenced the genome of the affected dog and compared the data with 564 genetically diverse control genomes. Filtering for private variants identified a homozygous missense variant in SDR9C7, c.454C>T or p.(Arg152Trp). SDR9C7 is a known candidate gene for ichthyosis in humans and encodes the short-chain dehydrogenase/reductase family 9C member 7. The enzyme is involved in the production of a functional corneocyte lipid envelope (CLE), a crucial component of the epidermal barrier. Pathogenic variants in SDR9C7 have been described in human patients with autosomal recessive ichthyosis. We assume that the identified missense variant in the affected Chihuahua of this study impairs the normal enzymatic activity of SDR9C7 and thus prevents the formation of a functioning CLE, resulting in a defective skin barrier. To the best of our knowledge, this is the first report of a spontaneous SDR9C7 variant in domestic animals.

Autologous Th2-polarized lymphocytes induce atopic dermatitis lesions in non-atopic human skin xenotransplants.

The key signals that suffice to induce atopic dermatitis (AD) in human skin remain incompletely understood. Also, current mouse models reflect human AD only unsatisfactorily. Therefore, we have asked whether a humanized AD mouse model can be developed that reflects human AD more faithfully and permit to identify key signals that suffice to induce AD lesions in previously healthy human skin in vivo. Healthy human skin from non-atopic donors was transplanted onto SCID/beige mice. After xenotransplant reinnervation by mouse sensory nerve fibers had occurred, mixed autologous human Th2 CD4+ and Tc2 CD8+ T cells that had been pretreated in vitro with IL-2, IL-4, and LPS were injected intradermally into the xenotransplants without skin barrier disruption. Injected non-atopic xenotransplants rapidly developed a morphological, functional, and immunological phenocopy of human AD lesions regarding skin barrier defects, immunopathology including intraepidermal eosinophils, mast cell activation, increase of thymic stromal lymphopoietin, eotaxin-1 and type 2 cytokine circuits, and even showed characteristic neuroimmunological abnormalities such as ß2-adrenergic receptor downregulation. The experimentally induced AD lesions in human skin responded to standard AD therapy (topical dexamethasone or tacrolimus; systemic anti-IL-4Rα antibody [dupilumab]), and relapsed when neurogenic skin inflammation was induced by exposing mice to perceived stress. This new animal model uniquely mimics the complexity of human AD and its clinical response to standard therapy and psychoemotional stressors in vivo, and shows that Th2-polarized lymphocytes associated with excessive IL-4Rα-mediated signaling suffice to induce human AD skin lesions, while atopy and epidermal barrier disruption are dispensable.

Uptake of Tropheryma whipplei by Intestinal Epithelia.

Tropheryma whipplei (TW) can cause different pathologies, e.g., Whipple's disease and transient gastroenteritis. The mechanism by which the bacteria pass the intestinal epithelial barrier, and the mechanism of TW-induced gastroenteritis are currently unknown. Using ex vivo disease models comprising human duodenal mucosa exposed to TW in Ussing chambers, various intestinal epithelial cell (IEC) cultures exposed to TW and a macrophage/IEC coculture model served to characterize endocytic uptake mechanisms and barrier function. TW exposed ex vivo to human small intestinal mucosae is capable of autonomously entering IECs, thereby invading the mucosa. Using dominant-negative mutants, TW uptake was shown to be dynamin- and caveolin-dependent but independent of clathrin-mediated endocytosis. Complementary inhibitor experiments suggested a role for the activation of the Ras/Rac1 pathway and actin polymerization. TW-invaded IECs underwent apoptosis, thereby causing an epithelial barrier defect, and were subsequently subject to phagocytosis by macrophages. TW enters epithelia via an actin-, dynamin-, caveolin-, and Ras-Rac1-dependent endocytosis mechanism and consecutively causes IEC apoptosis primarily in IECs invaded by multiple TW bacteria. This results in a barrier leak. Moreover, we propose that TW-packed IECs can be subject to phagocytic uptake by macrophages, thereby opening a potential entry point of TW into intestinal macrophages.

Gram-positive anaerobic cocci guard skin homeostasis by regulating host-defense mechanisms

In atopic dermatitis (AD), chronic skin inflammation is associated with skin barrier defects and skin microbiome dysbiosis including a lower abundance of Gram-positive anaerobic cocci (GPACs). We here report that, through secreted soluble factors, GPAC rapidly and directly induced epidermal host-defense molecules in cultured human keratinocytes and indirectly via immune-cell activation and cytokines derived thereof. Host-derived antimicrobial peptides known to limit the growth of Staphylococcus aureus-a skin pathogen involved in AD pathology-were strongly upregulated by GPAC-induced signaling through aryl hydrocarbon receptor (AHR)-independent mechanisms, with a concomitant AHR-dependent induction of epidermal differentiation genes and control of pro-inflammatory gene expression in organotypic human epidermis. By these modes of operandi, GPAC may act as an "alarm signal" and protect the skin from pathogenic colonization and infection in the event of skin barrier disruption. Fostering growth or survival of GPAC may be starting point for microbiome-targeted therapeutics in AD.

Experimental models of atopic dermatitis for preclinical researches

Introduction. The development of new methods and technologies for the treatment of atopic dermatitis (AtD) is an urgent medical task due to the growing incidence of the disease, increasing frequency of severe, continuously relapsing forms of dermatosis resistant to both external and systemic therapy. Appropriate experimental models of laboratory animals are needed to test new methods of AtD treatment. The purpose of the study is to describe the technologies of creating experimental models for AtD in laboratory animals to conduct preclinical studies to evaluate the effectiveness of AtD therapy, based on foreign and domestic literature data. Materials and methods. A search in the bibliographic databases PubMed, Scopus, Web of Science, scientific electronic library Elibrary was conducted, 58 sources were selected for the literary review. Search keywords: atopic dermatitis, animal models, mouse models, preclinical studies. Results and discussion. Mouse models are mainly used to reproduce AtD. Experimental mouse models of AtD can be divided into three groups: mice that spontaneously develop skin lesions similar to AtD; models using transgenic mice that either overexpress selective molecules or lack them; models induced cutaneous application of sensitizers. Typically, these models mimic various aspects of human AtD pathophysiology, such as defects in the skin barrier, Th2 predominance, with additional activation of Th1 and Th22 and, in some populations, Th17 immune response. Conclusion. Of the technologies for creating experimental models of AtD in laboratory animals, those with genetic predisposition and allergen-induced models are the closest to human AtD.