The mechanism of selenium regulating the permeability of vascular endothelial cells through selenoprotein O

Vascular diseases, a leading cause of death in human, are strongly associated with pathological damage to blood vessels. The selenoprotein (Sel) have been reported to play important roles in vascular disease. However, the role of SelO in vascular disease has not been conclusively investigated. The present experiment was to investigate the regulatory mechanism of the effect of SelO on the permeability of vascular endothelial. The H.E staining, FITC-Dextran staining, Dil-AC-LDL staining and FITC-WGA staining showed that vascular structure was damaged, and intercellular junctions were disrupted with selenium (Se)-deficient. Immunohistochemistry, qPCR and Western blot revealed decreased expression of the adhesion plaque proteins vinculin, talin and paxillin, decreased expression of the vascular connectivity effector molecules connexin, claudin-1 and E-cadherin and increased expression of JAM-A and N-cadherin, as well as decreased expression of the ZO-1 signaling pathways ZO-1, Rock, rhoGEF, cingulin and MLC-2. In a screening of 24 Sel present in mice, SelO showed the most pronounced changes in vascular tissues, and a possible association between SelO and vascular intercellular junction effectors was determined using IBM SPSS Statistics 25. Silencing of SelO, vascular endothelial intercellular junction adverse effects present. The regulatory relationship between SelO and vascular endothelial intercellular junctions was determined. The results showed that Se deficiency lead to increased vascular endothelial permeability and vascular tissue damage by decreasing SelO expression, suggesting a possible role for SelO in regulating vascular endothelial permeability.

Overview of the compromised mucosal integrity in celiac disease

Intestinal epithelium is a dynamic cellular layer that lines the small-bowel and makes a relatively impenetrable barrier to macromolecules. Intestinal epithelial cell polarity is crucial in coordinating signalling pathways within cells and mainly regulated by three conserved polarity protein complexes, the Crumbs (Crb) complex, partitioning defective (PAR) complex, and Scribble (Scrib) complex. Polarity proteins regulate the proper establishment of the intercellular junctional complexes including tight junctions (TJs), adherence junctions (AJs), and desmosomes which hold epithelial cells together and play a major role in maintaining intestinal barrier integrity. Impaired intestinal epithelial cell polarity and barrier integrity result in irreversible immune responses, the host- microbial imbalance and intestinal inflammatory disorders. Disassembling the epithelial tight junction and augmented paracellular permeability is a conspicuous hallmark of celiac disease (CD) pathogenesis. There are several dietary components that can improve intestinal integrity and function. The aim of this review article is to summarize current information about the association of polarity proteins and AJC damages with pathogenesis of CD.

DPP-4 exacerbates LPS-induced endothelial cells inflammation via integrin-α5β1/FAK/AKT signaling

Endothelial dysfunction plays a pivotal role in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Dipeptidyl peptidase IV (DPP-4), a cell surface glycoprotein, has been implicated in endothelial inflammation and barrier dysfunction. In this study, the role of DPP-4 on lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cells (HPMECs) dysfunction and the underlying mechanism were investigated by siRNA-mediated knockdown of DPP-4. Our results indicated that LPS (1 μg/ml) challenge resulted in either the production and releasing of DPP-4, as well as the secretion of IL-6 and IL-8 in HPMECs. DPP-4 knockdown inhibited chemokine releasing and monolayer hyper-permeability in LPS challenged HPMECs. When cocultured with human polymorphonuclear neutrophils (PMNs), DPP4 knockdown suppressed LPS-induced neutrophil-endothelial adhesion, PMN chemotaxis and trans-endothelial migration. Western blotting showed that DPP-4 knockdown attenuated LPS-induced activation of TLR4/NF-κB pathway. Immunoprecipitation and liquid chromatography-tandem mass spectrometry revealed that DPP-4 mediated LPS-induced endothelial inflammation by interacting with integrin-α5β1. Moreover, exogenous soluble DPP-4 treatment sufficiently activated integrin-α5β1 downstream FAK/AKT/NF-κB signaling, thereafter inducing ICAM-1 upregulation in HPMECs. Collectively, our results suggest that endothelia synthesis and release DPP-4 under the stress of endotoxin, which interact with integrin-α5β1 complex in an autocrine or paracrine manner to exacerbate endothelial inflammation and enhance endothelial cell permeability. Therefore, blocking DDP-4 could be a potential therapeutic strategy to prevent endothelial dysfunction in ALI/ARDS.

The effect of Par3 on the cellular junctions and biological functions of odontoblast-lineage cells

Perfect intercellular junctions are key for odontoblast barrier function. However, whether Partitioning defective-3 (Par3) is expressed in odontoblasts and its potential effects on odontoblast junctions are unknown. Herein, we investigated the effect of Par3 on cellular junctions and the biological behavior of odontoblast-lineage cells (OLCs). Whole-transcriptome sequencing was used to analyze the effects of Par3 on OLCs and the underlying molecular mechanism. Par3 was detected under physiological and inflammatory conditions in OLCs. To investigate the regulatory effect of Par3 on junctions between mouse OLCs, the effects of Par3 downregulation on the proliferation, migration, cycle and apoptosis of OLCs were detected by 5-ethyl-2'-deoxyuridine (EdU) and Transwell assays and flow cytometry. Western blotting and alizarin red S and alkaline phosphatase (ALP) staining were used to observe the effect of Par3 downregulation on OLC mineralization. Whole-transcriptome sequencing was used to investigate the biological role of Par3 in OLCs and potential molecular mechanisms. Par3 was located along the odontoblast layer in the rat pulp tissue and in the cytoplasm of OLCs. Par3 expression was downregulated under inflammatory conditions. The OLC junctions were discontinuous, and total Zona occluden-1 (ZO-1) expression and expression of ZO-1 at the membrane in OLCs were reduced after Par3 silencing (P < 0.05). Expression of a junction-related protein (ZO-1) was downregulated after the downregulation of Par3 (P < 0.05), and ZO-1 moved from the cell membrane to the cytoplasm. OLC proliferation and migration were enhanced, but apoptosis and mineralization were inhibited in shPar3-transfected cells (P < 0.05). Sequencing identified 2996 differentially expressed genes (DEGs), which were mainly enriched in the response to stimuli and binding. Downregulation of Par3 could overactivate the PI3k-AKT pathway by promoting AKT phosphorylation (P < 0.05). Downregulation of Par3 may disrupt junctions between OLCs by affecting ZO-1 expression and distribution and promote OLC proliferation and migration but inhibit OLC mineralization. Par3 may interact with 14-3-3 proteins for PI3K-AKT pathway activation to affect OLC junctions and function.

Intestinal mucosal barrier in functional constipation: Dose it change?

BACKGROUND

The intestinal mucosal barrier is the first line of defense against numerous harmful substances, and it contributes to the maintenance of intestinal homeostasis. Recent studies reported that structural and functional changes in the intestinal mucosal barrier were involved in the pathogenesis of several intestinal diseases. However, no study thoroughly evaluated this barrier in patients with functional constipation (FC).

AIM

To investigate the intestinal mucosal barrier in FC, including the mucus barrier, intercellular junctions, mucosal immunity and gut permeability.

METHODS

Forty FC patients who fulfilled the Rome IV criteria and 24 healthy controls were recruited in the Department of Gastroenterology of China-Japan Friendship Hospital. The colonic mucus barrier, intercellular junctions in the colonic epithelium, mucosal immune state and gut permeability in FC patients were comprehensively examined. Goblet cells were stained with Alcian Blue/Periodic acid Schiff (AB/PAS) and counted. The ultrastructure of intercellular junctional complexes was observed under an electron microscope. Occludin and zonula occludens-1 (ZO-1) in the colonic mucosa were located and quantified using immunohistochemistry and quantitative real-time polymerase chain reaction. Colonic CD3+ intraepithelial lymphocytes (IELs) and CD3+ lymphocytes in the lamina propria were identified and counted using immunofluorescence. The serum levels of D-lactic acid and zonulin were detected using enzyme-linked immunosorbent assay.

RESULTS

Compared to healthy controls, the staining of mucus secreted by goblet cells was darker in FC patients, and the number of goblet cells per upper crypt in the colonic mucosa was significantly increased in FC patients (control, 18.67 ± 2.99; FC, 22.42 ± 4.09; P = 0.001). The intercellular junctional complexes in the colonic epithelium were integral in FC patients. The distribution of mucosal occludin and ZO-1 was not altered in FC patients. No significant differences were found in occludin (control, 5.76E-2 ± 1.62E-2; FC, 5.17E-2 ± 1.80E-2; P = 0.240) and ZO-1 (control, 2.29E-2 ± 0.93E-2; FC, 2.68E-2 ± 1.60E-2; P = 0.333) protein expression between the two groups. The mRNA levels in occludin and ZO-1 were not modified in FC patients compared to healthy controls (P = 0.145, P = 0.451, respectively). No significant differences were observed in the number of CD3+ IELs per 100 epithelial cells (control, 5.62 ± 2.06; FC, 4.50 ± 2.16; P = 0.070) and CD3+ lamina propria lymphocytes (control, 19.69 ± 6.04/mm²; FC, 22.70 ± 11.38/mm²; P = 0.273). There were no significant differences in serum D-lactic acid [control, 5.21 (4.46, 5.49) mmol/L; FC, 4.63 (4.31, 5.42) mmol/L; P = 0.112] or zonulin [control, 1.36 (0.53, 2.15) ng/mL; FC, 0.94 (0.47, 1.56) ng/mL; P = 0.185] levels between FC patients and healthy controls.

CONCLUSION

The intestinal mucosal barrier in FC patients exhibits a compensatory increase in goblet cells and integral intercellular junctions without activation of mucosal immunity or increased gut permeability.

[Research Updates: Relationship between Gingival Epithelial Intercellular Junctions and Periodontal Pathogenic Bacteria]

Gingival epithelial barrier is the first line of defense of periodontal tissues against the invasion of pathogenic bacteria. The destruction of gingival epithelial barrier is closely related to the development of periodontal disease. Studies have shown that periodontal pathogenic bacteria and their inflammatory microenvironment can inhibit the expression of gingival epithelial junctional proteins via molecular mechanisms such as the downregulation of the expression of grainyhead-like protein family and the upregulation of the methylation level of gene promoter of epithelial connexin, and thus cause damage to the gingival epithelial barrier and the development of periodontitis. We herein reviewed the effects of bacteria and inflammatory factors induced by bacterial infection on gingival epithelial intercellular junctions and related mechanisms, and summarized the research progress on the relationship between gingival epithelial intercellular junctions and periodontal pathogenic bacteria in recent years. Most recent studies were focused on i n vitro cytological experiments and animal models of infections caused by a single kind of bacterium. We have suggested that building gingival epithelial organoid model and combining multi-omics approaches with high resolution three-dimensional electron microscopy are expected to help pinpoint the key microorganisms and their most important virulence factors that trigger periodontal microecologcal imbalance and cause functional damage to the gingival epithelial barrier, to reveal the key molecular mechanisms involved in the maintenance and destruction of gingival epithelial barrier function, and to provide new perspectives on the pathogenesis and the clinical prevention and treatment of periodontitis.

The unusual cytoarchitecture of "vitelline follicles" in freshwater blood flukes of the genus Sanguinicola (Digenea, Aporocotylidae)

This is the first study assessing the cytoarchitecture of the vitellarium of members of the freshwater, teleost-infecting lineage of blood-flukes (Aporocotylidae). The vitelline cytoarchitecture of two innominate species of Sanguinicola from freshwater fishes in Russia showed that vitelline cells at different stages of maturation are widely distributed throughout much of the body and are mixed with other cell types. The latter feature indicates that use of the term "follicular vitellarium" is inappropriate for species of this genus. An additional characteristic of the vitelline cells in these Sanguinicola spp. is their ability to form long, pseudopodia-like extensions of the peripheral cytoplasm that contact neighbouring vitelline cells and sarcoplasmic extensions, forming both heterologous and homologous intercellular junctions. Within the vitelline duct lumen, the cytoplasm of mature vitelline cells is filled with regular clusters (0.5-1.0 μm in diameter), comprising 10-30 vitelline globules, which have heterogeneous contents and electron-lucent lipid droplets (1.1-1.7 μm in diameter), but no apparent modifications of vitelline globules occur within the vitelline duct. The flattened, ciliated, epithelial lining of the common vitelline duct contains intra-epithelial nuclei, its luminal surface bears shallow lamellae and adjacent cells are adjoined by apical septate junctions. All of these observations, when compared to the marine Aporocotyle simplex, likely represent additional characteristics supporting the divergent evolutionary lineages of marine and freshwater aporocotylids.

Environmental contaminant ammonia triggers epithelial-to-mesenchymal transition-mediated jejunal fibrosis with the disassembly of epithelial cell-cell contacts in chicken

Ammonia (NH₃) is an environmental contaminant that is causing increasing problems with human and animal health due to the development of poultry industry. There are limited studies on the effect of NH₃ inhalation toxicity on the intestinal tract of animals, and underlying molecular mechanisms remain unclear. In the present study, we established a chicken model of NH₃ aspiration-induced injury for 42 days and observed histopathological changes of the jejunum. Tandem mass tag-based quantitative proteomic analysis was applied to investigate changes in the protein profile in the jejunum tissue of chickens that were exposed to NH₃. Overall, 48 significantly differentially expressed proteins (DEPs) were identified. GO and KEGG analyses revealed that most DEPs were closely related to epithelial-to-mesenchymal transition (EMT), cell-cell junctions, and fibrosis-related factors. Regarding fibrosis, type I collagen and fibronectin were significantly increased. With respect to EMT, epithelial marker proteins (such as E-cadherin and keratin) were repressed, while mesenchymal marker proteins (such as vimentin) were activated. Loss of epithelial cell-cell junctions (such as tight junctions, adherens junctions and desmosomes) were observed. Additionally, overexpression of transforming growth factor-beta (TGF-β) may play a key role in the EMT process and fibrosis. Taken together, these findings suggested that NH₃ triggered the EMT and disassembly of epithelial cell-cell contacts, resulting in jejunal fibrosis that was mediated by TGF-β in chickens. The results of our study will contribute to provide a technical reference regarding the research methods of intestinal toxicity of NH₃ and have largely regulatory implications for ecological risk assessment of human health.

Assessing functional status of cardiac lymphatics: From macroscopic imaging to molecular profiling

Here we describe various techniques for visualization of the lymphatic vasculature, particularly in the heart. Addressing macro-, microscopic, and molecular levels of lymphatic organization, we give examples of how to explore the roles of specific antigens/markers expressed in lymphatic vessels and their extracellular matrix as structural and functional elements involved in various biological functions of lymphatics. Some obstacles and technical challenges related to lymphatic visualization are also discussed.

Stabilization of microtubules restores barrier function after cytokine-induced defects in reconstructed human epidermis

BACKGROUND

A variety of human skin disorders is characterized by defects in the epidermal barrier, leading to dehydration, itchiness, and rashes. Previously published literature suggests that microtubule stabilization at the cortex of differentiating keratinocytes is necessary for the formation of the epidermal barrier.

OBJECTIVES

We tested whether stabilization of microtubules with paclitaxel or epothilone B can repair barrier defects that were experimentally induced in three-dimensional culture models of epidermis.

METHODS

We established two models of defective epidermis in vitro, using three-dimensional cultures of primary human keratinocytes on filter supports: immature reconstructed human epidermis (RHE), and RHE that was compromised by treatment with inflammatory cytokines, the latter mimicking defects seen in atopic dermatitis.

RESULTS

Both paclitaxel and epothilone B promoted keratinocyte differentiation, accumulation of junctional proteins at the cell cortex, and the early appearance of lamellar bodies in immature RHE, whereas destabilization of microtubules by nocodazole had the reverse effect. Moreover, stabilization of microtubules rescued the barrier after cytokine treatment. The rescued barrier function correlated with the restoration of filaggrin and loricrin protein levels, the cortical accumulation of junctional proteins (E-cadherin, β-catenin, and claudin-1), and with the secretion of lamellar bodies.

CONCLUSIONS

Our data suggest that the microtubule network is important for the formation of the epidermis, and that stabilization of microtubules promotes barrier formation. Microtubule stabilization may support regeneration of damaged skin, by restoring or improving the barrier.

Preparation of Testicular Samples for Histology and Immunohistochemistry

One approach to visualize internal structures of the testis is histological sectioning of the material. The use of testicular samples allows a detailed analysis of the structure of both seminiferous tubules and the interstitial space. It is worth noting that key role in the control of germ cell development is assigned to Sertoli cells. Thus, in this chapter the special reference is made on visualization of Sertoli cells in the seminiferous epithelium in which they create a specialized microenvironment to support the germ cell development through the formation of the blood-testis barrier (BTB). The use of transmission electron microscopy (TEM) allows a deeper insight into the BTB morphology, especially the organization of the basal ectoplasmic specialization (ES) and coexisting intercellular junctions.Equally important, immunohistochemistry (IHC) is an appropriate technique to detect the localization of various proteins in paraffin-embedded and fixed tissues, i.e. testicular samples. A proper fixation allows to stabilize structure of the seminiferous tubules and preserve cells against irreversible damage. As such localization of various junction proteins connecting adjoined Sertoli cells and present in germ cell-Sertoli cell interfaces is possible. Also immunofluorescence (IF) is helpful to detect the distribution and relative abundance of the junctional proteins, while immunocytochemistry (ICC) is a valuable technique to show a protein distribution within a single cell (e.g. in Sertoli cell culture).

Locomotory control in amphioxus larvae: new insights from neurotransmitter data

Amphioxus larvae have a midbrain-level locomotory control center whose overall organization is known from serial TEM reconstructions. How it functions has been a puzzle, owing to uncertainty as to the transmitters used by each class of neurons, but this has recently become clearer. We summarize what is now known, and correct past misconceptions: The large paired neurons at the core of the control center are glutamatergic, and hence excitatory, the commissural neurons are GABAergic, hence probably inhibitory, and both motoneurons and ipsilateral projection neurons are cholinergic, suggesting that the latter, a class of interneurons, may be derived evolutionarily from the former. The data clarify some aspects of how fast and slow swimming are controlled and prevented from interfering with one another, but leave open the source of pacemaker activity, which could reside in the large paired neurons or circuits associated with them. A unusual type of non-synaptic junction links the fast and slow systems, but how these junctions function is open to interpretation, depending chiefly on whether they act to couple adjacent cells independent of cell type, or can have differential effects that vary with cell type. Some evolutionary implications are discussed.

Twist1-positive epithelial cells retain adhesive and proliferative capacity throughout dissemination

Dissemination is the process by which cells detach and migrate away from a multicellular tissue. The epithelial-to-mesenchymal transition (EMT) conceptualizes dissemination in a stepwise fashion, with downregulation of E-cadherin leading to loss of intercellular junctions, induction of motility, and then escape from the epithelium. This gain of migratory activity is proposed to be mutually exclusive with proliferation. We previously developed a dissemination assay based on inducible expression of the transcription factor Twist1 and here utilize it to characterize the timing and dynamics of intercellular adhesion, proliferation and migration during dissemination. Surprisingly, Twist1(+) epithelium displayed extensive intercellular junctions, and Twist1(-) luminal epithelial cells could still adhere to disseminating Twist1(+) cells. Although proteolysis and proliferation were both observed throughout dissemination, neither was absolutely required. Finally, Twist1(+) cells exhibited a hybrid migration mode; their morphology and nuclear deformation were characteristic of amoeboid cells, whereas their dynamic protrusive activity, pericellular proteolysis and migration speeds were more typical of mesenchymal cells. Our data reveal that epithelial cells can disseminate while retaining competence to adhere and proliferate.

Quantifying cell behaviors in negative-pressure induced monolayer cell movement

Background

Negative-pressure of 125 mmHg (NP) has been shown to accelerate wound healing. Effects of NP on human keratinocyte behaviors during wound healing process were highlighted in this study.

Methods

An NP incubator incorporating the electric cell–substrate impedance sensing (ECIS) technique has been built to quantify monolayer keratinocytes movement in serum-free media at the ambient pressure (AP) and NP for 12 h. Monolayer cell motions were continuously recorded by ECIS in the frequency range of 22.5–64 kHz. Membrane capacitance (C_m), cell–substratum resistance (α), and cell–cell junction resistance (R_b) were evaluated in cells at the different pressures.

Results

A greater monolayer cell migration distance was found in cells at NP. Decreased cell–substratum adhesion reflected in the significantly low α (AP:NP = ∼5 Ω^0.5:∼3 Ω^0.5⋅cm), decreased integrin expression, and increased cell–substratum distance were seen in cells at NP. A significantly increased C_m (AP:NP = ∼4:∼8 μF/cm²) in association with increased membrane ruffling and microtubule filaments were observed early in the monolayer cell movement at NP. A progressive drop in the R_b from 1.2 Ω·cm² to 0.8 Ω·cm² corresponding to the gradually decreased E-cadherin expressions were observed 6 h after wound closure after NP treatment.

Conclusion

A quick membrane ruffling formation, an early cell–substratum separation, and an ensuing decrease in the cellular interaction occur in cells at NP. These specific monolayer cell behaviors at NP have been quantified and possibly accelerate wound healing.

Developmental changes in intercellular junctions and Kv channels in the intestine of piglets during the suckling and post-weaning periods

Background

The intestinal epithelium is an important barrier that depends on a complex mixture of proteins and these proteins comprise different intercellular junctions. The purpose of this study was to investigate the postnatal and developmental changes in morphology, intercellular junctions and voltage-gated potassium (Kv) channels in the intestine of piglets during the suckling and post-weaning periods.

Results

Samples of the small intestine were obtained from 1-, 7-, 14-, and 21-d-old suckling piglets and piglets on d 1, 3, 5, and 7 after weaning at 14 d of age. The results showed that the percentage of proliferating cell nuclear antigen (PCNA)-positive cells and alkaline phosphatase (AKP) activity, as well as the abundances of E-cadherin, occludin, and Kv1.5 mRNA and claudin-1, claudin-3, and occludin protein in the jejunum were increased from d 1 to d 21 during the suckling period (P < 0.05). Weaning induced decreases in the percentage of PCNA-positive cells, AKP activity and the abundances of E-cadherin, occludin and zonula occludens (ZO)-1 mRNA or protein in the jejunum on d 1, 3 and 5 post-weaning (P < 0.05). There were lower abundances of E-cadherin, occludin and ZO-1 mRNA as well as claudin-1, claudin-3 and ZO-1 protein in the jejunum of weanling piglets than in 21-d-old suckling piglets (P < 0.05). The abundances of E-cadherin, occludin, ZO-1 and integrin mRNA were positively related to the percentage of PCNA-positive cells.

Conclusion

Weaning at 14 d of age induced damage to the intestinal morphology and barrier. While there was an adaptive restoration on d 7 post-weaning, the measured values did not return to the pre-weaning levels, which reflected the impairment of intercellular junctions and Kv channels.

Beta-7 integrin controls enterocyte migration in the small intestine

AIM: To hypothesize that beta-7 integrin affects cellular migration of both, lymphocytes and enterocytes.

METHODS: The nucleoside analog BrdU was ip injected in beta-7-deficient mice (C57BL/6-Itgb^tmlcgn/J) of male gender and age-matched male C57BL/J J mice (wild type) 4, 20, or 40 h before analysis. The total small intestine was isolated, dissected, and used for morphometrical studies. BrdU-positive epithelial cells were numbered in at least 15 hemi-crypts per duodenum, jejunum, and ileum of each animal. The outer most BrdU-positive cell (cell^max) was determined per hemi-crypt, numerically documented, and statistically analysed.

RESULTS: Integrins containing the beta-7-chain were exclusively expressed on leukocytes. In the small intestinal mucosa of beta-7 integrin-deficient mice the number of intraepithelial lymphocytes was drastically decreased. Moreover, the Peyer’s patches of beta-7 integrin-deficient mice appeared hypoplastic. In beta-7 integrin-deficient mice the location of cell^max was found in a higher position than it was the case for the controls. The difference was already detected at 4 h after BrdU application, but significantly increased with time (40 h after BrdU injection) in all small intestinal segments investigated, i.e., duodenum, jejunum, and ileum. Migration of small intestinal enterocytes was different between the experimental groups measured by cell^max locations.

CONCLUSION: The E-cadherin beta-7 integrin pathway probably controls migration of enterocytes within the small intestinal surface lining epithelial layer.