Article

Altered claudin expression is a feature of chronic plaque psoriasis

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Abstract

Epithelial tight junctions play a central role in cell-cell adhesion and are necessary for the selective paracellular movement of ions. Claudins are key components of tight junctions and their expression is altered in gut epithelia in a variety of inflammatory enteropathies, including ulcerative colitis and Crohn's disease. Psoriasis is a chronic inflammatory skin disease affecting approximately 2% of the western population, with significantly increased occurrence in individuals with Crohn's disease. Initial studies investigated the expression of claudins in skin of healthy volunteers and patients with chronic plaque psoriasis. We report here that claudins-1 and -3 are the major protein species present in the epidermis of healthy skin; they are expressed on the surface of epidermal keratinocytes, consistent with their localization to tight junctions. In plaques of psoriasis, claudin-1 was not identifiable in the epidermis, although typical staining patterns were observed in clinically normal, uninvolved skin of patients with psoriasis. Claudin-3 was present in the epidermal granular cell layer in normal skin, but was only identified within the cytosol of epidermal keratinocytes in both involved and uninvolved skin of psoriasis patients. We examined further whether exposure of keratinocytes in vitro to pro-inflammatory cytokines mimicked the observed changes in claudin expression seen in chronic plaque psoriasis; lipopolysaccharide, interferon-gamma and tumour necrosis factor-alpha had no effect on claudin protein expression or distribution. Addition of interleukin-1beta, however, resulted in down-regulation of claudins-1 and -3. Tumour necrosis factor-alpha and interleukin-1beta were further used in an in vivo model of skin inflammation; interleukin-1beta alone modulated claudin protein expression in this system. These data demonstrate that epidermal claudin expression is altered in chronic plaque psoriasis and that expression is in part modulated by interleukin-1beta.

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... Proinflammatory cytokines like interleukin (IL)-1β and tumor necrosis factor alpha (TNFα) have been shown to increase and decrease TJ function in a time-dependent manner in NHEKs which is accompanied by an up-and down-regulation and relocalization of TJ proteins [71]. Dermal injection of IL-1β into healthy volunteers results in down-regulation of Cldn-1 [72]. In ex-vivo skin it leads to a broader localization of Ocln and ZO-1 as well as to up-regulation of ZO-1 on protein level [71]. ...
... In non-lesional skin, no TJ protein alterations are observed [72,73,124]. In early stages of lesional skin, Cldn-1 and Cldn-7 are downregulated in the uppermost and lowermost layers while a broader localization of ZO-1, Ocln and Cldn-4 is observed [71]. ...
... elevated levels of certain cytokines, contribute to the alteration of TJ proteins. As already described above (Section 2.1.2.2), injection of IL-1β into the skin of healthy volunteers results in down-regulation of claudin-1 [72]. In ex-vivo skin, it leads to a broader localization of occludin and ZO-1 [71]. ...
Article
The skin protects our body from external assaults like pathogens, xenobiotics or UV irradiation. In addition, it prevents the loss of water and solutes. To fulfill these important tasks, a complex barrier system has developed which comprises the stratum corneum, tight junctions, the microbiome, the chemical barrier and the immunological barrier. These barriers do not act separately, but influence each other e.g. after external manipulation or in skin diseases. Especially the two mechanical barriers, i.e. stratum corneum and tight junctions, are of great interest for drug delivery, because they are the first interaction partners of drug delivery systems and play the major role in skin absorption. Tight junctions are of special interest, as they are centrally localized in this complex barrier system in the outermost viable layer - the stratum granulosum of the interfollicular epidermis and the companion cell layer of the hair follicle - and because they can react very quickly to stimuli. We summarize here our current knowledge about tight junction barrier function in mammalian interfollicular epidermis and hair follicles, and the interaction of tight junctions with other skin barrier components in health and disease. Furthermore, we discuss their relevance for drug delivery and provide examples for tight junction modulators.
... [7,8] This suggests that claudin integrity is essential for health and the altered expression has a role in the pathogenesis of diseases of simple epithelia. [9] A similar association of altered claudin-1 expression has been seen in inflammatory diseases affecting the stratified epithelia such as skin. [10] Psoriasis is a common remitting and relapsing chronic inflammatory skin disease. ...
... Immunofluorescence demonstrated the lack of claudin-1 expression in the lower layers. [9] Their in vivo model showed downregulation of claudin-1 following intradermal injection of interleukin 1β in controls. [9] Similar results were seen in the study by Kirschner et al. indicating an important role of cytokines in the regulation of expression of tight junction proteins including claudin-1 in the pathogenesis of psoriasis. ...
... [9] Their in vivo model showed downregulation of claudin-1 following intradermal injection of interleukin 1β in controls. [9] Similar results were seen in the study by Kirschner et al. indicating an important role of cytokines in the regulation of expression of tight junction proteins including claudin-1 in the pathogenesis of psoriasis. [16] Reduced expression of Vitamin D receptor, an antiproliferative and pro-differentiation driver in the keratinocytes correlates with downregulation of claudin-1 in cases of psoriasis by immunohistochemistry was shown by Visconti et al. [17] Pan et al. illustrated a negative correlation of interleukin-36γ with expression of claudin-1 in psoriasis by immunohistochemistry. [18] Loss of expression of claudin-1 was associated with high proliferative activity of keratinocytes, as enumerated by Ki67 expression in the index study. ...
Article
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Background: Psoriasis is a chronic remitting and relapsing inflammatory disease, with a prevalence of 0.44%–2.5% and is characterized by T-cell-mediated rapid turnover of epithelial cells. Claudin-1 protein is an integral part of the keratinocyte tight junction and has a role in proliferation, differentiation, and cell adhesion. Aim: The aim of the study was to investigate the role of claudin-1 expression in relation to keratinocyte proliferation in psoriasis. Materials and Methods: Fifty cases of psoriasis were included in the study. Skin biopsies were subjected to claudin-1 and Ki67 immunohistochemistry. Claudin-1 expression in the basal and spinous layers was scored. Ki67 proliferation index was assessed. Seven cases of normal skin biopsies were also included as controls. Fisher’s exact test was applied for statistical analysis. Results: The cases had a wide age range (14–78 years), with a mean of 46 years with a male preponderance (4:1). The basal cell layer showed a complete loss of expression for claudin-1 in 82% (n = 42). The spinous layer showed a decrescendo pattern of loss of claudin-1 expression in 96% (n = 48). The association of loss of expression of claudin-1 between the basal layer and spinous layer was statistically significant (P = 0.0229). The association of loss of expression of claudin-1 and high Ki67 proliferative index was also statistically significant (P < 0.00001). Conclusion: Our study showed consistent loss of expression of claudin-1 in the lower layers of the epidermis in psoriasis, which is also the site of intense proliferative activity. The cytokine soup released by the T-cells may be responsible for downregulation of claudin-1, which is one of the triggers for proliferation.
... In peridermalen Zellen sind typische TJ-Strukturen in der 17. Woche zu sehen (PUMMI et al., 2001) (PUMMI et al., 2001;YOSHIDA et al., 2001;BRANDNER et al., 2006;PELTONEN et al., 2007;WATSON et al., 2007). ...
... Epidermis (BRANDNER et al., 2006;WATSON et al., 2007) (FOX et al., 1994;HIRANO et al., 1994;MACKAY et al., 1994;SEITER et al., 1998), das 20 Exons umfasst, von denen 10 Exons durch alternatives Spleißen reguliert werden können. Die Expression der varianten Isoformen unterscheidet sich abhängig von Zelltyp und Wachstumsbedingungen (SCREATON et al., 1993). ...
... In Plaque-Psoriasis wurde bereits gezeigt, dass eine veränderte Lokalisation von TJ-Proteinen vorliegt (PUMMI et al., 2001;YOSHIDA et al., 2001;BRANDNER et al., 2006;PELTONEN et al., 2007;WATSON et al., 2007). Um zu klären, ob dies eine späte ...
... Thus, in principle, cCPE could influence one, several or all of these proteins. Because claudin-3, even though present at the protein level in keratinocytes, does not seem to be regularly localized at TJs in the epidermis (Hintsala et al. 2013;Tatari et al. 2014;Tebbe et al. 2002;Troy et al. 2007;Watson et al. 2007;Mathes et al., in preparation) and claudin-6 has up to now only been detected in mouse skin (Arabzadeh et al. 2006;Turksen and Troy 2002) but not in (adult) human skin (Kast et al. 2012), the effect of cCPE in RHS is most likely mediated via claudin-4 and -7, both of which have been described to be localized at cell-cell junctions in the SG of human epidermis ( Table 1). The mRNA of claudin-8 has been described in human skin and cultured keratinocytes but protein localization is not yet clear. ...
... There are no TJ protein alterations in non-involved skin of psoriasis vulgaris (De Benedetto et al. 2011;Peltonen et al. 2007;Watson et al. 2007), pointing to secondary TJ alterations associated with disease activity. In involved psoriatic skin, a down-regulation of claudin-1 (Brandner et al. 2006;Kirschner et al. 2009;Watson et al. 2007) and claudin-7 (Kirschner et al. 2009) and a broader localization of ZO-1 and occludin (Brandner et al. 2006;Kirschner et al. 2009;Peltonen et al. 2007;Pummi et al. 2001;Yoshida et al. 2001) as well as increased cytoplasmic staining (Kirschner et al. 2009) were observed. ...
... There are no TJ protein alterations in non-involved skin of psoriasis vulgaris (De Benedetto et al. 2011;Peltonen et al. 2007;Watson et al. 2007), pointing to secondary TJ alterations associated with disease activity. In involved psoriatic skin, a down-regulation of claudin-1 (Brandner et al. 2006;Kirschner et al. 2009;Watson et al. 2007) and claudin-7 (Kirschner et al. 2009) and a broader localization of ZO-1 and occludin (Brandner et al. 2006;Kirschner et al. 2009;Peltonen et al. 2007;Pummi et al. 2001;Yoshida et al. 2001) as well as increased cytoplasmic staining (Kirschner et al. 2009) were observed. This is already seen in early stages of psoriasis (Kirschner et al. 2009) and is reversed in healed lesions (Peltonen et al. 2007). ...
Article
The tight junction (TJ) regulates paracellular barrier properties. TJs are composed of transmembrane proteins, i.e., claudins, occludin, tricellulin and junctional adhesion molecules as well as TJ plaque proteins. Their relative abundance and composition determines epithelial tightness. TJs undergo rapid regulation by various signalling pathways, either directly addressing TJ transmembrane proteins or via plaque proteins and the cytoskeleton. In the skin, TJs exert predominantly barrier functions, while in the intestine they also mediate paracellular ion and water transport. In diseases, TJs can either be primarily affected (hereditary TJ defects) or changes can result from secondary regulatory inputs as, e.g., in inflammatory diseases (secondary TJ defects). Secondary TJ defects can maintain disease activity, e.g., by enhanced antigen leak. This review discusses TJ composition, function and regulation as well as primary and secondary tight junction defects in a comparative manner in skin and intestine in order to elucidate similarities and differences.
... As is well known, psoriasis has long been associated with skin barrier dysregulation [6], in which tight junction (TJ), as an important component in epidermal barrier function, is also seen to be clearly altered in psoriasis [7,8]. Claudin-1, a composition of TJ proteins that are extremely important to skin barrier, is reported to be downregulated in the uppermost and lowermost layers in early stages of skin lesion [9][10][11], while in the late stages of skin lesion, it is often completely absent [10]. Until now, there is little consensus on Claudin-1 patterns in psoriatic skin. ...
... As is well known, psoriasis has long been associated with skin barrier dysregulation [6], in which tight junction (TJ), as an important component in epidermal barrier function, is also seen to be clearly altered in psoriasis [7,8]. Claudin-1, a composition of TJ proteins that are extremely important to skin barrier, is reported to be downregulated in the uppermost and lowermost layers in early stages of skin lesion [9][10][11], while in the late stages of skin lesion, it is often completely absent [10]. Until now, there is little consensus on Claudin-1 patterns in psoriatic skin. ...
Article
Full-text available
Objective: This study aimed to estimate serum IL-17A and Claudin-1 levels, investigate their correlation, and evaluate their diagnostic significance as potential blood-based biomarkers in psoriasis. Methods: Serum IL-17A and Claudin-1 concentrations were determined using enzyme-linked immunosorbent assay (ELISA). Statistical analyses were performed to determine differences in serum levels of IL-17A and Claudin-1, their bivariable correlation with psoriasis severity, as Psoriasis Area Severity Index (PASI), and their predictive abilities using receiver operating characteristic (ROC) curves. Results: Significantly higher IL-17A and lower Claudin-1 levels were found in psoriasis (p < 0.05). PASI did not correlate significantly with either IL-17A or Claudin-1 in psoriasis and their subtypes. The only significant correlation between serum IL-17A and Claudin-1 was shown in late-onset psoriasis (r = 0.630, p = 0.028). ROC curve analysis indicated the serum IL-17A, serum Claudin-1, and combination of IL-17A and serum Claudin-1 for predicting psoriasis with the areas under the curve (AUC) of 0.951 (p < 0.0001), 0.709 (p = 0.0119), and 0.949 (p < 0.0001), respectively. Moreover, the potential role in distinguishing between early-onset and late-onset psoriasis: we obtained serum IL-17A, serum Claudin-1, and their combination AUC of 0.590 (p = 0.3126), 0.741 (p = 0.0045), and 0.741 (p = 0.0067), respectively. However, none of the serum IL-17A, serum Claudin-1, and their combination was well-performed discriminating mild psoriasis from moderate-to-severe psoriasis with AUC of 0.553 (p = 0.5596), 0.518 (p = 0.8539), and 0.559 (p = 0.5225), respectively. Conclusion: These preliminary results suggest that the serum Claudin-1 as a potential biomarker and the relationship and possible regulatory interactions between IL-17A and Claudin-1 in psoriasis are distinguishable by age of onset.
... Kirschnera and coresearchers demonstrated Ocln-and Cldn-1-positive sites in the SG (human skin) form a barrier for extracellular Biotin-SH (557 Da), and that in psoriatic skin the localization of the barrier and the TJ proteins are altered in parallel [75]. However, downregulation of Cldn-1 has also been described in psoriatic plaques in other investigations [70,76]. Troy et al. used transgenic animals to show that with aging and chronic dermatitis, certain structural changes are encountered in the epidermis associated with barrier dysfunctioning that was manifested by increased transepidermal water loss [44]. ...
... In contrast, TJ proteins that are normally localized in all layers of the epidermis, that is, Cldn-1 are down-regulated. Watson et al. suggested that IL-1b, which is produced by keratinocytes and monocytes/macrophages, plays a role in downregulation [76]. Real-time PCR revealed a decreased level of Cldn-1 mRNA in psoriatic skin compared with that in normal skin, whereas there was no change in the levels of Cldn-7 and JAM-A [70]. ...
Article
Full-text available
Tight junctions (TJs) are intercellular contacts that seal the space between the individual cells of an epithelial sheet or stratifying epithelia, such as the epidermis, so that they can collectively separate tissue compartments. Intercellular junctions, such as adherens and TJs, play a crucial role in the formation and maintenance of epithelial and endothelial barriers. A variety of components including claudins, occludin, tricellulin, zonula occluden proteins and junctional adhesion molecules have been identified in complex localization patterns in mammalian epidermis. In several skin diseases that are characterized by impaired skin barrier function, altered proliferation/differentiation of the epidermis and/or infiltration of inflammatory cells, altered expression patterns of TJ proteins have been observed. This review is aimed at providing an insight into the molecular composition, tools for identification and understanding the role of TJs in skin diseases and barrier function regulation.
... Whether this severe later phenotype, which ultimately leads to the death of the animals, reflects a separate, non-TJ, role for the protein in wound repair is unclear. Mislocalization of CLDN1 is a feature of a number of cutaneous diseases such as psoriasis [40], and in a number of cancers [36,41,42]. KRT76 depletion has also been linked with human oral carcinomas and premaligant epidermal changes [43]. ...
Article
Full-text available
Keratins are cytoskeletal intermediate filament proteins that are increasingly being recognised for their diverse cellular functions. Here we report the consequences of germ line inactivation of Keratin 76 (Krt76) in mice. Homozygous disruption of this epidermally expressed gene causes neonatal skin flaking, hyperpigmentation, inflammation, impaired wound healing, and death prior to 12 weeks of age. We show that this phenotype is associated with functionally defective tight junctions that are characterised by mislocalization of the integral protein CLDN1. We further demonstrate that KRT76 interacts with CLDN1 and propose that this interaction is necessary to correctly position CLDN1 in tight junctions. The mislocalization of CLDN1 has been associated in various dermopathies, including the inflammatory disease, psoriasis. These observations establish a previously unknown connection between the intermediate filament cytoskeleton network and tight junctions and showcase Krt76 null mice as a possible model to study aberrant tight junction driven skin diseases.
... In psoriatic lesions, Cldn-1 is down-regulated in some areas in the uppermost and lower layers, 9 whereas in other areas, it is almost completely lost. 9,45,46 Interestingly, treatment of ex vivo models with IL-1b (prominent in early-stage psoriasis) resulted in a downregulation of Cldn-1 in the uppermost layers, but not in the lower layers, which is in contrast to our findings regarding the treatment of RHEs with the IL-4/IL-13/IL-31 mixture. In squamous cell carcinoma and its precursors, there is a frequent down-regulation of Cldn-1 in the lower epidermal layers. ...
Article
Tight junctions are important for skin barrier function. The tight junction protein claudin 1 (Cldn-1) has been reported to be down-regulated in nonlesional skin of atopic dermatitis (AD) patients. In contrast, we did not observe a significant down-regulation of Cldn-1 in nonlesional skin of the AD cohort used in this study. However, for the first time, a significant down-regulation of Cldn-1 in the upper and lower epidermal layers of lesional skin was detected. In addition, there was a significant up-regulation of Cldn-4 in nonlesional, but not lesional, AD skin. For occludin, no significant alterations were observed. In an AD-like allergic dermatitis mouse model, Cldn-1 down-regulation in eczema was significantly influenced by dermal inflammation, and significantly correlated with hallmarks of eczema (ie, increased keratinocyte proliferation, altered keratinocyte differentiation, increased epidermal thickness, and impaired barrier function). In human epidermal equivalents, the addition of IL-4, IL-13, and IL-31 resulted in a down-regulation of Cldn-1, and Cldn1 knockdown in keratinocytes resulted in abnormal differentiation. In summary, we provide the first evidence that Cldn-1 and Cldn-4 are differentially involved in AD pathogenesis. Our data suggest a role of Cldn-1 in AD eczema formation triggered by inflammation. Copyright © 2015 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.
... There is currently no consensus about cldn-1 patterns as some report no differences and others show reduced expression at different strata of the epidermis. 65,84,[86][87][88] The reason for such variability is unclear to us. Unfortunately, the published studies do not allow for correlation of the staining results with any particular feature, such as disease severity, age of the PS plaques (e.g., acute vs chronic), systemic or local treatment, anatomical localization (e.g., sun-exposed) or even staining procedures (e.g., reagents, skin processing). ...
Article
The skin, the largest organ of the body, is an essential barrier that under homeostatic conditions efficiently protects and/or minimizes damage from both environmental (e.g. microorganisms, physical trauma, ultraviolet radiation) and endogenous (e.g., cancers, inflammation) factors. This formidable barrier function resides mainly in the epidermis, a dynamic, highly-stratified epithelium. The epidermis has 2 major barrier structures: stratum corneum, the outmost layer and tight junctions, intercellular junctions that seal adjacent keratinocytes in the stratum granulosum, found below the stratum corneum. In recent years there have been significant advances in our understanding of tight junction function, composition and regulation. Herein we review what is known about tight junctions in healthy skin and keratinocyte culture systems and highlight the dynamic crosstalk observed between tight junctions and the cutaneous immune system. Finally we discuss the preliminary observations suggesting that tight junction function or protein expression may be relevant for the pathogenesis of a number of common cutaneous inflammatory and neoplastic conditions.
... 44 Accumulating evidence suggests that downregulation of claudin-1 expression in psoriasis results in hyperproliferation and impaired differentiation of keratinocytes. 43,45 Therefore, we evaluated the protein expression of claudin-1 and found that delphinidin treatment markedly increased the protein expression of claudin-1 in flaky skin mice compared with control mice (Fig. 3). In addition, expression of occludin is increased in psoriasis and other inflammatory diseases. ...
Article
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Background Psoriasis is a chronic inflammatory skin disease characterized by hyperproliferation and aberrant keratinocyte differentiation. We have shown that treatment of reconstituted human skin with delphinidin, an anthocyanidin, present in pigmented fruits and vegetables, increased the expression and processing of caspase-14, which is involved in cornification. Delphinidin also increases the expression of epidermal differentiation marker proteins.Objectives To determine whether topical application of delphinidin can modulate pathological markers of psoriasiform lesions in flaky skin mice and if this is associated with increased epidermal differentiation and a reduction in proliferation and inflammation.Methods Five-week-old female homozygous flaky skin mice (fsn/fsn) were treated topically with delphinidin (0·5 mg cm−2 and 1 mg cm−2 skin areas, respectively), five times a week, up to 14 weeks of age.ResultsTreatment of flaky skin mice with delphinidin resulted in a reduction in (i) pathological markers of psoriasiform lesions; (ii) infiltration of inflammatory cells; and (iii) mRNA and protein expression of inflammatory cytokines. Delphinidin treatment also increased the expression and processing of caspase-14, and expression of filaggrin, loricrin, keratin-1 and keratin-10. Furthermore, there was a decrease in the expression of markers for cell proliferation (proliferating cell nuclear antigen and keratin-14) and modulation of tight junction proteins (occludin and claudin-1). In addition, delphinidin treatment increased the expression of activator protein-1 transcription factor proteins (JunB, JunD, Fra1 and Fra2).Conclusions Delphinidin could be a promising agent for treatment of psoriasis and other hyperproliferative skin disorders.
... Deregulation of these junction proteins perturbs this barrier [43] and is characteristic of many inflammatory skin diseases [47,48] . Psoriatic skin, characterised by small scaly plaques, has an over-expression of occludin and ZO-1, while claudin-1 and 3 are down-regulated [49,50] . Keratinocyte cytoskeletal elements are also important for maintaining the epidermal barrier. ...
Article
Full-text available
Activated protein C (APC) is a physiological anticoagulant, derived from its precursor protein C (PC). Independent of its anticoagulation, APC possesses strong anti-inflammatory, anti-apoptotic and barrier protective properties which appear to be protective in a number of disorders including chronic wound healing. The epidermis is the outermost skin layer and provides the first line of defence against the external environment. Keratinocytes are the most predominant cells in the epidermis and play a critical role in maintaining epidermal barrier function. PC/APC and its receptor, endothelial protein C receptor (EPCR), once thought to be restricted to the endothelium, are abundantly expressed by skin epidermal keratinocytes. These cells respond to APC by upregulating proliferation, migration and matrix metalloproteinase-2 activity and inhibiting apoptosis/inflammation leading to a wound healing phenotype. APC also increases barrier function of keratinocyte monolayers by promoting the expression of tight junction proteins and re-distributing them to cell-cell contacts. These cytoprotective properties of APC are mediated through EPCR, protease-activated receptors, epidermal growth factor receptor or Tie2. Future preventive and therapeutic uses of APC in skin disorders associated with disruption of barrier function and inflammation look promising. This review will focus on APC's function in skin epidermis/keratinocytes and its therapeutical potential in skin inflammatory conditions.
... In the skin, tight junctions form a barrier for electrolyte and water loss. In mouse models, knockdown Cldn4 changed skin permeability for certain ions and molecules and human studies have shown altered CLDN3 expression in psoriatic plaques [Kirschner et al., 2013;Watson et al., 2007]. No studies have investigated cell turnover in chronic CLDN3 or CLDN4 haploinsufficiency. ...
Article
Previous examination in a small number of individuals with Williams syndrome (also referred to as Williams-Beuren syndrome) has shown subtly softer skin and reduced deposition of elastin, an elastic matrix protein important in tissue recoil. No quantitative information about skin elasticity in individuals with Williams syndrome is available; nor has there been a complete report of dermatologic findings in this population. To fill this knowledge gap, 94 patients with Williams syndrome aged 7-50 years were recruited as part of the skin and vascular elasticity (WS-SAVE) study. They underwent either a clinical dermatologic assessment by trained dermatologists (2010 WSA family meeting) or measurement of biomechanical properties of the skin with the DermaLab™ suction cup (2012 WSA family meeting). Clinical assessment confirmed that soft skin is common in this population (83%), as is premature graying of the hair (80% of those 20 years or older), while wrinkles (92%), and abnormal scarring (33%) were detected in larger than expected proportions. Biomechanical studies detected statistically significant differences in dP (the pressure required to lift the skin), dT (the time required to raise the skin through a prescribed gradient), VE (viscoelasticity), and E (Young's modulus) relative to matched controls. The RT (retraction time) also trended longer but was not significant. The biomechanical differences noted in these patients did not correlate with the presence of vascular defects also attributable to elastin insufficiency (vascular stiffness, hypertension, and arterial stenosis) suggesting the presence of tissue specific modifiers that modulate the impact of elastin insufficiency in each tissue. © 2014 Wiley Periodicals, Inc.
... Homozygous claudin-1 knockout mice die within 1 day after birth and exhibit severe transepidermal water loss and macromolecular diffusion through the epidermal TJ that permits the conclusion that claudin-1 is essential for barrier formation [30]. Other skin diseases that are associated with a downregulation of claudin-1 are atopic dermatitis and psoriasis [19,34,103]. Also, claudin-1 is expressed in cholangiocytes and hepatocytes and has been shown to cause neonatal sclerosing cholangitis associated with ichthyosis due to loss-of-function mutations in the claudin-1 gene [33,35]. ...
Article
Full-text available
Intestinal inflammatory diseases, four of which are discussed here, are associated with alterations of claudins. In ulcerative colitis, diarrhea and antigen entry into the mucosa occurs. Claudin-2 is upregulated but data on other claudins are still limited or vary (e.g., claudin-1 and -4). Apart from that, tight junction changes contribute to diarrhea via a leak flux mechanism, while protection against antigen entry disappears behind epithelial gross lesions (erosions) and apoptotic foci. Crohn’s disease is additionally characterized by a claudin-5 and claudin-8 reduction which plays an active role in antigen uptake already before gross lesions appear. In microscopic colitis (MC), upregulation of claudin-2 expression is weak and a reduction in claudin-4 may be only passively involved, while sodium malabsorption represents the main diarrheal mechanism. However, claudin-5 is removed from MC tight junctions which may be an active trigger for inflammation through antigen uptake along the so-called leaky gut concept. In celiac disease, primary barrier defects are discussed in the context of candidate genes as PARD3 which regulate cell polarity and tight junctions. The loss of claudin-5 allows small antigens to invade, while the reductions in others like claudin-3 are rather passive events. Taken together, the specific role of single tight junction proteins for the onset and perpetuation of inflammation and the recovery from these diseases is far from being fully understood and is clearly dependent on the stage of the disease, the background of the other tight junction components, the transport activity of the mucosa, and the presence of other barrier features like gross lesions, an orchestral interplay which is discussed in this article.
... Deregulation of these junction proteins perturbs this barrier [43] and is characteristic of many inflammatory skin diseases [47,48] . Psoriatic skin, characterised by small scaly plaques, has an over-expression of occludin and ZO-1, while claudin-1 and 3 are down-regulated [49,50] . Keratinocyte cytoskeletal elements are also important for maintaining the epidermal barrier. ...
... The claudin family provides the most important components of TJs, with more than 24 members that determine TJ resistance and permeability (Van Itallie and Anderson, 2006). We showed that hBD-3 increased the gene expression of claudins, which have been found in keratinocytes (Brandner et al., 2002;Watson et al., 2007;Brandner, 2009;De Benedetto et al., 2011), and demonstrated that keratinocytes also express claudin-20 and claudin-25. Among these claudins, only claudin-1, claudin-3, claudin-4, claudin-14, and claudin-23 were selectively enhanced at the protein level, and their localization at cell-cell borders was also increased, suggesting the importance of these claudins in the TJ barrier function. ...
Article
Human β-defensins (hBDs) are host defense peptides that not only exhibit microbicidal properties but also stimulate various cellular activities, including keratinocyte proliferation, migration and wound healing. hBDs are overexpressed in the skin in cases of psoriasis but are down-regulated in AD skin, although both diseases are associated with stratum corneum barrier defects. Because the tight junction (TJ) barrier is dysfunctional in both AD and psoriasis patients, we hypothesized that hBDs may regulate the TJ barrier function in keratinocytes. We observed that among the hBDs tested, only hBD-3 increased the expression of several claudins and their localization along the cell-cell borders. Additionally, hBD-3 elevated the transepithelial electrical resistance and reduced the paracellular permeability of keratinocyte layers, and this effect was reversed by the claudin inhibitor ochratoxin A, CCR6 antibody and CCR6 siRNA. Moreover, hBD-3 enhanced the activation of Rac1, atypical PKC, glycogen synthase kinase-3 and PI3K, which are required for the hBD-3-mediated regulation of the TJ barrier function, as evidenced by the effects of their respective inhibitors. Collectively, our findings provide evidence regarding the contribution of host defense peptides to the innate immunity of skin by regulating TJ barrier function, in addition to their antimicrobial and other immunomodulatory activities.Journal of Investigative Dermatology accepted article preview online, 14 March 2014; doi:10.1038/jid.2014.143.
... Interestingly, a down-regulation of claudin-1 and claudin-3 in psoriatic skin was reported by Watson et al. [121], who also conducted in vitro experiments with human keratinocytes and suggested that this effect was dependent on IL-1b present in the plaques. Likewise, IL-1b is also expressed during antigen and irritant challenges in atopic patients, as assessed in epidermis scrapings [49]. ...
Article
Studies published in recent years have highlighted the role of epidermal barrier defects in both atopic skin disease and the development of broader allergic manifestations. While genetic determinants of barrier function are important, it is clear that local acquired effects are also involved in disease pathogenesis. In this review, we aimed to summarize the known influences of cytokines abundantly expressed during atopic skin disease on components of epidermal barrier integrity and function.
... As a consequence, these mice die of dehydration in the neonatal period (97). Downregulation of claudin-1 is also found in other skin diseases associated with dry skin, including atopic dermatitis and psoriasis (63,388). Claudin-1 is also expressed in cholangiocytes and hepatocytes and acts as a barrier in the hepatic biliary ducts (115), presumably against bile salt leakage. ...
Article
Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions.
... Although the coordination of the permeability of the mucosa is more important in gut and gills where it has been studied in greater detail (Bagherie-Lachidan et al., 2008;Bui et al., 2010;Tipsmark et al., 2010), changes in expression of proteins from the paracellular junctional complex can lead to an opening of the skin mucosa for pathogens, toxins or ions and, as a result, also affects homeostasis. In mammals the down-regulation of certain claudins has been observed prior to the development of psoriatic lesions (Watson et al., 2007). ...
Article
Cyprinid herpesvirus-3 (CyHV-3) is recognised as a pathogen which causes mass mortality in populations of carp, Cyprinus carpio. One of the characteristic symptoms of the disease associated with CyHV-3 infection is the occurrence of skin lesions, sloughing off the epithelium and a lack of mucus. Furthermore, fish then seem to be more susceptible to secondary infections by bacterial, parasitic or fungal pathogens which may cause further mortality within the population. The observed pathological alterations lead to the assumption that the carp skin barrier is strongly challenged during CyHV-3 associated disease. Therefore we examined mRNA expression of genes encoding inflammatory mediators, type I interferons, and the following skin defence molecules: antimicrobial peptides, claudins, and mucin. In addition, we monitored changes in the bacterial flora of the skin during disease conditions. Our results show that CyHV-3 associated disease in the skin of common carp leads to a reduction in mRNA expression of genes encoding several important components of the mucosal barrier, in particular mucin 5B, beta defensin 1 and 2, and the tight junction proteins claudin 23 and 30. This caused changes in the bacterial flora and the development of secondary bacterial infection among some individual fish. To our knowledge this is the first report showing that under disease conditions associated with virus infection, the mucosal barrier of fish skin is disrupted resulting in a higher susceptibility to secondary infections. The reported clinical signs of CyHV-3 skin infection can now be explained by our results at the molecular level, although the mechanism of a probable virus induced immunomodulation has to be investigated further.
... In lichen planus, a broader expression of occludin and ZO-1 was described [97]. The same is true for psoriasis, where in addition a broader expression of Cldn-4 and a more or less pronounced downregulation of Cldn-1 were described [66,93,120]. Of note, the TJ barrier is still present in psoriatic plaques, at least in lesions with residual Cldn-1 [65]. ...
Article
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Inflammation of the skin is found after various external stimuli, e.g., UV radiation, allergen uptake, microbial challenge, or contact with irritants, as well as due to intrinsic, not always well-defined, stimuli, e.g., in autoimmune responses. Often, it is also triggered by a combination of both. The specific processes, which mean the kind of cytokines and immune cells involved and the extent of the reaction, depend not only on the trigger but also on the predisposition of the individual. Tight junctions (TJs) in the skin have been shown to form a barrier in the granular cell layer of the epidermis. Furthermore, TJ proteins were found in several additional epidermal layers. Besides barrier function, TJ proteins have been shown to be involved in proliferation, differentiation, cell-cell adhesion, and apoptosis in keratinocytes. In inflamed skin, TJ proteins are often affected. We summarize here the impact of skin inflammation on TJs, e.g., in various forms of dermatitis including atopic dermatitis, in skin infection, and in UV-irradiated skin, and discuss the role of TJs in these inflammatory processes.
... The data of Kirschner et al. ( 2010 ) also demonstrated that alteration of TJ proteins is an early event in psoriasis vulgaris (Kirschner et al. 2010 ) . It was interesting to fi nd that CLDN1, which is normally expressed in all layers of the epidermis, is down-regulated in psoriatic epidermis (Brandner et al. 2006 ;Watson et al. 2007 ) . In infections with Staphylococcus aureus a down-regulation of TJ proteins in the upper and also the lower layers of the epidermis was observed (Ohnemus et al. 2008 ) , suggesting again the barrier function of TJs for pathogen invasion (Brandner 2009 ) . ...
Chapter
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In this chapter we summarize recent and more established data with respect to tight junctions (TJ) and TJ associated changes in human tissues. TJs are considered as multifunctional complexes which are involved not only in regulation of paracellular diffusion, maintenance of cell polarity but also in cell signaling and gene expression regulation. There are several -sometimes contradictory- data about TJ proteins- and genes expression in the different organs of the human body. Clearly, more research is needed to understand the functions and consequences of alterations of different TJ proteins expression in normal as well as tumor tissues in order to clarify contradictory issues. In this chapter we intend to review the immense amount of data published so far in the field of TJs in different organs. For better understanding, we grouped the organs according to their ectodermal, endodermal or mesodermal origin. CLDNs have been identified as the major constituents of TJ strands. All current evidence supports a central role for CLDNs in the functions of the TJs. However, the exact stoichiometry remains unclear and little is known about the molecular mechanisms taking place during assembly and strand formation in normal as well as in tumor tissues. Accordingly, the majority of data presented in this chapter consider the different CLDNs expression in normal human tissues, in premalignant or malignant lesions. Nevertheless, we made an effort to present data about other TJ components in different organs when available.
... 2) Further loss of claudin is a consequence of various stimuli like bacterial infections leading to impairment in the TJ barrier functions. ( Brandner, 2002 ;Watson et al., 2007 ;(Kirschner et al., 2009) Atopic Dermatitis Claudin−1 ,−2 ,−3 , Claudin−1 (lesional area) ...
... Lipid peroxidation and protein oxidation may result in excessive reactive oxygen species (ROS) production in the intestine. ROS can affect the epithelial cells and eliminate the integrity of the intestinal tissue.ROS negatively can affect epithelial and integrity of intestine.The parameters of the antioxidant system in the intestinal tract are important factors in controlling intestinal health, because oxidative damage causes disturbances in the tight junction proteins through the reduction of expression ZO-1 and Claudine genes in intestine [22]. Therefore, the analysis of antioxidant enzymes such as SOD, CAT, GPx and GR in fish, may use as indicators of fish health. ...
Article
Intestine in fish is a complex multifunctional organ, not only plays roles in digestion and absorption of nutrient, but also has critical role in immunity. The present study evaluated the effects of different levels of dietary sodium butyrate [Butirex® C4 (Butirex)] on intestinal immune-,antioxidant-and tight junction-related gene expression injuvenile rainbow trout(Oncorhynchusmykiss). 240 healthy rainbow trout were dispensed in 12 fiberglass tanks appointed to four treatments [0 (control), 1.5 (B1.5), 2.5 (B2.5) and 5 (B5)g Butirex per kg diet]. After a 45-day feeding trial, the fish fed with the Butirex-supplemented diets showed higher intestinal lysozyme (LYZ), complement(ACH50) and bactericidal activities; the elevations in ACH50 and bactericidal activities depended on Butirex levels (P < 0.05). The Butirex-supplemented groups, particularly the B2.5 group, had significantly higher LYZ gene expression compared to the control group (P < 0.05). Butirex at 2.5 and 5 g/kg levels led to significantly higher IL-1β gene expression. B2.5 and B5 had significantly lower and higher TNF-α gene expression compared to the control group (P < 0.05). The B2.5 group had significantly higher TGF-B, and significantly lower IL-8 compared to the control group (P < 0.05). The B1.5 and B2.5 group had significantly higher IL-10 gene expression compared to the control group (P < 0.05). The B2.5 and B5 groups had significantly higher SOD gene expression compared to the other groups; the highest expression was related to the B2.5 group (P < 0.05). Dietary Butirex supplementation significantly up-regulated CAT and GPx genes expression compared to the control group; the highest expression as related to the B2.5 and B5 groups (P < 0.05). The B2.5 group had significantly lower CLD12 gene expression compared to the control group (P < 0.05). The B2.5 and B5 groups had significantly higher CLD3, OCLD and ZO-1 gene expression compared to the control. The highest CLD3, ZO-1 gene expressions was related to the B2.5, and B5 groups respectively (P < 0.05). After challenge with Streptococcus iniae, B2.5 and B5 had significantly higher survival compared to the control group (55.6 ± 7.70 and 68.9 ± 10.2 vs. 33.3 ± 6.67). In conclusion, Butirex is efficient immune stimulant and health booster in rainbow trout, which augments the fish resistance to disease. Modulation of immune components, cytokines, antioxidant system and intestinal integrity might involve in improving disease resistance in Butirex-treated fish. Although most of the examined genes were modulated by 2.5 g/kg Butirex under normal conditions, 5 g/kg level is recommended under pathogenic state to mitigate mortality.
... These tight junctions are considered to be vital elements of the epidermal barriers. The expression and localization of tight junction proteins are altered in diseased conditions leading to a damaged skin barrier, such as in case of psoriasis (Kirschner et al. 2009;Watson et al. 2007). ...
Chapter
The field of nanomedicine has emerged as a promising platform for the development of novel drug delivery systems that delivers the therapeutic molecules in a sustained and controlled manner at a targeted site. Nanotechnology has progressed in the pharmaceutical field owing to its capability to resolve solubility, stability, absorption, permeation, and toxicity related issues. For the fabrication of drug delivery carriers, availability, safety, and toxicity issues must be considered seriously. The polysaccharides play a very significant role in overcoming these hurdles. Thus, the remarkable features of polysaccharides offer enormous potential for their applicability in the designing of drug delivery systems. Recently, polysaccharide-based nanostructural systems have emerged as attractive vehicles for delivering the drug into the skin (local action) and through the skin (systemic action). This chapter explores the mechanism of the fabrication of polysaccharide-based nanocarriers and their application as potential drug delivery vehicles for local and systemic action.
... claudins 1, 7, and 12, Junctional Adhesion Molecule (JAM)-A, and MUPP1), or to the spinous keratinocytes (e.g., ZO-1, ZO-2, claudins 4, 6, 18). [26][27][28]35,[57][58][59][60][61][62] Similar to observations in cultured keratinocytes, disruption of cadherin-containing adherens junctions in vivo results in impairment in tight junction formation. Targeted inactivation of Cdh1 in mice, which encodes E-cadherin, results in extensive transepidermal water loss and loss of functional tight junctions in the stratum granulosum. ...
Article
The skin of mammals and other terrestrial vertebrates protects the organism against the external environment, preventing heat, water and electrolyte loss, as well as entry of chemicals and pathogens. Impairments in the epidermal permeability barrier function are associated with the genesis and/or progression of a variety of pathological conditions, including genetic inflammatory diseases, microbial and viral infections, and photodamage induced by UV radiation. In mammals, the outside-in epidermal permeability barrier is provided by the joint action of the outermost cornified layer, together with assembled tight junctions in granular keratinocytes found in the layers underneath. Tight junctions serve as both outside-in and inside-out barriers, and impede paracellular movements of ions, water, macromolecules and microorganisms. At the molecular level, tight junctions consist of integral membrane proteins that form an extracellular seal between adjacent cells, and associate with cytoplasmic scaffold proteins that serve as links with the actin cytoskeleton. In this review, we address the roles that scaffold proteins play specifically in the establishment and maintenance of the epidermal permeability barrier, and how various pathologies alter or impair their functions.
... Watson et al. showed that IL-1β can downregulate the expression of tight junction proteins in the skin. 3 IL-36, a member of the IL-1 family of cytokines, might also influence the expression of these proteins. In this study, IL-36γ was selected in the lesional skin of psoriasis patients, as it is the only IL-36 cytokine constitutively expressed in the skin and may become a potential biomarker of psoriasis. ...
... Mercado et al. [49] found that glucocorticoid receptor can reduce the expression of the IL-1β gene in mouse skin. A study in humans showed that reduced IL-1β concentrations can increase epidermal keratinocyte claudin-3 protein [50]. However, studies on Mozambique tilapia (Oreochromis mossambicus) have shown that the gene expression levels of the glucocorticoid receptor in the PI are lower than those in the MI and DI [51]. ...
Article
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Ochratoxin A (OTA) contamination widely occurs in various feed ingredients and food crops, potentially posing a serious health threat to animals. In this research, 1260 juvenile grass carp were separately fed with seven distinct experimental diets (0, 406, 795, 1209, 1612, 2003 and 2406 µg of OTA/kg of diet) for 60 consecutive days to evaluate OTA’s toxic effect on the intestinal apical junctional complex (including the tight junction (TJ) and the adherents junction (AJ)) and the underlying action mechanisms. Our experiment firstly confirmed that OTA caused fish growth retardation and disrupted the intestinal structural integrity. The detailed results show that OTA (1) depressed the feed efficiency, percentage weight gain and specific growth rate; (2) accumulated in the intestine; (3) caused oxidative damage and increased intestinal permeability; and (4) induced the RhoA/ROCK signaling pathway, destroying intestinal apical junctional complexes. Notably, OTA intervention did not result in changes in the gene expression of claudin-3c (in the proximal intestine (PI)), claudin-b and ZO-2b (in the mid intestine (MI) and distal intestine (DI)) in the fish intestine.
... Linkage analysis identifies nine psoriatic susceptibility loci, some of which are located in the region encoding claudins. Patients with psoriasis have been shown to lack claudin-1 expression based on the detection of skin lesions [68]. ...
Article
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Tight junction (TJ) is a “zippering up” junction structure located at the uppermost portion of adjacent epithelial/endothelial cells in organs and tissues. TJs maintain the relative stability of intracellular substances and functions by closing or opening intercellular pathways, coordinating the entry and exit of molecules of different sizes and charges, and regulating the permeability of paracellular barrier. TJs also prevent microbial invasion, maintain epithelial/endothelial cell polarity, and regulate cell proliferation. TJs are widely present in the skin and mucosal epithelial barriers, intestinal epithelial barrier, glomerular filtration barrier, bladder epithelial barrier, blood-brain barrier, brain-blood tumor barrier, and blood-testis barrier. TJ dysfunction in different organs can lead to a variety of diseases. In addition to signal pathways, transcription factors, DNA methylation, histone modification, TJ proteins can also be regulated by a variety of non-coding RNAs, such as micro-RNAs, long-noncoding RNAs, and circular RNAs, directly or indirectly. This review summarizes the structure of TJs and introduces the functions and regulatory mechanisms of TJs in different organs and tissues. The roles and mechanisms of non-coding RNAs in the regulation of TJs are also highlighted in this review.
... Finally we investigated the role of the TJ protein Cldn-1 in HF keratinocytes. We were especially interested in Cldn-1 because (1) it is the most widespread TJ protein in HFs, (2) it shows a dynamic change during hair cycle, (3) it is known to be involved in proliferation [19][20][21] and apoptosis 22 , which are important for hair growth and regression, (4) Cldn-1 knock-out in mouse and human results in an aberrant hair phenotype 9,23 , and (5) Cldn-1 is altered in the epidermis of skin diseases, such as atopic dermatitis (AD) 20,24 and psoriasis 25,26 . We show here that Cldn-1 is also down-regulated in HFs of lesional AD skin and that down-regulation of Cldn-1 in hair keratinocytes results in impaired barrier function, decreased proliferation and increased apoptosis. ...
Article
Full-text available
Barrier function of hair follicles (HFs) is of great interest because they might be an entry port for allergens/pathogens, but could on the other hand be used for drug delivery or vaccination. Therefore we investigated tight junction (TJ) barrier function in human HFs. We show that there is a TJ barrier in the outermost living layer bordering to the environment from the infundibulum to the lower central part and between Henle's and Huxles layer of anagen HFs. In club hair typical for catagen and telogen HFs a TJ barrier is found surrounding the club. This demonstrates that there is a continuous TJ barrier along interfollicular epidermis and HFs in different phases of HF cycle. However, interestingly, in cell culture experiments we can show that barrier is less tight in HF keratinocytes compared to interfollicular keratinocytes. Knock-down of the TJ protein claudin-1, which we demonstrate here to be less expressed in HFs of lesional atopic dermatitis skin, results in impaired barrier function, decreased proliferation and increased apoptosis of hair keratinocytes. This is in line with a hair growth phenotype in claudin-1 deficient patients (NISCH syndrome) and corresponding knock-out mice and indicates an important role of claudin-1 in HF barrier function and growth.
... Tight junction proteins are also essential not only in regulation of cell permeability but also in enrolling different signaling proteins involving in cell proliferation and differentiation regulations 57 . The observed tight junction pathway significantly enriched in miR-378a-deficient keratinocytes was consistent with the previous studies reporting that down-regulation of tight junction proteins (i.e., claudin-1, -3, -7, and zonula occludens 1) were correlated with an increase of interleukin-36γ (IL-36γ) and a decrease of vitamin D receptor (VDR) expression in the epidermis of psoriatic lesions [58][59][60][61][62] . From this observation, it suggests that miR-378a may promote the dysregulation of tight junction proteins, exacerbating the disease pathogenesis. ...
Article
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Psoriasis is a chronic autoimmune skin disease driven by dysregulations at the cellular, genomic and genetic levels. MicroRNAs are key mediators of gene expression regulation. However, how microRNAs control the pathogenesis of psoriasis is still unclear. Here, we reported a significant up-regulation of miR-378a-3p (miR-378a) in skin biopsies from active psoriatic lesions while it was down-regulated after treatment with methotrexate or narrow-band ultraviolet B phototherapy. Using the keratinocyte in vitro model, we showed that miR-378a disturbed the cell cycle progression, causing cell cycle arrest at G1 phase. Transcriptomic analysis of keratinocytes with miR-378a overexpression and depletion revealed several important biological mechanisms related to inflammation and tight junction. Target mRNA transcript assessed by luciferase assay identified bone morphogenetic protein 2 as a novel target gene of miR-378a. These findings offer a mechanistic model where miR-378a contributes to the pathogenesis of psoriasis.
... In addition, the mixture of IL-4, IL-13, and IL-31 induced the decreased immunointensity of CLDN1 expression in skin equivalents [13]. Previous studies showed that IL-1ß resulted in a downregulation of CLDN1 expression [14,15]. It has been reported that CLDN1 expression decreased in a dose-dependent manner on the epidermis of skin equivalents treated with IL-17 [11]. ...
Article
Background: Tight junctions (TJs) have important roles in skin barrier function. The TJ protein claudin-1 (CLDN1) is decreased in atopic dermatitis (AD). However, little is known about the mechanism of CLDN1 down-expression. Objective: To elucidate the effect of IL-33 on CLDN1 expression in keratinocytes. Methods: Normal human epidermal keratinocytes (NHEKs) and human skin equivalent models (HSEMs) were cultured in vitro in the presence of IL-33. Production of CLDN1, signal transducer and activator of transcription 3 (STAT3) and Mitogen-activated protein kinases (MAPK) expression were measured by real-time PCR, western blot and immunofluorescence assay. MAPK inhibitors and small interfering RNA were used to confirm the signal pathway of STAT3 and CLDN1. Barrier function was measured by transepithelial electric resistance (TEER) and FITC-dextran flux assays. Electrophoretic Mobility Shift Assay was used to detect STAT3 transcriptional activity. Results: Levels of CLDN1 expression were reduced in the epidermis of AD-model mice overexpressing IL-33. IL-33 down-regulated the expression of CLDN1 mRNA and protein in NHEKs and HSEMs. IL-33 attenuated transepithelial electric resistance and induced FITC-dextran flux in NHEKs. The IL-33 suppressed CLDN1 expression was regulated by an extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription 3 (STAT3). STAT3 suppressed CLDN1 expression by direct binding to the promoters. Conclusion: IL-33 may down-regulate CLDN1 expression through the ERK/STAT3 pathway in keratinocytes.
... Many inflammatory skin diseases are connected to altered distribution patterns and expression levels of TJ proteins at the cell-cell border of epidermal layers [38]. Particularly, down-regulation or knockout of integral membrane proteins (i.e., occludin, JAM, and claudin 1 and other isoforms) and TJ plaque protein ZO-1 belong to the clinical pictures of psoriasis vulgaris [14,72,73], atopic dermatitis [12,74], bacterial impetigo contagiosa [75], ichthyosis vulgaris [9,76], lichen planus [9], Hailey-Hailey disease [77], or systemic sclerosis [78]. These diseases might be targeted using plasma technology [3], generating exogenous ROS that penetrate into tissue [79]. ...
Article
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Cold plasma technology is an emerging tool facilitating the spatially controlled delivery of a multitude of re-active species (ROS) to the skin. While the therapeutic efficacy of plasma treatment has been observed in several types of diseases, the fundamental consequences of plasma-derived ROS on skin physiology remain unknown. We aimed to bridge this gap since the epidermal skin barrier and perfusion plays a vital role in health and disease by maintaining homeostasis and protecting from environmental damage. The intact skin of SKH1 mice was plasma-treated in vivo. Gene and protein expression was analyzed utilizing transcriptomics, qPCR, and Western blot. Immunofluorescence aided the analysis of percutaneous skin penetration of curcumin. Tissue oxygenation, perfusion, hemoglobin, and water index was investigated using hyperspectral imaging. Reversed-phase liquid-chromatography/mass spectrometry was performed for the identification of changes in the lipid composition and oxidation. Transcriptomic analysis of plasma-treated skin revealed modulation of genes involved in regulating the junctional network (tight, adherence, and gap junctions), which was confirmed using qPCR, Western blot, and immunofluorescence imaging. Plasma treatment increased the disaggregation of cells in the stratum corneum (SC) concomitant with increased tissue oxygenation, gap junctional intercellular communication, and penetration of the model drug curcumin into the SC preceded by altered oxidation of skin lipids and their composition in vivo. In summary, plasma-derived ROS modify the junctional network, which promoted tissue oxygenation, oxidation of SC-lipids, and restricted penetration of the model drug curcumin, implicating that plasma may provide a novel and sensitive tool of skin barrier regulation.
Article
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Biological membranes define the boundaries of cells and compartmentalize the chemical and physical processes required for life. Many biological processes are carried out by proteins embedded in or associated with such membranes. Determination of membrane protein (MP) structures at atomic or near-atomic resolution plays a vital role in elucidating their structural and functional impact in biology. This endeavor has determined 1,198 unique MP structures as of early 2021. The value of these structures is expanded greatly by deposition of their three-dimensional (3D) coordinates into the Protein Data Bank (PDB) after the first atomic MP structure was elucidated in 1985. Since then, free access to MP structures facilitates broader and deeper understanding of MPs, which provides crucial new insights into their biological functions. Here we highlight the structural and functional biology of representative MPs and landmarks in the evolution of new technologies, with insights into key developments influenced by the PDB in magnifying their impact.
Article
OVERVIEW The skin acts as the interface between the organism and the outside environment, functioning as a physical and selective barrier against chemical and biological invasion (outside-to-inside), as well as retaining body solutes and maintaining thermoregulation (inside-to-outside). This complex role is achieved through an epidermal differentiation program that gives rise to a tightly regulated and selective epidermal permeability barrier (EPB). Dysfunction of this barrier during development, or at any time during the lifespan, leads to death under severe circumstances or to a propensity for chronic skin conditions or diseases. In spite of its important role, the molecular mechanisms behind the formation and function of the EPB are still poorly understood. The recent discovery of the Claudin (Cldn) family of tight junction (TJ) proteins and their structural-functional characterization has uncovered their essential role in the EPB and other tissue-organ barriers in the body. This chapter summarizes our emerging understanding of Cldns and their role in TJs and in the EPB in normal development and certain skin diseases.
Article
Ethnopharmacological relevance: Indigo naturalis is used in traditional Chinese medicine to treat various dermatoses. Our previous clinical studies showed that indigo naturalis is an effective treatment for psoriasis. Herein, the capabilities of indigo naturalis extract and its derivatives to increase claudin-1 expression and tight junction (TJ) function in human keratinocytes and psoriatic lesions were further studied. Materials and methods: Claudin-1 expression in psoriatic plaques with or without indigo naturalis treatment was analyzed by immunohistochemical methods. In primary human keratinocytes, the expression of claudin-1 was analyzed by fluorescent immunostaining, a real-time RT-PCR, and Western blot analysis. The effect of indigo naturalis on TJs was evaluated by measuring the transepithelial electrical resistance (TEER) and paracellular tracer flux. Results: The indigo naturalis extract upregulated mRNA and protein expressions of claudin-1 and function of TJs in primary human keratinocytes in concentration-dependent manners. Its main components, indirubin, indigo, and tryptanthrin, exerted synergistic effects on upregulating TJ functions in primary human keratinocytes. In addition, indigo naturalis increased the activity of protein kinase C (PKC), and a known potent PKC inhibitor, Ro318220, attenuated the indigo naturalis-induced claudin-1 expression. Significantly, restoration of claudin-1 was observed in healed psoriatic lesions after indigo naturalis treatment. Conclusions: Indigo naturalis upregulates claudin-1 expression and restores TJ function in keratinocytes. Our data also suggest that indirubin, indigo, and tryptanthrin have a synergistic effect on TJ function.
Tight junction proteins have been shown to be involved in barrier function of the skin. In the stratum granulosum they form typical barrier-forming TJ structures, in deeper layers they might form other structures and fulfil additional functions. This review summarizes our knowledge about TJ and TJ proteins in mammalian skin and their involvement in skin diseases such as ichthyosis, psoriasis, and bacterial infections. Their putative suitability as new targets for improving drug delivery is discussed.
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The skin is an indispensable barrier which protects the body from the uncontrolled loss of water and solutes as well as from chemical and physical assaults and the invasion of pathogens. In recent years several studies have suggested an important role of intercellular junctions for the barrier function of the epidermis. In this review we summarize our knowledge of the impact of adherens junctions, (corneo)-desmosomes and tight junctions on barrier function of the skin.
Article
A variety of chemical compounds are currently being discussed as novel drug delivery strategies. One promising strategy is to selectively open the paracellular pathway of epithelia for the passage of macromolecules. A prerequisite for this effect is a rapid and reversible action of these compounds, to allow a marked translocation of a drug, but also to avoid unwanted adverse effects, such as the translocation of noxious agents. Bioactive molecules that elevate paracellular permeability include Ca(2+) chelators, bacterial toxins, and other compounds, some of which perturb the structural basis of epithelial barrier function--the tight junction. Within the tight junction, organ- and tissue-specific barrier properties are determined mainly by claudins. The majority of members of the claudin protein family seal the paracellular pathway. This paper focuses on recent approaches concerning absorption-enhancing effects, with regard to selectivity and mechanism.
Article
Atopic dermatitis (AD) is a common skin inflammatory disease characterized by the production of thymic stromal lymphopoietin (TSLP) and a marked TH 2 polarization. Recent studies suggest that IL-1β contributes to the development of AD skin inflammation. Here, we have investigated the impact of IL-1β signalling on the epidermal homeostasis of both healthy subjects and AD patient [with functional filaggrin (FLG) alleles] with particular attention to TSLP production and keratinocyte differentiation. In healthy reconstructed human epidermis (RHE), IL-1β promoted: (i) a robust secretion of TSLP in an NFkB-dependant manner and (ii) a significant decrease in the expression of filaggrin and other proteins of the epidermal differentiation complex. These effects were prevented by treatment of RHE with the anti-IL-1β mAb canakinumab and by the IL-1 receptor antagonist anakinra. Interestingly, RHE generated from AD donors behaved like that of healthy individuals and showed comparable responses to IL-1β signals. Collectively, our results suggest that IL-1β may be an early key mediator for the acquisition of an AD phenotype through induction of TSLP and alteration of the epidermal homeostasis.
Article
Background: Cell junctions are crucial for the formation and maintenance of the paracellular barrier and for cell polarity in simple epithelia and endothelia. Altered localization and formation of tissue junction proteins in the epidermis have been described in plaque-type psoriasis. Vitamin D receptor (VDR) is a nuclear hormone involved in anti-proliferative and pro-differentiation pathways in keratinocytes. However, still to date, vitamin D/VDR signalling involved in tissue barrier related to psoriasis remains largely unknown. Objective: To study the expression of VDR and tight junctions (TJ) proteins (claudin 1, ZO-1 and occludin) in psoriatic skin, and to correlate the expression of VDR with that of the junctional proteins claudin- 1, occludin and ZO- 1. Methods: A total of 20 psoriatic tissue samples were included in the analysis. Immunohistochemical studies for VDR, claudin-1, occludin and ZO-1 were performed. Results: We observed a reduction of VDR, claudin-1 and ZO-1 expression in psoriatic skin if compared to normal skin, and the statistical analysis showed a significant correlation between a downgrading of VDR expression and that of claudin-1 (P < 0.005) and ZO-1(P < 0.005). Conclusions: Our results suggest a new role of VDR in the maintenance of the homeostasis skin barrier. Although the exiguity of our cohort, VDR status appears to be associated with the expression level and functions of TJ proteins, suggesting multiple and different cellular functions of the VDR.
Article
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Atopic dermatitis is a common pruritic inflammatory skin disease in humans and dogs. Cell junction and cornified envelope are groups of proteins that are crucial for the formation and stability of the skin barrier. The purpose of this study was to investigate gene expression in cell junction and cornified envelope groups in canine atopic dermatitis (CAD) in small dog breeds. Skin biopsy was performed from 10 lesional CAD, 9 non-lesional CAD cases and 11 normal dogs and subjected to quantitative reverse transcription-polymerase chain reaction. Several cell junction genes were evaluated, including claudin-1, occludin, zonula occludens-1 and -2, zonula occludens-1-associated nucleic acid binding protein, cingulin, gap junction beta 2 and e-cadherin together with transglutaminase 1, a cross-linker of the cornified envelope. An upregulation of gap junction beta 2 and transglutaminase 1 was significantly observed in the lesional skin. In conclusion, the present study demonstrates the expression of gap junction beta 2 and transglutaminase 1 in CAD. This is the first report on the association of cell junction and transglutaminase 1 genes with CAD.
Article
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Bicellular tight junctions (TJs) are intercellular junctions comprised of a variety of transmembrane proteins including occludin, claudins, and junctional adhesion molecules (JAMs) as well as intracellular scaffold proteins such as zonula occludens (ZOs). TJs are functional, intercellular structures that form a barrier between adjacent cells, which constantly seals and unseals to control the paracellular passage of molecules. They are primarily present in the epithelial and endothelial cells of all tissues and organs. In addition to their well-recognized roles in maintaining cell polarity and barrier functions, TJs are important regulators of signal transduction, which modulates cell proliferation, migration, and differentiation, as well as some components of the immune response and homeostasis. A vast breadth of research data is available on TJs, but little has been done to decipher their specific roles in wound healing, despite their primary distribution in epithelial and endothelial cells, which are essential contributors to the wound healing process. Some data exists to indicate that a better understanding of the functions and significance of TJs in healing wounds may prove crucial for future improvements in wound healing research and therapy. Specifically, recent studies demonstrate that occludin and claudin-1, which are two TJ component proteins, are present in migrating epithelial cells at the wound edge but are absent in chronic wounds. This indicates that functional TJs may be critical for effective wound healing. A tremendous amount of work is needed to investigate their roles in barrier function, re-epithelialization, angiogenesis, scar formation, and in the interactions between epithelial cells, endothelial cells, and immune cells both in the acute wound healing process and in non-healing wounds. A more thorough understanding of TJs in wound healing may shed new light on potential research targets and reveal novel strategies to enhance tissue regeneration and improve wound repair.
Chapter
The maintenance of optimum water content in the skin and especially in the epidermis is provided by many orchestrated mechanisms. Water uptake into the dermis/epidermis, paracellular and transcellular water transport through the epidermis and water retention as well as controlled water loss in the stratum corneum have to be coordinated. Unbalance of these mechanisms results in dry skin. Following its paracellular route, water has to pass tight junctions before it can get into contact with the stratum corneum. For the transcellular route water channels, formed by so-called aquaporins, are of importance. Here, I will summarize our current knowledge of the involvement of aquaporin-formed pores and tight junctions in epidermal water homeostasis - as well as in other functions - and their putative roles in skin dryness. © 2012 Springer-Verlag GmbH Berlin Heidelberg. All rights are reserved.
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The skin barrier is broadly composed of two elements-a physical barrier mostly localised in the epidermis, and an immune barrier localised in both the dermis and epidermis. These two systems interact cooperatively to maintain skin homeostasis and overall human health. However, if dysregulated, several skin diseases may arise. Psoriasis is one of the most prevalent skin diseases associated with disrupted barrier function. It is characterised by the formation of psoriatic lesions, the aberrant differentiation and proliferation of keratinocytes, and excessive inflammation. In this review, we summarize recent discoveries in disease pathogenesis, including the contribution of keratinocytes, immune cells, genetic and environmental factors, and how they advance current and future treatments.
Article
The purpose of this study was to elucidate the effects of bovine lactoferrin on keratinocyte differentiation and barrier function. Addition of bovine lactoferrin to differentiating HaCaT human keratinocytes led to increased transepithelial electrical resistance (TER), a marker of epithelial barrier function. This elevation was followed by upregulation of two differentiation markers, involucrin and filaggrin. The expression level of sterol regulatory element-binding protein-1 was also enhanced by bovine lactoferrin. The lactoferrin-induced upregulation of involucrin and filaggrin expression were confirmed in normal human epidermal keratinocytes (NHEK). Treatment with SB203580, a p38 mitogen-activated protein kinase (MAPK) α inhibitor, impaired the upregulation of involucrin and filaggrin expression in response to lactoferrin. The elevation of p38 MAPK phosphorylation was further enhanced by lactoferrin in the initial stage of differentiation of HaCaT keratinocytes. The findings suggest that bovine lactoferrin promotes epithelial differentiation by a p38-MAPK-dependent mechanism.
Article
Bacterial infections (e.g., with Staphylococcus aureus) are serious problems in skin with a compromised barrier, such as in patients with atopic dermatitis. Previously, it was shown that tight junction (TJ) proteins are influenced by staphylococcal infection, and TJ function is impaired after infection of the keratinocyte cell line HaCaT. However, functional studies in cells or models more similar to human skin are missing. Therefore, we investigated bacterial colonialization and infection with live S. aureus in primary human keratinocytes and reconstructed human epidermis (RHE). We show that short-term inoculation results in increased TJ barrier function—which could not be seen in HaCaT cells—hinting at an early protective effect. This is accompanied by occludin phosphorylation and sustained localization of occludin and claudin-4 at cell membranes. Long-term incubation resulted in decreased presence of claudin-1 and claudin-4 at cell membranes and decreased TJ barrier function. The agr regulon of S. aureus plays a role in the increasing but not in the decreasing effect. Proinflammatory cytokines, which are produced as a result of S. aureus inoculation, influence both phases. In summary, we show here that S. aureus can have short-term promoting effects on the TJ barrier, while in the long term it results in disturbance of TJs.
Article
Tumor Necrosis Factor-α (TNF-α) plays a pivotal role in psoriasis, an immuno-mediated and genetic skin disease. Anti-TNF-α inhibitors, such as etanercept, are widely used in clinical practice. By immunofluorescence, we investigated the expression of junctional transmembrane proteins in desmosomes (desmocollin-1, Dsc1; desmoglein-1, Dsg1), adherens junctions (E-cadherin), tight junctions (occludin), biomarkers of keratinocyte differentiation (keratin-10, K10; keratin-14, K14; keratin-16, K16; involucrin), epithelial proliferation and apoptosis in psoriatic skin before/after etanercept treatment (n = 5) and in control skin samples (n = 5). Occludin, K14, K16 and involucrin expressions were altered in psoriatic epidermis, while Dsc1, Dsg1, E-cadherin and K10 localisations were comparable to controls. Etanercept promoted the restoration of the physiological condition as suggested by a more differentiated keratinocyte phenotype and a reduced epidermal proliferation rate.
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The fine structure of freeze cleaved tight junctions was examined in high resolution replicas of rat small intestine. By carefully comparing the changes in the surface topography of the cleavage faces of specimens, which, before freezing, were either prefixed with glutaraldehyde and then infiltrated with glycerol, infiltrated with glycerol alone, or infiltrated with glycerol and then fixed with glutaraldehyde, a more precise definition of the tight junction architecture at the supramolecular level has become possible. The results of this analysis suggest that the bilayer membranes contributing to a tight junction are held together along interconnected lines of attachment that are arranged in the form of a continuous band like meshwork. Each line consists of 2 parallel rows, one in each membrane, of closely spaced adhesion particles. The sensitivity of these particles to glutaraldehyde and their cleaving behavior under different experimental conditions indicate that they represent globular proteins which bridge the width of the adjoining membranes and are linked together in the plane of the intercellular space. Thus, the morphology of a tight junction seal resembles a modified zipper with the locking units making head to head contact. Similarly, the presence of many open ended sealing elements between crypt cells has been interpreted as suggesting that the formation of tight junction seals could resemble a 'zippering up' process. At the juncture of 3 cells the tight junction meshwork is both modified and extended basally to produce a characteristic pattern. In the central area of such a triple junction, 3 parallel and very closely spaced vertical seals have been resolved, each joining a pair of adjacent plasma membranes. Small, regularly spaced, cross bridging elements interlink pairs of central seals within the plane of each membrane. At different levels each individual central seal may further give rise to horizontal sealing elements which connect in a ladder like fashion either to the major network or to vertical elements positioned at greater distances from the central axis. Evidence is presented suggesting that fragments of tight junctions can be internalized and broken down in lysosome like vesicles.
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Intercellular junctions are specialized regions of contact between the apposed plasma membranes of adjacent cells, and recent evidence suggests that they are essential for the development of multicellular organisms. They provide the structural means for groups of cells to interact in certain defined ways, and thereby enable them to create structures of higher order. This chapter reviews the morphological information on intercellular junctions derived from thin-sectioning, negative staining and freeze-cleave techniques, as well as from x-ray diffraction and biochemical investigations, and correlates the structural parameters with known or proposed physiological functions. The membrane structure of intercellular junctions is described. Membrane proteins can be divided into two groups: peripheral and integral. Peripheral membrane proteins are believed to be associated with the membrane surface, based on the observation that they are held to the membrane by rather weak noncovalent interactions, and are not strongly associated with membrane lipids. Only mild treatments, such as an increase in ionic strength of the medium or the addition of a chelating agent, are needed to dissociate them molecularly intact from the membrane. Furthermore, in the dissociated state they are relatively soluble in neutral aqueous buffers. In contrast, integral membrane proteins appear much more strongly bound to the lipid matrix, since they can be dissociated from the latter only by drastic treatments with chemicals such as detergents, protein denaturants, and organic solvents. The diversity in structure and function of intercellular junctions offers an exciting field for future research in which morphologists, physiologists, and biochemists should be able to make significant contributions to the knowledge of how individual cells interact to form structures of higher order.
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The tight junction (TJ) is not randomly located on the cell membrane, but occupies a precise position at the outermost edge of the intercellular space and, therefore, is itself considered a polarized structure. This article reviews the most common experimental approaches for studying this relationship. We then discuss three main topics. (a) The mechanisms of polarization that operate regardless of the presence of TJs: We explore a variety of polarization mechanisms that operate at stages of the cell cycle in which TJs may be already established. (b) TJs and polarity as partners in highly dynamic processes: Polarity and TJs are steady state situations that may be drastically changed by a variety of signaling events. (c) Polarized distribution of membrane molecules that depend on TJs: This refers to molecules (mainly lipids) whose polarized distribution, although not the direct result of TJs, depends on these structures to maintain such distribution.
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Changes in the levels of IL-1 (IL-1α, IL-1β, and its receptor antagonist, IL-1RA) occur upon keratinocyte differentiation in vitro and are associated in vivo with abnormal differentiated and hyperproliferative states of psoriatic keratinocytes. A flow cytometric procedure, capable of detecting changes in the intracellular levels of IL-1, was used to determine whether intracellular IL-1/IL-1RA levels in psoriatic and normal keratinocytes alter during in vivo differentiation and the cell cycle. Increases in the IL-1RA levels and IL-1α levels were observed as both normal and psoriatic keratinocytes differentiated from basal stem cells (β1 integrin+, small size) into transient amplifying cells (TAC; β1 integrin+, large size). Upon further differentiation (β1 integrin-, large size) both IL-1RA and IL-1α levels dropped. However, while psoriatic IL-1β levels increased as cells differentiated into TACs, little change occurred in the IL-1β levels of normal keratinocytes during differentiation. Changes in IL-1/IL-1RA levels were also detected as keratinocytes progressed through the cell cycle. Within the basal stem cell population of both normal and psoriatic keratinocytes, the IL-1α and IL-1RA levels increased between G0/G1 and S but not between S and G2/M. However, psoriatic basal keratinocyte IL-1β levels differed from those of normal keratinocytes by showing no increase between S and G2/M. The IL-1/IL-1RA levels of normal TAC increased throughout the cell cycle. However, in psoriatic TAC, a slight decrease in IL-1α and IL-1RA levels was observed between G0/G1 and S followed by a delayed increase between S and G2/M. IL-1β levels in psoriatic TAC varied little throughout the cell cycle. Thus, we were able to detect precisely the regulation of IL-1/IL-1RA intracellular levels during the keratinocyte cell cycle and differentiation, showing notably decreased IL-1β upregulation in psoriatic keratinocytes progressing through the cell cycle.
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House dust mite (HDM) allergens are important factors in the increasing prevalence of asthma. The lung epithelium forms a barrier that allergens must cross before they can cause sensitization. However, the mechanisms involved are unknown. Here we show that the cysteine proteinase allergen Der p 1 from fecal pellets of the HDM Dermatophagoides pteronyssinus causes disruption of intercellular tight junctions (TJs), which are the principal components of the epithelial paracellular permeability barrier. In confluent airway epithelial cells, Der p 1 led to cleavage of the TJ adhesion protein occludin. Cleavage was attenuated by antipain, but not by inhibitors of serine, aspartic, or matrix metalloproteinases. Putative Der p 1 cleavage sites were found in peptides from an extracellular domain of occludin and in the TJ adhesion protein claudin-1. TJ breakdown nonspecifically increased epithelial permeability, allowing Der p 1 to cross the epithelial barrier. Thus, transepithelial movement of Der p 1 to dendritic antigen-presenting cells via the paracellular pathway may be promoted by the allergen's own proteolytic activity. These results suggest that opening of TJs by environmental proteinases may be the initial step in the development of asthma to a variety of allergens.
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Approximately 2% of the Caucasian population is affected by psoriasis (PS); a chronic inflammatory skin disease triggered by both genetic and environmental risk factors. In addition to a major contribution from the HLA class I region, PS susceptibility loci have been mapped to a number of regions including 1q21, 3q21, 4qter, 14q31-q32, 17q24-q25, 19p13.3 and 20p. Some of these overlap with loci implicated in other autoimmune/inflammatory diseases. Global gene expression studies are beginning to provide insights into the etiology of these and other complex diseases. We used Affymetrix oligonucleotide arrays comprising approximately 12 000 known genes to initiate a more comprehensive analysis of the transcriptional changes that occur in involved and uninvolved skin of 15 psoriatic patients versus six normal controls. Expression levels of the transcripts detected on the arrays were first used to determine the relationship of samples to each other using hierarchical clustering. This analysis clearly differentiated involved psoriatic skin from uninvolved and normal skin. Clusters of differentially expressed genes with similar expression patterns in the same samples were then identified. Six out of 32 clusters contained a total of 177 transcripts that were differentially expressed in involved psoriatic skin versus normal skin. These differences were independent of the gender, age, skin site and HLA class I status of the patient. Ten of the 177 genes were also differentially expressed in uninvolved skin, and several mapped to regions previously shown to harbor psoriasis susceptibility loci.
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This study demonstrates the presence of tight junction antigens in adult and developing human epidermis. Indirect immunofluorescence labeling and immunoelectron microscopy with antibodies to ZO-1 and occludin localized tight junction components ZO-1 and occludin to a narrow zone of the granular cells of adult epidermis. Double immunolabeling for tight junction components with adherens junction or desmosome proteins suggested that occludin is more specific for tight junctions than ZO-1, which may also be associated with adherens junctions. In developing skin, tight junctions interconnected the peridermal cells, and after the fetal stratification localized to the granular cell layer. Immunolabeling of psoriasis, lichen planus, and ichthyosis vulgaris, representing aberrant differentiation of the epidermis, showed that these conditions were associated with relocation of ZO-1 and occludin to the spinous cells. Cultures of epidermal keratinocytes, which offer a useful model for the formation of cellular contacts, revealed that tight junction components, ZO-1 and occludin, displayed a marked degree of colocalization relatively late during the process when the fusion zone had assumed a linear appearance. This suggests that the formation of adherens junctions and desmosomes precedes that of tight junctions. We speculate that the epidermal barrier, isolating the human body from the external environment, is in part formed by tight junctions of stratum granulosum.
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The tight junction (TJ) and its adhesion molecules, claudins, are responsible for the barrier function of simple epithelia, but TJs have not been thought to play an important role in the barrier function of mammalian stratified epithelia, including the epidermis. Here we generated claudin-1-deficient mice and found that the animals died within 1 d of birth with wrinkled skin. Dehydration assay and transepidermal water loss measurements revealed that in these mice the epidermal barrier was severely affected, although the layered organization of keratinocytes appeared to be normal. These unexpected findings prompted us to reexamine TJs in the epidermis of wild-type mice. Close inspection by immunofluorescence microscopy with an antioccludin monoclonal antibody, a TJ-specific marker, identified continuous TJs in the stratum granulosum, where claudin-1 and -4 were concentrated. The occurrence of TJs was also confirmed by ultrathin section EM. In claudin-1-deficient mice, claudin-1 appeared to have simply been removed from these TJs, leaving occludin-positive (and also claudin-4-positive) TJs. Interestingly, in the wild-type epidermis these occludin-positive TJs efficiently prevented the diffusion of subcutaneously injected tracer (approximately 600 D) toward the skin surface, whereas in the claudin-1-deficient epidermis the tracer appeared to pass through these TJs. These findings provide the first evidence that continuous claudin-based TJs occur in the epidermis and that these TJs are crucial for the barrier function of the mammalian skin.
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On interaction with the intestine, the mycotoxin ochratoxin A is know to cause rapid inflammation, diarrhea, and increased bacterial translocation. All these effects are consistent with a decrease in epithelial barrier function. However, this has not been shown directly. We determined that ochratoxin A is able to reduce the barrier properties of the model intestinal cell line Caco-2. Over 24 h, ochratoxin A reduces the transepithelial electrical resistance of Caco-2 monolayers growing on Transwell filters by approximately 40%. At the same time, the permeability of the monolayer is increased with respect to 4- and 10-kDa FITC dextrans, but not to 20- or 40-kDa dextrans. Immunoblotting and immunofluorescence reveal that the decrease in barrier properties is concomitant with disappearance of claudins 3 and 4, but not claudin 1 from Caco-2 cell membranes. These results suggest that ochratoxin A is able to modulate the barrier function of Caco-2 cells by removal of specific claudin isoforms.
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Tight junction associated proteins are key molecular components governing cellular adhesion, polarity and glandular differentiation. Tight junction proteins also play critical roles in cellular proliferation and neoplastic pathways via their functions as couplers of the extracellular milieu to intracellular signaling pathways and the cytoskeleton. Neoplastic cells frequently exhibit structural and functional deficiencies in the tight junction. The purpose of this study was to determine the pattern of expression and prognostic value of four tight junction associated proteins, claudin-1, claudin-4, occludin and ZO-1 in a cohort of TNM stage II colon cancer using tissue microarray technology. In this study, we retrospectively analyzed, resected and otherwise untreated paraffin embedded specimens from 129 consecutive patients with TNM stage II colonic carcinomas for claudin-1, claudin-4, occludin and ZO-1 protein expression by immunohistochemistry. Seventy-five, 58, 56 and 44% of the tumors exhibited normal to elevated expression levels (+2 and +3 immunopositivity) of claudin-1, claudin-4, occludin and ZO-1 respectively. Low expression levels of claudin-1 and ZO-1 were directly associated with higher tumor grade (P=0.05 and 0.03 respectively). Multivariate analysis indicated that lymphovascular invasion (P=0.01) and low levels of claudin-1 (P=0.0001) expression were independent predictors of recurrence and that reduced claudin-1 expression (P=0.0001) was associated with poor survival. This study is the first to comprehensively examine the expression of several tight junction associated proteins in colonic neoplasms and to correlate their expression with disease progression. Loss of claudin-1 expression proved to be a strong predictor of disease recurrence and poor patient survival in stage II colon cancer.
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A key feature of inflammatory bowel disease (IBD) is disruption of the intestinal epithelial barrier by unknown mechanisms. Integrity of the epithelial barrier is determined by an apical junctional complex that is composed of tight junction (TJ) and adherens junction (AJ). Previous observations have suggested that alterations in the apical junctional complex occur in IBD. Localization studies in mucosal biopsies from IBD patients have revealed disappearance of key TJ (occludin, JAM1, ZO1, claudin 1) and AJ (E-cadherin, beta-catenin) proteins from intercellular junctions. In vitro experiments examining the effects of inflammatory cytokines on model intestinal epithelial monolayers suggest that disruption of the epithelial barrier is associated with internalization of transmembrane TJ proteins, JAM1, ocdudin and claudins 1/4. The mechanism(s) of internalization of intercellular junctions can be modelled in vitro by calcium depletion of confluent epithelial cell monolayers. Using this model, we have observed rapid, orchestrated endocytosis of all AJ and TJ proteins into a subapical cytoplasmic compartment that is independent of caveolae/lipid rafts and macropinocytosis. However, inhibitors of clathrin-mediated endocytosis effectively block internalization of AJs and TJs, and junctional proteins colocalize with clathrin. Interestingly, internalized AJ and TJ proteins enter early endosomes followed by movement to organelles that do not label with markers of late and recycling endosomes, lysosomes or Golgi but appear to represent a unique storage compartment that colocalizes with t-SNARE protein, syntaxin 4. A better understanding of the mechanisms of junctional internalization and recycling will likely provide new insights into the mechanisms of altered barrier function in IBD.
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Psoriasis is one of the most common human skin diseases and is considered to have key genetic underpinnings. It is characterized by excessive growth and aberrant differentiation of keratinocytes, but is fully reversible with appropriate therapy. The trigger of the keratinocyte response is thought to be activation of the cellular immune system, with T cells, dendritic cells and various immune-related cytokines and chemokines implicated in pathogenesis. The newest therapies for psoriasis target its immune components and may predict potential treatments for other inflammatory human diseases.
Article
Approximately 2% of the Caucasian population is affected by psoriasis (PS); a chronic inflammatory skin disease triggered by both genetic and environmental risk factors. In addition to a major contribution from the HLA class I region, PS susceptibility loci have been mapped to a number of regions including 1q21, 3q21, 4qter, 14q31-q32, 17q24-q25, 19p13.3 and 20p. Some of these overlap with loci implicated in other autoimmune/inflammatory diseases. Global gene expression studies are beginning to provide insights into the etiology of these and other complex diseases. We used Affymetrix oligonucleotide arrays comprising approximately 12 000 known genes to initiate a more comprehensive analysis of the transcriptional changes that occur in involved and uninvolved skin of 15 psoriatic patients versus six normal controls. Expression levels of the transcripts detected on the arrays were first used to determine the relationship of samples to each other using hierarchical clustering. This analysis clearly differentiated involved psoriatic skin from uninvolved and normal skin. Clusters of differentially expressed genes with similar expression patterns in the same samples were then identified. Six out of 32 clusters contained a total of 177 transcripts that were differentially expressed in involved psoriatic skin versus normal skin. These differences were independent of the gender, age, skin site and HLA class I status of the patient. Ten of the 177 genes were also differentially expressed in uninvolved skin, and several mapped to regions previously shown to harbor psoriasis susceptibility loci.
Article
The topical application of 0.1% retinoic acid (RA) on human skin over a period of 4 days, whether or not under occlusion, did not increase either IL-iα or β immunoreactivity as determined by a sensitive enzymoimmunoassay. No down modulation was seen following the application of a potent topical corticosteroid. Occlusion increased the yield of IL-iβ immunoreactivity. Immunoblot patterns of epidermal extracts revealed both the mature form of IL-i (17 kDa) and the precursor (36 kDa) and were identical in amounts whether the specimens were from controls or from RA- or corticosteroid-trcated skin. There was a slight modification in the pattern of high molecular weight proteins (52 kDa) probed by the anti-IL-iα and β sera. It appears that the IL-1 epidermal immunoreactive pools are barely amenable to modulation because they represent a storage form linked to end-stages of keratinocyte differentiation.
Article
In simple epithelia, tight junctions are well developed and have barrier and fence functions. On the other hand, tight junctions are less developed in stratified epithelia. In the rodent epidermis, only maculae occludentes (i.e. focal strands or spot tight junctions) are observed in the most superficial zone of the granular cell layer. Occludin is an integral membrane protein, and is localized at tight junctions in simple epithelia. In normal epidermis, occludin is expressed at the maculae occludentes in the granular cell layer, indicating that it is associated with keratinocyte differentiation. Thus, we examined occludin expression in psoriasis, in which differentiation of keratinocytes is impaired. In psoriasis, occludin was expressed more broadly in the upper epidermis than in normal epidermis. In addition, immunoelectron microscopy showed occludin to be concentrated on the maculae occludentes in the spinous layer of psoriatic skin. These findings indicate that occludin and the formation of tight junctions are related to the proliferation and differentiation of keratinocytes, and to the pathogenesis of psoriasis.
Article
Tight junction proteins comprise a novel group of integral membrane proteins necessary for cell-to-cell contacts and responsible for the barrier function in epithelial and endothelial cells in various tissues. The tight junction membrane domain contains at least three distinct proteins, named occludin, claudin and junctional adhesion molecule. Claudins are products of a gene family consisting of more than 20 members. We investigated mRNA expression of occludin and 13 different claudins in neonatal foreskin, adult skin and cultivated HaCaT keratinocytes by the Northern blot technique, and performed immunohistochemical staining of adult skin for occludin, claudin 1 and claudin 2. Occludin, claudin 1 and claudin 3 mRNAs were expressed in human neonatal and adult keratinocytes as well as in HaCaT keratinocytes. All other tested claudins were negative. Immunohistochemical staining of adult skin was positive for occludin in the intercellular space of the granular layer, and for claudin 1 in the inter-cellular space of the spinosum layer and basal layer, but negative for claudin 2 in all skin layers. Claudin 1 was also positive in the outer root sheath of hair follicles. Our results indicate that occludin, claudin 1 and claudin 3 are involved in cell-to-cell contacts between keratinocytes in human epidermis, although their functional importance remains unknown.
Article
Cutaneous inflammation is characterized by the infiltration of leukocytes such as polymorphonuclear neutrophils (PMNs), lymphocytes, and monocytes into the epidermis, dermis, or subcutaneous tissue in response to infectious or immunologic stimuli, in wound healing, or in response to trauma. In recent years, it has been found that cell-surface proteins on leukocytes, endothelial cells, and keratinocytes are critical elements in the initiation and evolution of cutaneous inflammation. In order for peripheral blood leukocytes to leave the circulatory system and enter tissue parenchyma, they must first bind to endothelial cells, pass between them, and traverse the vascular basement membrane. In this article we will examine both leukocyte-endothelial cell binding and evidence indicating that various cell-surface molecules present on leukocytes and endothelial cells, known as cell adhesion molecules (CAMs), interact with one another in specific fashion. This interaction or binding is a critical occurrence and its inhibition leads to downregulation of inflammation. Furthermore, some CAMs can be either induced or upregulated on leukocytes and endothelial cells by various proinflammatory cytokines. This tends to upregulate inflammation. It has become increasingly clear that the time-course of inflammation and its exquisite anatomic specificity are related to the regulation of expression of CAMs.
Article
The topical application of 0.1% retinoic acid (RA) on human skin over a period of 4 days, whether or not under occlusion, did not increase either IL-1 alpha or beta immunoreactivity as determined by a sensitive enzymoimmunoassay. No down modulation was seen following the application of a potent topical corticosteroid. Occlusion increased the yield of IL-1 beta immunoreactivity. Immunoblot patterns of epidermal extracts revealed both the mature form of IL-1 (17 kDa) and the precursor (36 kDa) and were identical in amounts whether the specimens were from controls or from RA- or corticosteroid-treated skin. There was a slight modification in the pattern of high molecular weight proteins (52 kDa) probed by the anti-IL-1 alpha and beta sera. It appears that the IL-1 epidermal immunoreactive pools are barely amenable to modulation because they represent a storage form linked to end-stages of keratinocyte differentiation.
Article
One hundred thirty-six unselected patients with Crohn's disease (43 men, 93 women) were studied for the possibility of psoriasis and questioned regarding their family history, as were 136 controls, matched for age and sex. Psoriasis was present in 13 of the 136 patients with Crohn's disease (9.6%), compared with three of 136 controls (2.2%) (p less than 0.02). Age at onset and anatomical site of Crohn's disease did not influence the result, and there was no difference between the sexes. Fourteen (three with psoriasis) of the 136 Crohn's patients (10%) had a family history of psoriasis in first-degree relatives compared with four of 136 controls (2.9%) (p less than 0.02). Psoriasis is more common in patients with Crohn's disease and their first-degree relatives than in controls, suggesting the possibility of a genetic link. Psoriasis should be included among the extraintestinal manifestations of the condition.
Article
A neutrophil-activating peptide (NAP)/IL-8 produced by LPS-stimulated human peripheral blood monocytes was biochemically purified and functionally characterized by different investigators. Work conducted in our laboratory showed that NAP/IL-8 as well as variants of this peptide are produced by a variety of cells (e.g., monocytes, T lymphocytes, endothelial cells) and that lesional psoriatic scales contain large amounts of biologically active NAP/IL-8. We now investigated human dermal fibroblasts for production of NAP/IL-8. The peptide was detected by immunocytochemistry by using the mAb 46E5. NAP/IL-8 mRNA was visualized by high resolutive fluorescent in situ hybridization with biotinylated antisense/sense RNA probes. Among the various stimuli used [human (h)rIL-1 alpha, hrTNF-alpha, hrIL-3, hr-granulocyte-macrophage-CSF, LPS, FMLP, and platelet-activating factor (PAF)] only hrIL-1 alpha (100 U/ml) and hrTNF-alpha (100 ng/ml) induced the transcription and translation of NAP/IL-8. In contrast to monocytes, LPS was without effect in cultured human dermal fibroblasts. Both NAP/IL-8 and NAP/IL-8 mRNA were found in the cytoplasm adjacent to the nucleus, but interestingly NAP/IL-8 mRNA was not restricted to the cytoplasm. In positive cells only two small bright spots were randomly distributed in the nucleus. Most likely these spots represent transcription sites where NAP/IL-8 mRNA is accumulated during gene expression. Our observations show that stimulation of dermal fibroblasts with the cytokines hrIL-1 alpha and hrTNF-alpha results in expression of IL-8.
Article
Based on nuclear magnetic resonance (NMR) spectroscopy and other evidence, it has been argued that tissues accumulate, and retain, ions in a binding process by a highly structured water-protoplasm system; thus active membrane transport need not be involved. Recent evidence has accounted for the loss of resonance intensity usually found when investigating quadrupolar ions in animal tissue. Using continuous wave NMR spectroscopy, we have examined two quadrupolar ions, Na(+) and K(+), in pea stem cells where about 90% of the ion content is in the largely aqueous vacuoles having a membrane barrier. The NMR resonances from these ions correspond to almost 100% of that expected from independent measurements of total ion content. This indicates that the ions are retained as free ions after accumulation. The small fraction which is NMR invisible may represent ions in an ordered, anisotropic environment, such as that in the wall or cytoplasm.
Article
EJACULATED spermatozoa cannot be preserved satisfactorily by conventional fixation procedures for electron microscopy. Osmium tetroxide (OsO4) fixation of crude ejaculate consistently produces a variety of artefacts such as separation of the plasma membrane from the acrosome, widening of nuclear vacuoles, erosion of the acrosome, and swelling of mitochondria1-3. These alterations could be the consequence of the rapid destruction of the fixative by the proteins of the seminal plasma. Similar results are obtained whenever the semen is washed either in salt solutions3,4 or in other media5-7 before osmium tetroxide fixation. In these cases, the structural alterations of the sperm are probably caused by osmotic imbalances. Fixation with glutaraldehyde is also unsuccessful in that it is associated with the typical artefacts of this fixative (our unpublished work).
Article
Recent investigations have revealed the involvement of cytokines in the pathogenesis of psoriasis. This study examined the amount of inflammatory cytokines--interleukin-1 (IL-1), interleukin-6 (IL-6) and granulocyte macrophage colony-stimulating factor (GM-CSF)--released into the supernatants of organ cultures of involved and uninvolved skin from psoriatic patients and normal skin from healthy individuals. Bioassays were employed to detect the activities of IL-1 and IL-6. Enzyme-linked immunosorbent assay (ELISA) methods were used to quantitate immunoreactive IL-1 alpha, IL-1 beta, IL-6 and GM-CSF. The activity of IL-1 in uninvolved psoriatic skin was found to be increased relative to that in involved and normal skin, while immunoreactive IL-1 beta was found only in involved skin. A neutralization experiment showed that bioactive IL-1 was mostly attributable to IL-1 alpha. Uninvolved psoriatic skin also secreted higher amounts of both bioactive and immunoreactive IL-6 compared with involved skin. Immunoreactive GM-CSF was detected in uninvolved skin only. These cytokines detected in uninvolved skin may have been released from epidermal or mesenchymal cells, since uninvolved skin contained fewer inflammatory infiltrates. Our results offer additional evidence that increased amounts of inflammatory cytokines in uninvolved skin may provide a preliminary condition and play important roles in the initial events in the evolution of psoriatic lesions.
Article
The induction phase of contact sensitization is associated with the movement of epidermal Langerhans cells (LC) from the skin and their migration, via afferent lymphatics, to draining lymph nodes where they accumulate as immunostimulatory dendritic cells (DC). It has been demonstrated previously that tumour necrosis factor-alpha (TNF-alpha) provides an important signal for LC migration and that in the absence of this cytokine, movement of LC from the epidermis to regional lymph nodes is inhibited. Recent evidence indicates that interleukin-1 beta (IL-1 beta), a cytokine produced in murine epidermis exclusively by LC, may also play a role in LC migration. The purpose of the investigations described here was to clarify, using relevant neutralizing anti-cytokine antibodies, the contributions made by TNF-alpha and IL-1 beta to the migration of LC from the epidermis. It was found that like anti-TNF-alpha, anti-IL-1 beta administered systemically to mice (by intraperitoneal injection), prior to skin sensitization with the contact allergen oxazolone, resulted in a marked inhibition of DC accumulation in draining lymph nodes. It was shown also that anti-IL-1 beta inhibited TNF-alpha-induced LC migration and DC accumulation and that; in similar fashion, the stimulation of LC migration and DC accumulation induced by IL-1 beta was compromised by prior treatment with anti-TNF-alpha. Based upon these data it is proposed that the stimulation of LC migration in response to skin sensitization requires the receipt by LC of two independent signals, one provided by TNF-alpha and the other by IL-1 beta. Morphological analyses of LC in epidermal sheets prepared from animals exposed to these cytokines with or without prior systemic treatment with anti-cytokine antibody suggested that the changes induced in LC by TNF-alpha and IL-1 beta may include the altered expression of adhesion molecules and acquisition of the ability to interact with and pass through the basement membrane.
Article
Three integral membrane proteins, clau- din-1, -2, and occludin, are known to be components of tight junction (TJ) strands. To examine their ability to form TJ strands, their cDNAs were introduced into mouse L fibroblasts lacking TJs. Immunofluorescence microscopy revealed that both FLAG-tagged claudin-1 and -2 were highly concentrated at cell contact sites as planes through a homophilic interaction. In freeze-fracture replicas of these contact sites, well-developed networks of strands were identified that were similar to TJ strand networks in situ and were specifically labeled with anti-FLAG mAb. In glutaraldehyde-fixed samples, claudin-1-induced strands were largely associated with the protoplasmic (P) face as mostly continuous structures, whereas claudin-2-induced strands were discontinuous at the P face with complementary grooves at the extracellular (E) face which were occupied by chains of particles. Although occludin was also concentrated at cell contact sites as dots through its homophilic interaction, freeze-fracture replicas identified only a small number of short strands that were labeled with anti-occludin mAb. However, when occludin was cotransfected with claudin-1, it was concentrated at cell contact sites as planes to be incorporated into well- developed claudin-1-based strands. These findings suggested that claudin-1 and -2 are mainly responsible for TJ strand formation, and that occludin is an accessory protein in some function of TJ strands.
Article
Mechanisms of diarrhea in ulcerative colitis (UC) are still unknown. Functional and structural characterization of epithelial barrier and transport properties in ulcerative colitis (UC) was performed. Inflamed sigmoid colon epithelium from UC patients was studied by alternating current impedance analysis to determine the pure epithelial resistance as a measure of intestinal barrier function. Tight junction (TJ) structure was investigated by freeze-fracture electron microscopy. Although total wall resistance was reduced in UC by 50%, impedance analysis uncovered a much more pronounced barrier defect. Epithelial resistance decreased from 95 +/- 5 to 20 +/- 3 omega3. cm2, which in conventional analysis is masked by an increase in subepithelial resistance from 14 +/- 1 to 36 +/- 3 omega3. cm2 caused by inflammation. This was paralleled by a change in epithelial cell TJ structure in UC. Strand count decreased from 6.94 +/- 0.25 to 4.76 +/- 0.47 at the surface and from 7.26 +/- 0.31 to 5.46 +/- 0.37 in the crypts. Conclusions: The inflamed colonic mucosa in UC has an impaired barrier function that is much more pronounced than previously assumed. An altered TJ structure contributes to this barrier defect which, because of increased back leak, can reduce net ion transport. Thus, a leak-flux mechanism contributes to the diarrhea in UC.
Article
Chronic sun exposure results in photoaged skin with deep coarse wrinkles and loss of elasticity. We have examined the distribution and abundance of fibrillin-rich microfibrils, key structural components of the elastic fiber network, in photoaged and photoprotected skin. Punch biopsies taken from photoaged forearm and from photoprotected hip and upper inner arm of 16 subjects with a clinical range of photoaging were examined for fibrillin-1 and fibrillin-2 expression and microfibril distribution. In situ hybridization revealed decreased fibrillin-1 mRNA but unchanged fibrillin-2 mRNA levels in severely photoaged forearm biopsies relative to photoprotected dermal sites. An immunohistochemical approach demonstrated that microfibrils at the dermal-epidermal junction were significantly reduced in moderate to severely photoaged forearm skin. Confocal microscopy revealed that the papillary dermal microfibrillar network was truncated and depleted in photoaged skin. These studies highlight that the fibrillin-rich microfibrillar network associated with the upper dermis undergoes extensive remodeling following solar irradiation. These changes may contribute to the clinical features of photoaging, such as wrinkle formation and loss of elasticity.
Article
Inflammatory bowel disease (IBD) consisting of ulcerative colitis (UC) and Crohn's (CD) typically displays a waxing and waning course punctuated by disease flares that are characterized by transepithelial migration of neutrophils (PMN) and altered barrier function. Since epithelial barrier function is primarily regulated by the apical most intercellular junction referred to as the tight junction (TJ), our aim was to examine expression of TJ and adherens junction (AJ) proteins in relation to PMN infiltration in mucosal tissue samples from patients with active IBD. Expression of epithelial intercellular TJ proteins (occludin, ZO-1, claudin-1, and JAM) and subjacent AJ (beta-catenin and E-cadherin) proteins were examined by immunoflourescence/confocal microscopy, immunohistochemistry, and Western blotting. Colonic mucosa from patients with UC revealed dramatic, global down-regulation of the key TJ transmembrane protein occludin in regions of actively transmigrating PMN and in quiescent areas in the biopsy samples. Significant decreases in occludin expression were observed at the protein and mRNA levels by Western and Northern blotting. In contrast, expression of other TJ and AJ proteins such as ZO-1, claudin-1, JAM, beta-catenin, and E-cadherin were down-regulated only in epithelial cells immediately adjacent to transmigrating PMN. Analysis of inflamed mucosa from Crohn's disease patients mirrored the results obtained with UC patients. No change in TJ and AJ protein expression was observed in colonic epithelium from patients with collagenous colitis or lymphocytic colitis that are respectively characterized by a thickened subepithelial collagen plate and increased intraepithelial lymphocytes. These results suggest that occludin expression is diminished in IBD by mechanisms distinct from those regulating expression of other intercellular junction proteins. We speculate that down-regulation of epithelial occludin may play a role in enhanced paracellular permeability and PMN transmigration that is observed in active inflammatory bowel disease.
Article
The primacy of the immune system in the pathogenesis of psoriasis is a well-established concept to the extent that psoriasis has been classified as a T-cell-mediated, autoimmune disease. An explosion of knowledge concerning immunological events in psoriasis and the clinical efficacy of immunologically directed therapies, such as cyclosporin, support this concept. Armed with this understanding and modern biotechnology, novel interventions have been developed to treat psoriasis. The aim of these therapies is to provide selective, immunologically directed intervention with the hope that such specificity will result in fewer side-effects than traditional therapies. Of interest and importance, these pharmaceutical interventions also act as a form of investigational tool in psoriasis. Their relative efficacy in the psoriatic process provides useful insights into the hierarchial importance of immune events in the disease process and recent evidence suggests that innate rather than acquired immunity has a key role. This article reviews recent developments in immune-based therapies for psoriasis.
Article
Occludin and several proteins of the claudin family have been identiried in simple epithelia and in endothelia as major and structure-determining transmembrane proteins clustered in the barrier-forming tight junctions (TJ), where they are associated with a variety of TJ plaque proteins, including protein ZO-1. To examine whether TJ also occur in the squamous stratified epithelium of the interfollicular human epidermis we have applied several microscopic and biochemical techniques. Using RT-PCR techniques, we have identiried mRNAs encoding protein ZO-1, occludin and claudins 1, 4, 7, 8, 11, 12, and 17 in both tissues, skin and cultured keratinocytes, whereas claudins i and 10 have only been detected in skin tissue. By immunocytochemistry we have localized claudin-1, occludin and protein ZO-1 in distinct plasma membrane structures representing cell-cell attachment zones. While claudin-1 occurs in plasma membranes of all living cell layers, protein ZO-1 is concentrated in or even restricted to the uppermost layers, and occludin is often detected only in the stratum granulosum. Using electron microscopy, typical TJ structures ("kissing points") as well as some other apparently related junctional structures have been detected in the stratum granulosum, interspersed between desmosomes. Modes and patterns of TJ formation have also been studied in experimental model systems, e.g., during wound healing and stratification as well as in keratinocyte cultures during Ca2+-induced stratification. We conclude that the epidermis contains in the stratum granulosum a continuous zonula occludens-equivalent structure with typical TJ morphology and molecular composition, characterized by colocalization of occludin, claudins and TJ plaque proteins. In addition, cell-cell contact structures and certain TJ proteins can also be detected in other epidermal cell layers in specific cell contacts. The pattern of formation and possible functions of epidermal TJ and related structures are discussed.
Article
Tight junction proteins comprise a novel group of integral membrane proteins necessary for cell-to-cell contacts and responsible for the barrier function in epithelial and endothelial cells in various tissues. The tight junction membrane domain contains at least three distinct proteins, named occludin, claudin and junctional adhesion molecule. Claudins are products of a gene family consisting of more than 20 members. We investigated mRNA expression of occludin and 13 different claudins in neonat