Developmental regulation of claudin localization by fetal alveolar epithelial cells
ABSTRACT Tight junction proteins in the claudin family regulate epithelial barrier function. We examined claudin expression by human fetal lung (HFL) alveolar epithelial cells cultured in medium containing dexamethasone, 8-bromo-cAMP, and isobutylmethylxanthanine (DCI), which promotes alveolar epithelial cell differentiation to a type II phenotype. At the protein level, HFL cells expressed claudin-1, claudin-3, claudin-4, claudin-5, claudin-7, and claudin-18, where levels of expression varied with culture conditions. DCI-treated differentiated HFL cells cultured on permeable supports formed tight transepithelial barriers, with transepithelial resistance (TER) >1,700 ohm/cm(2). In contrast, HFL cells cultured in control medium without DCI did not form tight barriers (TER <250 ohm/cm(2)). Consistent with this difference in barrier function, claudins expressed by HFL cells cultured in DCI medium were tightly localized to the plasma membrane; however, claudins expressed by HFL cells cultured in control medium accumulated in an intracellular compartment and showed discontinuities in claudin plasma membrane localization. In contrast to claudins, localization of other tight junction proteins, zonula occludens (ZO)-1, ZO-2, and occludin, was not sensitive to HFL cell phenotype. Intracellular claudins expressed by undifferentiated HFL cells were localized to a compartment containing early endosome antigen-1, and treatment of HFL cells with the endocytosis inhibitor monodansylcadaverine increased barrier function. This suggests that during differentiation to a type II cell phenotype, fetal alveolar epithelial cells use differential claudin expression and localization to the plasma membrane to help regulate tight junction permeability.
- SourceAvailable from: Ylermi Soini
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- "Bronchial epithelium also expresses cingulin, ZO-1, ZO-2, and ZO-3  . Occludin, ZO-1, ZO-2, ZO-3, cingulin and JAM-1 are expressed in alveolar cells   . "
ABSTRACT: Tight junctions are structures located in the apicobasal region of the cell membranes. They regulate paracellular solute and electrical permeability of cell layers. Additionally, they influence cellular polarity, form a paracellular fence to molecules and pathogens and divide the cell membranes to apical and lateral compartments. Tight junctions adhere to the corresponding ones of neighbouring cells and by this way also mediate attachment of the cells to one other. Molecules forming the membranous part of tight junctions include occludin, claudins, tricellulin and junctional adhesion molecules. These molecules are attached to scaffolding proteins such as ZO-1, ZO-2 and ZO-3 through which signals are mediated to the cell interior. Expression of tight junction proteins, such as claudins, may be up- or downregulated in cancer and they are involved in EMT thus influencing tumor spread. Like in tumors of other sites, lung tumors show changes in the expression in tight junction proteins. In this review the significance of tight junctions and its proteins in lung cancer is discussed with a focus on the proteins forming the membranous part of these structures.International journal of clinical and experimental pathology 01/2012; 5(2):126-36. · 1.78 Impact Factor
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- "Induction of claudin-5 by glucocorticoids has been described in rat brain microvessel endothelial cells (BMEC, GPNT), where addition of hydrocortisone to the cultures resulted in fewer frayed junctions and a more uniform distribution of claudin-5 at the cell borders as compared with cultures without hydrocortisone treatment  . In human alveolar epithelial cells, as well as in HUVEC claudin-5 has been shown to be one of the major genes up-regulated during differentiation in culture   . Also expression of adherens proteins, such as E-cadherin or VE-cadherin was enhanced by glucocorticoids  . "
ABSTRACT: Claudin-5, an integral tight junction protein component, plays a critical role in permeability of the endothelial cell barrier. Recently, we have shown that claudin-5 protein is down-regulated by the proinflammatory cytokine TNF alpha and its levels restored by dexamethasone treatment. In order to investigate the regulation of claudin-5 at the transcriptional level, we have cloned the murine claudin-5 promoter. The claudin-5 promoter sequence (1131 bp) showed no consensus TATA-box. We identified putative transcription factor binding sites, including six full and two half sites degenerated glucocorticoid-response elements (GREs), two NFkappaB, three Sp1, one Sp2, one Ap2, as well as three E-boxes. Serially deleted promoter constructs showed high basal activity. TNF alpha significantly reduced the promoter activity and mRNA levels of claudin-5 in brain cEND and myocardial MyEND endothelial cells. Dexamethasone treatment led to a significant increase of the murine claudin-5 promoter activity and mRNA levels in cEND cells. However, no claudin-5 induction could be observed in MyEND cells in response to dexamethasone. Our studies suggest tissue-specific regulation of the claudin-5 gene via glucocorticoids and a high vulnerability of claudin-5 to TNF alpha. This could be an important mechanism in diseases accompanied by the release of proinflammatory cytokines, for example in patients with chronic heart failure or multiple sclerosis.Molecular and Cellular Endocrinology 11/2008; 298(1-2):19-24. DOI:10.1016/j.mce.2008.09.041 · 4.24 Impact Factor
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- "tion of the TJ protein claudin - 5 at the cell borders as compared with cultures without GC treatment ( Romero et al . 2003 ; Calabria et al . 2006 ) . A recent screen of gene expression by human alveolar epithelial cells indicated that claudin - 5 is one of the major genes up - regulated during differentiation in culture ( Gonzales et al . 2002 ; Daugherty et al . 2004 ) . On the other hand , responsivity of the human VE - cadherin gene to GCs could not be observed in hCMEC / D3 cells , while it represents a GC target in the mouse ( Blecharz et al . 2008 ) . Reports on GC effects on VE - cadherin in other species or tissues could not be found , while the epithelial adherens protein , E - cadherin was "
ABSTRACT: Homeostasis of the central nervous system (CNS) microenvironment is maintained by the blood-brain barrier (BBB) which regulates the transport of molecules from blood into brain and back. Many disorders change the functionality and integrity of the BBB. Glucocorticoids are being used sucessfully in the treatment of some disorders while their effects on others are questionable. In addition, conflicting results between clinical and experimental experience using animal models has arisen, so that the results of molecular studies in animal models need to be revisited in an appropriate in vitro model of the human BBB for more effective treatment strategies. Using the human brain microvascular endothelial cell line hCMEC/D3, the influence of glucocorticoids on the expression of barrier constituting adherens junction and tight junction transmembrane proteins (VE-cadherin, occludin, claudins) was investigated and compared to other established BBB models. In hCMEC/D3 cells the administration of glucocorticoids induced expression of the targets occludin 2.75 +/- 0.04-fold and claudin-5 up to 2.32 +/- 0.11-fold, which is likely to contribute to the more than threefold enhancement of transendothelial electrical resistance reflecting barrier tightness. Our analyses further provide direct evidence that the GC hydrocortisone prevents endothelial barrier breakdown in response to pro-inflammatory stimuli (TNFalpha administration), which could be demonstrated to be partly based on maintenance of occludin levels. Our studies strongly suggest stabilization of BBB function as a mode of GC action on a molecular level in the human brain vasculature.The Journal of Physiology 05/2008; 586(7):1937-49. DOI:10.1113/jphysiol.2007.146852 · 4.54 Impact Factor