Download the Free Unbound MEDLINE PubMed App to your smartphone or tablet.
Available for iPhone, iPad, iPod touch, and Android.
tight junction [keywords]
- Resolution of central nervous system astrocytic and endothelial sources of CCL2 gene expression during evolving neuroinflammation. [Journal Article]
- Fluids Barriers CNS 2014; 11(1):6.
The chemokine CCL2 is a critical mediator of neuroinflammation in diseases such as multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). CCL2 drives mononuclear cell infiltration into the central nervous system (CNS), alters expression and distribution of microvascular endothelial tight junction proteins, and disrupts the blood-brain and blood-spinal cord barriers. Immunohistochemistry has consistently revealed astrocytes to be a source of this chemokine during neuroinflammation, while providing less uniform evidence that CNS endothelial cells may also express CCL2. Moreover, the relative contributions of these cell types to the CNS pool of CCL2 during MS/EAE are unclear and the aim of this study was to investigate this further.CCL2 gene expression was determined by qRT-PCR in different populations of CNS cells at different times following EAE induced by immunization with MOG35-55 peptide and adjuvants, or after injection with adjuvants alone. CNS cells types were isolated by two different protocols: bulk isolation to yield crude microvascular and parenchymal fractions (containing astrocytes, other glia, and neurons), or laser capture microdissection (LCM) to acquire more precisely microvascular endothelial cells, astrocytes or other parenchymal cells.Both CNS microvessel and parenchymal populations prepared by crude bulk isolation showed up-regulation of CCL2 mRNA following MOG immunization or injection of adjuvants alone. More exact dissection by LCM revealed microvascular endothelial cells and astrocytes to be the specific sources of CCL2 gene induction following MOG immunization, while only astrocytes showed elevated CCL2 mRNA in response to just adjuvants. Astrocytes displayed the greatest degree of stimulation of CCL2 gene expression following EAE induction.High-precision LCM affirmed both microvascular endothelial cells and astrocytes as the major CNS sources of CCL2 gene expression during EAE. Given the high accessibility of the CNS microvascular endothelium, endothelial-derived CCL2 could prove a viable target for therapeutic intervention in neuroinflammatory disease.
- Knockout mice reveal key roles for claudin 18 in alveolar barrier properties and fluid homeostasis. [JOURNAL ARTICLE]
- Am J Respir Cell Mol Biol 2014 Mar 3.
Claudin proteins are major constituents of epithelial and endothelial tight junctions (TJ) that regulate paracellular permeability to ions and solutes. Claudin 18, a member of the large claudin family, is highly expressed in lung alveolar epithelium. To elucidate the role of claudin 18 in alveolar epithelial barrier function, we generated claudin 18 knockout (C18 KO) mice. C18 KO mice exhibited increased solute permeability and alveolar fluid clearance (AFC) compared to wild type (WT) controls. Increased AFC in C18 KO mice was associated with increased β-adrenergic receptor signaling together with activation of cystic fibrosis transmembrane conductance regulator (CFTR), higher epithelial sodium channel (ENaC) and Na-K-ATPase (Na pump) activity and increased Na-K-ATPase β1 subunit expression. Consistent with in vivo findings, C18 KO alveolar epithelial cell (AEC) monolayers exhibited lower transepithelial electrical resistance (RT) and increased solute and ion permeability with unchanged ion selectivity. Claudin 3 and claudin 4 expression was markedly increased, while claudin 5 was unchanged and occludin significantly decreased, in C18 KO mice. Microarray analysis revealed changes in cytoskeleton-associated gene expression in C18 KO mice, consistent with observed F-actin cytoskeletal rearrangement in AEC monolayers. These findings demonstrate a crucial non-redundant role for claudin 18 in regulation of alveolar epithelial TJ composition and permeability properties. Importantly, increased AFC in C18 KO mice identifies a role for claudin 18 in alveolar fluid homeostasis beyond its direct contributions to barrier properties that may at least in part serve to compensate for increased permeability.
- HIV-Associated Disruption of Tight and Adherens Junctions of Oral Epithelial Cells Facilitates HSV-1 Infection and Spread. [Journal Article]
- PLoS One 2014; 9(2):e88803.
Herpes simplex virus (HSV) types 1 and 2 are the most common opportunistic infections in HIV/AIDS. In these immunocompromised individuals, HSV-1 reactivates and replicates in oral epithelium, leading to oral disorders such as ulcers, gingivitis, and necrotic lesions. Although the increased risk of HSV infection may be mediated in part by HIV-induced immune dysfunction, direct or indirect interactions of HIV and HSV at the molecular level may also play a role. In this report we show that prolonged interaction of the HIV proteins tat and gp120 and cell-free HIV virions with polarized oral epithelial cells leads to disruption of tight and adherens junctions of epithelial cells through the mitogen-activated protein kinase signaling pathway. HIV-induced disruption of oral epithelial junctions facilitates HSV-1 paracellular spread between the epithelial cells. Furthermore, HIV-associated disruption of adherens junctions exposes sequestered nectin-1, an adhesion protein and critical receptor for HSV envelope glycoprotein D (gD). Exposure of nectin-1 facilitates binding of HSV-1 gD, which substantially increases HSV-1 infection of epithelial cells with disrupted junctions over that of cells with intact junctions. Exposed nectin-1 from disrupted adherens junctions also increases the cell-to-cell spread of HSV-1 from infected to uninfected oral epithelial cells. Antibodies to nectin-1 and HSV-1 gD substantially reduce HSV-1 infection and cell-to-cell spread, indicating that HIV-promoted HSV infection and spread are mediated by the interaction of HSV gD with HIV-exposed nectin-1. Our data suggest that HIV-associated disruption of oral epithelial junctions may potentiate HSV-1 infection and its paracellular and cell-to-cell spread within the oral mucosal epithelium. This could be one of the possible mechanisms of rapid development of HSV-associated oral lesions in HIV-infected individuals.
- Interleukin-6 disrupts blood-testis barrier through inhibiting protein degradation or activating phosphorylated ERK in Sertoli cells. [Journal Article]
- Sci Rep 2014.:4260.
It has been recently ascribed to several inflammatory cytokines (i.e. TGF-β3, TNF-α, and IL-1) a functional role in regulating Sertoli cell blood-testis barrier (BTB) dynamics. In the testis, IL-6 inhibits meiotic DNA synthesis during the seminiferous epithelium cycle, reduces sperm motility and influences the secretion of transferrin and inhibin B by Sertoli cells. Also, it has been shown that IL-6 affects tight junction permeability in Sertoli cells, but, little is known about its role in regulating the BTB. The aim of this study was to investigate the molecular mechanisms by which IL-6 affects BTB dynamics. We show that IL-6 perturbs the integrity of the BTB, and alters the normal localization and steady-state levels of BTB integral membrane proteins. We demonstrated that IL-6 regulates the BTB by inhibiting the degradation of BTB constitutive proteins and activating ERK-MAPK pathways. Our results provide mechanistic insight into the roles of IL-6 in regulating BTB dynamics.
- ALTERATIONS OF INTERCELLULAR JUNCTIONS IN PERITONEAL MESOTHELIAL CELLS FROM PATIENTS UNDERGOING DIALYSIS: EFFECT OF RETINOIC ACID. [JOURNAL ARTICLE]
- Perit Dial Int 2014 Mar 1.
Dialysis patients are classified according to their peritoneal permeability as low transporter (LT, low solute permeability) or high transporter (HT, high solute permeability). Tight junction (TJ) proteins are critical to maintain ions, molecules and water paracellular transport through peritoneum. Exposure to peritoneal dialysis solutions causes damage to TJ in human peritoneal mesothelial cells (HPMCs). We analyzed the quantity, distribution and function of TJ proteins: claudin-1, -2 and -8, ZO-1 and occludin, in HPMC cultures from LT and HT patients. Since all-trans retinoic acid (ATRA) might modify the expression of TJ proteins, we studied its effect on HPMCs. ♢ METHODS: Control HPMCs were isolated from human omentum, while HT or LT cells were obtained from dialysis effluents. Cells were cultured in presence of ATRA 0, 50 or 100 nM. Transepithelial electrical resistance (TER) measurement, immunostaining and Western blot analyses wereperformed. ♢ RESULTS: HT exhibited lower TER than control and LT monolayers. Immunofluorescence for TJ was weak and discontinuous along the cell contour, in LT and HT. Furthermore, claudin- 1, occludin and ZO-1 expressions were decreased. In all groups, claudin-2 was localized at nuclei. We observed that ATRA improved TJ distribution and increased TJ expression in HT. This retinoid did not modify claudin-2 and -8 expressions. All-trans retinoic acid decreased TER in HT, but had no effect in LT. ♢ CONCLUSIONS: Tight junctions were altered in HPMCs from dialyzed patients. The HT monolayer has lower TER than LT, which might be associated with the peritoneal permeability in these patients. ATRA might be a therapeutic alternative to maintain mesothelial integrity, since it improved TJ localization and expression.
- Berberine ameliorates severe acute pancreatitis‑induced intestinal barrier dysfunction via a myosin light chain phosphorylation‑dependent pathway. [JOURNAL ARTICLE]
- Mol Med Rep 2014 Feb 28.
Berberine is a traditional drug used to treat gastrointestinal disorders in China and has been demonstrated to attenuate intestinal barrier dysfunction in certain animal models. However, the effects of berberine on pancreatitis‑induced intestinal barrier dysfunction are yet to be fully elucidated. This study aimed to investigate the effect of berberine pretreatment on the attenuation of intestinal barrier dysfunction induced by severe acute pancreatitis (SAP). A total of 36 rats were randomly divided into Sham, SAP and SAP plus berberine groups. Pancreatitis was induced using retrograde injection of 3% Na‑taurocholate into the pancreatic duct. Histological examinations of the pancreas were performed and intestinal barrier dysfunction was characterized by histological measurements and the assessment of serum diamine oxidase activity and endotoxin levels. Zonula occludens‑1 and occludin mRNA and protein expression, as well as myosin light chain (MLC) phosphorylation, were assessed. SAP rat models were successfully established. Berberine treatment was found to have no significant effect on the histological changes in the pancreas, but was observed to ameliorate the intestinal mucosal barrier damage and membrane permeability associated with SAP. Although berberine exerted minimal effects on tight junction proteins in the ilea of SAP rats, it was observed to significantly inhibit SAP‑induced MLC phosphorylation. To the best of our knowledge, this is the first study to demonstrate that berberine attenuates SAP‑induced intestinal barrier dysfunction in vivo. In addition, this study shows that the effect of berberine on intestinal barrier function may be associated with the inhibition of SAP‑induced upregulation of MLC phosphorylation.
- Astrocytic laminin regulates pericyte differentiation and maintains blood brain barrier integrity. [Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't]
- Nat Commun 2014.:3413.
Blood brain barrier (BBB) breakdown is not only a consequence of but also contributes to many neurological disorders, including stroke and Alzheimer's disease. How the basement membrane (BM) contributes to the normal functioning of the BBB remains elusive. Here we use conditional knockout mice and an acute adenovirus-mediated knockdown model to show that lack of astrocytic laminin, a brain-specific BM component, induces BBB breakdown. Using functional blocking antibody and RNAi, we further demonstrate that astrocytic laminin, by binding to integrin α2 receptor, prevents pericyte differentiation from the BBB-stabilizing resting stage to the BBB-disrupting contractile stage, and thus maintains the integrity of BBB. Additionally, loss of astrocytic laminin decreases aquaporin-4 (AQP4) and tight junction protein expression. Altogether, we report a critical role for astrocytic laminin in BBB regulation and pericyte differentiation. These results indicate that astrocytic laminin maintains the integrity of BBB through, at least in part, regulation of pericyte differentiation.
- In Silico Analysis and Validation of the Proliferative Potential of CLDN1 Expression in Gastric Cancer. [Journal Article]
- J Environ Pathol Toxicol Oncol 2013; 32(4):343-60.
Tight junction protein claudin-1 (CLDN1) is mainly involved in the intercellular barrier function of epithelial cells and is known to be dysregulated in many cancer types, including gastrointestinal cancers. However, the mechanisms behind their potential involvement in the proliferation and survival of tumor cells remain unexplored. In this study we sought to investigate the potential role and possible regulators of CLDN1 in gastric cancer. By analyzing the gastric tumors from publicly available genome-wide messenger RNA expression profiles, CLDN1 was identified to be overexpressed in gastric tumors when compared with normal gastric tissues. Association between CLDN1 expression and clinical molecular subtype characteristics of gastric cancer showed an elevated CLDN1 expression pattern in intestinal and proliferative types of gastric cancer. Using in vitro CLDN1 perturbation analysis in gastric cancer cell lines, we confirmed the potential role of CLDN1 in cellular proliferation. Aided by the integrative analysis of the pathway prediction method with CLDN1 expression in gastric tumors, we demonstrated the negative association between estrogen-α and CLDN1 expression in gastric tumors. Our results highlight the potential involvement of CLDN1 expression in gastric cancer.
- Applications of a 7-day Caco-2 cell model in drug discovery and development. [JOURNAL ARTICLE]
- Eur J Pharm Sci 2014 Feb 24.
Oral delivery is the preferred route of administration and therefore good absorption after oral dosing is a prerequisite for a compound to be successful in the clinic. The prediction of oral bioavailability from in vitro permeability assays is thus a valuable tool during drug discovery and development. Caco-2 cell monolayers mimic the human intestinal epithelium in many aspects. These monolayers form tight junctions between cells and have been widely used as a model of human intestinal absorption. Caco-2 cells also express a variety of transporter proteins although the transformed nature of the cells results in unpredictable differentiation markers, transport properties and enzyme expression. Thus various modifications of the Caco-2 assay are used in laboratories across the globe. The purpose of this paper is to provide an overview of a time and resource saving 7-day Caco-2 assay protocol. We also discuss the impact of various experimental conditions on permeability measurements and its applications during lead optimization in early discovery and for clinical candidate characterization, specifically for prediction of absorption in human, at a later stage in drug development.
- Leukocyte infiltration into spinal cord of EAE mice is attenuated by removal of endothelial leptin signaling. [JOURNAL ARTICLE]
- Brain Behav Immun 2014 Feb 24.
Leptin, a pleiotropic adipokine, crosses the brain-brain barrier (BBB) and blood-spinal cord barrier (BSCB) from the periphery and facilitates experimental autoimmune encephalomyelitis (EAE). EAE induces dynamic changes of leptin receptors in enriched brain and spinal cord microvessels, leading to further questions about the potential roles of endothelial leptin signaling in EAE progression. In endothelial leptin receptor specific knockout (ELKO) mice, there were lower EAE behavioral scores in the early phase of the disorder, better preserved BSCB function shown by reduced uptake of sodium fluorescein and leukocyte infiltration into the spinal cord. Flow cytometry showed that the ELKO mutation decreased the number of CD3 and CD45 cells in the spinal cord, although immune cell profiles in peripheral organs were unchanged. Not only were CD4(+) and CD8(+) T lymphocytes reduced, there were also lower numbers of CD11b(+)Gr1(+) granulocytes in the spinal cord of ELKO mice. In enriched microvessels from the spinal cord of the ELKO mice, the decreased expression of mRNAs for a few tight junction proteins was less pronounced in ELKO than WT mice, as was the elevation of mRNA for CCL5, CXCL9, IFN-γ, and TNF-α. Altogether, ELKO mice show reduced inflammation at the level of the BSCB, less leukocyte infiltration, and better preserved tight junction protein expression and BBB function than WT mice after EAE. Although leptin concentrations were high in ELKO mice and microvascular leptin receptors show an initial elevation before inhibition during the course of EAE, removal of leptin signaling helped to reduce disease burden. We conclude that endothelial leptin signaling exacerbates BBB dysfunction to worsen EAE.