• Journal of Life Science
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• v.26 no.5
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• pp.531-536
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• 2016

We previously showed that NAD(P)H:quinone oxidoreductase 1 (NQO1) knockout (KO) mice exhibited spontaneous inflammation with markedly increased mucosal permeability in the gut, and that NQO1 is functionally associated with regulating tight junctions in the mucosal epithelial cells that govern the mucosal barrier. Here, we confirm the role of NQO1 in the formation of tight junctions by human colonic epithelial cells (HT29). We treated HT29 cells with a chemical inhibitor of NQO1 (dicumarol; 10 μM), and examined the effect on the transepithelial resistance of epithelial cells and the protein expression levels of ZO1 and occludin (two known regulators of tight junctions between gut epithelial cells). The dicumarol-induced inhibition of NQO1 markedly reduced transepithelial resistance (a measure of tight junctions) and decreased the levels of the tested tight junction proteins. In vivo, luminal injection of dicumarol significantly increased mucosal permeability and decreased ZO1 and occludin protein expression levels in mouse guts. However, in contrast to the previous report that the epithelial cells of NQO1 KO mice showed marked down-regulations of the transcripts encoding ZO1 and occludin, these transcript levels were not affected in dicumarol-treated HT29 cells. This result suggests that the NQO1-depedent regulation of tight junction molecules may involve multiple processes, including both transcriptional regulation and protein degradation processes such as those governed by the ubiquitination/proteasomal, and/or lysosomal systems.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.2
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• pp.147-152
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• 2016

Present study aimed to investigate the effect of curcumin-pretreatment on intestinal I/R injury and on intestinal mucosa barrier. Thirty Wistar rats were randomly divided into: sham, I/R, and curcumin groups (n=10). Animals in curcumin group were pretreated with curcumin by gastric gavage (200 mg/kg) for 2 days before I/R. Small intestine tissues were prepared for Haematoxylin & Eosin (H&E) staining. Serum diamine oxidase (DAO) and tumor necrosis factor (TNF)-${\alpha}$ levels were measured. Expression of intestinal TNF-${\alpha}$ and tight junction protein (ZO-1) proteins was detected by Western blot and/or immunohistochemistry. Serum DAO level and serum and intestinal TNF-${\alpha}$ leves were significantly increased after I/R, and the values were markedly reduced by curcumin pretreatment although still higher than that of sham group (p<0.05 or p<0.001). H&E staining showed the significant injury to intestinal mucosa following I/R, and curcumin pretreatment significantly improved the histological structure of intestinal mucosa. I/R insult also induced significantly down-regulated expression of ZO-1, and the effect was dramatically attenuated by curcumin-pretreatment. Curcumin may protect the intestine from I/R injury through restoration of the epithelial structure, promotion of the recovery of intestinal permeability, as well as enhancement of ZO-1 protein expression, and this effect may be partly attributed to the TNF-${\alpha}$ related pathway.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.5
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• pp.731-738
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• 2016

Glucagon-like peptide-2 (GLP-2) is important for intestinal barrier function and regulation of tight junction (TJ) proteins, but the intracellular mechanisms of action remain undefined. The purpose of this research was to determine the protective effect of GLP-2 mediated TJ and transepithelial electrical resistance (TER) in lipopolysaccharide (LPS) stressed IPEC-J2 cells and to test the hypothesis that GLP-2 regulate TJ and TER through the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway in IPEC-J2 cells. Wortmannin and LY294002 are specific inhibitors of PI3K. The results showed that $100{\mu}g/mL$ LPS stress decreased TER and TJ proteins occludin, claudin-1 and zonula occludens protein 1 (ZO-1) mRNA, proteins expressions (p<0.01) respectively. GLP-2 (100 nmol/L) promote TER and TJ proteins occludin, claudin-1, and zo-1 mRNA, proteins expressions in LPS stressed and normal IPEC-J2 cells (p<0.01) respectively. In normal cells, both wortmannin and LY294002, PI3K inhibitors, prevented the mRNA and protein expressions of Akt and mTOR increase induced by GLP-2 (p<0.01) following with the significant decreasing of occludin, claudin-1, ZO-1 mRNA and proteins expressions and TER (p<0.01). In conclusion, these results indicated that GLP-2 can promote TJ's expression and TER in LPS stressed and normal IPEC-J2 cells and GLP-2 could regulate TJ and TER through the PI3K/Akt/mTOR pathway.

• Korean Journal of Organic Agriculture
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• v.29 no.1
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• pp.125-136
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• 2021

In this study, a meta-analysis was performed to determine the correlation between the expression of tight junction protein in the intestine and the productivity of broiler chickens. A total of 9 papers were selected in which the result values consisted of the mean and standard deviation value, and the standardized mean difference was calculated to compare the mean of the control and treatment groups. A meta-regression test was conducted to determine the effect of each type of tight junction protein. The TJPs observed in each study were claudin1, claudin2, claudin3, occludin, ZO1, ZO2, etc., and the indicators to indicate the productivity of broilers were body weight gain (BWG), feed intake (FI), and feed conversion rate (FCR), average daily feed intake (ADFI), average daily gain (ADG), and feed/gain ratio (FPG). Although there are differences depending on the type of TJP, it was found that the change in expression level had a close effect on the productivity of broilers. In particular, occludin significantly correlated with body weight gain, feed intake, and feed conversion rate. Based on the results of this study, a study on a method to effectively increase the expression level of TJP is expected to contribute to improving the productivity of broilers and producing safe livestock products.

• Journal of Life Science
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• v.25 no.1
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• pp.101-112
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• 2015

A type of cell junction that is formed between different parts within the same cell is called autotypic cell junction. Autotypic junction proteins form tight junctions found between membrane lamellae of a cell, especially in myelinating glial cells. Some of them have postsynaptic density-95/disks large/zonula occludens-1 (PDZ) domains, which interact with the carboxyl (C)-terminal PDZ-binding motif of other proteins. PDZ domains are protein-protein interaction modules that play a role in protein complex assembly. The PDZ domain, which is widespread in bacteria, plants, yeast, metazoans, and Drosophila, allows the assembly of large multi-protein complexes. The multi-protein complexes act in intracellular signal transduction, protein targeting, and membrane polarization. The identified PDZ domain-containing proteins located at autotypic junctions include zonula occludens-1 (ZO-1), ZO-2, pals-1-associated tight junction protein (PATJ), multi-PDZ domain proteins (MUPPs), membrane-associated guanylate kinase inverted 2 (MAGI2), and protease-activated receptor (PAR)-3. PAR-3 interacts with atypical protein kinase C and PAR-6, forming a ternary complex, which plays an important role in the regulation of cell polarity. MAGI2 interacts with ${\alpha}$-amino-3-hydroxyl-5-methyl-4-isoxazole propionate (AMPA) receptor at excitatory synapses. PATJ is detected in paranodal loops associated with claudin-1. On the other hand, MUPP1 is found in mesaxons and Schmidt-Lanterman incisures with claudin-5. ZO-1, ZO-2, and PAR-3 are found at all three sites. Different distributions of PDZ domain-containing proteins affect the development of autotypic junctions. In this review, we will describe PDZ domain-containing proteins at autotypic tight junctions in myelinating Schwann cells and their roles.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.5
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• pp.733-742
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• 2014

The glucagon-like peptide 2 (GLP-2) that is expressed in intestine epithelial cells of mammals, is important for intestinal barrier function and regulation of tight junction (TJ) proteins. However, there is little known about the intracellular mechanisms of GLP-2 in the regulation of TJ proteins in piglets' intestinal epithelial cells. The purpose of this study is to test the hypothesis that GLP-2 regulates the expressions of TJ proteins in the mitogen-activated protein kinase (MAPK) signaling pathway in piglets' intestinal epithelial cells. The jejunal tissues were cultured in a Dulbecco's modified Eagle's medium/high glucose medium containing supplemental 0 to 100 nmol/L GLP-2. At 72 h after the treatment with the appropriate concentrations of GLP-2, the mRNA and protein expressions of zonula occludens-1 (ZO-1), occludin and claudin-1 were increased (p<0.05). U0126, an MAPK kinase inhibitor, prevented the mRNA and protein expressions of ZO-1, occludin, claudin-1 increase induced by GLP-2 (p<0.05). In conclusion, these results indicated that GLP-2 could improve the expression of TJ proteins in weaned pigs' jejunal epithelium, and the underlying mechanism may due to the MAPK signaling pathway.

• Herbal Formula Science
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• v.32 no.2
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• pp.121-128
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• 2024

Objectives : This study aimed to investigate the protective effects of mixed extracts from Scutellaria baicalensis Georgi, Alisma orientale Juzepzuk, and Atractylodes japonica Koidzumi on interleukin (IL)-6-induced damage to tight junction (TJ) integrity in a Caco-2 cell model. Methods : We assessed the TJ integrity of Caco-2 monolayers by measuring the flux of FITC-labeled dextran and transepithelial electrical resistance (TEER). Additionally, we evaluated the expression of TJ proteins, such as ZO-1 and Occludin. Results : Treatment with IL-6 (50 ng/ml) increased TJ permeability and decreased TEER values of Caco-2 monolayers. Pretreatment with HTB (50-200 ㎍/ml) for 1 h significantly alleviated IL-6-induced TJ disruption, as evidenced by reduced TJ permeability and increased TEER values. Furthermore, HTB reversed the IL-6-induced inhibition of TJ protein expression, including ZO-1 and Occludin. Conclusions : These findings indicate that HTB protects barrier function by reversing the IL-6-induced decrease in TJ integrity and the suppression of TJ protein expression.

• Journal of Animal Science and Technology
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• v.64 no.5
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• pp.842-853
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• 2022

Ochratoxin A (OTA) is a well-known mycotoxin that causes disease through the ingestion of contaminated food or feed, for example, in the porcine industry. The intestinal epithelium acts as the first barrier against food contamination. We conducted a study on the exposure of the porcine intestinal epithelium to OTA. We used the intestinal porcine epithelial cell line IPEC-J2 as an in vitro model to evaluate the altered molecular mechanisms following OTA exposure. Gene expression profiling revealed that OTA upregulated 782 genes and downregulated 896, totalling 1678 differentially expressed genes. Furthermore, immunofluorescence, quantitative real-time polymerase chain reaction, and western blotting confirmed that OTA damages the tight junction protein ZO-1. Moreover, OTA activated the expression of inflammatory genes (IL-6, IL-8, IL-10, NF-kB, TLR4, and TNF-α). In summary, this study confirmed that OTA alters various molecular mechanisms and has several adverse effects on IPEC-J2 cells.

• Journal of the Korean Applied Science and Technology
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• v.41 no.1
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• pp.58-68
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• 2024

The purpose of this study was to investigate the effects of treadmill exercise treadmill exercise (TE) and environmental enrichment (EE) interventions on cognitive function, muscle function, and the expression of tight junction proteins in an Alzheimer's disease (AD) animal model. To create the AD animal model, aluminum chloride (AlCl₃) was administered for 90 days (40mg/kg/day), while simultaneously exposing the animals to TE (10-12m/min, 40-60min/day) or EE. The results showed that cognitive impairment and muscle dysfunction induced by AlCl₃ administration were alleviated by TE and EE. Furthermore, TE and EE reduced the increased expression of β-amyloid(Aβ), alpha-synuclein, and tumor necrosis factor-α (TNF-α) proteins observed in AD pathology. Additionally, TE and EE significantly increased the expression of decreased adhesive adjacent proteins (Occludin, Claudin-5, and ZO-1) induced by AlCl₃ administration. Lastly, correlation analysis between Aβ protein and tight junction proteins showed negative correlations (Occludin: r=-0.853, p=0.001; Claudin-5: r=-0.352, p=0.915; ZO-1: r=-0.424, p=0.0390). In conclusion, TE or EE interventions are considered effective exercise methods that partially alleviate pathological features of AD, improving cognitive and muscle function.

• Journal of Life Science
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• v.17 no.9 s.89
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• pp.1298-1302
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• 2007

A hallmark of cancers is 'leaky' tight junctions (Tjs). TJs mediated paracellular permeability is elevated and TJs maintained cell polarity is frequently lost. Concomitantly, TJs-associated proteins including members of the claudin family of proteins are dysregulated. Recent findings indicate that these TJs changes can contribute to cancer progression. In this study, we examined the effects of ${\beta}-lapachone$, a quinone compound obtained from the bark of the lapacho tree (Tabebuia avellanedae), on the Tjs-associated regulators in human hepatocarcinoma cell lines, HepG2 and Hep3B. ${\beta}-lapachone$ treatment downregulated the levels of insulin-like growth factor 1 receptor (IGF-lR) proteins in both HepG2 and Hep3B cells. But the levels of claudin-3 and -4 proteins were increased in ${\beta}-lapachone$-treated HepG2 and Hep3B cells. And also the zonnula occludens-l (la-I) and p-catenin protein levels by ${\beta}-lapachone$ were increased in a time-dependent manner. However, claudin-3 and -4 mRNA levels were uninhibited by ${\beta}-lapachone$ in HepG2 and Hep3B. The present results suggest that the upregulation of claudin-3 and -4 protein levels by ${\beta}-lapachone$ occurs by a post-transcriptional mechanism and points to a novel mechanism by ${\beta}-lapachone$.