Biomedical subjects

Hideki Chiba

Publications and source records attributed to Hideki Chiba.

At least 19 recordsLinked to original sources

PubMed2006

The nuclear receptor hepatocyte nuclear factor 4alpha acts as a morphogen to induce the formation of microvilli.

Microvilli are actin-based organelles found on apical plasma membranes that are involved in nutrient uptake and signal transduction. Numerous components, including ezrin/radixin/moesin (ERM) proteins, have been identified that link filamentous actins to transmembrane proteins, but the signals driving microvillus biogenesis are not known. In this study, we show that the conditional and/or ectopic expression of a nuclear receptor, hepatocyte nuclear factor 4alpha (HNF4alpha), triggers microvillus morphogenesis. We also demonstrate that HNF4alpha expression induces ERM-binding phosphoprotein 50 (EBP50) expression and that attenuation of EBP50 using RNA interference inhibits microvillus development. We conclude that HNF4alpha acts as a morphogen to trigger microvillus formation.

Animals↗

PubMed2006

Cellular retinoic acid bioavailability determines epithelial integrity: Role of retinoic acid receptor alpha agonists in colitis.

The epithelial barrier is determined primarily by intercellular tight junctions (TJs). We have demonstrated previously that all-trans retinoic acid (atRA) plays an important role in forming functional TJs through a specific retinoic acid receptor (RAR)/retinoid X receptor heterodimer in epithelial cells. However, the physiological relevance of retinoic acids (RAs) in maintaining the epithelial integrity remains to be examined. Here, we show that several types of RA, including atRA, promote the barrier function of epithelial TJs. Conversely, RA depletion in the cells by overexpressing CYP26s, cytochrome P450 enzymes specifically involved in the metabolic inactivation of RAs, induces an increase of permeability as measured by two differently sized tracer molecules, inulin and mannitol. This RA-mediated enhancement of barrier function is potentially associated with the increased expression of TJ-associated genes such as occludin, claudin-1, claudin-4, and zonula occludens-1. We also found that RARalpha is a preferential regulator of the epithelial barrier in vitro. Studies of murine experimental colitis, which is characterized by increased gut permeability, reveal that RARalpha stimulation significantly attenuates the loss of the epithelial barrier during colitis in vivo. Our results suggest that cellular RA bioavailability determines the epithelial integrity, because it is a critical regulator for barrier protection during mucosal injuries.

Animals↗

PubMed2006

Epigenetic silencing of occludin promotes tumorigenic and metastatic properties of cancer cells via modulations of unique sets of apoptosis-associated genes.

Occludin is the first identified integral protein for the tight junction (TJ), and its long COOH-terminal domain is considered to have functions in receiving and transmitting cell survival signals. Loss of TJ-associated molecules, such as occludin, has been correlated with tumor progression in carcinogenesis; however, the precise molecular mechanisms explaining its loss of expression and whether occludin expression has any effects on cancer phenotypes remain to be clarified. Here, we show that forced expression of occludin in cancer cells exhibits enhanced sensitivity to differently acting apoptogenic factors, and thus inhibits the tumorigenicity of transformed cells, via modulation of unique sets of apoptosis-associated genes. In addition, studies using deletion mutants of occludin constructs show that 44 amino acids at the COOH-terminal end play a critical role in modifying the cellular phenotypes. Interestingly, occludin decreases cellular invasiveness and motility, thereby abrogating metastatic potencies of cancer cells. We also found that occludin expression is silenced by CpG island hypermethylation on its promoter region. Synergy with a demethylator and histone deacetylase inhibitor or retinoids that stimulate retinoic acid receptor alpha induces endogenous occludin, which is sufficient for apoptotic sensitization. Our results show the functional diversity of occludin and suggest that methylator phenotype of occludin provides enhanced tumorigenic, invasive, and metastatic properties of cancer cells, identifying occludin as a likely candidate for a tumor-suppressor gene in certain types of cancer.

Animals↗

PubMed2006

Connexin 26 expression prevents down-regulation of barrier and fence functions of tight junctions by Na+/K+-ATPase inhibitor ouabain in human airway epithelial cell line Calu-3.

Gap junctions are considered to play a crucial role in differentiation of epithelial cells and to be associated with tight junction proteins. In this study, to investigate the role of gap junctions in regulation of the barrier function and fence function on the tight junctions, we introduced the Cx26 gene into human airway epithelial cell line Clau-3 and used a disruption model of tight junctions employing the Na(+)/K(+)-ATPase inhibitor ouabain. In parental Calu-3 cells, gap junction proteins Cx32 and Cx43, but not Cx26, and tight junction proteins occludin, JAM-1, ZO-1, claudin-1, -2, -3, -4, -5, -6, -7, -8, -9, and -14 were detected by RT-PCR. The barrier function and fence function of tight junctions were well maintained, whereas the GJIC was low level. Treatment with ouabain caused disruption of the barrier function and fence function of tight junctions together with down-regulation of occludin, JAM-1, claudin-2, and -4 and up-regulation of ZO-1 and claudin-14. In Cx26 transfectants, Cx26 protein was detected by Western blotting and immunocytochemistry, and many gap junction plaques were observed with well-developed tight junction strands. Expression of claudin-14 was significantly increased in Cx26 transfectants compared to parental cells, and in some cells, Cx26 was co-localized with claudin-14. Interestingly, transfection with Cx26 prevented disruption of both functions of tight junctions by treatment with ouabain without changes in the tight junction proteins. Pretreatment with the GJIC blockers 18beta-glycyrrhetinic acid and oleamide did not affect the changes induced by Cx26 transfection. These results suggest that Cx26 expression, but not the mediated intercellular communication, may regulate tight junction barrier and fence functions in human airway epithelial cell line Calu-3.

Base Sequence↗

PubMed2006

Differential expression and subcellular localization of claudin-7, -8, -12, -13, and -15 along the mouse intestine.

Among tight-junction proteins, claudins, which play a key role in paracellular transport across epithelia, claudins 1 to 5 are expressed in the intestine, and changes in their abundance and/or distribution are considered to contribute to various gastrointestinal diseases. We investigated, by reverse transcription-PCR, immunoblot, and immunofluorescence analyses, which other claudin species were expressed in the mouse intestine, and whether they showed unique expression profiles. Rabbit polyclonal antibodies against mouse claudin-8, claudin-12, and claudin-15 were generated, and their specificity was verified by immunoblotting using COS-7 cells transfected with individual claudin cDNAs. Claudin-7, -8, -12, -13, and -15 appeared to be expressed in the duodenum, jejunum, ileum, and/or colon with remarkable variations in the expression levels along the intestinal tract, and had distinct subcellular localization in the intestinal epithelium. In addition, claudin-13 and -15 exhibited gradients along the crypt-surface axis of the colon. By contrast, claudin-6, -9, -10, -11, -14, -16, -18, and -19 were not observed in the intestine. Our results indicate that five additional species of claudins have very complex expression patterns along and within the intestine, and that this may reflect differences in paracellular permeable properties, providing valuable resources for studying the significance of these claudins in gastrointestinal disorders. This manuscript contains online supplemental material available at http://www.jhc.org. Please visit this article online to view these materials.

Animals↗

PubMed2006

The significance of interferon-gamma-triggered internalization of tight-junction proteins in inflammatory bowel disease.

Disruption of the epithelial barrier function of tight junctions by the proinflammatory cytokine interferon (IFN)-gamma plays a fundamental role in the pathogenesis of inflammatory bowel disease and other gastrointestinal disorders, but its precise mechanism has not been established. This Perspective provides an overview of how IFN-gamma triggers barrier dysfunction and bacterial translocation in intestinal epithelial cells, and highlights the roles of internalization of tight-junction transmembrane proteins, as well as rearrangements of the cortical actin cytoskeleton, in intestinal inflammation.

Animals↗

PubMed2006

Possible involvement of gap junctions in the barrier function of tight junctions of brain and lung endothelial cells.

Gap-junction plaques are often observed with tight-junction strands of vascular endothelial cells but the molecular interaction and functional relationships between these two junctions remain obscure. We herein show that gap-junction proteins connexin40 (Cx40) and Cx43 are colocalized and coprecipitated with tight-junction molecules occludin, claudin-5, and ZO-1 in porcine blood-brain barrier (BBB) endothelial cells. Gap junction blockers 18beta-glycyrrhetinic acid (18beta-GA) and oleamide (OA) did not influence expression of Cx40, Cx43, occludin, claudin-5, junctional adhesion molecule (JAM)-A, JAM-B, JAM-C, or ZO-1, or their subcellular localization in the porcine BBB endothelial cells. In contrast, these gap-junction blocking agents inhibited the barrier function of tight junctions in cells, determined by measurement of transendothelial electrical resistance and paracellular flux of mannitol and inulin. 18beta-GA also significantly reduced the barrier property in rat lung endothelial (RLE) cells expressing doxycycline-induced claudin-1, but did not change the interaction between Cx43 and either claudin-1 or ZO-1, nor their expression levels or subcellular distribution. These findings suggest that Cx40- and/or Cx43-based gap junctions might be required to maintain the endothelial barrier function without altering the expression and localization of the tight-junction components analyzed.

Animals↗

PubMed2006

Reduced expression of claudin-7 correlates with invasion and metastasis in squamous cell carcinoma of the esophagus.

Claudins are transmembrane proteins that seal tight junctions, bind with peripheral protein zonula occludens (ZO)-1, and are known to play an important role in several normal tissues and cancers. However, the role of claudin-1 and claudin-7 expressions in esophageal squamous cell carcinoma remains to be clarified. In the present study, we confirmed the expressions of claudin-1, claudin-7, and ZO-1 in the prickle cell layer of the normal human esophageal squamous epithelium. The expressions of claudin-1 and claudin-7 at the invasive front of the esophageal squamous cell carcinoma were analyzed immunohistochemically to clarify their role in tumor progression. Reduced expression of claudin-7 at the invasive front of the esophageal cancer was significantly associated with the depth of invasion (P = .004), stage (P = .038), lymphatic vessel invasion (P = .001), and lymph node metastasis (P = .014). In contrast, significant association was not detected between claudin-1 expression and clinicopathologic factors except for histologic differentiation of the tumor (P = .0029). Comparison of claudin-7 expression at the invasive front of the primary tumor and its corresponding metastatic lymph nodes revealed significant reduction in claudin-7 expression in the metastatic lymph nodes (P = .007). These results suggest that the reduced expression of claudin-7 at the invasive front of esophageal squamous cell carcinoma may lead to tumor progression and subsequent metastatic events. Thus, claudin-7 can be a novel marker for the prediction of lymph node metastasis.

Aged↗

PubMed2005

Phosphorylation of ezrin enhances microvillus length via a p38 MAP-kinase pathway in an immortalized mouse hepatic cell line.

The apical microvilli are closely related with the development and the maintenance of cell polarization, and the length of microvilli varies in a regular way among cell types. Ezrin, a member of the ezrin/radixin/moesin (ERM) family, seems to be involved in the formation and stabilization of the apical microvilli. We found that phosphorylation of ezrin caused elongation of microvilli via a p38 MAP-kinase signaling pathway in an immortalized mouse hepatic cell line. When, in the oncogenic Raf-1-transfected mouse hepatic cell line, epithelial to mesenchymal transition (EMT) indicated as down-regulation of E-cadherin and up-regulation of Snail occurred, loss of microvilli and down-regulation of ezrin but not radixin and moesin were also observed. In the Raf-1 transfectants treated with the MAP-kinase inhibitor PD98059 and the p38 MAP-kinase inhibitor SB203580, the numbers of microvilli and the expression of ezrin, E-cadherin and Snail were recovered. More interestingly, treatment with SB203580 induced elongation of microvilli and increased phosphorylation of ezrin (at Thr-567 and Tyr-353). Phosphorylated ezrin-positive dots were colocalized with actin-positive dots on the surface of some Raf-1 transfectants treated with SB203580. These results suggested that phosphorylation of ezrin via the p38 MAP-kinase signaling pathway might be involved in the formation of microvilli during development of epithelial cell polarization.

Acrylates↗

PubMed2005

Hyperstimulation and a gonadotropin-releasing hormone agonist modulate ovarian vascular permeability by altering expression of the tight junction protein claudin-5.

We investigated the mechanism by which a GnRH agonist (GnRHa) affects ovarian vascularity, vascular permeability, and expression of the tight junction protein claudin-5 in a rat model of ovarian hyperstimulation syndrome (OHSS). Hyperstimulated rats received excessive doses of pregnant mare serum gonadotropin (PMSG; 50 IU/d) for 4 consecutive days, from d 25 to 28 of life, followed by 25 IU human chorionic gonadotropin (hCG) on d 29. Control rats received 10 IU PMSG on d 27 of life, followed by 10 IU hCG on d 29. GnRHa (leuprolide 100 microg/kg.d) was administered to some hyperstimulated rats either on d 29 and 30 (short-term GnRHa treatment) or from d 25 to 30 (long-term GnRHa treatment). Ovarian vascular density (vessels per 10 mm(2)) and vessel endothelial area (percent) were assessed by immunohistochemical analysis of the distribution of von Willebrand factor, whereas vascular permeability was evaluated based on leakage of Evans blue. High doses of PMSG and hCG significantly increased ovarian weight, vascular permeability, vascular density, and the vessel endothelial area and significantly reduced expression of claudin-5 protein and mRNA. All of these effects were significantly and dose-dependently inhibited by administration of GnRHa. This suggests that reduced expression of claudin-5 plays a crucial role in the increased ovarian vascular permeability seen in OHSS and that its expression can be modulated by GnRHa treatment. Indeed, preventing redistribution of tight junction proteins in endothelial cells and the resultant loss of endothelial barrier architecture might be the key to protecting patients against massive extravascular fluid accumulation in cases of OHSS.

Analysis of Variance↗

PubMed2005

Behavior of tight-junction, adherens-junction and cell polarity proteins during HNF-4alpha-induced epithelial polarization.

We previously reported that expression of tight-junction molecules occludin, claudin-6 and claudin-7, as well as establishment of epithelial polarity, was triggered in mouse F9 cells expressing hepatocyte nuclear factor (HNF)-4alpha [H. Chiba, T. Gotoh, T. Kojima, S. Satohisa, K. Kikuchi, M. Osanai, N. Sawada. Hepatocyte nuclear factor (HNF)-4alpha triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells, Exp. Cell Res. 286 (2003) 288-297]. Using these cells, we examined in the present study behavior of tight-junction, adherens-junction and cell polarity proteins and elucidated the molecular mechanism behind HNF-4alpha-initiated junction formation and epithelial polarization. We herein show that not only ZO-1 and ZO-2, but also ZO-3, junctional adhesion molecule (JAM)-B, JAM-C and cell polarity proteins PAR-3, PAR-6 and atypical protein kinase C (aPKC) accumulate at primordial adherens junctions in undifferentiated F9 cells. In contrast, CRB3, Pals1 and PATJ appeared to exhibit distinct subcellular localization in immature cells. Induced expression of HNF-4alpha led to translocation of these tight-junction and cell polarity proteins to beltlike tight junctions, where occludin, claudin-6 and claudin-7 were assembled, in differentiated cells. Interestingly, PAR-6, aPKC, CRB3 and Pals1, but not PAR-3 or PATJ, were also concentrated on the apical membranes in differentiated cells. These findings indicate that HNF-4alpha provokes not only expression of tight-junction adhesion molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization.

Adherens Junctions↗

PubMed2005

Down-regulation of survival signaling through MAPK and Akt in occludin-deficient mouse hepatocytes in vitro.

The tight junction (TJ) regulates epithelial cell polarity and barrier including permeability of the paracellular pathway. Occludin was the first integral membrane protein to be discovered, but it is not indispensable for the formation of TJ strands. The physiological function of occludin is still unclear, although occludin-deficient mice show very complex abnormalities in various organs without overt dysfunction of the TJ. To investigate the role of occludin in TJ expression and apoptosis regulated by survival signal transduction pathways such as MAPK and Akt, we performed primary culture of hepatocytes and established hepatic cell lines from occludin-deficient mice. In primary cultures of occludin-deficient mouse hepatocytes, claudin-2 expression and apoptosis were induced by down-regulation of the activation of MAPK and Akt. In the hepatic cell lines derived from occludin-deficient mice, claudin-2 expression and serum-free induced apoptosis were also increased by down-regulation of the activation of MAPK and Akt. Furthermore, in the hepatic cell lines transiently transfected with mouse and rat occludin genes, induction of claudin-2 expression and the apoptosis were inhibited with increases in activation of MAPK and Akt. These findings show that occludin plays a crucial role in claudin-2-dependent TJ function and the apoptosis involving MAPK and Akt signaling pathways in hepatocytes.

Animals↗

PubMed2005

Glyceraldehyde-derived advanced glycation end-products preferentially induce VEGF expression and reduce GDNF expression in human astrocytes.

The blood-brain barrier (BBB) is a biological unit composed of capillary endothelial cells and astrocytes. Here we examined the effects of various types of advanced glycation end-products (AGEs) on astrocytes and BBB-forming endothelial cells. While no type of AGE we examined changed the permeability of endothelial sheets, glyceraldehyde-derived AGE induced VEGF expression most significantly in astrocytes. The expression of glial cell line-derived neurotrophic factor (GDNF), which reduces the vascular permeability, was decreased in the astrocytes by treatment with glyceraldehyde-derived AGE. These results indicate that glyceraldehyde-derived AGE is the biologically active substance for astrocytes by regulating the VEGF and GDNF expression, which is causally contributing to an increase in the permeability of the BBB.

Astrocytes↗

PubMed2005

Activation of p21CIP1/WAF1 gene expression and inhibition of cell proliferation by overexpression of hepatocyte nuclear factor-4alpha.

The F9 murine embryonal carcinoma cell line provides an attractive system for studying epithelial differentiation and antiproliferative processes. We have recently established F9 cells expressing doxycycline-inducible hepatocyte nuclear factor (HNF)-4alpha and shown that HNF-4alpha triggers the gene expression of tight-junction molecules, occludin, claudin-6, and claudin-7, as well as formation of functional tight junctions and polarized epithelial morphology (Exp. Cell Res. 286, [2003] 288). Since these events were very similar to those induced by retinoids, we investigated whether HNF-4alpha, like retinoid receptors, was involved in the control of cell proliferation. We herein show that HNF-4alpha up-regulates expression of the p21 gene, but not the p15, p16, p18, p19, or p27 gene, in a p53-independent manner, and inhibits cell growth in F9 cells. Similar results were observed in rat lung endothelial cells, in which expression of HNF-4alpha is conditionally induced by doxycycline. Furthermore, we demonstrate, by reporter assay, that HNF-4alpha significantly elevates the transcriptional activity of the p21 promoter. Since, HNF-4alpha is expressed not only in the liver but also in organs containing epithelial cells, such as kidney, intestine, pancreas, and stomach, it might also play critical roles in the regulation of epithelial morphogenesis and proliferation in these organs.

Animals↗

PubMed2005

p38 MAP-kinase regulates function of gap and tight junctions during regeneration of rat hepatocytes.

BACKGROUND/AIMS: Hepatocyte regeneration is considered to be associated with adaptive changes in expression of gap and tight junctions through multiple signal transduction pathways including p38 MAP-kinase. The role of the stress responsitive MAP-kinase, p38 MAP-kinase, signaling pathway in function of gap and tight junctions was examined during regeneration of rat hepatocytes in vivo and in vitro. METHODS: We examined changes in formation, expression and function of gap and tight junctions in rat livers after 70% partial hepatectomy and in primary cultures of rat hepatocytes, by using a p38 MAP-kinase inhibitor, SB203580. RESULTS: When p38 MAP-kinase was activated during partial hepatectomy, down-regulation of Cx32 and up-regulation of claudin-1 were observed. By SB203580 treatment, the down-regulation of Cx32 was inhibited and the up-regulation of claudin-1 was enhanced, well maintaining the structures of gap and tight junctions. SB203580 treatment did not affect the increase of hepatocyte proliferation. In EGF induced proliferative rat hepatocytes treated with SB203580, the expression and function of Cx32 and claudin-1 were increased. CONCLUSIONS: Dynamic changes of formation of gap and tight junctions during regeneration of rat hepatocytes in vivo and in vitro are in part controlled via a p38 MAP-kinase signaling pathway, and are independent of cell growth.

Animals↗

PubMed2004

Tight junction protein MAGI-1 is up-regulated by transfection with connexin 32 in an immortalized mouse hepatic cell line: cDNA microarray analysis.

Gap junctions are considered to play a crucial role in differentiation of epithelial cells, including hepatocytes. Recently, we found that Cx32 but not Cx26 was closely related to tight junctional proteins in primary cultured rat hepatocytes (Kojima et al., Exp Cell Res 263:193-201, 2001) and that Cx32 formation and/or Cx32-mediated intercellular communication could induce expression and function of tight junctions in a mouse hepatic cell line (Kojima et al., Exp Cell Res 276:40-51, 2002). In this study, to investigate the mechanisms of induction of tight junctions by transfection with Cx32, we performed cDNA microarray analysis of Cx32 transfectants, compared with parental cells derived from Cx32-deficient hepatocytes. In cDNA microarray analysis, a 2.5-fold increase in expression of membrane-associated guanylate kinase with inverted orientation-1 (MAGI-1), which is known to be localized at adherens and tight junction regions, was observed. High expression of MAGI-1 in Cx32 transfectants was confirmed by Western blotting and RT-PCR. MAGI-1 was colocalized with occludin, claudin-2, ZO-1, and F-actin, but not with E-cadherin in the apical-most regions at cell borders of Cx32 transfectants, similar to junctional adhesion molecule-1 (JAM-1), which may play a crucial role in formation and assembly of tight junctions. Treatment with the gap junction blocker 18beta-glycyrrhetinic acid did not affect expression of MAGI-1 and JAM-1 in Cx32 transfectants. These results suggest that Cx32 expression is in part related to induction of tight junctions through modulation of MAGI-1 expression in an immortalized mouse hepatic cell line.

Actins↗

PubMed2004

Thr(207) of claudin-5 is involved in size-selective loosening of the endothelial barrier by cyclic AMP.

We have recently shown that cyclic AMP (cAMP) increases claudin-5 immunoreactivity along cell boundaries and could promote phosphorylation of claudin-5 on threonine residues in porcine blood-brain barrier (BBB) endothelial cells via a protein kinase A (PKA)-dependent pathway (Exp. Cell Res. 290 [2003] 275). Along this line, we identified a putative phosphorylation site for PKA at Thr(207) in the intracytoplasmic carboxyl terminal domain of claudin-5. To clarify the biological significance of this site in regulation of endothelial barrier functions, we established rat lung endothelial (RLE) cells expressing doxycycline (Dox)-inducible wild-type claudin-5 and a mutant with a substitution of Ala for Thr(207) (CL5T207A). We show that induction of wild-type claudin-5 is sufficient to reconstitute the paracellular barrier against inulin (5 kDa), but not mannitol (182 Da), in leaky RLE cells. By contrast, the barrier against both molecules was induced in the mutant cells. We also demonstrate that, upon cAMP treatment, Thr(207) of claudin-5 is involved in enhancement of claudin-5 immunoreactive signals along cell borders, rapid reduction in transendothelial electrical resistance (TER), and loosening of the claudin-5-based endothelial barrier against mannitol, but not inulin. cAMP decreased the claudin-5-based endothelial barrier, strongly suggesting that other tight-junction molecule(s) are required to elevate endothelial barrier functions in response to cAMP.

Alanine↗

PubMed2004

IL-1beta regulates expression of Cx32, occludin, and claudin-2 of rat hepatocytes via distinct signal transduction pathways.

The functions of gap and tight junctions are perturbed during the acute-phase response to liver injury. To elucidate the mechanism of pro-inflammatory cytokine IL-1beta responsible for regulation of hepatic gap and tight junctions, we analyzed expression and function of gap and tight junctions using a rat liver injury model and primary cultures of rat hepatocyte. In rat liver lobules at 24 h after thioacetamide (TAA) treatment, where some IL-1beta-positive non-parenchymal cells existed, disappearance of connexin32-positive spots at cell borders of the hepatocytes and increases of claudin-2 and occludin immunoreactivities in bile canalicular regions were observed. In primary cultures of rat hepatocytes, IL-1beta caused the disappearance of connexin32, which was reciprocal to the induction and localization of claudin-2 to cell membranes. The downregulated connexin32 expression was inhibited by treatment with a MAP-kinase inhibitor (PD98059), whereas the upregulated claudin-2 expression was blocked by p38 MAP and PI3-kinase inhibitors (SB203580 and LY294002). The changes of connexin32 and claudin-2 may be controlled at the transcriptional level via NF-kappaB, HNF-1alpha, and CDX2. Occludin was hyperphosphorylated by IL-1beta treatment and was inhibited by treatment with a PI3-kinase inhibitor. These results demonstrate that MAP-kinase, p38 MAP-kinase, and PI3-kinase are distinctly involved in the regulation of hepatic gap and tight junctions during the acute-phase response to IL-1beta.

Animals↗