Homoharringtonine is a transdermal granular permeation enhancer.

Although modulation of claudin-1-based tight junction (TJ) in stratum granulosum is an option for transdermal absorption of drugs, granular permeation enhancers have never been developed. We previously found that homoharringtonine (HHT), a natural alkanoid, weakened intestinal epithelial barrier with changing expression and cellular localization of TJ components such as claudin-1 and claudin-4. In the present study, we investigated whether HHT is an epidermal granular permeation enhancer. Treatment of normal human epidermal keratinocytes (NHEK) cells with HHT decreased claudin-1 and claudin-4 but not zonula occludens-1 and E-cadherin. HHT lowered TJ-integrity in NHEK cells, accompanied by permeation-enhancement of dextran (4 kDa) in a dose-dependent manner. Transdermal treatment of mice with HHT weakened epidermal barrier. HHT treatment enhanced transdermal absorption of dextran with a molecular mass of up to 10 kDa. Together, HHT may be a transdermal absorption enhancer.

Rebeccamycin Attenuates TNF-α-Induced Intestinal Epithelial Barrier Dysfunction by Inhibiting Myosin Light Chain Kinase Production.

BACKGROUND/AIMS: Although proinflammatory cytokine-induced disruption of intestinal epithelial barrier integrity is associated with intestinal inflammatory disease, effective treatment for barrier dysfunction is lacking. Previously, we demonstrated that rebeccamycin alleviates epithelial barrier dysfunction induced by inflammatory cytokines in Caco-2 cell monolayers; however, the underlying mechanism remained unclear. Here, we investigated the mechanism by which rebeccamycin protects the epithelial barrier function of Caco-2 cells exposed to TNF-α. METHODS: To confirm the epithelial barrier function of Caco-2 cell monolayers, transepithelial electrical resistance (TER) and paracellular permeability were measured. Production levels and localization of tight junction (TJ) proteins were analyzed by immunoblot and immunofluorescence, respectively. Phosphorylated myosin light chain (pMLC) and MLC kinase (MLCK) mRNA expression levels were determined by immunoblot and quantitative RT-PCR, respectively. RESULTS: Rebeccamycin attenuated the TNF-α-induced reduction in TER and increase in paracellular permeability. Rebeccamycin increased claudin-5 expression, but not claudin-1, -2, -4, occludin or ZO-1 expression, and prevented the TNF-α-induced changes in ZO-1 and occludin localization. Rebeccamycin suppressed the TNF-α-induced increase in MLCK mRNA expression, thus suppressing MLC phosphorylation. The rebeccamycin-mediated reduction in MLCK production and protection of epithelial barrier function were alleviated by Chk1 inhibition. CONCLUSION: Rebeccamycin attenuates TNF-α-induced disruption of intestinal epithelial barrier integrity by inducing claudin-5 expression and suppressing MLCK production via Chk1 activation.

Claudin-5-Binders Enhance Permeation of Solutes across the Blood-Brain Barrier in a Mammalian Model.

A current bottleneck in the development of central nervous system (CNS) drugs is the lack of drug delivery systems targeting the CNS. The intercellular space between endothelial cells of the blood-brain barrier (BBB) is sealed by complex protein-based structures called tight junctions (TJs). Claudin-5 (CLDN-5), a tetra-transmembrane protein is a key component of the TJ seal that prevents the paracellular diffusion of drugs into the CNS. In the present study, to investigate whether CLDN-5 binders can be used for delivery of drugs to the CNS, we generated monoclonal antibodies (mAbs) specific to the extracellular domains of CLDN-5. In an in vitro model of the BBB, the anti-CLDN-5 mAbs attenuated trans-epithelial/endothelial electrical resistance and enhanced solute permeation. These anti-CLDN-5 mAbs are potential leads for the development of novel drug delivery systems targeting the CNS.

Creation of a Claudin-2 Binder and Its Tight Junction-Modulating Activity in a Human Intestinal Model.

Disruption of the gastrointestinal epithelial barrier is a hallmark of chronic inflammatory bowel diseases (IBDs). The transmembrane protein claudin 2 (CLDN2) is a component of epithelial tight junctions (TJs). In the intestines of patients with IBDs, the expression of the pore-forming TJ protein CLDN2 is upregulated. Although CLDN2 is involved in these leaky barriers, whether it can be a target to enhance TJ integrity is unknown because a CLDN2-specific inhibitor has not been developed. Here, we used DNA immunization to generate a monoclonal antibody (mAb) that recognized an extracellular loop of CLDN2. Treatment of epithelial cell monolayers with the mAb increased barrier integrity. In addition, the anti-CLDN2 mAb attenuated the decrease in TJ integrity induced by the proinflammatory cytokine tumor necrosis factor-α (TNF-α), and cotreatment of cells with anti-TNF-α mAb and anti-CLDN2 mAb showed additive attenuating effects. These findings indicate that CLDN2 may be a target for enhancing TJ integrity, and CLDN2 binder may be an enhancer of mucosal barrier integrity and a potential therapeutic option for IBDs.

Generation and characterization of a human-mouse chimeric antibody against the extracellular domain of claudin-1 for cancer therapy using a mouse model.

Claudin-1 (CLDN-1), an integral transmembrane protein, is an attractive target for drug absorption, prevention of infection, and cancer therapy. Previously, we generated mouse anti-CLDN-1 monoclonal antibodies (mAbs) and found that they enhanced epidermal absorption of a drug and prevented hepatitis C virus infection in human hepatocytes. Here, we investigated anti-tumor activity of a human-mouse chimeric IgG1, xi-3A2, from one of the anti-CLDN-1 mAbs, clone 3A2. Xi-3A2 accumulated in the tumor tissues in mice bearing with human CLDN-1-expressing tumor cells. Xi-3A2 activated Fcγ receptor IIIa-expressing reporter cells in the presence of human CLDN-1-expressing cells, suggesting xi-3A2 has a potential to exhibit antibody-dependent cellular cytotoxicity against CLDN-1 expressing tumor cells. We also constructed a mutant xi-3A2 antibody with Gly, Ser, and Ile substituted with Ala, Asp, and Arg at positions 236, 239, and 332 of the Fc domain. This mutant antibody showed greater activation of Fcγ receptor IIIa and in vivo anti-tumor activity in mice bearing human CLDN-1-expressing tumors than xi-3A2 did. These findings indicate that the G236A/S239D/I332E mutant of xi-3A2 might be a promising lead for tumor therapy.

Anti-HCV effect of Lentinula edodes mycelia solid culture extracts and low-molecular-weight lignin.

Lentinula edodes mycelia solid culture extract (MSCE) contains several bioactive molecules, including some polyphenolic compounds, which exert immunomodulatory, antitumor, and hepatoprotective effects. In this study, we examined the anti-hepatitis C virus (HCV) activity of MSCE and low-molecular-weight lignin (LM-lignin), which is the active component responsible for the hepatoprotective effect of MSCE. Both MSCE and LM-lignin inhibited the entry of two HCV pseudovirus (HCVpv) types into Huh7.5.1 cells. LM-lignin inhibited HCVpv entry at a lower concentration than MSCE and inhibited the entry of HCV particles in cell culture (HCVcc). MSCE also inhibited HCV subgenome replication. LM-lignin had no effect on HCV replication, suggesting that MSCE contains additional active substances. We demonstrate here for the first time the anti-HCV effects of plant-derived LM-lignin and MSCE. The hepatoprotective effect of LM-lignin suggests that lignin derivatives, which can be produced in abundance from existing plant resources, may be effective in the treatment of HCV-related diseases.

Claudin-1 Binder Enhances Epidermal Permeability in a Human Keratinocyte Model.

Tight junctions (TJs) are complex biochemical structures that seal the intercellular space and prevent the free movement of solutes across epithelial cell sheets. Modulating the TJ seal is a promising option for increasing the transdermal absorption of drugs. Within TJs, the binding of the claudin (CLDN) family of tetratransmembrane proteins through cis- and trans-interactions is an integral part of seal formation. Because epidermal TJs contain CLDN-1 and CLDN-4, a binder for these CLDNs may be a useful modulator of the permeability of the epidermal barrier. Here, we investigated whether m19, which can bind to CLDN-1/-4 (also CLDN-2/-5), modulates the integrity of epidermal TJs and the permeability of cell sheets to solutes. Treatment of normal human epidermal keratinocytes (NHEKs) with the CLDN binder reduced the integrity of TJs. A CLDN-1-specific binder (a monoclonal antibody, clone 7A5) also weakened the TJ seal in NHEKs. Although m19 attenuated the TJ barrier in human intestinal epithelial cells (Caco-2), 7A5 did not. Treatment of NHEKs with 7A5 enhanced permeation of a paracellular permeation marker. These findings indicate that CLDN-1 is a potential target for modulating the permeability of the epidermis, and that our CLDN-1 binder is a promising candidate molecule for development as a dermal absorption enhancer.

Discovery of anti-claudin-1 antibodies as candidate therapeutics against hepatitis C virus.

Claudin-1 (CLDN1), a known host factor for hepatitis C virus (HCV) entry and cell-to-cell transmission, is a target molecule for inhibiting HCV infection. We previously developed four clones of mouse anti-CLDN1 monoclonal antibody (mAb) that prevented HCV infection in vitro. Two of these mAbs showed the highest antiviral activity. Here, we optimized the anti-CLDN1 mAbs as candidates for therapeutics by protein engineering. Although Fab fragments of the mAbs prevented in vitro HCV infection, their inhibitory effects were much weaker than those of the whole mAbs. In contrast, human chimeric IgG1 mAbs generated by grafting the variable domains of the mouse mAb light and heavy chains inhibited in vitro HCV infection as efficiently as the parental mouse mAbs. However, the chimeric IgG1 mAbs activated Fcγ receptor, suggesting that cytotoxicity against mAb-bound CLDN1-expressing cells occurred through the induction of antibody-dependent cellular cytotoxicity (ADCC). To avoid ADCC-induced side effects, we prepared human chimeric IgG4 mAbs. The chimeric IgG4 mAbs did not activate Fcγ receptor or induce ADCC, but they prevented in vitro HCV infection as efficiently as did the parental mouse mAbs. These findings indicate that the IgG4 form of human chimeric anti-CLDN1 mAb may be a candidate molecule for clinically applicable HCV therapy.

Use of cell-based screening to identify small-molecule compounds that modulate claudin-4 expression.

Claudins constitute a family of at least 27 proteins with four transmembrane domains, and play a pivotal role in maintaining tight-junctions seals in diverse epithelial tissues. The expression of claudin-4 often changes in intestinal tissues of inflammatory bowel disease and various human cancers. Therefore, claudin-4 is a promising target for treatment of these diseases. In our previous study, we established a reporter cell line to monitor claudin-4 expression on the basis of a functional claudin-4 promoter. Using this cell line, we have performed a cell-based screen of a library containing 2642 biologically active small-molecule compounds to identify modulators of claudin-4 expression. The screen identified 24 potential modulators of the claudin-4 promoter activity. Fourteen of these compounds (12 of them novel) induced endogenous claudin-4 expression. The identified compounds might serve as lead compounds targeting aberrant gene expression in inflammatory bowel disease.

Development of an anti-claudin-3 and -4 bispecific monoclonal antibody for cancer diagnosis and therapy.

Most malignant tumors are derived from epithelium, and claudin (CLDN)-3 and CLDN-4 are frequently overexpressed in such tumors. Although antibodies have potential in cancer diagnostics and therapy, development of antibodies against CLDNs has been difficult because the extracellular domains of CLDNs are too small and there is high homology among human, rat, and mouse sequences. Here, we created a monoclonal antibody that recognizes human CLDN-3 and CLDN-4 by immunizing rats with a plasmid vector encoding human CLDN-4. A hybridoma clone that produced a rat monoclonal antibody recognizing both CLDN-3 and -4 (clone 5A5) was obtained from a hybridoma screen by using CLDN-3- and -4-expressing cells; 5A5 did not bind to CLDN-1-, -2-, -5-, -6-, -7-, or -9-expressing cells. Fluorescence-conjugated 5A5 injected into xenograft mice bearing human cancer MKN74 or LoVo cells could visualize the tumor cells. The human-rat chimeric IgG1 monoclonal antibody (xi5A5) activated FcγRIIIa in the presence of CLDN-3- or -4-expressing cells, indicating that xi5A5 may exert antibody-dependent cellular cytotoxicity. Administration of xi5A5 attenuated tumor growth in xenograft mice bearing MKN74 or LoVo cells. These results suggest that 5A5 shows promise in the development of a diagnostic and therapeutic antibody for cancers.

A novel proapoptotic gene PANO encodes a post-translational modulator of the tumor suppressor p14ARF.

The protein p14ARF is a known tumor suppressor protein controlling cell proliferation and survival, which mainly localizes in nucleoli. However, the regulatory mechanisms that govern its activity or expression remain unclear. Here, we report that a novel proapoptotic nucleolar protein, PANO, modulates the expression and activity of p14ARF in HeLa cells. Overexpression of PANO enhances the stability of p14ARF protein by protecting it from degradation, resulting in an increase in p14ARF expression levels. Overexpression of PANO also induces apoptosis under low serum conditions. This effect is dependent on the nucleolar localization of PANO and inhibited by knocking-down p14ARF. Alternatively, PANO siRNA treated cells exhibit a reduction in p14ARF protein levels. In addition, ectopic expression of PANO suppresses the tumorigenicity of HeLa cells in nude mice. These results indicate that PANO is a new apoptosis-inducing gene by modulating the tumor suppressor protein, p14ARF, and may itself be a new candidate tumor suppressor gene.

A baculoviral display system to assay viral entry.

In this study, we evaluated a baculoviral display system for analysis of viral entry by using a recombinant adenovirus (Ad) carrying a luciferase gene and budded baculovirus (BV) that displays the adenoviral receptor, coxsackievirus and adenovirus receptor (CAR). CAR-expressing B16 cells (B16-CAR cells) were infected with luciferase-expressing Ad vector in the presence of BV that expressed or lacked CAR (CAR-BV and mock-BV, respectively). Treatment with mock-BV even at doses as high as 5 µg/mL failed to attenuate the luciferase activity of B16-CAR cells. In contrast, treatment with CAR-BV with doses as low as 0.5 µg/mL significantly decreased the luciferase activity of infected cells, which reached 65% reduction at 5 µg/mL. These findings suggest that a receptor-displaying BV system could be used to evaluate viral infection.

A simple reporter assay for screening claudin-4 modulators.

Claudin-4, a member of a tetra-transmembrane protein family that comprises 27 members, is a key functional and structural component of the tight junction-seal in mucosal epithelium. Modulation of the claudin-4-barrier for drug absorption is now of research interest. Disruption of the claudin-4-seal occurs during inflammation. Therefore, claudin-4 modulators (repressors and inducers) are promising candidates for drug development. However, claudin-4 modulators have never been fully developed. Here, we attempted to design a screening system for claudin-4 modulators by using a reporter assay. We prepared a plasmid vector coding a claudin-4 promoter-driven luciferase gene and established stable reporter gene-expressing cells. We identified thiabendazole, carotene and curcumin as claudin-4 inducers, and potassium carbonate as a claudin-4 repressor by using the reporter cells. They also increased or decreased, respectively, the integrity of the tight junction-seal in Caco-2 cells. This simple reporter system will be a powerful tool for the development of claudin-4 modulators.

A claudin-targeting molecule as an inhibitor of tumor metastasis.

Tumor metastasis of epithelium-derived tumors is the major cause of death from malignant tumors. Overexpression of claudin is observed frequently in malignant tumors. However, claudin-targeting antimetastasis therapy has never been investigated. We previously prepared a claudin-4-targeting antitumor molecule that consisted of the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) fused to protein synthesis inhibitory factor (PSIF) derived from Pseudomonas exotoxin. In the present study, we investigated whether claudin CPE receptors can be a target for tumor metastasis by using the C-CPE-fused PSIF as a claudin-targeting agent. One of the most popular murine metastasis models is the lung metastasis of intravenously injected B16 cells. Therefore, we first investigated the effects of the C-CPE-fused PSIF on lung metastasis of claudin-4-expressing B16 (CL4-B16) cells. Intravenous administration of the C-CPE-fused PSIF suppressed lung metastasis of CL4-B16 cells but not B16 cells. Injection of C-CPE-fused PSIF also inhibited tumor growth and spontaneous lung metastasis of murine breast cancer 4T1 cells inoculated into the subcutis. Treatment with C-CPE-fused PSIF did not show apparent side effects in mice. These findings indicate that claudin targeting may be a novel strategy for inhibiting some tumor metastases.

Hepatoprotective effect of syringic acid and vanillic acid on CCl4-induced liver injury.

The mycelia of the edible mushroom Lentinula edodes can be cultured in solid medium containing lignin, and the hot-water extracts (L.E.M.) is commercially available as a nutritional supplement. During the cultivation, phenolic compounds, such as syringic acid and vanillic acid, were produced by lignin-degrading peroxidase secreted from L. edodes mycelia. Since these compounds have radical scavenging activity, we examined their protective effect on oxidative stress in mice with CCl(4)-induced liver injury. We examined the hepatoprotective effect of syringic acid and vanillic acid on CCl(4)-induced chronic liver injury in mice. The injection of CCl(4) into the peritoneal cavity caused an increase in the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. The intravenous administration of syringic acid and vanillic acid significantly decreased the levels of the transaminases. Four weeks of CCl(4) treatment caused a sufficiently excessive deposition of collagen fibrils. An examination of Azan-stained liver sections revealed that syringic acid and vanillic acid obviously suppressed collagen accumulation and significantly decreased the hepatic hydroxyproline content, which is the quantitative marker of fibrosis. Both of these compounds inhibited the activation of cultured hepatic stellate cells, which play a central role in liver fibrogenesis, and maintained hepatocyte viability. These data suggest that the administration of syringic acid and vanillic acid could suppress hepatic fibrosis in chronic liver injury.

Lignosulfonic acid attenuates NF-κB activation and intestinal epithelial barrier dysfunction induced by TNF-α/IFN-γ in Caco-2 cells.

Lentinula edodes mycelia solid culture extract (MSCE) is used as a medical food ingredient and provides beneficial effects to patients with cancer and chronic type C hepatitis. Low molecular weight lignin (LM-lignin), which is an active component of MSCE, exhibits hepatoprotective, antitumor, antiviral, and immunomodulatory effects. In this study, we investigated the effect of LM-lignin/lignosulfonic acid on intestinal barrier function. Lignosulfonic acid enhanced transepithelial membrane electrical resistance in human intestinal Caco-2 cell monolayers. In Caco-2 cells treated with lignosulfonic acid, expression of claudin-2, which forms high conductive cation pores in tight junctions (TJs), was decreased. Lignosulfonic acid also attenuated the barrier dysfunction that is caused by tumor necrosis factor (TNF)-α and interferon (IFN)-γ in Caco-2 cells. TNF-α- and IFN-γ-induced activation of NF-κB, such as translocation of NF-κB p65 into the nucleus and induction of gene expression, was inhibited by lignosulfonic acid treatment. Furthermore, lignosulfonic acid decreased the TNF-α- and IFN-γ-induced increase in interleukin (IL)-1ß and IL-6 expression in Caco-2 cells. These results suggest that lignosulfonic acid not only enhances TJ barrier function but also restores TJ barrier integrity impaired by inflammatory cytokines. Therefore, lignosulfonic acid may be beneficial for the treatment of inflammation-induced intestinal barrier dysfunction observed in inflammatory bowel disease.

Safety evaluation of a human chimeric monoclonal antibody that recognizes the extracellular loop domain of claudin-2.

Claudin-2 (CLDN-2), a pore-forming tight junction protein with a tetra-transmembrane domain, is involved in carcinogenesis and the metastasis of some cancers. Although CLDN-2 is highly expressed in the tight junctions of the liver and kidney, whether CLDN-2 is a safe target for cancer therapy remains unknown. We recently generated a rat monoclonal antibody (mAb, clone 1A2) that recognizes the extracellular domains of human and mouse CLDN-2. Here, we investigated the safety of CLDN-2-targeted cancer therapy by using 1A2 as a model therapeutic antibody. Because most human therapeutic mAbs are IgG1 subtype that can induce antibody-dependent cellular cytotoxicity, we generated a human-rat chimeric IgG1 form of 1A2 (xi-1A2). xi-1A2 activated Fcγ receptor IIIa in the presence of CLDN-2-expressing cells, indicating that xi-1A2 likely exerts antibody-dependent cellular cytotoxicity. At 24 h after its intravenous injection, xi-1A2 was distributed into the liver, kidney, and tumor tissues of mice bearing CLDN-2-expressing fibrosarcoma cells. Treatment of the xenografted mice with xi-1A2 attenuated tumor growth without apparent adverse effects, such as changes in body weight and biochemical markers of liver and kidney injury. These results support xi-1A2 as the lead candidate mAb for safe CLDN-2-targeted cancer therapy.

Angubindin-1 opens the blood-brain barrier in vivo for delivery of antisense oligonucleotide to the central nervous system.

Within the field of RNA therapeutics, antisense oligonucleotide-based therapeutics are a potentially powerful means of treating intractable diseases. However, if these therapeutics are used for the treatment of neurological disorders, safe yet efficient methods of delivering antisense oligonucleotides across the blood-brain barrier to the central nervous system must be developed. Here, we examined the use of angubindin-1, a binder to the tricellular tight junction, to modulate paracellular transport between brain microvascular endothelial cells in the blood-brain barrier for the delivery of antisense oligonucleotides to the central nervous system. This proof-of-concept study demonstrated that intravenously injected angubindin-1 increased the permeability of the blood-brain barrier and enabled transient delivery of subsequently administered antisense oligonucleotides into the mouse brain and spinal cord, leading to silencing of a target RNA without any overt adverse effects. We also found that two bicellular tight junction modulators did not produce such a silencing effect, suggesting that the tricellular tight junction is likely a better target for the delivery of antisense oligonucleotides than the bicellular tight junction. Our delivery strategy of modulating the tricellular tight junction in the blood-brain barrier via angubindin-1 provides a novel avenue of research for the development of antisense oligonucleotide-based therapeutics for the treatment of neurological disorders.

Identification of claudin-4 binder that attenuates tight junction barrier function by TR-FRET-based screening assay.

Claudins are key functional and structural components of tight junctions (TJs) in epithelial cell sheets. The C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) binds to claudin-4 and reversibly modulates intestinal TJ seals, thereby enhancing paracellular transport of solutes. However, the use of C-CPE as an absorption enhancer is limited by the molecule's immunogenicity and manufacturing cost. Here, we developed a high-throughput screening system based on the Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) method to identify claudin-4 binders in a library collection of 32,560 compounds. Thiostrepton, identified from the screen, decreased transepithelial electrical resistance and increased flux of 4-kDa fluorescein isothiocyanate-labelled dextran (FD-4) in Caco-2 cell monolayers, a model of intestinal epithelium. Thiostrepton changed the expression, but not the localisation, of TJ components. Treatment of rat jejunum with thiostrepton increased the absorption of FD-4 without tissue toxicity, indicating that thiostrepton is a novel claudin-4 binder that enhances intestinal permeability. The screening system may therefore be a useful tool for identifying claudin-4 binders to enhance drug absorption in mucosa.

Angubindin-1, a novel paracellular absorption enhancer acting at the tricellular tight junction.

A limiting barrier for mucosal absorption of drugs is the tight junction (TJ). TJs exist between two adjacent cells (bicellular TJ, bTJ) and at the sites where three cells meet (tricellular TJ, tTJ). We present a novel approach which employs a physiologically regulated pathway for the passage of large molecules through the tTJ. Main barrier-relevant tTJ proteins are tricellulin and angulin-1 to -3. We developed an angulin binder from Clostridium perfringens iota-toxin (Ib) whose receptor is angulin-1. An Ib fragment corresponding to amino acids 421-664 (Ib421-664) of iota-toxin proved to bind in cells expressing angulin-1 and -3, but not angulin-2. This binding led to removal of angulin-1 and tricellulin from the tTJ which enhanced the permeation of macromolecular solutes. Ib421-664 enhanced intestinal absorption in rats and mice. Our findings indicate that Ib421-664, which we designate angubindin-1, is a modulator of the tTJ barrier and that modulation of that barrier qualifies for a new strategy of developing a mucosal absorption enhancer.