Overexpression and characterization of carboxyl-terminal processing protease for precursor D1 protein: regulation of enzyme-substrate interaction by molecular environments

CtpA, which is classified as a novel type of serine protease with a Ser/Lys catalytic dyad, is responsible for the C-terminal processing of precursor D1 protein (pD1) of the photosystem II reaction center, a process that is indispensable for the integration of water-splitting machinery in photosynthesis. In this study, overexpression in Escherichia coli and one-step purification of spinach CtpA were carried out to analyze the characteristics of this new type of protease and to elucidate the molecular interactions in the C-terminal processing of pD1 on the thylakoid membrane. The successful accumulation of functional CtpA in E. coli may argue against the possibility, based on homology to E. coli Tsp, that the enzyme is involved in the degradation of incomplete proteins in chloroplasts, e.g. by utilizing the ssrA-tagging system. Analysis using a synthetic pD1 oligopeptide demonstrated that the enzymatic properties (including substrate recognition) of overexpressed CtpA with an extra sequence of GSHMLE at the N terminus were indistinguishable from those of the native enzyme. CtpA was insensitive to penem, which has been shown to inhibit some Ser/Lys-type proteases, suggesting that the catalytic center of CtpA is quite unique. By using the substrate in different molecular environments (i.e. synthetic pD1 oligopeptide in solution and pD1 in photosystem II-enriched thylakoid membrane), we observed a dramatic difference in the pH profile and affinity for the substrate, suggesting the presence of a specific interaction of CtpA with a factor(s) that modulates the pH dependence of proteolytic action in response to physiological conditions.

Role of mast cells in antigen-induced airway inflammation and bronchial hyperresponsiveness in rats

The participation of mast cells in the induction of antigen-induced airway inflammation and bronchial hyperresponsiveness (BHR) to acetylcholine (ACh) was investigated using pharmacological agents and mast cell-deficient rats (Ws/Ws). A significant increase in the number of leukocytes in bronchoalveolar lavage fluid (BALF) and bronchial responsiveness to ACh were observed 24 h after antigen (ovalbumin) challenge in sensitized Brown-Norway (BN) rats. Disodium cromoglycate and terfenadine did not inhibit antigen-induced airway inflammation and BHR in sensitized BN rats. In contrast, cyclosporin A (CyA), FK-506 and prednisolone significantly inhibited antigen-induced airway inflammation and BHR in sensitized BN rats. In addition, disodium cromoglycate, terfenadine and prednisolone, but not CyA and FK-506, inhibited homologous passive cutaneous anaphylaxis in rats. Furthermore, a significant increase in the number of leukocytes in BALF and BHR was also observed in Ws/Ws rats 24 h after inhalation of antigen; however, the magnitude of BHR in Ws/Ws rats was lower than that in the congenic rats. These findings suggest that mast cells play a partial role in the development of antigen-induced BHR in rats and that the induction of BHR is barely suppressed by mast cell stabilizing agents.

Scratching behavior in various strains of mice

Scratching behavior was induced in 12 strains of mice and the frequency was compared. An injection of histamine at a dose of 50 nmol induced frequent scratching behavior only in ICR mice, although the same dose of serotonin induced frequent scratching behavior in all strains of mice except for A/J. Histamine (10 nmol), serotonin (1 nmol), substance P (50 nmol) and passive cutaneous anaphylaxis induced significant vascular permeability increase in BALB/c, ICR, ddY and NC/Nga mice. These four stimuli also induced frequent scratching behavior in ICR mice. However, they failed to induce substantial increase in the incidence of scratching in the other three strains, except for ddY, which exhibited a slight but significant increase against substance P injection. These results suggest that the ICR mouse is a good responder for scratching behavior against various stimuli, especially against histamine. Thus ICR mice may be suitable for studying mediators and/or mechanisms for itching.

Atp-binding cassette transporter ABC2/ABCA2 in the rat brain: a novel mammalian lysosome-associated membrane protein and a specific marker for oligodendrocytes but not for myelin sheaths

We recently cloned a full-length cDNA of the rat ATP-binding cassette transporter 2 (ABC2, or ABCA2) protein, a member of the ABC1 (or ABCA) subfamily (-ABC1/ABCA1 is a causal gene for Tangier disease) and found it to be strongly expressed in the rat brain. In this study, we identified ABC2 as a lysosome-associated membrane protein that is being localized specifically in oligodendrocytes. The ABC2-immunolabeled cells were detected mainly in the white matter but were also scattered in gray matter throughout the whole brain. In addition, these cells were found to be colocalized with 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase) immunoreactivity when the marker antibody for oligodendrocytes was used. However, no such colocalization was observed with markers for other kinds of glial cells. Unlike the CNP antibody, which also intensely stains myelin sheaths in the white matter, ABC2 immunoreactivity was detected only in the cell bodies of oligodendrocytes. At the ultrastructural level, ABC2 immunoreactivity was detected mostly around lysosome and partly in Golgi apparatus by electron microscopy. This was confirmed by immunocolocalization of ABC2 and lysosomal markers in a neuroblastoma cell line. Immunoblotting analysis of ABC2 from the whole brain and the ABC2-transfected cell line revealed bands at approximately 260 kDa. The result of in situ hybridization with a riboprobe for ABC2 matched the results obtained from immunostaining. These findings strongly suggest that ABC2 is a specific marker for oligodendrocytes but not for myelinsheaths and that it is as a novel mammalian lysosome-associated membrane protein involved in myelinization or other kinds of metabolism in the CNS.

Development and characterization of 1C6-203, a new monoclonal antibody specific to human thymidine phosphorylase

Thymidine phosphorylase (dThdPase) is an essential enzyme for activation of the oral cytostatic drug capecitabine and its intermediate metabolite, doxifluridine, to 5-fluorouracil in tumors. Methods to estimate dThdPase expression in tumor tissue might be useful to predict the efficacy of capecitabine and doxifluridine in cancer patients. We established a new monoclonal antibody (MAb), 1C6-203, applicable for dThdPase immunohistochemistry and compared its staining characteristics with those of a previously established MAb, 654-1. In 4% paraformaldehyde-fixed colorectal carcinoma, 1C6-203 and 654-1 stained cancer cells in 19/30 and 9/30 patients, respectively. In 10% formalin-fixed colorectal carcinoma, 1C6-203 and 654-1 stained cancer cells in 18/30 and 6/30 patients, respectively. In negative 10% formalin-fixed tissues, microwave treatment improved the positivity of 654-1-stained cancer cells. These results suggest that an epitope recognized by 1C6-203 is resistant to epitope masking by formaldehyde fixation, whereas that for MAb 654-1 is sensitive. Therefore, MAb 1C6-203 might be more suitable than MAb 654-1 for evaluating dThdPase expression in colorectal carcinoma.

Prednisolone inhibits an IgE-mediated late-phase allergic cutaneous reactionby interfering with the activation of mast cells in mice

Epicutaneous antigen challenge in passively sensitized mice with IgE produces a biphasic cutaneous response which peaks 1 h (immediate-phase reaction) and 24 h (late-phase reaction; LPR) after the antigen challenge. In this model, anaphylactic degranulation and interleukin 6 (IL-6) expression between 4 and 8 h are observed in resident mast cells as the preceding stage of LPR. Prednisolone at a dose of 3 mg kg(-1) clearly inhibited the LPR when administered 2 h before and 4 h after antigen challenge. Slight or no inhibition of LPR was observed by prednisolone administered 6-12 h after challenge. Histologically, prednisolone treatment 2 h before antigen challenge completely inhibited edema and inflammatory cell infiltration, while treatment at 6 h did not at all. In order to investigate the relationship between inhibition of LPR by prednisolone and mast cell activation, the effects of prednisolone on degranulation of mast cells and IL-6 expression in mast cells were investigated. 8 h after antigen challenge, prednisolone clearly inhibited the increase in the number of anaphylactic degranulated and IL-6-positive mast cells by administration 2 h before challenge, but did not affect it by administration 6 h after challenge. These data indicate that the inhibitory mechanism of prednisolone on LPR, at least, involves the inhibition of mast cell activation before LPR.

Inhibition of passive cutaneous anaphylaxis-associated scratching behavior by mu-opioid receptor antagonists in ICR mice

BACKGROUND

Itching in humans is attenuated by mu-opioid receptor antagonists. ICR mice display increases in scratching behavior upon induction of IgE-mediated passive cutaneous anaphylaxis (PCA), or intradermal injection of compound 48/80 or histamine.

METHODS

Cutaneous reactions were induced in ICR mice by IgE-mediated PCA, compound 48/80 and histamine, and the scratching behavior associated with the cutaneous reactions was evaluated.

RESULTS

Naloxone and nalmefene reduced the incidence of scratching behavior associated with PCA. Naloxone also inhibited the induction of scratching behavior caused by compound 48/80 and histamine. Naloxone did not affect the increase in vascular permeability caused by PCA and injection of compound 48/80.

CONCLUSION

Scratching behavior in mice may be induced by a sensation or a mechanism similar to itching in humans and should become a useful model for examining itching in humans.

Cloning, characterization and tissue distribution of the rat ATP-binding cassette (ABC) transporter ABC2/ABCA2

The ABC1 (ABCA) subfamily of the ATP-binding cassette (ABC) transporter superfamily has a structural feature that distinguishes it from other ABC transporters. Here we report the cloning, molecular characterization and tissue distribution of ABC2/ABCA2, which belongs to the ABC1 subfamily. Rat ABC2 is a protein of 2434 amino acids that has 44.5%, 40.0% and 40.8% identity with mouse ABC1/ABCA1, human ABC3/ABCA3 and human ABCR/ABCA4 respectively. Immunoblot analysis showed that proteins of 260 and 250 kDa were detected in COS-1 cells transfected with ABC2 having a haemagglutinin tag, while no band was detected in mock-transfected cells. After incubation with N-glycosidase F, the mobilities of the two proteins increased and a single band was detected, suggesting that ABC2 is a glycoprotein. Photoaffinity labelling with 8-azido-[alpha-(32)P]ATP confirmed that ATP binds to the ABC2 protein in the presence of Mg(2+). RNA blot analysis showed that ABC2 mRNA is most abundant in rat brain. Examination of brain by in situ hybridization determined that ABC2 is expressed at high levels in the white matter, indicating that it is expressed in the oligodendrocytes. ABC2, therefore, is a glycosylated ABC transporter protein, and may play an especially important role in the brain. In addition, the N-terminal 60-amino-acid sequence of the human ABC1, which was missing from previous reports, has been determined.

Activation of Ca2+/calmodulin-dependent protein kinase II within post-synaptic dendritic spines of cultured hippocampal neurons

To understand the cell signaling of protein kinases, it is essential to monitor their activity in each of the subcellular compartments. Here we developed a method to visualize the activities of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in the cytoplasm, plasma membrane, and nucleus, separately, by utilizing targeted phosphorylation motifs and phosphorylation-specific antibodies. This approach was used to monitor the activities of post-synaptic CaMKII in cultured hippocampal neurons. Strong stimulation of the neurons by N-methyl-d-aspartate led to global activations of CaMKII in the cell bodies and dendrites. On the other hand, weak stimulation by removal of Mg(2+) block of N-methyl-d-aspartate receptors induced CaMKII signaling localized within single dendritic spines. Post-synaptic CaMKII is thought to modify synaptic efficiency. The present data for the first time demonstrate the activation of CaMKII localized within single dendritic spines and are consistent with the notion that synaptic efficiency is modified by CaMKII in single or multiple spine level depending on the strength of receptor activation.

Roles of mitogen-activated protein kinase pathways for mediator release from human cultured mast cells

Human cultured mast cells (HCMC) secrete histamine, sulfidoleukotrienes (LTs), and prostaglandin D(2) (PGD(2)), and produce a variety of cytokines after aggregation of high-affinity receptors for IgE (FcepsilonRI). With respect to the mitogen-activated protein kinase (MAPK) family, extracellular signal-regulated kinases (ERKs), c-Jun NH(2)-terminal kinases (JNKs), and p38 mitogen-activated protein kinase (p38 MAPK) are known. To investigate the roles of these kinase pathways for mediator release from human mast cells, we examined the participation of the activation of these kinases in mediator release, using 1,4-diamino-2, 3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126), an ERK pathway inhibitor, and 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imid azo le (SB203580), a p38 MAPK pathway inhibitor. U0126 inhibited ERK activation, LT and PGD(2) release, and granulocyte macrophage-colony stimulating factor (GM-CSF) production after stimulation of HCMC. SB203580, on the other hand, potentiated JNK activation and GM-CSF production. The findings of the present study demonstrated that: (i) the release of arachidonic acid metabolites is mediated by the ERK pathway; (ii) GM-CSF production may be driven by both the ERK and JNK pathways; and (iii) the p38 MAPK pathway negatively regulates the JNK pathway. This suggests that MAPK pathways play important roles in mediator release from human mast cells.

Phosphorylation of collapsin response mediator protein-2 by Rho-kinase. Evidence for two separate signaling pathways for growth cone collapse

We previously identified Rho-associated protein kinase (Rho-kinase) as a specific effector of Rho. In this study, we identified collapsin response mediator protein-2 (CRMP-2), as a novel Rho-kinase substrate in the brain. CRMP-2 is a neuronal protein whose expression is up-regulated during development. Rho-kinase phosphorylated CRMP-2 at Thr-555 in vitro. We produced an antibody that specifically recognizes CRMP-2 phosphorylated at Thr-555. Using this antibody, we found that Rho-kinase phosphorylated CRMP-2 downstream of Rho in COS7 cells. Phosphorylation of CRMP-2 was observed in chick dorsal root ganglion neurons during lysophosphatidic acid (LPA)-induced growth cone collapse, whereas the phosphorylation was not detected during semaphorin-3A-induced growth cone collapse. Both LPA-induced CRMP-2 phosphorylation and LPA-induced growth cone collapse were inhibited by Rho-kinase inhibitor HA1077 or Y-32885. LPA-induced growth cone collapse was also blocked by a dominant negative form of Rho-kinase. On the other hand, semaphorin-3A-induced growth cone collapse was not inhibited by a dominant negative form of Rho-kinase. Furthermore, overexpression of a mutant CRMP-2 in which Thr-555 was replaced by Ala significantly inhibited LPA-induced growth cone collapse. These results demonstrate the existence of Rho-kinase-dependent and -independent pathways for growth cone collapse and suggest that CRMP-2 phosphorylation by Rho-kinase is involved in the former pathway.

Effect of a novel anti-allergic agent, HSR-609, on antigen-induced airway hyperresponsiveness in mice

The effects of a newly synthesized anti-allergic agent, HSR-609, on allergic airway hyperresponsiveness and airway inflammation have been studied in sensitized mice. The effects were compared with those of two histamine H(1) receptor antagonists, cetirizine and terfenadine, and prednisolone. Three inhalations of antigen caused an increase in leukocytes (including eosinophils) with increases in IL-5 in BALF and airway hyperresponsiveness to acetylcholine in BALB/c mice. All drugs were orally administered once a day for 10 days from the day before the first inhalation of antigen. HSR-609 (10 mg/kg) and prednisolone (5 mg/kg) significantly inhibited the antigen-induced airway hyperresponsiveness, whereas cetirizine (10 mg/kg) or terfenadine (100 mg/kg) did not affect this airway response. At the same time HSR-609 inhibited the antigen-induced eosinophilia and IL-5 production in BALF. Prednisolone also showed an inhibitory effect on the airway eosinophilia and IL-5 production but not cetirizine and terfenadine in the same experiments. In addition, HSR-609 (p.o.) dose-dependently suppressed the accumulation of eosinophils elicited by antigen-stimulated D10G4.1 cells, a murine Th2 clone, in peritoneal cavity lavage fluid in AKR/J mice. These results suggest that HSR-609 inhibits allergic airway hyperresponsiveness to acetylcholine probably because of the inhibition of Th2-dependent eosinophilia caused by IL-5. In addition, effects of HSR-609 were different from those of cetirizine and terfenadine concerning the inhibition of antigen-induced airway hyperresponsiveness in mice.

Measurement of glucose uptake and intracellular calcium concentration in single, living pancreatic beta-cells

There has been no method previously to measure both glucose transport and its effect on the various intracellular functions in single, living mammalian cells. A fluorescent derivative of d-glucose, 2-[N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)amino]-2-deoxy-d-glucose (2-NBDG), that we have developed has made such measurements possible. COS-1 cells that overexpress the human glucose transporter GLUT2 show significantly greater 2-NBDG uptake than mock transfected cells. Using GLUT2-abundant mouse insulin-secreting clonal MIN6 cells, we found that 2-NBDG was incorporated into the cells in a time- and concentration-dependent manner. The 2-NBDG uptake was inhibited by high concentrations of d-glucose in a dose-dependent manner and also was almost completely inhibited by 10 micrometer cytochalasin B. We then measured both glucose uptake and the intracellular calcium concentration ([Ca(2+)](i)) in single, living pancreatic islet cells. 2-NBDG and fura-2 were used as the tracer of glucose and indicator of intracellular calcium, respectively. All of the cells that showed an increase in [Ca(2+)](i) in response to a high concentration of glucose (16.8 mm) rapidly incorporated significant 2-NBDG. Immunocytochemical examination confirmed these cells to be insulin-positive beta-cells. All of the cells that showed no significant, rapid 2-NBDG uptake lacked such glucose responsiveness of [Ca(2+)](i), indicating that these cells were non-beta-cells such as glucagon-positive alpha-cells. These results show the uptake of glucose causing a concomitant increase of [Ca(2+)](i) in beta-cells. Because 2-NBDG is incorporated into mammalian cells through glucose transporters, it should be useful for the measurement of glucose uptake together with concomitant intracellular activities in many types of single, living mammalian cells.

Evaluation of anti-scratch properties of oxatomide and epinastine in mice

Anti-scratch effects of oxatomide and epinastine were examined in mice. Scratching behavior and cutaneous reactions were induced in BALB/c, ICR and ddY mice by dinitrofluorobenzene painting, passive cutaneous anaphylaxis and substance P injection, respectively. Although oxatomide and epinastine failed to inhibit scratching behavior in BALB/c mice, they inhibited the cutaneous reaction significantly. The drugs potently inhibited both scratching behavior and cutaneous reaction in ICR mice. They also inhibited scratching behavior and cutaneous reaction in ddY mice, although cetirizine and terfenadine failed to affect them. Histamine did not induce frequent scratching behavior in BALB/c and ddY mice. These results indicate that oxatomide and epinastine inhibit the scratching behavior in ICR mice associated with passive cutaneous anaphylaxis mainly through an antagonistic action on histamine H(1) receptors. The results also indicate that these drugs inhibit substance P-induced scratching behavior in ddY mice through an action independent of the antagonistic action on histamine H(1) receptors.

Effect of a fluorinated pyrimidine on cachexia and tumour growth in murine cachexia models: relationship with a proteolysis inducing factor

The fluorinated pyrimidine nucleoside, 5'-deoxy-5-fluorouridine (5'-dFUrd) has been shown to effectively attenuate the progress of cachexia in the murine adenocarcinomas MAC16 and colon 26 as well as in the human uterine cervical carcinoma xenograft, Yumoto. Although concomitant inhibition of tumour growth was observed in all three models this was not sufficient to account for the preservation of body weight. An attempt has been made to correlate the anti-cachectic activity of 5'-dFUrd with the presence of a tumour produced proteolysis-inducing factor (PIF), thought to be responsible for the development of cachexia in the MAC16 model. Two variants of colon 26 adenocarcinoma were employed, clone 20 which produces profound cachexia, and clone 5 which produces no change in body weight in recipient animals. Mice bearing the colon 26, clone 20 variant showed evidence for the presence of PIF in tumour, serum and urine, while there was no evidence for the presence of PIF in tumour or body fluids of mice bearing the clone 5 tumours. Treatment of animals bearing the clone 20 variant with 5'-dF Urd led to the disappearance of PIF from the tumour, serum and urine concomitant with the attenuation of the development of cachexia. The human cervical carcinoma, Yumoto, which also induced cachexia in recipiant animals, showed expression of PIF in tumour, serum and urine in control and vehicle-treated mice, but was absent in mice treated with 5'-dFUrd. Thus in these experimental models cachexia appears to be correlated with the presence of PIF.

Role of mast cells in the onset of IgE-mediated late-phase cutaneous response in mice

BACKGROUND

In mice that are passively sensitized to IgE, cutaneous antigen challenge produces a biphasic response with peaks at 1 and 24 hours after challenge.

OBJECTIVE

We investigated the role of mast cells in the IgE-mediated late-phase reaction in mice.

METHODS

We histologically and ultrastructurally investigated the morphologic changes of mast cells during the biphasic responses.

RESULTS

Degranulation of mast cells, which was observed between 4 and 24 hours after challenge, reached a peak at 8 hours. Piecemeal degranulation was seen during the immediate phase reaction. The number of IL-6-positive mast cells was increased after 4 hours in both IgE-sensitized and unsensitized mice, but positive cells showed a greater increase in sensitized mice and reached a peak after 8 hours. With in situ hybridization experiments, mast cells were positive for IL-6 messenger RNA at 6 hours after challenge.

CONCLUSION

These findings indicate that anaphylactic degranulation of mast cells and the expression of IL-6 mRNA within 4 hours after antigen challenge are important for the onset of the late-phase allergic cutaneous reaction in mice.

A sealed cranial window system for simultaneous recording of blood flow, and electrical and optical signals in the rat barrel cortex

We have developed a new sealed cranial window technique which allows the manipulation of simultaneously and independently multiple sensor probes, such as a glass microelectrode and a laser-Doppler probe. possible. Furthermore, normal intracranial pressure (4 mmHg) can be maintained throughout the craniectomy and the experiment. Using this technique, we have measured the neuronal activity and local cerebral blood flow together with the intrinsic optical properties in the rat barrel cortex during mechanical stimulation of the whiskers. The onset of the field response recorded by an extracellular electrode in the principal barrel columns occurred about 8 ms from the beginning of stimulation. These responses were well correlated with the whisker displacements (3 Hz, 2 s). The local cerebral blood flow, measured by laser-Doppler flowmetry, started to increase about 0.5 s after the first field response, peaked at about 1.7 s, and then gradually waned. A similar time-course of changes in the local blood volume was observed by simultaneous intrinsic optical imaging at the hemoglobin-isosbestic wavelength (570 nm). These results suggest that our technique would be useful for assessing the mechanism underlying neurovascular coupling under physiological conditions in vivo.

Effect of Am-80, a retinoid derivative, on 2, 4-dinitrofluorobenzene-induced contact dermatitis in mice

Retinoids have many pharmacological activities, including anti-inflammatory action and antiangiogenesis, effected through the regulation of various gene transcriptions. In this study, we investigated the effect of Am-80, one of the retinoic acid derivatives, on hapten-induced contact hypersensitivity in BALB/c mice. After application of 2,4-dinitrofluorobenzene (DNFB) to the ears of the mice, severe contact hypersensitivity with marked infiltration of inflammatory cells and hypertrophy of the epidermis was caused. The thickness of the ears increased biphasically and reached a peak 3 and 24 h after the DNFB challenge. Am-80 significantly inhibited ear thickness in the late-(24 h), but not the early-phase (3 h) reaction in a dose-dependent manner. In a histopathological study, obvious depression of edema and infiltration of inflammatory cells was observed in the ears of mice treated with Am-80. Am-80 inhibited the levels of expression in mice ears of interferon-gamma (IFN-gamma) and interleukin-6 (IL-6), but not tumor necrosis factor-alpha (TNF-alpha) or interleukin-4 (IL-4). Furthermore, Am-80 inhibited the antigen-induced production of some cytokines, including IFN-gamma and IL-6, but not IL-4, in vitro. Therefore, Am-80 inhibited hapten-induced contact hypersensitivity through the direct inhibition of inflammatory cytokines such as IFN-gamma and IL-6.

Effects of luteolin, quercetin and baicalein on immunoglobulin E-mediated mediator release from human cultured mast cells

BACKGROUND

Flavonoids have a variety of activities including anti-allergic activities, and are known to inhibit histamine release from human basophils and murine mast cells.

OBJECTIVE

The effects of luteolin, a flavone, on the immunoglobulin (Ig) E-mediated allergic mediator release from human cultured mast cells (HCMCs) were investigated and compared with those of baicalein and quercetin.

METHODS

HCMCs were sensitized with IgE, and then treated with flavonoids before challenge with antihuman IgE. The amount of released mediators was determined as was mobilization of intracellular Ca2+ concentration, protein kinase C (PKC) translocation and phosphorylation of intracellular proteins were detected after anti-IgE stimulation.

RESULTS

Luteolin, baicalein and quercetin inhibited the release of histamine, leukotrienes (LTs), prostaglandin D2 (PGD2), and granulocyte macrophage-colony stimulating factor (GM-CSF) from HCMC in a concentration-dependent manner. Additionally, the three flavonoids inhibited A23187-induced histamine release. As concerns Ca2+ signalling, luteolin and quercetin inhibited Ca2+ influx strongly, although baicalein did slightly. With regard to PKC signalling, luteolin and quercetin inhibited PKC translocation and PKC activity strongly, although baicalein did slightly. The suppression of Ca2+ and PKC signallings might contribute to the inhibition of mediator release. The activation of extracellular signal-regulated kinases (ERKs) and c-Jun NH2-terminal kinase (JNK), that were activated just before the release of LTs and PGD2 and GM-CSF mRNA expression in IgE-mediated signal transduction events, were clearly suppressed by luteolin and quercetin. In contrast, the flavonoids did not affect the activation of p38 mitogen-activated protein kinase (p38 MAPK) pathway.

CONCLUSION

These results indicate that luteolin is a potent inhibitor of human mast cell activation through the inhibition of Ca2+ influx and PKC activation.

Effects of luteolin and other flavonoids on IgE-mediated allergic reactions

The anti-allergic action of luteolin was investigated in the rodent experimental allergic models. In the present study, the effects of luteolin were compared to those of baicalein, quercetin, and prednisolone. Luteolin as well as baicalein, quercetin, and prednisolone inhibited the IgE antibody-mediated biphasic cutaneous reaction (immediate phase reaction and late phase reaction) in mice. However, these compounds did not affect the histamine-, serotonin-, and platelet activating factor-induced cutaneous reactions in rats. In an in vitro study, luteolin, baicalein, and quercetin inhibited IgE-mediated histamine release from bone marrow-derived cultured murine mast cells (BMMC) and rat peritoneal mast cells. These compounds also inhibited IgE-mediated TNF-alpha and IL-6 production from BMMC. From these results, luteolin inhibited the IgE-mediated biphasic cutaneous reaction mainly by the inhibition of histamine and cytokine release from mast cells, but not through mediator antagonistic effects.

Synthesis and biological activities of novel antiallergic agents with 5-lipoxygenase inhibiting action

Novel benzimidazole derivatives were synthesized and their pharmacological activities were examined. These compounds showed a good suppressive action on histamine release from rat peritoneal mast cells produced by antigen-antibody reaction, an antagonistic action on guinea pig ileum contraction caused by histamine, an inhibitory action on 5-lipoxygenase in rat basophilic leukemia-1 (RBL-1) cells, and a preventive action on NADPH dependent lipid peroxidation induced by Fe3+-ADP in rat liver microsomes. In addition, 1-[2-[2-(4-Hydroxy-2,3,5-trimethylphenoxy)ethoxy]-ethyl]-2-(4-meth yl-1-homopiperazino)-1H-benzimidazole difumarate (BOM1006) exhibited a dose dependent suppressive action on 48 h homologous passive cutaneous anaphylaxis (PCA) reaction in rats orally administered the drug.

Nonelectrical poling in ferroelectric polythioureas

A new poling method utilizing the cooperativity and strong hydrogen bonding force of thiourea groups is proposed in ferroelectric polythioureas [poly(octamethylene thiourea) and poly(nonamethyleno thiourea)]. The method, which is named "surface energy poling," takes advantage of the surface energy difference of the polar amorphous material to form remanent polarization. A polythiourea film sandwiched between a metal with higher surface energy and polytetrafluoroethylenes with lower surface energy was heated up to T/sub c/ [1.15/spl times/T/sub g/ (glass transition temperature)] and cooled slowly to room temperature. The resulting film showed a pyroelectric constant of 10 /spl mu//m/sup 2/K, giving evidence of remanent polarization. This method is similar to the orientation process in liquid crystal devices.

Different role of IL-4 in the onset of hapten-induced contact hypersensitivity in BALB/c and C57BL/6 mice

1. To study the role of interleukin (IL)-4 in the onset of contact hypersensitivity (CH) in mice, the effect of IL-4 gene-depletion and anti-IL-4 monoclonal antibody treatment on dinitrofluorobenzene (DNFB)-induced CH was examined. Simultaneously, to clarify the effect of background gene, DNFB-induced CH in BALB/c and C57BL/6 mice was compared. 2. Five repeated topical applications of DNFB to the ears of mice resulted in CH of the ears in terms of increases in ear thickness and histopathological changes. The magnitude of ear thickness increase in BALB/c mice was almost three times greater than that in C57BL/6 mice. 3. The CH in BALB/c mice was significantly suppressed by IL-4 gene-depletion and anti-IL-4 monoclonal antibody treatment. In contrast, the symptoms of dermatitis in C57BL/6 mice were slightly affected by the same treatment. These changes corresponded well to the production of specific IgE antibody. 4. Total IgE antibody production and the expression of productive Cepsilon mRNA were dramatically suppressed by IL-4 gene-depletion and anti-IL-4 treatment in BALB/c and C57BL/6 mice. Neither total IgG nor IgM levels in either strain of mice was altered by depletion of IL-4. 5. The expression of IFN-gamma in the skin lesion was dramatically suppressed by IL-4 gene-depletion in BALB/c mice, but not in C57BL/6 mice. 6. These findings indicate that IL-4 plays an important role in the onset of DNFB-induced CH in BALB/c mice, but not in C57BL/6 mice.