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Biomedical subjects

T Ichimaru

Publications and source records attributed to T Ichimaru.

At least 19 recordsLinked to original sources
PubMed2005

dsRNA enhances eotaxin-3 production through interleukin-4 receptor upregulation in airway epithelial cells.

The exacerbation of asthma during viral infections is mainly explained by neutrophils infiltrating into the airways. However, enhanced functions of eosinophils are also observed. The aim of this study was to reveal the mechanism of how eosinophils are activated during and after viral infection of the airways, using a model of viral infection. A synthetic double-stranded RNA, poly inosinic-cytidyric acid (poly(IC)), was transfected to a human airway epithelial cell line (BEAS-2B) and the primary bronchial epithelial cells, to mimic a viral infection. The production of chemokines from the cells was investigated. The transfection of poly(IC), alone, marginally affected the eotaxin-3 production of the cells. However, the transfection of poly(IC) prior to interleukin (IL)-4 stimulation enhanced eotaxin-3 production. Poly(IC) transfection increased mRNA and protein expressions of IL-4 receptor (R)alpha and IL-2Rgamma, components of the IL-4R. In BEAS-2B cells, IL-4-mediated phosphorylation of signal transducer and activator of transcription six was enhanced in poly(IC) transfected cells. This was reversed by the addition of anti-IL-4Ralpha antibody, suggesting the role of an increased number of IL-4 receptors in enhanced IL-4-induced eotaxin-3 production. Poly(IC)-induced upregulation of IL-4Ralpha was inhibited by treatment with cycloheximide or dexamethasone. In conclusion, these results suggest that viral airway infection may enhance interleukin-4-induced eotaxin-3 production through upregulation of the interleukin-4 receptor in airway epithelial cells.

Cells, Cultured↗
PubMed2003

Central cholecystokinin-octapeptide accelerates the activity of the hypothalamic gonadotropin-releasing hormone pulse generator in goats.

To clarify central actions of cholecystokinin-octapeptide (CCK-8) on reproduction, effects of an intracerebroventricular (i.c.v.) administration of CCK-8 on the activity of the gonadotropin-releasing hormone (GnRH) pulse generator were examined in ovariectomized (OVX) goats in the absence or presence of oestradiol. Goats were chronically fitted with recording electrodes in the mediobasal hypothalamus, and electrophysiological manifestations of the GnRH pulse generator were monitored as characteristic increases in the multiple-unit activity (MUA volleys). In OVX goats, a bolus i.c.v. injection of as little as 0.01 nmol of CCK-8 induced a MUA volley with a short latency, which resulted in a significant decrease in the post-treatment volley interval compared to that in the saline injected control. Administration of higher doses of CCK-8 (0.1 and 2 nmol) did not further accelerate the occurrence of the MUA volley, but stimulatory effects were observed for a longer period than that after the 0.01 nmol injection. When goats were treated with oestradiol, while a bolus i.c.v. injection of 0.01 nmol CCK-8 had no effect, an injection of 0.1 nmol of the peptide significantly decreased the post-treatment volley interval. On continuous i.c.v. infusion of CCK-8 at 3 nmol per 200 micro l/h for 3 h, MUA volleys with shorter intervals than those in the control were successively induced without any apparent change in basal plasma luteinizing hormone levels in OVX goats. These results demonstrate that central CCK-8 strongly accelerates the activity of the GnRH pulse generator in goats.

Animals↗
PubMed2001

A possible role of neuropeptide Y as a mediator of undernutrition to the hypothalamic gonadotropin-releasing hormone pulse generator in goats.

To understand central mechanisms for nutritional infertility, the activity of the GnRH pulse generator was directly assessed in ovariectomized (OVX) goats under several experimental conditions by recording characteristic increases in the multiple-unit activity (volleys). When estradiol (E(2))-treated animals were fasted for 4-5 days, the activity of the GnRH pulse generator was gradually suppressed, and the volley interval at the end of fasting was significantly prolonged, compared with that during the feeding period (67.4 vs. 49.3 min, n = 5, P < 0.01). On the other hand, such a significant effect on the pulse generator was not observed in OVX goats. In the second experiment, the animals received a bolus intracerebroventricular injection of several doses (0, 2, 5, and 20 microg/400 microl) of neuropeptide Y (NPY). Exogenous NPY dose-dependently inhibited the pulse generator activity. At the highest dosage, the 1st posttreatment volley interval was significantly longer than that of the pretreatment (112.4 vs. 32.6 min, n = 5, P < 0.01) in OVX goats. The suppressive effect of NPY was similarly observed in OVX+E(2) goats. Further, when NPY was infused (10 microg/200 microl.h for 6 h) into OVX goats, the activity of the GnRH pulse generator was almost completely inhibited during the infusion period. Hypothalamic sites responding to fasting were immunohistochemically evaluated using an antibody for Fos in castrated goats. Fos-immunoreactive neurons were found in areas adjacent to the third ventricle. Double-labeling immunohistochemistry revealed that a subpopulation of NPY neurons in the arcuate nucleus was activated in response to fasting. These results demonstrate that: 1) the activity of the GnRH pulse generator is suppressed by fasting in the presence of E(2); 2) exogenous NPY inhibits the activity of the GnRH pulse generator regardless of the presence of E(2); and 3) several hypothalamic neurons or regions, including those containing NPY in the arcuate nucleus, are activated by fasting. Collectively, these observations suggest that NPY acts as a mediator of undernutrition to the GnRH pulse generator.

Animal Nutritional Physiological Phenomena↗
PubMed2000

New induction of leukotriene A(4) hydrolase by interleukin-4 and interleukin-13 in human polymorphonuclear leukocytes.

Interleukin (IL)-4, IL-10, and IL-13, Th2 cell-derived cytokines, play major roles in the pathophysiology of allergic diseases. These cytokines up-regulate or down-regulate the production of arachidonic acid metabolites. In this study, we have investigated the effect of IL-4, IL-10, IL-13, and other cytokines on A23187-stimulated synthesis of leukotriene (LT) B(4) in human polymorphonuclear leukocytes (PMNs). Production of LTB(4) was measured by specific radioimmunoassay and high performance liquid chromatography. Messenger RNA (mRNA) expression of cytosolic phospholipase A(2) (cPLA(2)), 5-lipoxygenase (5-LO), and LTA(4) hydrolase, which were involved in the synthesis of LTB(4), was determined by reverse transcription-polymerase chain reaction and Northern blot analysis. Protein synthesis of their enzymes was determined by Western blot analysis. IL-4 and IL-13 enhanced A23187-stimulated LTB(4) synthesis and increased mRNA expression and protein synthesis of LTA(4) hydrolase, but not those of cPLA(2) or 5-LO. These results indicate that IL-4 and IL-13 transcriptionally or post-transcriptionally up-regulate the synthesis of LTB(4), a potent chemotactic factor to PMNs, at the enzyme level of LTA(4) hydrolase, and this up-regulation mechanism may participate in the development of allergic inflammation. (Blood. 2000;96:601-609)

Arachidonate 5-Lipoxygenase↗
PubMed2000

(9-[4-acetyl-3-hydroxy-2-n-propylphenoxy) methyl]-3-(1H-tetrazol-5-yl)-4H-pyrido [1,2-a] pyrimidin-4-one), AS-35, inhibits leukotriene synthesis.

AS-35, (9-[4-acetyl-3-hydroxy-2-n-propylphenoxy) methyl]-3-(1H-tetrazol-5-yl)-4H-pyrido[1, 2-a] pyrimidin-4-one), was developed as a leukotriene (LT) receptor antagonist, which also inhibited IgE-mediated release of leukotrienes (LTs). We have investigated the action of AS-35 on the enzyme activities which are involved in the synthesis of LTC(4) and LTB(4) (LT-synthesizing enzymes); cytosolic phospholipase A(2) (cPLA(2)), 5-lipoxygenase (5-LO), leukotriene (LT)C(4) synthase and LTA(4) hydrolase. AS-35 dose-dependently inhibited IgE- and A23187-stimulated production of LTC(4) by up to 71.5-84.8% and that of LTB(4) by 48.3-49.2% at 2. 5x10(-5) M. The assays for cPLA(2)(-), 5-LO-, LTC(4) synthase- and LTA(4) hydrolase-activities revealed that the inhibition is attributable to suppression of cPLA(2), 5-LO and LTC(4) synthase but not LTA(4) hydrolase. We have also studied the action of AS-35 on the release of beta-hexosaminidase (beta-HEX) as a marker of preformed mediators. AS-35 had only weak inhibitory action on the release of beta-HEX. The results indicate that anti-allergic action of AS-35 is predominantly attributable to its inhibition of LT synthesis by suppressing three consecutive enzymes for LTC(4) synthesis.

Animals↗
PubMed2000

Ulinastatin, an elastase inhibitor, inhibits the increased mRNA expression of prostaglandin H2 synthase-type 2 in Kawasaki disease.

Kawasaki disease is an inflammatory disease of unknown cause that causes panvasculitis, including coronary arteritis. Polymorphonucleocytosis in the early stage of the illness suggests the implication of neutrophils in the pathogenesis of the disease. In the acute phase of Kawasaki disease, mRNA expression of prostaglandin H2 synthase (PHS)-2, as determined by reverse transcription-polymerase chain reaction, was markedly enhanced, and thromboxane A2 (TXA2)-synthesizing activity was increased in polymorphonuclear leukocytes (PMNL). This up-regulation of PHS-2 was suppressed by ulinastatin (a neutrophil-elastase inhibitor) treatment. Lipopolysaccharide-induced enhancement of PHS-2 mRNA was also inhibited by therapeutic doses of ulinastatin in vitro by use of PMNL from healthy volunteers. Thus, ulinastatin inhibits arachidonate PHS metabolism by inhibiting new induction of PHS-2 at the mRNA level, which is a novel pharmacologic action of this substance. Ulinastatin treatment is possibly an additional therapeutic approach to Kawasaki disease.

Aspirin↗
PubMed1999

Magnolol inhibits leukotriene synthesis in rat basophilic leukemia-2H3 cells.

We have observed an inhibitory action of magnolol on the production of leukotriene (LT) C4 and LTB4, important lipid mediators in allergy and inflammation. IgE- and A23187-stimulated production of LTC4 and LTB4 was measured by radio-immunoassay (RIA) in the absence or presence of various concentrations of magnolol in intact rat basophilic leukemia (RBL)-2H3 cells. Magnolol dose-dependently inhibited synthesis of LTC4 and LTB4. Magnolol inhibited the IgE-mediated increase of intracellular calcium ion concentration, resulting in the inhibition of cytosolic phospholipase A2 (cPLA2) and possibly 5-lipoxygenase (5-LO), both calcium ion-dependent enzymes. In cell-free studies magnolol inhibited LTC4 synthase activity. LTA4 hydrolase activity was only inhibited at the higher concentration (2.5 x 10(-5)M). These results indicate that magnolol inhibits production of LTs by inhibiting PLA2, 5-LO, LTC4 synthase and LTA4 hydrolase which are essential for LT-synthesis. Magnolol may have anti-allergic effect by blocking LT-synthesis.

Animals↗
PubMed1999

Induction of cytosolic phospholipase A2 and prostaglandin H2 synthase-2 by lipopolysaccharide in human polymorphonuclear leukocytes.

Polymorphonuclear leukocytes (PMNs) produce arachidonic acid (AA) metabolites including thromboxane A2 (TXA2). These cells are the first line of defense against bacterial invasion, which often causes endotoxin shock. TXA2 which plays an important role in the pathogenesis of endotoxin shock is synthesized by three consecutive enzyme activation, cytosolic phospholipase A2 (cPLA2), prostaglandin H2 synthase (PHS type 1 and type 2) and TXA2 synthase. Among them, cPLA2- and PHS-2 activity is known to be transcriptionally and/or posttranscriptionally up-regulated by various bioactive substances including lipopolysaccharide (LPS), a bacterial endotoxin, in many cell types. We investigated the action of LPS on TXA2 synthesis in human PMNs. A23187-stimulated production of thromboxane B2 (TXB2, a stable metabolite of TXA2), assayed by specific radioimmunoassay (RIA), was significantly increased from 566.7+/-44.1 pg/10(6) cells to 966.7+/-44.1 pg/10(6) cells (p<0.05) after 6 h-exposure to LPS at the concentration of 100 ng/ml. Messenger RNA for PHS-2, PHS-1, TXA2 synthase and cPLA2, which was assessed by reverse transcription-polymerase chain reaction (RT-PCR), was expressed in PMNs without LPS stimulation. Although PHS-2 was putatively an inducible enzyme, abundance of mRNA for PHS-2 in PMNs without LPS stimulation was detectable. Messenger RNA abundance for PHS-2 and cPLA2, but not for PHS-1 and TXA2 synthase, was enhanced by LPS-treatment, indicating that the increased production of TXB2 was attributable to the up-regulation of cPLA2 and PHS-2. We conclude that (1) PHS-2 plays a more important role than PHS-1 in the production of TXA2 in human PMNs and (2) TXA2 synthesis in human PMNs is transcriptionally up-regulated by new induction of cPLA2 as well as PHS-2, when the cells encounter endotoxin producing bacteria.

Aspirin↗
PubMed1998

Inhibition of leukotriene synthesis by terfenadine in vitro.

To determine the inhibitory mechanisms of terfenadine on the synthesis of leukotriene C4 (LTC4), an important mediator in allergic diseases, we evaluated the action of terfenadine on the IgE-dependent production of LTC4 in rat basophilic leukaemia 2H3 cells. Rat IgE-loaded cells were stimulated with anti-IgE in the presence or absence of various concentrations of terfenadine and the level of LTC4 released into the medium was measured by performing a specific radio immunoassay. Terfenadine inhibited the synthesis of LTC4 to 67.2% at a concentration of 5 microg/ml. LT synthesis was directly suppressed by inhibition of 5-lipoxygenase (5-LO) through calcium ion-independent mechanisms, and was also possibly suppressed by inhibition of cytosolic phospholipase A2 and 5-LO by blocking the influx of intracellular calcium ion that was initiated by IgE-related stimulation.

Animals↗
PubMed1998

Effect of dexamethasone on leukotriene synthesis in DMSO-stimulated HL-60 cells.

Human leukemia (HL) 60 cells were differentiated by dimethylsulfoxide (DMSO) treatment to granulocyte-like cells, leukotriene (LT) synthesizing activity of which was increased in response to the differentiation of the cells. Four synthesizing enzymes, cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), LTA4 hydrolase and LTC4 synthase, and an enzyme associated protein, 5-lipoxygenase activating protein (FLAP) are involved in the generation of LTC4 and LTB4. We examined the expression of messenger RNA (mRNA) for these LT synthesizing enzymes and an associated protein in DMSO differentiated HL-60 cells by reverse transcriptase polymerase chain reaction (RT-PCR). The production of LTC4 and LTB4, measured by radioimmunoassay (RIA), was increased after the incubation with DMSO for more than 3 days. Messenger RNA abundance for 5-LO, LTC4 synthase and LTA4 hydrolase was increased, that for FLAP was stable, but that for cPLA2 was decreased. These results indicate that DMSO induced increase of LT synthesis is associated with the increase of mRNA expression of 5-LO, LTC4 synthase and LTA4 hydrolase, although the precise regulatory mechanisms of the increased mRNA expression are not determined. We also investigated an action of dexamethasone (DEX) on DMSO-induced enhancement of LT synthesis. DEX suppressed DMSO induced increase of LTC4 synthesis, but rather enhanced DMSO induced LTB4 production. The DEX attenuated the DMSO-induced increase of mRNA expression for LTC4 synthase, but showed no effect on that for LTA4 hydrolase. The inhibition of LTC4 synthesis is associated with the suppression of mRNA expression for LTC4 synthase. However, increased LTB4 synthesis by DEX is regulated by the mechanisms which are independent from mRNA level of LTA4 hydrolase.

5-Lipoxygenase-Activating Proteins↗
PubMed1998

Direct evidence that LTC4 and LTB4 but not TXA2 are involved in asthma attacks in children.

There are substantial numbers of reports showing that leukotrienes (LTs) play important roles in adult asthma. No definite evidence has been demonstrated that LTs are involved in asthma attacks in children, although it is highly expected. In this report, we demonstrated that the levels of LTB4 and LTC4 but not thromboxane B2 (TXB2), a stable metabolite of TXA2, were significantly elevated in the bronchoalveolar lavage fluid, which was obtained from intubated and mechanically ventilated children with severe asthma attacks. This is direct evidence that LTB4 and LTC4 predominantly participate in asthma attacks in pediatric patients.

Adolescent↗
PubMed1998

Factors affecting dimensional instability of alginate impressions during immersion in the fixing and disinfectant solutions.

To clarify the factors determining the dimensional stability of alginate impressions during immersion in disinfectant and fixing solution, the weight change of impressions in solutions of glutaraldehyde (GA), NaClO, Na2SO4, K2SO4, CaCl2, and ZnSO4 was measured. In the nonelectrolytic solution, GA, the weight decreased in proportion to concentration, possibly due to the gradient of osmotic pressure between the impression and solution. In monovalent metallic salt solutions the weight change decreased with increased concentration. Especially at lower concentrations the rate of weight loss was high. A chemical action of the solution might also be involved, in addition to the osmotic pressure difference. The weight loss in divalent metallic salt solutions was greater than in monovalent solutions, implicating crosslinking reactions between the impression and solution.

Alginates↗
PubMed1997

The Chinese herbal medicine, shinpi-to, inhibits IgE-mediated leukotriene synthesis in rat basophilic leukemia-2H3 cells.

We examined the action of Shinpi-To (Formula divinita; TJ-85), a granular extract of seven Chinese medicinal herbs that is used in treating childhood asthma, on the leukotriene synthesis in rat basophilic leukemia-2H3 cells (RBL-2H3 cells). IgE-loaded cells were stimulated with anti-IgE serum in the presence or absence of Shinpi-To. Released LTC4 and LTB4 were measured by radioimmunoassay (RIA). Shinpi-To significantly inhibited IgE-mediated synthesis of leukotriene (LT)C4 and LTB4. To identify the inhibitory sites, we investigated the action of this extract on four synthetic enzymes, phospholipase A2 (PLA2), 5-lipoxygenase (5-LO). LTC4 synthase, and LTA4 hydrolase. Shinpi-To inhibited the A23187-stimulated release of [3H]arachidonic acid (AA) from the cell membrane, reflecting an effect on PLA2 activity. It also suppressed production of LTC4 and LTB4 when cell lysates were incubated with AA as substrate. It did not inhibit the production of LTC4 and LTB4 when LTA4-free acid was used as the substrate. Shinpi-To did not inhibit the IgE-mediated increase of intracellular Ca2+ ([Ca2+]i) concentration. Results indicate that Shinpi-To inhibits LT synthesis by inhibiting PLA2 and 5-LO activities without affecting the mobilization of [Ca2+]i.

Analysis of Variance↗
PubMed1997

Unbalanced production of interleukin-5 and interleukin-2 in children with atopic dermatitis.

BACKGROUND: Cytokines, such as interleukin (IL)-5, produced by T helper type 2 Th2) cells appear to play an important role in the inflammatory processes associated with atopic dermatitis. The roles of cytokines produced by Th1 cells remain controversial. OBJECTIVE: We examined IL-5 and IL-2 mRNA abundance in and protein production by peripheral blood mononuclear cells (PBMCs) from patients with atopic dermatitis and compared those from controls. METHODS: Peripheral blood mononuclear cells were isolated from six children with atopic dermatitis and six control children, and stimulated with both phytohemaggulutinin (PHA) and phorbol 12-myristate 13-acetate (PMA). The abundance of IL-5 and IL-2 mRNA in PBMCs was measured by reverse transcription-polymerase chain reaction analysis. The production of IL-5 and IL-2 by PBMCs was also determined by enzyme-linked immunosorbent assay. RESULTS: After incubation with PHA and PMA, PBMCs from atopic children showed significantly higher IL-5 mRNA abundance (P < .05) and IL-5 production (P < .01), as well as a lower amount of IL-2 mRNA (P = .056) and IL-2 production (P < .05) than those from healthy controls. The time course of changes in IL-5 mRNA abundance induced by PHA and PMA in PBMCs from atopic children differed markedly from that observed with healthy controls, whereas the time course of changes in IL-2 mRNA abundance were similar between the two groups. CONCLUSIONS: The increased IL-5 and decreased IL-2 production observed with PBMCs from children with atopic dermatitis may underlie the activation of eosinophils and high serum immunoglobulin E concentrations also apparent in such individuals. An imbalance in the number and activity of Th1 and Th2 cells is likely to be responsible for the abnormal pattern of cytokine production in atopic dermatitis.

Adolescent↗
PubMed1996

Inhibition of leukotriene synthesis by azelastine.

BACKGROUND: Azelastine, oxatomide, and ketotifen are used for patients with allergic diseases. These drugs inhibit the release of chemical mediators including the leukotrienes; however, the mechanism involved is unclear. OBJECTIVE: To clarify the mechanism of inhibition, we investigated the effects of three drugs on the function of phospholipase A2, 5-lipoxygenase, leukotriene C4 synthase, and leukotriene A4 hydrolase, which are all catabolic enzymes involved in synthesizing leukotriene C4 and leukotriene B4 in rat basophilic leukemia (RBL)-1 cells. METHODS AND RESULTS: The production of leukotriene C4 and leukotriene B4 was measured by high performance liquid chromatography (HPLC). All three drugs inhibited the production of leukotriene C4 and leukotriene B4 when cells were stimulated with A23187. All three drugs also inhibited the A23187-stimulated release of 3H-arachidonic acid from membrane phospholipids. Azelastine inhibited the production of leukotriene C4, but not leukotriene B4, when either arachidonic acid or leukotriene A4 free acid was used as the substrate in our cell free system. Oxatomide and ketotifen did not inhibit the synthesis of either leukotriene C4 or leukotriene B4 in the same cell free study. CONCLUSION: Results indicated that oxatomide and ketotifen inhibit the production of leukotriene C4 and leukotriene B4 by inhibiting phospholipase A2 activity, whereas, azelastine inhibits the leukotriene C4 production by inhibiting phospholipase A2 and leukotriene C4 synthase.

Animals↗
PubMed1996

Primary gastrointestinal T-cell lymphoma resembling multiple lymphomatous polyposis.

An extremely rare case of primary gastrointestinal T-cell lymphoma involving the stomach and intestine is reported. Radiographic and endoscopic examinations showed multiple polypoid lesions covered by a normal-appearing mucosa in the stomach, duodenal bulb, and terminal ileum and numerous small aphthoid lesions throughout the entire colorectum. Histopathologic, immunohistochemical, and polymerase chain reaction studies were performed using paraffin-embedded or fresh-frozen specimens from endoscopic biopsies and endoscopic mucosal resections. All lesions were composed of small, atypical lymphoid cells, which were classified as low-grade pleomorphic lymphoma. The tumor cells expressed CD3, CD4, and the T-cell receptor gamma gene phenotype as well as human mucosal lymphocyte 1 antigen, suggesting that the lymphoma cells were derived from intraepithelial T lymphocytes. This is the first description of primary gastrointestinal T-cell lymphoma with expression of human mucosal lymphocyte 1 antigen and a novel morphology resembling multiple lymphomatous polyposis.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Inhibition of leukotriene synthesis by honokiol in rat basophilic leukemia cells.

The effects of honokiol, a diphenyl compound extracted from a Chinese herbal medicine, on leukotriene (LT) synthesis were evaluated in rat basophilic leukemia (RBL) cells. The production of LTC4 and LTB4 stimulated by the Ca2+ ionophore A23187 was measured in RBL-1 cells by high-performance liquid chromatography. Honokiol inhibited the production of LTC4 and LTB4 stimulated by A23187 in RBL-1 cells. Honokiol did not inhibit either phospholipase A2 activity, measured by the release of 3H-arachidonic acid (AA), or LTC4 synthase and LTA4 hydrolase activities, measured with LTA4-free acid as substrate. The synthesis of LTC4 and LTB4 from AA in RBL-1 cell lysates in the presence of Ca2+ was inhibited by honokiol. These results indicate that honokiol blocks LT synthesis by inhibiting 5-lipoxygenase activity. Honokiol also inhibited immunoglobulin E-mediated production of these LTs in RBL-2H3 cells, which was measured by a specific radioimmunoassay (RIA). These results suggest that honokiol may exhibit antiallergic actions by inhibiting LT synthesis in immediate-type hyperreactivity.

Animals↗