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Biomedical subjects

J Tamaoki

Publications and source records attributed to J Tamaoki.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Effect of heparin on the increase in intracellular calcium caused by inositol 1,4,5-triphosphate in airway epithelial cells].

We studied the effect of heparin on the inositol 1,4,5-triphosphate (IP3)-dependent increase in intracellular calcium (Ca2+) caused by ATP. The Ca2+ concentration ([Ca2+]i) in cultured epithelial cells from cow tracheas was measured by the fura-2 method. ATP (10(-4) M) stimulated IP3 production and caused a biphasic increase in [Ca2+]i a transient response and a subsequent sustained response. Heparin (l 100 U/ml) dose-dependently inhibited the ATP-induced increase in [Ca2+]i but had no effect on IP3 production. Dextran sulfate, a polysaccharide with negative charge density, had a similar inhibitory effect on the ATP-induced increase in [Ca2+]i. These data suggest that heparin inhibits intracellular Ca2+ mobilization by acting at a site "distal to" IP3 production, and that the mechanism of action of heparin may be related to its negative charge.

Adenosine Triphosphate↗
PubMed1997

Stimulation of airway mucociliary transport and epithelial ciliary motility by the triazolopyridazin derivative TAK-225.

To elucidate whether a newly developed antiallergic drug, the triazolopyridazin derivative TAK-225, alters airway mucociliary clearance and, if so, what the mechanism of action is, we measured mucociliary transport in the rabbit tracheal mucosa ex vivo and ciliary motility of the tracheal epithelium in vitro. Mucociliary transport function was determined by the transport rate of Evans blue dye that had been placed on the mucosal surface above the carina. Oral administration of TAK-225 (0.3-30 mg/kg) increased Evans blue transport toward the larynx in a dose-dependent manner. Addition of TAK-225 caused a rapid and sustained increase in the ciliary beat frequency of tracheal epithelium, as assessed by photoelectric method; the maximal increase from the base-line value was 25.1 +/- 4.6% (P < .01), and the concentration required to produce a half-maximal effect (EC50) was 3.1 +/- 0.8 x 10(-7) M. This effect was greatly attenuated by pretreatment with the cAMP antagonist adenosine 3',5'-cyclic monophosphorothioate, but not by Ca++-free medium containing ethylene glycol-bis [3-aminoethyl ether] N,N,N',N'-tetraacetic acid and [1,2-bis(2)aminophenoxy]ethane N,N,N',N'-tetraacetic acid-acetomethoxy ester. Incubation of tracheal epithelium with TAK-225 increased intracellular cAMP contents in a concentration-dependent manner. These results suggest that TAK-225 enhances airway mucociliary clearance probably through cAMP-mediated stimulation of ciliary motility of airway epithelium.

Animals↗
PubMed1997

[Role of neutrophil elastase in allergen-induced airway microvascular leakage in sensitized guinea pigs].

To determine the role of neutrophil elastase in allergen-induced airway microvascular leakage, we assessed vascular permeability of guinea pig trachea by measuring the extravasation of Evans blue dye in the circulating blood. Inhalation of ovalbumin (OA) to guinea pigs sensitized with OA caused Evans blue extravasation, indicating an increased microvascular permeability. Pretreatment with ONO-5046 a specific inhibitor of neutrophil elastase, inhibited OA-induced vascular leakage in a dose-dependent manner. Tracheal instillation of human neutrophil elastase likewise increased microvascular permeability, and this effect was almost completely abolished by ONO-5046. Challenge with OA increased the number of neutrophils and neutrophil elastase activity in the bronchoalveolar lavage fluid, and these effects were inhibited by ONO-5046. These results suggest that neutrophil accumulation into the airway and the subsequent release of neutrophil elastase may play a role in the airway microvascular leakage produced by antigen challenge.

Animals↗
PubMed1997

5-Hydroxytryptamine inhibits Na absorption and stimulates Cl secretion across canine tracheal epithelial sheets.

BACKGROUND: 5-Hydroxytryptamine (5-HT) can be released from mast cells and platelets through an IgE-dependent mechanism and may play a role in the pathogenesis of allergic bronchoconstriction. However, the effect of 5-HT on ion transport by airway epithelium remains uncertain. OBJECTIVE: To determine whether 5-HT alters electrical and ion transport properties of Cl-secreting epithelia and, if so, what subtype of 5-HT receptors is involved, we studied canine tracheal epithelium under short-circuit conditions in vitro. METHODS: Canine tracheal mucosa was mounted in Lucite half-chambers and the responses of short-circuit current (lsc), transepithelial potential difference (PD) and tissue conductance (G) were measured. In addition, ion fluxes were directly measured using 22Na and 36Cl. RESULTS: Mucosal addition of 5-HT caused a rapid increase in lsc, which was accompanied by the increases in PD and G, whereas submucosal 5-HT had no effect. In the presence of amiloride, 5-HT and its receptor agonists dose-dependently increased lsc, with the rank order of potency being 5-HT > alpha-methyl-5-HT > 2-methyl-5HT > 5-carboxamidotryptamine. The effect of 5-HT was inhibited by ketanserin and spiperone but not by ondansetron. 5-HT increased Cl flux from the submucosa to the mucosa with a slight inhibition of Na flux to the opposite direction. CONCLUSION: 5-HT inhibits airway epithelial Na absorption and stimulates Cl secretion. The latter action predominates the former and is mediated by 5-HT2 receptors. These effects may result in the increase in water movement toward the airway lumen.

Amiloride↗
PubMed1997

Role of the sarcolemmal sodium pump in nitroprusside-induced vasodilation of the pulmonary artery.

To elucidate the mechanism of nitrovasodilator-induced pulmonary vasodilation, we examined the role of sodium pump and K+ channels in the relaxant responses of canine pulmonary arterial rings to sodium nitroprusside (SNP) under isometric conditions in vitro. Pretreatment with the sodium pump inhibitor ouabain attenuated the SNP-induced vasodilation of KCI-contracted tissues, so that the maximal relaxation decreased from 90 +/- 7 to 62 +/- 6% (P < 0.01), and the negative logarithm of SNP concentration required to produce a half-maximal effect (pD2) decreased from 5.9 +/- 0.4 to 5.1 +/- 0.4 (P < 0.01). This effect was not altered by mechanical removal of the endothelium. In contrast, pretreatment with K+ channel blockers including iberiotoxin, apamin and glibenclamide did not change the relaxant responses to SNP. Incubation of endothelium-denuded rings with SNP increased ouabain-sensitive 86Rb uptake in a dose-dependent manner, an effect that was inhibited by KT 5823, a cGMP-dependent protein kinase inhibitor. These results suggest that activation of sarcolemmal sodium pump may be involved in the nitrovasodilator-induced cGMP-mediated pulmonary vasodilation, whereas K+ channels may play a less important role in this action.

Animals↗
PubMed1997

Inhaled cromoglycate reduces airway neurogenic inflammation via tachykinin antagonism.

To determine whether sodium cromoglycate (SCG) inhibits airway neurogenic inflammation and, if so, to elucidate the mechanism of its action, we studied plasma extravasation evoked by hypertonic saline in the rat trachea by measuring the amount of extravasated Evans blue dye. Inhalation of hypertonic saline (5-15% NaCl) produced microvascular leakage, an effect that was reduced by pretreatment with SCG in a dose-dependent manner. Inhaled SCG (10 mg/ml) for 2 min did not affect the basal vascular permeability, but significantly inhibited the 10% NaCl-induced plasma extravasation by 34%. SCG likewise inhibited the responses of microvascular leakage to substance P aerosols, whereas it was without effect on those to platelet activating factor aerosols. These results suggest that SCG inhibits airway neurogenic inflammation presumably via functional antagonism of tachykinins, and that this novel effect may be involved in the therapeutic efficacy of SCG in the treatment of airway inflammatory diseases including asthma.

Administration, Inhalation↗
PubMed1996

Effect of ciprofloxacin on ciliary motility of rabbit airway epithelium.

To determine the effect of the new quinolone ciprofloxacin on airway ciliary motility, we studied ciliary beat frequency (CBF) of rabbit tracheal epithelium using an in-vitro microphoto-oscillation method. Incubation of the cells with ciprofloxacin increased CBF in a concentration-dependent manner, the maximal increase from the baseline value and the EC50 being 17.1 +/- 2.0% (P < 0.01) and 10(-7.25) M, respectively. This ciliary stimulatory effect was not affected by propranolol or indomethacin but was nullified by verapamil. These results suggest that ciprofloxacin probably increases airway epithelial ciliary motility by facilitating Ca2+ influx through a voltage-dependent channel.

Animals↗
PubMed1996

[Effect of macrolide antibiotics on airway goblet hypersecretion in guinea pigs].

Although macrolide antibiotics have now been widely used in the treatment of chronic airway infections including diffuse panbronchiolitis and chronic bronchitis, the mechanism of the efficacy remains uncertain. Because the increased mucus glycoprotein secretion from airway goblet cells may play a significant role in the development of such diseases, to determine the effects of macrolides on airway goblet cell secretion, we studied guinea pig airways by a semiquantitative morphometric method. The goblet cell secretion was assessed in histological sections of the trachea and main bronchi stained with Alcian blue and PAS by determining mucus score, which is inversely related to the magnitude of mucus discharge. Intravenous IL-8 decreased mucus score in a dose-dependent manner and increased the number of neutrophils present in bronchoalveolar lavage fluid. Oral administration of clarithromycin at a daily dose of 1-10 mg/day for 2 weeks dose-dependently inhibited IL-8 (5 mg/ kg)-induced decrease in mucus score, with the maximal inhibition being 54 +/- 11% (p < 0.001) in the trachea and 48 +/- 8% (p < 0.01) in the main bronchi. This effect was accompanied by the inhibition of neutrophil accumulation into bronchoalveolar lavage fluid. Erythromycin produced similar inhibitory effects on IL-8-induced goblet cell secretion and neutrophil accumulation, whereas amoxicillin and cefaclor had no effect. These results suggest that macrolides protect against goblet cell hypersecretion probably through an inhibition of recruitment of neutrophils into the airway mucosa.

Animals↗
PubMed1996

Effects of roxithromycin and erythromycin on interleukin 8-induced neutrophil recruitment and goblet cell secretion in guinea pig tracheas.

Inhaled interleukin 8 caused an increase in goblet cell secretion in guinea pig tracheas, which was accompanied by mucosal infiltration of neutrophils. These responses were inhibited by pretreatment with roxithromycin or erythromycin in a dose-dependent fashion. Macrolides may thus be a value in protecting against neutrophil-associated airway hypersecretion.

Animals↗
PubMed1996

Hypoxia impairs nitrovasodilator-induced pulmonary vasodilation: role of Na-K-ATPase activity.

To elucidate the effect of hypoxia on nitrovasodilator-induced pulmonary vasodilation, we studied canine pulmonary arterial rings under isometric conditions in vitro. Exposure to hypoxia inhibited the relaxant responses of KCl-contracted tissues to sodium nitroprusside (SNP), so that the maximal relaxation (Emax) and the negative logarithm of molar concentration required to produce 50% relaxation (pD2) were decreased from 92 +/- 7 to 62 +/- 5% and from 5.8 +/- 0.2 to 4.7 +/- 0.3, respectively (means +/- SE, P < 0.01 for each). This effect was likewise observed when 8-bromoguanosine-3',5'-cyclic monophosphate was used as a relaxant. The impairment of SNP-induced relaxation of endothelium-denuded rings under hypoxia was abolished by ouabain or K(+)-free solution. Incubation with SNPincreased intracellular cGMP contents in a dose dependent manner, an effect that was not altered by hypoxia. SNP also increased ouabain-sensitive 86Rb uptake, and this effect was inhibited by hypoxia. These results suggest that hypoxia reduces nitrovasodilator-induced relaxation of pulmonary artery, probably through an inhibition of cGMP-dependent sarcolemmal Na-K-adenosine triphosphatase activity.

Animals↗
PubMed1996

Effect of oxitropium bromide on histamine-induced airway goblet cell secretion.

To determine whether histamine affects airway goblet cell secretion and, if so, whether cholinergic mechanism is involved, we studied guinea pig airways by a semiquantitative morphometric method. The goblet cell secretion was assessed in histologic sections of the tracheal mucosa stained with Alcian blue and periodic acid-Schiff (PAS) by determining the mucus score, which is inversely related to the magnitude of mucus discharge. Inhaled or intravenously administrated histamine dose dependently decreased the mucus score, an effect that was similarly observed in cartilaginous and muscular portions. Inhalation of the anticholinergic agent oxitropium bromide at doses of 1.5 micrograms and higher greatly attenuated the decrease in mucus score produced by intravenous histamine but not by inhaled histamine. Likewise, cutting of bilateral vagus nerves or atropine abolished intravenous histamine-induced goblet cell secretion. The response of the mucus score to inhaled histamine was abolished by cimetidine, whereas the response to intravenous histamine was reduced by mepyramine but not by cimetidine or thioperamide. These results suggest that inhaled histamine increases airway goblet secretion, probably by stimulating histamine H2-receptors on goblet cells, and that intravenous histamine produces a similar effect through a stimulation of histamine H1-receptor-mediated release of acetylcholine from cholinergic nerve terminals, presumably involving vagal reflex.

Administration, Inhalation↗
PubMed1996

Cholinergic control of rabbit tracheal transepithelial potential difference in vivo.

The aim of the present study was to investigate the role of the autonomic nervous system in the regulation of airway epithelial ion transport in vivo. Rabbits were anaesthetized and mechanically-ventilated through a cannula inserted above the carina. The upper tracheal mucosa was exposed, and the electrical potential difference (PD) between the mucosal surface and the submucosal space was continuously measured by a high-impedance voltmeter under open-circuit conditions. Perfusion of the mucosa with atropine caused a rapid decline in PD from -20.1+/-2.0 to -15.2+/-0.9 mV (p<0.01), whereas phentolamine, propranolol, or the tachykinin antagonist, FK224, had no effect. Cutting both cervical vagus nerves decreased PD to the same degree as did atropine. Exogenously applied acetylcholine increased PD in a dose-dependent manner. Topical application of ipratropium bromide reduced the baseline value PD in a dose-dependent manner. The maximal decrease in PD was 43 +/- 0.3 mV (p<0.01), and the dose required to produce a half-maximal effect was 34 microg. Perfusion with either amiloride, a Na channel blocker, and diphenylamine-2-carboxylate, a Cl channel blocker, decreased the baseline PD, and the subsequent application of ipratropium bromide further decreased the PD in each case. We conclude that a cholinergic neural component may play a role in the generation of tracheal potential difference in vivo, probably involving stimulation by endogenously released acetylcholine of both Cl secretion and Na absorption across the airway epithelium.

Acetylcholine↗
PubMed1996

[T-kinin-induced increase in airway vascular permeability and its modulation by angiotensin-converting enzyme].

We studied the effect of T-kinin on airway vascular permeability and its modulation by endogenous peptidases in anesthetized rats in vivo, Vascular permeability was assessed by photometric measurement of extravasated Evans blue dye after formamide extraction. Intravenous injection of T-kinin increased dye extravasation in the trachea and main bronchi in a dose-dependent manner. Plasma extravasation evoked by T-kinin was inhibited by Hoe 140, a B2 receptor but-not by des Arg9-Leu8-bradykinin, a B1 receptor antagonist. Treatment with captopril, an angiotensin-converting enzyme inhibitor, potentiated the T-kinin-induced plasma extravasation, whereas phosphoramidon, a neutral endopeptidase inhibitor, had no effect. These results suggest that T-kinin increases airway vascular permeability via stimulation of B2 receptors, and that this effect is modulated by endogenous angiotensin-converting enzyme.

Animals↗
PubMed1996

[Regulation of cyclooxygenase activity in airway epithelium by endogenous nitric oxide].

The role of nitric oxide (NO) in the activity of cyclooxygenase (COX) in cultured canine tracheal epithelium was studied. Tracheal epithelium spontaneously released prostaglandin E2 (PGE2), which is a product of COX. The release of PGE2 was increased by bradykinin and was decreased by two NO synthase inhibitors: NG-nitro-L-arginine methyl ester and NG-monomethyl-L-arginine. That decrease was reversed in the presence of L-arginine. Chrolpromadin, but not aminoguanidine, inhibited PGE2 production, which suggests that constitutive NO synthase is involved. Two stable NO donors, sodium nitroprusside and S-nitroso-N-acetyl DL-penicillamine, also increased the production of PGE2. These effects were abolished by coincubation with hemoglobin, which binds and inactivates NO, but not by methylene blue, an inhibitor of soluble guanylate cyclase. NADPH diaphorase histochemistry of cultured tracheal cells revealed activity in the periphery of the cytoplasm. These results suggest that, in cultured canine tracheal epithelium, NO directly interacts with COX to regulate PGE2 production.

Animals↗
PubMed1996

Effect of 5-hydroxytryptamine on bioelectric properties of airway epithelial cells in culture.

To elucidate whether 5-hydroxytryptamine (5-HT) affects airway epithelial electrolyte transport and, if so, what the mechanism of action is, we studied the bioelectric properties of canine cultured tracheal epithelium under short-circuit conditions in vitro. Mucosal addition of 5-HT dose-dependently increased short-circuit current (Isc), which was accompanied by increases in transepithelial potential difference and cell conductance. In contrast, 5-HT had no effect on bioelectric properties when it was added to the submucosal side. Pretreatment of cells with amiloride potentiated the increase in Isc produced by 5-HT. In the presence of diphenylamine-2-carboxylate or Cl-free medium, 5-HT decreased Isc from the baseline level. Incubation with BAPTA-AM but not dibutyryl cAMP greatly attenuated the 5-HT-induced increase in amiloride-insensitive portion of Isc. These results suggest that 5-HT inhibits Na absorption and stimulates Cl secretion across canine tracheal epithelium and that the Cl secretion may be associated with elevation of intracellular Ca2+ contents.

Amiloride↗
PubMed1996

[Effect of sodium cromoglycate on airway vascular leakage caused by hypertonic saline in the rat trachea].

The action of the anti-asthmatic drug sodium cromoglycate (SCG) on airway inflammation remains uncertain. Using Evans blue dye as a maker of plasma leakage, we studied the effect of SCG on neurogenic vascular extravasation evoked by hypertonic saline (HTS) in the rat trachea. Inhalation of HTS (5-15%) caused a concentration-dependent increase in plasma leakage, but inhaled 0.9% NaCl had no effect. Inhalation of SCG did not affect the baseline level of vascular permeability, but it inhibited the effect of HTS in a dose-dependent manner: plasma extravasation induced by 10% NaCl was significantly reduced by 2 minutes of inhalation of SCG at concentrations of 10 and 50 mg/ml (p < 0.05 and p < 0.01, respectively). SCG (10 mg/ml), also inhibited the changes in microvascular permeability caused by aerosols of substance P (10(-4) M), whereas it did not affect the responses to aerosols of platelet-activating factor (3 x 10(-4) M). A similar dose of SCG did not significantly alter microvascular leakage caused by 5% NaCl. However, phosphoramidon, a selective inhibitor of neutral endopeptidase, potentiated the response to 5% NaCl, an effect that was inhibited by SCG (p < 0.05). These results suggest that SCG inhibits HTS-induced airway vascular permeability, presumably through a tachykinin-antagonist-like property, and that this inhibition is exaggerated when the activity of endogenous neutral endopeptidase is low.

Animals↗