Biomedical subjects

Atsushi Tachibana

Publications and source records attributed to Atsushi Tachibana.

11 recordsLinked to original sources

PubMed2005

Differential role of an atypical protein kinase C, PKC zeta, in regulation of human eosinophil and neutrophil functions.

BACKGROUND: Protein kinase C (PKC) comprises a family of isoenzymes playing a key role in downstream signaling and cell functions. PKCs are grouped according to molecular structure and mode of activation: 'conventional' PKCs (alpha, betaI, betaII, gamma), 'novel' PKCs (delta, epsilon, mu, theta, eta), and 'atypical' PKCs (zeta, tau/lambda). Here we compared the influence of PKC zeta on the function of human eosinophils and neutrophils. METHODS: After pretreating the cells with a myristoylated specific PKC zeta inhibitor, a myristoylated PKC eta inhibitor, or bisindolylmaleimide I (Bis I; an inhibitor of conventional and novel PKCs), we examined N-formyl-methionyl-leucyl-phenylalanine (FMLP)- or 4-phorbol 12-myristate 13-acetate (PMA)-evoked superoxide anion (O(2)(-)) generation. Induced PKC translocation was characterized using confocal laser scanning microscopy. RESULTS: The PKC zeta inhibitor significantly blocked FMLP- or PMA-induced O(2)(-) generation by eosinophils. However, this inhibitor attenuated PMA- but not FMLP-induced O(2)(-) generation by neutrophils. In contrast, Bis I inhibited FMLP-induced O(2)(-) generation by eosinophils and neutrophils in a similar manner. The PKC eta inhibitor had no significant effect, since both cell types lack PKC eta; this confirmed specificity of PKC zeta inhibitor effects. Finally, the translocation of PKC zeta to the plasma membrane induced by FMLP in both eosinophils and neutrophils was started at 1 min while the translocation was maintained for 15 min in eosinophils but not in neutrophils. CONCLUSION: An atypical PKC, PKC zeta, regulates human eosinophil and neutrophil functions in a differential manner.

Cell Movement↗

PubMed2005

An atypical protein kinase C, PKC zeta, regulates human eosinophil effector functions.

Protein kinase (PK) C comprises a family of isoenzymes that play key roles in downstream signalling and cell functions. We studied PKC zeta participation in the effector functions of human eosinophils stimulated with platelet-activating factor (PAF) or complement (C) 5a. After pretreating eosinophils with a myristoylated specific PKC zeta inhibitor; bisindlolylmaleimide I (BisI), an inhibitor of conventional and novel PKCs; or rottlerin, a PKC delta inhibitor, we examined PAF- and C5a-evoked functions. Induced PKC translocation was characterized by confocal laser scanning microscopy. The PKC zeta inhibitor blocked PAF- or C5a-induced eosinophil superoxide anion generation as effectively as BisI or rottlerin. The PKC zeta inhibitor also attenuated PAF- or C5a-induced eosinophil degranulation and adhesion. In contrast, the PKC zeta inhibitor did not affect PAF- or C5a-induced CD11b expression. Finally, both eosinophil shape changes and the translocation of PKC zeta and p47phox, a component of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, to the plasma membrane induced by PAF or C5a were completely inhibited by the PKC inhibitor. Thus, the atypical PKC zeta regulates human eosinophil adhesion and effector functions.

CD11b Antigen↗

PubMed2004

Stereoselective [3,3]-sigmatropic rearrangement promoted by the metal [1,3]-shift of binuclear Fischer carbene complexes.

Reaction of chiral homobinuclear Fischer chromium carbene complexes with allyl alcohol in the presence of NaH and the following oxidative demetalation gave alpha-allyl esters in up to 97% ee via [3,3]-sigmatropic rearrangement reaction promoted by the metal 1,3-shift. On the other hand, chiral heterobinuclear tungsten carbene complexes with arene chromium complexes afforded alpha-allyl-beta-hydroxy esters as a major product in up to 92/8 dr by the same reaction sequence.

Journal Article↗

PubMed2004

Dual signaling and effector pathways mediate human eosinophil activation by platelet-activating factor.

Platelet-activating factor (PAF) induces various cellular functions in eosinophils including chemotaxis, adhesion, superoxide anion (O2-) production, and degranulation. While PAF shares many biological effects with other chemotactic factors such as N-formyl-methionyl-leucyl-phenylalanine, complement fragments, and lipid mediators, PAF is unique in that its action is relatively resistant to pertussis toxin (PTX), and in activating eosinophils more strongly than neutrophils. In this review we consider how PAF might activate human eosinophils in preference to neutrophils, and discuss possible mechanisms of PAF-induced activation of human eosinophils via two distinct signaling and effector pathways. Recently we analyzed O2- production by eosinophils using a sensitive, real-time chemiluminescence method. Our results showed that in human eosinophils PAF activates two distinct signaling and effector pathways coupled to the PAF receptor: one linked to PTX-sensitive G protein(s) and another to PTX-resistant G protein(s), phosphatidylinositol 3-kinase, and cellular adhesion. This activation of two different G proteins by the eosinophil PAF receptor may explain the strong and diverse biological responses of human eosinophils to PAF.

Animals↗

PubMed2003

Distinct isoforms of protein kinase C are involved in human eosinophil functions induced by platelet-activating factor.

BACKGROUND: Platelet-activating factor (PAF) is a potent stimulator of eosinophils. Recently, treatment with a protein kinase C (PKC) inhibitor which generally inhibits PKC isoforms has been shown to modulate several eosinophil functions in distinct manners, in that PKC inhibition enhanced CD11b expression and cellular adhesion, but inhibited superoxide generation and degranulation in PAF-stimulated human eosinophils. These results suggested that distinct PKC isoforms were likely to be involved in each eosinophil function induced by PAF. We have therefore investigated whether or not the PKC isoforms involved in PAF-induced CD11b expression and superoxide generation were different. METHODS: Human eosinophils prepared from healthy volunteers were treated with PKC inhibitors, bis-indolylmaleimide I (BisI; a general PKC inhibitor), myristoylated PKC inhibitor peptide (myr-psiPKC; a PKCalpha, beta and delta inhibitor) and rottlerin (a PKCdelta inhibitor), followed by stimulation with PAF. CD11b expression was determined using flow cytometry and superoxide generation was evaluated using a cytochrome c reduction assay. RESULTS: BisI treatment led to enhancement of PAF-induced CD11b expression, while myr-psiPKC and rottlerin did not. In contrast, PAF-induced superoxide generation was inhibited by treatment with BisI, myr-psiPKC and rottlerin. CONCLUSIONS: PKCalpha, beta and delta are not involved in PAF-induced CD11b expression, but PKCdelta is involved in the PAF-induced activation of superoxide anion generation.

Acetophenones↗

PubMed2002

Platelet-activating factor activates two distinct effector pathways in human eosinophils.

In granulocytes, platelet-activating factor (PAF) shares many of its biological effects with other chemotactic factors, such as FMLP, complement fragments, and lipid mediators. Two unique effects are that PAF is relatively resistant to pertussis toxin (PTX) and that PAF activates the inflammatory functions of eosinophils more strongly than it activates those of neutrophils. To investigate the molecular mechanisms of the responses of eosinophils to PAF, we analyzed superoxide anion production by a chemiluminescence method that provides real-time kinetic data for the cellular responses. We found that PAF induced bimodal superoxide anion production in human eosinophils, consisting of an intense, but transient, first phase and a larger and sustained second phase. In contrast, PAF induced essentially a transient unimodal response in human neutrophils. The two phases of eosinophil response were mediated by distinct cellular mechanisms: the second phase was highly dependent on cellular adhesion and beta(2) integrins, but the first phase was independent of both adhesion and beta(2) integrins. The upstream signaling mechanisms were also different: the second phase was mediated by PTX-resistant G-protein(s) and through activation of phosphatidylinositol 3-kinase, while the first phase was mediated by PTX-sensitive G-protein(s). Furthermore, the second-phase response was approximately 100-fold more resistant to inhibition by a competitive PAF receptor antagonist than the first phase. Thus, eosinophils and neutrophils react differently to PAF, and PAF activates two separate and distinct effector pathways in human eosinophils. These two activation pathways may explain the eosinophils' strong and diverse biological responses to PAF.

Eosinophils↗

PubMed2002

Cellular adhesion is required for effector functions of human eosinophils via G-protein coupled receptors.

BACKGROUND: Eosinophils play an important role in the pathogenesis of allergic diseases. Chemoattractants, including platelet-activating factor (PAF) and complement component 5a (C5a), induce eosinophil infiltration and promote eosinophil effector functions. OBJECTIVE: To compare eosinophil degranulation and superoxide anion (O2-) generation induced by various chemoattractants, and to elucidate the role of cellular adhesion on these effector functions. METHODS: Human eosinophils were stimulated with PAF, C5a, eotaxin, or leukotriene B4 (LTB4). O2- generation was assayed by a chemiluminescence method using a Cypridina luciferin analog as the amplifier. Degranulation and adhesion were measured by quantitating eosinophil protein X by radioimmunoassay. Expression of CD11b on eosinophils was measured by flow cytometry. RESULTS: PAF and C5a induced significant degranulation and O2- generation from eosinophils. In contrast, the potency of eotaxin or LTB4 for these functions was much less. PAF and C5a also significantly enhanced eosinophil adhesion, whereas eotaxin and LTB4 did not. CD11b expression on eosinophils was enhanced by all four stimulants, and the order of potency to induce CD11b expression was C5a > PAF > eotaxin > LTB4. CONCLUSIONS: The potency of PAF and C5a for inducing effector function in eosinophils was greater than that of eotaxin or LTB4. The magnitude of the effector function was consistent with the degree of eosinophil adherence induced by each stimulant. These results suggest that effector functions of eosinophils which are mediated through G-protein coupled receptors are dependent on cellular adhesion.

Cell Adhesion↗

PubMed2002

Fenoterol inhibits superoxide anion generation by human polymorphonuclear leukocytes via beta-adrenoceptor-dependent and -independent mechanisms.

BACKGROUND: Beta2-adrenoceptor agonists, used widely as bronchodilator in treating bronchial asthma, may have anti-inflammatory activity. OBJECTIVE: We examined whether various widely prescribed beta2-adrenoceptor agonists differ in anti-inflammatory mechanisms. METHODS: We investigated effects of these drugs on superoxide anion generation by stimulated human polymorphonuclear leukocytes in vitro using chemiluminescence. RESULTS: At high concentrations, fenoterol significantly inhibited both N-formylmethionyl-leucyl-phenylalanine- and phorbol myristate acetate-induced superoxide generation by neutrophils. In contrast, salbutamol or procaterol partially inhibited generation with the former stimulus but not the latter. Inhibition by salbutamol or procaterol was completely reversed by either propranolol, a nonselective beta-adrenoceptor antagonist, or ICI-118551, a beta2-adrenoceptor-selective antagonist. In contrast, the effect of fenoterol at concentrations exceeding 10(-6) M against superoxide generation with the former stimulus was only partially reversed by antagonists, and the effect of high concentrations of fenoterol against generation with the latter stimulus was not reversed. No drugs scavenged superoxide at the highest concentration used (10(-5) M). CONCLUSIONS: Fenoterol at high concentrations has an inhibitory effect on superoxide generation that includes a component not mediated via beta2-adrenoceptors. Direct inhibition at or downstream from protein kinase C may be involved.

Adrenergic beta-Agonists↗

PubMed2002

Prevalence of gastro-esophageal reflux-related symptoms in Japanese infants.

BACKGROUND: To obtain precise information on the natural course of gastro-esophageal reflux (GER)-related symptoms in Japanese children, we surveyed the prevalence of regurgitation or vomiting and other GER-related symptoms and complications in infants visiting for healthy baby check-ups. METHODS: We interviewed the mothers of 921 infants who had visited for baby check-ups at 1, 4, 7 and 12 months after birth, about the number of regurgitation or vomiting episodes per day, other GER-related symptoms, milk volume, feeding interval, and the body position after feeding. RESULTS: Of 1-month-old infants, 47.1% had one or more regurgitation or vomiting episode per day. This proportion decreased to 28.8% at 4 months old and 6.4% at 7 months old. The proportion of infants with three or more episodes of these symptoms per day showed a similar pattern. There was no significant difference in the prevalence of regurgitation or vomiting between breast-fed infants and formula-fed or mixed-feeding infants either at 1 or 4 months of age. There was no significant difference in the bodyweight gain of 3-month-old infants among those with various degrees of regurgitation. There was no significant difference in the frequency of regurgitation or vomiting episodes between infants placed in a vertical position and those placed in a horizontal position after feeding. No infant had a history of chronic coughing, wheezing, bleeding or other serious conditions. CONCLUSIONS: Regurgitation is a common symptom in Japanese infants and decreases spontaneously with age. The natural history of GER must be taken into consideration when deciding the treatment.

Female↗

PubMed2002

Inhibition of protein kinases A and C demonstrates dual modes of response in human eosinophils stimulated with platelet-activating factor.

BACKGROUND: Platelet-activating factor (PAF) is a potent stimulator of human eosinophils involved in the pathogenesis of allergic diseases. However, intracellular signaling mechanisms in eosinophils involving the PAF receptor are incompletely understood. OBJECTIVE: We sought to determine the roles of protein kinase C (PKC) and cyclic AMP-dependent protein kinase (protein kinase A [PKA]) in signaling pathways of human eosinophils stimulated with PAF. METHODS: After pretreatment with a PKC inhibitor, bisindolylmaleimide I, or a PKA inhibitor, H89, we investigated PAF-evoked functions, such as CD11b expression, cellular adhesion, superoxide anion generation, and degranulation in human eosinophils. RESULTS: Preincubation of eosinophils with bisindolylmaleimide I resulted in enhancement of upregulated CD11b expression and adhesion induced by PAF. H89 pretreatment also enhanced PAF-induced cellular adhesion. Superoxide anion generation and degranulation were suppressed by means of inhibition of either PKC or PKA. CONCLUSION: PKC and PKA negatively regulate PAF-induced CD11b upregulation and cellular adhesion but promote eosinophil effector functions, such as superoxide anion generation and degranulation. PKC and PKA modulate PAF-evoked intracellular signaling of the eosinophil function in distinct ways.

Benzoquinones↗

PubMed2002

Respiratory syncytial virus enhances the expression of CD11b molecules and the generation of superoxide anion by human eosinophils primed with platelet-activating factor.

BACKGROUND: Human respiratory syncytial virus (RSV) infection in infancy and early childhood causes acute bronchiolitis and exacerbates bronchial asthma. Eosinophil infiltration may contribute to airway obstruction in RSV infection. OBJECTIVE: We hypothesized that RSV affects eosinophil function. METHODS: Eosinophil activation was evaluated by chemiluminescent detection of superoxide anion (O(2)(-)) generation. Expression of CD11b on eosinophils was determined by flow cytometry. RESULTS: Although RSV did not induce O(2)(-) generation by resting eosinophils, RSV enhanced O(2)(-) generation of eosinophils primed with platelet-activating factor (PAF). Enhancement was significantly inhibited by either continuous agitation to prevent eosinophil adhesion to test tube surfaces or by pretreating cells with anti-CD18 antibody, suggesting that the stimulatory effects of RSV on eosinophils depend on cell adhesion via beta(2)-integrins. In fact, RSV enhanced PAF-induced CD11b expression by eosinophils. CONCLUSIONS These findings suggest that RSV enhances eosinophil CD11b expression and O(2)(-) generation induced by PAF. Thus, RSV infection may exacerbate airway inflammation by enhancing mediator release from eosinophils.

Eosinophils↗