Bing Qi

Tokyo Dental College, Tokyo, Tokyo-to, Japan

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Publications (12)11.77 Total impact

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    ABSTRACT: Insulin-like growth factor-I (IGF-I) is expressed in salivary glands. We examined the effects of IGF-I on cell number, the expression and distribution of tight junction proteins and the paracellular barrier function in cells derived from rat submandibular glands. When those cells were cultured in medium containing 10% foetal bovine serum (FBS) or IGF-I, the number of cells was comparable at 10 days. However, in the presence of inhibitor of IGF-I receptors, the number of cells cultured with FBS only was clearly reduced. The tight junction proteins occludin and claudin-3 were similarly detected by Western blotting in cells cultured with IGF-I or FBS. Immunostaining revealed that occludin and another tight junction protein (ZO-1) were similarly localized at intracellular junctions of cells cultured with IGF-I or FBS. The barrier functions were evaluated by transepithelial resistance (TER) and by FITC-dextran permeability. The TER values and FITC-dextran permeability of cells cultured with IGF-I or FBS were comparable. These observations suggest that IGF-I contributes to the maintenance not only of the cell number of salivary gland cells but also of their paracellular barrier function via the expression and distribution of tight junction proteins.
    Archives of oral biology 12/2010; 55(12):963-9. · 1.65 Impact Factor
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    ABSTRACT: Tachykinins such as neurokinin A (NKA) and substance P have been demonstrated to induce salivary fluid secretion in vivo. However, characteristics of salivary fluid secretion induced by tachykinins in salivary glands have not been well elucidated. In this study, the effects of the tachykinin NKA on salivary fluid secretion were investigated in isolated, perfused rat submandibular gland. NKA provoked salivary fluid secretion, which consisted of transient and sustained phases, in a dose-dependent manner. In fura-2-loaded dispersed cells of the rat submandibular gland, the doses of NKA in which induced salivary fluid secretion caused an increase in intracellular Ca(2+) concentration. When Ca(2+) was removed from the perfusate to examine the effect of Ca(2+) mobilization on NKA-induced fluid secretion, only the transient salivary fluid secretion occurred. When the gland was perfused with the Ca(2+)-free perfusate containing the intracellular Ca(2+) chelator BAPTA-AM, NKA failed to induce salivary fluid secretion. NKA also induced an increase in oxygen consumption, but which was reduced by the removal of Ca(2+) from perfusate. Salivary fluid is secreted via transcellular and paracellular pathways in acinar cells of salivary glands. To examine the contribution of paracellular pathway to NKA-induced salivary fluid secretion, the glands were perfused with a perfusate containing Lucifer yellow (LY), a cellular impermeable substance, and then were stimulated with NKA, which provoked secretion of LY in the saliva. These results suggest that the NKA-induced salivary fluid secretion is Ca(2+)-dependent and that the paracellular pathway contributes to the secretion.
    Archives of oral biology 10/2010; 55(10):737-44. · 1.65 Impact Factor
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    ABSTRACT: In parotid acinar cells, the activation of β-adrenergic receptors induces the accumulation of intracellular cAMP, and consequently provokes the exocytotic release of amylase, a digestive enzyme. The cellular redox status plays a pivotal role in regulating various cellular functions. Cellular redox imbalance caused by the oxidation of cellular antioxidants, as a result of oxidative stress, induces significant biological damage. In this study, we examined the effects of diamide, a thiol-oxidizing reagent, on amylase release by rat parotid acinar cells. In cells treated with diamide, the formation of cAMP and the release of amylase induced by the β-agonist isoproterenol (IPR) were partially reduced. The inhibitory effect of diamide on the IPR-induced release of amylase could be abrogated by reduced glutathione or dithiothreitol. Diamide had no effect on the amylase release induced by forskolin, an adenylate cyclase activator, or by mastoparan, a heterotrimeric GTPbinding protein activator. In cells treated with diamide, the binding affinity for [(3)H]DHA, but not the number of binding sites, was reduced. These results suggest that β-adrenergic receptor function is reduced by thiol-oxidation, which inhibits amylase secretion by parotid acinar cells.
    Biomedical Research 01/2010; 31(5):293-9. · 1.15 Impact Factor
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    ABSTRACT: Myristoylated alanine-rich C kinase substrate (MARCKS) is known as a major cellular substrate for protein kinase C (PKC). MARCKS has been implicated in the regulation of brain development and postnatal survival, cellular migration and adhesion, as well as phagocytosis, endocytosis, and exocytosis. The involvement of MARCKS phosphorylation in secretory function has been reported in Ca(2+)-mediated exocytosis. In rat parotid acinar cells, the activation of beta-adrenergic receptors provokes exocytotic amylase release via accumulation of intracellular cAMP levels. Here, we studied the involvement of MARCKS phosphorylation in the cAMP-dependent amylase release in rat parotid acinar cells. MARCKS protein was detected in rat parotid acinar cells by Western blotting. The beta-adrenergic agonist isoproterenol (IPR) induced MARCKS phosphorylation in a time-dependent manner. Translocation of a part of phosphorylated MARCKS from the membrane to the cytosol and enhancement of MARCKS phosphorylation at the apical membrane site induced by IPR were observed by immunohistochemistry. H89, a cAMP-dependent protein kinase (PKA) inhibitor, inhibited the IPR-induced MARCKS phosphorylation. The PKCdelta inhibitor rottlerin inhibited the IPR-induced MARCKS phosphorylation and amylase release. IPR activated PKCdelta, and the effects of IPR were inhibited by the PKA inhibitors. A MARCKS-related peptide partially inhibited the IPR-induced amylase release. These findings suggest that MARCKS phosphorylation via the activation of PKCdelta, which is downstream of PKA activation, is involved in the cAMP-dependent amylase release in parotid acinar cells.
    AJP Gastrointestinal and Liver Physiology 05/2009; 296(6):G1382-90. · 3.65 Impact Factor
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    ABSTRACT: Neurokinin A (NKA) evokes salivary secretion. Despite such reports, the direct effect of NKA on salivary secretion in submandibular gland has not been clarified. Here we studied characterization of salivary fluid secretion induced by NKA in the perfused submandibular grand (SMG) of the rat. NKA (3-100 nM) stimulated salivary fluid secretion in a dose-dependent manner. The profile of secretion induced by NKA consisted of two phases, transient and sustained phases. When the gland was perfused with Lucifer yellow (LY)-containing perfusate buffer and stimulated by NKA, concentration of LY in saliva was increased. In the absence of Ca(2+) in the perfusate, NKA induced only a transient salivary fluid and a transient LY secretion. When the gland was treated with BAPTA, NKA failed to induce both salivary fluid secretion and LY secretion. These results suggest that NKA induces salivary secretion via both transcellular and paracellular pathways, which depends on intracellular Ca(2+) mobilization.
    The Journal of Medical Investigation 01/2009; 56 Suppl:278-80.
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    ABSTRACT: Hyposecretion of saliva and consequent dry mouth lead to severe caries and periodontal disease. Therapeutic radiation for head and neck cancer and sialadenitis result in atrophy and fibrosis of salivary glands, but the mechanism is not clear. As a model for dysfunction of salivary glands, we examined the change of gene expression patterns in primary cultured parotid acinar cells. The expression levels of acinar markers such as amylase and aquaporin-5 rapidly decreased during culture. At the same time, ductal markers began to be expressed although their expression was transient. In the late phase of culture, markers of epithelial-mesenchymal transition began to be expressed and increased. Inhibitor for Src or p38 MAP kinase suppressed these changes. These results suggest that parotid acinar cells transiently change to duct-like cells during epithelial-mesenchymal transition and that these changes are induced by signal transduction via Src-p38 MAP kinase pathway. There is a possibility that parotid acinar cells retain a plasticity of differentiation.
    The Journal of Medical Investigation 01/2009; 56 Suppl:258-9.
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    ABSTRACT: Salivary gland acinar cells secrete large amounts of water and electrolytes, where aquaporins (AQPs) are thought to be involved in the secretion. In the present study, we investigated expression/localization of AQP6, and the anion transporting properties of AQP6 in mouse parotid acinar cells. RT-PCR, western blotting and immunohistochemical analyses revealed expression of AQP6 in acinar cells, localized in apical membrane. Voltage ramp from -100 mV to +100 mV at a holding potential of -60 mV elicited outwardly-rectifying currents, in the presence of extracellular Cl(-) channel blockers and intracellular solution with 150 mM Cs(+). These outward currents were increased when extracellular Cl(-) was replaced by Br(-), NO(3)(-), I(-), or SCN(-), accompanying a negative shift of reversal potentials. The outward current was enhanced by extracellular Hg(2+). These results were consistent with the biophysical properties of transfected AQP6 oocytes or HEK cells, which indicate that the AQP6 channel is functionally expressed in parotid acinar cells, and suggest that AQP6 contributes to secretion of anions in parotid acinar cells.
    The Journal of Medical Investigation 01/2009; 56 Suppl:347-9.
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    ABSTRACT: Xerostomia is the symptom of dry mouth often seen in patients who receive head and neck radiation therapy or in patients who have Sjögren's syndrome. The primary treatment to relieve xerostomia symptom is oral administration of pilocarpine, a parasympathomimetic agent with muscarinic action. Increase in salivary secretion induced by systemic administration of pilocarpine is considered to be mediated by actions on muscarinic cholinergic receptors in the central nervous system and salivary glands. In this study, we investigated the direct effect of pilocarpine on salivary fluid secretion in the isolated, perfused rat submandibular gland. Pilocarpine provoked salivary fluid secretion in a dose-dependent manner. The Na(+)-channel blocker tetrodotoxin had almost no effect on the pilocarpine-induced salivary fluid secretion, indicating that pilocarpine directly stimulates submandibular gland. Pilocarpine induced an increase in intracellular Ca(2+) concentration in dispersed submandibular gland cells at 37 degrees C, but not 25 degrees C. The salivary fluid secretion induced by pilocarpine was consisted of a rapid and transient phase and a subsequent sustained phase, which profile was different from that evoked by carbachol, another typical muscarinic agonist. Pilocarpine also induced Lucifer yellow secretion via paracellular route.
    The Journal of Medical Investigation 01/2009; 56 Suppl:281-3.
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    ABSTRACT: In parotid acinar cells, beta-adrenergic receptor activation results in accumulation of intracellular cAMP. Subsequently, cAMP-dependent protein kinase (PKA) is activated and consequently amylase release is provoked. In this paper, we investigated involvement of protein kinase C-delta (PKC delta), a novel isoform of PKC, in amylase release induced by beta-adrenergic receptor stimulation. Amylase release stimulated with the beta-agonist isoproterenol (IPR) was inhibited by rottlerin, an inhibitor of PKC delta. IPR activated PKC delta and the effect of IPR were inhibited by a PKA inhibitor, H89. Myristoylated alanine-rich C kinase substrate (MARCKS), a major cellular substrate for PKC, was detected in rat parotid acinar cells, and a MARCKS inhibitor, MARCKS-related peptide, inhibited the IPR-induced amylase release. IPR stimulated MARCKS phosphorylation, which was found to be inhibited by H89 and rottlerin. These observations suggest that PKC delta activation is a downstream pathway of PKA activation and is involved in amylase release via MARCKS phosphorylation in rat parotid acinar cells stimulated with beta-adrenergic agonist.
    The Journal of Medical Investigation 01/2009; 56 Suppl:368-70.
  • The Journal of Medical Investigation 01/2009; 56:368-370.
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    ABSTRACT: In parotid acinar cells, activation of beta-adrenergic receptors provokes exocytotic amylase release via the accumulation of intracellular cAMP. Cellular redox status plays a pivotal role in the regulation of various cellular functions. Cellular redox imbalance caused by the oxidation of cellular antioxidants, as a result of oxidative stress, induces significant biological damages. In this study, we examined effect of diamide, a thiol-oxidizing reagent, on amylase release in rat parotid acinar cells. In the presence of diamide, isoproterenol (IPR)-induced cAMP formation and amylase release were partially reduced. Diamide had no effect on amylase release induced by forskolin and mastoparan, an adenylate cyclase activator and heterotrimeric GTP binding protein activator, respectively. In the cells pretreated with diamide, the binding affinity of [(3)H]dihydroalprenolol to beta-receptors was reduced. These results suggest that oxidative stress results in reduction of binding affinity of ligand on beta-receptor and consequently reduces protein secretory function in rat parotid acinar cells.
    The Journal of Medical Investigation 01/2009; 56 Suppl:284-6.
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    ABSTRACT: Tight junctions are essential for the maintenance of epithelial cell polarity. We have previously established a system for the primary culture of salivary parotid acinar cells that retain their ability to generate new secretory granules and to secrete proteins in a signal-dependent manner. Because cell polarity and cell-cell adhesion are prerequisites for the formation of epithelial tissues, we have investigated the structure of the tight junctions in these cultures. We have found two types of cellular organization in the culture: monolayers and semi-spherical clusters. Electron microscopy has revealed tight junctions near the apical region of the lateral membranes between cells in the monolayers and cells at the surface of the clusters. The cells in the interior of the clusters also have tight junctions and are organized around a central lumen. These interior cells retain more secretory granules than the surface or monolayer cells, suggesting that they maintain their original character as acinar cells. The synthesis of claudin-4 increases during culture, although it is not detectable in the cells immediately after isolation from the glands. Immunofluorescence microscopy has shown that claudin-4 is synthesized in the monolayers and at the surface of the clusters, but not inside the clusters. Only claudin-3, which is present in the original acinar cells following isolation and in the intact gland, has been detected inside the clusters. These results suggest that differences in claudin expression are related to the three-dimensional structures of the cell cultures and reflect their ability to function as acinar cells.
    Cell and Tissue Research 08/2007; 329(1):59-70. · 3.68 Impact Factor