Koichi Sato

Gunma University, Maebashi, Gunma, Japan

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Publications (74)267.94 Total impact

  • PLoS ONE 06/2015; 10(6):e0129334. DOI:10.1371/journal.pone.0129334 · 3.53 Impact Factor
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    ABSTRACT: Free fatty acid receptor 4 (FFA4; formerly known as GPR120) is the G protein-coupled receptor (GPCR) for omega-3 polyunsaturated fatty acids. FFA4 has been found to express in the small intestines and colons of mice and humans. In this study we investigate the effects of omega-3 polyunsaturated fatty acids on FFA4 in human colon epithelial cells in vitro. HCT116 and HT-29 human colon epithelial cell lines endogenously expressing FFA4 were used. Intracellular Ca(2+) concentration ([Ca(2+)]i) was measured in fura 2-AM-loaded cells with fluorescence spectrophotometry. RT-PCR and immunohistochemistry were used to detect FFA4. Ten to 100 μmol/L of omega-3 polyunsaturated fatty acids α-linolenic acid (αLA) or eicosapentaenoic acid (EPA) induced dose-dependent [Ca(2+)]i increase in HCT116 and HT-29 cells, whereas docosahexaenoic acid (DHA) had no effect. In addition, the omega-6 fatty acids linoleic acid and γ-linoleic acid also dose-dependently increase [Ca(2+)]i, but the mono-unsaturated fatty acid oleic acid and saturated fatty acids such as stearic acid and palmitic acid had no effect. In HCT116 and HT-29 cells, the αLA-induced [Ca(2+)]i increase was partially inhibited by pretreatment with EGTA, phospholipase C inhibitor edelfosine, cADPR inhibitors 8-bro-cADPR or DAB, and abolished by pretreatment with Ca(2+)ATPase inhibitor thapsigargin, but was not affected by Gi/o protein inhibitor PTX or IP3R inhibitor 2-APB. Omega-3 and omega-6 long-chain polyunsaturated fatty acids (C18-20) induce Ca(2+) mobilization responses in human colonic epithelial cells in vitro through activation of FFA4 and PTX-insensitive Gi/o protein, followed by Ca(2+) release from thapsigargin-sensitive Ca(2+) stores and Ca(2+) influx across the plasma membrane.
    Acta Pharmacologica Sinica 05/2015; DOI:10.1038/aps.2015.29 · 2.50 Impact Factor
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    ABSTRACT: The elucidation of the functional mechanisms of extracellular acidification stimulating intracellular signaling pathway is of great importance for developing new targets of treatment for solid tumors, and inflamitory disorders characterized by extracellular acidification. In the present study, we focus on the regulation of extracellular acidification on intracellular signaling pathways in mouse embryo fibroblasts (MEFs). We found extracellular acidification was at least partly involved in stimulating p38MAPK pathway through PTX-sensitive behavior to enhance cell migration in the presence or absence of platelet-derived growth factor (PDGF). Statistical analysis showed that the actions of extracellular acidic pH and PDGF on inducing enhancement of cell migration were not an additive effect. However, we also found extracellular acidic pH did inhibit the viability and proliferation of MEFs, suggesting that extracellular acidification stimulates cell migration probably through proton-sensing mechanisms within MEFs. Using OGR1-, GPR4-, and TDAG8-gene knock out technology, and real-time qPCR, we found known proton-sensing G protein-coupled receptors (GPCRs), transient receptor potential vanilloid subtype 1 (TRPV1), and acid-sensing ion channels (ASICs) were unlikely to be involved in the regulation of acidification on cell migration. In conclusion, our present study validates that extracellular acidification stimulates chemotactic migration of MEFs through activation of p38MAPK with a PTX-sensitive mechanism either by itself, or synergistically with PDGF, which was not regulated by the known proton-sensing GPCRs, TRPV1, or ASICs. Our results suggested that others proton-sensing GPCRs or ion channels might exist in MEFs, which mediates cell migration induced by extracellular acidification in the presence or absence of PDGF. Copyright © 2015. Published by Elsevier Inc.
    Biochemical and Biophysical Research Communications 03/2015; 460(2). DOI:10.1016/j.bbrc.2015.03.006 · 2.28 Impact Factor
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    ABSTRACT: Mammalian ovarian G-protein-coupled receptor 1 (OGR1) and GPR4 are identified as a proton-sensing G-protein-coupled receptor coupling to multiple intracellular signaling pathways. In the present study, we examined whether zebra fish OGR1 and GPR4 homologs (zOGR1 and zGPR4) could sense protons and activate the multiple intracellular signaling pathways and, if so, whether the similar positions of histidine residue, which is critical for sensing protons in mammalian OGR and GPR4, also play a role to sense protons and activate the multiple signaling pathways in the zebra fish receptors. We found that extracellular acidic pH stimulated CRE-, SRE-, and NFAT-promoter activities in zOGR1 overexpressed cells and stimulated CRE- and SRE- but not NFAT-promoter activities in zGPR4 overexpressed cells. The substitution of histidine residues at the 12(th), 15(th), 162(th), and 264(th) positions from the N-terminal of zOGR1 with phenylalanine attenuated the proton-induced SRE-promoter activities. The mutation of the histidine residue at the 78(th) but not the 84(th) position from the N-terminal of zGPR4 to phenylalanine attenuated the proton-induced SRE-promoter activities. These results suggest that zOGR1 and zGPR4 are also proton-sensing G-protein-coupled receptors, and the receptor activation mechanisms may be similar to those of the mammalian receptors. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Biochemical and Biophysical Research Communications 01/2015; 457(4). DOI:10.1016/j.bbrc.2014.12.105 · 2.28 Impact Factor
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    ABSTRACT: Sphingosine 1-phosphate (S1P) has been implicated in anti-atherogenic properties of high-density lipoproteins. However, the roles and signaling of S1P in macrophages, the main contributor to atherosclerosis, have not been well studied. Furthermore, pro-inflammatory M1 and anti-inflammatory M2 macrophage phenotypes may influence the development of atherosclerosis. Therefore, we investigated the effects of S1P on macrophages phenotypes, especially on M2 polarization and its signaling in relation to the anti-atherogenic properties of S1P. It was found that S1P induced anti-inflammatory M2 polarization via IL-4 secretion and its signaling, and induced IL-4Rα and IL-2Rγ. In addition, down-stream signalings, such as, stat-6 phosphorylation, SOCS1 induction, and SOCS3 suppression were also observed in macrophages in response to S1P. Furthermore, S1P-induced ERK activation, and the inhibitions of p38 MAPK and JNK were found to be key signals for IL-4 induction. Moreover, the anti-atherogenic effect of S1P in HDL was confirmed by the observation that oxidized LDL-induced lipid accumulation was attenuated in S1P-treated M2 macrophages. Furthermore, the atheroprotective effect of S1P was demonstrated by its anti-apoptotic effect on S1P-treated macrophages. The present study shows that S1P-induced M2 polarization of macrophages could be mediated via IL-4 signaling, and suggests that M2 polarization by S1P is responsible for the anti-atherogenic and atheroprotective properties of high-density lipoproteins in vivo.
    Cellular Signalling 10/2014; 26(10). DOI:10.1016/j.cellsig.2014.07.009 · 4.47 Impact Factor
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    ABSTRACT: Neuronal NO synthase (nNOS)-mediated cGMP accumulation has been shown to affect a variety of neuronal cell activities, regardless of whether they are detrimental or beneficial, depending on the amount of their levels, under the physiological and pathological situations. In the present study, we examined the role of proton-sensing G protein-coupled receptors (GPCRs), which have been identified as new pH sensors, in the acidic pH-induced nNOS/cGMP activity in N1E-115 neuronal cells. In this cell line, ovarian cancer G protein-coupled receptor 1 (OGR1) and G protein-coupled receptor 4 (GPR4) mRNAs are expressed. An extracellular acidic pH increased cGMP accumulation, which was inhibited by nNOS-specific inhibitors. Acidic pH also activated phospholipase C/Ca(2+) pathways and Akt-induced phosphorylation of nNOS at S1412, both of which have been shown to be critical regulatory mechanisms for nNOS activation. The acidic pH-induced activation of the phospholipase C/Ca(2+) pathway, but not Akt/nNOS phosphorylation, was inhibited by small interfering RNA specific to OGR1 and YM-254890, an inhibitor of Gq/11 proteins, in association with the inhibition of cGMP accumulation. Moreover cGMP accumulation was inhibited by 2-aminoethoxydiphenyl borate, an inhibitor of inositol 1,4,5-trisphosphate channel; however, it was not by wortmannin, a phosphatidylinositol 3-kinase inhibitor, which inhibited Akt/nNOS phosphorylation. In conclusion, acidic pH stimulates cGMP accumulation preferentially through the OGR1/Gq/11 proteins/phospholipase C/Ca(2+)/nNOS in N1E-115 neuronal cells. Akt-mediated phosphorylation of nNOS, however, does not appreciably contribute to the acidification-induced accumulation of cGMP.
    Cellular Signalling 07/2014; 26(11). DOI:10.1016/j.cellsig.2014.07.010 · 4.47 Impact Factor
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    ABSTRACT: Oxidatively damaged proteins and lipid peroxidation products have been shown to accumulate in the brain of neurodegenerative diseases, such as Alzheimer’s disease and multiple sclerosis, and oxidized lipoprotein is considered to be toxic and neurodegenerative. However, the role of lipoprotein and its oxidized form in neurite remodeling has not been well understood. In the present study, we have aimed to clarify whether and, if so, how high-density lipoprotein (HDL) and oxidized HDL (oxHDL) affect neuritogenesis. In the presence of nerve growth factor, exposure of PC12 cells to either HDL or oxHDL induces a rapid neurite retraction, which is followed by re-outgrowth of neurites in either case; however, oxHDL-treated cells exhibit much longer outgrowths than do basal and HDL-treated cells. Thus, processes in the morphological changes of neuronal cells after lipoprotein treatment are composed of two phases: the reversible retraction phase and the extension phase. Characterization of the active fractions of lipids and experiments with desensitization and knockdown of receptors have indicated that the reversible retraction phase involves mainly sphingosine 1-phosphate for HDL and lysophosphatidic acid for oxHDL. The change in the components responsible for the retraction response is comparable with the change in sphingosine 1-phosphate and lysophosphatidic acid contents by the oxidation of HDL. In the extension phase, lysophosphatidylcholine, which is increased by the oxidation of HDL, may play a stimulatory role in neurite outgrowth. We conclude that lipoprotein and its oxidized form differentially regulate neuritogenesis through lipoprotein-associated lysolipid molecules.
    Neurochemistry International 03/2014; 68. DOI:10.1016/j.neuint.2014.02.005 · 2.65 Impact Factor
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    ABSTRACT: Interleukin-1β (IL-1β) is released from activated microglia and involved in the neurodegeneration of acute and chronic brain disorders, such as stroke and Alzheimer's disease, in which extracellular acidification has been shown to occur. Here, we examined the extracellular acidic pH regulation of IL-1β production, especially focusing on TDAG8, a major proton-sensing G-protein-coupled receptor, in mouse microglia. Extracellular acidification inhibited lipopolysaccaride (LPS)-induced IL-1β production, which was associated with the inhibition of IL-1β cytoplasmic precursor and mRNA expression. The IL-1β mRNA and protein responses were significantly, though not completely, attenuated in microglia derived from TDAG8-deficient mice compared with those from wild-type mice. The acidic pH also stimulated cellular cAMP accumulation, which was completely inhibited by TDAG8 deficiency. Forskolin and a cAMP derivative, which specifically stimulates protein kinase A (PKA), mimicked the proton actions, and PKA inhibitors reversed the acidic pH-induced IL-1β mRNA expression. The acidic pH-induced inhibitory IL-1β responses were accompanied by the inhibition of extracellular signal-related kinase (ERK) and c-Jun N-terminal kinase (JNK) activities. The inhibitory enzyme activities in response to acidic pH were reversed by the PKA inhibitor and TDAG8 deficiency. We conclude that extracellular acidic pH inhibits LPS-induced IL-1β production, at least partly, through the TDAG8/cAMP/PKA pathway, by inhibiting ERK and JNK activities, in mouse microglia. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 01/2014; DOI:10.1111/jnc.12661 · 4.24 Impact Factor
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    ABSTRACT: Ovarian cancer G protein-coupled receptor 1 (OGR1) stimulation by extracellular protons causes the activation of G proteins and subsequent cellular functions. However, the physiological and pathophysiological roles of OGR1 in airway responses remain largely unknown. In the present study, we show that OGR1-deficient mice are resistant to the cardinal features of asthma, including airway eosinophilia, airway hyperresponsiveness (AHR), and goblet cell metaplasia, in association with a remarkable inhibition of Th2 cytokine and IgE production, in an ovalbumin (OVA)-induced asthma model. Intratracheal transfer to wild-type mice of OVA-primed bone marrow-derived dendritic cells (DCs) from OGR1-deficient mice developed lower AHR and eosinophilia after OVA inhalation compared with the transfer of those from wild-type mice. Migration of OVA-pulsed DCs to peribronchial lymph nodes was also inhibited by OGR1 deficiency in the adoption experiments. The presence of functional OGR1 in DCs was confirmed by the expression of OGR1 mRNA and the OGR1-sensitive Ca(2+) response. OVA-induced expression of CCR7, a mature DC chemokine receptor, and migration response to CCR7 ligands in an in vitro Transwell assay were attenuated by OGR1 deficiency. We conclude that OGR1 on DCs is critical for migration to draining lymph nodes, which, in turn, stimulates Th2 phenotype change and subsequent induction of airway inflammation and AHR.
    PLoS ONE 11/2013; 8(11):e79985. DOI:10.1371/journal.pone.0079985 · 3.53 Impact Factor
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    ABSTRACT: Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown as a receptor for protons. In the present study, we aimed to know whether OGR1 plays a role in insulin secretion and, if so, the manner in which it does. To this end, we created OGR1-deficient mice and examined insulin secretion activity in vivo and in vitro. OGR1 deficiency reduced insulin secretion induced by glucose administered ip, although it was not associated with glucose intolerance in vivo. Increased insulin sensitivity and reduced plasma glucagon level may explain, in part, the unusual normal glucose tolerance. In vitro islet experiments revealed that glucose-stimulated insulin secretion was dependent on extracellular pH and sensitive to OGR1; insulin secretion at pH 7.4 to 7.0, but not 8.0, was significantly suppressed by OGR1 deficiency and inhibition of G(q/11) proteins. Insulin secretion induced by KCl and tolbutamide was also significantly inhibited, whereas that induced by several insulin secretagogues, including vasopressin, a glucagon-like peptide 1 receptor agonist, and forskolin, was not suppressed by OGR1 deficiency. The inhibition of insulin secretion was associated with the reduction of glucose-induced increase in intracellular Ca(2+) concentration. In conclusion, the OGR1/G(q/11) protein pathway is activated by extracellular protons existing under the physiological extracellular pH of 7.4 and further stimulated by acidification, resulting in the enhancement of insulin secretion in response to high glucose concentrations and KCl.
    Endocrinology 06/2012; 153(9):4171-80. DOI:10.1210/en.2012-1164 · 4.64 Impact Factor
  • Cardiovascular Research 04/2012; 94(1):163. DOI:10.1093/cvr/cvs087 · 5.81 Impact Factor
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    ABSTRACT: Pancreatic cancer is highly metastatic and has a poor prognosis. However, there is no established treatment for pancreatic cancer. Lysophosphatidic acid (LPA) has been shown to be present in effluents of cancers and involved in migration and proliferation in a variety of cancer cells, including pancreatic cancer cells, in vitro. In the current study, we examined whether an orally active LPA antagonist is effective for pancreatic cancer tumorigenesis and metastasis in vivo. Oral administration of Ki16198, which is effective for LPA(1) and LPA(3), into YAPC-PD pancreatic cancer cell-inoculated nude mice significantly inhibited tumor weight and remarkably attenuated invasion and metastasis to lung, liver, and brain, in association with inhibition of matrix metalloproteinase (MMP) accumulation in ascites in vivo. Ki16198 inhibited LPA-induced migration and invasion in several pancreatic cancer cells in vitro, which was associated with the inhibition of LPA-induced MMP production. In conclusion, Ki16198 is a promising orally active LPA antagonist for inhibiting the invasion and metastasis of pancreatic cancer cells. The inhibitory effects of the antagonist on invasion and metastasis in vivo may be partially explained by the inhibition of motility activity and MMP production in cancer cells.
    Cancer Science 02/2012; 103(6):1099-104. DOI:10.1111/j.1349-7006.2012.02246.x · 3.53 Impact Factor
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    ABSTRACT: Dexamethasone (DEX), a potent glucocorticoid, increased the expression of T-cell death associated gene 8 (TDAG8), a proton-sensing G protein-coupled receptor, which is associated with the enhancement of acidic pH-induced cAMP accumulation, in peritoneal macrophages. We explored the role of increased TDAG8 expression in the anti-inflammatory actions of DEX. The treatment of macrophages with either DEX or acidic pH induced the cell death of macrophages; however, the cell death was not affected by TDAG8 deficiency. While DEX inhibited lipopolysaccharide-induced production of tumor necrosis factor-α, an inflammatory cytokine, which was independent of TDAG8, at neutral pH, the glucocorticoid enhanced the acidic pH-induced inhibition of tumor necrosis factor-α production in a manner dependent on TDAG8. In conclusion, the DEX-induced increase in TDAG8 expression is in part involved in the glucocorticoid-induced anti-inflammatory actions through the inhibition of inflammatory cytokine production under the acidic pH environment. On the other hand, the role of TDAG8 in the DEX-induced cell death is questionable.
    Biochemical and Biophysical Research Communications 11/2011; 415(4):627-31. DOI:10.1016/j.bbrc.2011.10.122 · 2.28 Impact Factor
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    ABSTRACT: Asthma is characterized by airway inflammation, hyper-responsiveness and remodeling. Extracellular acidification is known to be associated with severe asthma; however, the role of extracellular acidification in airway remodeling remains elusive. In the present study, the effects of acidification on the expression of connective tissue growth factor (CTGF), a critical factor involved in the formation of extracellular matrix proteins and hence airway remodeling, were examined in human airway smooth muscle cells (ASMCs). Acidic pH alone induced a substantial production of CTGF, and enhanced transforming growth factor (TGF)-β-induced CTGF mRNA and protein expression. The extracellular acidic pH-induced effects were inhibited by knockdown of a proton-sensing ovarian cancer G-protein-coupled receptor (OGR1) with its specific small interfering RNA and by addition of the G(q/11) protein-specific inhibitor, YM-254890, or the inositol-1,4,5-trisphosphate (IP(3)) receptor antagonist, 2-APB. In conclusion, extracellular acidification induces CTGF production through the OGR1/G(q/11) protein and inositol-1,4,5-trisphosphate-induced Ca(2+) mobilization in human ASMCs.
    Biochemical and Biophysical Research Communications 09/2011; 413(4):499-503. DOI:10.1016/j.bbrc.2011.08.087 · 2.28 Impact Factor
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    ABSTRACT: We investigated the mechanisms of action of lysophosphatidic acid (LPA) to regulate vascular endothelial (VE)-cadherin dynamics and cell-cell contact. While a low concentration of LPA stimulated VE-cadherin internalization and subsequent cell-cell dissociation, a high concentration of LPA masked the disruptive actions on VE-cadherin and protected the barrier function in human vascular endothelial cells. Knockdown experiments of major LPA receptor subtypes, i.e. LPA(1) and p2y5 (also termed LPA(6)), with their specific small interfering RNAs, showed that LPA(1) and LPA(6) mediate the LPA-induced disruptive and protective actions on barrier integrity, respectively. LPA(6)-mediated tube formation, reflecting stabilization of barrier integrity, was confirmed by in vitro angiogenesis assay. The LPA(1)-mediated disruptive actions were inhibited by pertussis toxin, dominant-negative Rac1, and inhibitors for c-Jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK), but not by dominant-negative RhoA. In contrast, the LPA(6)-mediated protective actions were associated with activation of Src and Rap1 and attenuated by abrogation of their activities. Further characterization showed that Rap1 is located downstream of Src and dependent on C3G, a Rap1 guanine nucleotide exchange factor. Finally, an LPA antagonist significantly inhibited lactic acid-induced limb lesions in vivo, which may be attributed to dysfunction of endothelial cells. LPA induced disruption and protection of VE-cadherin integrity through LPA(1)-G(i) protein-Rac1-JNK/p38MAPK and LPA(6)-G(12/13) protein-Src-C3G-Rap1 pathways, respectively.
    Cardiovascular Research 06/2011; 92(1):149-58. DOI:10.1093/cvr/cvr154 · 5.81 Impact Factor
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    ABSTRACT: Action mechanism of lipopolysaccharide (LPS), interleukin-1β (IL-1β), and lysophosphatidic acid (LPA) to regulate motility, an important process of astrogliosis, was investigated in rat astrocytes. While LPA exerted no significant effect on the cell migration, the prior treatment of the cells with LPS or IL-1β resulted in the appearance of migration activity in response to LPA. The LPS induction of the migration response to LPA was associated with the production of IL-1β precursor protein and inhibited by the IL-1 receptor antagonist. The IL-1β treatment also allowed LPA to activate Rac1. The LPA-induced Rac1 activation and migration were inhibited by pertussis toxin, a small interfering RNA specific to LPA(1) receptors, and LPA(1) receptor antagonists, including Ki16425. However, the IL-1β treatment had no appreciable effect on LPA(1) receptor mRNA expression and LPA-induced activation of ERK, Akt, and proliferation. The induction of the migration response to LPA by IL-1β was inhibited by a constitutively active RhoA. Moreover, LPA significantly activated RhoA through the LPA(1) receptor in the control cells but not in the IL-1β-treated cells. These results suggest that IL-1β inhibits the LPA(1) receptor-mediated Rho signaling through the IL-1 receptor, thereby disclosing the LPA(1) receptor-mediated G(i) protein/Rac/migration pathway.
    Journal of Neurochemistry 04/2011; 117(1):164-74. DOI:10.1111/j.1471-4159.2011.07188.x · 4.24 Impact Factor
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    Koichi Sato, Fumikazu Okajima
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    ABSTRACT: The reverse cholesterol transport mediated by high-density lipoprotein (HDL) is an important mechanism for maintaining body cholesterol, and hence, the crucial anti-atherogenic action of the lipoprotein. Recent studies, however, have shown that HDL exerts a variety of anti-inflammatory and anti-atherogenic actions independently of cholesterol metabolism. The present review provides an overview of the roles of sphingosine 1-phosphate (S1P)/S1P receptor and apolipoprotein A-I/scavenger receptor class B type I systems in the anti-atherogenic HDL actions. In addition, the physiological significance of the existence of S1P in the HDL particles is discussed.
    11/2010; 1(11):327-37. DOI:10.4331/wjbc.v1.i11.327
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    ABSTRACT: The asthmatic airway has been shown to be an acidic environment that may be involved in the pathophysiological features of asthma. However, the mechanism by which an acidic pH modulates the cellular activities involved in the asthmatic airway remains elusive. Here, we characterized acidic pH-induced actions in human airway smooth muscle cells (ASMCs). Extracellular acidification stimulates the mRNA expression and protein production of IL-6, a proinflammatory cytokine, in association with the phosphorylation of extracellular signal-regulated kinase (ERK) and p38MAPK, reflecting the activation of the enzymes. Acidification-induced cytokine production was inhibited by inhibitors of ERK and p38MAPK. Acidification also increased intracellular Ca(2+) concentration, which was accompanied by cell rounding, most likely reflecting contraction. In ASMCs, OGR1 is expressed at by far the highest levels among proton-sensing G protein-coupled receptors. The knockdown of OGR1 and G(q/11) protein with their specific small interfering RNAs and an inhibition of G(q/11) protein with YM-254890 attenuated the acidification-induced actions. We conclude that extracellular acidification stimulates IL-6 production and Ca(2+) mobilization through proton-sensing OGR1 receptors/G(q/11) proteins in human ASMCs.
    AJP Lung Cellular and Molecular Physiology 10/2010; 299(4):L567-77. DOI:10.1152/ajplung.00415.2009 · 4.04 Impact Factor
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    ABSTRACT: Atherosclerosis is a chronic inflammation disease characterized by acidic micromilieu and the accumulation of numerous bioactive lipid mediators, such as lysophosphatidic acid (LPA) and prostaglandins, in the atherosclerotic lesion. Chronic acidification induced various effects on vascular smooth muscle cells, but the molecular mechanisms underlying these effects remain unknown. In this study, we examine the role of proton-sensing ovarian cancer G protein-coupled receptor 1 (OGR1) in extracellular acidification-induced regulation of cyclooxygenase (COX)-2 induction, PGI(2) production, MAPK phosphatase (MKP)-1 expression, and plasminogen activator inhibitor (PAI)-1 expression and proliferation in human aortic smooth muscle cells (AoSMCs). Experiments with knockdown with small interfering RNA specific to OGR1 and specific inhibitors for G proteins showed that acidification-induced COX-2 expression, PGI(2) production, and MKP-1 expression, but not PAI-1 expression and inhibition of proliferation, were dependent on OGR1 and mainly mediated by G(q/11) protein. LPA remarkably enhanced, through the LPA(1) receptor/G(i) protein, the OGR1-mediated vascular actions to acidic pH. In conclusion, acidic pH-induced vascular actions of AoSMCs can be dissected to OGR1-dependent and -independent pathways: COX-2 expression, PGI(2) production, and MKP-1 expression are mediated by OGR1, but PAI-1 expression and inhibition of proliferation are not. LPA, which is usually thought to be a proatherogenic lipid mediator, may exert antiatherogenic actions under acidic micromilieu through cross-talk between LPA(1)/G(i) protein and OGR1/G(q/11) protein.
    AJP Heart and Circulatory Physiology 09/2010; 299(3):H731-42. DOI:10.1152/ajpheart.00977.2009 · 4.01 Impact Factor
  • Folia Pharmacologica Japonica 06/2010; 135(6):240-4. DOI:10.1254/fpj.135.240

Publication Stats

3k Citations
267.94 Total Impact Points

Institutions

  • 1989–2015
    • Gunma University
      • • Laboratory of Signal Transduction
      • • Institute for Molecular and Cellular Regulation
      Maebashi, Gunma, Japan
  • 2004–2005
    • Pusan National University
      • College of Pharmacy
      Pusan, Busan, South Korea