The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Amos C Hung - One of the best experts on this subject based on the ideXlab platform.
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roles of protein kinase c in regulation of p2x7 receptor mediated calcium signalling of cultured type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2005Co-Authors: Amos C Hung, Juyun Weng, Hammer B Chen, Youjing Chu, Yahui Lin, Synthia H SunAbstract:The role of protein kinase C (PKC) on regulation of P2X(7) receptor-mediated Ca(2+) signalling was examined on RBA-2 Astrocytes. Activation of PKC decreased the receptor-mediated Ca(2+) signalling and the decrease was restored by PKC inhibitors. Down regulation of PKC also caused a decrease in the Ca(2+) signalling. Thus PKC might play a dual role on the P2X(7) receptor signalling. Successive stimulation of the P2X(7) receptor induced a gradual decLine of Ca(2+) signalling but PKC inhibitors failed to restore the decLine. Nevertheless, PMA stimulated translocation of PKC-alpha, -betaI, -betaII, and -gamma, but only anti-PKC-gamma co-immunoprecipitated the receptors. To examine the role of PKC-gamma, Ca(2+) signalling was measured by Ca(2+) imaging. Our results revealed that the agonist-stimulated Ca(2+) signalling were reduced in the Cells that the transfection of either P2X(7) receptor or PKC-gamma morpholino antisense oligo was identified. Thus, we concluded that PKC-gamma interacted with P2X(7) receptor complex and positively regulated the receptor-mediated Ca(2+) signalling.
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roles of protein kinase c in regulation of p2x7 receptor mediated calcium signalling of cultured type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2005Co-Authors: Amos C Hung, Juyun Weng, Hammer B Chen, Yinchung AuAbstract:Abstract The role of protein kinase C (PKC) on regulation of P2X 7 receptor-mediated Ca 2+ signalling was examined on RBA-2 Astrocytes. Activation of PKC decreased the receptor-mediated Ca 2+ signalling and the decrease was restored by PKC inhibitors. Down regulation of PKC also caused a decrease in the Ca 2+ signalling. Thus PKC might play a dual role on the P2X 7 receptor signalling. Successive stimulation of the P2X 7 receptor induced a gradual decLine of Ca 2+ signalling but PKC inhibitors failed to restore the decLine. Nevertheless, PMA stimulated translocation of PKC-α, -βI, -βII, and -γ, but only anti-PKC-γ co-immunoprecipitated the receptors. To examine the role of PKC-γ, Ca 2+ signalling was measured by Ca 2+ imaging. Our results revealed that the agonist-stimulated Ca 2+ signalling were reduced in the Cells that the transfection of either P2X 7 receptor or PKC-γ morpholino antisense oligo was identified. Thus, we concluded that PKC-γ interacted with P2X 7 receptor complex and positively regulated the receptor-mediated Ca 2+ signalling.
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endothelin 1 stimulated capacitative ca2 entry through eta receptors of a rat brain derived type 1 Astrocyte Cell Line ia 1g1
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Amos C Hung, Hungjung Lin, Synthia H SunAbstract:Abstract The present study demonstrated that endotheLine-1 (ET-1) stimulated a biphasic (transient and sustained) increase in [Ca 2+ ] i and signaling was blocked by BQ123 and inhibited by BQ788. RT-PCR analysis revealed that ET A was expressed more than ET B mRNA—suggesting that ET A is the major receptor. Simply reintroducing Ca 2+ in the buffer stimulated a sustained increase in [Ca 2+ ] i and the effect was inhibited by U73122, thapsigargin (TG), miconazole and SKF96365. When measured in Ca 2+ -free buffer, the ET-1-stimulated Ca 2+ transient decreased by 73% and the reintroduction of Ca 2+ induced a large sustained increase in [Ca 2+ ] i . These effects were not affected by nifedipine, but were inhibited by miconazole and SKF96365—indicating that the sustained increase in [Ca 2+ ] i mediated by ET-1 was mostly due to capacitative Ca 2+ entry (CCE). The ET-1-induced CCE was inhibited by phorbol ester (PMA) but was enhanced by GF109203X; it was also enhanced by 8-bromo-cyclic AMP (8-Br-cAMP) but was inhibited by H89. Thus, protein kinase C (PKC) negatively regulated and cAMP-dependent protein kinase (PKA) positively regulated the ET-1-mediated CCE in these Cells.
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atp stimulated ca2 influx and phospholipase d activities of a rat brain derived type 2 Astrocyte Cell Line rba 2 are mediated through p2x7 receptors
Journal of Neurochemistry, 2002Co-Authors: Amos C HungAbstract:This study characterizes and examines the P2 receptor-mediated signal transduction pathway of a rat brain-derived type 2 Astrocyte Cell Line, RBA-2. ATP induced Ca 2+ influx and activated phospholipase D (PLD). The ATP-stimulated Ca 2+ influx was inhibited by pretreating Cells with P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), in a concentration-dependent manner. The agonist 2'-and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) stimulated the largest increases in intraCellular Ca 2+ concentrations ([Ca 2+ ] i ); ATP, 2-methylthioadenosine triphosphate tetrasodium, and ATPγS were much less effective, whereas UTP, ADP, α,β-methylene-ATP, and β,γ-methylene-ATP were ineffective. Furthermore, removal of extraCellular Mg 2+ enhanced the ATP- and BzATP-stimulated increases in [Ca 2+ ] i . BzATP stimulated PLD in a concentration- and time-dependent manner that could be abolished by removal of extraCellular Ca 2+ and was inhibited by suramin, PPADS, and oxidized ATP. In addition, PLD activities were activated by the Ca 2+ mobilization agent, ionomycin, in an extraCellular Ca 2+ concentration-dependent manner. Both staurosporine and prolonged phorbol ester treatment inhibited BzATP-stimulated PLD activity. Taken together, these data indicate that activation of the P2X 7 receptors induces Ca 2+ influx and stimulates a Ca 2+ -dependent PLD in RBA-2 Astrocytes. Furthermore, protein kinase C regulates this PLD.
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atp stimulated ca2 influx and phospholipase d activities of a rat brain derived type 2 Astrocyte Cell Line rba 2 are mediated through p2x7 receptors
Journal of Neurochemistry, 2002Co-Authors: Synthia H Sun, Amos C Hung, Lianbin Lin, Jonson KuoAbstract:This study characterizes and examines the P2 receptor-mediated signal transduction pathway of a rat brain-derived type 2 Astrocyte Cell Line, RBA-2. ATP induced Ca2+ influx and activated phospholipase D (PLD). The ATP-stimulated Ca2+ influx was inhibited by pretreating Cells with P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), in a concentration-dependent manner. The agonist 2'- and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) stimulated the largest increases in intraCellular Ca2+ concentrations ([Ca2+]i); ATP, 2-methylthioadenosine triphosphate tetrasodium, and ATPgammaS were much less effective, whereas UTP, ADP, alpha,beta-methylene-ATP, and beta,gamma-methylene-ATP were ineffective. Furthermore, removal of extraCellular Mg2+ enhanced the ATP- and BzATP-stimulated increases in [Ca2+]i. BzATP stimulated PLD in a concentration- and time-dependent manner that could be abolished by removal of extraCellular Ca2+ and was inhibited by suramin, PPADS, and oxidized ATP. In addition, PLD activities were activated by the Ca2+ mobilization agent, ionomycin, in an extraCellular Ca2+ concentration-dependent manner. Both staurosporine and prolonged phorbol ester treatment inhibited BzATP-stimulated PLD activity. Taken together, these data indicate that activation of the P2X7 receptors induces Ca2+ influx and stimulates a Ca2+-dependent PLD in RBA-2 Astrocytes. Furthermore, protein kinase C regulates this PLD.
Synthia H Sun - One of the best experts on this subject based on the ideXlab platform.
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roles of protein kinase c in regulation of p2x7 receptor mediated calcium signalling of cultured type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2005Co-Authors: Amos C Hung, Juyun Weng, Hammer B Chen, Youjing Chu, Yahui Lin, Synthia H SunAbstract:The role of protein kinase C (PKC) on regulation of P2X(7) receptor-mediated Ca(2+) signalling was examined on RBA-2 Astrocytes. Activation of PKC decreased the receptor-mediated Ca(2+) signalling and the decrease was restored by PKC inhibitors. Down regulation of PKC also caused a decrease in the Ca(2+) signalling. Thus PKC might play a dual role on the P2X(7) receptor signalling. Successive stimulation of the P2X(7) receptor induced a gradual decLine of Ca(2+) signalling but PKC inhibitors failed to restore the decLine. Nevertheless, PMA stimulated translocation of PKC-alpha, -betaI, -betaII, and -gamma, but only anti-PKC-gamma co-immunoprecipitated the receptors. To examine the role of PKC-gamma, Ca(2+) signalling was measured by Ca(2+) imaging. Our results revealed that the agonist-stimulated Ca(2+) signalling were reduced in the Cells that the transfection of either P2X(7) receptor or PKC-gamma morpholino antisense oligo was identified. Thus, we concluded that PKC-gamma interacted with P2X(7) receptor complex and positively regulated the receptor-mediated Ca(2+) signalling.
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activation of p2x7 purinoceptor stimulated tgf β1 mrna expression involves pkc mapk signalling pathway in a rat brain derived type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Yuanyi Chang, Synthia H SunAbstract:The present study investigates the receptor and mechanisms involved in ATP-stimulated transforming growth factor-beta 1 (TGF-beta 1) mRNA expression of a type-2 Astrocyte Cell Line, RBA-2. RT-PCR analysis revealed that RBA-2 type-2 Astrocytes possess abundant P2X(4) and P2X(7) receptors. ATP and P2X(7) receptor-sensitive agonist, BzATP, both stimulated TGF-beta 1 mRNA expression in a time and dose-dependent manner. The stimulation required a minimum of 500 muM ATP; BzATP was much more potent that ATP, and P2X(7)-selective antagonist, oATP, inhibited the effects. In addition, ATP metabolites ADP, AMP and adenosine were ineffective in stimulation of TGF-beta 1 mRNA expression. Thus, the effect of ATP was mediated through the P2X(7) receptors. To investigate further the mechanisms by which the P2X(7) receptor mediated the TGF-beta 1 mRNA expression, the Cells were treated with inhibitors for mitogen-activated kinase (MAPK) or protein kinase C (PKC), PD98059 or GF109203X, respectively. Both PD98059 and GF109203X inhibited the ATP-stimulated TGF-beta 1 mRNA expression. Furthermore, ATP and BzATP stimulated ERK1/2 activation and the activation was inhibited by PKC inhibitors, GF109203X and Go6976. In conclusion, activation of P2X(7) receptors enhanced TGF-beta 1 mRNA expression and the effect involved PKC/MAPK signalling pathway in RBA-2 type-2 Astrocytes.
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endothelin 1 stimulated capacitative ca2 entry through eta receptors of a rat brain derived type 1 Astrocyte Cell Line ia 1g1
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Amos C Hung, Hungjung Lin, Synthia H SunAbstract:Abstract The present study demonstrated that endotheLine-1 (ET-1) stimulated a biphasic (transient and sustained) increase in [Ca 2+ ] i and signaling was blocked by BQ123 and inhibited by BQ788. RT-PCR analysis revealed that ET A was expressed more than ET B mRNA—suggesting that ET A is the major receptor. Simply reintroducing Ca 2+ in the buffer stimulated a sustained increase in [Ca 2+ ] i and the effect was inhibited by U73122, thapsigargin (TG), miconazole and SKF96365. When measured in Ca 2+ -free buffer, the ET-1-stimulated Ca 2+ transient decreased by 73% and the reintroduction of Ca 2+ induced a large sustained increase in [Ca 2+ ] i . These effects were not affected by nifedipine, but were inhibited by miconazole and SKF96365—indicating that the sustained increase in [Ca 2+ ] i mediated by ET-1 was mostly due to capacitative Ca 2+ entry (CCE). The ET-1-induced CCE was inhibited by phorbol ester (PMA) but was enhanced by GF109203X; it was also enhanced by 8-bromo-cyclic AMP (8-Br-cAMP) but was inhibited by H89. Thus, protein kinase C (PKC) negatively regulated and cAMP-dependent protein kinase (PKA) positively regulated the ET-1-mediated CCE in these Cells.
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atp stimulated ca2 influx and phospholipase d activities of a rat brain derived type 2 Astrocyte Cell Line rba 2 are mediated through p2x7 receptors
Journal of Neurochemistry, 2002Co-Authors: Synthia H Sun, Amos C Hung, Lianbin Lin, Jonson KuoAbstract:This study characterizes and examines the P2 receptor-mediated signal transduction pathway of a rat brain-derived type 2 Astrocyte Cell Line, RBA-2. ATP induced Ca2+ influx and activated phospholipase D (PLD). The ATP-stimulated Ca2+ influx was inhibited by pretreating Cells with P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), in a concentration-dependent manner. The agonist 2'- and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) stimulated the largest increases in intraCellular Ca2+ concentrations ([Ca2+]i); ATP, 2-methylthioadenosine triphosphate tetrasodium, and ATPgammaS were much less effective, whereas UTP, ADP, alpha,beta-methylene-ATP, and beta,gamma-methylene-ATP were ineffective. Furthermore, removal of extraCellular Mg2+ enhanced the ATP- and BzATP-stimulated increases in [Ca2+]i. BzATP stimulated PLD in a concentration- and time-dependent manner that could be abolished by removal of extraCellular Ca2+ and was inhibited by suramin, PPADS, and oxidized ATP. In addition, PLD activities were activated by the Ca2+ mobilization agent, ionomycin, in an extraCellular Ca2+ concentration-dependent manner. Both staurosporine and prolonged phorbol ester treatment inhibited BzATP-stimulated PLD activity. Taken together, these data indicate that activation of the P2X7 receptors induces Ca2+ influx and stimulates a Ca2+-dependent PLD in RBA-2 Astrocytes. Furthermore, protein kinase C regulates this PLD.
Chiamei Wang - One of the best experts on this subject based on the ideXlab platform.
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activation of p2x7 purinoceptor stimulated tgf β1 mrna expression involves pkc mapk signalling pathway in a rat brain derived type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Yuanyi ChangAbstract:The present study investigates the receptor and mechanisms involved in ATP-stimulated transforming growth factor-beta 1 (TGF-β1) mRNA expression of a type-2 Astrocyte Cell Line, RBA-2. RT-PCR analysis revealed that RBA-2 type-2 Astrocytes possess abundant P2X4 and P2X7 receptors. ATP and P2X7 receptor-sensitive agonist, BzATP, both stimulated TGF-β1 mRNA expression in a time and dose-dependent manner. The stimulation required a minimum of 500 μM ATP; BzATP was much more potent that ATP, and P2X7-selective antagonist, oATP, inhibited the effects. In addition, ATP metabolites ADP, AMP and adenosine were ineffective in stimulation of TGF-β1 mRNA expression. Thus, the effect of ATP was mediated through the P2X7 receptors. To investigate further the mechanisms by which the P2X7 receptor mediated the TGF-β1 mRNA expression, the Cells were treated with inhibitors for mitogen-activated kinase (MAPK) or protein kinase C (PKC), PD98059 or GF109203X, respectively. Both PD98059 and GF109203X inhibited the ATP-stimulated TGF-β1 mRNA expression. Furthermore, ATP and BzATP stimulated ERK1/2 activation and the activation was inhibited by PKC inhibitors, GF109203X and Go6976. In conclusion, activation of P2X7 receptors enhanced TGF-β1 mRNA expression and the effect involved PKC/MAPK signalling pathway in RBA-2 type-2 Astrocytes.
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activation of p2x7 purinoceptor stimulated tgf β1 mrna expression involves pkc mapk signalling pathway in a rat brain derived type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Yuanyi Chang, Synthia H SunAbstract:The present study investigates the receptor and mechanisms involved in ATP-stimulated transforming growth factor-beta 1 (TGF-beta 1) mRNA expression of a type-2 Astrocyte Cell Line, RBA-2. RT-PCR analysis revealed that RBA-2 type-2 Astrocytes possess abundant P2X(4) and P2X(7) receptors. ATP and P2X(7) receptor-sensitive agonist, BzATP, both stimulated TGF-beta 1 mRNA expression in a time and dose-dependent manner. The stimulation required a minimum of 500 muM ATP; BzATP was much more potent that ATP, and P2X(7)-selective antagonist, oATP, inhibited the effects. In addition, ATP metabolites ADP, AMP and adenosine were ineffective in stimulation of TGF-beta 1 mRNA expression. Thus, the effect of ATP was mediated through the P2X(7) receptors. To investigate further the mechanisms by which the P2X(7) receptor mediated the TGF-beta 1 mRNA expression, the Cells were treated with inhibitors for mitogen-activated kinase (MAPK) or protein kinase C (PKC), PD98059 or GF109203X, respectively. Both PD98059 and GF109203X inhibited the ATP-stimulated TGF-beta 1 mRNA expression. Furthermore, ATP and BzATP stimulated ERK1/2 activation and the activation was inhibited by PKC inhibitors, GF109203X and Go6976. In conclusion, activation of P2X(7) receptors enhanced TGF-beta 1 mRNA expression and the effect involved PKC/MAPK signalling pathway in RBA-2 type-2 Astrocytes.
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endothelin 1 stimulated capacitative ca2 entry through eta receptors of a rat brain derived type 1 Astrocyte Cell Line ia 1g1
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Amos C Hung, Hungjung Lin, Synthia H SunAbstract:Abstract The present study demonstrated that endotheLine-1 (ET-1) stimulated a biphasic (transient and sustained) increase in [Ca 2+ ] i and signaling was blocked by BQ123 and inhibited by BQ788. RT-PCR analysis revealed that ET A was expressed more than ET B mRNA—suggesting that ET A is the major receptor. Simply reintroducing Ca 2+ in the buffer stimulated a sustained increase in [Ca 2+ ] i and the effect was inhibited by U73122, thapsigargin (TG), miconazole and SKF96365. When measured in Ca 2+ -free buffer, the ET-1-stimulated Ca 2+ transient decreased by 73% and the reintroduction of Ca 2+ induced a large sustained increase in [Ca 2+ ] i . These effects were not affected by nifedipine, but were inhibited by miconazole and SKF96365—indicating that the sustained increase in [Ca 2+ ] i mediated by ET-1 was mostly due to capacitative Ca 2+ entry (CCE). The ET-1-induced CCE was inhibited by phorbol ester (PMA) but was enhanced by GF109203X; it was also enhanced by 8-bromo-cyclic AMP (8-Br-cAMP) but was inhibited by H89. Thus, protein kinase C (PKC) negatively regulated and cAMP-dependent protein kinase (PKA) positively regulated the ET-1-mediated CCE in these Cells.
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activation of p2x7 receptors induced 3h gaba release from the rba 2 type 2 Astrocyte Cell Line through a cl hco3 dependent mechanism
Glia, 2002Co-Authors: Chiamei Wang, Yuanyi ChangAbstract:: ATP is an important signaling molecule in the nervous system and it's signaling is mediated through the metabotropic P2Y and ionotropic P2X receptors. ATP is known to stimulate Ca(2+) influx and phospholipase D (PLD) activity in the type-2 Astrocyte Cell Line, RBA-2; in this study, we show that the release of preloaded [(3)H]GABA from RBA-2 Cells is mediated through the P2X(7) receptors. ATP and the ATP analogue 3'-O-(4-benoylbenoyl)-adenosine-5'-triphosphate (BzATP) both stimulated [(3)H]GABA release in a concentration dependent manner, while the nonselective P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), the P2X(7)-sensitive antagonist oxidized ATP (oATP), and high extraCellular Mg(2+) all inhibited the ATP-stimulated [(3)H]GABA release. The ATP-stimulated [(3)H]GABA release was not affected neither by removing extraCellular Na(+) nor by changes in the intraCellular or extraCellular Ca(2+) concentration. The GABA transporter inhibitors nipecotic acid and beta-alanine also had no effect. The ATP-stimulated [(3)H]GABA release was blocked, however, when media Cl(-) was replaced with gluconate and when extraCellular HCO(3)(-) was removed. The Cl(-) channel/exchanger blockers 4,4'-diisothiocyanatostilbene-2',2'-disulfonic acid (DIDS) and 4-acetamido-4'- isothiocyanatostilbene-2',2'-disulfonic acids (SITS), but not diphenylamine-2-carboxylic acid (DPC) and furosemide, blocked the ATP-stimulated [(3)H]GABA release. The anionic selectivity of the process was F(-) > Cl(-) > Br(-) which is the same as that reported for volume-sensitive Cl(-) conductance. Treating Cells with phorbol-12-myristate 13-acetate (PMA), forskolin, dibutyryl-cAMP, PD98059, neomycin, and D609 all inhibited the ATP-stimulated [(3)H]GABA release. We concluded that in RBA-2 Cells, ATP stimulates [(3)H]GABA release through the P2X(7) receptors via a Cl(-)/HCO(3)(-)-dependent mechanism that is regulated by PKC, PKA, MEK/ERK, and PLD.
Yuanyi Chang - One of the best experts on this subject based on the ideXlab platform.
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activation of p2x7 purinoceptor stimulated tgf β1 mrna expression involves pkc mapk signalling pathway in a rat brain derived type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Yuanyi ChangAbstract:The present study investigates the receptor and mechanisms involved in ATP-stimulated transforming growth factor-beta 1 (TGF-β1) mRNA expression of a type-2 Astrocyte Cell Line, RBA-2. RT-PCR analysis revealed that RBA-2 type-2 Astrocytes possess abundant P2X4 and P2X7 receptors. ATP and P2X7 receptor-sensitive agonist, BzATP, both stimulated TGF-β1 mRNA expression in a time and dose-dependent manner. The stimulation required a minimum of 500 μM ATP; BzATP was much more potent that ATP, and P2X7-selective antagonist, oATP, inhibited the effects. In addition, ATP metabolites ADP, AMP and adenosine were ineffective in stimulation of TGF-β1 mRNA expression. Thus, the effect of ATP was mediated through the P2X7 receptors. To investigate further the mechanisms by which the P2X7 receptor mediated the TGF-β1 mRNA expression, the Cells were treated with inhibitors for mitogen-activated kinase (MAPK) or protein kinase C (PKC), PD98059 or GF109203X, respectively. Both PD98059 and GF109203X inhibited the ATP-stimulated TGF-β1 mRNA expression. Furthermore, ATP and BzATP stimulated ERK1/2 activation and the activation was inhibited by PKC inhibitors, GF109203X and Go6976. In conclusion, activation of P2X7 receptors enhanced TGF-β1 mRNA expression and the effect involved PKC/MAPK signalling pathway in RBA-2 type-2 Astrocytes.
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activation of p2x7 purinoceptor stimulated tgf β1 mrna expression involves pkc mapk signalling pathway in a rat brain derived type 2 Astrocyte Cell Line rba 2
Cellular Signalling, 2003Co-Authors: Chiamei Wang, Yuanyi Chang, Synthia H SunAbstract:The present study investigates the receptor and mechanisms involved in ATP-stimulated transforming growth factor-beta 1 (TGF-beta 1) mRNA expression of a type-2 Astrocyte Cell Line, RBA-2. RT-PCR analysis revealed that RBA-2 type-2 Astrocytes possess abundant P2X(4) and P2X(7) receptors. ATP and P2X(7) receptor-sensitive agonist, BzATP, both stimulated TGF-beta 1 mRNA expression in a time and dose-dependent manner. The stimulation required a minimum of 500 muM ATP; BzATP was much more potent that ATP, and P2X(7)-selective antagonist, oATP, inhibited the effects. In addition, ATP metabolites ADP, AMP and adenosine were ineffective in stimulation of TGF-beta 1 mRNA expression. Thus, the effect of ATP was mediated through the P2X(7) receptors. To investigate further the mechanisms by which the P2X(7) receptor mediated the TGF-beta 1 mRNA expression, the Cells were treated with inhibitors for mitogen-activated kinase (MAPK) or protein kinase C (PKC), PD98059 or GF109203X, respectively. Both PD98059 and GF109203X inhibited the ATP-stimulated TGF-beta 1 mRNA expression. Furthermore, ATP and BzATP stimulated ERK1/2 activation and the activation was inhibited by PKC inhibitors, GF109203X and Go6976. In conclusion, activation of P2X(7) receptors enhanced TGF-beta 1 mRNA expression and the effect involved PKC/MAPK signalling pathway in RBA-2 type-2 Astrocytes.
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activation of p2x7 receptors induced 3h gaba release from the rba 2 type 2 Astrocyte Cell Line through a cl hco3 dependent mechanism
Glia, 2002Co-Authors: Chiamei Wang, Yuanyi ChangAbstract:: ATP is an important signaling molecule in the nervous system and it's signaling is mediated through the metabotropic P2Y and ionotropic P2X receptors. ATP is known to stimulate Ca(2+) influx and phospholipase D (PLD) activity in the type-2 Astrocyte Cell Line, RBA-2; in this study, we show that the release of preloaded [(3)H]GABA from RBA-2 Cells is mediated through the P2X(7) receptors. ATP and the ATP analogue 3'-O-(4-benoylbenoyl)-adenosine-5'-triphosphate (BzATP) both stimulated [(3)H]GABA release in a concentration dependent manner, while the nonselective P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), the P2X(7)-sensitive antagonist oxidized ATP (oATP), and high extraCellular Mg(2+) all inhibited the ATP-stimulated [(3)H]GABA release. The ATP-stimulated [(3)H]GABA release was not affected neither by removing extraCellular Na(+) nor by changes in the intraCellular or extraCellular Ca(2+) concentration. The GABA transporter inhibitors nipecotic acid and beta-alanine also had no effect. The ATP-stimulated [(3)H]GABA release was blocked, however, when media Cl(-) was replaced with gluconate and when extraCellular HCO(3)(-) was removed. The Cl(-) channel/exchanger blockers 4,4'-diisothiocyanatostilbene-2',2'-disulfonic acid (DIDS) and 4-acetamido-4'- isothiocyanatostilbene-2',2'-disulfonic acids (SITS), but not diphenylamine-2-carboxylic acid (DPC) and furosemide, blocked the ATP-stimulated [(3)H]GABA release. The anionic selectivity of the process was F(-) > Cl(-) > Br(-) which is the same as that reported for volume-sensitive Cl(-) conductance. Treating Cells with phorbol-12-myristate 13-acetate (PMA), forskolin, dibutyryl-cAMP, PD98059, neomycin, and D609 all inhibited the ATP-stimulated [(3)H]GABA release. We concluded that in RBA-2 Cells, ATP stimulates [(3)H]GABA release through the P2X(7) receptors via a Cl(-)/HCO(3)(-)-dependent mechanism that is regulated by PKC, PKA, MEK/ERK, and PLD.
Manfred Huettinger - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of chondroitin sulfate bioactivity in hippocampal neurones and the Astrocyte Cell Line U373: influence of position of sulfate groups and charge density.
Basic & clinical pharmacology & toxicology, 2005Co-Authors: Alfred Rapp, Nina Brandl, Nicola Volpi, Manfred HuettingerAbstract:Abstract: Chondroitin sulfates are Linear polysaccharides of alternating glucuronic acid and N-acetylgalactosamine, sulfated in varying positions. They form the extraCellular framework providing the information for the structural establishment of tissues in multiCellular organisms. Growth cones of neurones modulate their outgrowth according to signals received from proteoglycans. The exact molecular structures behind these functions are not fully understood, but structural details of the carbohydrate backbone are crucial. In this report we have employed quantitative cytometry on hippocampal neurite outgrowth in the presence of chondroitin sulfate added in solution to determine the influence of the position and density of the sulfate groups of the N-acetyl-D-galactosamine-residues of chondroitin sulfates. It is of profound interest whether externally added chondroitin sulfates can compete with core protein bound chondroitin sulfate to modulate the effects of tissue-synthesized matrix. In series of microscopic images 3 parameters of neuritic outgrowth activity, neurite length, number of neurites and fasciculation (thickness of neurites) are analyzed at concentrations occurring in intact tissues. Fasciculation increased and number of neurites decreased with high di-sulfation. No significant differences on process length reduction were found between the isotypes. Specificity of effects found is emphasized, as no influence on Cell proliferation with U373 human Astrocyte Cell Line is detectable, while neurones clearly are inhibited. The IC30 and IC50 values of chondroitin sulfates isoforms are presented for neurones. The data indicate that the soluble fragments from chondroitin sulfate are actively modulating Cell development. Besides dosage, sulfation density and position are relevant for effects of chondroitin sulfate in neuronal regenerative activity.
