Dual contradictory roles of cAMP signaling pathways in hydroxyl radical production in the rat striatum
Dual contradictory roles of cAMP signaling pathways in hydroxyl radical production in the rat striatum
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DOI：
10.1016/j.freeradbiomed.2012.01.002
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发表时间：
2012-03-15
影响因子：
7.4
通讯作者：
Mizukami, Hajime
中科院分区：
文献类型：
--
作者：
Hara, Shuichi;Kobayashi, Masamune;Mizukami, Hajime
研究表明，cAMP信号通路可能与活性氧的产生有关。在这项研究中，我们研究了cAMP信号的修改如何影响大鼠纹状体中羟基自由基的产生，使用微透析来测量细胞外2，3-二羟基苯甲酸（2，3-DHBA），这是水杨酸的羟基自由基加合物。高达50 nmol的细胞渗透性cAMP模拟物8-溴-cAMP（8-Br-cAMP）以剂量依赖性方式增加2，3-DHBA（在100 nmol时，2，3-DHBA没有额外的增加）。另一种cAMP模拟物，二丁酰cAMP（db-cAMP），在50 nmol时引起2，3-DHBA的非显著增加，在100 nmol时引起显著降低。高达20 nmol的毛喉素，这是腺苷酸环化酶的直接激活剂，增加2，3-DHBA，类似于8-Br-cAMP的效果;然而，毛喉素导致2，3-DHBA的更大的增加。蛋白激酶A（PKA）的有效抑制剂H89（500 μ M）增强8-Br-cAMP和毛喉素诱导的2，3-DHBA增加，并拮抗100 nmol db-cAMP的抑制作用。有趣的是，单独或与H89组合施用100 nmol 8-溴-cGMP对2，3-DHBA水平没有显著影响。100 nmol剂量的优先PKA激活剂（6-苯基-cAMP）或优先PKA抑制剂（8-溴腺苷-3 '，5'-环状单硫代磷酸酯，Rp-异构体; Rp-8-Br-cAMPS）（其也抑制cAMP介导的Epac（由cAMP直接激活的交换蛋白）的激活）分别抑制或增强2，3-DHBA的形成。高达100 nmol的8-（4-氯苯硫基）-2 '-O-甲基腺苷-cAMP（Epac的选择性激活剂）可剂量依赖性地刺激2，3-DHBA的形成。这些结果表明，cAMP信号在大鼠纹状体产生羟自由基中起着相互矛盾的作用（刺激和抑制），通过Epac和PKA的不同作用。这些作用可能有助于产生羟基自由基伴随cAMP在一氧化碳中毒，因为2，3-DHBA的形成是由PKA抑制剂H89增强和RP-8-Br-cAMPS，抑制PKA和Epac。(C)2012 Elsevier Inc. All rights reserved.
Studies have suggested that cAMP signaling pathways may be associated with the production of reactive oxygen species. In this study, we examined how modifications in cAMP signaling affected the production of hydroxyl radicals in rat striatum using microdialysis to measure extracellular 2,3-dihydroxybenzoic acid (2,3-DHBA), which is a hydroxyl radical adduct of salicylate. Up to 50 nmol of the cell-permeative cAMP mimetic 8-bromo-cAMP (8-Br-cAMP) increased 2,3-DHBA in a dose-dependent manner (there was no additional increase in 2,3-DHBA at 100 nmol). Another cAMP mimetic, dibutyryl cAMP (db-cAMP), caused a nonsignificant increase in 2,3-DHBA at 50 nmol and a significant decrease at 100 nmol. Up to 20 nmol of forskolin, which is a direct activator of adenylyl cyclase, increased 2,3-DHBA, similar to the effect of 8-Br-cAMP; however, forskolin resulted in a much greater increase in 2,3-DHBA. A potent inhibitor of protein kinase A (PKA), H89 (500 mu M), potentiated the 8-Br-cAMP- and forskolin-induced increases in 2,3-DHBA and antagonized the inhibitory effect of 100 nmol of db-cAMP. Interestingly, the administration of 100 nmol of 8-bromo-cGMP alone or in combination with H89 had no significant effect on 2,3-DHBA levels. Doses of 100 nmol of a preferential PKA activator (6-phenyl-cAMP) or a preferential PKA inhibitor (8-bromoadenosine-3',5'-cyclic monophosphorothionate, Rp-isomer; Rp-8-Br-cAMPS), which also inhibits the cAMP-mediated activation of Epac (the exchange protein directly activated by CAMP), suppressed or enhanced, respectively, the formation of 2,3-DHBA. Up to 100 nmol of 8-(4-chlorophenylthio)-2'-O-methyladenosine-cAMP, which is a selective activator of Epac, dose-dependently stimulated the formation of 2,3-DHBA. These findings suggest that cAMP signaling plays contradictory roles (stimulation and inhibition) in the production of hydroxyl radicals in rat striatum by differential actions of Epac and PKA. These roles might contribute to the production of hydroxyl radicals concomitant with cAMP in carbon monoxide poisoning, because the formation of 2,3-DHBA was potentiated by the PKA inhibitor H89 and suppressed by Rp-8-Br-cAMPS, which inhibits PKA and Epac. (C) 2012 Elsevier Inc. All rights reserved.