Opioid withdrawal increases transient receptor potential vanilloid 1 activity in a protein kinase A-dependent manner
Opioid withdrawal increases transient receptor potential vanilloid 1 activity in a protein kinase A-dependent manner
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DOI：
10.1016/j.pain.2012.12.026
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发表时间：
2013-04-01
期刊：
影响因子：
7.4
通讯作者：
Zoellner, Christian
中科院分区：
文献类型：
--
作者：
Spahn, Viola;Fischer, Oliver;Zoellner, Christian
痛觉过敏是阿片类药物戒断的主要症状。瞬时受体电位香草样蛋白1 （TRPV1）是一种配体门控离子通道，在感觉神经元上表达，对有害热量、质子和辣椒素等化学刺激作出反应。TRPV1可以通过mu-阿片受体（MOR）介导的腺苷酸环化酶（ACs）活性降低和环磷酸腺苷（cAMP）水平降低来抑制。相比之下，慢性MOR激活后的阿片类药物戒断揭示了AC超激活以及随后cAMP和蛋白激酶A （PKA）活性的增加。在这里，我们研究了(1)阿片类药物戒断期间cAMP的增加是否会增加TRPV1的活性；(2)阿片类药物戒断如何调节辣椒素诱导的大鼠有害行为。我们应用了全细胞膜片钳、微荧光法、cAMP测定、放射配体结合、定点诱变和行为实验。阿片戒断显著增加转染人胚胎肾293细胞和分离背根神经节（DRG）神经元的cAMP水平和辣椒素诱导的TRPV1活性。抑制AC和PKA，以及PKA磷酸化位点苏氨酸144和丝氨酸774的突变，阻止了TRPV1活性的增强。最后，辣椒素诱导的攻击性行为在体内阿片类药物戒断期间增加。总之，我们的研究结果表明，DRG神经元中TRPV1活性的增加是阿片戒断诱导痛觉过敏的新机制。(c) 2013年国际疼痛研究协会。Elsevier b.v.版权所有。
Hyperalgesia is a cardinal symptom of opioid withdrawal. The transient receptor potential vanilloid 1 (TRPV1) is a ligand-gated ion channel expressed on sensory neurons responding to noxious heat, protons, and chemical stimuli such as capsaicin. TRPV1 can be inhibited via mu-opioid receptor (MOR)-mediated reduced activity of adenylyl cyclases (ACs) and decreased cyclic adenosine monophosphate (cAMP) levels. In contrast, opioid withdrawal following chronic activation of MOR uncovers AC superactivation and subsequent increases in cAMP and protein kinase A (PKA) activity. Here we investigated (1) whether an increase in cAMP during opioid withdrawal increases the activity of TRPV1 and (2) how opioid withdrawal modulates capsaicin-induced nocifensive behavior in rats. We applied whole-cell patch clamp, microfluorimetry, cAMP assays, radioligand binding, site-directed mutagenesis, and behavioral experiments. Opioid withdrawal significantly increased cAMP levels and capsaicin-induced TRPV1 activity in both transfected human embryonic kidney 293 cells and dissociated dorsal root ganglion (DRG) neurons. Inhibition of AC and PKA, as well as mutations of the PKA phosphorylation sites threonine 144 and serine 774, prevented the enhanced TRPV1 activity. Finally, capsaicin-induced nocifensive behavior was increased during opioid withdrawal in vivo. In summary, our results demonstrate an increased activity of TRPV1 in DRG neurons as a new mechanism contributing to opioid withdrawal-induced hyperalgesia. (c) 2013 International Association for the Study of Pain. Published by Elsevier B. V. All rights reserved.