Suppressed Ca2+/CaM/CaMKII-dependent KATP channel activity in primary afferent neurons mediates hyperalgesia after axotomy
Suppressed Ca2+/CaM/CaMKII-dependent KATP channel activity in primary afferent neurons mediates hyperalgesia after axotomy
复制标题
DOI：
10.1073/pnas.0901815106
复制
发表时间：
2009-05-26
影响因子：
11.1
通讯作者：
Sarantopoulos, Constantine
中科院分区：
文献类型：
--
作者：
Kawano, Takashi;Zoga, Vasiliki;Sarantopoulos, Constantine
疼痛性轴索切断术会降低初级传入神经元中的 K-ATP 通道电流 (IKATP)。由于受损的背根神经节 (DRG) 神经元中胞质 Ca2+ 信号传导受到抑制，因此我们研究了 Ca2+-钙调蛋白 (CaM)-Ca2+/CaM 依赖性激酶 II (CaMKII) 是否调节大 DRG 神经元中的 IKATP。免疫组织化学鉴定出神经丝 200 阳性 DRG 体细胞中存在 K-ATP 通道亚基 SUR1、SUR2 和 Kir6.2，但不存在 Kir6.1 和 pCaMKII。细胞贴附斑块的单通道记录显示，离子霉素（一种 Ca2+ 离子载体）的基础 IKATP 和诱发 IKATP 被 CaMKII 激活。在通过脊髓神经结扎（SNL）产生痛觉过敏的大鼠的轴突神经元中，基础K-ATP通道活性降低，并且消除了对离子霉素的敏感性。在分离出神经元的大鼠中，基础和 Ca2+ 诱发的 K-ATP 通道活性与 SNL 诱导的痛觉过敏程度呈负相关。格苯脲（一种选择性 K-ATP 通道抑制剂）对 IKATP 的抑制作用，在穿孔的全细胞贴片中记录去极化静息膜电位 (RMP)，并通过电流分析法测量增强的神经递质释放。选择性 K-ATP 通道开放剂二氮嗪使 RMP 超极化并减弱神经递质释放。因 SNL 而产生痛觉过敏的大鼠的轴突神经元失去了对肉豆蔻酰化形式的自卡肽 2 相关抑制肽 (AIPm)（一种 CaMKII 的假底物阻断剂）的敏感性，而来自未发生痛觉过敏的 SNL 动物的轴突神经元则显示出 AIPm 正常的 IKATP 抑制作用。 AIPm 还通过 K-ATP 通道抑制使对照神经元中的 RMP 去极化。即使在疼痛性神经损伤后，K-ATP 通道的单一电流电导和对胞质 ATP 和配体的敏感性也得以保留，从而为选择性治疗神经性疼痛提供了机会。
Painful axotomy decreases K-ATP channel current (IKATP) in primary afferent neurons. Because cytosolic Ca2+ signaling is depressed in injured dorsal root ganglia (DRG) neurons, we investigated whether Ca2+-calmodulin (CaM)-Ca2+/CaM-dependent kinase II (CaMKII) regulates IKATP in large DRG neurons. Immunohistochemistry identified the presence of K-ATP channel subunits SUR1, SUR2, and Kir6.2 but not Kir6.1, and pCaMKII in neurofilament 200-positive DRG somata. Single-channel recordings from cell-attached patches revealed that basal and evoked IKATP by ionomycin, a Ca2+ ionophore, is activated by CaMKII. In axotomized neurons from rats made hyperalgesic by spinal nerve ligation (SNL), basal K-ATP channel activity was decreased, and sensitivity to ionomycin was abolished. Basal and Ca2+-evoked K-ATP channel activity correlated inversely with the degree of hyperalgesia induced by SNL in the rats from which the neurons were isolated. Inhibition of IKATP by glybenclamide, a selective K-ATP channel inhibitor, depolarized resting membrane potential (RMP) recorded in perforated whole-cell patches and enhanced neurotransmitter release measured by amperometry. The selective K-ATP channel opener diazoxide hyperpolarized the RMP and attenuated neurotransmitter release. Axotomized neurons from rats made hyperalgesic by SNL lost sensitivity to the myristoylated form of autocamtide-2-related inhibitory peptide (AIPm), a pseudosubstrate blocker of CaMKII, whereas axotomized neurons from SNL animals that failed to develop hyperalgesia showed normal IKATP inhibition by AIPm. AIPm also depolarized RMP in control neurons via K-ATP channel inhibition. Unitary current conductance and sensitivity of K-ATP channels to cytosolic ATP and ligands were preserved even after painful nerve injury, thus providing opportunities for selective therapeutic targeting against neuropathic pain.