Department of Biophysics, Faculty of Medicine, University of Suleyman Demirel, Isparta, Turkey.
Physiol Behav. 2012 May 15;106(2):122-8. doi: 10.1016/j.physbeh.2012.01.014. Epub 2012 Jan 24.
N-acetylcysteine (NAC) is a thiol-containing (sulphydryl donor) antioxidant, which contributes to regeneration of glutathione (GSH) and also acts through a direct reaction with free radicals. Thiol depletion has been implicated in the neurobiology of sensory neurons and pain. We reported recently an activator role of intracellular GSH depletion on calcium influx through transient receptor potential melastatin-like 2 (TRPM2) channels in rat dorsal root ganglion (DRG). NAC may have a protective role on calcium influx through regulation of TRPM2 channels in the neurons. Therefore, we tested the effects of NAC on TRPM2 channel currents in cytosolic GSH depleted DRG in rats. DRG neurons were freshly isolated from rats and the neurons were incubated for 24 h with buthionine sulfoximine (BSO). In whole-cell patch clamp experiments, TRPM2 currents in the DRG incubated with BSO were gated by H(2)O(2). TRPM2 channels current densities, cytosolic free Ca(2+) content, and lipid peroxidation values in the neurons were higher in H(2)O(2) and BSO + H(2)O(2) group than in controls; however GSH and GSH peroxidase (GSH-Px) values were decreased. BSO + H(2)O(2)-induced TRPM2 channel gating was totally inhibited by extracellular NAC and partially inhibited by 2-aminoethyl diphenylborinate. GSH-Px activity, lipid peroxidation and GSH levels in the DRG neurons were also modulated by NAC. In conclusion, we observed a modulator role of NAC on Ca(2+) influx through a TRPM2 channel in intracellular GSH depleted DRG neurons. NAC incubation before BSO exposure appears to be more protective than NAC incubation after BSO exposure. Since cytosolic thiol group depletion is a common feature of neuropathic pain, our findings are relevant to the etiology and treatment of pain neuropathology in DRG neurons.
N-乙酰半胱氨酸（NAC）是一种含巯基（硫醇供体）的抗氧化剂，可促进谷胱甘肽（GSH）的再生，还可通过与自由基直接反应发挥作用。巯基耗竭与感觉神经元和疼痛的神经生物学有关。我们最近报道了细胞内 GSH 耗竭通过瞬时受体电位 melastatin 样 2（TRPM2）通道对大鼠背根神经节（DRG）中钙内流的激活作用。NAC 可能通过调节神经元中的 TRPM2 通道对钙内流具有保护作用。因此，我们测试了 NAC 对胞质 GSH 耗竭大鼠 DRG 中 TRPM2 通道电流的影响。从大鼠中分离出 DRG 神经元，并将神经元与丁硫氨酸亚砜胺（BSO）孵育 24 小时。在全细胞膜片钳实验中，用 H 2 O 2 门控 DRG 孵育的 BSO 中的 TRPM2 电流。与对照组相比，在 H 2 O 2 和 BSO + H 2 O 2 组中，神经元中的 TRPM2 通道电流密度、胞质游离 Ca 2+含量和脂质过氧化值较高；然而，GSH 和 GSH 过氧化物酶（GSH-Px）值降低。BSO + H 2 O 2 诱导的 TRPM2 通道门控完全被细胞外 NAC 抑制，部分被 2-氨基乙基二苯基硼酸抑制。NAC 还调节 DRG 神经元中的 GSH-Px 活性、脂质过氧化和 GSH 水平。总之，我们观察到 NAC 对细胞内 GSH 耗竭的 DRG 神经元中通过 TRPM2 通道的 Ca 2+内流具有调节剂作用。在 BSO 暴露前孵育 NAC 比在 BSO 暴露后孵育 NAC 更具保护作用。由于胞质巯基基团耗竭是神经病理性疼痛的共同特征，我们的研究结果与 DRG 神经元中疼痛神经病理学的病因和治疗有关。
