Nazıroğlu Mustafa
Neuroscience Research Center, Süleyman Demirel University, Isparta, Turkey.
Tıp Fakültesi, Biyofizik Anabilim Dalı Başkanı, Süleyman Demirel University, 32260, Isparta, TR, Turkey.
J Mol Neurosci. 2017 Mar;61(3):425-435. doi: 10.1007/s12031-017-0882-4. Epub 2017 Jan 17.
Despite considerable research, the mechanisms of neuropathic pain induced by excessive oxidative stress production and overload calcium ion (Ca) entry in dorsal root ganglion (DRG) remain substantially unidentified. The transient receptor potential melastatin 2 (TRPM2) and vanilloid 1 (TRPV1) channels are activated with different stimuli including oxidative stress. TRPM2 and TRPV1 have been shown to be involved in induction of neuropathic pain. However, the activation mechanisms of TRPM2 and TRPV1 via NADPH oxidase and protein kinase C (PKC) pathways are poorly understood. In this study, I investigated the roles of NADPH oxidase and PKC on Ca entry through TRPM2 and TRPV1 channels in in vitro DRG neurons of rats. Rat DRG neurons were used in whole-cell patch clamp experiments. The HO-induced TRPM2 current densities were decreased by N-(p-amylcinnamoyl)anthranilic acid (ACA), and dose-dependent capsaicin (CAP) and HO-induced TRPV1 currents were inhibited by capsazepine (CPZ). The TRPV1 channel is activated in the DRG neurons by 0.01 mM capsaicin but not 0.001 mM or 0.05 mM capsaicin. TRPM2 and TRPV1 currents were increased by the PKC activator, phorbol myristate acetate (PMA), although the currents were decreased by ACA, CPZ, and the PKC inhibitor, bisindolylmaleimide I (BIM). Both channel currents were further increased by PMA + HO as compared to HO only. In the combined presence of PMA + BIM, no TRPM2 or TRPV1 currents were observed. The CAP and HO-induced TRPM2 current densities were also decreased by the NADPH oxidase inhibitors apocynin and N-Acetylcysteine. In conclusion, these results demonstrate a protective role for NADPH oxidase and PKC inhibitors on Ca entry through TRPM2 and TRPV1 channels in DRG neurons. Since excessive oxidative stress production and Ca entry are implicated in the pathophysiology of neuropathic pain, the findings may be relevant to the etiology and treatment of neuropathology in DRG neurons.
尽管进行了大量研究，但背根神经节（DRG）中因过度产生氧化应激和钙离子（Ca）内流过载而导致神经性疼痛的机制仍基本不明。瞬时受体电位香草酸亚家族成员2（TRPM2）和香草酸受体1（TRPV1）通道可被包括氧化应激在内的不同刺激激活。TRPM2和TRPV1已被证明与神经性疼痛的诱导有关。然而，通过烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶和蛋白激酶C（PKC）途径激活TRPM2和TRPV1的机制却知之甚少。在本研究中，我研究了NADPH氧化酶和PKC在大鼠体外DRG神经元中通过TRPM2和TRPV1通道介导的Ca内流中的作用。大鼠DRG神经元用于全细胞膜片钳实验。N-（对戊基肉桂酰基）邻氨基苯甲酸（ACA）降低了过氧化氢（HO）诱导的TRPM2电流密度，辣椒素（CAP）呈剂量依赖性地抑制HO诱导的TRPV1电流，而辣椒素受体拮抗剂（CPZ）抑制了TRPV1电流。在DRG神经元中，0.01 mM辣椒素可激活TRPV1通道，但0.001 mM或0.05 mM辣椒素则不能。PKC激活剂佛波醇肉豆蔻酸酯乙酸酯（PMA）增加了TRPM2和TRPV1电流，尽管ACA、CPZ和PKC抑制剂双吲哚马来酰亚胺I（BIM）降低了电流。与仅用HO相比，PMA + HO进一步增加了两种通道电流。在PMA + BIM共同存在的情况下，未观察到TRPM2或TRPV1电流。NADPH氧化酶抑制剂夹竹桃麻素和N-乙酰半胱氨酸也降低了CAP和HO诱导的TRPM2电流密度。总之，这些结果证明了NADPH氧化酶和PKC抑制剂对DRG神经元中通过TRPM2和TRPV1通道的Ca内流具有保护作用。由于过度产生氧化应激和Ca内流与神经性疼痛的病理生理学有关，这些发现可能与DRG神经元神经病理学的病因和治疗相关。
