From the Department of Anesthesiology, School of Medicine and.
Department of Occupational Toxicology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan.
Anesth Analg. 2021 Jun 1;132(6):1756-1767. doi: 10.1213/ANE.0000000000005546.
The transient receptor potential vanilloid subtype 3 (TRPV3) channel is activated by innocuous temperature and several chemical stimuli. It is proposed to be involved in pathological pain development and is therefore considered a potential target for treating pain. Local anesthetics have been used for patients with both acute and chronic pain. Although blockage of the voltage-gated sodium channel is the primary mechanism by which local anesthetics exert their effects, they cannot be explained by this mechanism alone, especially in pathologic states such as chronic pain. Indeed, the effects of local anesthetics on multiple targets involved in the pain pathway have been reported. It has also been suggested that modulating the function of transient receptor potential (TRP) channels (eg, TRPV1 and transient receptor potential ankyrin 1 [TRPA1]) is one of the mechanisms of action of local anesthetics. However, the effects of local anesthetics on TRPV3 have not been reported.
We expressed TRPV3 in Xenopus oocytes and investigated the effects of local anesthetics on 2-aminoethoxydiphenyl borate (2APB)-induced currents using 2-electrode voltage-clamp techniques.
Clinically used local anesthetics inhibited the 2APB-activated currents from the TRPV3 channel in a concentration-dependent manner at pharmacologically relevant concentrations with half maximal inhibitory concentration (IC50) values of 2.5 (lidocaine), 1.4 (mepivacaine), 0.28 (ropivacaine), and 0.17 (bupivacaine) mmol/L, respectively. Conversely, these local anesthetics also directly induced currents at higher concentrations, although these currents were quite small compared to the 2APB-induced currents. We found that the inhibition of TRPV3 by lidocaine is noncompetitive and independent of intracellular signaling cascades. 2APB-induced TRPV3 currents were reduced by extracellular N-(2,6-dimethylphenylcarbamoylmethyl) triethylammonium bromide (QX-314) but not by intracellular QX-314 nor benzocaine. Moreover, lidocaine showed a use-dependent block in TRPV3 inhibition. Finally, QX-314 appeared to slightly permeate the activated TRPV3 channel pore based on examination of oocytes coexpressing TRPV3 and a sodium channel. These results suggest that local anesthetics could inhibit TRPV3 channel function by extracellular interactions of their charged forms with the channel pore.
Local anesthetics inhibited TRPV3 2APB-induced currents at pharmacologically relevant concentrations when TRPV3 was expressed in Xenopus oocytes. These effects seem to occur via an extracellular interaction between the charged form of the anesthetic with the TRPV3 channel pore. These results help to elucidate the mechanisms of action of local anesthetics.
瞬时受体电位香草酸亚型 3（TRPV3）通道可被无害的温度和多种化学刺激激活。它被认为与病理性疼痛的发展有关，因此被认为是治疗疼痛的潜在靶点。局部麻醉剂已用于治疗急性和慢性疼痛的患者。尽管阻断电压门控钠离子通道是局部麻醉剂发挥作用的主要机制，但这一机制并不能单独解释其作用，尤其是在慢性疼痛等病理状态下。事实上，已经报道了局部麻醉剂对参与疼痛途径的多个靶点的影响。此外，调节瞬时受体电位（TRP）通道（例如 TRPV1 和瞬时受体电位锚蛋白 1[TRPA1]）的功能被认为是局部麻醉剂的作用机制之一。然而，尚未报道局部麻醉剂对 TRPV3 的影响。
我们在非洲爪蟾卵母细胞中表达 TRPV3，并使用双电极电压钳技术研究局部麻醉剂对 2-氨基乙氧基二苯硼酸盐（2APB）诱导电流的影响。
临床上使用的局部麻醉剂以浓度依赖性方式抑制 TRPV3 通道的 2APB 激活电流，在药理学相关浓度下具有半数最大抑制浓度（IC50）值，分别为 2.5（利多卡因）、1.4（甲哌卡因）、0.28（罗哌卡因）和 0.17（布比卡因）mmol/L。相反，这些局部麻醉剂在更高的浓度下也直接诱导电流，尽管与 2APB 诱导的电流相比，这些电流相当小。我们发现，利多卡因对 TRPV3 的抑制是非竞争性的，且不依赖于细胞内信号级联。QX-314 可减少 2APB 诱导的 TRPV3 电流，但细胞内 QX-314 和苯佐卡因不能。此外，利多卡因在 TRPV3 抑制中表现出使用依赖性阻断。最后，基于共表达 TRPV3 和钠通道的卵母细胞的检查，QX-314 似乎略微渗透激活的 TRPV3 通道孔。这些结果表明，局部麻醉剂可能通过其带电形式与通道孔的细胞外相互作用抑制 TRPV3 通道功能。
当 TRPV3 在非洲爪蟾卵母细胞中表达时，局部麻醉剂在药理学相关浓度下抑制 TRPV3 2APB 诱导的电流。这些作用似乎是通过麻醉剂的带电形式与 TRPV3 通道孔之间的细胞外相互作用发生的。这些结果有助于阐明局部麻醉剂的作用机制。
