Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium.
Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium; Department of Urology, University Hospitals Leuven, Leuven, Belgium.
Eur J Pharmacol. 2023 Mar 5;942:175512. doi: 10.1016/j.ejphar.2023.175512. Epub 2023 Jan 16.
and purpose: Phenazopyridine (PAP) is an over-the-counter drug widely used to provide symptomatic relief of bladder pain in conditions such as cystitis or bladder pain syndrome (BPS). Whereas the analgesic effect of PAP has been attributed to a local effect on the mucosa of the lower urinary tract (LUT), the molecular targets of PAP remain unknown. We investigated the effect of PAP on pain-related Transient Receptor Potential (TRP) channels expressed in sensory neurons that innervate the bladder wall.
The effects of PAP on the relevant TRP channels (TRPV1, TRPA1, TRPM8, TRPM3) expressed in HEK293 or CHO cells was investigated using Fura-2-based calcium measurements and whole-cell patch-clamp recordings. Activity of PAP on TRPM8 was further analysed using Fura-2-based calcium imaging on sensory neurons isolated from lumbosacral dorsal root ganglia (DRG) of mice.
PAP rapidly and reversibly inhibits responses of TRPM8 expressed in HEK293 cells to cold and menthol, with IC values between 2 and 10 μM. It acts by shifting the voltage dependence of channel activation towards positive potentials, opposite to the effect of menthol. PAP also inhibits TRPM8-mediated, menthol-evoked calcium responses in lumbosacral DRG neurons. At a concentration of 10 μM, PAP did not significantly affect TRPA1, TRPV1, or TRPM3.
PAP inhibits TRPM8 in a concentration range consistent with PAP levels in the urine of treated patients. Since TRPM8 is expressed in bladder afferent neurons and upregulated in patients with painful bladder disorders, TRPM8 inhibition may underlie the analgesic activity of PAP.
匹那酯（PAP）是一种非处方药物，广泛用于缓解膀胱炎或膀胱疼痛综合征（BPS）等疾病的膀胱疼痛症状。虽然 PAP 的镇痛作用归因于对下尿路（LUT）黏膜的局部作用，但 PAP 的分子靶点仍不清楚。我们研究了 PAP 对支配膀胱壁的感觉神经元中表达的与疼痛相关的瞬时受体电位（TRP）通道的影响。
使用 Fura-2 基础钙测量和全细胞膜片钳记录研究了 PAP 对在 HEK293 或 CHO 细胞中表达的相关 TRP 通道（TRPV1、TRPA1、TRPM8、TRPM3）的影响。使用 Fura-2 基础钙成像进一步分析了 PAP 对从小鼠腰骶部背根神经节（DRG）分离的感觉神经元中表达的 TRPM8 的活性。
PAP 快速且可逆地抑制了 HEK293 细胞中表达的 TRPM8 对冷和薄荷醇的反应，IC 值在 2 至 10 μM 之间。它通过将通道激活的电压依赖性向正电位移动起作用，与薄荷醇的作用相反。PAP 还抑制了腰骶部 DRG 神经元中 TRPM8 介导的薄荷醇诱发的钙反应。在 10 μM 浓度下，PAP 对 TRPA1、TRPV1 或 TRPM3 没有明显影响。
PAP 在与治疗患者尿液中 PAP 水平一致的浓度范围内抑制 TRPM8。由于 TRPM8 表达在膀胱传入神经元中，并在上皮细胞过度表达，因此，TRPM8 抑制可能是 PAP 镇痛作用的基础。
