Objective: To explore the effects between transient receptor potential melastatin 8 (TRPM8) on pain symptom and neuronal proliferation in mice with interstitial cystitis/bladder pain syndrome (IC/BPS). Methods: Female wild-type C57BL/6 mice (8-10 weeks old) were divided into control group, IC/BPS model group, and IC/BPS model+menthol group (6 mice each) by random number table method; TRPM8 knockout mice were randomly divided into TRPM8 knockout group and TRPM8 knockout model group (6 mice each). The IC/BPS model group, the IC/BPS model+menthol group, and the TRPM8 knockout model group were injected subcutaneously with residues 65-84 of murine uroplakin 3A (UPK3A65-84). The IC/BPS model+menthol group continued to be injected with menthol. After successful modeling, the differences in pain thresholds between the groups were assessed by mechanosensitivity. The bladder wall was injected with a cell membrane red fluorescent probe (Dil), and the dorsal root ganglion (DRG) tissues were collected 10 days later. The differences in the protein and mRNA levels of TRPM8 and GAP43 in the groups were detected by Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Immunofluorescence was used to detect the distribution of TRPM8 expression with GAP43 or Dil in DRG tissues. The relationship between TRPM8 and pain symptom and its role in neuronal proliferation in IC/BPS mice were analyzed. Results: The models were all constructed successfully. Compared with the control group, the pain thresholds of mice in the IC/BPS model group and IC/BPS model+menthol group were reduced [(8.50±1.22), (5.50±1.05) vs (11.67±2.16), respectively, all P<0.001]. Compared with the control group, the expression of TRPM8 mRNA was elevated in the IC/BPS model group and IC/BPS model+menthol group, while TRPM8 was not expressed in the TRPM8 knockout group [(3.16±0.05), (6.46±0.21), and 0 vs (1.00±0.06), respectively, all P<0.001]. The expression of TRPM8 protein and mRNA in each group had the same trend (P<0.001). Compared with the control group, the expression of GAP43 mRNA in the DRG of the IC/BPS model group and the IC/BPS model+menthol group was increased, whereas the expression of GAP43 mRNA in the TRPM8 knockout model group was decreased (all P<0.001). The trend of GAP43 protein expression was the same as that of mRNA expression (P<0.001). Immunofluorescence results showed an increase in the number of GAP43-positive neurons in the DRG of the IC/BPS model group and the IC/BPS model+menthol group, and a decrease in the TRPM8 knockout group compared with the control group (all P<0.001). Compared with the control group, the number of Dil-positive neurons in the DRG of the IC/BPS model group and the IC/BPS model+menthol group was increased, while the TRPM8 knockout group was decreased (all P<0.001). Conclusion: TRPM8 can exacerbate pain symptom in IC/BPS mice, and the mechanism may be related to the induction of sensory nerve proliferation at the DRG level.
目的： 探讨瞬时受体电位M8（TRPM8）对间质性膀胱炎/膀胱疼痛综合征（IC/BPS）小鼠疼痛症状及神经元增殖的影响。 方法： 将雌性野生型C57BL/6小鼠（8~10周龄）按随机数字表法分为对照组、IC/BPS模型组和IC/BPS模型+薄荷醇组（各6只）；TRPM8基因敲除小鼠随机分为TRPM8基因敲除组和TRPM8基因敲除模型组（各6只）。IC/BPS模型组、IC/BPS模型+薄荷醇组和TRPM8基因敲除模型组小鼠皮下注射尿路斑块蛋白65-84氨基酸残基（UPK3A65-84）多肽；IC/BPS模型+薄荷醇组继续注射薄荷醇。建模成功后，通过机械敏感性评估各组疼痛阈值的差异；膀胱壁注射细胞膜红色荧光探针（Dil），10 d后采集背根神经节（DRG）组织，利用Western蛋白印迹法和实时定量反转录聚合酶链反应（qRT-PCR）分别检测各组TRPM8和生长相关蛋白43（GAP43）的蛋白质和mRNA含量的差异；免疫荧光技术检测DRG组织中TRPM8表达与GAP43或Dil的分布情况。分析TRPM8与IC/BPS小鼠疼痛症状的关系及在神经元增殖中的作用。 结果： 模型均构建成功。与对照组相比，IC/BPS模型组和IC/BPS模型+薄荷醇组小鼠的疼痛阈值均降低［分别为（8.50±1.22）、（5.50±1.05）比（11.67±2.16），均P<0.001］。与对照组相比，IC/BPS模型组和IC/BPS模型+薄荷醇组TRPM8的表达量均升高，而在TRPM8基因敲除组小鼠中TRPM8未表达［分别为（3.16±0.05）、（6.46±0.21）、0比（1.00±0.06），均P<0.001］。各组小鼠TRPM8蛋白表达量与mRNA表达趋势相同（P<0.001）。与对照组相比，IC/BPS模型组和IC/BPS模型+薄荷醇组DRG中GAP43 mRNA的表达增加，而TRPM8基因敲除模型组的表达下降（均P<0.001）。GAP43蛋白表达与mRNA表达趋势相同（P<0.001）。免疫荧光结果显示，与对照组相比，IC/BPS模型组和IC/BPS模型+薄荷醇组DRG中GAP43阳性神经元的数量增加，TRPM8基因敲除组下降（均P<0.001）。与对照组相比，IC/BPS组和IC/BPS模型+薄荷醇组DRG Dil阳性感觉神经元数量增加，而TRPM8基因敲除组下降（均P<0.001）。 结论： TRPM8可加剧IC/BPS小鼠的疼痛症状，其机制可能与诱导DRG水平的感觉神经增殖有关。.