Ihara Tatsuya, Shinozaki Youichi, Shigetomi Eiji, Danjo Yosuke, Tsuchiya Sachiko, Kanda Mie, Kamiyama Manabu, Takeda Masayuki, Koizumi Schuichi, Mitsui Takahiko
Department of Urology, Toranomon Hospital Kajigaya, Kawasaki, Kanagawa 213-8587, Japan.
Visual Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
Life Sci. 2023 Nov 1;332:122072. doi: 10.1016/j.lfs.2023.122072. Epub 2023 Sep 11.
Bladder function is regulated by clock genes and dysregulation of circadian bladder function can cause nocturia. The blood concentration of palmitoylethanolamide (PEA), a fatty acid metabolite, changes with circadian rhythm. Clock gene abnormalities demonstrate the highest PEA levels during the sleep phase. PEA is a GPR55 agonist that influences urination; therefore, increased PEA during the sleep phase may cause nocturia. Herein, we investigated the function of GPR55 to evaluate the relationship between GPR55 and nocturia that evoked higher PEA during the sleep phase in patients with circadian rhythm disorders.
Male C57BL/6 mice were used. GPR55 localization was evaluated by immunofluorescence staining, qRT-PCR, and western blotting. Variations in PEA-induced intracellular Ca concentrations were measured in primary cultured mouse urothelial cells (UCs) using Ca imaging. PEA-induced NGF and PGI release in UCs was measured by ELISA. The micturition reflex pathway after PEA administration was evaluated using immunofluorescence staining.
GPR55 was predominant in the UC layer. PEA induced release of Ca from the endoplasmic reticulum into the UC cytoplasm. ELISA and immunofluorescence staining revealed that NGF and PGI were released from bladder UCs, stimulated the pontine micturition center in mice, and induced nocturia.
The loss of regular circadian metabolizing rhythm in fatty acids causes higher blood PEA levels during the sleep phase. Binding of PEA to GPR55 in UC may activate the downstream processes of the micturition reflex, leading to nocturia. These findings suggest a new mechanism for nocturia and its potential as a therapeutic target.
膀胱功能受生物钟基因调控，昼夜膀胱功能失调可导致夜尿症。脂肪酸代谢产物棕榈酰乙醇胺（PEA）的血药浓度随昼夜节律变化。生物钟基因异常显示睡眠期PEA水平最高。PEA是一种影响排尿的GPR55激动剂；因此，睡眠期PEA升高可能导致夜尿症。在此，我们研究了GPR55的功能，以评估GPR55与昼夜节律紊乱患者睡眠期引起PEA升高的夜尿症之间的关系。
使用雄性C57BL/6小鼠。通过免疫荧光染色、qRT-PCR和蛋白质印迹法评估GPR55的定位。使用钙成像技术在原代培养的小鼠尿路上皮细胞（UCs）中测量PEA诱导的细胞内钙浓度变化。通过ELISA测量PEA诱导的UCs中NGF和PGI的释放。使用免疫荧光染色评估PEA给药后的排尿反射途径。
GPR55在UC层中占主导地位。PEA诱导内质网中的钙释放到UC细胞质中。ELISA和免疫荧光染色显示，NGF和PGI从膀胱UCs中释放出来，刺激小鼠脑桥排尿中枢，并导致夜尿症。
脂肪酸正常昼夜代谢节律的丧失导致睡眠期血PEA水平升高。PEA与UC中GPR55的结合可能激活排尿反射的下游过程，导致夜尿症。这些发现提示了夜尿症的一种新机制及其作为治疗靶点的潜力。
