Intermittent Restraint Stress Induces Circadian Misalignment in the Mouse Bladder, Leading to Nocturia

Abstract

Background: Intermittent stress disrupts the circadian rhythm in clock genes such as Per2 only in peripheral organs without any effect on the central nervous system. Here, the effect of restraint stress (RS) on circadian bladder function was investigated based on urination behavior and gene expression rhythms. Furthermore, PF670462 (PF), a Per2 phosphorylation enzyme inhibitor, was administered to investigate the effects on circadian bladder re-alignment after RS. Method: Two-hour RS during the light phase was applied to mice (RS mice) for 5 days. The following parameters were then examined: urination behaviors; clock gene expression rhythms and urinary sensory-related molecules; Per2 expression in the excised bladder of Per2::luc mice; in vivo Per2 expression rhythms in the bladder of Per2::luc mice. Findings: Control mice did not show altered urination behavior in the light phase, whereas RS mice exhibited a higher voiding frequency and lower bladder capacity. In the bladder mucosa, RS mice also showed abrogated or misaligned urinary sensory-related molecules and clock gene expression. The rhythmic expression of Per2 was also altered in RS mice both in excised- and in vivo bladder, compared with control mice. After PF administration, voiding frequency was reduced and bladder capacity was increased during the light phase in RS mice; the in vivo Per2 expression rhythm was also fully restored. Interpretation: RS can alter circadian gene expression in the bladder during the light phase and might cause nocturia via changes in circadian bladder function due the dysregulation of clock genes. Amending the circadian rhythm therapeutically could be applied for nocturia. Funding Statement: This work was supported financially by Suzuki Urinary Medicine Promotion Foundation and Astellas Pharma Inc. Declaration of Interests: The authors declare that they have no conflicts of interest with the contents of this article. Ethics Approval Statement: All procedures were conducted in accordance with the Guiding Principles in the Care and Use of Animals in the Field of the Physiologic Society of Japan and the policies of the Institutional Animal Care and Use Committee.