Circadian coordination of ATP release in the urothelium via connexin43 hemichannels

Atsushi Sengiku,Nobuyuki Nishikawa,Shigeki Shimba,Takeshi Sano,Hiromitsu Negoro,Masakatsu Ueda,Louis S Liou,Jin Kono,Masao Doi,Kojiro Tsujihana,Hitoshi Okamura,Akihiro Kanematsu,Sumihiro Kunisue,Osamu Ogawa

doi:10.1038/s41598-018-20379-0

Atsushi Sengiku, Nobuyuki Nishikawa + Show 12 more

Open Access

https://doi.org/10.1038/s41598-018-20379-0

Copy DOI

Abstract

Day-night changes in the storage capacity of the urinary bladder are indispensable for sound sleep. Connexin 43 (Cx43), a major gap junction protein, forms hemichannels as a pathway of ATP in other cell types, and the urinary bladder utilizes ATP as a mechanotransduction signals to modulate its capacity. Here, we demonstrate that the circadian clock of the urothelium regulates diurnal ATP release through Cx43 hemichannels. Cx43 was expressed in human and mouse urothelium, and clock genes oscillated in the mouse urothelium accompanied by daily cycles in the expression of Cx43 and extracellular ATP release into the bladder lumen. Equivalent chronological changes in Cx43 and ATP were observed in immortalized human urothelial cells, but these diurnal changes were lost in both arrhythmic Bmal1-knockout mice and in BMAL1-knockdown urothelial cells. ATP release was increased by Cx43 overexpression and was decreased in Cx43 knockdown or in the presence of a selective Cx43 hemichannel blocker, which indicated that Cx43 hemichannels are considered part of the components regulating ATP release in the urothelium. Thus, a functional circadian rhythm exists in the urothelium, and coordinates Cx43 expression and function as hemichannels that provide a direct pathway of ATP release for mechanotransduction and signalling in the urothelium.

Highlights

Humans have the ability to increase bladder capacity and decrease urine production at night-time compared with daytime to avoid disturbances of sleep by micturition[1,2,3]
ATP released to the basal side of the urothelium activates purinergic receptors such as P2X2 and P2X3 expressed by afferent nerves in the suburothelium[21,22,23,24,25], whereas ATP released to the luminal side activates various P2X and P2Y receptors on the urothelium in an autocrine/paracrine manner to form a positive feedback loop of ATP secretion[26,27]
To demonstrate that the connexin 43 (Cx43) expression and ATP release are under the control of the circadian clock, we investigated the influence of BMAL1-knockdown on the circadian rhythm in urothelial cells

Summary

Introduction

Humans have the ability to increase bladder capacity and decrease urine production at night-time compared with daytime to avoid disturbances of sleep by micturition[1,2,3]. Mice are nocturnal (i.e. active primarily during the night), and the phases of their sleep-wake cycles are inverted to those of humans Their bladder capacity is increased during the sleep/light phase and decreased during the active/dark phase. ATP released to the basal side of the urothelium activates purinergic receptors such as P2X2 and P2X3 expressed by afferent nerves in the suburothelium[21,22,23,24,25], whereas ATP released to the luminal side activates various P2X and P2Y receptors on the urothelium in an autocrine/paracrine manner to form a positive feedback loop of ATP secretion[26,27] These findings suggest that ATP modulates bladder capacity by transmitting mechanotransduction signals

Methods

Results

Conclusion