Contractile responses in intact and mucosa-denuded human ureter—a comparison with urinary bladder detrusor preparations

In vitro effects of β3-adrenoceptor agonist mirabegron on the human ureter

INTRODUCTION

This study aimed to investigate the effect of mirabegron, a β3-adrenoceptor agonist with widespread clinical use for treating overactive bladder disease, on isolated healthy human ureter strips.

MATERIALS AND METHODS

This was a prospective study employing a series of in vitro organ bath experiments using ureteral tissues of kidney grafts from 10 healthy donors. The ureteral strips were subjected to cumulative mirabegron concentrations (10-9-10-4.5 M). Effects on frequency or amplitude of spontaneous, 10 mM KCl- or EFS-induced contractions were evaluated.

RESULTS

Mirabegron decreased the frequency of spontaneous ureteric contraction in a concentration-dependent manner. Statistically significant decrease in the frequency of spontaneous contraction was observed at 10-8-10-4.5 M. In 10 mM KCl medium, statistically significant change in frequency was observed at 10-9-10-4.5 M. Statistically significant decrease in the amplitudes of spontaneous contraction was observed at 10-7-10-4.5 M. In a 10 mM KCl medium, statistically significant change in amplitudes was observed at 10-8-10-4.5 M.

CONCLUSIONS

Mirabegron reduced the amplitude and frequency of human ureter activity in in vitro organ bath studies. This effect was achieved in a dose-dependent manner on isolated tissue strips. Although monotherapy with mirabegron remains uncertain, this study has the potential to elucidate the mechanism underlying the effectiveness of mirabegron, particularly in combination therapy for ureteral stones.

Activation of TRPM8 channel inhibits contraction of the isolated human ureter

AIMS

The transient receptor potential melastin-8 (TRPM8) channel is a "cooling" receptor expressed in primary sensory neurons and can be activated by compounds like menthol or icilin. TRPM8 is involved in the regulation of urinary bladder sensory function and contraction, but the role of TRPM8 in the ureter, particularly in the human ureter, is poorly understood. The aim of this study is to examine the effects of TRPM8 activation on human ureter contraction.

METHODS

Human ureters were acquired from 20 patients undergoing radical nephrectomy. Contractions of ureter strips were recorded by an isometric transducer in the organ bath. Ureteral TRPM8 expression in the human ureter was examined by immunofluorescence and western blot.

RESULTS

The two TRPM8 agonists menthol and icilin both reduced the frequency of spontaneous, electrical field stimulation, or neurokinin A-evoked ureteral contractions in a dose-dependent manner. The inhibitory effects were decreased by 10-fold in mucosa-denuded strips. The inhibitory effects of TRPM8 agonists were mimicked by calcitonin gene-related peptide (CGRP), and were blocked by KRP2579 (a TRPM8 antagonist), tetrodotoxin (a sodium channel blocker), olcegepant (BIBN, a CGRP receptor antagonist), SQ22536 (an adenylate cyclase antagonist), or H89 (a nonspecific cAMP-dependent protein kinase A inhibitor). TRPM8 was coexpressed with CGRP on the nerves located in the suburothelial and intermuscular regions and was not expressed in the urothelium.

CONCLUSIONS

The TRPM8 channel expressed on sensory nerve terminals of the human ureter is involved in the inhibitory sensory neurotransmission and modulate ureter contraction via the CGRP-adenylyl cyclase-protein kinase A pathway. TRPM8 may be involved in stone-induced changes in ureter contraction or pain.

TRPM3 channel activation inhibits contraction of the isolated human ureter via CGRP released from sensory nerves

AIMS

Sensory nerve activation modulates ureteral contractility by releasing neuropeptides including CGRP and neurokinin A (NKA). TRPM3 is a recently discovered thermosensitive channel expressed in nociceptive sensory neurons, and plays a key role in heat nociception and chronic pain. The aim of this study is to examine the role of TRPM3 activation in human ureter motility.

MAIN METHOD

Human proximal ureters were obtained from fourteen patients undergoing nephrectomy. Spontaneous or NKA-evoked contractions of longitudinal ureter strips were recorded in an organ bath. Ureteral TRPM3 expression was examined by immunofluorescence.

KEY FINDINGS

Spontaneous contractions were observed in 60% of examined strips. TRPM3 activation using pregnenolone sulphate (PS) or CIM0216 (specific TRPM3 agonists) dose-dependently reduced the frequency of spontaneous and NKA-evoked contractions, with IC50s of 241.7 μM and 4.4 μM, respectively. The inhibitory actions of TRPM3 agonists were mimicked by CGRP (10 to 100 nM) or a cAMP analogue (8-Br-cAMP; 1 mM). The inhibitory actions of TRPM3 agonists (300 μM PS or 30 μM CIM0216) were blocked by pretreatment with primidone (TRPM3 antagonist; 30 μM), tetrodotoxin (sodium channel blocker; 1 μM), olcegepant (CGRP receptor antagonist; 10 μM), or H89 (non-specific PKA inhibitor; 30 μM). TRPM3 was co-expressed with CGRP in nerves in the sub-urothelial and intermuscular regions of the ureter.

SIGNIFICANCE

TRPM3 channels expressed on sensory terminals of the human ureter involve in inhibitory sensory neurotransmission and modulate ureter motility via the CGRP-cAMP-PKA signal pathway. Targeting TRPM3 may be a pharmacological strategy for promoting the ureter stone passage.