Actions of cAMP on calcium sensitization in human detrusor smooth muscle contraction

  • BJU Int. 2016 Jan;117(1):179-91. doi: 10.1111/bju.13180.
Maya Hayashi  1 ,  Shunichi Kajioka  1 ,  Momoe Itsumi  1 ,  Ryosuke Takahashi  1 ,  Nouval Shahab  2 ,  Takao Ishigami  3 ,  Masahiro Takeda  3 ,  Noriyuki Masuda  4 ,  Akito Yamaguchi  5 ,  Seiji Naito  1
Affiliations
  • 1. Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Japan.
  • 2. Department of Urology, Faculty of Medicine and Health Sciences, Syarif Hidayaullah Jakarta State Islamic University, Jakarta, Indonesia.
  • 3. Urology Research Unit, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Japan.
  • 4. Innovation and Research Portfolio Planning, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Japan.
  • 5. Division of Urology, Harasanshin Hospital, Fukuoka, Japan.
PMID: 25981809 DOI: 10.1111/bju.13180
Abstract

Objectives: To clarify the effect of cAMP on the CA(2+) -sensitized smooth muscle contraction in human detrusor, as well as the role of novel exchange protein directly activated by cAMP (Epac) in cAMP-mediated relaxation.

Materials and methods: All experimental protocols to record isometric tension force were performed using α-toxin-permeabilized human detrusor smooth muscle strips. The mechanisms of cAMP-mediated suppression of CA(2+) sensitization activated by 10 μm carbachol (CCh) and 100 μm GTP were studied using a selective rho kinase (ROK) inhibitor, Y-27632, and a selective protein kinase C (PKC) inhibitor, GF-109203X. The relaxation mechanisms were further probed using a selective protein kinase A (PKA) activator, 6-Bnz-cAMP and a selective Epac activator, 8-pCPT-2'-O-Me-cAMP.

Results: We observed that CCh-induced CA(2+) sensitization was inhibited by cAMP in a concentration-dependent manner. GF-109203X (10 μm) but not Y-27632 (10 μm) significantly enhanced the relaxation effect induced by cAMP (100 μm). 6-Bnz-cAMP (100 μm) predominantly decreased the tension force in comparison with 8-pCPT-2'-O-Me-cAMP (100 μm).

Conclusions: We showed that cAMP predominantly inhibited the ROK pathway but not the PKC pathway. The PKA-dependent pathway is dominant, while Epac plays a minor role in human detrusor smooth muscle CA(2+) sensitization.

Keywords
cAMP; calcium sensitization; human detrusor smooth muscle; permeabilization; rho kinase; α-toxin.
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