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Rho Kinase and Protein Kinase C Pathways are Responsible for Enhanced Carbachol Contraction in Permeabilized Detrusor in a Rat Model of Cystitis
Author(s) -
Denizalti Merve,
DurluKandilci Nezahat Tugba,
Simsek Gul,
Bozkurt Turgut Emrah,
SahinErdemli Inci
Publication year - 2018
Publication title -
basic and clinical pharmacology and toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.805
H-Index - 90
eISSN - 1742-7843
pISSN - 1742-7835
DOI - 10.1111/bcpt.13045
Subject(s) - carbachol , contraction (grammar) , chemistry , endocrinology , ryanodine receptor , detrusor muscle , interstitial cystitis , contractility , medicine , endoplasmic reticulum , protein kinase c , thapsigargin , protein kinase a , channel blocker , muscle contraction , rho associated protein kinase , rho kinase inhibitor , kinase , calcium , urinary bladder , receptor , biochemistry , urinary system
Abstract Interstitial cystitis is a syndrome characterized by detrusor overactivity and chronic inflammation of the bladder. The mechanisms responsible for the altered smooth muscle contractility remain poorly understood. The aim of the study was to investigate the role of intracellular signalling pathways in carbachol‐induced detrusor contraction in a rat model of interstitial cystitis. Cyclophosphamide (150 mg/kg, dissolved in saline) was injected to rats (Sprague–Dawley, female, 200–250 g) intraperitoneally once a day on days 1, 4 and 7 to induce interstitial cystitis. Control groups were injected with saline (0.9% NaCl). Detrusor smooth muscle strips were mounted in 1‐ml organ baths containing HEPES ‐buffered modified Krebs’ solution and permeabilized with 40 μM β‐escin for 30 min. Carbachol‐induced contractions were significantly increased from 21.2 ± 1.6% (saline‐treated) to 44 ± 4.4% in cyclophosphamide‐treated group. The Rho kinase inhibitor Y‐27632 (8.8 ± 2%) and the protein kinase C inhibitor GF ‐109203X (11.7 ± 2.8%) inhibited the increased contractile response (44 ± 4.4%) in rats with cystitis. The increased carbachol‐induced contraction (44 ± 4.4%) was also significantly inhibited by the sarcoplasmic reticulum ryanodine channel blocker ryanodine (25.8 ± 3.2%) and the sarcoplasmic reticulum IP 3 receptor blocker heparin (17.2 ± 2.2%) in cystitis. RhoA protein levels in the bladder of cyclophosphamide‐treated rats were significantly increased while pan‐protein kinase C (α, β and γ isoforms) protein expression was unaltered between experimental groups. Carbachol‐induced calcium sensitization at constant and clamped calcium ( pC a 6) was also increased in cystitis (from 15.8 ± 2.2% to 24.7 ± 2.8%). This increased response (24.7 ± 2.8%) was significantly inhibited by both Y‐27632 (7.9 ± 0.7%) and GF ‐109203X (4.4 ± 1.5%). We conclude that interstitial cystitis is characterized by an enhanced carbachol contractile response as well as by calcium sensitization of the detrusor smooth muscle. Activation of Rho kinase and protein kinase C pathways may be the molecular culprits responsible for the augmented muscarinic response observed in cystitis.