39 UPREGULATION OF P2X PURINERGIC RECEPTORS IN BLADDER OXIDATIVE STRESS AUGMENTS SMOOTH MUSCLE CONTRACTIONS

Abstract

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Basic Research (1)1 Apr 201339 UPREGULATION OF P2X PURINERGIC RECEPTORS IN BLADDER OXIDATIVE STRESS AUGMENTS SMOOTH MUSCLE CONTRACTIONS Qi Zhang, Mike Siroky, and Kazem Azadzoi Qi ZhangQi Zhang Boston, MA More articles by this author , Mike SirokyMike Siroky Boston, MA More articles by this author , and Kazem AzadzoiKazem Azadzoi Boston, MA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.1414AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Neural regulation of bladder contraction involves both cholinergic and nonadrenergic, noncholinergic (NANC) mechanisms. Nerve stimulated bladder contractions appear to involve acetylcholine and ATP co-released from parasympathetic nerve terminals. Our goal was to examine P2X purinergic receptors expression and their role in increased smooth muscle contractions after bladder exposure to oxidative stress conditions. METHODS Confluent cultured human bladder smooth muscle cells (BSMC) were incubated under normoxia (21% oxygen, 5 dishes) and continuous hypoxia (2% oxygen, 5 dishes) conditions for 48 hours using a computerized cell oxycycler system. To study oxidative stress, another five dishes of cells were incubated under cyclical hypoxia/reoxygenation using 2% oxygen for 30 minutes followed by reoxygenation with 21% oxygen for one hour; cycling in this manner for 48 hours. Bladder oxidative stress was produced in rabbits by inducing arterial atherosclerosis and chronic bladder ischemia. Human BSMC samples and tissues from eight weeks ischemic rabbit bladders (n=8) and age-matched controls (n=8) were processed for ELISA of oxidative stress markers, western blotting of P2X purinergic receptors and measurement of contractile responses to electrical field stimulation (EFS) at 10 volts and varying frequencies in the organ bath. RESULTS P2X1 and P2X2 purinergic receptors were expressed in human BSMC while P2X1, P2X2, P2X3, P2X4, P2X5 and P2X7 were found in the rabbit bladder tissues. Continuous exposure of human BSMC to hypoxia downregulated both P2X1 and P2X2 expression. Oxidative stress significantly decreased P2X1 and increased P2X2 expression in human BSMC. Accumulation of oxidative radicals in the rabbit ischemic bladders were associated with upregulation of P2X1, P2X2, P2X3, P2X4, P2X5 and P2X7 and a significant increase in bladder smooth muscle contractions to EFS. Treatment with PPADS, a non-selective P2X receptor antagonist, normalized contractions of oxidatively stressed rabbit bladder tissues to low frequency stimulation (0.5 Hz, 1 Hz, 2 Hz and 4 Hz) while having no significant effect on contractions to high frequencies (8 Hz, 16 Hz and 32 Hz). CONCLUSIONS Upregulation of P2X purinoceptors in both human BSMC and rabbit ischemic bladder were associated with accumulation of oxidative free radicals. Upregulation of P2X receptors in rabbit bladder augmented smooth muscle contractions. While P2X receptors mediated contractions to low frequency EFS, co-release of non-purinergic transmitters appeared to dominate bladder contractions at high frequency EFS. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e15-e16 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Qi Zhang Boston, MA More articles by this author Mike Siroky Boston, MA More articles by this author Kazem Azadzoi Boston, MA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...