492 CAVEOLAE-MEDIATED REGULATION OF PURINERGIC SIGNALING IN THE BLADDER SUPPRESSES SPONTANEOUS ACTIVITY

Abstract

You have accessJournal of UrologyBladder and Urethra: Anatomy, Physiology and Pharmacology II1 Apr 2012492 CAVEOLAE-MEDIATED REGULATION OF PURINERGIC SIGNALING IN THE BLADDER SUPPRESSES SPONTANEOUS ACTIVITY Vivian Cristofaro, Subbarao Yalla, and Maryrose Sullivan Vivian CristofaroVivian Cristofaro Boston, MA More articles by this author , Subbarao YallaSubbarao Yalla Boston, MA More articles by this author , and Maryrose SullivanMaryrose Sullivan Boston, MA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.562AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Bladder smooth muscle (BSM) caveolae, membrane domains that modulate responses to physiologic stimuli, are reduced in animal models of DO. These animals exhibit increased bladder spontaneous activity (SA) and altered purinergic signaling. In this study, we investigated whether caveolae-mediated regulation of the purinergic system plays a role in maintaining the level of SA in the bladder. METHODS Rat bladder strips without mucosa were mounted in organ bath. SA and responses induced by αβmeATP were measured before and after caveolae depletion (achieved by methyl-β-cyclodextrin, mβCD). Changes in SA were also determined after P2X receptor inhibition (NF449, NF279, PPADS, or after αβmeATP-desensitization) and in the presence of ivermectin (IVC, a P2X4 positive modulator) or BDBD (P2X4 antagonist), or after the connexin (Cx) hemichannel blocker, carbenoxolone (CBX). Differences among these treatments in levels of ATP released either spontaneously or upon stimulation (induced by KCl in BSM tissue and hypotonic Krebs exposure in BSM cells) were determined by luciferase assay. P2X4 receptor expression in BSM tissue and the interaction of caveolin proteins with P2X4 receptor and Cx43 were determined by western blot and co-immunoprecipitation. RESULTS Depletion of caveolae inhibited P2X-mediated contractile responses and augmented SA in BSM tissue, and increased basal ATP release from BSM cells. SA and ATP levels in BSM tissue were also increased by inhibiting P2X receptors and by exposure to IVC. BDBD prevented the augmentation in SA caused by P2X receptor inhibition and the KCl-induced ATP release from BSM tissue. Similarly, CBX attenuated the increase in ATP induced by mβCD or by hypotonic Krebs in BSM cells, and prevented the KCl-induced ATP release from BSM tissue. P2X4 and Cx43 were expressed in BSM tissue and co-precipitated with caveolin proteins. CONCLUSIONS The impaired regulation of purinergic signaling and the ATP-induced increase in SA after mβCD is consistent with enhanced SA in animal models of DO in which caveolae are reduced, suggesting a role for caveolae in restraining SA. Loss of caveolae exposed an excitatory component, potentially mediated by P2X4 receptor activation, which was prevented by CBX, suggesting that SA levels are modulated by the effects of endogenous ATP released from BSM cells through Cx hemichannels. The molecular interaction of Cx43 with caveolin proteins supports the concept that hemichannel-mediated ATP release is suppressed by caveolae. Therefore, loss of BSM caveolae may cause dysregulation of this mechanism and lead to DO. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e201 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Vivian Cristofaro Boston, MA More articles by this author Subbarao Yalla Boston, MA More articles by this author Maryrose Sullivan Boston, MA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...