MP54-06 PANNEXIN 1 CHANNELS INVOLVEMENT IN MECHANISM OF STRESS-INDUCED PELVIC PAIN AND URINARY SYMPTOMS IN MICE

Abstract

INTRODUCTION AND OBJECTIVE: Pannexin 1 (Panx1) channels are key components of the urothelial mechanosensory and mechanotransduction system. They are mechanosensitive and provide a direct conduit for urothelial ATP release in response to bladder distension. Little is known of the role of Panx1 channels in bladder pathology. The goal of this study is to evaluate if Panx1 channels are involved in emergence of pelvic pain and urinary symptoms in an animal model of stress. METHODS: Wildtype (WT) and Panx1-null mice, and the stress model of 96 hours of continuous illumination (CI) were used in this study. Pelvic tactile sensitivity and bladder function were evaluated at baseline (pre-CI) and the day after the 96 hours of CI using the Von Frey test and the void stain on paper (VSOP) method, respectively. ATP levels in spontaneously voided urine were quantified pre- and post-CI using the luciferin-luciferase assay. Bladders were harvested from CI stressed and age-matched controls (housed under conventional 12 hour/day illumination), and urothelial Panx1 mRNA levels were quantified by real time PCR. Cystometric data from an additional group of WT mice was obtained pre-CI and then post-CI with and without intravesical treatment with Panx1 channel blocker mefloquine (300nM). Data is expressed as mean±SEM and statistical difference determined by paired or unpaired Student’s t-test. RESULTS: In WT mice, pelvic tactile threshold decreased 18-fold (pre-CI: 0.22 ± 0.06 vs post-CI: 0.012 ± 0.007; N = 4 p<0.01) and voiding frequency increased 2-fold (pre-CI: 0.56 ± 0.04 vs post-CI: 1.11 ± 0.12; N = 4 p<0.01) after CI. This was accompanied by a 2.5-fold increase in Panx1 expression in the bladder urothelium when compared to non-stressed WT mice (2.53 ± 0.29 stressed/non-stressed controls; N=4; p<0.001), and a 2-fold increase in urothelial ATP release compared to baseline levels (1.8 ± 0.24 post-CI/pre-CI; N = 4; p=0.007). Notably, emergence of pelvic pain and voiding frequency was abrogated in Panx1-null mice submitted to CI stress, and urothelial ATP release was not different from control pre-CI levels. Urodynamic assessment of WT mice after CI indicated marked bladder hyperactivity that was normalized by intravesical treatment with Panx1 channel blocker mefloquine. CONCLUSIONS: Panx1 channels play a significant role in stress-induced pelvic pain and urinary frequency, likely by amplifying urothelial ATP release that can ultimately change the bladder sensory and motor responses, and cause bladder sensitization. Source of Funding: None