PD20-05 HERPES SIMPLEX VIRUS (HSV) VECTOR-MEDIATED GENE DELIVERY OF PROTEIN PHOSPHATASE 1α REDUCES BLADDER OVERACTIVITY AND

Abstract

INTRODUCTION AND OBJECTIVES: Increased afferent excitability has been proposed as an important pathophysiological basis of overactive bladder (OAB) and hypersensitive bladder disorders such as interstitial cystitis/bladder pain syndrome (IC/BPS). Previous studies reported that transient receptor potential vanilloid-1 (TRPV1) receptors greatly contribute to afferent sensitization. We recently found Protein Phosphatase 1a (PP1a) as a modulator of TRPV1 receptor activity using an HSV vector cDNA library screen method to identify genes that antagonize TRPV1 activation. HSV vector-mediated PP1a expression significantly reduced capsaicin-induced thermal hyperalgesia. Therefore, we investigated the effect of HSV vectors-mediated gene delivery of PP1a on bladder overactivity and pain-related behavior in rats. METHODS: Replication-deficient HSV vectors encoding PP1a or green fluorescent protein (GFP) as control were injected into the bladder wall of adult female Sprague-Dawley rats. Cystometry (CMG) under urethane anesthesia was performed 1 week after viral injection to evaluate bladder overactivity induced by resiniferatoxin (RTX, a TRPV1 agonist). RTX-induced nociceptive behavior such as licking (lower abdominal licking) and freezing (motionless headturning) was observed 2 weeks after viral innoculation. GFP expression in the L6/S1 DRG and the bladder as well as c-Fos positive cells in the L6 spinal cord dorsal horn were evaluated. The expression of p-ERK, p-Inositol trisphosphate receptor (p-IP3R), and p-TRPV1 in the bladder was estimated by Western blot. RESULTS: GFP expression was seen in L6/S1 DRG as well as in the bladder. In CMG, the PP1a group showed a significantly (p1⁄40.03) smaller reduction (46 1%) in intercontraction intervals after RTX infusion than the GFP group (64 2%). The number of RTX-induced freezing behavior, which is correlated with bladder pain sensation, was significantly (p<0.001) decreased in the PP1a vs. GFP groups. The number of c-Fos positive cells in the L6 spinal dorsal horn was significantly (p<0.01) smaller in the PP1a vs. the GFP group (33 4 vs. 59 6 cells per section). Western blot revealed that p-ERK, p-IP3R, and p-TRPV1 was less expressed in the PP1a vs. the GFP group (p1⁄40.07, 0.01, and 0.04, respectively) CONCLUSIONS: These results indicate that HSV vectorsmediated gene delivery of PP1a can suppress TRPV1-mediated bladder overactivityandpainbehavior, possibly due todecreasedphosphorylation of TRPV1 channels. Thus, PP1a gene thetapy could be a novel treatment of OAB and/or hypersensitive bladder disorders such as IC/BPS.