Compound 48/80 increases bladder wall mechanical compliance via activation of MMP-2

Abstract

<b>Abstract ID 26334</b> <b>Poster Board 32</b> <b>Background:</b> Alteration in wall stiffness and bladder compliance can disrupt normal bladder function and lead to lower urinary tract symptoms (LUTS). Urinary bladder fibrosis due to inflammation is implicated in many clinical cases of LUTS. Mast cell activation represents a key target to understand the fibrotic inflammatory pathways within the bladder wall. Our lab has previously shown that mast cell activation using Compound 48/80 increases mechanical compliance and detrusor contractility, and prostaglandins and matrix metalloproteases (MMPs) released from mast cells can directly alter the mechanical properties of the bladder wall. Blocking the release of prostaglandins blocks the increase in both mechanical compliance and detrusor contractility; however, the specific MMPs responsible for driving changes in compliance are unknown. Thus, in this study we pharmacologically investigated the role of specific MMPs in driving the increase in compliance upon mast cell activation. We hypothesized that MMP-2 is present in the urinary bladder wall and is responsible for the increase in mechanical compliance caused by mast cell degranulation. <b>Methods:</b> Whole mouse bladders from C57Bl/6 (wild-type) mice were dissected and mounted in the custom-designed pentaplanar reflected image macroscopy (PRIM) system for simultaneous measurement of transient pressure events, intravesical pressure, bladder volume, wall stress, and wall stretch during <i>ex vivo</i> bladder filling. Wall compliance was derived as a measure of the stress <i>versus</i> stretch relationship using the pressure-volume curves and associated wall geometry gathered from imaging data. Bladders were exposed to Compound 48/80 (10 μg/ml) in the presence of vehicle, the broad-spectrum MMP inhibitor marimastat (10 μM), or the MMP2 inhibitor ARP-100 (10μM) during <i>ex vivo</i> filling. MMP-2 protein expression in whole urinary bladder protein isolates was also determined using western blot analysis. <b>Results:</b> Western blot analysis showed that MMP-2 is present in the bladder wall in both detrusor and urothelium layers. Both marimastat and ARP-100 completely abolished the increase in compliance caused by Compound 48/80. However, neither altered the increase in amplitude of transient pressure events. <b>Conclusions:</b> These findings suggest that the effects of mast cell activation are dual in nature: mast cell activation causes a release of prostaglandins that directly alter detrusor contractility and also increase wall compliance by activating MMP-2. Increases in excitability and profound bladder wall remodeling also occur in minutes after degranulation, suggesting these mechanisms are initiated rapidly after inflammatory insult. Support/Funding Information: R01DK119615 (NRT) and P20DK127554 (SR and NRT).