Effects of pharmacological neurotrophin receptor inhibition on bladder function in female mice with cyclophosphamide-induced cystitis

Abstract

Interstitial cystitis/bladder pain syndrome is a chronic inflammatory pelvic pain syndrome of unknown etiology characterized by a number of lower urinary tract symptoms, including increased urinary urgency and frequency, bladder discomfort, decreased bladder capacity, and pelvic pain. While its etiology remains unknown, a large body of evidence suggests a role for changes in neurotrophin signaling, particularly that of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Here, we evaluated the effects of pharmacological inhibition of the NGF receptor TrkA, BDNF receptor TrkB, and pan-neurotrophin receptor p75^NTR on bladder function in acute (4-hour) and chronic (8-day) mouse models of cyclophosphamide (CYP)-induced cystitis. TrkA inhibition via ARRY-954 significantly increased intermicturition interval and bladder capacity in control and acute and chronic CYP-treatment conditions. TrkB inhibition via ANA-12 significantly increased intermicturition interval and bladder capacity in acute, but not chronic, CYP-treatment conditions. Interestingly, intermicturition interval and bladder capacity significantly increased following p75^NTR inhibition via LM11A-31 in the acute CYP-treatment condition, but decreased in the chronic condition, potentially due to compensatory changes in neurotrophin signaling or increased urothelial barrier dysfunction in the chronic condition. Our findings demonstrate that these receptors represent additional potent therapeutic targets in mice with cystitis and may be useful in the treatment of interstitial cystitis and other inflammatory disorders of the bladder.

Keywords: TrkA; TrkB; brain-derived neurotrophic factor (BDNF); cyclophosphamide; interstitial cystitis (IC)/bladder pain syndrome (BPS); nerve growth factor; p75; urinary bladder.

FIGURE 1

Bladder function was assessed via conscious, open-outlet cystometry. (A) Tubing is surgically implanted in the bladder and run subcutaneously to a port at the nape of the neck, allowing direct infusion into the bladder. (B) During cystometry, the mouse is placed in a wire-bottomed recording chamber. Saline is infused into the bladder at a constant rate of 25 μL/minute, allowing the measurement of various urodynamic parameters: bladder pressure (threshold, maximum, minimum, and average), infused volume (IV; the volume of saline infused into the bladder since the last void), and intermicturition interval (IMI; time between voids). Original illustrations by Harrison Hsiang.

FIGURE 2

Increased voiding frequency following acute (4-hour) and chronic (8-day) CYP-treatment. (A) Representative traces of bladder pressure (mm Hg) over time (seconds) for control, acute and chronic CYP-treatment during constant intravesical infusion of saline. Bladder pressure increases with filling, spiking when the bladder contracts during micturition. Intermicturition interval is visibly decreased (increased frequency) in acute and chronic CYP-treatment conditions. (B) Both acute and chronic CYP-treatment increased voiding frequency. Intermicturition interval and infused volume were significantly reduced in acute (p = 0.0000014) and chronic (p = 0.0000098) CYP-treatment conditions. Circles mark the individual data points for each condition. N = 6 for all.

FIGURE 3

Decreased voiding frequency following intravesical treatment with AR. Intermicturition interval was statistically increased following intravesical administration of AR in control (1.18-fold, p = 0.01622, N = 6) and acute (4-hour; 1.56-fold, p = 0.001935, N = 5) and chronic (8-day; 1.68-fold, p = 0.02549, N = 6) CYP-treated mice. Slope graphs indicate the change of individual mice before and after treatment. Red dotted lines indicate the change in mean values for each condition before and after treatment.

FIGURE 4

No effect on bladder function following intravesical treatment with 20% Captisol (p > 0.05, N = 6). Slope graphs indicate the change of individual mice before and after treatment. Red dotted lines indicate the change in mean values for each condition before and after treatment.

FIGURE 5

Decreased voiding frequency following intravesical treatment with LM in acute CYP-treatment conditions. Intermicturition interval was statistically increased following intravesical administration of LM in acute (4-hour) CYP-treated mice (1.83-fold, p = 0.001702, N = 7). Intermicturition interval was statistically decreased following intravesical administration of LM in chronic (8-day) CYP-treated mice (0.63-fold, p = 0.007845, N = 5). There was no statistical difference before and after LM treatment in the control condition (p > 0.05; N = 6). Slope graphs indicate the change of individual mice before and after treatment. Red dotted lines indicate the change in mean values for each condition before and after treatment.

FIGURE 6

Decreased voiding frequency following intravesical treatment with ANA. Intermicturition interval was statistically increased following intravesical administration of ANA in acute (4-hour) CYP-treated mice (1.6-fold, p = 0.001114, N = 8). There was no statistical difference following treatment in the control and chronic (8-day) CYP-treatment conditions (p > 0.05, N = 8, 7). Slope graphs indicate the change of individual mice before and after treatment. Red dotted lines indicate the change in mean values for each condition before and after treatment.