TRPV1 and mast cell involvement in repeated variate stress-induced urinary bladder dysfunction in adult female mice

Abstract

The etiology of interstitial cystitis/bladder pain syndrome (IC/BPS) is unknown but likely multifactorial. IC/BPS symptoms can be exacerbated by psychological stress, but underlying mechanisms remain to be defined. Transient receptor potential vanilloid 1 (TRPV1) channels, expressed on nerve fibers, have been implicated in bladder dysfunction and colonic hypersensitivity with stress in rodents. Histamine/H1R activation of TRPV1⁺ nerves increases bladder afferent fiber sensitivity to distension. TRPV1 channels are also expressed on mast cells, previously implicated in contributing to IC/BPS etiology and symptoms. We have examined the contribution of TRPV1 and mast cells to bladder dysfunction after repeated variate stress (RVS). RVS increased (P ≤ 0.05) serum and fecal corticosterone expression and induced anxiety-like behavior in wild-type (WT) mice. Intravesical instillation of the selective TRPV1 antagonist capsazepine (CPZ) rescued RVS-induced bladder dysfunction in WT mice. Trpv1 knockout (KO) mice did not increase voiding frequency with RVS and did not exhibit increased serum corticosterone expression despite exhibiting anxiety-like behavior. Mast cell-deficient mice (B6.Cg-Kit^w-sh) failed to demonstrate RVS-induced increased voiding frequency or serum corticosterone expression, whereas control (no stress) mast cell-deficient mice had similar functional bladder capacity to WT mice. TRPV1 protein expression was significantly increased in the rostral lumbar (L1-L2) spinal cord and dorsal root ganglia (DRG) in WT mice exposed to RVS, but no changes were observed in lumbosacral (L6-S1) spinal segments or DRG. These studies demonstrated TRPV1 and mast cell involvement in RVS-induced increased voiding frequency and suggest that TRPV1 and mast cells may be useful targets to mitigate stress-induced urinary bladder dysfunction.NEW & NOTEWORTHY Using pharmacological tools and transgenic mice in a repeated variate stress (RVS) model in female mice, we demonstrate that transient receptor potential vanilloid 1 (TRPV1) and mast cells contribute to the increased voiding frequency observed following RVS. TRPV1 and mast cells should continue to be considered as targets to improve bladder function in stress-induced bladder dysfunction.

Keywords: corticosterone; cystometry; dorsal root ganglia; histamine; open-field test.

Graphical abstract

Figure 1.

Corticosterone expression is increased in serum and fecal pellets from wild-type (WT), transient receptor potential vanilloid 1 (Trpv1) knockout (KO), and mast cell-deficient (B6.Cg-Kit^w-sh) mice exposed to repeated variate stress (RVS). A: WT mice exposed to RVS exhibited significantly (P ≤ 0.05) greater serum corticosterone compared to WT control mice. No changes in baseline serum corticosterone expression were observed among any mouse strain evaluated. RVS-induced serum corticosterone expression was significantly (P ≤ 0.01) greater in WT mice compared to Trpv1 KO or mast cell-deficient (B6.Cg-Kit^w-sh) mice. B: WT RVS mice exhibited significantly (P ≤ 0.05) greater fecal corticosterone expression than WT control mice (no RVS). Mast cell-deficient (B6.Cg-Kit^w-sh) mice exhibited significantly (P ≤ 0.05) increased fecal corticosterone expression compared to mast cell-deficient (B6.Cg-Kit^w-sh) control mice (no RVS). Trpv1 KO control mice (no RVS) exhibited significantly greater (P ≤ 0.05) baseline fecal corticosterone compared to WT control mice (no RVS). Trpv1 KO mice exposed to RVS exhibited significantly (P ≤ 0.05) greater fecal corticosterone expression compared to WT mice exposed to RVS (WT RVS). Data were analyzed using one-way ANOVA. *P ≤ 0.05; ***P ≤ 0.001. n = 13–14 for WT mice, n = 5–10 for Trpv1 KO mice, and n = 4–8 for mast cell-deficient (B6.Cg-Kit^w-sh) mice.

Figure 2.

The transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine (CPZ) increased the intermicturition interval (IMI; A) and increased the infused volume (IV; B) (functional bladder capacity) in mice exposed to repeated variate stress (RVS). A: summary bar graph of IMI of wild-type (WT) control (no RVS) mice and mice exposed to RVS before (pre) and after (post) CPZ treatment. WT control (no RVS) mice exhibited significantly (*P ≤ 0.02) greater (1.56-fold) IMI compared to mice exposed to RVS pre-CPZ. No change in IMI was observed in WT control (no RVS) mice before or after CPZ treatment. Mice exposed to RVS exhibited a significant (*P ≤ 0.03) increase in IMI (1.53-fold) after CPZ treatment. B: summary bar graph of IV (functional bladder capacity) of WT control (no RVS) mice and mice exposed to RVS before (pre) and after (post) CPZ treatment. WT control (no RVS) mice exhibited significantly (*P ≤ 0.02) greater (1.56-fold) IV compared to mice exposed to RVS. No change in IV was observed in WT control (no RVS) mice before or after CPZ treatment. Mice exposed to RVS exhibited a significant (*P ≤ 0.03) increase in IV (1.53-fold) after CPZ treatment. Data were analyzed using paired t tests. n = 5 for all groups.

Figure 3.

Transient receptor potential vanilloid 1 (Trpv1) knockout (KO) mice do not exhibit changes in intermicturition interval (IMI) and infused volume (IV), whereas B6.Cg-Kit^w-sh (mast cell-deficient) mice exhibited increased IMI and IV with repeated variate stress (RVS) exposure. A and B: summary bar graph of IMI (A) and IV (B) of wild-type (WT) control mice and Trpv1 KO mice exposed to RVS. WT mice exhibited a significant (*P ≤ 0.02) decrease in IMI (0.60-fold) and IV (0.63-fold; *P ≤ 0.02) when exposed to RVS. In contrast, Trpv1 KO mice exhibited no change in IMI (A) or IV (B) with RVS exposure. n = 7–8 for all groups. Data were analyzed using paired t tests. C and D: summary bar graph of IMI (C) and IV (D) of B6.Cg-Kit^w-sh control mice and B6.Cg-Kit^w-sh mice exposed to RVS. B6.Cg-Kit^w-sh mice exposed to RVS exhibited increased IMI (1.61-fold; *P ≤ 0.053) and IV (functional bladder capacity) (1.61-fold; *P ≤ 0.054) that approached significance. Data were analyzed using t tests. n = 4–8 for both groups.

Figure 4.

Representative conscious cystometry traces for wild-type (WT) control, WT repeated variate stress (RVS), WT RVS + capsazepine (CPZ), transient receptor potential vanilloid 1 (Trpv1) knockout (KO) control, Trpv1 KO RVS, B6.Cg-Kit^w-sh control, or B6.Cg-Kit^w-sh RVS groups. WT mice exposed to RVS exhibited a significantly (see also Fig. 2A; P ≤ 0.02) decreased intermicturition interval (IMI) (decreased bladder capacity) compared to other groups. The WT RVS group after CPZ treatment (WT RVS + CPZ) did not exhibit a difference in IMI compared to WT control or any other group. Trpv1 KO mice under control condition (no RVS) or exposed to RVS also did not exhibit any difference in IMI compared to WT control mice. B6.Cg-Kit^w-sh mice exposed to RVS exhibited increased IMI (increased bladder capacity) approaching significance compared to B6.Cg-Kit^w-sh control (no RVS) mice. The calibration bar represents pressure (mmHg) and time (s). Data were analyzed using one-way ANOVA.

Figure 5.

Wild-type (WT) and transient receptor potential vanilloid 1 (Trpv1) knockout (KO) mice exposed to repeated variate stress (RVS) exhibit anxiety-like behaviors. A: WT mice exposed to RVS spent significantly less time in the open area of the testing field compared to WT control (no RVS) and Trpv1 KO control (no RVS) groups (***P ≤ 0.0006 for both groups). Trpv1 KO mice spent significantly less time in the open area compared to WT control (**P ≤ 0.001) and Trpv1 KO control (**P ≤ 0.001) groups. B and C: representative yarn plots (B) showing the path and heat maps (C) showing where mice spent the most time during an open-field test for Trpv1 KO control (no stress; B) and Trpv1 KO mice exposed to RVS (C). Data were analyzed using one-way ANOVA. n = 7–8 for all groups.

Figure 6.

Transient receptor potential vanilloid 1 (TRPV1) expression is increased in the rostral lumbar (L1-L2) spinal cord (SC) and dorsal root ganglia (DRG) in wild-type (WT) mice exposed to repeated variate stress (RVS) or capsazepine (CPZ) treatment. A: in the L1 spinal cord, mice exposed to RVS and mice exposed to RVS and that received CPZ (RVS + CPZ) exhibited significantly (*P ≤ 0.01 and **P ≤ 0.001, respectively) greater TRPV1 expression (1.44- to 1.45-fold increase) compared to WT control (no RVS) mice. B: in the L2 spinal cord, mice exposed to RVS also exhibited (*P ≤ 0.04) increased TRPV1 expression (1.45-fold increase) compared to WT control (no RVS) mice. C: no mouse group evaluated (WT control, WT RVS, WT RVS + CPZ, Trpv1 KO control, or Trpv1 KO RVS) exhibited any changes in TRPV1 expression in L1 DRG. D: mice exposed to RVS exhibited a significant (*P ≤ 0.047) increase in TRPV1 expression (1.4-fold increase) in L2 DRG compared to WT control (no RVS) mice. Mice exposed to RVS + CPZ exhibited a significant (*P ≤ 0.04) increase (1.58-fold increase) in TRPV1 expression in L2 DRG compared to control (no RVS) mice exposed to CPZ (control + CPZ). Data were analyzed using one-way ANOVA. n = 3–20 for all groups.