TRPA1 mediates bladder hyperalgesia in a mouse model of cystitis

Abstract

Urinary bladder pain is a primary symptom associated with interstitial cystitis/painful bladder syndrome. We employed systemic injections of cyclophosphamide (CYP), an alkylating anti-neoplastic agent, to induce cystitis and examine the roles of two channels previously shown to be required for inflammatory visceral hyperalgesia: transient receptor potential vanilloid-1 (TRPV1) and ankyrin-1 (TRPA1). Injection of CYP (100 mg/kg, i.p.) every other day for five days was accompanied by bladder edema and urothelial ulceration, but without significant plasma extravasation or infiltration of neutrophils. Toluidine blue staining showed a significant increase in the number of degranulated bladder mast cells following CYP treatment. Despite this mild pathology, CYP-treated mice exhibited bladder hyperalgesia one day following the final injection that persisted seven days later. Although many previous studies of visceral hyperalgesia have reported changes in dorsal root ganglion neuron TRPV1 expression and/or function, we found no change in bladder afferent TRPV1 expression or sensitivity, based on the percentage of bladder afferents responsive to capsaicin, including at sub-maximal concentrations. In contrast, the percentage of bladder afferents expressing functional TRPA1 protein (i.e., those responsive to mustard oil) increased ~2.5-fold one day after CYP treatment, and remained significantly elevated seven days later. Moreover, bladder hyperalgesia was reversed by acute treatment with the TRPA1 antagonist, HC-030031 (300 mg/kg, i.p.). Our results indicate that CYP-induced bladder hyperalgesia can be induced without robust inflammation or changes in primary afferent TRPV1. However, significant changes were seen in TRPA1 expression, and blockade of TRPA1 alleviated CYP-induced bladder hyperalgesia.

Stress and Chronic Pelvic Pain

“…24,164 Furthermore, early life stress increased TRPA1 protein expression in bladder, 61 while experimental cystitis induced a TRPA1-, but not TRPV1-, dependent hyperalgesia. 165 Expression of metabotropic glutamate receptors were also upregulated primarily in bladder, rather than lumbosacral spinal cord, of mice with CYP-cystitis. 166 Together, these studies suggest that while there are etiological similarities between IBS and IC/PBS, the specific molecular mechanisms contributing towards bladder pain are likely distinct from those contributing towards the more predominantly studied gastrointestinal pain syndromes.…”

Artemin Immunotherapy Is Effective in Preventing and Reversing Cystitis-Induced Bladder Hyperalgesia via TRPA1 Regulation

“…ARTN sensitizes nociceptive afferents, in part, through upregulation and/or augmented function of the ion channels TRPV1 and TRPA1 31, 35 . Recent studies from our labs revealed that bladder afferent TRPA1 contributes to persistent hyperalgesia in a mouse model of cyclophosphamide (CYP)-induced cystitis 16 . Because of the previously demonstrated relationship between ARTN and TRPA1 expression, we hypothesized that treatment with an ARTN-neutralizing antibody (α-ARTN) might be effective in blocking bladder hyperalgesia.…”

“…To test our hypothesis, we used a mouse model of cystitis shown previously to elicit changes in TRPA1 expression and function 16 and quantified urinary bladder expression of growth factor mRNAs, bladder primary afferent TRPA1 expression and function, nociceptive behavior, and spinal pERK immunoreactivity. A single injection of α-ARTN, either at the initiation or the conclusion of CYP treatment, effectively blocked or reversed, respectively, bladder hyperalgesia.…”

Sensory TRP Channels

“…In addition to colonic afferents, enterochromaffin cells in the gastrointestinal tract express TRPA1, where it may be involved in manifestation of inflammatory disorders such as Crohn’s disease and colitis. 195,196 TRPA1 is also expressed in skin, where keratinocytes showed changes in inflammatory mediator secretion in response to TRPA1 activation. 197 Sensory afferents expressing TRPA1 also innervate the bladder and prostate, raising the possibility that TRPA1 is involved in cystitis-associated pain.…”

“…197 Sensory afferents expressing TRPA1 also innervate the bladder and prostate, raising the possibility that TRPA1 is involved in cystitis-associated pain. 196 …”