Experimental colitis triggers the release of substance P and calcitonin gene-related peptide in the urinary bladder via TRPV1 signaling pathways

Abstract

Clinical data provides evidence of high level of co-morbidity among genitourinary and gastrointestinal disorders characterized by chronic pelvic pain. The objective of this study was to test the hypothesis that colonic inflammation can impact the function of the urinary bladder via activation of TRPV1 signaling pathways followed by alterations in gene and protein expression of Substance P (SP) and calcitonin gene-related peptide (CGRP) in sensory neurons and in the bladder. Inflammation was induced by intracolonic instillation of trinitrobenzene sulfonic acid (TNBS, 12.5 mg/kg) and desensitization of TRPV1 receptors was evoked by intracolonic resiniferatoxin (RTX, 10 −7 M). mRNA and protein concentrations of CGRP and SP were measured at 3, 5 and 30 days. RTX instillation in the colon caused 3-fold up-regulation of SP mRNA in the urinary bladder at day 5 (n=7, p≤0.05) followed by 35-fold increase at day 30 (n=5, p≤0.05). Likewise, TNBS colitis triggered 15.8-fold up-regulation of SP mRNA one month after TNBS (n=5, p≤0.05). Desensitization of colonic TRPV1 receptors prior to TNBS abolished SP increase in the urinary bladder. RTX led to 4.3-fold increase of CGRP mRNA at day 5 (n=7, p≤0.05 to control) in the bladder followed by 28-fold increase at day 30 post-RTX (n=4, p≤0.05). Colitis did not alter CGRP concentration during acute phase, however, at day 30 mRNA level was increased by 17.8±6.9 fold (n=5, p≤0.05) in parallel with 4-fold increase in CGRP protein (n=5, p≤0.01) in the detrusor. Protein concentration of CGRP in the spinal cord was diminished by 45-65% (p≤0.05) during colitis. RTX pretreatment did not affect CGRP concentration in the urinary bladder, however, caused a reduction in CGRP release from lumbosacral DRG neurons during acute phase (3 and 5 days post-TNBS). Our results clearly demonstrate that colonic inflammation triggers the release of pro-inflammatory neuropeptides SP and CGRP in the urinary bladder via activation of TRPV1 signaling mechanisms enunciating the neurogenic nature of pelvic organ cross-sensitization.

Acute colonic inflammation triggers detrusor instability via activation of TRPV1 receptors in a rat model of pelvic organ cross-sensitization

“…3). We previously tested if TNBS could also trigger minor bladder inflammation by using MPO assay and H&E staining (34). Analysis of the H&E-stained cross sections of the urinary bladder performed in this study showed that neither RTX nor TNBS (alone or in combination) caused detectable structural changes in the urinary bladder, confirming that the urinary bladder did not develop any signs of acute inflammatory reaction (Fig.…”

“…Our previous studies showed that animals with the DAI score of four and above developed distinct histological changes in the colon (thickening of the colonic wall, signs of hemorrhage, etc.) without noticeable histological or biochemical changes in the urinary bladder in this model of colon-bladder crosssensitization (28,34). Because RTX treatment does not lead to the development of hemorrhage, wall thickening, and/or gastrointestinal bleeding, two groups treated either with RTX alone or with RTX-TNBS were not assessed using DAI.…”

“…Segments of the colon and bladder (0.5-0.7 cm) were fixed in 4% paraformaldehyde for histological studies and hematoxylin and eosin (H&E) staining; another part of each organ was snap-frozen for myeloperoxidase (MPO) assay as previously described (34). In vitro measurements of detrusor contractility.…”

“…Midline laparotomy was performed to remove the bladders and distal colon. The colon was evaluated for the signs of hemorrhage and wall thickening in all groups as described in our previous studies (28,34). The results of histological evaluation of the bladder and colon cross sections are presented in Fig.…”

“…Previous animal studies have established a correlation between structural pathophysiological changes in the directly affected pelvic organs and secondary dysfunctions developed in adjacent pelvic structures (9,27,28,36). It has been determined that colonic inflammation causes hyperactivity of bladder afferent fibers (44), hyperexcitability of bladder projecting sensory (27, 28) and spinal (38) neurons, increased release of proinflammatory neuropeptides in the urinary bladder (34,45), and changes in the detrusor contractility (32). However, the exact pathways of transmission of nociceptive information from the inflamed colon to the urinary bladder as well as receptors and molecules activated during this transmission remain elusive.…”