Urinary levels of substance P and its metabolites are not increased in interstitial cystitis

Neuroepithelial control of mucosal inflammation in acute cystitis

The nervous system is engaged by infection, indirectly through inflammatory cascades or directly, by bacterial attack on nerve cells. Here we identify a neuro-epithelial activation loop that participates in the control of mucosal inflammation and pain in acute cystitis. We show that infection activates Neurokinin-1 receptor (NK1R) and Substance P (SP) expression in nerve cells and bladder epithelial cells in vitro and in vivo in the urinary bladder mucosa. Specific innate immune response genes regulated this mucosal response, and single gene deletions resulted either in protection (Tlr4^−/− and Il1b^−/− mice) or in accentuated bladder pathology (Asc^−/− and Nlrp3^−/− mice), compared to controls. NK1R/SP expression was lower in Tlr4^−/− and Il1b^−/− mice than in C56BL/6WT controls but in Asc^−/− and Nlrp3^−/− mice, NK1R over-activation accompanied the exaggerated disease phenotype, due, in part to transcriptional de-repression of Tacr1. Pharmacologic NK1R inhibitors attenuated acute cystitis in susceptible mice, supporting a role in disease pathogenesis. Clinical relevance was suggested by elevated urine SP levels in patients with acute cystitis, compared to patients with asymptomatic bacteriuria identifying NK1R/SP as potential therapeutic targets. We propose that NK1R and SP influence the severity of acute cystitis through a neuro-epithelial activation loop that controls pain and mucosal inflammation.

Peripheral tachykinin receptors as potential therapeutic targets in visceral diseases

More than 10 years of intensive preclinical investigation of selective tachykinin (TK) receptor antagonists has provided a rationale to the speculation that peripheral neurokinin (NK)-1, -2 and -3 receptors may be involved in the pathophysiology of various human diseases at the visceral level. In the airways, despite promising effects in animal models of asthma, pilot clinical trials with selective NK-1 or -2 receptor antagonists in asthmatics have been ambiguous, whereas the potential antitussive effects of NK-1, -2 or -3 antagonists have not yet been verified in humans. In the gastrointestinal (GI) tract, irritable bowel syndrome (IBS) and pancreatitis are appealing targets for peripherally-acting NK-1 and -2 antagonists, respectively. In the genito-urinary tract, NK-1 receptor antagonists could offer some protection against nephrotoxicity and cytotoxicity induced by chemotherapeutic agents, whereas NK-2 receptor antagonists appear to be promising new agents for the treatment of neurogenic bladder hyperreflexia. Finally, there is preclinical evidence for hypothesising an effect of NK-3 receptor antagonists on the cardiovascular disturbance that characterises pre-eclampsia. Other more speculative applications are also mentioned.

Effects of dimethyl sulphoxide and heparin on stretch-activated ATP release by bladder urothelial cells from patients with interstitial cystitis

OBJECTIVE

To determine whether dimethyl sulphoxide (DMSO) and heparin reduce the greater stretch-activated ATP release in interstitial cystitis (IC), as ATP serves as a nocio-neurotransmitter in the bladder, and thus explain their beneficial effects in patients with IC (a disease characterized by hypersensory bladder symptoms).

MATERIALS AND METHODS

Bladder epithelia in IC release more ATP in response to stretch than do control samples. Both DMSO and heparin are used intravesically to treat IC; such agents can modulate urothelial function because they directly contact bladder urothelium. Biopsies taken from patients with IC and from control subjects were grown in primary cultures using established cell-culture techniques. Cultured urothelial cells were stretched with the Flexcell device (Flexcell International Corp., McKeesport, PA, USA) and supernatant ATP was measured, using a luciferin-luciferase assay. DMSO (0.1%, 0.5% and 1%) or heparin (50, 200, 800 and 1600 U) was added to the cells at the start of the stretch experiments and the ATP released into the supernatant measured. Cell viability was also determined using Trypan Blue staining.

RESULTS

IC cells released significantly more ATP in response to stretch than did control cells. This increased release of ATP by stretched IC cells was significantly blocked by adding DMSO or heparin at all concentrations used. Heparin appeared to have a greater dose-dependent effect on ATP release than did DMSO.

CONCLUSIONS

These findings are consistent with the hypothesis that the urothelium provides sensory input via ATP release and that this process is increased in IC. Furthermore, stretch-activated ATP release was blocked by adding DMSO and heparin, both intravesical agents commonly used to treat the symptoms of IC. This study supports the notion that purinergic-targeted therapy is warranted in treating IC. Further studies are needed to determine the mechanisms of increased ATP release by IC urothelial cells.

Interstitial cystitis: an update

PURPOSE OF REVIEW

Interstitial cystitis is a chronically progressive, severely debilitating, heterogeneous syndrome affecting the urinary bladder, mainly associated with urgency, frequency and pain. Though known for over a century, its etiology is poorly understood and universally effective treatments are lacking. This review focuses on recently published literature on the disorder.

RECENT FINDINGS

Appropriate diagnostic tests for interstitial cystitis remain uncertain. The diagnostic criteria developed by the US National Institutes of Health represent research definitions which are subject to controversial debate for their overenthusiastic clinical application. The diagnosis is made clinically and by cystoscopy with hydrodistention and sometimes biopsy when other pathologies have been excluded. In symptomatic patients, glomerulations upon bladder distension are indicative but not pathognomonic for nonulcerative interstitial cystitis. Patients with ulcerative disease represent a separate subgroup with distinct characteristics and treatment implications. The role of bladder permeability tests remains controversial. Promising noninvasive markers for interstitial cystitis have been described but are not yet clinically available. Validated symptom scores are appropriate to assist in diagnostics and to monitor disease course and treatment efficacy. Lately investigated hypotheses for causative factors include occult or resistant microorganisms, urothelial hyperpermeability, neurogenic or hormonal pathomechanisms, and mast cell activation. Increasing evidence for a genetic susceptibility is emerging.

SUMMARY

Among the multitude of oral, intravesical, interventional and complementary treatments suggested few studies have high levels of evidence. Newly proposed agents must await further controlled studies. Treatment remains empiric until radical surgical procedures should ultimately be considered for severe refractory cases.

Interstitial cystitis

Appropriate diagnostic tests for interstitial cystitis remain uncertain. One or more promising markers for this disease have been described which may provide a noninvasive means for diagnosis as well as clues to pathogenesis of this disease. Treatment remains empiric.