The urothelium drives changes to urinary bladder smooth muscle contractility that mimic neurogenic inflammatory signaling

Abstract

Neurogenic inflammation disrupts urothelial homeostasis, which leads to barrier injury, cellular turnover, and dysregulated release of ATP and prostaglandins resulting in urinary bladder smooth muscle instability. Increased urothelium signaling is implicated in many bladder pathologies, such as idiopathic detrusor overactivity, interstitial cystitis, and recurrent urinary tract infections, in animal models along with patients. Previously, we utilized compound 48/80 as a pro-inflammatory agent on urinary bladder smooth muscle strips, which resulted in urothelium-dependent increases in smooth muscle phasic activity and augmented nerve-evoked contractions. Thus, we hypothesized that compound 48/80 causes spontaneous rhythmic contractions dependent on the release of urothelial-derived prostaglandins (PGE2, PGF2 alpha, Thromboxane A2) and pannexin-1-mediated ATP release, similar to neurogenic signaling pathways that drive smooth muscle hyperactivity. Tissue bath studies were performed with urothelium intact or denuded urinary bladder smooth muscle strips from 8–12-week-old male C57BL/6 mice (n=1 strip from N=5-6) to measure isometric contractility and nerve-evoked contractions in the presence of pharmacological inhibitors and compound 48/80 (10 μg/mL). Prior to compound 48/80 exposure, strips of urothelium were returned to the bottom of the organ tissue bath chambers directly underneath denuded smooth muscle strips to assess if soluble mediators were released. The non-selective cyclooxygenase inhibitor indomethacin (5 μM) diminished compound 48/80 augmentation of nerve-evoked contractions. However, the neurokinin 1 antagonist QWF (10 μM), PGF2 alpha FP receptor antagonist AL8810 (5 μM), PGE2 EP1 receptor antagonist SC51089 (10 μM), Thromboxane A2 TP receptor antagonist GR32191B (1 μM), and pannexin-1 mimetic inhibitory peptide 10Panx (200 μM) had no effect on compound 48/80-induced contractions compared to respective vehicle controls ( p=0.18, 0.91, 0.57, 0.41, and 0.44, respectively). A cocktail of all prostaglandin antagonists did significantly reduce contractions ( p=0.01). Interestingly, despite the physical distance of the detached urothelium, exposure to compound 48/80 resulted in increased contractility ( p=0.016) and phasic activity ( p=0.017) as compared to a urothelium-denuded strips. These results suggest that activation of urothelial signaling via compound 48/80 mimics neurogenic inflammation to release a wide array of prostaglandins capable of altering bladder smooth muscle contractility. Thus, the urothelium should be considered as an inflammatory milieu whereby physiological and pharmacological changes contribute to urinary bladder smooth muscle dysfunction. This research is supported by NIH P20-DK127554 (NRT), NIH R01-DK119615 (NRT & GCM; supplement to BMJ) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.