Urothelium dysfunction contributes to diverse lower urinary tract disorders, e.g. overactive bladder syndrome (OAB). OAB is age-related and highly prevalent in both men and women. In OAB, increased neurotransmitter acetylcholine (ACh) release and signaling via nicotinic and muscarinic receptors (mAChR) expressed by detrusor muscle cells leads to dysregulated bladder contraction, and thus frequency, urgency and sometimes incontinence. Recent evidence shows that urothelial cells also release ACh and express mAChRs, establishing the theory that an ACh autocrine loop contributes to urothelial sensory dysfunction. Whether this autocrine loop also contributes to the urothelium's protective functions, e.g. innate immune responses mediated by Toll-like receptors (TLR) or IL22 remains unknown - TLRs detect bacterial products, while the cytokine IL22 regulates antimicrobial peptide (AMP) expression; thus, they both control bacterial infection. Since mAChR-mediated signal transduction depends on PI3 kinase activation, which also modulates the TLR-mediated innate immune response, we propose a new OAB paradigm, in which an ACh autocrine loop affects the ability of human urothelial cells (HUCs) to generate proper TLR- and IL22-mediated innate immune responses. We hypothesize that HUCs from OAB patients display two abnormalities: 1) dysfunctional TLR signaling; and 2) altered IL22- regulated AMP production. We further hypothesize that these urothelial changes in OAB are differentially modulated by bacterial products from the newly discovered urinary microbiota. For this study, we established a system to culture primary urothelial cells from human bladder biopsies. We expect that results from this study will establish: 1) increased ACh response affects innate immune responses mediated by IL22 and TLRs; 2) IL22 as an important innate component of the human urothelium that maintains protection against bacterial infection; 3) bacterial products from commensal and pathogenic bacteria differentially affect TLR- and IL22- mediated responses in urothelium of OAB versus non-OAB patients. This new knowledge will advance understanding of urothelium dysfunctions in OAB in the elderly.
The main goal of this proposal is to understand at the molecular and cellular levels how the dysfunctional urothelium of overactive bladder (OAB) affects the innate immune response. OAB is an age-related condition that reduces quality of life in the elderly and imposes a financial burden. The results from the proposed study are expected to identify new potential therapeutic targets to effectively treat OAB in the elderly.
