Prostanoids exert profound physiological effects on the urinary tract including nociception, induction of smooth muscle contractility, enhancement of cell proliferation, and blood flow regulation. The rate-limiting step in prostanoid synthesis is catalyzed by cyclooxygenase (COX). This enzyme exists in two isoforms: COX-1 (usually constitutive) and COX-2 (highly inducible). COX-2 is substantially induced with distension and stretch of urinary tissues. A new area of interest involving COX activity in urinary tract has been identified: urothelial cell stretch-induced COX-2 expression. In cell culture, urothelial stretch produces a 10-fold induction in COX-2 levels within 6 hours of applying stretch. Since COX-2 upregulation would lead to an increase in soluble prostanoids, this process represents a critical link between urothelial stretch and afferent pain perception, muscle contractility, and cell proliferation. While the specific model of this proposal involves urothelial cells cultured from the ureter, this novel concept has broad implications in the pathophysiology of the urinary tract. The goal of this project is to identify cellular pathways of stretch-induced COX-2 expression and thereby provide several potential targets for drug therapy. Based on titerature reports in other cells, and preliminary data, the hypothesis of this proposal is that stretch activation of PKC and p38 MAP kinase signaling cascades induces COX-2 in urothelial cells.
The Specific Aims are: I. To characterize COX-2 induction in human urothelial cells subjected to mechanical stretch. This will be accomplished by determining the optimal duration and degree of stretch for COX-2 induction in human urothelial cells and determining if stretch-induced COX-2 expression is regulated transcriptionally and/or post-transcriptionally in human urothelial cells. II. To determine if stretch induction of COX-2 is mediated by increased intracellular calcium concentrations [Ca++] i and subsequent PKC and p38 MAP kinase activation. This will be accomplished by determining if stretch of urothelial cells increases [Ca++] i, and activates PKC and p38 MAP kinase, if inhibition of calcium, PKC, or p38 MAP kinase attenuate stretch-induction of COX-2, and if p38-dependent transcriptional factors are involved in stretch-induced COX-2 expression. The findings of this exploratory proposal have great potential to expand into several dynamic lines of research and may identify novel approaches to treating urinary tract disorders such as bladder outlet obstruction, ureteropelvic junction obstruction, and interstitial cystitis.
| Jerde, Travis J; Mellon, William S; Bjorling, Dale E et al. (2006) Evaluation of urothelial stretch-induced cyclooxygenase-2 expression in novel human cell culture and porcine in vivo ureteral obstruction models. J Pharmacol Exp Ther 317:965-72 |
