Obstruction stimulates COX-2 expression in bladder smooth muscle cells via increased mechanical stretch

Abstract

Studies were performed to investigate the regulatory mechanism of bladder cyclooxygenase-2 (COX-2) expression after outlet obstruction. In situ hybridization of murine bladder tissues using COX-2-specific riboprobes demonstrated that COX-2 expression was induced predominantly in the bladder smooth muscle cells after outlet obstruction. To study the effect of increased mechanical stretch on COX isoform expression, cultured rat bladder smooth muscle cells were grown on silicone elastomer-bottomed plates coated with collagen type I and were subjected to continuous cycles of stretch/relaxation for variable duration. COX-1 mRNA levels did not change with stretch. COX-2 expression increased in a time-dependent manner after stretch, with maximal mRNA and protein levels occurring after 4 h. PGE2 levels increased more than 40-fold in the culture media after stretch, consistent with increased COX activity, and this was reduced to near completion in the presence of a COX-2 inhibitor, NS-398. Exposure to stretch over a 48-h period induced a 4.7 ± 0.6-fold increase in tritiated thymidine incorporation rate. This increase in DNA synthesis was markedly suppressed when the cells were stretched in the presence of NS-398. We conclude that in bladder obstruction COX-2 activation occurs predominantly in the smooth muscle cells in response to mechanical stretch. Our findings also suggest that stretch-activated COX-2 expression may participate in bladder smooth muscle cell proliferation and thereby play a role in pathological bladder wall thickening after obstruction.

Involvement of Cyclooxygenase-2 in Synergistic Effect of Cyclic Stretching and Eicosapentaenoic Acid on Adipocyte Differentiation

“…It has been reported that several COX inhibitors also act as PPARγ agonists (27,28). However, the concentration of NS-398 (10 µM) used in this study has been used before (for example, 5 -50 µM) for specific inhibition of COX-2 (8,19,29). In fact, we did not observe any apparent effect of NS-398, when used during the induction period, on the triglyceride accumulation in the maturation period (Fig.…”

Involvement of hypoxia-triggered endoplasmic reticulum stress in outlet obstruction-induced apoptosis in the urinary bladder

“…An experimental model of BOO was established as described in Materials and Methods, and after 24 h, expression of endogenous indicators for individual stress was evaluated by northern blot analysis. The indicators used were COX-2 for mechanical stress, 17 GAPDH and VEGF for hypoxic stress [18][19][20] and GRP78 and CHOP for ER stress. 7,21 Northern blot analysis showed that, compared with untreated and sham-operated rats, rats subjected to BOO exhibited induction of COX-2 (Figure 1a), GAPDH and VEGF (Figure 1b) in the bladders.…”

Cyr61 and CTGF are molecular markers of bladder wall remodeling after outlet obstruction

“…Baskin and colleagues (3,4) have reported an increase in transforming growth factor (TGF)-␤2, TGF-␤3, and TGF-␣ in bladders subjected to partial urethral outlet obstruction and correlate such increases with excessive deposition of extracellular matrix proteins. Studies in various animal models and in humans showed that hypertrophied obstructed bladders contain significantly more insulin-like growth factor I (IGF-I) and cyclooxygenase-2 than normal bladders (1,11,43). Other studies emphasized the role of the renin-angiotensin system and inducible nitric oxide synthase in the early responses of the bladder to the outlet obstruction (5,12).…”