Increased polyamine signaling in bladder urothelial cells (BUC) may play a role in the pathophysiology of overactive bladder (OAB).
We quantitated intracellular polyamine levels in cultured BUC from OAB and asymptomatic (NB) subjects. We assessed whether polyamines modulated rapid intracellular calcium ([Ca2+]i) changes and delayed acetylcholine (ACh) release evoked by oxotremorine (OXO, a muscarinic agonist). BUC were cultured from cystoscopic biopsies. High performance liquid chromatography (HPLC) quantitated intracellular putrescine, spermidine and spermine levels. 5 mM difluoromethylornithine (DFMO) and 1 mM methylglyoxalbisguanylhydrazone (MGBG) treatments were used to deplete intracellular polyamines. 10 µM OXO was used to increase [Ca2+]i levels (measured by fura-2 microfluorimetry) and trigger extracellular ACh release (measured by ELISA). Polyamine levels were elevated in OAB compared to NB BUC (0.5±0.15 vs 0.16±0.03 nmol/mg for putrescine, 2.4±0.21 vs 1.01±0.13 nmol/mg for spermidine, 1.90±0.27 vs 0.86±0.26 nmol/mg for spermine, p< 0.05 for all comparisons). OXO evoked greater [Ca2+]i rise in OAB (205.10%±18.82% increase over baseline) compared to in NB BUC (119.54%±13.01%, p< 0.05). After polyamine depletion, OXO evoked [Ca2+]i rise decreased in OAB and NB BUC to 43.40% ±6.45% and 38.82%±3.5%, respectively. OXO tended to increase ACh release by OAB versus NB BUC (9.02±0.1 versus 7.04±0.09 µM, respectively, p< 0.05). Polyamine depletion reduced ACh release by both OAB and NB BUC. In conclusion, polyamine levels were elevated 2 fold in OAB BUC. OXO evoked greater increase in [Ca2+]i and ACh release in OAB BUC, though these two events may be unrelated. Depletion of polyamines caused OAB BUC to behave similarly to NB BUC.
Written by:
Li M, Sun Y, Tomiya N, Hsu Y, Chai TC. Are you the author?
University of Maryland School of Medicine.
Reference: Am J Physiol Renal Physiol. 2013 May 22. Epub ahead of print.
doi: 10.1152/ajprenal
PubMed Abstract
PMID: 23698115
UroToday.com Investigative Urology Section
