Elevated polyamines in urothelial cells from OAB subjects mediate oxotremorine-evoked rapid intracellular calcium rise and delayed acetylcholine release

• Published in: American journal of physiology. Renal physiology Vol. 305; no. 4; pp. F445 - F450
• Main Authors: Li, Mingkai, Sun, Yan, Tomiya, Noboru, Hsu, Yuchao, Chai, Toby C.
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 15.08.2013
• Subjects: Acetylcholine; Acetylcholine - metabolism; Amino acids; Calcium; Calcium - metabolism; Cells; Cells, Cultured; Chromatography; Chromatography, High Pressure Liquid; Female; Fluorescent Antibody Technique; Humans; Oxotremorine - pharmacology; Polyamines - metabolism; Putrescine - metabolism; Signal Transduction; Spermidine - metabolism; Spermine - metabolism; Translational Physiology; Urinary Bladder, Overactive - metabolism; Urothelium - metabolism; polyamine; intracellular calcium; urothelial cells; overactive bladder; muscarinic signaling
• ISSN: 1931-857X; 1522-1466; 1522-1466
• DOI: 10.1152/ajprenal.00345.2012

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 ([Ca 2+ ] 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. Five-millimeter difluoromethylornithine (DFMO), and one-millimeter methylglyoxalbisguanylhydrazone (MGBG) treatments were used to deplete intracellular polyamines. Ten micrometers of OXO were used to increase [Ca 2+ ] i levels (measured by fura 2 microfluorimetry) and trigger extracellular ACh release (measured by ELISA). Polyamine levels were elevated in OAB compared with 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, and 1.90 ± 0.27 vs. 0.86 ± 0.26 nmol/mg for spermine; P < 0.05 for all comparisons). OXO evoked greater [Ca 2+ ] i rise in OAB (205.10 ± 18.82% increase over baseline) compared with in NB BUC (119.54 ± 13.01%; P < 0.05). After polyamine depletion, OXO evoked [Ca 2+ ] 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 vs. NB BUC (9.02 ± 0.1 vs. 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 twofold in OAB BUC. OXO evoked greater increase in [Ca 2+ ] i and ACh release in OAB BUC, although these two events may be unrelated. Depletion of polyamines caused OAB BUC to behave similarly to NB BUC.