Department of Pharmacology and Pharmacotherapy, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Pharmacol Res. 2013 Apr;70(1):147-54. doi: 10.1016/j.phrs.2013.01.010. Epub 2013 Feb 1.
The urothelium plays a crucial role in integrating urinary bladder sensory outputs, responding to mechanical stress and chemical stimulation by producing several diffusible mediators, including ATP and, possibly, neurotrophin nerve growth factor (NGF). Such urothelial mediators activate underlying afferents and thus may contribute to normal bladder sensation and possibly to the development of bladder overactivity. The muscle-contracting and pain-inducing peptide bradykinin is produced in various inflammatory and non-inflammatory pathologies associated with bladder overactivity, but the effect of bradykinin on human urothelial function has not yet been characterized. The human urothelial cell line UROtsa expresses mRNA for both B1 and B2 subtypes of bradykinin receptors, as determined by real-time PCR. Bradykinin concentration-dependently (pEC50=8.3, Emax 4434±277nM) increased urothelial intracellular calcium levels and induced phosphorylation of the mitogen-activated protein kinase (MAPK) ERK1/2. Activation of both bradykinin-induced signaling pathways was completely abolished by the B2 antagonist icatibant (1μM), but not the B1 antagonist R715 (1μM). Bradykinin-induced (100nM) B2 receptor activation markedly increased (192±13% of control levels) stretch-induced ATP release from UROtsa in hypotonic medium, the effect being dependent on intracellular calcium elevations. UROtsa cells also expressed mRNA and protein for NGF and spontaneously released NGF to the medium in the course of hours (11.5±1.4pgNGF/mgprotein/h). Bradykinin increased NGF mRNA expression and accelerated urothelial NGF release to 127±5% in a protein kinase C- and ERK1/2-dependent manner. Finally, bradykinin up-regulated mRNA for transient-receptor potential vanilloid (TRPV1) sensory ion channel in UROtsa. In conclusion, we show that bradykinin represents a versatile modulator of human urothelial phenotype, accelerating stretch-induced ATP release, spontaneous release of NGF, as well as expression of sensory ion channel TRPV1. Bradykinin-induced changes in urothelial sensory function might contribute to the development of bladder dysfunction.
尿路上皮在整合膀胱感觉输出方面起着至关重要的作用，通过产生几种可扩散的介质（包括 ATP 以及可能的神经营养因子神经生长因子 (NGF)）来响应机械应激和化学刺激。这种尿路上皮介质激活了下面的传入神经，因此可能有助于正常的膀胱感觉，并可能有助于膀胱过度活动的发展。肌肉收缩和引起疼痛的肽缓激肽在与膀胱过度活动相关的各种炎症和非炎症性病理中产生，但缓激肽对人尿路上皮功能的影响尚未得到描述。人尿路上皮细胞系 UROtsa 通过实时 PCR 确定表达 B1 和 B2 两种缓激肽受体亚型的 mRNA。缓激肽浓度依赖性地（pEC50=8.3，Emax 4434±277nM）增加尿路上皮细胞内钙水平，并诱导丝裂原活化蛋白激酶 (MAPK) ERK1/2 的磷酸化。两种缓激肽诱导的信号通路的激活均被 B2 拮抗剂 icatibant（1μM）完全阻断，但 B1 拮抗剂 R715（1μM）则不然。缓激肽诱导的（100nM）B2 受体激活显著增加（比对照水平高 192±13%）在低渗介质中 UROtsa 对牵张诱导的 ATP 释放，该作用依赖于细胞内钙的升高。UROtsa 细胞还表达 NGF 的 mRNA 和蛋白，并在数小时内（11.5±1.4pgNGF/mgprotein/h）自发地将 NGF 释放到培养基中。缓激肽以蛋白激酶 C 和 ERK1/2 依赖的方式增加 NGF mRNA 表达并加速尿路上皮 NGF 释放至 127±5%。最后，缓激肽上调 UROtsa 中瞬时受体电位香草酸 (TRPV1) 感觉离子通道的 mRNA。总之，我们表明缓激肽是人类尿路上皮表型的多功能调节剂，可加速牵张诱导的 ATP 释放、NGF 的自发释放以及感觉离子通道 TRPV1 的表达。缓激肽诱导的尿路上皮感觉功能变化可能有助于膀胱功能障碍的发展。
