Gomez-Pinilla Pedro J, Gomez Maria F, Swärd Karl, Hedlund Petter, Hellstrand Per, Camello Pedro J, Andersson Karl-Erik, Pozo María J
Department of Physiology, Nursing School, University of Extremadura, Caceres, Spain.
J Pineal Res. 2008 May;44(4):416-25. doi: 10.1111/j.1600-079X.2007.00544.x. Epub 2008 Jan 9.
Urinary bladder disturbances are frequent in the elderly population but the responsible mechanisms are poorly understood. This study evaluates the effects of aging on detrusor myogenic contractile responses and the impact of melatonin treatment. The contractility of bladder strips from adult, aged and melatonin-treated guinea pigs was evaluated by isometric tension recordings. Cytoplasmatic calcium concentration (Ca(2+)) was estimated by epifluorescence microscopy of fura-2-loaded isolated detrusor smooth muscle cells, and the levels of protein expression and phosphorylation were quantitated by Western blotting. Aging impairs the contractile response of detrusor strips to cholinergic and purinergic agonists and to membrane depolarization. The impaired contractility correlates with increased Ca(2+) in response to the stimuli, suggesting a reduced Ca(2+)sensitivity. Indeed, the agonist-induced contractions in adult strips were sensitive to blockade with Y27362, an inhibitor of Rho kinase (ROCK) and GF109203X, an inhibitor of protein kinase C (PKC), but these inhibitors had negligible effects in aged strips. The reduced Ca(2+) sensitivity in aged tissues correlated with lower levels of RhoA, ROCK, PKC and the two effectors CPI-17 and MYPT1, and with the absence of CPI-17 and MYPT1 phosphorylation in response to agonists. Interestingly, melatonin treatment restored impaired contractility via normalization of Ca(2+) handling and Ca(2+) sensitizations pathways. Moreover, the indoleamine restored age-induced changes in oxidative stress and mitochondrial polarity. These results suggest that melatonin might be a novel therapeutic tool to palliate aging-related urinary bladder contractile impairment.
膀胱功能障碍在老年人群中很常见，但相关机制尚不清楚。本研究评估衰老对逼尿肌肌源性收缩反应的影响以及褪黑素治疗的作用。通过等长张力记录评估成年、老年和褪黑素处理的豚鼠膀胱条的收缩性。通过对负载fura-2的分离逼尿肌平滑肌细胞进行落射荧光显微镜检查来估计细胞质钙浓度（Ca(2+)），并通过蛋白质印迹法定量蛋白质表达和磷酸化水平。衰老会损害逼尿肌条对胆碱能和嘌呤能激动剂以及膜去极化的收缩反应。收缩性受损与刺激后Ca(2+)增加相关，提示钙敏感性降低。实际上，成年条中激动剂诱导的收缩对Rho激酶（ROCK）抑制剂Y27362和蛋白激酶C（PKC）抑制剂GF109203X的阻断敏感，但这些抑制剂对老年条的作用可忽略不计。老年组织中钙敏感性降低与RhoA、ROCK、PKC以及两个效应器CPI-17和MYPT1水平较低相关，且对激动剂无CPI-17和MYPT1磷酸化。有趣的是，褪黑素治疗通过钙处理和钙敏化途径的正常化恢复了受损的收缩性。此外，吲哚胺恢复了年龄诱导的氧化应激和线粒体极性变化。这些结果表明，褪黑素可能是缓解衰老相关膀胱收缩功能障碍的一种新型治疗工具。
