Na Channels in Afferents after Bladder Obstruction

描述（由申请人提供）：良性前列腺增生（BPH）在四分之一的男性中发展。超过10亿美元用于缓解由膀胱过度活跃（OAB）引起的前列腺增生的恼人症状。这些症状可能包括尿急、尿频、夜尿和急迫性尿失禁。局部麻醉和微创手术可使膀胱和尿道的感觉输入钝化，但不能消除阻塞。通过啮齿类动物部分尿道结扎模型，研究者推测OAB可能源于下尿路肌肉和神经的改变。梗阻（OBS）大鼠表现出尿频和逼尿肌过度活动，这与传入神经肥厚的发展、脊髓反射增强和神经生长因子（NGF）的升高在时间上相关。NGF免疫可抑制神经可塑性和OAB。因此，NGF作为一种细胞因子被认为参与了这些事件，NGF影响传入兴奋性的能力被认为部分来源于改变Na电导，而Na电导反过来又依赖于Na通道异构体的表达。数据显示，OBS大鼠传入神经的免疫组化（IHC）染色显示Nay1.8亚型降低。这种Na α亚基在c纤维传入中产生抗河豚毒素（TTX-R）钠（Na）电流。此外，一个反义（AS）而不是错配的寡脱氧核苷酸（ODN）可以减少OAB。我们假设，在OBS大鼠中，1)传入兴奋性增加存在，2)OAB和传入兴奋性是由于钠（Na）电导的改变，3)鞘内AS ODN抑制Na通道异构体(s)减少传入高兴奋性和OAB， 4) NGF参与传入兴奋性增强，Na通道功能改变和/或异构体表达的发生。这些假设将通过确定是否阻塞与假手术相比，1)基于膜片钳分析改变标记的传入膀胱神经元的电特性，2)使用免疫组化和Western blotting改变Na通道同种异构体的表达，以及3)兴奋性或蛋白质表达的改变是否可逆与排尿行为的指定和正常化来验证。NGF协调这些事件的能力将通过观察NGF免疫或trkA拮抗剂是否与对照组相比阻止OBS的电学性质和蛋白质表达的变化来阐明。深入了解这些细胞过程可以利用药理学、分子或基因为基础的策略开发基于传入的OAB治疗。

DESCRIPTION (provided by applicant): Benign prostatic hyperplasia (BPH) develops in one out of four men. In excess of $1 billion is spent to relieve bothersome symptoms of BPH due to an overactive bladder (OAB). These symptoms may include urgency, frequency, nocturia and urge incontinence. Symptoms can be relieved by local anesthetics and minimally invasive procedures that blunt sensory input from the bladder and urethra yet fail to un-obstruct. Using the partial urethral ligation model in rodents, investigators postulate that OAB may originate from changes in muscle and nerves in the lower urinary tract. Obstructed (OBS) rats exhibit urinary frequency and detrusor overactivity temporally correlated to the development of afferent hypertrophy, an enhanced spinal reflex, and a rise in nerve growth factor (NGF). Immunity to NGF prevents both neural plasticity and OAB. Therefore, NGF acting as a cytokine is thought to participate in these events, NGF's ability to influence afferent excitability is thought to derive, in part, from altering Na conductances, which in turn depends on Na channel isoform expression. Data suggests that afferents from OBS rats exhibit decreased immunohistochemical (IHC) staining for the Nay1.8 isoform. This Na alpha subunit gives rise to tetrodotoxin resistant (TTX-R) sodium (Na) currents in C-fiber afferents. Moreover, an antisense (AS) but not mismatch oligodeoxynucleotide (ODN) against this isoform reduces OAB. We postulate that in OBS rats 1) increased afferent excitability exists, 2) OAB and afferent excitability are due to an alteration in sodium (Na) conductance, 3) knockdown of Na channel isoform(s) using intrathecal AS ODN reduces afferent hyperexcitability and OAB, and 4) NGF participates in the genesis of enhanced afferent excitability, alterations in Na channel function and/or isoform expression. These hypotheses will be tested by determining whether obstruction compared to sham surgery 1) alters electrical properties of labeled afferent bladder neurons based on patch clamp analysis, 2) changes expression of Na channel isoforms using IHC and Western blotting, and 3) whether alterations in excitability or protein expression are reversible with deligation and normalization of voiding behavior. The ability of NGF to orchestrate these events will be elucidated by noting if NGF immunity or trkA antagonists prevent changes in electrical properties and protein expression in OBS compared to controls. Insight into these cellular processes could be exploited to develop afferent based treatments for OAB employing pharmacologic, molecular or gene based strategies.