Saban Ricardo, Simpson Cindy, Vadigepalli Rajanikanth, Memet Sylvie, Dozmorov Igor, Saban Marcia R
Department of Physiology, The University Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
BMC Urol. 2007 May 22;7:7. doi: 10.1186/1471-2490-7-7.
Tachykinins (TK), such as substance P, and their neurokinin receptors which are ubiquitously expressed in the human urinary tract, represent an endogenous system regulating bladder inflammatory, immune responses, and visceral hypersensitivity. Increasing evidence correlates alterations in the TK system with urinary tract diseases such as neurogenic bladders, outflow obstruction, idiopathic detrusor instability, and interstitial cystitis. However, despite promising effects in animal models, there seems to be no published clinical study showing that NK-receptor antagonists are an effective treatment of pain in general or urinary tract disorders, such as detrusor overactivity. In order to search for therapeutic targets that could block the tachykinin system, we set forth to determine the regulatory network downstream of NK1 receptor activation. First, NK1R-dependent transcripts were determined and used to query known databases for their respective transcription regulatory elements (TREs).
An expression analysis was performed using urinary bladders isolated from sensitized wild type (WT) and NK1R-/- mice that were stimulated with saline, LPS, or antigen to provoke inflammation. Based on cDNA array results, NK1R-dependent genes were selected. PAINT software was used to query TRANSFAC database and to retrieve upstream TREs that were confirmed by electrophoretic mobility shift assays.
The regulatory network of TREs driving NK1R-dependent genes presented cRel in a central position driving 22% of all genes, followed by AP-1, NF-kappaB, v-Myb, CRE-BP1/c-Jun, USF, Pax-6, Efr-1, Egr-3, and AREB6. A comparison between NK1R-dependent and NK1R-independent genes revealed Nkx-2.5 as a unique discriminator. In the presence of NK1R, Nkx2-5 _01 was significantly correlated with 36 transcripts which included several candidates for mediating bladder development (FGF) and inflammation (PAR-3, IL-1R, IL-6, alpha-NGF, TSP2). In the absence of NK1R, the matrix Nkx2-5_02 had a predominant participation driving 8 transcripts, which includes those involved in cancer (EYA1, Trail, HSF1, and ELK-1), smooth-to-skeletal muscle trans-differentiation, and Z01, a tight-junction protein, expression. Electrophoretic mobility shift assays confirmed that, in the mouse urinary bladder, activation of NK1R by substance P (SP) induces both NKx-2.5 and NF-kappaB translocations.
This is the first report describing a role for Nkx2.5 in the urinary tract. As Nkx2.5 is the unique discriminator of NK1R-modulated inflammation, it can be imagined that in the near future, new based therapies selective for controlling Nkx2.5 activity in the urinary tract may be used in the treatment in a number of bladder disorders.
速激肽（TK），如P物质，及其在人类泌尿系统中广泛表达的神经激肽受体，代表了一个调节膀胱炎症、免疫反应和内脏超敏反应的内源性系统。越来越多的证据表明，TK系统的改变与诸如神经源性膀胱、流出道梗阻、特发性逼尿肌不稳定和间质性膀胱炎等泌尿系统疾病相关。然而，尽管在动物模型中显示出有前景的效果，但似乎尚无已发表的临床研究表明NK受体拮抗剂是治疗一般疼痛或泌尿系统疾病（如逼尿肌过度活动）的有效方法。为了寻找能够阻断速激肽系统的治疗靶点，我们着手确定NK1受体激活下游的调控网络。首先，确定NK1R依赖性转录本，并用于查询已知数据库中它们各自的转录调控元件（TRE）。
使用从致敏的野生型（WT）和NK1R - / - 小鼠分离的膀胱进行表达分析，这些小鼠用盐水、LPS或抗原刺激以引发炎症。基于cDNA阵列结果，选择NK1R依赖性基因。使用PAINT软件查询TRANSFAC数据库并检索通过电泳迁移率变动分析确认的上游TRE。
驱动NK1R依赖性基因的TRE调控网络中，cRel处于中心位置，驱动所有基因的22%，其次是AP - 1、NF - κB、v - Myb、CRE - BP1/c - Jun、USF、Pax - 6、Efr - 1、Egr - 3和AREB6。NK1R依赖性和NK1R非依赖性基因之间的比较显示Nkx - 2.5是一个独特的鉴别因子。在存在NK1R的情况下，Nkx2 - 5_01与36个转录本显著相关，其中包括几个介导膀胱发育（FGF）和炎症（PAR - 3、IL - 1R、IL - 6、α - NGF、TSP2）的候选基因。在不存在NK1R的情况下，基质Nkx2 - 5_02主要参与驱动8个转录本，其中包括那些参与癌症（EYA1、Trail、HSF1和ELK - 1）、平滑肌向骨骼肌转分化以及紧密连接蛋白Z01表达的转录本。电泳迁移率变动分析证实，在小鼠膀胱中，P物质（SP）激活NK1R会诱导NKx - 2.5和NF - κB易位。
这是第一份描述Nkx2.5在泌尿系统中作用的报告。由于Nkx2.5是NK1R调节炎症的独特鉴别因子，可以想象在不久的将来，用于控制泌尿系统中Nkx2.5活性的新型基础疗法可能会用于治疗多种膀胱疾病。
