Pthophysiological significance of target genes of NRSF, a new transcriptional suppressor, in congestive heart failure

醛固酮是参与心力衰竭发病机制的关键分子之一，由肾上腺皮质细胞特异性合成酶CYP 11B 2合成，其基因表达受T型钙通道Cav 3.2介导的钙内流调控。最近我们报道了神经元限制性沉默因子（Neuron restrictive silencer factor，NRSF）与神经元限制性沉默元件（Neuron restrictive silencer element，NRSE）结合，抑制含NRSE基因的转录，并参与体内外心脏胚胎基因的再诱导。过表达显性负性NRSF的小鼠表现出扩张性心肌病样心脏表型改变和致死性室性心律失常引起的心源性猝死，我们还鉴定了与NRSE序列高度同源的序列位于CYP 11B 2基因和CACNA 1H基因的转录调控区，后者编码Cav3.2的亚基。本实验研究了NRSE/NRSF系统在人肾上腺皮质细胞（H295 R）合成醛固酮中的作用。腺病毒载体介导的显性负性NRSF（AD/dnNRSF）抑制内源性NRSF功能可显著增加醛固酮分泌和CYP 11B 2 mRNA的表达。AD/dnNRSF还增加CACNA 1H mRNA的水平。Efonidipine，双重T/L型钙通道阻滞剂，抑制dnNRSF诱导的CYP 11B 2 mRNA表达和CYP 11B 2报告基因活性的结构含有突变或缺失的NRSE序列。AD/dnNRSF可抑制Ang Ⅱ和K^+诱导的CYP 11 B2 mRNA表达的增加，提示NRSE/NRSF系统调控肾上腺醛固酮合成，是心力衰竭的心外代偿机制之一。

Aldosterone, one of key molecules which are involved in pathogenesis in heart failure, is synthesized by a specific synthase, CYP11B2, and its gene expression is regulated Ca influx into via T-type calcium channel, Cav 3.2, in adrenal cortical cells. However, the molecular mechanism for aldosterone synthesis in heart failure is not fully understood.Recently we reported that Neuron restrictive silencer factor (NRSF), which binds to neuron restrictive silencer element (NRSE) to suppress transcription of NRSE-containing genes, is involved in the re-induction of a number of cardiac embryonic genes in vitro and in vivo. Mice over-expressing dominant negative NRSF show dilated cardiomyopathy-like cardiac phenotypic changes and sudden cardiac death due to fatal ventricular arrhythmia.We also identified the sequence highly homologous to NRSE sequence is located in transcriptional regulatory region of the CYP11B2 gene and CACNA1H gene, the latter of which encodes subunit of Cav3.2.Here we examined the roles of the NRSE/NRSF system in aldosterone synthesis in human adrenocortical (H295R) cells. Inhibiting endogenous NRSF function by adenovirus vector containing dominant-negative NRSF (AD/dnNRSF) markedly increased aldosterone secretion and CYP11B2 mRNA. AD/dnNRSF also increased levels of CACNA1H mRNA. Efonidipine, dual T/L-type calcium channel blocker, inhibited dnNRSF-induced CYP11B2 mRNA expression and CYP11B2 reporter gene activity from constructs containing a mutated or missing NRSE sequence. Moreover, AD/dnNRSF attenuated AngII- and K^+-induced increases in CYP11B2 mRNA levels.The present findings suggest the NRSE/NRSF system controls aldosterone synthesis in the adrenal gland, which is one of extracardiac compensatory mechanism in heart failure.