Sakai Koji, Agassandian Khristofor, Morimoto Satoshi, Sinnayah Puspha, Cassell Martin D, Davisson Robin L, Sigmund Curt D
Department of Internal Medicine, Department of Anatomy and Cell Biology, and Center on Functional Genomics of Hypertension, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
J Clin Invest. 2007 Apr;117(4):1088-95. doi: 10.1172/JCI31242.
The mechanism controlling cell-specific Ang II production in the brain remains unclear despite evidence supporting neuron-specific renin and glial- and neuronal-specific angiotensinogen (AGT) expression. We generated double-transgenic mice expressing human renin (hREN) from a neuron-specific promoter and human AGT (hAGT) from its own promoter (SRA mice) to emulate this expression. SRA mice exhibited an increase in water and salt intake and urinary volume, which were significantly reduced after chronic intracerebroventricular delivery of losartan. Ang II-like immunoreactivity was markedly increased in the subfornical organ (SFO). To further evaluate the physiological importance of de novo Ang II production specifically in the SFO, we utilized a transgenic mouse model expressing a floxed version of hAGT (hAGT(flox)), so that deletions could be induced with Cre recombinase. We targeted SFO-specific ablation of hAGT(flox) by microinjection of an adenovirus encoding Cre recombinase (AdCre). SRA(flox) mice exhibited a marked increase in drinking at baseline and a significant decrease in water intake after administration of AdCre/adenovirus encoding enhanced GFP (AdCre/AdEGFP), but not after administration of AdEGFP alone. This decrease only occurred when Cre recombinase correctly targeted the SFO and correlated with a loss of hAGT and angiotensin peptide immunostaining in the SFO. These data provide strong genetic evidence implicating de novo synthesis of Ang II in the SFO as an integral player in fluid homeostasis.
尽管有证据支持神经元特异性肾素以及胶质细胞和神经元特异性血管紧张素原（AGT）的表达，但大脑中控制细胞特异性血管紧张素II生成的机制仍不清楚。我们构建了双转基因小鼠，其从神经元特异性启动子表达人肾素（hREN），并从其自身启动子表达人AGT（hAGT）（SRA小鼠）以模拟这种表达。SRA小鼠表现出饮水和盐摄入量以及尿量增加，在慢性脑室内给予氯沙坦后这些指标显著降低。穹窿下器官（SFO）中的血管紧张素II样免疫反应性明显增加。为了进一步评估SFO中从头合成血管紧张素II的生理重要性，我们利用了一种表达hAGT（hAGT(flox)）的转基因小鼠模型，这样可以用Cre重组酶诱导缺失。我们通过显微注射编码Cre重组酶的腺病毒（AdCre）靶向SFO特异性切除hAGT(flox)。SRA(flox)小鼠在基线时饮水显著增加，在给予AdCre/编码增强型绿色荧光蛋白的腺病毒（AdCre/AdEGFP）后水摄入量显著减少，但单独给予AdEGFP后没有这种现象。这种减少仅在Cre重组酶正确靶向SFO时发生，并且与SFO中hAGT和血管紧张素肽免疫染色的丧失相关。这些数据提供了强有力的遗传学证据，表明SFO中血管紧张素II的从头合成是体液稳态中的一个重要因素。
