Yamada Masahiro, Kushibiki Motoi, Osanai Tomohiro, Tomita Hirofumi, Okumura Ken
Department of Cardiology, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan.
Cardiovasc Res. 2008 Jul 1;79(1):169-78. doi: 10.1093/cvr/cvn064. Epub 2008 Mar 7.
We recently demonstrated that aldosterone induces a non-genomic vasoconstrictor effect on rat coronary arterioles and that this effect was blocked by angiotensin II type 1 receptor (AT1) blockers. Intracellular transglutaminase enhances AT1 signalling by cross-linking AT1 homodimers. The purpose of this study was to confirm the AT1-dependency of the vasoconstrictor effect of aldosterone using AT1a knockout (AT1aKO) mice and to investigate the role of intracellular transglutaminase and AT1 dimerization in this effect.
The mesenteric arterioles (60-160 microm) were isolated from C57BL/6J (wild-type, WT) and AT1aKO mice, and the internal diameter was measured by video microscopy. Aldosterone (10(-13) to 10(-6) M), but not hydrocortisone, produced a dose-dependent vasoconstriction in WT mice; the maximal diameter change was -8.6 +/- 0.3% from the baseline (P < 0.001). This vasoconstrictor effect was unaffected by the mineralocorticoid receptor antagonist spironolactone or eplerenone, the AT2 antagonist PD123319, the glucocorticoid receptor antagonist RU486, or endothelium denudation. Aldosterone's vasoconstrictor effect was negligible in AT1aKO mice. The AT1 blockers valsartan or candesartan suppressed aldosterone-induced vasoconstriction in WT mice. The transglutaminase inhibitors cystamine and monodansyl cadaverine also suppressed the vasoconstrictor effect of aldosterone, without affecting the vasoconstrictor effect of angiotensin II in WT mice. AT1 dimer protein levels were increased in WT mesenteric arterioles treated with 10(-7) M aldosterone, and the transglutaminase inhibitor and AT1 blocker blocked this aldosterone-induced formation of AT1 dimer. Treatment with 10(-7) M aldosterone for 10 min increased the transglutaminase activity by 2.5 +/- 0.2-fold in cultured vascular smooth muscle cells and by 1.2 +/- 0.1-fold in the mesenteric arterioles. These increases were abolished by transglutaminase inhibitors.
Aldosterone produces a non-genomic, endothelium-independent vasoconstrictor effect by enhancing intracellular transglutaminase activity and presumably inducing AT1 dimer formation in mesenteric arterioles.
我们最近证明，醛固酮对大鼠冠状动脉小动脉具有非基因组血管收缩作用，且该作用被1型血管紧张素II受体（AT1）阻滞剂阻断。细胞内转谷氨酰胺酶通过交联AT1同源二聚体增强AT1信号传导。本研究的目的是使用AT1a基因敲除（AT1aKO）小鼠证实醛固酮血管收缩作用对AT1的依赖性，并研究细胞内转谷氨酰胺酶和AT1二聚化在此作用中的作用。
从C57BL/6J（野生型，WT）和AT1aKO小鼠分离肠系膜小动脉（60 - 160微米），通过视频显微镜测量内径。醛固酮（10^(-13)至10^(-6) M）而非氢化可的松在WT小鼠中产生剂量依赖性血管收缩；最大直径变化相对于基线为-8.6±0.3%（P < 0.001）。这种血管收缩作用不受盐皮质激素受体拮抗剂螺内酯或依普利酮、AT2拮抗剂PD123319、糖皮质激素受体拮抗剂RU486或内皮剥脱的影响。醛固酮在AT1aKO小鼠中的血管收缩作用可忽略不计。AT1阻滞剂缬沙坦或坎地沙坦抑制WT小鼠中醛固酮诱导的血管收缩。转谷氨酰胺酶抑制剂胱胺和单丹磺酰尸胺也抑制醛固酮的血管收缩作用，而不影响WT小鼠中血管紧张素II的血管收缩作用。用10^(-7) M醛固酮处理的WT肠系膜小动脉中AT1二聚体蛋白水平升高，转谷氨酰胺酶抑制剂和AT1阻滞剂阻断这种醛固酮诱导的AT1二聚体形成。用10^(-7) M醛固酮处理10分钟使培养血管平滑肌细胞中转谷氨酰胺酶活性增加2.5±0.2倍，使肠系膜小动脉中转谷氨酰胺酶活性增加1.2±0.1倍。这些增加被转谷氨酰胺酶抑制剂消除。
醛固酮通过增强细胞内转谷氨酰胺酶活性并可能诱导肠系膜小动脉中AT1二聚体形成，产生非基因组、不依赖内皮的血管收缩作用。
