Analysis of endothelium-targeted PRMT-overexpressed mice

内皮型一氧化氮合酶(NO)具有维持内皮功能，预防动脉粥样硬化的作用。NO由内皮型一氧化氮合酶产生。ADMA(不对称二甲基精氨酸)是一种内源性NO抑制物，在高脂血症、高血糖和慢性肾脏疾病中其水平升高。然而，ADMA合成增加对内皮功能的影响尚不清楚。ADMA由蛋白质精氨酸N-甲基转移酶(PRMT)合成。我们利用Tie-2启动子(Tie2-PRMT-TG)建立了内皮特异性表达PRMT的转基因小鼠，以研究血管内皮细胞ADMA增加的影响。我们发现，与对照组相比，血清中ADMA水平增加到3.8倍，而NO水平下降到42%。将Tie2-PRMT-TG与载脂蛋白E缺陷小鼠(ApoE-KO)杂交，得到Tie2-PRMT-TG/ApoE-KO小鼠。在西方饮食后8周，与ApoE-KO相比，Tie2-PRMT-TG/ApoE-KO显示动脉粥样硬化减轻。PRMT-TG/ApoE-KO中eNOS的1177Ser磷酸化水平降低。此外，链脲佐菌素诱导的高血糖诱导的PRMT-TG/ApoE-KO中MCP和TNFa-mRNA的合成是ApoE-KO的~3倍。因此，PRMT诱导的ADMA抑制NO以促进内皮功能障碍。

Endothelial Nitric Oxide (NO) has been shown to maintain EC function to prevent atherosclerosis. NO is produced by endothelial NO synthase. ADMA (asymmetric dimethylarginine) acts as an endogenous NO inhibitor and its level increases in hyperlipidemia, hyperglycemia, and chronic renal disease. However, the effect of increased ADMA synthesis on endothelial function was not clear. ADMA was synthesized by protein arginine N-methyltrans-ferases (PRMT). We generated the transgenic mice in which PRMT was over-expressed in endothelium-specific manner using Tie-2 promoter (Tie2-PRMT-Tg) to study the effect of increased ADMA in endothelium. We found that ADMA level in the serum increased to 3.8-fold, whereas NO level decreased to 42%, compared to the control. Tie2-PRMT-Tg were crossed with ApoE-deficient mice (ApoE-KO) to generate Tie2-PRMT-Tg/ApoE-KO mice. At 8 weeks after Western diet, the Tie2-PRMT-Tg/ApoE-KO shows attenuated atherosclerosis, compared to ApoE-KO. 1177Ser phosphorylation level of eNOS in the PRMT-Tg/ApoE-KO was decreased. Furthermore, streptoztocine-induced hyperglycemia induced synthesis of MCP and TNFa-mRNA in in PRMT-Tg/ApoE-KO was ~3 fold higher than ApoE-KO. Thus, PRMT-Induced ADMA inhibited NO to promote endothelial dysfunction.