在人體，血管收縮素Ⅱ(Angiotensin Ⅱ，ANGⅡ) 和內皮素Endothelin-1 ( ET-1) 皆為體內促進血管收縮的重要物質。本項實驗的研究目的在探討在正常情況下或病態狀況下，ANGⅡ對ET-1表現的影響。
利用RT-PCR以及Real-time PCR的方法，觀察preproET mRNA的表現量。在human umbilical vein endothelin cells ( HUVECs )，給予ANGⅡ會刺激preproET mRNA的表現，在1小時後的表現最大；隨著劑量的增加，mRNA表現量也會隨之增加；這樣的作用是透過AT1 receptor活化，再經由phospholipase C和protein kinase C這條傳遞路徑所形成。
另外也發現ANGⅡ會刺激PPAR-g的表現；這樣的作用會被ETB receptor抑制劑的BQ 788阻斷。因此，推測是因ANGⅡ刺激了ET-1的增加，藉由ET-1再去刺激ETB receptor來活化PPAR-γ的基因表現。同時，也發現PPAR-γ的活化會去抑制內皮細胞的移行能力。當共同處理ANGⅡ和PPAR-γ拮抗劑(GW9662)到HUVECs，GW9662會增加原本ANGⅡ所刺激的細胞移行能力。由此推測，當內皮細胞的ET-1受到刺激時，會回饋性刺激PPAR-γ的表現，抑制內皮細胞移行，減少血管病變的產生。
另一方面，糖尿病患者常會伴隨高血壓的併發症，文獻指出insulin可能會經由活化protein kinase C ( PKC )來刺激ET-1的合成。在HUVECs，給予胰島素也會增加preproET mRNA的表現，在2小時後的表現最大；隨著劑量增加表現量也會隨之增加。而且，同時給予ANGⅡ和insulin時，preproET mRNA的上升會有加成的現象。
Hyperinsulinemia和hyperglycemia是糖尿病患者體內常見的症狀，於是，讓細胞處於高血糖或胰島素抗阻性的兩種環境，再給予ANGⅡ，觀察ET-1和PPAR-γ表現量的變化。結果發現，當細胞處於高血糖狀態下(25mM vs. 5.5mM正常組)，三天後再給予ANGⅡ，發現原本ANGⅡ刺激ET-1表現的時間有提前的現象；意謂著細胞對ANGⅡ敏感性有增加的結果。另外，當先將細胞處理胰島素24小時後，再給予ANGⅡ刺激，發現ANGⅡ對ET-1的作用時間有延長的的作用。此外，在高血糖狀態或長期胰島素刺激下，PPAR-γ的表現量皆會較正常組有增加的情形。另外，再給予ANGⅡ刺激，PPAR-γ的表現量也會有明顯的改變。
綜合以上的結果，ANGⅡ會透過AT1 receptor的活化，經由phospholipase C和protein kinase C刺激ET-1的表現。增加的ET-1蛋白會活化ETB receptor進而增加PPAR-γ的基因表現；在生理功能上，PPAR-γ的活化在抑制內皮細胞移行可能扮演重要的角色。

In vivo, angiotensin II (ANG II) and endothelin-1 (ET-1) are mentioned as the potent vasoconstrictive peptide. Also, ANG II has the ability to stimulate ET-1 production. The aim of this study is to examine the effect of ANG II and insulin on ET-1 gene expression in normal or pathological conditions.
Cultured human umbilical vein endothelial cells were incubated with ANG II. Total RNA was extracted and ET-1 mRNA expression was assessed by RT-PCR. ANG II can increase preproendothelin-1 mRNA in a dose- and time-dependent manner. The presence of valsartan (an ANG II receptor type I antagonist), U733122 (the phospholipase C inhibitor) and GF109203X (the protein kinase C inhibitor) abolished this effect of ANG II. Thus, ANG II stimulates ET-1 gene expression through activation of AT1 receptor via PLC-PKC pathway.
On the other hand, ANG II also increased the peroxisome proliferator-activated receptor-g ( PPAR-g ) mRNA in a dose- and time-dependent manner. The addition of BQ788, ETB receptor antagonist, inhibited this action of ANG II indicating that increase of ET-1 protein is mediated ETB receptor to stimulate PPAR-g expression. In order to understand main function of the increased PPAR-g expression, we investigated the ability of endothelial cell migration. Treatment with PPAR-g antagonist GW9662 significantly increased the migration induced by ANG II.
Type II diabetes and hypertension are two pathologies which are frequently associated in adults , especially in developed countries. Insulin resistance has an important role in the pathogenesis and evolution of type 2 diabetes. In insulin resistance, there are two marked features: hyperinsulinemia and hyperglycemia. Thus, we investigated the effects of hyperinsulinemia and hyperglycemia on ET-1 and PPAR-g gene expression. In hyperglycemia condition, the onset of ET-1 gene expression stimulated by ANG II is accelerated. On the other hand, in hyperinsulinemia condition, the time of ET-1 gene expression stimulated by ANG II is elongated. In two conditions, PPAR-g gene expression is significantly increased regardless the stimulation with ANG II or not.
The results indicated that ANG II stimulates ET-1 gene expression via AT1 receptor-PLC-PKC signaling pathway. The increased ET-1 activates PPAR-g gene expression via ETB receptor. The increased PPAR-g expression inhibits the migration induced by ANG II. The ET-1 expression in response to ANG II is obviously increased in HUVEC under hyperinsulinemia and hyperglycemia.

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