Carrillo-Sepulveda Maria Alicia, Keen Henry L, Davis Deborah R, Grobe Justin L, Sigmund Curt D
Department of Pharmacology and Roy J. and A. Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America.
PLoS One. 2014 Aug 14;9(8):e103786. doi: 10.1371/journal.pone.0103786. eCollection 2014.
Peroxisome proliferator activated receptor γ (PPARγ) has been reported to play a protective role in the vasculature; however, the underlying mechanisms involved are not entirely known. We previously showed that vascular smooth muscle-specific overexpression of a dominant negative human PPARγ mutation in mice (S-P467L) leads to enhanced myogenic tone and increased angiotensin-II-dependent vasoconstriction. S-P467L mice also exhibit increased arterial blood pressure. Here we tested the hypotheses that a) mesenteric smooth muscle cells isolated from S-P467L mice exhibit enhanced angiotensin-II AT1 receptor signaling, and b) the increased arterial pressure of S-P467L mice is angiotensin-II AT1 receptor dependent. Phosphorylation of mitogen-activated protein/extracellular signal-regulated kinase (ERK1/2) was robustly increased in mesenteric artery smooth muscle cell cultures from S-P467L in response to angiotensin-II. The increase in ERK1/2 activation by angiotensin-II was blocked by losartan, a blocker of AT1 receptors. Angiotensin-II-induced ERK1/2 activation was also blocked by Tempol, a scavenger of reactive oxygen species, and correlated with increased Nox4 protein expression. To investigate whether endogenous renin-angiotensin system activity contributes to the elevated arterial pressure in S-P467L, non-transgenic and S-P467L mice were treated with the AT1 receptor blocker, losartan (30 mg/kg per day), for 14-days and arterial pressure was assessed by radiotelemetry. At baseline S-P467L mice showed a significant increase of systolic arterial pressure (142.0 ± 10.2 vs 129.1 ± 3.0 mmHg, p<0.05). Treatment with losartan lowered systolic arterial pressure in S-P467L (132.2 ± 6.9 mmHg) to a level similar to untreated non-transgenic mice. Losartan also lowered arterial pressure in non-transgenic (113.0 ± 3.9 mmHg) mice, such that there was no difference in the losartan-induced depressor response between groups (-13.53 ± 1.39 in S-P467L vs -16.16 ± 3.14 mmHg in non-transgenic). Our results suggest that interference with PPARγ in smooth muscle: a) causes enhanced angiotensin-II AT1 receptor-mediated ERK1/2 activation in resistance vessels, b) and may elevate arterial pressure through both angiotensin-II AT1 receptor-dependent and -independent mechanisms.
据报道，过氧化物酶体增殖物激活受体γ（PPARγ）在脉管系统中发挥保护作用；然而，其潜在机制尚不完全清楚。我们之前发现，在小鼠中血管平滑肌特异性过表达显性负性人PPARγ突变体（S-P467L）会导致肌源性张力增强以及血管紧张素II依赖性血管收缩增加。S-P467L小鼠还表现出动脉血压升高。在此，我们检验了以下假设：a）从S-P467L小鼠分离的肠系膜平滑肌细胞表现出增强的血管紧张素II AT1受体信号传导，以及b）S-P467L小鼠动脉血压升高是血管紧张素II AT1受体依赖性的。在来自S-P467L小鼠的肠系膜动脉平滑肌细胞培养物中，丝裂原活化蛋白/细胞外信号调节激酶（ERK1/2）的磷酸化在血管紧张素II刺激下显著增加。血管紧张素II引起的ERK1/2激活被AT1受体阻滞剂氯沙坦阻断。血管紧张素II诱导的ERK1/2激活也被活性氧清除剂Tempol阻断，并且与Nox4蛋白表达增加相关。为了研究内源性肾素-血管紧张素系统活性是否导致S-P467L小鼠动脉血压升高，非转基因和S-P / 467L小鼠用AT1受体阻滞剂氯沙坦（每天每千克体重30毫克）治疗14天，并通过无线电遥测评估动脉血压。在基线时，S-P467L小鼠的收缩压显著升高（142.0±10.2对129.1±3.0 mmHg，p<0.05）。氯沙坦治疗使S-P467L小鼠的收缩压降低至（132.2±6.9 mmHg）与未治疗的非转基因小鼠相似的水平。氯沙坦也降低了非转基因小鼠的动脉血压（113. / 0±3.9 mmHg），使得两组之间氯沙坦诱导的降压反应没有差异（S-P467L组为-13.53±1.39，非转基因组为-16.16±3.14 mmHg）。我们的结果表明，平滑肌中PPARγ的干扰：a）导致阻力血管中血管紧张素II AT1受体介导的ERK / 2激活增强，b）并且可能通过血管紧张素II AT1受体依赖性和非依赖性机制升高动脉血压。
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