Chen Bernadette, Calvert Andrea E, Cui Hongmei, Nelin Leif D
Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, The Ohio State University College of Medicine, Columbus, USA.
Am J Physiol Lung Cell Mol Physiol. 2009 Dec;297(6):L1151-9. doi: 10.1152/ajplung.00183.2009. Epub 2009 Oct 2.
Vascular remodeling and smooth muscle cell proliferation are hallmark pathogenic features of pulmonary artery hypertension (PAH). Alterations in the metabolism of l-arginine via arginase and nitric oxide synthase play a critical role in the endothelial dysfunction seen in PAH. l-arginine metabolism by arginase produces l-ornithine and urea. l-ornithine is a precursor for polyamine and proline synthesis, ultimately leading to an increase in cellular proliferation. Given the integral role of the smooth muscle layer in the pathogenesis of hypoxia-induced PAH, we hypothesized that hypoxia would increase cellular proliferation via arginase induction in human pulmonary artery smooth muscle cells (hPASMC). We found that arginase II mRNA and protein expression were significantly increased in cultured hPASMC exposed to 1% O(2) for 24 and 48 h, which coincided with an increase in arginase activity at 48 h. There were no hypoxia-induced changes in levels of arginase I mRNA or protein in cultured hPASMC. Exposure to hypoxia resulted in more than one and a half times as many viable cells after 120 h than normoxic exposure. The addition of the arginase inhibitor, S-(2-boronoethyl)-l-cysteine, completely prevented both the hypoxia-induced increase in arginase activity and proliferation in hPASMC. Furthermore, transfection of small interfering RNA (siRNA) targeting arginase II in hPASMC resulted in knockdown of arginase II protein levels and complete prevention of the hypoxia-induced cellular proliferation. These data support our hypothesis that hypoxia increases proliferation of hPASMC through the induction of arginase II.
血管重塑和平滑肌细胞增殖是肺动脉高压（PAH）的标志性致病特征。通过精氨酸酶和一氧化氮合酶对L-精氨酸代谢的改变在PAH中出现的内皮功能障碍中起关键作用。精氨酸酶对L-精氨酸的代谢产生L-鸟氨酸和尿素。L-鸟氨酸是多胺和脯氨酸合成的前体，最终导致细胞增殖增加。鉴于平滑肌层在缺氧诱导的PAH发病机制中的重要作用，我们推测缺氧会通过诱导人肺动脉平滑肌细胞（hPASMC）中的精氨酸酶来增加细胞增殖。我们发现，暴露于1%氧气24小时和48小时的培养hPASMC中，精氨酸酶II的mRNA和蛋白表达显著增加，这与48小时时精氨酸酶活性的增加相一致。培养的hPASMC中，缺氧并未引起精氨酸酶I的mRNA或蛋白水平的变化。暴露于缺氧环境120小时后，存活细胞比常氧暴露时多出一倍半以上。添加精氨酸酶抑制剂S-（2-硼乙基）-L-半胱氨酸，完全阻止了缺氧诱导的hPASMC中精氨酸酶活性增加和细胞增殖。此外，在hPASMC中转染靶向精氨酸酶II的小干扰RNA（siRNA），导致精氨酸酶II蛋白水平降低，并完全阻止了缺氧诱导的细胞增殖。这些数据支持了我们的假设，即缺氧通过诱导精氨酸酶II增加hPASMC的增殖。
