scholarly journals Arginase II is a target of miR-17-5p and regulates miR-17-5p expression in human pulmonary artery smooth muscle cells

2014 ◽  
Vol 307 (2) ◽  
pp. L197-L204 ◽  
Author(s):  
Youpeng Jin ◽  
Yi Jin ◽  
Bernadette Chen ◽  
Trent E. Tipple ◽  
Leif D. Nelin
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Viable Cell Number ◽  
Acid Product ◽  
Protein Levels ◽  
Pulmonary Artery Smooth Muscle ◽  
Arginase Ii ◽  
Human Pulmonary Artery

Vascular remodeling and smooth muscle cell proliferation are hallmark pathogenic features of pulmonary artery hypertension. MicroRNAs, endogenously expressed small noncoding RNAs, regulate gene expression at the posttranscriptional level. It has previously been shown that miR-17 overexpression in cultured human pulmonary artery smooth muscle cell (hPASMC) resulted in increased viable cell number. Previously, we have found that arginase II promotes hypoxia-induced proliferation in hPASMC. Therefore, we hypothesized that miR-17 would be upregulated by hypoxia in hPASMC and would result in greater arginase II expression. We found that levels of miR-17-5p and arginase II were significantly greater in cultured hPASMC exposed to 1% O2 for 48 h than in hPASMC exposed to 21% O2 for 48 h. Furthermore, inhibiting miR-17-5p expression decreased hypoxia-induced arginase II protein levels in hPASMC. Conversely, overexpressing miR-17-5p resulted in greater arginase II protein levels. Somewhat surprisingly, arginase II inhibition was associated with lower miR-17-5p expression in both normoxic and hypoxic hPASMC, whereas overexpressing arginase II resulted in greater miR-17-5p expression in hPASMC. These findings suggest that hypoxia-induced arginase II expression is not only regulated by miR-17-5p but also that there is a feedback loop between arginase II and miR-17-5p in hPASMC. We also found that the arginase II-mediated regulation of miR-17-5p was independent of either p53 or c- myc. We also found that l-arginine, the substrate for arginase II, and l-ornithine, the amino acid product of arginase II, were not involved in the regulation of miR-17-5p expression.

Hypoxia promotes human pulmonary artery smooth muscle cell proliferation through induction of arginase

2009 ◽  
Vol 297 (6) ◽  
pp. L1151-L1159 ◽  
Author(s):  
Bernadette Chen ◽  
Andrea E. Calvert ◽  
Hongmei Cui ◽  
Leif D. Nelin
Keyword(s):  
Cell Proliferation ◽  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Cellular Proliferation ◽  
Smooth Muscle Cell Proliferation ◽  
Pulmonary Artery Smooth Muscle ◽  
Arginase Ii ◽  
Human Pulmonary Artery

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% O2 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.

scholarly journals Hypoxia induces arginase II expression and increases viable human pulmonary artery smooth muscle cell numbers via AMPKα1 signaling

2017 ◽  
Vol 312 (4) ◽  
pp. L568-L578 ◽  
Author(s):  
Jianjing Xue ◽  
Leif D. Nelin ◽  
Bernadette Chen
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Cell Numbers ◽  
Pulmonary Artery Smooth Muscle ◽  
Arginase Ii ◽  
Sirna Knockdown ◽  
Pharmacologic Inhibition

Pulmonary artery smooth muscle cell (PASMC) proliferation is one of the hallmark features of hypoxia-induced pulmonary hypertension. With only supportive treatment options available for this life-threatening disease, treating and preventing the proliferation of PASMCs is a viable therapeutic option. A key promoter of hypoxia-induced increases in the number of viable human PASMCs is arginase II, with attenuation of viable cell numbers following pharmacologic inhibition or siRNA knockdown of the enzyme. Additionally, increased levels of arginase have been demonstrated in the pulmonary vasculature of patients with pulmonary hypertension. The signaling pathways responsible for the hypoxic induction of arginase II in PASMCs, however, remain unknown. Hypoxia is a recognized activator of AMPK, which is known to be expressed in human PASMCs (hPASMCs). Activation of AMPK by hypoxia has been shown to promote cell survival in PASMCs. In addition, pharmacologic agents targeting AMPK have been shown to attenuate chronic hypoxia-induced pulmonary hypertension in animal models. The present studies tested the hypothesis that hypoxia-induced arginase II expression in hPASMCs is mediated through AMPK signaling. We found that pharmacologic inhibitors of AMPK, as well as siRNA knockdown of AMPKα1, prevented hypoxia-induced arginase II. The hypoxia-induced increase in viable hPASMC numbers was also prevented following both pharmacologic inhibition and siRNA knockdown of AMPK. Furthermore, we demonstrate that overexpression of AMPK induced arginase II protein expression and viable cells numbers in hPASMCs.

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