Intracellular sources of ornithine for polyamine synthesis in endothelial cells
Intracellular sources of ornithine for polyamine synthesis in endothelial cells
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DOI：
10.1007/s00726-016-2256-6
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发表时间：
2016-10-01
期刊：
影响因子：
3.5
通讯作者：
Wu, Guoyao
中科院分区：
文献类型：
--
作者：
Li, Hui;Meininger, Cynthia J.;Wu, Guoyao
多胺对内皮细胞（EC）的增殖和血管生成是必需的。本研究使用N-ω-羟基-去甲-L-精氨酸（Nor-NOHA，一种精氨酸酶抑制剂）和加巴库林（一种鸟氨酸氨基转移酶抑制剂; OAT）鉴定了EC中用于多胺合成的鸟氨酸代谢来源。Nor-NOHA对完整EC的IC 50值为10 μ M，可抑制葡萄糖氧化酶。单独使用Nor-NOHA（0.5 mM）可抑制EC中的精氨酸酶活性98%，使精氨酸的总细胞浓度增加14%，并使鸟氨酸、腐胺和亚精胺的总细胞浓度分别降低17%、65%和74%。精氨酸和谷氨酰胺分别占EC产生的鸟氨酸的73%和26%。加巴库林（1 mM）单独降低精氨酸，鸟氨酸，腐胺，亚精胺的总细胞浓度分别为14，96，32和42%。Nor-NOHA和gabaculine的组合完全阻断了EC中的鸟氨酸产生，导致没有可检测到的细胞鸟氨酸和几乎完全耗尽的细胞腐胺和亚精胺。添加0.5 mM的鸟氨酸恢复细胞内的多胺浓度与Nor-NOHA加gabaculine处理EC，表明Nor-NOHA和gabaculine不抑制鸟氨酸脱羧酶活性。我们的研究结果表明，精氨酸酶和OAT途径是EC中鸟氨酸的唯一来源时，很少有细胞外的鸟氨酸，并有精氨酸和鸟氨酸的多胺的内皮合成的细胞内区室化。这些新发现可能对改善胎盘血管生长、伤口愈合和癌症治疗具有重要意义。
Polyamines are essential for proliferation of endothelial cells (EC) and angiogenesis. This study was conducted to identify the metabolic source(s) of ornithine for polyamine synthesis in EC, using N-omega-hydroxy-nor-l-arginine (Nor-NOHA, an inhibitor of arginase) and gabaculine (an inhibitor of ornithine aminotransferase; OAT). Nor-NOHA inhibited arginase with an IC50 value of 10 A mu M for intact EC. Nor-NOHA (0.5 mM) alone inhibited arginase activity in EC by 98 %, increased total cellular concentrations of arginine by 14 %, and decreased total cellular concentrations of ornithine, putrescine and spermidine by 17, 65 and 74 %, respectively. Arginine and glutamine contributed to 73 and 26 % of the ornithine produced by EC, respectively. Gabaculine (1 mM) alone decreased the total cellular concentrations of arginine, ornithine, putrescine, and spermidine by 14, 96, 32, and 42 %, respectively. A combination of both Nor-NOHA and gabaculine completely blocked ornithine production in EC, resulting in no detectable cellular ornithine and almost complete depletion of cellular putrescine and spermidine. Addition of 0.5 mM ornithine restored the intracellular concentrations of polyamines in EC treated with Nor-NOHA plus gabaculine, indicating that Nor-NOHA and gabaculine did not inhibit ornithine decarboxylase activity. Our results suggest that the arginase and OAT pathways are the exclusive sources of ornithine in EC when there is little extracellular ornithine and that there is intracellular compartmentalization of arginine and ornithine for endothelial synthesis of polyamines. These novel findings may have important implications for improving placental vascular growth, wound healing, and cancer therapy.