Odense University Hospital and University of Southern Denmark, Institute for Molecular Medicine, Cardiovascular and Renal Research, Institute of Clinical Research, Winsløwparken 21.3, DK-5000 Odense C, Denmark.
Hypertension. 2011 Aug;58(2):317-24. doi: 10.1161/HYPERTENSIONAHA.111.173690. Epub 2011 Jun 20.
Hypertension is a common complication in hemodialysis patients during erythropoietin (EPO) treatment. The underlying mechanisms of EPO-induced hypertension still remain to be determined. Increased transient receptor potential canonical (TRPC) channels have been associated with hypertension. Now, TRPC gene expression was investigated using quantitative real-time RT-PCR and immunoblotting in cultured human endothelial cells and in monocytes from hemodialysis patients. EPO dose-dependently increased TRPC5 mRNA in endothelial cells. EPO increased TRPC5 mRNA stability, that is, EPO prolonged the half-life period for TRPC5 mRNA from 16 hours (control) to 24 hours (P<0.05). The poly(A) tail length was measured by rapid amplification of cDNA ends-poly(A) test. Increased TRPC5 mRNA stability was attributed to longer 3' poly(A) tail lengths after EPO administration. EPO also significantly increased TRPC5 channel protein abundance by 70% (P<0.05). Whole-cell patch clamp showed that angiotensin II-induced, TRPC5-mediated currents were dramatically increased in endothelial cells treated with EPO. Fluorescent dye techniques confirmed that increased calcium influx after EPO treatment was abolished after TRPC5 knockdown (P<0.05). EPO also significantly increased intracellular reactive oxygen species production. Knockdown of TRPC5 alleviated EPO-induced reactive oxygen species generation in endothelial cells (P<0.05). In vivo, EPO-treated hemodialysis patients showed significantly increased amounts of TRPC5 mRNA in monocytes compared with EPO-free hemodialysis patients (6.0±2.4 [n=12] versus 1.0±0.5 [n=9]; P<0.01). Patients undergoing EPO treatment also showed significantly elevated systolic blood pressure (160±7 versus 139±6 mm Hg; P<0.05). Our findings suggest that upregulated functional TRPC5 gene may be one cause of EPO-induced hypertension in patients with chronic kidney disease.
高血压是接受促红细胞生成素（EPO）治疗的血液透析患者的常见并发症。EPO 引起的高血压的潜在机制仍有待确定。已经发现瞬时受体电位经典（TRPC）通道增加与高血压有关。现在，使用定量实时 RT-PCR 和免疫印迹法在培养的人内皮细胞和血液透析患者的单核细胞中研究了 TRPC 基因表达。EPO 剂量依赖性地增加了内皮细胞中的 TRPC5 mRNA。EPO 增加了 TRPC5 mRNA 的稳定性，即 EPO 将 TRPC5 mRNA 的半衰期从 16 小时（对照）延长至 24 小时（P<0.05）。通过快速扩增 cDNA 末端-多（A）测试测量多（A）尾的长度。EPO 给药后，TRPC5 mRNA 的稳定性增加归因于更长的 3'多（A）尾长度。EPO 还使 TRPC5 通道蛋白丰度增加了 70%（P<0.05）。全细胞膜片钳显示，血管紧张素 II 诱导的，EPO 处理后内皮细胞中 TRPC5 介导的电流显著增加。荧光染料技术证实，EPO 处理后钙内流增加在 TRPC5 敲低后被消除（P<0.05）。EPO 还显著增加了细胞内活性氧物质的产生。TRPC5 敲低减轻了 EPO 诱导的内皮细胞中活性氧物质的产生（P<0.05）。在体内，与 EPO 无治疗的血液透析患者相比，接受 EPO 治疗的血液透析患者的单核细胞中 TRPC5 mRNA 的量显著增加（6.0±2.4 [n=12] 与 1.0±0.5 [n=9]；P<0.01）。接受 EPO 治疗的患者的收缩压也显著升高（160±7 与 139±6 mmHg；P<0.05）。我们的研究结果表明，上调的功能性 TRPC5 基因可能是慢性肾脏病患者 EPO 诱导的高血压的一个原因。
