title: Erythropoietin increases expression and function of transient receptor potential canonical 5 channels.
abstract: 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.
authors.affiliation: 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.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Xu
authors.forename: Florian
authors.initials: F
authors.lastname: Thilo
authors.forename: Ulla G
authors.initials: UG
authors.lastname: Friis
authors.forename: Boye L
authors.initials: BL
authors.lastname: Jensen
authors.forename: Alexandra
authors.initials: A
authors.lastname: Scholze
authors.forename: Junhua
authors.initials: J
authors.lastname: Zheng
authors.forename: Martin
authors.initials: M
authors.lastname: Tepel
mesh_terms: D000368:Aged; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D004921:Erythropoietin / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D050052:TRPC Cation Channels; C491780:TRPC5 protein, human; D004921:Erythropoietin