title: miR-21 contributes to renal protection by targeting prolyl hydroxylase domain protein 2 in delayed ischaemic preconditioning.
abstract: OBJECTIVE
  Upregulation of miR-21 in renal ischaemic preconditioning (IPC) was associated with increased hypoxia inducible factor (HIF)-1α expression. Hypoxic induction of HIF-1α is mediated by inhibition of prolyl hydroxylase domain protein 2 (PHD2) .We hypothesized that miR-21 regulated HIF-1α by targeting PHD2 in the renal IPC.
  
  
  METHODS
  Luciferase reporter assay examined if miR-21 target the 3'-untranslated region of PHD2. In vitro, human proximal tubular cell line (HK-2) was incubated in hypoxia or hypoxia/ reoxygenation condition. Kidneys of Mice were respectively subjected to ischaemia/reperfusion injury (IRI) and IPC. Locked nucleic acid (LNA) modified anti-miR-21 was used to knockdown miR-21. Serum creatinine and histological changes estimated the renal injury. Levels of HIF-1α, PHD2, VEGF and miR-21 were examined by western blot or real-time PCR.
  
  
  RESULTS
  miR-21 targeting of PHD2 was confirmed by 3'-untranslated region reporter assay. miR-21 was significantly upregulated by hypoxia/reoxygenation in HK-2 cell, while PHD2 protein level decreased significantly. LNA anti-miR-21 significantly repressed miR-21 levels and increased the abundance of PHD2. In vivo, IPC upregulated miR-21 expression 24 h after the second ischaemia, while PHD2 expression decreased significantly with upregulation of HIF-1α protein and VEGF mRNA. MiR-21 induced by delayed IPC was effectively inhibited by the LNA anti-miR-21. With downregulation of miR-21, the protection of delayed IPC was attenuated and PHD2 protein was increased. Furthermore, upregulation of HIF-1α and VEGF were abolished after the LNA anti-miR-21 treatment.
  
  
  CONCLUSIONS
  miR-21 could protect kidney against IRI via HIF-1α by inhibiting its target PHD2.The study suggested a new relationship between miR-21 and HIF-1α.
authors.affiliation: Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.|Shanghai Institute of Kidney Disease and Dialysis, Shanghai, China.|Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Jiao
authors.affiliation: Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.|Shanghai Institute of Kidney Disease and Dialysis, Shanghai, China.|Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China.
authors.forename: Xialian
authors.initials: X
authors.lastname: Xu
authors.affiliation: Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.|Shanghai Institute of Kidney Disease and Dialysis, Shanghai, China.|Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Physiology and Center of Systems Molecular Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Mingyu
authors.initials: M
authors.lastname: Liang
authors.affiliation: Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Teng
authors.affiliation: Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.|Shanghai Institute of Kidney Disease and Dialysis, Shanghai, China.|Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Ding
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001665:Binding Sites; D015687:Cell Hypoxia; D002460:Cell Line; D004195:Disease Models, Animal; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases / Q000235:genetics / Q000378:metabolism*; D019194:Ischemic Preconditioning / Q000379:methods*; D007674:Kidney Diseases / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000517:prevention & control*; D007687:Kidney Tubules, Proximal / Q000201:enzymology* / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D015427:Reperfusion Injury / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000517:prevention & control*; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D035683:MicroRNAs; D042461:Vascular Endothelial Growth Factor A; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; C524940:MIRN21 microRNA, human; C467480:vascular endothelial growth factor A, mouse; C490190:EGLN1 protein, human; C490189:Egln1 protein, mouse; C531950:MIRN21 microRNA, mouse
keywords: MiR-21; hypoxia-inducible factor-1α; ischaemic preconditioning; prolyl hydroxylase domain 2; renal ischaemia-reperfusion injury