title: Protection of DDAH2 overexpression against homocysteine-induced impairments of DDAH/ADMA/NOS/NO pathway in endothelial cells.
abstract: OBJECTIVE
  Homocysteine-induced endothelial dysfunction favors the development of cardiovascular diseases through accumulation of endogenous nitric oxide (NO) synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA). Dimethylarginine dimethylaminohydrolase 2 (DDAH2) is the major enzyme for the degradation of ADMA in endothelial cells. The purpose of this study was to determine whether suppressed DDAH2 expression contributed to impairments of DDAH/ADMA/NOS/NO pathway induced by homocysteine in endothelial cells and whether DDAH2 overexpression could prevent endothelial cell dysfunction caused by homocysteine.
  
  
  METHODS
  Liposome-mediated transfection of endothelial cells was performed to establish the cell line of DDAH2 overexpression. After treatment of cells with 1 mmol/L homocysteine for 24 h, the transcription and expression of DDAH1 and DDAH2, DDAH and NOS activities as well as ADMA and NO concentrations were measured.
  
  
  RESULTS
  Treatment of endothelial cells with homocysteine significantly suppressed the transcription and expression of DDAH2 but not DDAH1. This suppression was associated with the declined DDAH activity, increased ADMA accumulation, inhibited NOS activity and decreased NO production in endothelial cells. DDAH2 overexpression not only resisted homocysteine-induced decline of DDAH activity, but also decreased the accumulation of endogenous ADMA, subsequently attenuated the reductions of NOS activity and NO production induced by homocysteine.
  
  
  CONCLUSIONS
  These results indicate that suppression of DDAH2 expression is a culprit for homocysteine-induced impairments of DDAH/ADMA/NOS/NO pathway in endothelial cells, and therapeutic manipulation of DDAH2 expression may be a promising strategy for preventing endothelial dysfunction and cardiovascular diseases associated with hyperhomocysteinemia.
authors.affiliation: Department of Pharmacology, Guangzhou Medical University, Guangzhou, Guangdong, PR China.
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Liu
authors.forename: Zheng
authors.initials: Z
authors.lastname: Guo
authors.forename: Mei
authors.initials: M
authors.lastname: Feng
authors.forename: Zhong-Zu
authors.initials: ZZ
authors.lastname: Wu
authors.forename: Zhi-Min
authors.initials: ZM
authors.lastname: He
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiong
mesh_terms: D000581:Amidohydrolases / Q000235:genetics* / Q000378:metabolism; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D002478:Cells, Cultured; D004727:Endothelium / Q000201:enzymology / Q000503:physiopathology; D015870:Gene Expression; D006710:Homocysteine / Q000502:physiology*; D061307:Human Umbilical Vein Endothelial Cells / Q000201:enzymology*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000201:enzymology / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D006710:Homocysteine; D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D001120:Arginine; D007770:L-Lactate Dehydrogenase; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D000581:Amidohydrolases; C059999:dimethylargininase