title: Shear stress inhibits homocysteine-induced stromal cell-derived factor-1 expression in endothelial cells.
abstract: BACKGROUND
  Hyperhomocysteinemia contributes to vascular dysfunction and risks of cardiovascular diseases. Stromal cell-derived factor (SDF)-1, a chemokine expressed by endothelial cells (ECs), is highly expressed in advanced atherosclerotic lesions. The interplays among homocysteine, chemokines, and shear stress in regulating vascular endothelial function are not clearly understood.
  
  
  OBJECTIVE
  To investigate the mechanisms for modulations of EC SDF-1 expression by homocysteine and shear stress.
  
  
  RESULTS
  Homocysteine stimulation induced dose- and time-dependent SDF-1 expression and phosphorylation of mitogen-activated protein kinases extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. By using specific inhibitors, small interfering (si)RNA, and dominant negative mutants, we demonstrated that activation of JNK pathway is critical for the homocysteine-induced SDF-1 expression. Transcription factor ELISA and chromatin immunoprecipitation assays showed that homocysteine increased Sp1- and AP-1-DNA binding activities in ECs. Inhibition of Sp1 and AP-1 activations by specific siRNA blocked the homocysteine-induced SDF-1 promoter activity and expression. Preshearing of ECs for 1 to 4 hours at 20 dyn/cm2 inhibited the homocysteine-induced JNK phosphorylation, Sp1 and AP-1 activation, and SDF-1 expression. The homocysteine-induced SDF-1 expression was suppressed by NO donor. Inhibitor or siRNA for endothelial NO synthase abolished the shear inhibition of SDF-1 expression.
  
  
  CONCLUSIONS
  Our findings serve to elucidate the molecular mechanisms underlying the homocysteine induction of SDF-1 expression in ECs and the shear stress protection against this induction.
authors.affiliation: Department of Cardiology, St Martin De Porres Hospital, Chiayi, Taiwan.
authors.forename: Mao-Lin
authors.initials: ML
authors.lastname: Sung
authors.forename: Chia-Ching
authors.initials: CC
authors.lastname: Wu
authors.forename: Hsin-I
authors.initials: HI
authors.lastname: Chang
authors.forename: Chia-Kuang
authors.initials: CK
authors.lastname: Yen
authors.forename: Heng Jung
authors.initials: HJ
authors.lastname: Chen
authors.forename: Ju-Chien
authors.initials: JC
authors.lastname: Cheng
authors.forename: Shu
authors.initials: S
authors.lastname: Chien
authors.forename: Cheng-Nan
authors.initials: CN
authors.lastname: Chen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000378:metabolism / Q000473:pathology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D034741:RNA, Small Interfering; D012307:Risk Factors; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013312:Stress, Physiological; D018808:Transcription Factor AP-1 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D020030:Nitric Oxide Donors; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D006710:Homocysteine; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4