title: Molecular regulation of the expression of leptin by hypoxia in human coronary artery smooth muscle cells.
abstract: BACKGROUND
  Leptin, produced mainly by white adipose tissue, is a hormone that promotes vascular smooth muscle cell (VSMC) migration and proliferation, a process involved in the pathophysiology of atherosclerosis. Leptin expression in human coronary artery smooth cell (HCASMC) is induced by hypoxia. However, our understanding of the process of atherosclerosis in HCASMC is only emerging. Since the mechanisms by which hypoxia regulates leptin in HCASMC are as yet unknown, this study aims to investigate the mechanics of molecular regulation of leptin expression in HCASMC under hypoxia. We subjected cultured HCASMCs to hypoxia for varying periods of time. Through use of different signal pathway inhibitors, we were able to sort out and identify the pathway through which hypoxia-induced leptin expression occurs.
  
  
  RESULTS
  Leptin mRNA and protein levels increased after 2.5% hypoxia for 2-to-4 hours, with earlier expression of angiotensin II (AngII) and reactive oxygen species (ROS). The addition before hypoxia of the c-Jun N-terminal kinase (JNK) pathway inhibitor (SP600125), JNK small interfering RNA (siRNA), AngII receptor blockers (ARBs; losartan), or N-acetyl-L-cysteine (NAC, an ROS scavenger), had the effect of inhibiting JNK phosphorylation and leptin expression. Gel shift assay and luciferase promoter study showed that leptin/activator protein 1 (AP-1) binding and transcriptional activity to the leptin promoter increased after hypoxia, and SP600125, JNK siRNA, losartan, and NAC abolished the binding and transcriptional activity induced by hypoxia. The use of SP600125, JNK siRNA, losartan, and NAC effectively inhibited the binding and transcriptional activity induced by hypoxia. Migration and proliferation, ROS generation, and the presence of leptin in the nuclei of HCASMCs also increased under hypoxia.
  
  
  CONCLUSIONS
  Hypoxia in HCASMCs increases leptin expression through the induction of AngII, ROS, and the JNK pathway to enhance atherosclerosis in HCASMCs.
authors.affiliation: School of Medicine, College of Medicine, Fu-Jen Catholic University, New Taipei, Taiwan. m004401@ms.skh.org.tw.|Division of Cardiology, Shin-Kong Wu Ho-Su Memorial Hospital, 95 Wen- Chang Road, Taipei, Taiwan. m004401@ms.skh.org.tw.
authors.forename: Chiung-Zuan
authors.initials: CZ
authors.lastname: Chiu
authors.affiliation: School of Medicine, College of Medicine, Fu-Jen Catholic University, New Taipei, Taiwan. T002558@ms.skh.org.twl.
authors.forename: Bao-Wei
authors.initials: BW
authors.lastname: Wang
authors.affiliation: Division of Cardiology, Shin-Kong Wu Ho-Su Memorial Hospital, 95 Wen- Chang Road, Taipei, Taiwan. m004401@yahoo.com.tw.|Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical, University, Taipei, Taiwan. m004401@yahoo.com.tw.
authors.forename: Kou-Gi
authors.initials: KG
authors.lastname: Shyu
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D003331:Coronary Vessels / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D020738:Leptin / Q000235:genetics* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D020738:Leptin; D017382:Reactive Oxygen Species; D000804:Angiotensin II