title: Tongxinluo Reverses the Hypoxia-suppressed Claudin-9 in Cardiac Microvascular Endothelial Cells.
abstract: BACKGROUND
  Claudin-5, claudin-9, and claudin-11 are expressed in endothelial cells to constitute tight junctions, and their deficiency may lead to hyperpermeability, which is the initiating process and pathological basis of cardiovascular disease. Although tongxinluo (TXL) has satisfactory antianginal effects, whether and how it modulates claudin-5, claudin-9, and claudin-11 in hypoxia-stimulated human cardiac microvascular endothelial cells (HCMECs) have not been reported.
  
  
  METHODS
  In this study, HCMECs were stimulated with CoCl2to mimic hypoxia and treated with TXL. First, the messenger RNA (mRNA) expression of claudin-5, claudin-9, and claudin-11 was confirmed. Then, the protein content and distribution of claudin-9, as well as cell morphological changes were evaluated after TXL treatment. Furthermore, the distribution and content histone H3K9 acetylation (H3K9ac) in the claudin-9 gene promoter, which guarantees transcriptional activation, were examined to explore the underlying mechanism, by which TXL up-regulates claudin-9 in hypoxia-stimulated HCMECs.
  
  
  RESULTS
  We found that hypoxia-suppressed claudin-9 gene expression in HCMECs (F = 7.244; P = 0.011) and the hypoxia-suppressed claudin-9 could be reversed by TXL (F = 61.911; P = 0.000), which was verified by its protein content changes (F = 29.142; P = 0.000). Moreover, high-dose TXL promoted the cytomembrane localization of claudin-9 in hypoxia-stimulated HCMECs, with attenuation of cell injury. Furthermore, high-dose TXL elevated the hypoxia-inhibited H3K9ac in the claudin-9 gene promoter (F = 37.766; P = 0.000), activating claudin-9 transcription.
  
  
  CONCLUSIONS
  The results manifested that TXL reversed the hypoxia-suppressed claudin-9 by elevating H3K9ac in its gene promoter, playing protective roles in HCMECs.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.forename: Xiu-Juan
authors.initials: XJ
authors.lastname: Wang
authors.forename: Yan-Ning
authors.initials: YN
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Biochemistry, Hebei Key Laboratory of Medical Biotechnology, Hebei Medical University, Shijiazhuang, Hebei 050017, China.
authors.forename: Jin-Sheng
authors.initials: JS
authors.lastname: Qi
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
mesh_terms: D015687:Cell Hypoxia; D002478:Cells, Cultured; D057167:Claudins / Q000032:analysis / Q000235:genetics*; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic
chemical_list: C524757:CLDN9 protein, human; D057167:Claudins; D004365:Drugs, Chinese Herbal; D006657:Histones; C513941:tongxinluo