title: Hsp20 functions as a novel cardiokine in promoting angiogenesis via activation of VEGFR2.
abstract: Heat shock proteins (Hsps) are well appreciated as intrinsic protectors of cardiomyocytes against numerous stresses. Recent studies have indicated that Hsp20 (HspB6), a small heat shock protein, was increased in blood from cardiomyopathic hamsters. However, the exact source of the increased circulating Hsp20 and its potential role remain obscure. In this study, we observed that the circulating Hsp20 was increased in a transgenic mouse model with cardiac-specific overexpression of Hsp20, compared with wild-type mice, suggesting its origin from cardiomyocytes. Consistently, culture media harvested from Hsp20-overexpressing cardiomyocytes by Ad.Hsp20 infection contained an increased amount of Hsp20, compared to control media. Furthermore, we identified that Hsp20 was secreted through exosomes, independent of the endoplasmic reticulum-Golgi pathway. To investigate whether extracellular Hsp20 promotes angiogenesis, we treated human umbilical vein endothelial cells (HUVECs) with recombinant human Hsp20 protein, and observed that Hsp20 dose-dependently promoted HUVEC proliferation, migration and tube formation. Moreover, a protein binding assay and immunostaining revealed an interaction between Hsp20 and VEGFR2. Accordingly, stimulatory effects of Hsp20 on HUVECs were blocked by a VEGFR2 neutralizing antibody and CBO-P11 (a VEGFR inhibitor). These in vitro data are consistent with the in vivo findings that capillary density was significantly enhanced in Hsp20-overexpressing hearts, compared to non-transgenic hearts. Collectively, our findings demonstrate that Hsp20 serves as a novel cardiokine in regulating myocardial angiogenesis through activation of the VEGFR signaling cascade.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhang
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhu
authors.forename: Evangelia G
authors.initials: EG
authors.lastname: Kranias
authors.forename: Yaoliang
authors.initials: Y
authors.lastname: Tang
authors.forename: Tianqing
authors.initials: T
authors.lastname: Peng
authors.forename: Jiang
authors.initials: J
authors.lastname: Chang
authors.forename: Guo-Chang
authors.initials: GC
authors.lastname: Fan
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D055354:Exosomes / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D050886:HSP20 Heat-Shock Proteins / Q000097:blood* / Q000494:pharmacology*; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000187:drug effects* / Q000502:physiology; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
chemical_list: D050886:HSP20 Heat-Shock Proteins; D040301:Vascular Endothelial Growth Factor Receptor-2