title: Effect of mini-tyrosyl-tRNA synthetase on ischemic angiogenesis, leukocyte recruitment, and vascular permeability.
abstract: Mini-tyrosyl-tRNA synthetase (mini-TyrRS), the N-terminal domain of tyrosyl-tRNA synthetase, is a recently identified protein released by endothelial cells that exhibits angiogenic and leukocyte chemoattractant, ELR-motif (Glu-Leu-Arg)-dependent activities in vitro. We sought to determine whether exogenous mini-TyrRS exerts these and other cytokine-like actions in physiological and pathological settings in vivo. High-dose mini-TyrRS (600 microg.kg(-1).day(-1)) augmented while low-dose mini-TyrRS (3 microg.kg(-1).day(-1)), unexpectedly, inhibited angiogenesis in the ischemic mouse ear. Enhanced angiogenesis was associated with increased CD45- and CD4-positive leukocyte accumulation. Mini-TyrRS also had biphasic actions on both basal and mustard oil-evoked and VEGF-evoked leakage of Evan's blue dye-albumin in nonischemic ear and in endothelial cell monolayers, that is, low-dose inhibited and high-dose augmented leakage. Mutation of the ELR motif of mini-TyrRS abolished the above activities. Mini-TyrRS was reduced (immunoblot) in extracts of ischemic calf muscle and in thoracic aorta explants exposed to hypoxia or VEGF. Inhibition of VEGF with a soluble Flt1 "trap" protein abolished this hypoxic-induced reduction in mini-TyrRS in aorta explants. These data show that mini-TyrRS has dose-dependent biphasic effects on ischemic angiogenesis and vascular permeability in vivo, that is, antiangiogenic and antipermeability activities at low concentration and proangiogenic, propermeability activities at high concentrations.
authors.affiliation: Dept. of Cell and Molecular Physiology, 6309 MBRB, Univ. of North Carolina, Chapel Hill, NC 27599-7545, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Cheng
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.forename: Xianglei
authors.initials: X
authors.lastname: Yang
authors.forename: Eleni
authors.initials: E
authors.lastname: Tzima
authors.forename: Karla L
authors.initials: KL
authors.lastname: Ewalt
authors.forename: Paul
authors.initials: P
authors.lastname: Schimmel
authors.forename: James E
authors.initials: JE
authors.lastname: Faber