title: Piperlongumine Blocks JAK2-STAT3 to Inhibit Collagen-Induced Platelet Reactivity Independent of Reactive Oxygen Species.
abstract: BACKGROUND
  Piperlongumine (PL) is a compound isolated from the piper longum plant. It possesses anti-cancer activities through blocking the transcription factor STAT3 and by inducing reactive oxygen species (ROS) in cancer, but not normal cells. It also inhibits platelet aggregation induced by collagen, but the underlying mechanism is not known.
  
  
  OBJECTIVE
  We conducted in vitro experiments to test the hypothesis that PL regulates a non-transcriptional activity of STAT3 to specifically reduce the reactivity of human platelets to collagen.
  
  
  RESULTS
  PL dose-dependently blocked collagen-induced platelet aggregation, calcium influx, CD62p expression and thrombus formation on collagen with a maximal inhibition at 100 μM. It reduced platelet microvesiculation induced by collagen. PL blocked the activation of JAK2 and STAT3 in collagen-stimulated platelets. This inhibitory effect was significantly reduced in platelets pretreated with a STAT3 inhibitor. Although PL induced ROS production in platelets; quenching ROS using excessive reducing agents: 20 μM GSH and 0.5 mM L-Cysteine, did not block the inhibitory effects. The NADPH oxidase inhibitor Apocynin also had no effect.
  
  
  CONCLUSIONS
  PL inhibited collagen-induced platelet reactivity by targeting the JAK2-STAT3 pathway. We also provide experimental evidence that PL and collagen induce different oxidants that have differential effects on platelets. Studying these differential effects may uncover new mechanisms of regulating platelet functions by oxidants in redox signals.
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.|Tianjin Neurological Institute, General Hospital, Tianjin Medical University, Tianjin, China.
authors.forename: Hengjie
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.
authors.forename: Katie L
authors.initials: KL
authors.lastname: Houck
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.|Tianjin Neurological Institute, General Hospital, Tianjin Medical University, Tianjin, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Tian
authors.affiliation: Division of Infectious Disease, Department of Medicine, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Uddalak
authors.initials: U
authors.lastname: Bharadwaj
authors.affiliation: The Natural Products LINCHPIN Laboratory and Department of Chemistry, Texas A & M University, College Station, Texas, United States of America.
authors.forename: Ken
authors.initials: K
authors.lastname: Hull
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Zhou
authors.forename: Mingzhao
authors.initials: M
authors.lastname: Zhu
authors.affiliation: The Natural Products LINCHPIN Laboratory and Department of Chemistry, Texas A & M University, College Station, Texas, United States of America.
authors.forename: Mingzhao
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Wu
authors.affiliation: Division of Infectious Disease, Department of Medicine, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: David J
authors.initials: DJ
authors.lastname: Tweardy
authors.affiliation: The Natural Products LINCHPIN Laboratory and Department of Chemistry, Texas A & M University, College Station, Texas, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Romo
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.|Division of Hematology, Department of Medicine, University of Washington, School of Medicine, Seattle, Washington, United States of America.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Fu
authors.affiliation: Medicine Division, Imperial College London, London, United Kingdom.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Tianjin Neurological Institute, General Hospital, Tianjin Medical University, Tianjin, China.
authors.forename: Jianning
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Bloodworks Northwest Research Institute, Seattle, Washington, United States of America.|Division of Hematology, Department of Medicine, University of Washington, School of Medicine, Seattle, Washington, United States of America.
authors.forename: Jing-fei
authors.initials: JF
authors.lastname: Dong
mesh_terms: D003094:Collagen / Q000037:antagonists & inhibitors*; D004148:Dioxolanes / Q000494:pharmacology*; D006801:Humans; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors*; D015539:Platelet Activation / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors*; D010881:Piperidones
chemical_list: D003094:Collagen; D004148:Dioxolanes; D053614:Janus Kinase 2; D017382:Reactive Oxygen Species; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C507924:JAK2 protein, human; C498077:piperlongumine; D010881:Piperidones