Cyclophilin A is secreted by a vesicular pathway in vascular smooth muscle cells

Jun Suzuki, Zheng Gen Jin, David F. Meoli, Tetsuya Matoba, Bradford C. Berk

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189 Citations (Scopus)


Reactive oxygen species (ROS) contribute to the pathogenesis of atherosclerosis in part by promoting vascular smooth muscle cell (VSMC) growth. Previously we demonstrated that cyclophilin A (CyPA) is a secreted oxidative stress-induced factor (SOXF) that promotes inflammation, VSMC growth, and endothelial cell apoptosis. However, the mechanisms that regulate CyPA secretion are unknown. In this study, we hypothesized that ROS-induced CyPA secretion from VSMC requires a highly regulated process of vesicle transport, docking, and fusion at the plasma membrane. Conditioned medium and plasma membrane sheets were prepared by exposing VSMC to 1 μmol/L LY83583, which generates intracellular superoxide. A vesicular transport mechanism was confirmed by colocalization at the plasma membrane with vesicle-associated membrane protein (VAMP). CyPA transport to the plasma membrane and secretion were significantly increased by LY83583. Reduction of VAMP-2 expression by small interfering RNA inhibited LY83583-induced CyPA secretion. Pretreatment with 3 μmol/L cytochalasin D, an actin depolymerizing agent, abrogated CyPA secretion. Infection with dominant-negative RhoA and Cdc42 adenovirus inhibited CyPA secretion by 72% and 63%, respectively, whereas dominant-negative Rac1 had a small effect (11%). Pretreatment with the Rho kinase inhibitor Y27632 (3 to 30 μmol/L) and myosin II inhibitor blebbistatin (1 to 10 μmol/L) inhibited CyPA secretion in a dose-dependent manner. Simvastatin (3 to 30 μmol/L) also dose-dependently inhibited LY83583-induced CyPA secretion likely via decreased isoprenylation of small GTPases. Our findings define a novel VSMC vesicular secretory pathway for CyPA that involves actin remodeling and myosin II activation via RhoA-, Cdc42-, and Rho kinase-dependent signaling events.

Original languageEnglish
Pages (from-to)811-817
Number of pages7
JournalCirculation research
Issue number6
Publication statusPublished - Mar 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine


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