Article Text

  1. K. Birukov1,
  2. V. Bochkov2,
  3. N. Leitinger2,
  4. J. Garcia1
  1. 1Johns Hopkins University, Baltimore, MD
  2. 2University of Vienna


Increased levels of oxidized phospholipids generated by oxidation of shed cell membranes released into local circulation have been recently detected in acute lung injury and cardiac ischemia. This study characterized signaling pathways and barrier regulation induced in human pulmonary artery endothelial cells (EC) by a bioactive component of cell membrane-derived oxidized phospholipids, oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC). OxPAPC induced time-dependent activation of protein kinase C (PKC), protein kinase A (PKA), Raf/MEK1,2/Erk-1,2 MAP kinase cascade, JNK MAP-kinase, protein tyrosine phosphorylation, and small GTPases Rac and Cdcd42 without noticeable activation of Rho. These effects were specific to oxidized phospholipids, as non-oxidized species (PAPC, PLPC, DMPC) were without effect. OxPAPC caused sustained concentration-dependent increases in EC transendothelial resistance (TER) and alleviated increased permeability elicited by thrombin. This barrier-protective effect was linked to oxygenated, epoxyisoprostane-containing phospholipids, as confirmed by mass-spectrometric analysis of OxPAPC bioactive components. Pharmacological inhibitors of OxPAPC-induced signaling and depletion of small GTPases using siRNA approach showed direct involvement of PKC, PKA, Rac and Cdc42, but not MAP-kinase cascades and Rho GTPase in EC barrier-protective response. In addition, inhibition of PKC and PKA attenuated OxPAPC-induced activation of Rac, suggesting that PKC and PKA are upstream of Rac in OxPAPC-activated signaling cascade. These results demonstrate for the first time barrier-protective properties of cell membrane-derived oxidized phospholipids generated in acute lung or cardiac injury and suggest PKC-, PKA-, Cdc42- and Rac-dependent cytoskeletal mechanisms of the vascular barrier restoration.

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