Angiopoietin-1 inhibits intrinsic apoptotic signaling and vascular hyperpermeability following hemorrhagic shock.
Studies from our laboratory demonstrated the involvement of intrinsic apoptotic signaling in hyperpermeability following hemorrhagic shock (HS). Angiopoietin 1 (Ang-1), a potent inhibitor of hyperpermeability, was recently shown to inhibit apoptosis. The purpose of our study was to determine the effectiveness of Ang-1 in attenuating HS-induced hyperpermeability and its relationship to apoptotic signaling. HS was induced in rats by withdrawing blood to reduce the mean arterial pressure to 40 mmHg for 1 h, followed by reperfusion. Mesenteric postcapillary venules were examined for changes in hyperpermeability by intravital microscopy. Mitochondrial release of second mitochondrial derived activator of caspases (smac) and cytochrome c were determined by Western blot and ELISA, respectively. Caspase-3 activity was determined by fluorometric assay. Parallel studies were performed in rat lung microvascular endothelial cell (RLMEC) monolayers, utilizing HS serum and the proapoptotic Bcl-2 homologous antagonist/killer [BAK (BH3)] peptide as inducers of hyperpermeability. In rats, Ang-1 (200 ng/ml) attenuated HS-induced hyperpermeability versus the HS group (P < 0.05). Ang-1 prevented HS-induced collapse of mitochondrial transmembrane potential (DeltaPsi(m)), smac and cytochrome c release, and caspase-3 activity (P < 0.05). In RLMEC monolayers, HS serum and BAK (BH3) peptide both induced hyperpermeability that was inhibited by Ang-1 (P < 0.05). Ang-1 attenuated HS and BAK (BH3) peptide-induced collapse of DeltaPsi(m), smac release, cytochrome c release, activation of caspase-3, and vascular hyperpermeability. In vivo, BAK (BH3) induced vascular hyperpermeability that was attenuated by Ang-1 (P < 0.05). These findings suggest that Ang-1's role in maintaining microvascular endothelial barrier integrity involves the intrinsic apoptotic signaling cascade.
Childs
Ed W
EW
Department of Surgery, Texas A&M University System HSC College of Medicine, Scott & White Memorial Hospital, 2401 South 31st Street, Temple, TX 76508, USA. echilds@swmail.sw.org
Tharakan
Binu
B
Byrge
Nickolas
N
Tinsley
John H
JH
Hunter
Felicia A
FA
Smythe
W Roy
WR
D022005:Adherens Junctions / Q000378:metabolism / Q000473:pathology; D042683:Angiopoietin-1 / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D002199:Capillary Permeability; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008643:Mesentery / Q000098:blood supply*; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D008928:Mitochondria / Q000201:enzymology / Q000473:pathology; D024101:Mitochondrial Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012771:Shock, Hemorrhagic / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D013997:Time Factors; D014699:Venules / Q000378:metabolism / Q000473:pathology
D042683:Angiopoietin-1; D051017:Apoptosis Regulatory Proteins; C474007:Bax protein (53-86); D002352:Carrier Proteins; C489013:DIABLO protein, rat; D024101:Mitochondrial Proteins; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D045304:Cytochromes c; C505410:Casp3 protein, rat; D053148:Caspase 3