title: Regulation of angiopoietin-2 secretion from human pulmonary microvascular endothelial cells.
abstract: Sepsis is characterized by dysregulated systemic inflammation and cytokine storm. Angiopoietin-2 (Ang-2) is known to closely correlate with severity of sepsis-related acute lung injury and mortality. The aim of this study was to clarify the mechanisms involved in Ang-2 secretion to better understand the pathophysiology of sepsis.
  
  
  
  The concentration of Ang-2 was assessed in culture medium of pulmonary microvascular endothelial cells in the presence or absence of Gram-positive bacteria cell wall components [lipoteichoic acid (LTA) and peptidoglycan (PGN)] stimulation at different time points ranging from 15 minutes to 24 hours. Constitutive and LTA-PGN-stimulated Ang-2 level changes were also assessed after cells were pretreated with different pathway inhibitors for 1 hour.
  
  
  
  Two distinctive mechanisms of Ang-2 secretion, constitutive and stimulated secretion, were identified. Constitutive secretion resulted in slow but continuous increase in Ang-2 in culture medium over time. It was regulated by 3'5'-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-Ca2+and nitric oxide (NO)-3'5'-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-Ca2+pathways and partially regulated by N-ethyl-maleimide-sensitive factor-Ca2+pathways. LTA-PGN stimulation caused rapid and potent increase followed by gradual decrease of Ang-2. It was partially regulated by both Ral A-phospholipase D and NSF-Ca2+pathways.
  
  
  
  We demonstrated characteristics and involved pathways for two distinctive secretory mechanisms, constitutive and stimulated, of Ang-2 in pulmonary microvascular endothelial cells. Considering the close correlation of Ang-2 with sepsis outcomes, our findings provide a better understanding of an important mechanism associated with sepsis pathophysiology and identify possible therapeutic targets to improve outcomes in the potentially lethal disease.
authors: a The Elmezzi Graduate School of Molecular Medicine , Manhasset , New York , USA.|b Department of Pulmonary and Critical Care Medicine , University of South Alabama , Mobile , Alabama , USA.
authors: Ji Young
authors: JY
authors: Lee
authors: c The Center for Heart and Lung Research , The Feinstein Institute for Medical Research , Manhasset , New York , USA.
authors: Helena M
authors: HM
authors: Linge
authors: c The Center for Heart and Lung Research , The Feinstein Institute for Medical Research , Manhasset , New York , USA.
authors: Kanta
authors: K
authors: Ochani
authors: c The Center for Heart and Lung Research , The Feinstein Institute for Medical Research , Manhasset , New York , USA.
authors: Ke
authors: K
authors: Lin
authors: a The Elmezzi Graduate School of Molecular Medicine , Manhasset , New York , USA.|c The Center for Heart and Lung Research , The Feinstein Institute for Medical Research , Manhasset , New York , USA.|d Hofstra North Shore-LIJ Medical School , Hempstead , New York , USA.
authors: Edmund J
authors: EJ
authors: Miller
mesh_terms: D042702:Angiopoietin-2 / Q000378:metabolism*; D002473:Cell Wall / Q000737:chemistry; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000737:chemistry; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000098:blood supply* / Q000166:cytology; D010457:Peptidoglycan / Q000494:pharmacology; D018805:Sepsis / Q000503:physiopathology; D013682:Teichoic Acids / Q000494:pharmacology
chemical_list: D042702:Angiopoietin-2; D008070:Lipopolysaccharides; D010457:Peptidoglycan; D013682:Teichoic Acids; C009900:lipoteichoic acid
keywords: angiopoietin-2; endothelial cells; exocytosis; pulmonary; secretion