title: Lipopolysaccharide-induced pulmonary endothelial barrier disruption and lung edema: critical role for bicarbonate stimulation of AC10.
abstract: Bacteria-induced sepsis is a common cause of pulmonary endothelial barrier dysfunction and can progress toward acute respiratory distress syndrome. Elevations in intracellular cAMP tightly regulate pulmonary endothelial barrier integrity; however, cAMP signals are highly compartmentalized: whether cAMP is barrier-protective or -disruptive depends on the compartment (plasma membrane or cytosol, respectively) in which the signal is generated. The mammalian soluble adenylyl cyclase isoform 10 (AC10) is uniquely stimulated by bicarbonate and is expressed in pulmonary microvascular endothelial cells (PMVECs). Elevated extracellular bicarbonate increases cAMP in PMVECs to disrupt the endothelial barrier and increase the filtration coefficient (Kf) in the isolated lung. We tested the hypothesis that sepsis-induced endothelial barrier disruption and increased permeability are dependent on extracellular bicarbonate and activation of AC10. Our findings reveal that LPS-induced endothelial barrier disruption is dependent on extracellular bicarbonate: LPS-induced barrier failure and increased permeability are exacerbated in elevated bicarbonate compared with low extracellular bicarbonate. The AC10 inhibitor KH7 attenuated the bicarbonate-dependent LPS-induced barrier disruption. In the isolated lung, LPS failed to increase Kf in the presence of minimal perfusate bicarbonate. An increase in perfusate bicarbonate to the physiological range (24 mM) revealed the LPS-induced increase in Kf, which was attenuated by KH7. Furthermore, in PMVECs treated with LPS for 6 h, there was a dose-dependent increase in AC10 expression. Thus these findings reveal that LPS-induced pulmonary endothelial barrier failure requires bicarbonate activation of AC10.
authors.affiliation: Department of Physiology and Cell Biology, University South Alabama, Mobile, Alabama;
authors.forename: Jordan
authors.initials: J
authors.lastname: Nickols
authors.affiliation: Department of Pharmacology, University South Alabama, Mobile, Alabama; Center for Lung Biology, University South Alabama, Mobile, Alabama; and.
authors.forename: Boniface
authors.initials: B
authors.lastname: Obiako
authors.affiliation: Department of Physiology and Cell Biology, University South Alabama, Mobile, Alabama;
authors.forename: K C
authors.initials: KC
authors.lastname: Ramila
authors.affiliation: Department of Physiology and Cell Biology, University South Alabama, Mobile, Alabama;
authors.forename: Kevin
authors.initials: K
authors.lastname: Putinta
authors.affiliation: University of Applied Sciences Bingen, Bingen am Rhein, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Schilling
authors.affiliation: Department of Physiology and Cell Biology, University South Alabama, Mobile, Alabama; Center for Lung Biology, University South Alabama, Mobile, Alabama; and ssayner@southalabama.edu.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Sayner
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002199:Capillary Permeability / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D008297:Male; D020033:Protein Isoforms / Q000378:metabolism*; D011654:Pulmonary Edema / Q000139:chemically induced* / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D012128:Respiratory Distress Syndrome / Q000378:metabolism; D018805:Sepsis / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D008070:Lipopolysaccharides; D020033:Protein Isoforms; D000242:Cyclic AMP; D000262:Adenylyl Cyclases
keywords: bicarbonate; compartmentalized cAMP; lipopolysaccharide; lung edema; soluble adenylate cyclase