title: Upregulation of alveolar epithelial active Na+ transport is dependent on beta2-adrenergic receptor signaling.
abstract: Alveolar epithelial beta-adrenergic receptor (betaAR) activation accelerates active Na+ transport in lung epithelial cells in vitro and speeds alveolar edema resolution in human lung tissue and normal and injured animal lungs. Whether these receptors are essential for alveolar fluid clearance (AFC) or if other mechanisms are sufficient to regulate active transport is unknown. In this study, we report that mice with no beta1- or beta2-adrenergic receptors (beta1AR-/-/beta2AR-/-) have reduced distal lung Na,K-ATPase function and diminished basal and amiloride-sensitive AFC. Total lung water content in these animals was not different from wild-type controls, suggesting that betaAR signaling may not be required for alveolar fluid homeostasis in uninjured lungs. Comparison of isoproterenol-sensitive AFC in mice with beta1- but not beta2-adrenergic receptors to beta1AR-/-/beta2AR-/- mice indicates that the beta2AR mediates the bulk of beta-adrenergic-sensitive alveolar active Na+ transport. To test the necessity of betaAR signaling in acute lung injury, beta1AR-/-/beta2AR-/-, beta1AR+/+/beta2AR-/-, and beta1AR+/+/beta2AR+/+ mice were exposed to 100% oxygen for up to 204 hours. beta1AR-/-/beta2AR-/- and beta1AR+/+/beta2AR-/- mice had more lung water and worse survival from this form of acute lung injury than wild-type controls. Adenoviral-mediated rescue of beta2-adrenergic receptor (beta2AR) function into the alveolar epithelium of beta1AR-/-/beta2AR-/- and beta1AR+/+/beta2AR-/- mice normalized distal lung beta2AR function, alveolar epithelial active Na+ transport, and survival from hyperoxia. These findings indicate that betaAR signaling may not be necessary for basal AFC, and that beta2AR is essential for the adaptive physiological response needed to clear excess fluid from the alveolar airspace of normal and injured lungs.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago, Ill, USA.
authors.forename: Gökhan M
authors.initials: GM
authors.lastname: Mutlu
authors.forename: Vidas
authors.initials: V
authors.lastname: Dumasius
authors.forename: James
authors.initials: J
authors.lastname: Burhop
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: McShane
authors.forename: Fan Jing
authors.initials: FJ
authors.lastname: Meng
authors.forename: Lynn
authors.initials: L
authors.lastname: Welch
authors.forename: Andrew
authors.initials: A
authors.lastname: Dumasius
authors.forename: Nima
authors.initials: N
authors.lastname: Mohebahmadi
authors.forename: Gloria
authors.initials: G
authors.lastname: Thakuria
authors.forename: Karen
authors.initials: K
authors.lastname: Hardiman
authors.forename: Sadis
authors.initials: S
authors.lastname: Matalon
authors.forename: Steven
authors.initials: S
authors.lastname: Hollenberg
authors.forename: Phillip
authors.initials: P
authors.lastname: Factor
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D001834:Body Water / Q000378:metabolism; D002302:Cardiac Output; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005838:Genotype; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology*; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015221:Potassium Channels / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000293:injuries / Q000502:physiology* / Q000503:physiopathology; D018342:Receptors, Adrenergic, beta-1 / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D018343:Receptors, Adrenergic, beta-2 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013047:Specific Pathogen-Free Organisms; D013318:Stroke Volume; D014161:Transduction, Genetic
chemical_list: C505032:CFTR protein, human; D015221:Potassium Channels; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D011993:Recombinant Fusion Proteins; D015222:Sodium Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000584:Amiloride; D012964:Sodium; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase