title: Alterations in the bovine bronchoalveolar lavage proteome induced by dexamethasone.
abstract: Stressors such as transportation, weaning and co-mingling increase susceptibility to bacterial pneumonia in cattle and are associated with elevated levels of endogenous glucocorticoids. To determine the effect of glucocorticoids on the proteins expressed in the fluid lining the respiratory tract, bronchoalveolar lavage (BAL) was performed on cattle treated with dexamethasone or saline and proteins were resolved by two-dimensional electrophoresis (2-DE). Significant changes in expression were observed for 9 of the 363 detected spots, and the identities of these proteins were determined by mass spectrometry. Consistent with the initiation of an acute phase response, the expression of alpha-1-acid glycoprotein (orosomucoid) and alpha-1-antitrypsin was increased and alpha-2-HS-glycoprotein (fetuin) was decreased in the BAL fluid of dexamethasone-treated cattle. In addition, dexamethasone induced the expression of two hydrophobic ligand-binding proteins, adipocyte-fatty acid binding protein and odorant binding protein (OBP), as well as the proteins alpha-enolase, cofilin-1 and immunoglobulin J chain. OBP mRNA expression in bronchial biopsies was quantified by real-time RT-PCR and the 6-fold higher levels of expression observed in dexamethasone- versus saline-treated animals correlated with the changes observed in OBP protein level. These findings demonstrate glucocorticoid-dependent changes in the protein composition of the epithelial lining fluid of the respiratory tract, identifying proteins potentially integral to respiratory disease susceptibility.
authors.affiliation: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ont., Canada N1G 2W1. gmitchel@uoguelph.ca
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Mitchell
authors.forename: Mary Ellen
authors.initials: ME
authors.lastname: Clark
authors.forename: Jeff L
authors.initials: JL
authors.lastname: Caswell
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry*; D002417:Cattle / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D020543:Proteome / Q000378:metabolism*; D018035:Receptors, Odorant / Q000235:genetics / Q000378:metabolism; D020545:Respiratory Mucosa / Q000187:drug effects
chemical_list: D020543:Proteome; D018035:Receptors, Odorant; C045648:odorant-binding protein; D003907:Dexamethasone