Secretoglobin 1A1 and 1A1A differentially regulate neutrophil reactive oxygen species production, phagocytosis and extracellular trap formation.
Secretoglobin family 1A member 1 (SCGB 1A1) is a small protein mainly secreted by mucosal epithelial cells of the lungs and uterus. SCGB 1A1, also known as club (Clara) cell secretory protein, represents a major constituent of airway surface fluid. The protein has anti-inflammatory properties, and its concentration is reduced in equine recurrent airway obstruction (RAO) and human asthma. RAO is characterized by reversible airway obstruction, bronchoconstriction and neutrophilic inflammation. Direct effects of SCGB 1A1 on neutrophil functions are unknown. We have recently identified that the SCGB1A1 gene is triplicated in equids and gives rise to two distinct proteins. In this study we produced the endogenously expressed forms of SCGBs (SCGB 1A1 and 1A1A) as recombinant proteins, and analyzed their effects on reactive oxygen species production, phagocytosis, chemotaxis and neutrophil extracellular trap (NET) formation ex vivo. We further evaluated whether NETs are present in vivo in control and inflamed lungs. Our data show that SCGB 1A1A but not SCGB 1A1 increase neutrophil oxidative burst and phagocytosis; and that both proteins markedly reduce neutrophil chemotaxis. SCGB 1A1A reduced chemotaxis significantly more than SCGB 1A1. NET formation was significantly reduced in a time- and concentration-dependent manner by SCGB 1A1 and 1A1A. SCGB mRNA in bronchial biopsies, and protein concentration in bronchoalveolar lavage fluid, was lower in horses with RAO. NETs were present in bronchoalveolar lavage fluid from horses with exacerbated RAO, but not in fluid from horses with RAO in remission or in challenged healthy horses. These findings indicate that SCGB 1A1 and 1A1A have overlapping and diverging functions. Considering disparities in the relative abundance of SCGB 1A1 and 1A1A in airway secretions of animals with RAO suggests that these functional differences may contribute to the pathogenesis of RAO and other neutrophilic inflammatory lung diseases.
Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Olivier
O
Côté
Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Mary Ellen
ME
Clark
Department of Clinical Studies, University of Guelph, Guelph, Ontario, Canada.
Laurent
L
Viel
Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Geneviève
G
Labbé
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Stephen Y K
SY
Seah
Program in Physiology and Experimental Medicine, Lung Innate Immunity Research Laboratory, Hospital for Sick Children, Toronto, Ontario, Canada.
Meraj A
MA
Khan
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Program in Physiology and Experimental Medicine, Lung Innate Immunity Research Laboratory, Hospital for Sick Children, Toronto, Ontario, Canada.
David N
DN
Douda
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada; Program in Physiology and Experimental Medicine, Lung Innate Immunity Research Laboratory, Hospital for Sick Children, Toronto, Ontario, Canada.
Nades
N
Palaniyar
Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Dorothee
D
Bienzle
D000402:Airway Obstruction / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002633:Chemotaxis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D065206:Extracellular Traps / Q000187:drug effects* / Q000378:metabolism*; D006736:Horses; D006801:Humans; D016209:Interleukin-8 / Q000494:pharmacology; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012008:Recurrence; D016897:Respiratory Burst / Q000187:drug effects; D060765:Secretoglobins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors
D016209:Interleukin-8; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D060765:Secretoglobins