title: Reduced mucociliary clearance in old mice is associated with a decrease in Muc5b mucin.
abstract: Respiratory infections are a major cause of morbidity and mortality in the elderly. Previous reports have suggested that mucociliary clearance (MCC) is impaired in older individuals, but the cause is unclear. To unravel the mechanisms responsible for the age-associated decline in MCC, we investigated the MCC system in young (3 mo) and old (2 yr) C57BL/6 mice. We found that old mice had significantly reduced MCC function in both the upper and lower airways compared with young mice. Measurement of bioelectric properties of isolated tracheal and bronchial tissue revealed a significant decrease in Cl(-) secretion, suggesting that the older mice may have a reduced ability to maintain a sufficiently hydrated airway surface for efficient MCC. Ciliary beat frequency was also observed to be reduced in the older animals; however, this reduction was small relative to the reduction in MCC. Interestingly, the level of the major secreted mucin, Muc5b, was found to be reduced in both bronchioalveolar lavage and isolated tracheal tissue. Our previous studies of Muc5b(-/-) mice have demonstrated that Muc5b is essential for normal MCC in the mouse. Furthermore, examination of Muc5b(+/-) and wild-type animals revealed that heterozygous animals, which secrete ∼50% of the wild-type level of Muc5b, also demonstrate a markedly reduced level of MCC, confirming the importance of Muc5b levels to MCC. These results demonstrate that aged mice exhibit a decrease in MCC and suggest that a reduced level of secretion of both Cl(-) and Muc5b may be responsible.
authors.affiliation: Marsico Lung Institute/UNC CF Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and.
authors.forename: Barbara R
authors.initials: BR
authors.lastname: Grubb
authors.affiliation: Marsico Lung Institute/UNC CF Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Livraghi-Butrico
authors.affiliation: Marsico Lung Institute/UNC CF Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and.
authors.forename: Troy D
authors.initials: TD
authors.lastname: Rogers
authors.affiliation: Marsico Lung Institute/UNC CF Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and.
authors.forename: Weining
authors.initials: W
authors.lastname: Yin
authors.affiliation: Marsico Lung Institute/UNC CF Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and.
authors.forename: Brian
authors.initials: B
authors.lastname: Button
authors.affiliation: Marsico Lung Institute/UNC CF Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina ostro@med.unc.edu.
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Ostrowski
mesh_terms: D000375:Aging; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D055257:Mucin-5B / Q000378:metabolism*; D009079:Mucociliary Clearance; D020545:Respiratory Mucosa / Q000378:metabolism*; D014132:Trachea / Q000378:metabolism
chemical_list: D002712:Chlorides; C524579:Muc5b protein, mouse; D055257:Mucin-5B
keywords: aging; mucociliary clearance