Macrophages primed by overnight culture demonstrate a marked stimulation of surfactant protein A degradation.
The current study examined whether long-term culture of macrophages affects their metabolism of surfactant components. Compared with freshly isolated resting macrophages in culture for 1 h, macrophages attached to plastic dishes for 24 h showed evidence of conversion to a "primed" state with 1) an altered morphology characterized by a larger size, ruffled membranes, lamellipodia, and a "foamy" appearance after attachment to glass and 2) a fivefold greater respiratory burst in response to phorbol 12-myristate 13-acetate stimulation. On incubation with iodinated surfactant protein A (SP-A), the 24-h alveolar or tissue macrophages showed a 5- or a 23-fold greater increase in SP-A degradation, respectively, than macrophages cultured for 1 h. Conditioned media experiments demonstrated that the elevated rate of SP-A degradation after prolonged culture was not a result of proteases secreted by the macrophages. Incubation of cells with NH4Cl reduced the degradation of SP-A to a similar extent (to 33% of control values) in resting and primed tissue macrophages. On the other hand, length of time of cell culture did not affect macrophage uptake and degradation of [3H]dipalmitoylphosphatidylcholine in mixed unilamellar liposomes. Thus freshly isolated resting tissue and alveolar macrophages can be primed to specifically increase their rate of SP-A degradation. Activation of macrophages associated with lung disease may be important for SP-A metabolism and surfactant function.
Bates
S R
SR
Institute for Environmental Medicine, School of Medicine, University of Pennsylvania, Philadelphia 19104-6068, USA.
Xu
J
J
Dodia
C
C
Fisher
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AB
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D000818:Animals; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D010450:Endopeptidases / Q000378:metabolism; D007700:Kinetics; D008081:Liposomes / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000166:cytology* / Q000502:physiology*; D008297:Male; D011510:Proteolipids / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000502:physiology*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
D017077:Culture Media, Conditioned; D008081:Liposomes; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D017382:Reactive Oxygen Species; D015060:1,2-Dipalmitoylphosphatidylcholine; D010450:Endopeptidases