title: Meconium impairs pulmonary surfactant by a combined action of cholesterol and bile acids.
abstract: Mechanisms for meconium-induced inactivation of pulmonary surfactant as part of the meconium aspiration syndrome in newborn infants, to our knowledge, are not clearly understood. Here we have studied the biophysical mechanisms of how meconium affects surface activity of pulmonary surfactant and whether the membrane-perturbing effects of meconium can be mimicked by exposure of surfactant to a mixture of bile acids and cholesterol. Surface activity of pulmonary surfactant complexes purified from animal lungs was analyzed in the absence and in the presence of meconium in standard surface balances and in a captive bubble surfactometer. We have also evaluated accumulation of surfactant at the air-liquid interface by what we believe to be a novel microtiter plate fluorescent assay, and the effect of meconium components on surfactant membrane fluidity using Laurdan fluorescence thermotropic profiles and differential scanning calorimetry thermograms. Rapid interfacial adsorption, low surface tension upon film compression, efficient film replenishment upon expansion, and thermotropic properties of surfactant complexes are all adversely affected by meconium, and, in a similar manner, they are affected by cholesterol/taurocholate mixtures but not by taurocholate alone. We conclude that inhibition of surfactant by meconium can be mimicked by a bile salt-promoted incorporation of excess cholesterol into surfactant complexes. These results highlight the potential pathogenic role of cholesterol-mobilizing agents as a crucial factor resulting in cholesterol induced alterations of structure and dynamics of surfactant membranes and films.
authors.affiliation: Departamento Bioquimica, Facultad Biologia, Universidad Complutense, Madrid, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Lopez-Rodriguez
authors.affiliation: Departamento Bioquimica, Facultad Biologia, Universidad Complutense, Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Echaide
authors.affiliation: Departamento Bioquimica, Facultad Biologia, Universidad Complutense, Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cruz
authors.affiliation: Department of Pediatrics, San Francisco General Hospital, University of California, San Francisco, California.
authors.forename: H William
authors.initials: HW
authors.lastname: Taeusch
authors.affiliation: Departamento Bioquimica, Facultad Biologia, Universidad Complutense, Madrid, Spain. Electronic address: jpg@bbm1.ucm.es.
authors.forename: Jesus
authors.initials: J
authors.lastname: Perez-Gil
mesh_terms: D000327:Adsorption; D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D008470:Meconium / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013499:Surface Properties; D034421:Sus scrofa; D013696:Temperature
chemical_list: D001647:Bile Acids and Salts; D011663:Pulmonary Surfactants; D002784:Cholesterol