Fine airborne urban particles (PM_2.5) sequester lung surfactant and amino acids from human lung lavage

Abstract

Kendall M. Fine airborne urban particles (PM2.5) sequester lung surfactant and amino acids from human lung lavage. Am J Physiol Lung Cell Mol Physiol 293: L1053-L1058, 2007. First published July 6, 2007; doi:10.1152/ajplung.00131.2007.-Components of surfactant act as opsonins and enhance phagocytosis of bacteria; whether this process occurs with atmospheric fine particles has not been shown. We have studied the interactions of fine particles (urban PM2.5) and surfactant removed from normal human lungs by lavage, using a surface analysis technique. The aim was to identify which of the chemical components of brochoalveolar lavage (BAL) deposit on the surfaces of urban PM 2.5. Deposition of surfactant components on urban PM2.5 surfaces was reported in previous studies, but molecular identification and relative quantification was not possible using simple data analysis. In this study, we were able to identify adsorbed components by applying an appropriate statistical technique, factor analysis. In this study, the most strongly associated mass fragment on PM2.5 surfaces exposed to BAL (and undetected on both untreated samples and saline controls) was di-palmitoyl-phosphatidylcholine, a component of lung surfactant. Amino acids were also strongly associated with BAL-exposed PM2.5 surfaces and not other sample types. Thirteen mass fragments were identified, diagnostic of the amino acids alanine, arginine, asparagine, aspartic acid, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, serine, and valine. This study provides evidence that lung surfactant and amino acids related to opsonin proteins adsorb to nonbiological particle surfaces exposed to human lung lining fluid. Disruption of normal surfactant function, both physical and immunological, is possible but unproven. Further work on this PM-opsonin interaction is recommended. bronchoalveolar lavage EPIDEMIOLOGICAL STUDIES have shown that exposure to particulate air pollutants damages health (32). The exact mechanisms further underlying these air pollution effects remain unknown, although recent work (29, 39) has shown that cardiovascular system (acutely) and the developing respiratory system (chronic effects; Ref. 11) are most significantly affected. Effects on the cardiovascular system were seen on the day of exposure, indicating immediate short-term effects that were detectable within hours of exposures. It is likely that sensitivity to particles varies across the population with the young, the elderly, and those with preexisting cardio-respiratory disease being most at risk (31). Effects occur at ambient concentrations in industrial countries: These concentrations are low compared with concentrations recorded in earlier periods and with those common, now, in developing countries (8). Epidemiological and toxicological studies have demonstrated associations between specific PM characteristics and increased mortality and morbidity. Implicated characteristics include surface area, metals, acidic components, oxidative stress potent...

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