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EFFECTS OF DIESEL EXHAUST PARTICLES ON HUMAN ALVEOLAR MACROPHAGE RESPONSIVENESS TO LIPOPOLYSACCHARIDE
Citation:
Mundandhara, S., M. C. Madden, AND S E. Becker. EFFECTS OF DIESEL EXHAUST PARTICLES ON HUMAN ALVEOLAR MACROPHAGE RESPONSIVENESS TO LIPOPOLYSACCHARIDE. Presented at American Thoracic Society Meeting, Orlando, FL, May 21-26, 2004.
Description:
Effects of diesel exhaust particles on human alveolar macrophage responsiveness to lipopolysaccharide
S. Mundandhara1 , S. Becker2 and M. Madden2, 1UNC Center for Environmental Medicine, Asthma, and Lung Biology, 2US EPA, NHEERL, HSD, Chapel Hill, NC, US
Epidemiological studies have associated exposure to ambient particulate matter (PM) with increased lung infections. Diesel exhaust particles (DEP) compose a significant fraction of PM in some areas. Alveolar macrophages (AM) function in pulmonary host defense mechanisms against infections via activation and release of soluble mediators. This study was desinged to investigate the effects of DEP on human AM functions. AM were exposed in vitro to Standard Reference Material (SRM) 2975 (DEP#1), SRM 1650 (DEP#2), SRM 1975(DEP#3, an organic extract of DEP#1) (SRMs from NIST), or carbon black (CB) for 24 hr. Tumor necrosis factor (TNF ), interleukin 8 (IL8) and prostaglandin E2 (PGE2) were measured in the supernatants by ELISA. At non-cytotoxic doses, DEPs but not CB, produced an increase in TNF and PGE2. Polymyxin B inhibited induced increases in mediators, suggesting the presence of lipopolysaccharide (LPS) like compounds. E5531, a Toll-4 receptor antagonist, inhibits the DEP-induced decreases in PGE2 production. After exposure to DEPs and CB, AM were incubated 24 hr with LPS (1ng/ml). In a dose dependent manner, DEPs #1,2,and 3, but not CB, decreased the ability of LPS to stimulate the production of TNF , IL8 and PGE2, despite COX-2 protein levels being equivalent in LPS and DEPs treated AM. AM were incubated with increasing concentrations of LPS to examine if DEP-induced decreases in mediators were maintained . The data show a maintenance of DEPs-induced decreases in cytokine production at all LPS concentrations, suggesting a noncompetitive inhibition. The data indicate DEPs suppress the ability of AM to produce mediators to LPS. This inhibitory effect appears to be due to organic components rather than carbon core. This suppression could impair lung host defense mechanisms, and play a role in PM-induced increases in morbidity. [This abstract may not represent official EPA policy. Supported by CR829522.]
Epidemiological studies have associated exposure to ambient particulate matter (PM) with increased morbidity including lung infections. Diesel exhaust particles (DEP) account for a significant fraction of PM in some locations. Alveolar macrophages (AM) function in pulmonary host defense mechanisms against infections via activation and release of soluble mediators. This study was desinged to investigate the effects of DEP on human AM functions. AM were exposed in vitro to Standard Reference Material (SRM) 2975 (DEP#1), SRM 1650 (DEP#2), SRM 1975(DEP#3) SRMs from National Institute of Standards andTechnology) or Carbon black (CB) for24hr. Tumor necrosis factor (TNF ), interleukin 8 (IL8) and prostaglandin E2 (PGE2) were measured in the supernatants by ELISA. At non-cytotoxic doses, DEP#1, but not the other DEPs and CB, produced an increase in TNF and PGE2 (eg, 3x increase). Polymyxin B inhibited DEP#1 induced increases in cytokines, suggesting the presence of endotoxin like compounds. The synthetic lipid A agonist E5531, a Toll-4 receptor antagonist, almost completely inhibits the DEP-induced decreases in PGE2 production. Following the exposure to DEPs and CB, AM were incubated 24hr with lipopolysaccharide (LPS 1ng/ml). In a dose dependent manner, DEPs #1,2,and 3, but not CB, decreased the ability of LPS to stimulate the production TNF a, IL8 and PGE2, despite COX-2 protein levels being equivalent in LPS + DEPs treated AM. To examine if DEP-induce decreases in mediators were maintained with increasing agonists, AM were incubated with increasing concentrations of LPS. The data show a maintenance of DEPs-induced decreases in cytokine production at all LPS concentrations, suggesting a noncompetitive inhibition. The data from our study indicate DEPs suppress the ability of AM to produce mediators to LPS. This inhibitory effect appears to be due to organic components rather than carbonaceous core of DEPs. This suppression could impair lung host defense mechanisms, and play a role in PM-induced increases in morbidity.[ This abstract may not represent officail EPA policy. Supported by CR829522].