title: In vitro toxicity of particulate matter (PM) collected at different sites in the Netherlands is associated with PM composition, size fraction and oxidative potential--the RAPTES project.
abstract: BACKGROUND
  Ambient particulate matter (PM) exposure is associated with respiratory and cardiovascular morbidity and mortality. To what extent such effects are different for PM obtained from different sources or locations is still unclear. This study investigated the in vitro toxicity of ambient PM collected at different sites in the Netherlands in relation to PM composition and oxidative potential.
  
  
  METHODS
  PM was sampled at eight sites: three traffic sites, an underground train station, as well as a harbor, farm, steelworks, and urban background location. Coarse (2.5-10 μm), fine (< 2.5 μm) and quasi ultrafine PM (qUF; < 0.18 μm) were sampled at each site. Murine macrophages (RAW 264.7 cells) were exposed to increasing concentrations of PM from these sites (6.25-12.5-25-50-100 μg/ml; corresponding to 3.68-58.8 μg/cm2). Following overnight incubation, MTT-reduction activity (a measure of metabolic activity) and the release of pro-inflammatory markers (Tumor Necrosis Factor-alpha, TNF-α; Interleukin-6, IL-6; Macrophage Inflammatory Protein-2, MIP-2) were measured. The oxidative potential and the endotoxin content of each PM sample were determined in a DTT- and LAL-assay respectively. Multiple linear regression was used to assess the relationship between the cellular responses and PM characteristics: concentration, site, size fraction, oxidative potential and endotoxin content.
  
  
  RESULTS
  Most PM samples induced a concentration-dependent decrease in MTT-reduction activity and an increase in pro-inflammatory markers with the exception of the urban background and stop & go traffic samples. Fine and qUF samples of traffic locations, characterized by a high concentration of elemental and organic carbon, induced the highest pro-inflammatory activity. The pro-inflammatory response to coarse samples was associated with the endotoxin level, which was found to increase dramatically during a three-day sample concentration procedure in the laboratory. The underground samples, characterized by a high content of transition metals, showed the largest decrease in MTT-reduction activity. PM size fraction was not related to MTT-reduction activity, whereas there was a statistically significant difference in pro-inflammatory activity between Fine and qUF PM. Furthermore, there was a statistically significant negative association between PM oxidative potential and MTT-reduction activity.
  
  
  CONCLUSIONS
  The response of RAW264.7 cells to ambient PM was markedly different using samples collected at various sites in the Netherlands that differed in their local PM emission sources. Our results are in support of other investigations showing that the chemical composition as well as oxidative potential are determinants of PM induced toxicity in vitro.
authors: Division of Toxicology, Institute for Risk Assessment Sciences, Utrecht University, PO Box 80177, 3508 TD Utrecht, The Netherlands.
authors: Maaike
authors: M
authors: Steenhof
authors: Ilse
authors: I
authors: Gosens
authors: Maciej
authors: M
authors: Strak
authors: Krystal J
authors: KJ
authors: Godri
authors: Gerard
authors: G
authors: Hoek
authors: Flemming R
authors: FR
authors: Cassee
authors: Ian S
authors: IS
authors: Mudway
authors: Frank J
authors: FJ
authors: Kelly
authors: Roy M
authors: RM
authors: Harrison
authors: Erik
authors: E
authors: Lebret
authors: Bert
authors: B
authors: Brunekreef
authors: Nicole A H
authors: NA
authors: Janssen
authors: Raymond H H
authors: RH
authors: Pieters
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D018929:Cell Culture Techniques; D002460:Cell Line; D016207:Cytokines / Q000276:immunology; D003627:Data Interpretation, Statistical; D004731:Endotoxins / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D009426:Netherlands; D010084:Oxidation-Reduction; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D016207:Cytokines; D004731:Endotoxins; D052638:Particulate Matter