title: Toxic effects of brake wear particles on epithelial lung cells in vitro.
abstract: BACKGROUND
  Fine particulate matter originating from traffic correlates with increased morbidity and mortality. An important source of traffic particles is brake wear of cars which contributes up to 20% of the total traffic emissions. The aim of this study was to evaluate potential toxicological effects of human epithelial lung cells exposed to freshly generated brake wear particles.
  
  
  RESULTS
  An exposure box was mounted around a car's braking system. Lung cells cultured at the air-liquid interface were then exposed to particles emitted from two typical braking behaviours ("full stop" and "normal deceleration"). The particle size distribution as well as the brake emission components like metals and carbons was measured on-line, and the particles deposited on grids for transmission electron microscopy were counted. The tight junction arrangement was observed by laser scanning microscopy. Cellular responses were assessed by measurement of lactate dehydrogenase (cytotoxicity), by investigating the production of reactive oxidative species and the release of the pro-inflammatory mediator interleukin-8. The tight junction protein occludin density decreased significantly (p < 0.05) with increasing concentrations of metals on the particles (iron, copper and manganese, which were all strongly correlated with each other). Occludin was also negatively correlated with the intensity of reactive oxidative species. The concentrations of interleukin-8 were significantly correlated with increasing organic carbon concentrations. No correlation was observed between occludin and interleukin-8, nor between reactive oxidative species and interleukin-8.
  
  
  CONCLUSIONS
  These findings suggest that the metals on brake wear particles damage tight junctions with a mechanism involving oxidative stress. Brake wear particles also increase pro-inflammatory responses. However, this might be due to another mechanism than via oxidative stress.
authors.affiliation: Institute for Anatomy, Division of Histology, University of Bern, Bern, Switzerland. rothen@ana.unibe.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Gasser
authors.forename: Michael
authors.initials: M
authors.lastname: Riediker
authors.forename: Loretta
authors.initials: L
authors.lastname: Mueller
authors.forename: Alain
authors.initials: A
authors.lastname: Perrenoud
authors.forename: Fabian
authors.initials: F
authors.lastname: Blank
authors.forename: Peter
authors.initials: P
authors.lastname: Gehr
authors.forename: Barbara
authors.initials: B
authors.lastname: Rothen-Rutishauser