Monitoring mice health responses caused by intra-tracheal instillation of vehicle exhaust particles by means of BronchoAlveolar Lavage

LEONIDAS NTZIACHRISTOS (1), Tobias Stoeger (2), Theodoros Tzamkiozis (1), Constantinos Sioutas (3), Zissis Samaras (1)

(1) Aristotle University Thessaloniki, (2) Helmholtz Center Munich, (3) University of Southern California

     Abstract Number: 85
     Last modified: October 27, 2009

Abstract
Numerous epidemiological and toxicological studies have demonstrated associations between elevated PM levels and morbidity or mortality. However, there is not a single mechanism which would explain their health effects. In order to identify such mechanisms, one needs to establish a clear link between representative sampling and collection, administration of samples to live specimens and health responses identification methods. This study demonstrates the results of an initial effort to link these different research fields. Particle exhaust samples were collected by a novel sampling device called versatile aerosol concentration enrichment system (VACES). This sampling method retains the original physicochemical characteristics of particles by collecting them in liquid suspensions.
Three different vehicles were employed for testing. One Diesel vehicle was tested in two configurations. First, the vehicle is equipped with a pre-catalyst and a main catalyst (Euro 4). In the second configuration its main oxidation catalyst was replaced by a Diesel Particle Filter (Euro 4 DPF). The second Diesel vehicle was also tested in two alternative configurations. In the first the vehicle is equipped with an oxidation catalyst and is fed with 100% soy-bean biodiesel (Euro 2 Bio). In the second one, the catalyst was removed and the vehicle is tested with regular low-sulfur fuel (Euro 1). Finally, a gasoline Euro 3 car equipped with a three-way has been added in the vehicle sample.
A suite of various driving cycles was run and five liquid suspensions of PM were collected, one for each vehicle configuration. The estimated particulate mass concentration of the liquid samples was approximately 0.1 micro-gram/ micro-liter for the gasoline vehicle and 0.2 micro-gram/ micro-liter for the rest vehicles. For each sample, five mice were intra-tracheal instilled with 50 micro-liter of the sample and five with a dose of 100 micro-liters resulting in 10 mice per sample. Twenty-four hours later, the 60 PM exposed mice were analyzed by bronchoalveolar lavage (BAL) for acute lung inflammation and also for hematological changes, and compared to control mice (5 mice as negative control and 5 as sham control).
This original effort shows that PM samples collected in liquid suspensions can induce a moderate but still significant inflammatory response, depending on vehicle configuration (ranking of inflammatory response: Gasoline Euro 3> Diesel Euro 1 > Diesel Euro 2 Bio > Diesel Euro 4 DPF > Diesel Euro 4). Only the high (100 micro-l) dose of the Gasoline Euro 3 and the Diesel Euro 1 PM resulted in significant (p<0.05) elevated BAL neutrophil counts, raising from 25.3±1.8 ×10E3 cells in sham controls to 73.1±14.0 and 46.9±6.4 ×10E3 cells respectively. Exposure to PM emission samples from Diesel Euro 4 DPF caused 50.2±9.1 ×10E3 BAL PMNs but this change failed to be statistically significant, while levels remained unchanged for the Diesel Euro 4 samples. Interestingly, microscopic investigations of BAL recovered alveolar macrophages revealed visible incorporated carbon black aggregates only for the Diesel Euro 4 samples.
Follow-up steps are the increase in the dose and the concentration of the samples administered.