Diesel and Biodiesel Exhaust Particle Effects on Rat Alveolar Macrophages with in vitro Exposure

Combustion emissions from diesel engines emit particulate matter which deposits within the lungs. Alveolar macrophages (AMs) encounter the particles and attempt to engulf the particles. Emissions particles from diesel combustion engines have been found to contain diverse biologically active components including metals and polyaromatic hydrocarbons which cause adverse health effects. However little is known about AM response to particles from the incorporation of biodiesel. The objective of this study was to examine the toxicity in Wistar Kyoto rat AM of biodiesel blend (B20) and low sulfur petroleum diesel (PDEP) exhaust particles. Particles were independently suspended in media at a range of 1-500μgmL^-1. Results indicated B20 and PDEP initiated a dose dependent increase of inflammatory signals from AM after exposure. After 24h exposure to B20 and PDEP gene expression of cyclooxygenase-2 (COX-2) and macrophage inflammatory protein 2 (MIP-2) increased. B20 exposure resulted in elevated prostaglandin E₂ (PGE₂) release at lower particle concentrations compared to PDEP. B20 and PDEP demonstrated similar affinity for sequestration of PGE₂ at high concentrations, suggesting detection is not impaired. Our data suggests PGE₂ release from AM is dependent on the chemical composition of the particles. Particle analysis including measurements of metals and ions indicate B20 contains more of select metals than PDEP. Other particle components generally reduced by 20% with 20% incorporation of biodiesel into original diesel. This study shows AM exposure to B20 results in increased production of PGE₂ in vitro relative to diesel.