Particles derived from combustion of heating oil, wood pellets and diesel induce changes in cytokine release and gene transcription in human cell lines

In the lung epithelial cell line, the heating oil particles were more potent to induce release of IL-8 and IL-6 than the diesel and wood pellet particles. In the monocyte cell line, all types of particles induced changes in DNA transcription, increased production of IL-10 and TNFa and reduced production of IL-12p40 and IL-6, heating oil particles apparently being the most potent. Surprisingly, the anti-inflammatory cytokine thrombospondine-1 was up-regulated. However, it is important to emphasise that particles were compared on a mass basis and heating oil combustion emits very low particle mass per energy unit (mg/MJ). However, the heating oil combustion particles contained more PAHs than the other ones. The difference in response between the lung epithelial cells and the monocytes, may be due to different duration of exposure, different kinetics of cytokine expression, or to different roles of the two cells in the immune response. Both macrophages and epithelial cells are important for the inflammatory responses in the lung. Macrophages are also involved in directing the early immune response. The up regulation of IL-10 and down-regulation of IL-12p40 may be crucial in that respect, possibly favouring a Th2 response. The analysis of the DNA transcriptional activity was a preliminary study, and no clear correlation between cytokine analysis and transcription of individual genes was seen.