Diesel exhaust particles (DEP) enhance allergic airway inflammation in mice (Takano et al., Am J Respir Crit Care Med 1997; 156: 36–42). DEP consist of carbonaceous nuclei and a vast number of organic chemical compounds. However, it remains to be identified which component(s) from DEP are responsible for the enhancing effects. 9,10-Phenanthraquinone (PQ) is a quinone compound involved in DEP.
Objective To investigate the effects of PQ inoculated intratracheally on allergic airway inflammation related to ovalbumin (OVA) challenge.
Materials and Methods We evaluated effects of PQ on airway inflammation, local expression of cytokine proteins, and allergen-specific immunoglobulin production in mice in the presence or absence of OVA.
Results In the presence of OVA, PQ (2.1 ng/animal) significantly increased the numbers of eosinophils and mononuclear cells in bronchoalveolar lavage fluid as compared with OVA alone. In contrast, the numbers of these cells around the airways were not significantly different between OVA challenge and OVA plus PQ challenge in lung histology. PQ exhibited adjuvant activity for the allergen-specific production of IgG1 and IgE. OVA challenge induced significant increases in the lung expression of IL-4, IL-5, eotaxin, macrophage chemoattractant protein-1, and keratinocyte chemoattractant as compared with vehicle challenge. However, the combination of PQ with OVA did not alter the expression levels of these proteins as compared with OVA alone.
Conclusion These results indicate that PQ can enhance the immunoglobulin production and the infiltration of inflammatory cells into alveolar spaces that are related to OVA, whereas PQ seems to be partially responsible for the DEP toxicity on the allergic airway inflammation.