Dibutyl phthalate induced oxidative stress does not lead to a significant adjuvant effect on a mouse asthma model
The prevalence of allergic diseases around the world has been increasing dramatically in recent years. Epidemiological and experimental studies have suggested the involvement of phthalate esters (PAEs) in this increase in allergic diseases. It has been previously reported that PAEs may act as adjuvants, thus contributing to an increase of these diseases. In this study we focus on examining whether dibutyl phthalate (DBP) exhibits an adjuvant effect mediated via an oxidative stress mechanism in a murine asthma model. The DBP was applied through a daily gavage exposure route. Mice were immunized with ovalbumin (OVA) to initiate immune responses, and melatonin (MT) was used as an antioxidant. However, we did not see a significant difference in the level of oxidative stress, which suggested that the possible adjuvant effect of DBP is not via an oxidative stress mechanism. Additionally, the level of immunoglobulin E (IgE) in serum, cytokines and inflammatory cells in bronchoalveolar lavage fluid (BALF) showed no significant difference between the OVA positive control group and the DBP and OVA combined exposure group. The significant difference that was observed in the expiratory resistance of airway hyperresponsiveness (AHR) may be attributed to changes in the three dimensional structure of the airway wall and the slight shrinkage of the airway. The administration of MT significantly reversed all these effects. Taken together with our data, these results suggest that DBP has little or no adjuvant effect in a murine mouse model and is not mediated through an oxidative stress mechanism.