Lipid peroxidation changes induced by dibutyl phthalate in allergic asthma mice

Background Dibutyl phthalate (DBP) is a common plasticizer in daily life and has been proved to be related to the exacerbation of allergic asthma. Domestic and foreign studies have shown that lipid peroxidation is closely related to the severity of asthma, which can be used as a basis for the diagnosis and treatment of asthma. Whether DBP can induce lipid peroxidation in allergic asthma remains to be further studied.

Objective To investigate whether DBP aggravates allergic asthma by inducing lipid peroxidation in allergic asthma mice.

Methods Eighty male BALB/c mice were randomly divided into 4 groups, namely control group, DBP group (40 mg·kg⁻¹), 50 μg ovalbumin (OVA) group (allergic asthma model group), and DBP+OVA group. The DBP group and the DBP+OVA group were given DBP by gavage from Day 1 to 28, and the OVA group and the DBP+OVA group were sensitized by intraperitoneal injection of OVA, once every 3 d, a total of 5 injections, from Day 9 to 21. From Day 29 to 35, the OVA group and the DBP+OVA group were challenged by OVA atomization. After the exposure, samples of blood and lung were collected. The airway hyperresponsiveness of mice was observed by lung function analysis. The serum contents of immunoglobulin E (IgE), OVA-specific immunoglobulin E (OVA-IgE), and lung homogenate levels of interleukin 4 (IL-4) were detected by enzyme-linked immunosorbent assay (ELISA) to evaluate airway allergic inflammation. The pathological changes of lung tissues were observed after hematoxylin-eosin (HE) staining and collagen fiber (Masson) staining. The contents of reactive oxygen species (ROS), lipid ROS, glutathione peroxidase 4 (GPX4), reduced glutathione (GSH), malondialdehyde (MDA), and 4-hydroxynonenal (4-HNE) in lung homogenates were detected by ELISA to evaluate lipid peroxidation.

Results The results of lung function analysis showed that compared with the control group, the inspiratory resistance (Ri) and expiratory resistance (Re) of the OVA group and the DBP+OVA group were increased, and the lung compliance (Cldyn) was decreased. The DBP + OVA group was more severe, and the difference between the OVA group and the DBP + OVA group was statistically significant (P<0.05 or P<0.01). Compared with the control group, the contents of IgE, OVA-IgE, and IL-4 in the OVA group and the DBP+OVA group were increased (P<0.05 or P<0.01), which indicated more severe allergic airway inflammation. The HE sections of the OVA group and the DBP+OVA group showed inflammatory cell infiltration around the airway, airway wall hyperplasia and thickening, and severe airway deformation, and the presentation of the DBP+OVA group was the most serious. After Masson staining, the OVA group and the DBP+OVA group showed depositions of a large number of collagen fibers, and the blue collagen fibrosis in the DBP+OVA group was even more serious. ROS, lipid ROS, MDA, and 4-HNE levels increased and GSH and GPX4 levels decreased in the OVA and DBP+OVA groups (P<0.05 or P<0.01), with the most severe effect in the DBP+OVA group.

Conclusion DBP may induce lipid peroxidation in mice allergic asthma by producing excessive ROS which may aggravate the allergic asthma in mice.