Glucocorticoid regulates Keap1-Nrf2 pathway to relieve pulmonary oxidative stress in asthmatic mice

Abstract

Objective To investigate the level of oxidative stress in asthmatic mice and the mechanism of dexamethasone forrelieving oxidative stress. Methods Thirty female C57BL/6 mice were randomly divided into control group, asthma group and dexamethasone group. Following challenges with house dust mites in the latter 2 groups and prior dexamethasone treatment in dexamethasone group, the mice were examined for expression levels of lipid peroxide metabolites malondialdehyde (MDA) and oxidized glutathione (GSSG). Quantitative real-time PCR was used to detect the expression of nuclear factor erythroid 2-related factor 2 (NF-E2) and heme oxygenase 1 (HO-1) in the lung tissues. Immunohistochemistry was used to detect the expression of Nrf2 protein, and Western blotting was performed to detect the changes of Nrf2-Keap1 signaling pathway in the lungs of the mice. Results MDA and GSSG levels were significantly higher in the asthmatic mice than in control group (P < 0.01), and were significantly lowered by dexamethasone treatment in the asthmatic mice (P < 0.05). Compared with the control group, the asthmatic mice showed significantly higher pulmonary expression levels of Nrf2 and HO-1 mRNA (P < 0.05), which were obviously lowered by dexamethasone treatment (P < 0.05). Immunohistochemistry and immunofluorescence assay revealed a significantly higher expression of Nrf2 protein in the lung tissue of asthmatic mice (P < 0.01), which was significantly lowered by dexamethasone treatment (P < 0.01). The asthmatic mice had a significantly lower expression of Keap1 protein in the lungs (P < 0.05), which was obviously increased by dexamethasone treatment (P < 0.05). Conclusion Asthmatic mice have an increased level of oxidative stress. Dexamethasone inhibits the level of pulmonary oxidative stress in asthmatic mice possibly by inhibiting the expression of the downstream antioxidant elements via regulating the Keap1-Nrf2 pathway.

Keywords

• asthma
• dexamethasone
• oxidative stress
• nrf2-keap1 pathway