Apolipoprotein E negatively regulates murine allergic airway inflammation via suppressing the activation of NLRP3 inflammasome and oxidative stress

Abstract Apolipoprotein E (ApoE) has been reported as a steroid unresponsive gene and functions as a negative regulator of airway hyperreactivity (AHR) and goblet cell hyperplasia in house dust mite (HDM)-challenged mice. However, the role of ApoE in Ovalbumin (OVA)-induced allergic airway inflammation disease and the underlying mechanism are still unknown. In the present study, murine allergic airway inflammation was induced by inhaled OVA for consecutive 7 days in wild type (WT) and ApoE−/− mice. In the OVA-induced model, the ApoE level in the bronchoalveolar lavage fluid (BALF) and lung tissues was significantly higher than that of control mice. And ApoE deficiency aggravated airway inflammation including leukocytes infiltration, goblet cell hyperplasia and IgE production as compared to those of WT mice after OVA- challenged, suggesting ApoE servers as an endogenous negative regulator of airway inflammation. Furthermore, OVA challenge elevated the activation of NLRP3 inflammasome with higher protein expression of NLRP3, caspase1 and IL-1β, enhanced oxidative stress with higher expression of 8-OHdG, nitrotyrosine and SOD2, increased the expression of mitochondrial fusion/fission markers including Optic Atrophy 1 (OPA1), Mitofusion 2 (Mfn2), dynamin-related protein 1 (DRP1) and Fission 1 (Fis1). However, these OVA-induced changes were augmented in ApoE−/− mice. Collectively, our results demonstrated that the OVA-induced airway inflammation was aggravated in ApoE−/− mice, and suggested that the underlying mechanism may be associated with the augmented activation of NLRP3 inflammasome and oxidative stress in ApoE−/− mice, therefore targeting ApoE pathway might be a novel therapy approach for allergic airway diseases such as asthma.