LPS Exposure in Early Life Protects Against Mucus Hypersecretion in Ovalbumin-Induced Asthma by Down-Regulation of the IL-13 and JAK-STAT6 Pathways

Abstract

Background/aims: Previous studies have shown that lipopolysaccharide (LPS) exposure may have a protective effect on asthma by reducing airway hyper-responsiveness, airway inflammation and serum IgE levels. However, there are few studies investigating the effect of LPS on mucous secretion in asthma. In this study, we evaluate the relationship between LPS pre-treatment in infant mice and airway mucus hypersecretion in an OVA (ovalbumin)-induced asthma model, and further explore the mechanisms behind this effect.

Methods: Mice were pre-treated with LPS by intranasal instillation (i.n.) from the 3rd day of life for 10 consecutive days before the OVA-induced asthma model was established. In order to detect mucus secretion, periodic acid-Schiff (PAS) staining was carried out, and the expression of Muc5ac was detected. The IL-13 levels in Bronchoalveolar lavage fluid (BALF) and lung tissue were also detected. In vitro, the expression of Muc5ac mRNA and protein was quantified in IL-13-stimulated 16HBE cells with or without LPS pre-treatment. In addition, proteins in the JAK2/STAT6 pathway, transcription factors (forkhead box transcription factor A2 (FOXA2), activation protein-1(AP-1), NF-κB), and the levels of reactive oxygen species (ROS) were also measured in vivo and in vitro.

Results: LPS pre-treatment reduced mucus secretion, as demonstrated by decreased PAS staining and muc5ac expression. Further exploration of the underlying mechanisms of this phenomenon revealed that LPS pre-treatment decreased the production of IL-13, IL-13 induced ROS synthesis was reduced, and the JAK2/STAT6 pathway was inhibited. Decreased stat6 increased transcription factor FOXA2, and the relatively increased FOXA2 further decreased the level of Muc5ac and mucous hypersecretion in OVA-induced asthma.

Conclusions: LPS pre-treatment ameliorated mucus hypersecretion in an OVA-induced asthma model by inhibition of IL-13 production and by further inhibiting the JAK2/STAT6 pathway and ROS activity, and up-regulating expression of FOXA2.

Keywords: Asthma; IL-13; JAK-STAT6; Lps; Mucus hypersecretion.