Airway inflammation induced by LPS exposure in a mouse model of papain-induced asthma

In severe asthma patients, it is difficult to treat because of resistance to corticosteroid therapies. We have previously demonstrated that LPS induced steroid insensitive airway inflammation in mice. In this study, we investigated the effects of LPS exposure on airway inflammation in papain-induced asthma mice model. Papain-sensitized A/J mice were challenged to papain every other day, then were exposed with LPS intranasally twice daily for 3 days. Fluticasone propionate (FP) were administered intranasally at 2 h before each LPS exposure. BALF was collected at 24 h after the last LPS exposure and eosinophils and neutrophils were quantified by FACS analysis. The level of inflammatory cytokine and chemokine in BALF were measured by ELISA, and mRNA expression in lung was measured by RT-qPCR. The number of neutrophils and eosinophils in mice co-exposed to papain and LPS in BALF was significantly increased compared to that in the papain alone-exposed group, especially the number of neutrophils was significantly increased. Chemokine and cytokine levels and mRNA expression were also significantly increased by co-exposure to papain and LPS, especially CXCL1. However, these indicators of airway inflammation were resistant to FP. These profiles provide new insights into steroid insensitive airway inflammation in severe asthma.