MiR-146a negatively regulates neutrophil elastase-induced MUC5AC secretion from 16HBE human bronchial epithelial cells.

Mucus hypersecretion is a major manifestation in patients with chronic inflammatory airway diseases, and MUC5AC protein is a major component of airway mucus. Earlier studies have demonstrated that neutrophil elastase (NE), a serine protease, mainly produced by neutrophils, stimulates the production of MUC5AC from airway epithelial cells. The microRNA miR-146a has been linked to inflammatory diseases. However, the role of miR-146a in the NE-induced MUC5AC expression remains unclear. Here, we show that NE exerts a dose- and time-dependent induction of both MUC5AC and miR-146a in human bronchial epithelial cells (16HBE). Ectopic expression of miR-146a in 16HBE cells inhibited the stimulation of MUC5AC by NE, while, conversely, depletion of endogenous miR-146a enhanced the MUC5AC production. Knockdown of intrinsic miR-146a activated both c-Jun N-terminal kinase (JNK) and nuclear factor-kappaB (NF-κB) signaling pathways. Moreover, targeting JNK or NF-κB by specific chemical inhibitors blocked the upregulation of MUC5AC by miR-146a silencing. Taken together, our data highlight a negative feedback role for miR-146a in the control of MUC5AC production from airway epithelial cells stimulated by NE, which may be associated with the inactivation of JNK and NF-κB signaling.