RESUMEN
Excessive mucus production has been linked to many of the pathologic features of respiratory diseases, including obstruction of the airways, decline in lung function, increased rates of mortality, and increased infections. The mucins, MUC5AC and MUC5B, contribute to the viscoelastic properties of mucus, and are found at elevated levels in the airways of individuals with chronic respiratory diseases. The T helper type 2 cell cytokine, IL-13, is known to regulate MUC5AC expression in goblet cells of the airways, although much less is known about the regulation of MUC5B expression. In a study to further understand the mediators of MUC5AC and MUC5B expression, neuregulin (NRG) 1beta1 was identified as novel regulator of goblet cell formation in primary cultures of human bronchial epithelial cells (HBECs). NRG1beta1 increased expression of MUCAC and MUC5B proteins in a time- and dose-dependent fashion in HBEC cultures. NRG1beta1-induced expression of MU5AC and MUC5B was shown to involve v-erb-b2 erythroblastic leukemia viral oncogene homolog (ErbB) and ErbB3 receptors, but not ErbB4 receptors. Treatment of HBECs with inhibitors of p38 mitogen-activated protein kinase, extracellular signal-regulated kinase1/2, and phosphatidylinositol 3-kinase indicated that these kinases were involved in NRG1beta1-induced MUC5AC and MUC5B expression. Additionally, NRG1beta1 was shown to induce the phosphorylation of the ErbB2 receptor, AKT, and extracellular signal-regulated kinase 1/2. NRG1beta1 protein was found increased in the airways of antigen-challenged mice, together with increases in MUC5AC and MUC5B message. Together, these data indicate that NRG1beta1 is a novel mediator of MUC5AC and MUC5B expression in HBECs, and may represent a novel therapeutic target for mucus hypersecretion in respiratory diseases.