TNF-alpha in the regulation of MUC5AC secretion: some aspects of cytokine-induced mucin hypersecretion on the in vitro model.

TNF-alpha has been implicated in the aetiology of otitis media with effusion (OME), where goblet cells proliferate in a modified respiratory epithelium, leading to the accumulation of a mucin-rich effusion in the middle-ear cleft. The MUC5AC mucin gene product has been identified as a component of these effusions. Here we have used the HT29-MTX goblet cell line, which secretes MUC5AC mucin, as a model to study the effect of TNF-alpha on goblet cells. MUC5AC mucin was identified and quantitated with a monoclonal antibody NCL-HGM-45M1. TNF-alpha stimulates MUC5AC mucin secretion in a dose-dependent manner, with 20 ng/ml producing maximal stimulation. Both pre-confluent and confluent cells showed peak stimulation after 7 h, however the pre-confluent cells showed twice the level of mucin hypersecretion. These results suggest that TNF-alpha stimulation of mucin secretion could play an important role in the early acute phase of the development of OME. This hypersecretion of mucin could then lead to the failure of the mucociliary clearance system, resulting in the accumulation of a mucin-rich effusion in the middle ear and the movement to a more chronic phase of the disease.