Cholesterol Depletion in Cell Membranes of Human Airway Epithelial Cells Suppresses MUC5AC Gene Expression

ABSTRACT

PURPOSE: If cholesterol in the cell membrane is depleted by treating cells with methyl-beta-cyclodextrin (MbetaCD), the activities of transmembrane receptors are altered in a cell-specific and/or receptor-specific manner. The proinflammatory cytokines, IL-1beta is potent inducers of MUC5AC mRNA and protein synthesis in human airway epithelial cells. Cells activated by IL-1beta showed increased phosphorylation of extracellular signal regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK). Thus, we investigated the effects of cholesterol depletion on the expression of MUC5AC in human airway epithelial cells and whether these alterations to MUC5AC expression were related to MAPK activity. MATERIALS AND METHODS: After NCI-H292 cells were pretreated with 1% MbetaCD before adding IL-1beta for 24 hours, MUC5AC mRNA expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and real time-PCR. Cholesterol depletion by MbetaCD was measured by modified microenzymatic fluorescence assay and filipin staining. The phosphorylation of IL-1 receptor, ERK and p38 MAPK, was analyzed by western blot. RESULTS: Cholesterol in the cell membrane was significantly depleted by treatment with MbetaCD on cells. IL-1beta-induced MUC5AC mRNA expression was decreased by MbetaCD and this decrease occurred IL-1-receptor-specifically. Moreover, we have shown that MbetaCD suppressed the activation of ERK1/2 and p38 MAPK in cells activated with IL-1beta. This result suggests that MbetaCD-mediated suppression of IL-1beta-induced MUC5AC mRNA operated via the ERK- and p38 MAPK-dependent pathway. CONCLUSION: Cholesterol depletion in NCI-H292 cell membrane may be considered an anti-hypersecretory method since it effectively inhibits mucus secretion of respiratory epithelial cells.