ObjectiveTo explore the effects of elafin on the regulation of mucin5AC (MUC5AC) in airway epithelial cells.MethodsAfter cultivating epithelial cells in vitro, cells were stimulated by cigarette smoke extract (CSE) and lipopolysaccharide (LPS), the intracellular MUC5AC production and extracellular secretion were assayed by immunofluorescence and ELISA, respectively.ResultsThe level of MUC5AC protein was obviously increased in the LPS stimulation group [(0.785±0.005) μg/ml vs. (0.232±0.004) μg/ml] and the CSE stimulation group [(0.803±0.005) μg/ml vs. (0.255±0.003) μg/ml] than those in the blank control groups (both P<0.01). When pretreated with elafin then stimulated by LPS and CSE, the MUC5AC productions were evidently decreased than those in the single LPS and CSE stimulation groups [(0.363±0.003) μg/ml and (0.406±0.006) μg/ml, bothP<0.01]. As compared with the blank control groups, the MUC5AC protein secretion were significantly decreased after stimulated with single elafin [(0.176±0.002) μg/ml and (0.193±0.004) μg/ml, bothP<0.05].ConclusionElafin may inhibit MUC5AC hypersecretion by blocking MUC5AC production and secretion.