Evaluation of MUC5AC expression and upregulation in airway epithelial cells of horses

Objective-To isolate and culture primary equine airway epithelial cells in vitro and elucidate the major cytokines involved in expression of the gel-forming mucin gene MUC5AC in horses. Sample Population-12 tracheas obtained within 5 hours after euthanasia from horses free from respiratory tract disease. Procedures-Tracheal rings were digested overnight in 0.2% protease, and dissociated airway epithelial cells were grown in a serum-free defined medium at an air-liquid interface until confluence was achieved. Differentiated airway epithelial cells were treated with a panel of recombinant equine cytokines followed by quantitative reverse transcriptase PCR assay for mRNA of equine MUC5AC and the control gene glyceraldehyde 3-phosphate dehydrogenase. Cultures were incubated in the presence of isohelenin, a nuclear factor kappa B-DNA-binding inhibitor, to investigate transcriptional regulation of MUC5AC. Results-Light and electron microscopy revealed a differentiated epithelium with ciliated cells, nonciliated mucous cells, and basal-like cells. Recombinant equine tumor necrosis factor-alpha was the major mediator in the cytokine panel that significantly increased MUC5AC mRNA by a factor of 5 in a dose- and time-dependent manner. This enhancement was attenuated by isohelenin. Conclusions and Clinical Relevance-Data suggested that a nuclear factor kappa B-based transcriptional mechanism is involved in induction of MUC5AC expression by tumor necrosis factor-a. Understanding the molecular mechanism of cytokine-enhanced MUC5AC expression in horses may lead to better treatment options and understanding of the pathogenesis of equine pulmonary diseases. (Am J Vet Res 2010;71:690-696)