Regulation of human MUC7 mucin gene expression by cigarette smoke and Pseudomonas aeruginosa lipopolysaccharide in human airway epithelial cells and in MUC7 transgenic mice
MUC7 gene encodes a small-mucin-glycoprotein that functions in lubricating/protecting epithelial surface of the human oral cavity/respiratory tract. To increase the understanding of the regulation of MUC7 expression, this study evaluated the effect of pathogenic factors, cigarette smoke and Pseudomonas aeruginosa LPS, on MUC7 expression in human lung carcinoma cell-line NCI-H292 ( in-vitro ) and MUC7 transgenic mice ( in-vivo ). Expression of human MUC5AC, or mouse Muc5ac and Muc10 (MUC7 ortholog) was assessed for comparative purposes. The in-vitro result showed that with LPS or cigarette smoke extract (CSE) alone, there was a statistically significant increase in the transcription (by quantitative real-time RT-PCR) of MUC7 only with 1%CSE (3.2-fold) and of MUC5AC only with LPS (6-fold). The combination of CSE/LPS resulted in 3.2-4.4-fold and 13-22-fold increase of MUC7 and MUC5AC transcripts, respectively. However, the mucin glycoprotein levels (by ELISA) increased only by 1.3-1.5-fold. In vivo, the smoke/LPS treatment of mice resulted in variable increase of mucins on transcriptional and glycoprotein level (immunohistochemistry) in trachea and lung tissues.