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Comparative Study
. 2001 Sep;16(3):167-72.
doi: 10.3904/kjim.2001.16.3.167.

Mucin secretion in the rat tracheal epithelial cells by epidermal growth factor and Pseudomonas aeruginosa extracts

J S Song  1 , S W Hyun, E Lillihoj, B T Kim
Affiliations
Comparative Study

Mucin secretion in the rat tracheal epithelial cells by epidermal growth factor and Pseudomonas aeruginosa extracts

J S Song et al. Korean J Intern Med. 2001 Sep.

Abstract

Background: Hypersecretion of mucin due to goblet cell hyperplasia is frequently encountered in many chronic airway diseases, such as chronic bronchitis, bronchiectasis, bronchial asthma and cystic fibrosis. Even in normal individuals, viral infection or bacterial pneumonia frequently provoke huge amounts of bronchial secretions which may cause airway obstruction. The production of mucin was regulated by epidermal growth factor (EGF) in vitro. To know whether this EGF system regulates mucin secretion in vivo and Pseudomonas also stimulates the mucin secretion by the same pathway, we studied these relationships in the cultured rat tracheal epithelial cells.

Methods: Rat tracheal epithelial cells were obtained by pronase dissociation from the male Fisher 344 rats. When cells became confluent, they were divided into 6 groups and stimulated with either EGF for 24 hours or Pseudomonas extracts for 12 hours with or without selective EGF-R tyrosine kinase inhibitor tyrphostin AG1478.

Results: We found that both EGF and Pseudomonas extracts phosphorylated the tyrosine residue in the EGF receptor from the rat tracheal epithelial cells and this tyrosine phosphorylation was nearly completely blocked by selective EGF-R tyrosine kinase inhibitor tyrphostin AG1478. The mucin secretion was also stimulated by either EGF or Pseudomonas extracts but more strong secretion of mucin and MUC5AC gene expression in the rat tracheal epithelial cell was done by Pseudomonas extracts.

Conclusion: These data suggest that Pseudomonas secretes the mucin by way of the EGF receptor and MUC5AC gene expression and the inhibitors of EGF receptor tyrosine phosphorylation would be useful to prevent the huge production of mucin due to Pseudomonas aeruginosa lung infection.

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Figures

Figure 1.
Figure 1.
Mucin secretion from the cultured rat tracheal epithelial cells was measured by using the 3H-glucosamine (10 uCi/mL) and sepharose CL-4B gel-filtration column chromatography (0.7×50 cm). The radioactivity of 3H-mucin was counted in the gamma counter. NC; negative control, no serum and no EGF medium (M/D+6F). PC; positive control, 5% serum and EGF (50 ng/mL) containing medium. EGF; EGF (50 ng/mL) in no serum medium. EGF+I; EGF (50 ng/mL) plus tyrphostin AG 1478 (10 uM) in no serum medium. PA; Pseudomonas extracts (1:40 dilution) in no serum medium. PA+I; Pseudomonas extracts (1:40) plus tyrphostin AG 1478 in no serum medium.
Figure 2.
Figure 2.
MUC 5AC mRNA expression in the rat tracheal epithelial cells. Representative RT-PCR showed that both EGF and Pseudomonas stimulated the MUC 5AC mRNA expression and selective tyrosine kinase inhibitor typhorstin AG 1478 blocked the MUC 5AC mRNA expression. As was the case of mucin secretion, Pseudomonas markedly increased the MUC 5AC mRNA expression than from the EGF stimulation.

  1. Lane 1 : negative control, culture medium without EGF and without serum

  2. Lane 2 : positive control, culture medium with EGF and with serum

  3. Lane 3 : culture medium with EGF (25 ng/mL)

  4. Lane 4 : EGF+typhorstin AG 1478

  5. Lane 5 : Pseudomonas extracts (1:40)

  6. Lane 6 : Pseudomonas extracts+typhorstin AG 1478

Figure 3.
Figure 3.
Effects of EGF and Pseudomonas on the rat tracheal epithelial cell EGF-receptor tyrosine phosporylation. EGF and Pseudomonas increased the EGF phosphotyrosine band (180 Kda, arrow) and selective tyrosine kinase inhibitor tyrphostin AG 1478 completely inhibit the tyrosine phosphorylation.

  1. Lane 1 : negative control, culture medium without EGF and without serum

  2. Lane 2 : positive control, culture medium with EGF and with serum

  3. Lane 3 : culture medium with EGF (25 ng/mL)

  4. Lane 4 : EGF + typhorstin AG 1478

  5. Lane 5 : Pseudomonas extracts (1:40)

  6. Lane 6 : Pseudomonas extracts + typhorstin AG 1478

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