Involvement of the p38 MAPK pathway in IL-13-induced mucous cell metaplasia in mouse tracheal epithelial cells.
OBJECTIVE
IL-13 has been shown to play a pivotal role in mucous cell metaplasia, which is an important feature of the pathogenesis of asthma. However, the signalling pathways evoked by IL-13 in airway epithelial cells remain unclear. This study investigated the signalling mechanism of IL-13-induced mucous cell metaplasia in primary cultures of mouse tracheal epithelial cells (mTEC).


METHODS
mTEC were cultured in an air-liquid interface system in the presence or absence of IL-13. Goblet cell hyperplasia was evaluated quantitatively by immunofluorescent staining for MUC5AC, which is a major component of airway mucins. Western blotting was used to assess activation of the signalling molecules, signal transducer and activator of transcription 6 (STAT6), p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) 1/2. MUC5AC gene expression was measured by RT-PCR.


RESULTS
IL-13 induced mucous cell metaplasia for 7-14 days in mTEC. IL-13 phosphorylated STAT6 within 20 min, whereas it induced delayed phosphorylation of p38 MAPK 36-48 h after stimulation. In contrast, ERK1/2 was constantly activated and was not enhanced by IL-13. An inhibitor of p38 MAPK (SB202190) suppressed mucous cell differentiation in a concentration-dependent manner. In STAT6 knockout mice, IL-13 failed to induce mucous cell metaplasia and activate p38 MAPK. Cycloheximide also diminished activation of p38 MAPK and induction of MUC5AC mRNA expression by IL-13.


CONCLUSIONS
The p38 MAPK pathway is involved in IL-13-induced mucous cell metaplasia and MUC5AC mRNA regulation in mTEC. In addition, p38 MAPK phosphorylation may require STAT6-dependent de novo protein synthesis induced by IL-13.
Fujisawa
Tomoyuki
T
Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, Japan. tomo-f@bc4.so-net.ne.jp
Ide
Kyotaro
K
Holtzman
Michael J
MJ
Suda
Takafumi
T
Suzuki
Kenichiro
K
Kuroishi
Shigeki
S
Chida
Kingo
K
Nakamura
Hirotoshi
H
D000818:Animals; D018929:Cell Culture Techniques; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D020397:Goblet Cells / Q000378:metabolism*; D018793:Interleukin-13 / Q000502:physiology*; D008297:Male; D008679:Metaplasia / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D055271:Mucin 5AC; D009077:Mucins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D050800:STAT6 Transcription Factor / Q000378:metabolism; D014132:Trachea / Q000378:metabolism* / Q000473:pathology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D018793:Interleukin-13; C524679:Muc5ac protein, mouse; D055271:Mucin 5AC; D009077:Mucins; D012333:RNA, Messenger; D050800:STAT6 Transcription Factor; C494100:Stat6 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases