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Up-regulation of MUC5AC mRNA expression in endotoxin-induced otitis media
Abstract:
We investigated the expression levels of MUC5AC in endotoxin-induced otitis media with effusion (OME) in the rat using competitive polymerase chain reaction (PCR) and the morphology of middle ear mucosa using transmission electron microscopy (TEM). Experimental OME in the rat was induced after middle ear instillation of Escherichia coli lipopolysaccharides (LPS). Middle ear mucosa were obtained at 0 h, 12 h, Day 1, Day 3, Day 7 and Day 14 and reverse transcriptase (RT)-PCRs were then performed for the identification of MUC1, MUC2, MUC5AC and submandibular mucin 1 expression, followed by competitive PCRs for MUC5AC and beta2-microglobulin expression. Normal middle ear mucosa revealed no expression of mucin genes, whereas endotoxin upregulated the expression of MUC5AC mRNA between 12 h and Day 7, with maximal expression at Days 1 and 3. Middle ears treated three times with LPS upregulated more MUC5AC mRNA expression, by a factor of approximately 3.5, than those 1 day after one instillation. On TEM, dark granulated cells were observed at Day 3 after endotoxin instillation, but mixed granulated cells were seen on the ears treated three times with LPS. These results suggest that MUC5AC could be one of the major mucin genes in the middle ear mucosa related to otitis media.
Insights
This study shows that endotoxin-induced otitis media with effusion in rats significantly increases MUC5AC mucin gene expression, particularly at Days 1 and 3. This suggests MUC5AC is a key mucin in middle ear inflammation.
Area of Science:
- Otorhinolaryngology
- Molecular Biology
- Pathology
Background:
- Otitis media with effusion (OME) is a common condition, but the molecular mechanisms of middle ear mucosa changes are not fully understood.
- Mucins play a crucial role in mucosal protection and are implicated in various inflammatory conditions.
Purpose of the Study:
- To investigate the expression of MUC5AC, a major mucin, in endotoxin-induced otitis media with effusion (OME) in a rat model.
- To analyze the morphological changes in the middle ear mucosa during OME development.
Main Methods:
- Induction of experimental OME in rats using Escherichia coli lipopolysaccharides (LPS).
- Analysis of mucin gene expression (MUC1, MUC2, MUC5AC, submandibular mucin 1) using reverse transcriptase polymerase chain reaction (RT-PCR).
- Quantitative analysis of MUC5AC mRNA expression via competitive PCR and morphological assessment using transmission electron microscopy (TEM).
Main Results:
- Normal middle ear mucosa showed no mucin gene expression.
- Endotoxin significantly upregulated MUC5AC mRNA expression between 12 hours and Day 7, peaking at Days 1 and 3.
- Repeated LPS instillation led to approximately 3.5-fold higher MUC5AC mRNA expression compared to single instillation.
- TEM revealed distinct cellular changes, including dark granulated cells at Day 3 and mixed granulated cells after multiple LPS treatments.
Conclusions:
- MUC5AC is a major mucin expressed in the middle ear mucosa in response to endotoxin-induced inflammation.
- The expression pattern of MUC5AC suggests its significant role in the pathogenesis of otitis media with effusion.
- Morphological changes observed correlate with the degree of MUC5AC upregulation, indicating its involvement in OME.