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Lysosomal thiol proteases in middle ear effusions
Abstract:
Hydrolytic activity of lysosomal cathepsins B and H, and trypsin-like proteases in 115 middle ear effusions (MEEs, 40 serous and 75 mucoid) from chronic otitis media with effusion (OME) patients was measured and compared to that in plasma. The activity of both cathepsins in MEEs was significantly higher than that in plasma (p less than 0.01), and cathepsin B activity in mucoid MEEs was also significantly higher than that in serous MEEs (p less than 0.01). The activity of trypsin-like proteases was very weak in both MEEs and plasma. Profiles of various inhibitors indicated the qualitative difference of proteolytic enzymes between MEEs and plasma. Mucoid MEEs had significantly higher activity of thiol proteases than serous ones (p less than 0.01). Cathepsin B-like lysosomal thiol proteases, derived mainly from macrophages, could become a major proteolytic factor to perpetuate and amplify the inflammatory reaction of chronic OME.
Insights
Lysosomal cathepsins B and H show higher activity in middle ear effusions (MEEs) than plasma. Cathepsin B in mucoid MEEs may drive chronic otitis media inflammation.
Area of Science:
- Biochemistry
- Immunology
- Otolaryngology
Background:
- Chronic otitis media with effusion (OME) involves persistent middle ear inflammation.
- Proteolytic enzymes in middle ear effusions (MEEs) may contribute to OME pathogenesis.
- Lysosomal enzymes, particularly cathepsins, are implicated in inflammatory processes.
Purpose of the Study:
- To compare the hydrolytic activity of cathepsins B and H, and trypsin-like proteases in MEEs and plasma.
- To investigate differences in protease activity between serous and mucoid MEEs.
- To elucidate the role of specific proteases in the inflammatory mechanisms of chronic OME.
Main Methods:
- Measurement of hydrolytic activity of cathepsins B and H, and trypsin-like proteases.
- Analysis of 115 middle ear effusions (MEEs) from chronic OME patients (40 serous, 75 mucoid).
- Comparison of MEE protease activity with plasma samples and assessment using inhibitor profiles.
Main Results:
- Significantly higher cathepsin B and H activity in MEEs compared to plasma (p < 0.01).
- Elevated cathepsin B activity in mucoid MEEs versus serous MEEs (p < 0.01).
- Weak trypsin-like protease activity in both MEEs and plasma; distinct protease profiles between MEEs and plasma.
Conclusions:
- Lysosomal thiol proteases, especially cathepsin B from macrophages, are significantly elevated in MEEs.
- Cathepsin B activity in mucoid MEEs suggests a key role in perpetuating OME inflammation.
- These findings highlight cathepsin B as a potential therapeutic target in chronic OME.