Kinetics of lysosomal protease activity in human otitis media with effusion

Hydrolytic activity of various lysosomal proteases - elastase, collagenase, and cathepsins B and H - were measured in 125 middle ear effusions from patients with chronic (serous and mucoid) and acute otitis media with effusion (OME). The levels of cathepsin B activity and alpha-2-macroglobulin during the course of clinical therapies (myringotomy and tympanostomy tubing) were analyzed in 10 chronic OME cases where follow-up evaluation was possible. It is found that the level of lysosomal protease activity (elastase, collagenase and cathepsin B) was higher in acute OME than that in chronic OME; the hydrolytic activity of cathepsin B in middle ear effusions could be used as an indicator to reflect the level of lysosomal proteases activity in the middle ear; in chronic OME, inflammatory reaction including lysosomal protease activity of the middle ear mucosa at the time of the first myringotomy appeared to be more active than that at the time of the final myringotomy, but less than that in acute OME; and the proteolytic damage of lysosomal thiol proteases to the middle ear mucosa, which may be related to the chronicity of OME, could be reproduced by both therapeutic myringotomy and tympanostomy.