Related Experiment Videos
Lysosomal augmentation during aminoglycoside uptake in cochlear hair cells
E Hashino1, M Shero, R J Salvi
1Center for Hearing and Deafness, State University of New York at Buffalo, 14214, USA. hashino@ascu.buffalo.edu
Abstract:
Aminoglycoside antibiotics, such as kanamycin, have ototoxic side effects, which often result in degeneration of cochlear and vestibular hair cells in the inner ear. Cytotoxic effects of aminoglycosides, however, do not appear immediately after cellular uptake of aminoglycosides. In order to understand the mechanisms responsible for the delayed emergence of aminoglycoside ototoxicity, changes in lysosomal activities in cochlear hair cells were evaluated during a repeated administration of kanamycin by two methods. Electron microscopic localization of acid phosphatase (AcPase) revealed that AcPase started to accumulate in vesicles 27 h after the start of kanamycin administration. In addition, the number and size of AcPase-filled vesicles increased with repeated kanamycin doses. Confocal microscopic localization of the LysoTracker probe, a vital lysosomal marker, showed an increase in the size of lysosomes in hair cells that were treated with kanamycin. The temporal changes in the augmentation of lysosomes paralleled those in intracellular kanamycin levels. These results suggest that the intralysosomal compartments can accumulate extensive amounts of aminoglycosides, which might lead to lysosomal swelling and subsequent rupture.
Insights
Aminoglycoside antibiotics like kanamycin cause delayed inner ear hair cell damage. This study shows kanamycin accumulates in lysosomes, leading to their swelling and potential rupture, explaining the delayed ototoxicity.
Area of Science:
- Ototoxicity research
- Cell biology
- Pharmacology
Background:
- Aminoglycoside antibiotics, including kanamycin, are known to cause ototoxic side effects.
- These effects manifest as degeneration of cochlear and vestibular hair cells in the inner ear.
- The cytotoxic effects of aminoglycosides are not immediate upon cellular uptake, suggesting a delayed mechanism.
Purpose of the Study:
- To investigate the mechanisms behind the delayed emergence of aminoglycoside ototoxicity.
- To evaluate changes in lysosomal activities within cochlear hair cells during repeated kanamycin administration.
Main Methods:
- Electron microscopic localization of acid phosphatase (AcPase) to identify lysosomal enzyme activity.
- Confocal microscopic localization using LysoTracker, a vital lysosomal marker, to assess lysosome size and dynamics.
- Quantification of intracellular kanamycin levels and correlation with lysosomal changes.
Main Results:
- Acid phosphatase (AcPase) accumulation in vesicles was observed 27 hours after kanamycin administration began.
- The number and size of AcPase-filled vesicles increased with repeated kanamycin doses.
- Lysosomes in kanamycin-treated hair cells significantly increased in size, paralleling intracellular kanamycin levels.
Conclusions:
- Intralysosomal accumulation of aminoglycosides appears to be a key factor in delayed ototoxicity.
- The extensive accumulation of kanamycin within lysosomes may lead to lysosomal swelling and subsequent rupture.
- This mechanism provides insight into the delayed cytotoxic effects of aminoglycoside antibiotics on inner ear hair cells.