Aminoglycosides like gentamicin are antibiotics used for treating serious infections. However, these drugs also kill inner ear sensory hair cells, causing deafness and vestibular deficits. Endocytosis of aminoglycosides into cells is insufficiently rapid to account for their swift appearance in the cytoplasm and observed cytotoxicity. Recently, this laboratory described a rapid, non-endocytotic uptake mechanism for aminoglycoside entry, modulated by TRPV channel regulators. Aminoglycosides can also rapidly enter hair cells through transduction channels and apical endocytosis. The hair cell apex is bathed in endolymph. If the endolymph pathway is critical for aminoglycosides to enter hair cells, how do aminoglycosides enter the endolymph from the vasculature? A TRPV channel, TRPV4, is expressed at the luminal membrane of marginal and endothelial cells in the stria vascularis. TRPV4 could allow aminoglycosides to enter endothelial cells from the blood, and exit marginal cells into endolymph. We will use aortal endothelial cells and kidney tubule cells as models of endothelial uptake and marginal cell clearance of aminoglycosides in the inner ear, and verify that TRPV4 channel is bi-directionally aminoglycoside-permissive. We will determine if marginal cells in strial explants clear aminoglycosides and if this mechanism is TRPV4-dependent. Finally, we will conduct in vivo gentamicin injection experiments and determine if strial endothelial cells uptake gentamicin, allowing the drug to pass through stria vascularis, and if this process is also dependent on TRPV4 channel. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32DC008465-01A1
Application #
7223586
Study Section
Communication Disorders Review Committee (CDRC)
Program Officer
Sklare, Dan
Project Start
2006-08-15
Project End
2008-08-14
Budget Start
2006-08-15
Budget End
2007-08-14
Support Year
1
Fiscal Year
2006
Total Cost
$52,048
Indirect Cost
Name
Oregon Health and Science University
Department
Type
Organized Research Units
DUNS #
096997515
City
Portland
State
OR
Country
United States
Zip Code
97239
Karasawa, Takatoshi; Wang, Qi; Fu, Yi et al. (2008) TRPV4 enhances the cellular uptake of aminoglycoside antibiotics. J Cell Sci 121:2871-9