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Abstract
This study investigated the distribution of nitric oxide (NO) within isolated outer hair cells (OHCs) from the cochlea, its relationship to mitochondria and its modulation of mitochondrial function. Using two fluorescent dyes—4,5-diaminofluorescein diacetate (DAF-2DA), which detects NO, and tetramethyl rhodamine methyl ester (TMRM+), a mitochondrial membrane potential dye—it was found that a relatively greater amount of the DAF fluorescence in OHCs co-localized with mitochondria in comparison to DAF fluorescence in the cytosole. This study also observed reduced mitochondrial membrane potential of OHCs and increased DAF fluorescence following exposure of the cells to noise (120 dB SPL for 4 h) and to an exogenous NO donor, NOC-7 (>350 nm). Antibody label for nitrotyrosine was also increased, indicating NO-related formation of peroxynitrite in both mitochrondria and the cytosol. The results suggest that NO may play an important physiological role in regulating OHC energy status and act as a potential agent in OHC pathology.
| Abbreviations | ||
| OHC | = | Outer hair cell |
| NO | = | Nitric oxide |
| DAF-2DA | = | 4,5-diaminofluorescein diacetate |
| TMRM+ | = | Tetramethyl rhodamine methyl ester |
| NOS | = | Nitric oxide synthase |
| ROS | = | Reactive oxygen species |
| NT | = | Nitrotyrosine; ONOO−, Peroxynitrite |
| AIF | = | Apoptotic induced factor |
| Abbreviations | ||
| OHC | = | Outer hair cell |
| NO | = | Nitric oxide |
| DAF-2DA | = | 4,5-diaminofluorescein diacetate |
| TMRM+ | = | Tetramethyl rhodamine methyl ester |
| NOS | = | Nitric oxide synthase |
| ROS | = | Reactive oxygen species |
| NT | = | Nitrotyrosine; ONOO−, Peroxynitrite |
| AIF | = | Apoptotic induced factor |