Nitric oxide production from cultured spiral ligament fibrocytes: effects of corticosteroids

Conclusion. This is the first report of nitric oxide (NO) production by cultured spiral ligament (SL) fibrocytes. The data suggest that dexamethasone (Dex) suppresses NO production by SL fibrocytes. Given that SL fibrocytes play a role in cochlear fluid and ion homeostasis, glucocorticoids may suppress cochlear malfunction caused by NO production in SL fibrocytes. Objective. To investigate NO production by cultured SL fibrocytes and regulation of NO production by Dex in mouse secondary cell cultures. Materials and methods. Cultured SL fibrocytes were stimulated with tumor necrosis factor-alpha (TNF-alpha), and NO production was visualized with membrane-permeable 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM diacetate). Inducible nitric oxide synthase (NOSII) messenger RNA (mRNA) was measured by reverse transcription-polymerase chain reaction (RT-PCR). Results. After TNF-alpha stimulation, the fluorescence intensity increased in a time-dependent manner. This increase in fluorescence intensity was suppressed by a nonspecific NOS inhibitor, N-G-nitro L-arginine methyl ester (L-NAME), and Dex. After TNF-alpha stimulation, expression of NOSH mRNA was observed. Expression of NOSII mRNA was inhibited by Dex.